BioResources, Volume 6, Issue 2
NOTE: Each current issue of BioResources continues to build as new articles are approved.
Wood modification is a generic term describing the application of chemical, physical, or biological methods to alter the properties of the material. The aim is to get better performance from the wood, resulting in improvements in dimensional stability, decay resistance, weathering resistance, etc. It is essential that the modified wood is non-toxic in service and that disposal at the end of life does not result in the generation of any toxic residues. Over the past five years there have been significant developments in wood modification technologies, especially in the commercial sector. This technology is here to stay. PDF
The influence of cross-linking and branching on the number of interconnections between lignin units and the number of end groups (phenolic and non-phenolic) in the lignin molecules is discussed. Branching results in an increased number of end groups. It appears from an evaluation of the literature that p-hydroxyphenylpropane units are phenolic to a larger extent than guaiacylpropane units and that such units in turn are phenolic to a larger extent than syringylpropane units. It is proposed that this is related to the relative oxidation potentials of the lignin units. Guaiacylpropane units C-substituted in the 6-position are phenolic to a large extent. Alternative explanations for this are presented. PDF
Bio-monitoring of air quality in TehranCity was investigated by analyzing 36 pine tree (Pinus eldarica Medw.) barks. The samples were taken from different locations with different degrees of metal pollution (urban, industrial, highway, and control sites). Then, the concentrations of lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), and chromium (Cr) were measured using a flame atomic absorption spectrophotometer. The results of this study showed that the highest and lowest metal concentrations were found in the heavy traffic sites and the control site, respectively. Lead content was found to be the highest in high traffic density areas. The industrial part of the city was characterized by high Zn, Cr, and Ni contents. Variation in heavy metal concentrations between sites was observed and attributed to differences in traffic density and anthropogenic activities. The research also confirms the suitability of Pinus eldarica Medw barks as a suitable bio-indicator of aerial fallout of heavy metals. PDF
Yu, X., Zhang, G., Xie, C., Yu, Y., Cheng, T., and Zhou, Q. (2011). "Equilibrium, kinetic, and thermodynamic studies of hazardous dye neutral red biosorption by spent corncob substrate," BioRes. 6(2), 936-949.
This study focuses on the possible use of spent corncob substrate (SCS), an agricultural waste utilized after the cultivation of white rot fungus Pleurotus ostreatus, to adsorb the hazardous dye Neutral Red (NR) from aqueous solutions. Natural SCS was initially characterized by using a combination of Fourier Transform Infrared Spectrometry (FTIR) and Brunauer-Emmett-Teller (BET) techniques. A batch adsorption study was carried out with varied solution pH, adsorption time, temperature, and initial NR concentration. It was found that NR uptake was favorable over a pH range of 4.0 to 7.0, and the equilibrium adsorption capacity can be reached within about 180 min. The biosorption data were also calculated by the pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacity was 139.1, 140.0, and 143.3 mg g-1 at 20, 30, and 40 °C, respectively. Thermodynamic parameters showed that the adsorption was a spontaneous and endothermic process. The study highlighted a new pathway to develop potential low-cost biosorbent for the removal of dye pollutants from wastewater. PDF
Behaviors of kenaf fibers after long-term immersion under several environmental water conditions were studied. Water absorption tests were carried out by immersing kenaf fibers in distilled water, sea water (pH 8.4), and acidic solution (pH 3) at room temperature for 140 days. The test results indicated significant differences among the kenaf fibers immersed in different environmental conditions, with kenaf fiber immersed in sea water exhibiting the highest level of water absorption, whereas kenaf fiber immersed in acidic solution showed the lowest water absorption values. The tensile strength of the immersed kenaf fibers decreased with increasing immersion time, implying degradation of the fiber. Investigation on the microstructure of immersed kenaf fibers using SEM reveal the degradation of the kenaf fiber with the development of micro-cracks and increased surface roughness of the fiber. PDF
In this study, secondary sludge (SS) from a kraft paper mill was used as a source of biomass to recover protein and investigate its potential use as a wood adhesive. The process of protein recovery involved disruption of the floc structure in alkaline medium to disintegrate and release intercellular contents into the aqueous phase followed by separation of soluble protein. Finally, the soluble protein was subjected to low pH precipitation and the pelletized sludge protein, referred to as recovered sludge protein (RSP) was tested for crude protein, moisture, and other contents. A significant process yield of 90% in terms of precipitation of soluble protein from disintegrated sludge was estimated through calorimetric studies, whereas an overall material balance confirmed a RSP yield of up to 23% based on total suspended solids of raw sludge. The RSP containing 30% crude protein was used as a wood adhesive and its adhesion performance was compared with soy protein isolate (SPI) and phenol formaldehyde (PF) resin. The testing of plywood lap joints has shown up to 41% shear strength level of RSP adhesive compared to PF. This work demonstrates the technical feasibility and potential of SS as a biomass resource to develop eco-friendly adhesives for wood composite applications. PDF
García, J. C., Zamudio, M. A. M., Pérez, A., Feria, M. J., Gomide, J. L., Colodette, J. L., and López, F. (2011). "Soda-AQ pulping of Paulownia wood after hydrolysis treatment," BioRes. 6(2), 971-986.
A trihybrid clone of Paulownia fortunei x tormentosa x elongata was used for pulp and paper production using the soda-anthraquinone (AQ) process, comparing the results with those from Paulownia fortunei. An autohydrolysis process had been previously carried out on this raw material. A composite central experimental design and a multiple regression were used for modeling and optimizing the process. A valuable liquid phase could be obtained from the autohydrolysis process of Paulownia, trying to minimize cellulose degradation for pulp and paper production. A compromise to maximize the glucan and minimize the xylan contents in the postautohydrolysis solid phase could be achieved at 187.5ºC and 15 minutes. A suitable cellulosic pulp with kappa number ranging from 12.2 to 69.2 and ISO brightness from 18.2 to 30.6% presented better results than those from other studies. Regarding handsheets physical properties (tensile index 37.3 N·m/g ) and viscosity (848 cm3/g), significant improvements could be obtained when compared with previous results of a similar process using Paulownia fortunei or Paulownia elongata. PDF
The purpose of this study was to identify the wood species of the marine and filling piles obtained from the ancient Byzantine port of Eleutherius/ Theodosius, Istanbul, Turkey. Anatomical descriptions and identifications of 12 marine and 4 filling piles were performed by microscopic evaluations. In the study, Castanea sativa Mill., Quercus ithaburensis Decne., Quercus pontica C. Koch., and Cupressus sempervirens L. species were identified. No precise identifications were completed for only six samples at the species level; however, those samples showed significant similarity to Quercus spp. and Fagus spp. It was concluded that the economically viable supply of wood was more appropriate than obtaining it from nearby regions. The people living in ancient times had solid knowledge and experience on the utilization of wood species. PDF
Lal, M., Dutt, D., Tyagi, C. H., Kaur, H., and Kumar, A. (2011). "Bio-conventional bleaching of kraft-AQ pulp of A. cadamba by crude xylanases from Coprinellus disseminatus MLK-03 and effect of residual enzyme on effluent load," BioRes. 6(2), 1019-1028.
A new thermo-alkali-tolerant crude xylanase from Coprinellus disseminatus decreased kappa number by 34.38% and improved brightness and viscosity by 1.6 and 6.47% respectively after XE1-stage during prebleaching of Anthocephalus cadamba kraft-AQ pulp. At 2.4% chlorine demand, crude xylanase in a XECEHH (X= enzymatic prebleaching stage, E= extraction stage, C= chlorination stage, H= hypochlorite stage) bleaching sequence improved pulp brightness, tensile index, burst index, and double fold numbers by 3.66%, 4.78%, 6.38%, and 11.11%, respectively with a reduction in viscosity (10.59%) and tear index (10.77%) compared to the control. Combined bleach effluent of the XECEHH sequence mitigated adsorable organic halides (AOX) by 21% and increased chemical oxygen demand (COD), bio-chemical oxygen demand (BOD), and colour by 67.18%, 84.78%, and 97.53%, respectively, compared to the control. Residual enzymes that entered during enzymatic prebleaching stage decreased AOX, COD, BOD, and colour of combined effluent of the XECEHH bleaching sequence progressively and on 6th day, and these were reduced by 23.78%, 0.04%, 15.00%, and 0.61%, respectively, compared to the control. PDF
Variation in the pore structure of eucalyptus fibre during recycling was investigated using low-temperature nitrogen adsorption, atomic force microscopy (AFM), and fractal geometry. The Brunauer- Emmett-Teller (BET) surface area of the fibre fell to 55.1% of the original value after the first cycle, and to 49.0% after the second cycle, ultimately declining to 35.0% after the fourth. The Barret-Joyner- Halenda (BJH) adsorption cumulative pore volume fell to 38.4% of the original by the fourth. After four cycles, the average pore diameter fell to 82% of the original. AFM tests showed that the pore structure in fibre expressed high self-similarity in statistics, and the pore structure in the fibre could be regarded as a fractal. Fractal geometry analysis of the results showed that the fractal dimension of eucalyptus virgin fibre is 2.954. With the number of process cycles increasing, the fractal dimension fell to a minimum of 2.886 after four cycles. The water retention value (WRV) of the fibre was proportional to the fractal dimension and the crystallinity of fibre. PDF
Oil palm empty fruit bunches (EFB)/woven jute fibres (Jw) reinforced epoxy hybrid composites were prepared by hand lay-up technique by keeping the EFB/ woven jute fibre weight ratios constant, i.e. 4:1. By combining oil palm EFB and woven jute fibre, it is possible to take advantage of both fibres while at the same time suppressing their less desirable qualities. These hybrids provide a new type of sandwich structure with a good skin-core adhesion and the potential for their applications as cost-effective sandwich construction. The effect of the layering pattern on the water absorption and thickness swelling of the hybrid composites was studied. It was observed that water diffusion occurred in the composites, depending on the fibre type as well as the layering pattern. EFB fibre composites exhibited maximum water absorption during the whole duration of immersion. The hybridization of oil palm EFB composites with woven jute fibre showed beneficial effects on both the water absorption and thickness swelling by improving fibre/matrix bonding. PDF
Meza, P. R., Felissia, F. E., and Area, M. C. (2011). "Reduction of the recalcitrant COD of high yield pulp mills effluents by AOP. Part 1. Combination of ozone and activated sludge," BioRes. 6(2), 1053-1068.
The aim of this work was to study the effect of ozone, either alone or combined with an activated sludge system, on the reduction of the recalcitrant COD in the effluent of a chemimechanical pulping (NaOH -Na2SO3) integrated mill. Several alternative schemes involving ozonation were tested on liquors and effluents of the pulp mill, and on two kinds of effluents were taken at different points of an activated sludge pilot plant. The largest decrease in COD was 33%, whereas that in aromatic compounds (absorbance at 232.5 nm) was of 73%. The most obvious result of the ozone treatment was effluent decolorization. It was not possible to use ozonation as tertiary treatment, as ozone was necessary to treat the BOD generated, and therefore the effluent must necessarily pass through a biological treatment. With a scheme including an intermediate ozonation between two secondary treatments (post-activated sludge and pre-aeration lagoon), the maximum reductions achieved were of 70% in COD, of 93% in aromatics, and of 96% in color. The limits of COD allowed by the environmental regulations (<250 mg/L) could be achieved with the following stages: 1) primary clarifier, 2) activated sludge system, 3) ozonation, 4) aeration lagoon, and 5) stabilization lagoon. PDF
Dilute sulfuric acid hydrolysis was performed before the isolation of cellulose from Eulaliopsis binata. And then, the effects of dilute acid hydrolysis on composition and structure of the cellulose was studied in detail. The results indicated that hemicellulose was dissolved mostly and that the lignin-hemicellulose-cellulose interactions were also partially disrupted during the dilute acid hydrolysis. Cellulose in Eulaliopsis binata was identified as the cellulose I allomorph with low crystallinity. What’s more, hydrolysis with dilute acid at high temperature increased the degree of cellulose crystallinity and relatively reduced the proportions of less ordered cellulose allomorphs. This was attributed to a preferential degradation of amorphous cellulose and less ordered crystalline forms during the hydrolysis. The cellulose preparation from Eulaliopsis binata after dilute acid hydrolysis had a higher thermal stability than the cellulose preparation from untreated Eulaliopsis binata. PDF
Hydroxyphenyl (H-type) and guaiacyl (G-type) lignin model polymers composed of the β–O–4 structure without g–hydroxymethyl groups were synthesized. The chemical structures of the H- and G-type lignin models were characterized by 1H- and 13C-NMR, as well as MALDI-TOF/MS. The pyrolysis response was analyzed by means of TG-DTG, Py-GC/MS, and a tube furnace technique. 1H-, 13C-NMR, and MALDI-TOF/MS showed that the lignin models were linear polymers. The polymers included the β–O–4 linkage, as in natural lignin. Pyrolytic products from H-type lignin model only possessed p-hydroxyphenyl structure without methoxyl groups, and the pyrolytic products from G-type lignin model only possessed guaiacyl structure with methoxyl groups. Pyrolysis products from H- and G- type lignin models were classified into char, gas, and liquid (bio-oil), and the gaseous products of two model compounds mainly consisted of H2, CO, CH4, CO2, and C2H4. PDF
The aim of this study was to evaluate the potential of a new, straw-based fibre manufacturing technology integrated to bioenergy and biofuels production. The process is based on a novel hot water treatment and subsequent mechanical refining, both of which are performed at a high temperature. Soda process, ethanol production, and chemical defibration based on hot water treatment and subsequent alkaline peroxide bleaching were selected as references. The idea is to utilise the fibre fraction for packaging and the dissolved solids and the formed fines for energy. The investment costs of this process are significantly lower than those of a soda process. Additionally, a chemicals recovery process is unnecessary. Furthermore, the process offers an attractive alternative for biogas production. However, the assessment showed that the process could only be economical in some terms. Subsidies for investment would probably be needed to promote the acceptance of this environmentally safe process. PDF
van de Pas, D., Hickson, A., Donaldson, L, Lloyd-Jones, G., Tamminen, T., Fernyhough, A., and Mattinen, M.-L. (2011). "Characterization of fractionated lignins polymerized by fungal laccases," BioRes. 6(2), 1105-1121.
Lignins are important biopolymers that can be converted into value-added materials by enzymatic treatments. However, the heterogeneity of the lignin polymer makes it a challenging material to modify. Thus, chemical fractionation was used to obtain lignins with high homogeneity in order to assess their biotechnological utilization. Commercial Alcell, birch organosolv lignins, and steam-exploded pine and eucalypt lignins were sequentially fractionated by ether, ether/acetone 4:1 (v:v), and acetone. All fractions were structurally characterized prior to treatments with Thielavia arenaria, Trametes hirsuta, and Melanocarpus albomyces laccases. The reactivities of the enzymes towards the lignins were determined by oxygen consumption measurements, and the degree of polymerization was confirmed by size exclusion chromatography. Field emission scanning electron microscopy revealed that the surfaces of the lignin nanoparticles were dispersed in the enzyme treatment, suggesting an increase in hydrophilicity of the surfaces detected as loosened morphology. Hence, it was concluded that enzyme-aided valorization is an attractive means for lignin modification, provided that optimum reaction conditions are employed. PDF
Kenaf bast fiber was chemically modified by using propionic and succinic anhydrides. Five retention times were compared: 30, 60, 120, 180, and 240 minutes at 100°C. Confirmation of anhydride modification was established by the weight percent gain (WPG) and was further confirmed by Fourier Transform Infra-Red (FT-IR) spectroscopy. Based on WPG, succinylated fibers exhibited higher WPG than propionylated fibers. The results of WPG for both succinylated and propionylated fibers showed that 180 minutes was an optimum time for modification, yielding the highest WPG. The thermal stability of modified fibers was characterized with Thermal Gravimetric Analysis (TGA). Succinylated fibers showed better thermal stability than propionylated fibers. Anhydride modification also enhanced the fiber smoothness, as demonstrated by Scanning Electron Microscopy (SEM) analysis. Succinylated fibers showed a much smoother surface as compared to propionylated fibers and untreated fibers. Anhydride modification significantly decreased the contact angle of kenaf bast fibers, thus imparting good adhesion characteristics to the fibers. PDF
Cotton linter pulp was oxidized in the TEMPO-NaBr-NaClO system with ultrasonic treatment, and cellulose nanocrystals having high carboxylate content were produced directly. Results showed that the C6 primary hydroxyl group of cellulose fiber was converted to the carboxylate group, whose amount could be up to 1.66 mmol/g. During the oxidizing reaction, some of the amorphous region in the cellulose fiber was modified and gradually hydrolyzed, but the crystalline region still remained. It was also shown by TEM (Transmission electron microscopy) that the widths of cellulose nanocrystals were approximately 5-10 nm, and the lengths were approximately 100-400 nm. The high carboxylate content cellulose nanocrystals could be produced in one step by this method, yielding a stable and well dispersed aqueous suspension. PDF
Severe shortage of suitable wood for Medium Density Fiberboard (MDF) production makes it necessary to consider using uncommon and non-conventional raw materials such as agricultural residues. In order to demonstrate the suitability and the potential of two agricultural residues (cotton and corn stalks), laboratory MDF boards were produced. Three press temperatures (170, 180 and 190 ºC) were used. Test samples were prepared from the boards after conditioning at 65% RH and 21 ºC, and all tests were performed according to relevant EN standard methods. The results indicated that the MOR and MOE of boards produced from corn stalks were higher than those from cotton stalks, by almost 25%. However significant difference was not observed for internal bonds of boards. Thickness swelling of MDF boards from corn stalks was lower than cotton stalks. Comparing the results obtained with the strength of boards produced from hardwoods showed similarity between corn stalks and wood, but the strength of MDF boards from cotton stalks was lower. However, the results almost satisfied the EN 622-5;1997 requirement. PDF
Vallejos, M. E., Felissia, F. E., Curvelo, A. A. S., Zambon, M. D., Ramos, L., and Area, M. C. (2011). "Chemical and physico-chemical characterization of lignins obtained from ethanol-water fractionation of bagasse," BioRes. 6(2), 1158-1171.
Organosolv lignins can replace petroleum chemicals such as phenol either partially or totally in various applications. Eight lignins, seven of which corresponded to the ethanol-water fractionation of bagasse and the other to a reference lignin (Alcell®) were analyzed with the aim to evaluate their chemical and physicochemical characteristics. The purity of the lignin fractions was determined by high pressure liquid chromatography (HPLC) and by ash content. Fourier Transform-Infrared Spectroscopy (FTIR) techniques and differential UV spectroscopy were applied to identify the chemical groups in the lignin samples. The molecular weight distribution was determined by size exclusion chromatography (HPSEC). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques were used to determine the mass loss due to the high temperature treatment. The lignins studied showed the presence of p-hydroxyphenyl (H unit) and a greater proportion of guaiacyl (G unit) moieties, lower purity, similar or greater amount of phenolic hydroxyl groups, and higher degradation temperatures, than the Alcell® lignin. PDF
Saadat-Nia, M. A., Brancheriau, L., Gallet, P., Enayati, A. A., Pourtahmasi, K., and Honarvar, F. (2011). "Ultrasonic wave parameter changes during propagation through poplar and spruce reaction wood," BioRes. 6(2), 1172-1185.
Ultrasonic tests were performed in the main directions at 300 kHz in poplar and spruce reaction wood and normal wood. The experiments were conducted on 2 x 2 x 10 cm3 specimens selected from the pith to the bark. The same phase velocity values were measured in poplar tension wood and normal wood. In compression wood, the phase velocity was lower in the longitudinal direction and higher in the transverse direction. The group velocity measured in the longitudinal direction in tension wood was greater than in normal wood, but lower values were obtained in compression wood in comparison to those obtained in normal wood. The results showed that wave attenuation cannot be significantly affected by the structural properties of reaction wood. A better wave energy transfer pathway (RMS voltage) was found in poplar and spruce reaction wood than in normal wood. Acoustic radiation in reaction wood of both species was lower than levels obtained in normal wood in all anisotropic directions. The results obtained when comparing reaction wood and normal wood of both species indicated that sound velocity decreased as moisture content increased, but the attenuation coefficients increased slightly. PDF
Cellulose-silica composite fiber samples have been successfully synthesized using cellulose solution, tetraethoxysilane, and NH3•H2O in ethanol/water mixed solvents at room temperature for 24 h. The cellulose solution was previously prepared by the dissolution of microcrystalline cellulose in a solvent mixture of N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl). The effect of the tetraethoxysilane concentration on the product was investigated. The products were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetric analysis (DSC), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), energy-dispersive X-ray spectrum (EDS), and cross polarization magic angle spinning (CP/MAS) solid state 13C-NMR. The morphology of the cellulose-silica composite fiber was investigated by SEM, while their composition was established from EDS measurements combined with the results of FT-IR spectral analysis and XRD patterns. The XRD, FT-IR and EDS results indicated that the obtained product was cellulose-silica composite fiber. The SEM micrographs showed that the silica particles were homogeneously dispersed in the cellulose fiber. The CP/MAS solid state 13C-NMR results indicated that the silica concentration had an influence on the crystallinity of the cellulose. This method is simple for preparation of cellulose-based composites. PDF
This paper deals with the moisture diffusion coefficient of Dahurian Larch (Larix gmelinii Rupr.) by use of the Finite Difference Method (FDM). To obtain moisture distributions the dimensional boards of Dahurian Larch were dried, from which test samples were cut and sliced evenly into 9 pieces in different drying periods, so that moisture distributions at different locations and times across the thickness of Dahurian Larch were obtained with a weighing method. With these experimental data, FDM was used to solve Fick’s one-dimensional unsteady-state diffusion equation, and the moisture diffusion coefficient across the thickness at specified time was obtained. Results indicated that the moisture diffusion coefficient decreased from the surface to the center of the Dahurian Larch wood, and it decreased with decreasing moisture content at constant wood temperature; as the wood temperature increased, the moisture diffusion coefficient increased, and the effect of the wood temperature on the moisture diffusion coefficient was more significant than that of moisture content. Moisture diffusion coefficients were different for the two experiments due to differing diffusivity of the specimens. PDF
This study investigated the influence of heat treatment on the chemical composition and energy properties of maritime pine (Pinus pinaster) and pedunculate oak (Quercus robur). Samples were treated in a new experimental device at 220, 250, or 280 °C for 1 or 5 hours. Chemical and energy analyses were performed using standard methods. Our results clearly demonstrated an increased degradation of the material due to the combined effects of temperature and treatment duration. This mass loss was basically due to degradation of acid-soluble materials. The energy analysis showed that the fixed carbon content and higher heating value increased, for both species, whereas the volatile matter content decreased with increased extent of treatment (cumulated effects of temperature and time). In the range of temperature and duration studied here, the dimensionless energy properties for both species obeyed the same functions of overall mass loss. The relationships obtained allow quantification of the increase in wood energy concentration due to torrefaction. Mass loss is an excellent indicator of treatment extent. Analytical expressions allowing the prediction of energy and chemical properties as a function of overall mass loss, within the range of treatment extents studied here, are provided. PDF
Despite significant progress having been achieved in recent years to improve wood’s durability, additional developments are still necessary to increase its color stability. ZnO and CeO2 nanoparticles were compared to UV absorbers (Tinuvin 477 DW, 292 and 5151) commonly used to stabilize the wood products color. Nanoparticles, with concentrations in the range 1 to 2 wt%, and UV absorbers, using concentrations advised by the manufacturer, were dispersed in a waterborne UV curable polyurethane/polyacrylate resin. Dispersions were carried out with a high speed mixer at 2,500 RPM with micro glass beads or not, depending on the form of the nanoparticles. Nanocomposite coatings were aged with a weather-o-meter (CI 3000+ - Atlas) according ASTM G155. Color variations were measured with a colorimeter (BYK Gardner – Color Guide 45/0) working with the CIE L*a*b* system. The aim of the present study was to assess the effects of inorganic UV absorbers on the stabilization of color under indoor conditions. Results showed that nanoparticles (ZnO, CeO2) absorbed UV light frequencies in a manner similar to common organic molecules. Their efficiency was better at medium durations of light exposure, for which they could achieve the action of organic absorbers. Finally, the simultaneous use of both absorbers seems to create a protective synergy when degradation is due to UV energy alone. PDF
The peroxide bleaching of high yield pulps from wood with Mg(OH)2 has been developing recently in the pulp and paper industry. However, there is still a lack of data on the application of Mg(OH)2 in peroxide bleaching of non-wood fibres. In this work, our purpose was to study the effect of Mg(OH)2 on peroxide bleaching of wheat straw soda-AQ pulp. The results showed that Mg(OH)2 significantly improved peroxide bleaching efficiency (expressed as the ratio between the brightness gain and the H2O2 consumption) and selectivity (expressed as the ratio between the brightness gain and the viscosity losses) of wheat straw soda-AQ pulp. The brightness, viscosity, and yield of bleached pulp can be significantly enhanced by increasing the replacement ratio of Mg(OH)2. However, at 100% replacement of NaOH with Mg(OH)2, the brightness of bleached pulp was much lower than that of the bleached pulp with NaOH as the sole alkaline source. When 24 to 73% of the NaOH was replaced with Mg(OH)2, the COD of the bleaching filtrate was 11 to 38% lower than that of the NaOH as the sole alkaline source. The lower solubility and alkalinity of Mg(OH)2 , as well as the reduction of Cu ion content in bleached pulp were proposed as accounting for the favorable effect of Mg(OH)2 on peroxide bleaching of wheat straw soda-AQ pulp. PDF
Janardhnan, S., and Sain, M. (2011). "Targeted disruption of hydroxyl chemistry and crystallinity in natural fibers for the isolation of cellulose nano-fibers via enzymatic treatment," BioRes. 6(2), 1242-1250.
Cellulose is the Earth’s most abundant biopolymer. Exploiting its environmentally friendly attributes such as biodegradability, renewability, and high specific strength properties are limited by our inability to isolate them from the secondary cell wall in an economical manner. Intermolecular and intramolecular hydrogen bonding between the cellulose chains is the major force one needs to overcome in order to isolate the cellulose chain in its microfibrillar form. This paper describes how a hydrogen bond-specific enzyme disrupts the crystallinity of the cellulose, bringing about internal defibrillation within the cell wall. Bleached kraft softwood pulp was treated with a fungus (OS1) isolated from elm tree infected with Dutch elm disease. FT-IR spectral analysis indicated a significant reduction in the density of intermolecular and intramolecular hydrogen bonding within the fiber. X-ray spectrometry indicated a reduction in the crystallinity. The isolated nano-cellulose fibers also exhibited better mechanical strength compared to those isolated through conventional methods. The structural disorder created in the crystalline region in the plant cell wall by hydrogen bond-specific enzymes is a key step forward in the isolation of cellulose at its microfibrillar level. PDF
The modified bleaching sequence OPAPPO from short-sequence bleaching OAP and OQP was studied in an effort to achieve higher quality straw pulp (with brightness 84.5% and acceptable viscosity 669 mL/g), which will be appropriate for more situations than straw pulp as presently produced. Though the OP and PO stages are recognized as the key processes used to increase the pulp’s brightness, addition of hydrogen peroxide in acid pretreatment with polyoxometalate (POM) as catalyst (AP stage) was mainly considered in this work. Phosphomolybdic acid was applied to improve straw pulp’s brightness, which was 4.8% ISO higher than the pulp treated without POM. The optimum conditions of the AP stage were: initial pH value 3, temperature 90 °C, H2O2 1.5%, and phosphomolybdic acid 1.0%. Comparison of the sequences OPQPO, OPAPO, and OPAPPO showed that the brightness of pulp bleached by OPAPPO was 2% and 4.7% higher than the same pulp subjected to OPAPO and OPQPO sequences, respectively. Four lignin samples (LOP, LOPA, LOPAP, LOPAPPO) were characterized by 31P NMR spectroscopy. The spectroscopic investigation showed that in LOPA and LOPAP, aliphatic hydroxyls, p-coumaryl units, and guaiacyl phenol moieties were degraded when compared with that in LOP. In LOPAPPO, all these aliphatic hydroxyls and guaiacyl phenols had been destroyed and carboxylic acid functionalities increased. PDF
Lignin can be used as a cheap natural raw material to prepare organic aerogels based upon gelation and supercritical drying in ethanol. The aerogels were prepared from a mixture of the raw materials with lignin (L), resorcinol (R), and formaldehyde (F), followed by a reaction catalyzed by NaOH(C). The effect of the preparation conditions, such as the LRF concentration, the mass ratio of LR to NaOH (LR/C), the mole ratio of LR to F (LR/F), and the gelation temperature, on the gelation ability and the bulk density were studied. The results showed that the density of LRF aerogels increased with increasing reactant concentration and catalyst content. The microstructure of the porous carbon aerogels was investigated by SEM and TEM. The specific surface area and pore size distribution of LRF and RF aerogels were studied by nitrogen adsorption-desorption analysis. The pore width of LRF aerogels ranged from 1 nm to 100 nm. Most of the pores were about 50 nm wide, as is typical for mesoporous materials. PDF
Iqbal, H. M. N., Asgher, M., and Bhatti, H. N. (2011). "Optimization of physical and nutritional factors for synthesis of lignin degrading enzymes by a novel strain of Trametes vericolor," BioRes. 6(2), 1273-1287.
This paper reports the production of ligninase enzymes by a new strain of Trametes versicolor IBL-04 producing a novel pattern of ligninolytic enzymes with highest MnP activities followed by LiP and laccase. In previous studies Trametes versicolor has been reported to produce higher activities of MnP, followed by laccase and LiP. Lignocellulosic substrates including wheat straw, rice straw, banana stalks, corncobs, corn stover, and sugarcane bagasse were used in solid state fermentation (SSF) for the production of ligninases including peroxidase (LiP), manganese peroxidase (MnP), and laccase by Trametes versicolor IBL-04. Maximum production of MnP (998 U/mL), LiP (620 U/mL), and Laccase (49.7 U/mL) was observed after 5 days in the SSF medium containing 5g rice straw (60% w/w moisture) in still culture SSF. Moisture, pH, temperature, inoculums size, additional carbon and nitrogen sources, and surfactants had a significant influence on ligninase synthesis by the fungus. Production of ligninases was substantially enhanced by optimizing SSF production process. Maximum MnP (1775 U/mL), LiP (1663 U/mL), and laccase (99 U/mL) were produced when rice straw (5g) at 66.6 % moisture (w/w) receiving 5ml inoculum was incubated at pH 4.0 and 30oC in the presence of maltose (1% w/w) as carbon source, urea (0.2% w/w) as nitrogen source and 1mM Tween-80 (0.3 ml) as surfactant. PDF
This study presents the utilization of oil palm ash (OPA), a siliceous material from the fiber of oil palm biomass, as a nanofiller for the development of polymer nanocomposites. Polypropylene-based polymer nano-composites reinforced with OPA along with a compatibilizer were prepared by a melt-mixing technique, using a double screw extruder. Variations in the mechanical, morphological, and thermal properties with the filler and compatibilizer loading were studied. The best dispersion occurred in the polymer nano-composites for which the interactions between the polymer matrix and nanosized OPA appeared to be the highest. The particle size and the dispersion of the oil palm ash within the matrix were determined by transmission electron microscopy. The as-synthesized composite materials were typically characterized by tensile and impact test methods. The morphology of the composite materials was studied by scanning electron microscopy. The thermal properties determined by thermogravimetric analysis (TGA) showed enhanced thermal stability of a series of composite materials. Also, melting studies were carried out by differential scanning calorimetry. PDF
The influence of the variables soda (0.5-3.0%), hydrogen peroxide (1.0-6.0%) and time (1-5 h) in the bleaching of soda pulp of empty fruit bunches (EFB) from oil-palm, on the properties of bleached pulps, was studied. Polynomial and neural fuzzy models reproduced the results of brightness, kappa number, and viscosity of the pulps with errors less than 10%. By the simulation of the bleaching of pulp, using the polynomial and neural fuzzy models, it was possible to find optimal values of operating variables, so that the properties of bleached pulps differed only slightly from their best values and yet it was possible to save chemical reagents, energy, and plant size, operating with lower values of operating variables. Thus, operating with 1.13% soda concentration and 2.25% hydrogen peroxide concentration for 3 hours, a pulp with a brightness of 75.1% (8.1% below the maximum) and a viscosity of 740 mL/g (10.4% less than the maximum value), was obtained. PDF
Aydemir, D., Gunduz, G., Altuntaş, E., Ertas, M., Şahin, H. T., and Hakki Alma, M. (2011). "Investigating changes in the chemical consitutents and dimensional stability of heat-treated hornbeam and uludag fir wood," BioRes. 6(2), 1308-1321.
Changes in chemical constituents and some physical properties such as swelling and water absorption of hornbeam (Carpinus betulus L) and uludag fir (Abies bornmulleriana Mattf.) wood were investigated after heat treatment at three different temperatures (170 oC, 190 oC, and 210 oC) for three different durations (4, 8, and 12 hours) by using thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectrometry. The results of TGA show that there was less weight loss in the main degradation region (300-500 oC) for the heat-treated samples as compared to untreated (control) samples. In addition, there was greater weight loss of hornbeam wood than of uludag fir wood in a similar degradation region. This difference could be due to the chemical constituents of softwoods and hardwoods. The results of FTIR spectrometry show that the chemical constituents of the hornbeam wood samples were more affected by heat treatment. All heat-treated samples exhibited lower water absorption and swelling compared to control samples. It was found that the relative decrease in swelling and water absorption for uludag fir was higher than for hornbeam. The maximum decrease in water absorption and swelling was found for both species that were heat-treated at 210 oC for 12 hours. PDF
Kraft lignin, a by-product of the pulp and paper industry, was explored as an adsorbent for six dietary oils and was compared to chitosan, which is widely used in the pharmaceutical market. The dissolution and adsorption efficiency of kraft lignin were tested at an acidic pH corresponding to the stomach, as well as at a basic pH corresponding to the intestine. Results showed that kraft lignin is a powerful adsorbent that can take up dietary oils at up to about 6 times its own weight. Kraft lignin exhibits higher stability and insolubility at the pH of the stomach in comparison to chitosan. The adsorption isotherm of dietary oils fits well with the Freundlich model, and the adsorption kinetics follows a pseudo-second order relationship. PDF
The emergence of novel high-speed inkjet printing technology has been hindered because of claims of poor deinkability of the printed product. Based on our results the decolorization of inkjet inks with the laccase-mediator system is a possible approach to improve the deinkability of inkjet-printed paper. The commercial Myceliophtora thermophila and Trametes versicolor laccases (1 U/mL) and a mediator compound acetosyringone (0.1 mM) decolorized water-soluble textile and inkjet ink dyes by up to 94% and aqueous dye-based inkjet inks by 40 to 98%. M. thermophila laccase decolorized magenta and black inks effectively even at pH 9.0. Acetosyringone was a better mediator compared to ABTS and violuric acid because of its high efficiency and low inherent color. The enzymatic decolorization of inkjet ink was also achieved in deinking experiments with inkjet-printed paper. A treatment with M. thermophila laccase (2 U/g of paper) and acetosyringone (0.02% of paper weight) improved ISO-brightness of the pulp by 5%. PDF
Polymer nanocomposites reinforced with lower volume fractions of nanofiller have recently attracted steadily growing interest due to their peculiar and fascinating properties as well as their unique applications in commercial sectors. In this study, composites based on high density polyethylene and rice husk flour with different loading of nanoclay were fabricated in an internal mixer. The influence of nanofiller at four levels (0, 2, 4, and 6 per hundred compounds (phc)) on the thermal and rheological behavior was studied. The morphology of nanoclay was determined by X-ray diffraction (XRD), and the effect of morphology on the thermal and dynamic mechanical properties were considered. Results indicated that the crystallization temperature, crystallization enthalpy, and crystallinity level increased with increase of nanoclay up to 2 phc and then decreased. Also, the dynamic mechanical behavior of composites was improved by the addition of nanofiller. X-ray diffraction patterns (XRD) revealed that the nanocomposites formed were intercalated. Morphological findings showed that samples containing 2 phc of nanoclay had higher order of intercalation and better dispersion. It seems that the thermal and dynamic mechanical properties of the HDPE/rice husk flour composites were improved by increasing addition of coupling agent. PDF
Basta, A. H., Sefain, M. Z., and El-Rewainy, I. (2011). "Role of some treatments on enhancing the eco-friendly utilization of lignocellulosic wastes in production of cement-fiber bricks," BioRes. 6(2), 1359-1375.
Rice straw (RS) and sawdust (SD) were evaluated for the manufacturing of fiber-cement bricks. The utilization of these bio-wastes will contribute to the reduction of the environmental impact of waste disposal. Pre-treating the fiber wastes, mechanically and/or chemically, was carried out before mixing them with cement and the appropriate amount of water. This approach was done for trials to reduce the tendency of fibers to absorb water, and consequently overcome the side effects of exposing the fiber-bricks to humidity. Different chemical treating agents, based on organic and inorganic materials, were used, e.g., gelatin-hexamine mixture, sodium silicate, and linseed oil. The results obtained show that the investigated organic treatments, especially linseed oil, were effective to reduce the water retention value (WRV) of RS and SD by 60% and 65%, respectively. The treatment provided bricks with compressive strengths of 4.9 MPa and 5.4 MPa, respectively. According to the Engineering Encyclopedia of Building standards, these values are suitable for construction purposes. The bricks manufactured from linseed oil-treated fibers with cement and Nitobond AR may be suited for load-bearing walls, since the compressive strength reached is 7.8 to 8.6 MPa. PDF
Culture conditions of a newly isolated basidiomycetous strain were optimized for the enhanced production of extracellular alkali-thermo-tolerant cellulase-poor xylanase using wheat bran as the sole carbon source under solid state fermentation (SSF). SEM and ITS sequencing confirmed it as Coprinopsis cinerea HK-1 NFCCI-2032. Among various inexpensive agro-residues, wheat bran (carbon source) came up as the most potent enzyme inducer under SSF, and resulted in 54% higher xylanase activity compared to that in submerged fermentation mode. The strain grew well even at 47 ºC. The highest xylanase (695.8 IU/mL) titer was recorded at a substrate:moisture ratio of 1:3 after 7 days of incubation at 37 oC at pH 6.4 along with 0.541 IU/mL of poorly associated cellulase activity. The xylanase exhibited remarkable stability and retained 50% of its activity at pH 8.0 on incubation at 55 ºC for 15 min and 78, 43, and 23% of its activity at temperatures 65, 75 and 85 oC, respectively, demonstrating an approximately 50% alkali-thermo-tolerant nature, which is suitable for biobleaching. PDF
Wang, X., Chang, P. R., Li, Z., Wang, H., Liang, H., Cao, X., and Chen, Y. (2011). "Chitosan-coated cellulose/soy protein membranes with improved physical properties and hemocompatibility," BioRes. 6(2), 1392-1413.
A series of cellulose/soy protein membranes (CSM) was coated with chitosan to improve the mechanical properties, cytocompatibility, and hemocompatibility. The original CSM and chitosan-coated CSM (CH/CSM) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, water contact angle testing, and tensile testing. CH/CSM had a smoother surface microstructure and enhanced mechanical properties as compared to the corresponding CSM. The cytocompatibility and hemocompatibility of CSM and CH/CSM were evaluated by cell culture, MTT assay, in vitro platelet adhesion testing, plasma recalcification time (PRT) measurement, and hemolysis assay. The higher cell adherence and improved cytocompatibility of CH/CSM were mainly ascribed to the coated composition and the altered surface microstructure of CSM. CH/CSM also showed lower platelet adhesion, longer PRT, and a lower hemolysis rate, all resulting from the good hemocompatibility of chitosan and the smoother membrane surface after chitosan coating. Undoubtedly, surface coating with chitosan improved the microstructure, mechanical properties, cytocompatibility, and hemocompatibility, thus widening the possible range of applications for cellulose/soy protein-based biomaterials. PDF
An orthogonal designed experiment was used to investigate the effects of sulfite pretreatment on the components separation and saccharification of wheat straw. The process involved sulfite pretreatment of wheat straw under acidic conditions followed by mechanical size reduction using a high consistency refiner. Reaction temperature, retention time, and charges of sodium bisulfite and sulphuric acid were considered as key factors. The results showed the four factors had impact on saccharification of wheat straw. Raising the temperature, increasing the charge of sodium bisulfite or sulphuric acid, or extending the retention time would improve the dissolution of pentosan, lignin, and saccharification efficiency, while causing further conversion of pentose. The separation of lignin and pentosan from wheat straw was the main cause of improvements in saccharification. With an enzyme loading of 5 FPU cellulase plus 4 CBU β-glucosidase per gram of o.d. substrate, a glucose yield 72.45% was achieved using the substrate pretreated under the conditions of temperature 180 oC, sodium bisulfite charge 3%, sulfuric acid charge 1.48%, and retention time 20 min. PDF
Ma, X., Huang, L., Chen, Y., Cao, S., and Chen, L. (2011). "Preparation of bamboo dissolving pulp for textile production. Part 1. Study on prehydrolysis of green bamboo for producing dissolving pulp," BioRes. 6(2), 1428-1439.
Prehydrolysis was used as the first treatment of bamboo materials for producing high dissolving pulp for textile applications. In this paper, green bamboo (Dendrocalamopsis oldhami)was hydrolyzed in water, and the hydrolysis process was optimized. The morphology and super-molecular structures of the raw material and prehydrolyzed material were studied by SEM and XRD, respectively. Based on the optimum conditions, a study of the kinetics and mechanism showed that pentosan dissolution during the hydrolysis process was a first order reaction. When cooking temperature was 150 oC, 160 oC, 170 oC, and 180 oC, the corresponding reaction rate constants were 0.00411h-1, 0.00495h-1, 0.00730h-1, and 0.00925h-1, respectively. The activation energy was 44.94 kJ/mol based on the Arrhenius empirical equation. SEM results revealed that after the pre-hydrolysis process, the bamboo structure became loose because of hemicellulose dissolution, which created a favorable environment for chemical penetration in the subsequent treatment. Furthermore, the degree of crystallinity was increased from 45.43% to 57.06% during the prehydrolysis. Both the treated and the untreated fibers were assumed to be cellulose I. PDF
The present work deals with the use of multiple-step procedures to obtain valuable sub-products, including nanocellulose, from rice husk. Each sub-product was characterized after every step by analyzing the chemical composition (mainly based on thermogravimetric analysis, Fourier transformed infrared spectra, and X-ray diffraction) and morphology (using visual observations and scanning electron microscopy). The results clearly showed that the selected procedure gave the possibility to separate silica in the first step and then to purify the resultant material, leading to nanocellulose production. All acquired sub-products can be used as additives and fillers in a very wide range of applications. The obtained results will be useful both from technological and academic points of view, mainly for people working in the field of biocomposites. The final material could give added value to a raw biomass material source such as rice husk. PDF
Flammability properties of plasma pretreated cotton fabrics subjected to flame-retardant treatment were studied. Plasma pretreatment, using an atmospheric pressure plasma jet (APPJ), was applied to cotton fabrics to enhance material properties, while retaining inherent advantages of the substrates. An organic phosphorus compound (flame-retardant agent, FR) together with a melamine resin (crosslinking agent, CL) and phosphoric acid (catalyst, PA) were used. Titanium dioxide (TiO2) or nano-TiO2 was used as a co-catalyst for cotton fabrics to improve treatment effectiveness and minimize side effects. Surface morphology of plasma pretreated cotton specimens subjected to flame-retardant treatment showed a roughened and wrinkled fabric surface with high deposition of the finishing agent, caused by an etching effect of plasma and attack of acidic FR. Combustibility of FR-CL-PA-TiO2 and FR-CL-PA-Nano-TiO2 treated fabrics was evaluated by a 45° flammability test. FR-CL-PA-treated specimens showed superior flame-retardancy, which was further improved by plasma pretreatment and addition of metal oxide as a co-catalyst. However, in comparison with the control sample, flame-retardant-treated cotton specimens had lower breaking load and tearing strength, resulting from side effects of the crosslinking agent used, while plasma pretreatment might compensate for the reduction in tensile strength caused by flame-retardant agents. In addition, both plasma pretreatment and metal oxide co-catalyst added in the flame-retardant finishing improved the crosslinking process between FR and cotton fabric, minimizing formation of free formaldehyde and allowing the use of FR in industry. PDF
Zabihzadeh, S. M., Omidvar, A., Marandi, M. A. B., Dastoorian, F., and Mirmehdi, S. M. (2011). "Effect of filler loading on physical and flexural properties of rapeseed stem/PP composites," BioRes. 6(2), 1475-1483.
The objective of the study is to develop a new filler for the production of natural filler thermoplastic composites using the waste rapeseed stalks. The long-term water absorption and thickness swelling behaviors and flexural properties of rapeseed filled polypropylene (PP) composites were investigated. Three different contents of filler were tested: 30, 45, and 60 wt%. Results of long-term hygroscopic tests indicated that by the increase in filler content from 30% to 60%, water diffusion absorption and thickness swelling rate parameter increased. A swelling model developed by Shi and Gardner can be used to quantify the swelling rate. The increasing of filler content reduced the flexural strength of the rapeseed/PP composites significantly. In contrast to the flexural strength, the flexural modulus improved with increasing the filler content. The flexural properties of these composites were decreased after the water uptake, due to the effect of the water molecules. PDF
The compositions of alkaline extractives in bamboo sulfonated chemi-mechanical pulps (SCMP) were analyzed by UV spectroscopy and gas chromatography-mass spectrometry (GC-MS), and their effects on peroxide bleaching were studied. The extractives were composed of short-chain aliphatic compounds, phenols, and fatty acids, of which phenols were the major components. The amount of extractives was increased with the dosage of NaOH, and correspondingly, the bleachability of the extracted pulp was improved. When 3.5% NaOH was used, the brightness gain was 5.83%ISO, and the post-color (PC) number was decreased by 55.7%. The phenol compounds, which might easily generate conjugated structures, may play an important role in bleachability of bamboo SCMP and brightness stability of pulp. PDF
Barrier paper, which is made of bleached absorbent kraft pulp, is a significant layer of decorative laminates, since it controls the see-through of brown color of saturating kraft paper and its opacifying effect usually is achieved by a heavy loading of TiO2. The TiO2, due to its very small particle size, passes between the cellulosic fibers and drains into the white water. To overcome this problem, papermakers try to use various retention aids for improving overall retention of TiO2, but agglomeration of TiO2 causes a decrease in light scattering efficiency of TiO2. During the subsequent saturation operation, the air in the voids is replaced by melamine formaldehyde, which has a refractive index close to that of cellulose. As a result, the sheet becomes translucent and poses 'see through' problem. Keeping this in view, anhydrous magnesium silicate is used as an extender with TiO2 because it effectively increases the overall filler retention, sheet brightness, opacity. The dispersed aqueous slurry of anhydrous magnesium silicate forms fine gel that entraps TiO2 in the wet web and prevents removal of fines and fillers. The addition of 25% TiO2, 7% micronized soapstone powder, 8% anhydrous magnesium silicate, 1% melamine formaldehyde, and 0.1% sodium hexameta-phosphate was found to improve the overall retention by 65.25% and to cut the manufacturing cost by US$ 546.00 per tonne of pulp without affecting the product quality. PDF
Verma, N., Bansal, M. C., and Kumar, V. (2011). "Pea peel waste: A lignocellulosic waste and its utility in cellulase production by Tricoderma reesei under solid state cultivation," BioRes. 1505-1519.
A wide variety of waste bioresources are available on our planet for conversion into bioproducts. In the biological systems, microorganisms are used to utilize waste as an energy source for the synthesis of valuable products such as biomass proteins and enzymes. The large quantities of byproducts generated during the processing of plant food involve an economic and environmental problem due to their high volumes and elimination costs. After isolation of the main constituent, there are abundant remains which represent an inexpensive material that has been undervalued until now. Pea peel waste is one of the undervalued, unused sources of energy that can serve as a potential source for cellulase production. Batch experiments have been performed, using pea peel waste as a carbon source for cellulase production under solid state cultivation by Trichoderma reesei. It was observed that 30 oC temperature and pH 5.0 are the most favorable conditions for cellulase production by T. reesei. FPase activity significantly increases by incorporation of whey as well as wheat starch hydrolysate in the basal salt media used in the production study. The present study describes the utility of pea peel waste, whey as well as wheat starch hydrolysate in cellulase production by T. reesei. The utilization of economically cheap, pea peel waste for cellulase production could be a novel, cost effective, and valuable approach in cellulase production as well as in solid waste management. PDF
The pyrolysis of two types of tobacco residue was carried out at different pyrolysis temperatures between 300 and 600 °C and a residence time of 1 h in a nitrogen atmosphere. The effect of pyrolysis temperature on the product distributions was investigated and the composition of the bio-oils identified. The variation in product distribution depended on both the temperature and the type of tobacco residues. The maximum liquid yields were obtained at 400°C for one sample and at 500°C for the other. The compositions of bio-oils from the pyrolysis of the two samples were found to be very similar. N-containing compounds were found to be the major compounds identified in ether extracts for both samples. PDF
Enzymatic hydrolysis (EH) lignin was modified with formaldehyde. TG-DSC and PY-GC-MS analysis methods were adopted to characterize the differences between EH lignin and the modified lignin. The modified lignin was then mixed with wood sawdust and made into a lignin-based composite under the following conditions: pressure of 2 to 5 MPa, temperature of 175 to 190 oC, and the modified lignin dosage of 20% to 70%. The effects of pressure, temperature, and the modified lignin dosage on the properties of the composites were also evaluated. The pressure of 2 MPa was not enough to make a strong composite, and the composite with low dosage of modified lignin could not resist water, which signifies pressure and the ratio of modified lignin to sawdust are vital factors. Temperatures of 175 oC and 190 oC did not make much difference to change the mechanical properties of the composites. The composites which were made under 3 MPa, 180 oC, and the ratio of 1:1 modified lignin to wood sawdust was of fair quality. The samples made with the modified lignin dosage of 70% under 2MPa at 180 oC for 10min showed a low thickness swelling and low rates of water absorption from humid air and liquid water. Their free formaldehyde contents were also low and met Grade 2 in the national standard of China. PDF
Gunduz, G., Aydemir, D., Onat, S. M., and Akgun, K. (2011). "The effects of tannin and thermal treatment on physical and mechanical properties of laminated chestnut wood composites," BioRes. 6(2), 1543-1555.
The aim of this study was to investigate the effects of tannin and thermal treatment on physical properties such as dimensional stability and moisture content (%), as well as mechanical properties such as bending strength, modulus of elasticity, and compression strength of laminated chestnut wood composites, which are used commonly for shipboard construction in Turkey. The chestnut wood used in boat construction is usually exposed to several treatments in order to achieve better bonding performance and to remove excessive tannins. According to the results obtained, physical properties of laminated chestnut wood without tannin were better compared to samples with tannin. Oven-dry density and air-dry density were found to be higher in samples containing tannins and not exposed to thermal treatment. Moreover, the lowest value of density was observed in samples containing no tannin and exposed to thermal treatment. In terms of mechanical properties, the highest bending strength and modulus of elasticity were obtained from samples containing tannins and not exposed to heat treatment. The lowest values were found in samples without tannin exposed to heat treatment. Regarding compression strength, the maximum and minimum values were found in samples containing tannins and not exposed to heat treatment and samples without tannin and exposed to heat treatment, respectively. PDF
Pine needles, which are abundantly found as underexploited biomass in coniferous forests, are responsible for fire hazards and air pollution. Utilization of pine needles as bed material in lactic acid production with solid state fermentation (SSF) has been studied here. This investigation compared lactic acid production by pure strains of Lactobacilli, (1) L. delbrueckii(NCIM2025); (2) L. pentosus (NCIM 2912); (3) Lactobacillus sp.(NCIM 2734); (4) Lactobacillus sp. (NCIM2084); and a co-culture of the first two strains. The studies required 6 g per flask powdered dry pine needles as bed material, 2 g/L (inoculum), liquid production media based on pure glucose or whey substituted glucose, at 60, 80, and 120 g/L sugar levels, 37 oC, and an initial pH of 6.5. Co-culture attained a maximum lactic acid concentration of 45.10 g/L, followed by that of strain-1, 43.87 g/L and strain-4, 26.15 g/L, in 80 g/L pure glucose media. With 120g/L total sugar in whey-substituted media, the co-culture attained maximum lactic acid production of 44.88 g/L followed by that of strain-1, 43.67 g/L. The present experimental studies indicated better compatibility of pine needle bed with co-culture in solid state fermentation of lactic acid, which may prove to be an eco-friendly technology for utilization of biomass as well as minimizing fires in coniferous forests. PDF
Xiao, L.-P., Sun, Z.-J., Shi, Z.-J., Xu, F., and Sun, R.-C. (2011). "Impact of hot compressed water pretreatment on the structural changes of woody biomass for bioethanol production," BioRes. 6(2), 1576-1598.
As an initial step in an alternative use of woody biomass to produce bioethanol, this work was aimed at investigating the effect of hot compressed water (HCW) pretreatment within the temperature range 100 to 200 °C in a batch-type reactor on the structural changes of Tamarix ramosissima. The untreated and pretreated solid residues were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), solid-state cross polarization/magic angle spinning (CP/MAS), 13C NMR spectroscopy, and thermogravimetric analysis (TGA), as well as chemical methods. The results showed that HCW pretreatment solubilized mainly hemicelluloses and resulted in enriched cellulose and lignin content in the pretreated solids. It was found that the deposition of lignin droplets on the residual surfaces was produced during pretreatment under the hot water conditions above 140 °C. In addition, the removal of hemicelluloses and lignin re-localisation as a result of condensation reactions under the severe pretreatment condition may lead to an increase in cellulose crystallinity and thermal stability of biomass solid residues, thus consequently influencing the downstream digestibility of biomass for sugars and bioethanol production. PDF
Gonzalez, R., Jameel, H., Chang, H.-M., Treasure, T., Pirraglia, A., and Saloni, D. (2011). "Thermo-mechanical pulping as a pretreatment for agricultural biomass as biochemical conversion," BioRes. 6(2), 1599-1614.
The use of thermo-mechanical pulping (TMP), an existing and well known technology in the pulp and paper industry, is proposed as a potential pretreatment pathway of agriculture biomass for monomeric sugar production in preparation for further fermentation into alcohol species. Three agricultural biomass types, corn stover, wheat straw, and sweet sorghum bagasse, were pretreated in a TMP unit under two temperature conditions, 160 ºC and 170 ºC, and hydrolyzed using cellulase at 5, 10, and 20 FPU/g OD biomass. Wheat straw biomass was further pretreated at different conditions including: i) soaking with acetic acid, ii) longer steaming residence time (15 and 30 min), and iii) refined at lower disk gap (0.0508 and 0.1524 mm). Preliminary results showed that carbohydrate conversion increased from 25% to 40% when the TMP temperature was increased from 160 to 170 ºC. Carbohydrate conversion was relatively similar for the three biomasses under the same pretreatment conditions and enzyme loading. Acetic acid soaking and refining at a reduce disk gap increases carbohydrate conversion. Further studies within this technological field to identify optimum process and TMP conditions for pretreatment are suggested. PDF
Changes of the pore structure of recycled fibers and the strength properties of papers produced by old corrugated container (OCC) recycled fibers were studied, after they were subjected to different stock preparation and papermaking processes. In this paper, the effects of beating, sizing, pressing, and drying on fiber properties were investigated, and the porous structure of fibers was analyzed by nitrogen adsorption technique. The results showed that beating, pressing, and other physical processes significantly influenced the fiber properties, whereas the effects of sizing were minor. Significant changes of water retention value (WRV), crystallinity index, and paper strength were observed after those processes. Further, an effort has been made to show relationships between pore structure and macroscopic properties (WRV, crystallinity index) of recycled fibers. PDF
Hrabalova, M., Schwanninger, M., Wimmer, R., Gregorova, A., Zimmermann, T., and Mundigler, N. (2011). "Fibrillation of flax and wheat straw cellulose: Effects on thermal, morphological, and viscoelastic properties of poly(vinylalcohol)/fibre composites," BioRes. 6(2), 1631-1647.
Nano-fibrillated cellulose was produced from flax and wheat straw cellulose pulps by high pressure disintegration. The reinforcing potential of both disintegrated nano-celluloses in a polyvinyl-alcohol matrix was evaluated. Disintegration of wheat straw was significantly more time and energy consuming. Disintegration did not lead to distinct changes in the degree of polymerization; however, the fibre diameter reduction was more than a hundredfold, creating a nano-fibrillated cellulose network, as shown through field-emission-scanning electron microscopy. Composite films were prepared from polyvinyl alcohol and filled with nano-fibrillated celluloses up to 40% mass fractions. Nano-fibrillated flax showed better dispersion in the polyvinyl alcohol matrix, compared to nano-fibrillated wheat straw. Dynamic mechanical analysis of composites revealed that the glass transition and rubbery region increased more strongly with included flax nano-fibrils. Intermolecular interactions between cellulose fibrils and polyvinyl alcohol matrix were shown through differential scanning calorimetry and attenuated total reflection-Fourier transform infrared spectroscopy. The selection of appropriate raw cellulose material for high pressure disintegration was an indispensable factor for the processing of nano-fibrillated cellulose, which is essential for the functional optimization of products. PDF
The aim of the study was to determine the effects of different heat treatment and varnish application combinations on hardness, scratch resistance, and glossiness of wood materials sampled from limba (Terminalia superba), iroko (Chlorophora excelsa), ash (Fraxinus excelsior L.), and Anatolian chestnut (Castenea sativa Mill.) species. The heat treatment was applied at two levels (150 and 180 oC) for both 3 and 6 hour periods. After the heat treatment, four types of varnish (cellulose lacquer, synthetic varnish, polyurethane varnish, and water based varnish) were applied, and hardness, scratch resistance, and glossiness of varnish film layers of the treated woods were measured. The effects of heat treatment and varnish combination applications on above mentioned variables were analyzed according to the study design (factorial design with 4 (species) x 2 (heat) x 2(duration) x 4 (varnish) = 64 experimental units) with 10 samples for each combination of parameters. Glossiness increased on wood samples for all of the four wood species treated with cellulose lacquer and synthetic varnish and across all heating treatments. However, glossiness values were decreased for all the wood species depending on heating temperature and time. Values of hardness and scratch resistance were also decreased for all the four wood species across all the treatment combinations. The results were obtained from the upper surface of the application process and are thought to contribute to the national economy. PDF
The disintegration of recovered paper is the first operation in the preparation of recycled pulp. It is known that the defibering process follows a first order kinetics from which it is possible to obtain the disintegration kinetic constant (KD) by means of different ways. The disintegration constant can be obtained from the Somerville index results (%ISV) and from the dissipated energy per volume unit (SS). The %ISV is related to the quantity of non-defibrated paper, as a measure of the non-disintegrated fiber residual (percentage of flakes), which is expressed in disintegration time units. In this work, disintegration kinetics from recycled coated paper has been evaluated, working at 20 rev/s rotor speed and for different fiber consistency (6, 8, 10, 12, and 14%). The results showed that the values of experimental disintegration kinetic constant, KD, through the analysis of Somerville index, as function of time, increased with the disintegration consistency. Therefore, as consistency increased, the disintegration time was drastically reduced. The calculation of the disintegration kinetic constant (modeled KD), extracted from the Rayleigh’s dissipation function, showed a good correlation with the experimental values using the evolution of the Somerville index or with the dissipated energy. PDF
Li, S., Gao, Y., Bai, H., Zhang, L., Qu, P., and Bai, L. (2011). "Preparation and characteristics of polysulfone dialysis composite membranes modified with nanocrystalline cellulose," BioRes. 6(2), 1670-1680.
Composite membranes for dialysis were prepared by a Loeb-Sourirajan (L-S) phase inversion process. After adding nanocrystalline cellulose (NCC), the ultrafiltration coefficient of the dialysis membrane could reach 48.37 L•m-2•h-1•mmHg-1. The clearance of lysozyme and urea could reach 70.25 % and 90.38 %, respectively. Simultaneously, the retention ratio of BSA could remain over 96%. Afterwards, in order to judge the hydrophilic nature of the dialysis membrane, the contact angle and surface energy were tested and calculated. And then the tensile strength and elongation ratio were measured to reflect the mechanical properties. The membranes were also observed with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to reveal the state of dispersion and dimensions of NCC. The porous structures of dialysis membrane were researched with both scanning electron microscopy (SEM) and AFM. PDF
Self-assembled multilayers of lignosulfonates (LS) were built up on both quartz slides and cellulose fibers using a Cu2+-mediated layer-by-layer (LBL) technique. The growth of LS multilayers on quartz slides was monitored by UV-Vis spectroscopy, and the absorbance at 205 nm as well as at 280 nm was found to linearly increase with the number of layers. The formation of LS multilayers on fibers surfaces was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The XPS results showed that the surface contents of the characteristic elements, S and Cu, of LS multilayers were increased with the number of layers, which suggests the deposition of LS-Cu2+ complexes on cellulose fibers. Furthermore, there was a good linear relationship between the calculated surface LS content and the increment of LS layers. The AFM morphology results confirmed that the cellulose microfibrils on fiber surface were gradually covered by LS particles, resulting in the increase of surface roughness as self-assembly proceeded. The hydrophobicity of cellulose fiber probed by dynamic contact angle was significantly increased due to LBL self-assembly of LS on its surface. The initial contact angle was increased from 0° to 115° as the cellulose fibers were modified with a 5-layer LS multilayer. The reduction rate of the contact angle was dependent on the number of layers. When the cellulose fiber was modified by a 5-layer LS multilayer, the contact angle shifted from 115 to 98° after 0.12 s, suggesting some degree of hydrophobic character. Therefore, this technique provides a simple but effective way for promoting hydrophobicity of cellulose fibers in a controllable manner. PDF
Shahriarinour, M., Wahab, M. N. A., Mohamad, R., Mustafa, S., and Ariff, A. B. (2011). "Cyanobacterial biomass as N-supplement to oil palm empty fruit bunch (OPEFB) fibre for improvement of cellulase production by Aspergillus terreus in submerged fermentation," BioRes. 6(2), 1696-1706.
The possibility of using dry biomass of a cyanobacterium, Anacystis nidulans, asnitrogen source supplement for improvement of cellulase production by Aspergillus terreus was studied in submerged fermentation using oil palm empty fruit bunch (OPEFB) fibre as a carbon source. For comparison, four other nitrogen sources (ammonium sulphate, urea, peptone, and yeast extract) were also tested. Growth and cellulase production were greatly enhanced in fermentation using biomass of cyanobacterium as the nitrogen source. The use of cyanobacterial biomass as a nitrogen source also reduced the inhibitory effect of high concentrations of CaCl2 to growth of A. terreus and cellulase production. The addition of 0.3 g L-1 CaCl2 to the medium containing OPEFB fibre and cyanobacterial biomass further enhanced the cellulase production, though growth remained unchanged. The final FPase, CMCase, and β-glucosidase obtained in fermentation using 10 g L-1 OPEFB fibre and 6 g/L cynaobacterial biomass with the addition of 3 mM CaCl2 was 0.97 U mL-1, 14.1 U mL-1, and 10.4 U mL-1, respectively. PDF
Saeed, A., Fatehi, P., Ni, Y., and van Heiningen, A. (2011). "Impact of furfural on the sugar analysis of prehydrolysis liquor of kraft-based dissolving pulp production process using the HPAEC technique," BioRes. 6(2), 1707-1718.
High performance anion-exchange chromatography with pulse ampero-metric detector (HPAEC-PAD) is a reliable method to systematically determine the sugar contents in pulp and paper waste streams, including bleaching and extraction liquors. We used the same method to determine the sugar content of industrially produced pre-hydrolysis liquor (PHL) from a kraft-based dissolving pulp production process. The analysis showed that the traditional method cannot be applied for sugar analysis, and an improvement on the method was required. In fact, the presence of furfural in the PHL sample was the reason for the required modification. It was noted that the removal of furfural via evaporation could improve the reliability of the HPAEC technique for sugar assessments. If the concentration of furfural was higher than 0.045% (wt.) in the PHL, the error introduced in the sugar analysis was profound. Also, the industrially produced PHL contained more furfural than the laboratory produced PHL under the same hydrolysis conditions. Consequently, the concentration of furfural in the PHL should be taken into account for sugar analysis using the HPAEC technique. PDF
The present study investigates cellulose phosphate from oil palm biomass (OPEFB-CP) as a potential biomaterial. To this effect, oil palm biomass microcrystalline cellulose (OPEFB-MCC) was phosphorylated using the H3PO4/ P2O5/ Et3PO4/ hexanol method. Characterization of OPEFB-CP was performed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetry (TG), and X-ray diffraction (XRD). The cytotoxicity evaluation of OPEFB-CP was conducted on mouse connective tissue fibroblast cells (L929) using MTS Assay analysis, and the proliferation rate of OPEFB-CP on L929 was assessed by the indirect extraction method, whilst mineralization assessment was carried out by immersion of the material in Simulated Body Fluid (SBF) for 30 days. Disruption of the crystalline structure of OPEFB-MCC, changes in surface morphology of OPEFB-CP, the presence of new FTIR peaks on OPEFB-CP at 2380 cm-1 and 1380 cm-1, and a smaller rate of mass loss of OPEFB-CP are indications of a successful grafting of phosphate groups. OPEFB-CP showed non-cytotoxic in vitro biocompatibility after 72h exposure with an IC-50 value 45mg/mL and a proliferation rate of up to 8 days with no change in cells morphology below the IC-50 concentration. Apatite formation was observed on OPEFB-CP surfaces after 30 days in SBF with a Ca:P ratio of 1.85. PDF
Kord, B., and Hosseini Kiakojouri, S. M. (2011). "Effect of nanoclay dispersion on physical and mechanical properties of wood flour/ polypropylene/ glass fiber hybrid composites," BioRes. 6(2), 1741-1751.
Polypropylene/wood flour composites having different nanoclay and glass fiber contents were fabricated by melt compounding and then injection molding. The physical and mechanical properties were evaluated. The results showed that the tensile modulus and tensile strength of the PP/wood flour composites increased with increasing glass fiber content. However, the impact strength of the PP/wood flour composites progressively decreased with increasing glass fiber content. Dimensional stability of the composites could be improved by increasing the glass fiber content. Also, results indicated that the tensile modulus and tensile strength of composites increased with increase of nanoclay up to 4phc and then decreased. However the impact strength and water absorption of the composites decreased with increasing the nanoclay loading. The morphology of the nanocomposites was examined by using X-ray diffraction (XRD). Morphological findings revealed an intercalated form in the sample with 4 per hundred compounds (phc) concentration of nanoclay, which implies the formation of an intercalated morphology and better dispersion than 6phc, and the d-spacing of clay layers were improved in the composite in the presence of compatibilizer. This project has shown that the composites treated with glass fiber and nanoclay will be desirable as building materials due to their improved stability and strength properties. PDF
Bhat, I. H., Mustafa, M. T. B., Mohmod, A. L., and Abdul Khalil, H. P. S. (2011). "Spectroscopic, thermal, and anatomical characterization of cultivated bamboo (Gigantochloa spp.)," BioRes. 6(2), 1752-1763.
This paper presents spectroscopic, thermal, and morphological properties of two bamboo species viz. Gigantochloa brang and Gigantochloa wrayi. The nature of cell wall structure and distribution of vascular bundles in G. brang and G. wrayi were studied by scanning electron microscopy and transmission electron microscopy techniques. Gigantochloa spp. at various positions and locations showed identical thermal stability and are stable up to 200 °C. The decomposition of cellulose and hemicelluloses component of the culm occurred between 220 °C and 390 °C, while the degradation of lignin takes place above 400 °C. PDF
Dai, Z., Court, G., Li, Z., and Ni, Y. (2011). "Effect of polymers and metal ions on the behavior of pitch from a spruce TMP-based specialty paper mill based on DSC and confocal LSM analysis," BioRes. 6(2), 1764-1772.
The appropriate pitch control is critical in many pulp and paper operations. One of the important approaches for pitch control is to use synthetic polymers. In this paper, we provide evidence from differential scanning calorimetry (DSC) analysis that the pitch deposits formed with polymers, such as polyDADMAC and CPAM, had better thermal stability than those without these polymers. Metal cations also affected the thermal stability of deposited pitch, depending on their valencies. The confocal laser scanning microscope (CLSM) was used to determine the distribution of pitch in the handsheets, and the results showed that polymers can aggregate pitch particles, which facilitates the retention of pitch on the paper sheet. PDF
The pyrolysis of tobacco residue in the presence of metal oxides and metal chlorides was investigated at 300, 400, and 500 °C. Catalysts used were Al2O3, Fe2O3, AlCl3, and SnCl4 in concentrations from 1 up to 5 wt% of the tobacco residue feedstock. The amount of catalysts and the pyrolysis temperature had significant effect on both product distributions and bio-oil composition. The catalytic effect was dominant at the lowest temperature (300 °C). The pyrolysis temperature was decreased by 200 °C compared to the thermal run. Bio-oil contained a large variety of compounds. Nicotine, which is very stable until temperatures in excess of 600 °C, could be degraded at the lowest temperature by using 1 wt% of AlCl3 and 1 wt% of Fe2O3. PDF
Cork is the bark of the cork oak tree (Quercus suber L), a renewable and biodegradable raw bioresource concentrated mainly in the Mediterranean region. Development of its potential uses as a biosorbent will require the investigation of its chemical composition; such information can be of help to understand its interactions with organic pollutants. The present study investigates the summative chemical composition of three bark layers (back, cork, and belly) of five Spanish cork samples and one cork sample from Portugal. Suberin was the main component in all the samples (21.1 to 53.1%), followed by lignin (14.8 to 31%), holocellulose (2.3 to 33.6%), extractives (7.3 to 20.4%), and ash (0.4 to 3.3%). The Kruskal-Wallis test was used to determine whether the variations in chemical composition with respect to the production area and bark layers were significant. The results indicate that, with respect to the bark layer, significant differences were found only for suberin and holocellulose contents: they were higher in the belly and cork than in the back. Based on the results presented, cork is a material with a lot of potential because of its heterogeneity in chemical composition. PDF
Belini, U. L., Hein, P. R. G., Filho, M. T., Rodrigues, J. C., and Chaix, G. (2011). "Near infrared spectroscopy for estimating sugarcane bagasse content in medium density fiberboard," BioRes. 6(2), 1816-1829.
Medium density fiberboard (MDF) is an engineered wood product formed by breaking down selected lignin-cellulosic material residuals into fibers, combining it with wax and a resin binder, and then forming panels by applying high temperature and pressure. Because the raw material in the industrial process is ever-changing, the panel industry requires methods for monitoring the composition of their products. The aim of this study was to estimate the ratio of sugarcane (SC) bagasse to Eucalyptus wood in MDF panels using near infrared (NIR) spectroscopy. Principal component analysis (PCA) and partial least square (PLS) regressions were performed. MDF panels having different bagasse contents were easily distinguished from each other by the PCA of their NIR spectra with clearly different patterns of response. The PLS-R models for SC content of these MDF samples presented a strong coefficient of determination (0.96) between the NIR-predicted and Lab-determined values and a low standard error of prediction (~1.5%) in the cross-validations. A key role of resins (adhesives), cellulose, and lignin for such PLS-R calibrations was shown. PLS-DA model correctly classified ninety-four percent of MDF samples by cross-validations and ninety-eight percent of the panels by independent test set. These NIR-based models can be useful to quickly estimate sugarcane bagasse vs. Eucalyptus wood content ratio in unknown MDF samples and to verify the quality of these engineered wood products in an online process. PDF
Nowadays agricultural wastes represent an alternative source of renewable raw materials. Different processes can be applied to these alternative materials to separate their components and obtain chemical products with high added value, such as bioethanol, organic acids, monomers, and biopolymers. The main objective of this work is to study the extraction of hemicelluloses from corn stalks using different reagents [H2SO4, HNO3, HCL, CH3COOH, CF3COOH, Ca(OH)2, NaOH]. The raw material was characterized and fractionated with autoclave hydrolysis processes (121 ºC, 1:20 solid/liquid ratio, 60 min, pH = 4 or 8). Monomeric sugars concentration, TDS, MO, MI, density, and final pH of the hydrolysate were determined. Hemicelluloses were precipitated and analyzed by different techniques (FTIR, TGA and GPC). The highest yield of hemicelluloses extraction was achieved by sulphuric acid (0.98 g/L total sugar content) and the less effective reagent was Ca(OH)2 (0.52 g/L total sugar content). PDF
Variations in average tracheid dimensions (such as length, diameter, lumen diameter, and wall thickness) and its biometrical ratios including slenderness ratio, flexibility ratio, and Runkell ratio, oven-dry and basic density, longitudinal, radial, tangential, and volume shrinkage, maximum moisture content, and porosity of cypress trees wood (Cupressus sempervirens L.var. horizontalis), which was cultivated in the north of Iran, were studied from the pith to bark (radial position), and along the stem from the base upwards. To measure the mentioned traits, the test specimens were prepared from three stands and 9 discs at different height levels (5, 25, and 50% of the total tree height) based on ASTM-D143 standard. Results indicated that the tracheid length, tracheid cross-sectional dimensions, and its biometrical ratios irregularly varied at each height level, along the stem from the bottom to top, but within the discs, at the same height level biometrical traits in the radial position regularly increased from the pith to bark. Within the tree, wood oven-dry and basic density, longitudinal, radial, tangential, and volume shrinkage varied at each height level, decreasing along the stem from the base upwards. Within the discs, at the same height level, wood density and shrinkage, except for longitudinal shrinkage in the radial position, increased from the pith to bark. The maximum moisture content and porosity varied at each height level, increasing along the stem from the bottom to the top of the tree. Moreover, within the discs, at the same height level in the radial direction porosity decreased and maximum moisture content increased except for at 5% of height level from the pith to bark. PDF
A reaction route accounting for the formation of levulinic acid from 5-hydroxymethylfuran-2-carbaldehyde was deduced on the basis of the mechanism previously offered by Horvat, to match the steps with more details. A newly deduced reaction route was proposed between two intermediate products within this mechanism, and the probabilities of the two mechanisms were compared by Gaussian 03 software. It was found that the conversion from the intermediate 2,3-dihydroxy-5-methyl-2,3-dihydro-furan-2-carbaldehyde (DMDFC) to 2,5-dioxo-hex-3-enal (DOHE) in the original mechanism has a lower net energy barrier than that in the newly deduced mechanism, and thus should be more preferred. The mechanism indicates that DMDFC is first protonized, followed by a proton shift process, and thereafter an OH- ion is added, completing the hydration process. Thereafter, an intramolecular H-shift reaction proceeds, leading to conversion to the intended intermediate product DOHE by the consecutive processes of isomerization and dehydration. PDF
This study has demonstrated a rapid spectroscopic method for the determination of chlorine dioxide and hypochlorous acid concentrations in the pulp bleaching processes. It was found that chlorine dioxide and hypochlorous acid have an isosbestic wavelength of 295 nm. The soluble lignin in such a system is the main interference, but can be corrected by determining the absorbances at 295 nm, 380 nm, and 480 nm. Thus, based on the spectroscopic measurements at 295 nm (the isosbestic point wavelength for chlorine dioxide and hypochlorous acid), 380 nm (absorbance wavelength of chlorine dioxide) and 480 nm (the acid soluble lignin absorbance wavelength), the chlorine dioxide and hypochlorous acid concentrations in the bleaching process can be quantified. However, hypochlorous acid was not detected in the real bleaching effluent for its low content. The present method is simple, rapid, accurate, and has the potential for on-line monitoring of the chlorine dioxide bleaching process. PDF
Properties of heat-treated wood have been studied extensively in recent years. However, study on wood that has been treated in pressurized steam is limited, as most wood heat treatments are carried out in atmospheric steam. The main purpose of this study was to explore the influence of steam pressure on chemical changes of heat-treated wood. Wet chemical analysis, elemental analysis, and FTIR analysis were performed to investigate the changes of cell wall components of Mongolian pine wood. Samples treated in pressurized steam had lower percentages of polysaccharides and higher percentages of lignin compared to those treated in atmospheric steam, indicating greater chemical changes during the treatment. It was also found that thermal degradation of both samples was modest at the treatment temperature of 205 °C. These results help to explain the better dimensional stability and limited strength deterioration of wood treated in pressurized steam. PDF
The amount of residual lignin in birch wood after a hot water extraction in a batch reactor was investigated as a function of extraction temperature and time. A kinetic model fitting the experimental data was then developed to explain delignification of wood during a hot water treatment. Results showed that delignification kinetics involves simultaneous degradation and condensation reactions, with degradation of lignin being much faster than its condensation. Native lignin in wood was successfully modeled as the sum of two fractions with different degradation rates. The rates of degradation and condensation increased along with increasing extraction temperature. The proportion of acid-soluble lignin to acid-insoluble (Klason) lignin in the wood residue decreased with increasing extraction temperature and time, probably due to chemical and structural changes in the lignin during the hot water treatment. Condensed lignin was predominantly determined as Klason lignin. On the other hand, the amount of soluble lignin in the extraction liquor increased slightly with temperature, but remained mostly constant after any extraction time. An insoluble fraction in the liquor that originated from precipitated lignin fragments is believed to contain traces of degradation products from carbohydrates or other degradation compounds. PDF
The decolourisation of reactive and cationic dyes by physical and chemical modified esparto fibers was investigated. Previously the decolourisation of reactive dyes only had been tested and optimized using untreated esparto fibers and those reinforced by zeolite. Non-treated cellulosic esparto fibers can absorb an important amount of dyes. In order to improve absorption properties of esparto fibers, chemical graft copolymerization with acrylic acid (AA), itaconic acid (IA), and a mixture of acrylamide and IA was performed using potassium persulfate as initiator. The effect of physical modification by zeolite was investigated. Reinforced zeolite esparto fibers were obtained from cellulose esparto fibers pre-treated with NaOH, and preformed zeolite powders. The IR spectroscopy, X-ray diffraction, thermal behavior, as well as the surface morphology of the treated fibers were also studied. The results showed that zeolite treated esparto fibers (the first time application of this kind) are more efficient adsorbents than luffa fibers. PDF
In this study a cationic talc was applied to deinked pulp for control of sticky contaminants. Effects of the cationic talc on stickies and dissolved and colloid substances were investigated and compared with those of a conventional talc. Characteristics of wet-end chemistry were examined for the pulp with addition of both kinds of talc samples. Furthermore, influences on paper properties were also compared. The results showed that the addition of cationic talc can effectively decrease the content of stickies and DCS, while reducing the cationic demand of the pulp, and the turbidity of the filtrate. Deposition of stickies can be reduced by about 63% with the addition of 2.0% cationic talc into the pulp, and the DCS was reduced from 1989 mg/L to 1927 mg/L. Addition of cationic talc significantly increased the ash content of the paper, but it negatively influenced the paper strength properties. PDF
Novel starch solutions were prepared by dissolving starch in NaOH/ thiourea/ urea aqueous solution, and they were further used as a surface sizing agent at high solids content in papermaking to improve the surface strength of papers. Two methods were adopted to dissolve the starch. In method A dry starch granules were directly added into the prepared solution. In method B a starch slurry was mixed with the prepared solution. The results revealed that method B was more effective than method A to achieve a lower viscosity of the starch solution. Dissolving temperature played an important role in dissolution of the starch. The viscosity values decreased with a decrease in the temperature of sample preparation. The starch dissolved in 4 wt% NaOH – 3 wt% urea – 3 wt% thiourea aqueous solution at -10°C were optimized to do the further application experiments. This kind of starch solution had lower viscosity and reached better viscosity-temperature stability, the viscosity was stable over a broad range of temperatures, and it also can be stored for over one month under room temperature. The surface sized papers with them had outstanding surface strength. Moreover, the prepared starch solutions were investigated by infrared spectroscopic analysis and scanning electron microscope, respectively, showing the structure of the starch solution. PDF
Han, M., Choi, G.-W., Kim, Y., and Koo, B.-C. (2011). "Bioethanol production by Miscanthus as a lignocellulosic biomass: Focus on high efficiency conversion to glucose and ethanol," BioRes. 6(2), 1939-1953.
Current ethanol production processes using crops such as corn and sugar cane have been well established. However, the utilization of cheaper lignocellulosic biomass could make bioethanol more competitive with fossil fuels while avoiding the ethical concerns associated with using potential food resources. In this study, Miscanthus, a lignocellulosic biomass, was pretreated using NaOH to produce bioethanol. The pretreatment and enzymatic hydrolysis conditions were evaluated by response surface methodology (RSM). The optimal conditions were found to be 145.29 °C, 28.97 min, and 1.49 M for temperature, reaction time, and NaOH concentration, respectively. Enzymatic digestibility of pretreated Miscanthus was examined at various enzyme loadings (10 to 70 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase). Regarding enzymatic digestibility, 50 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase were selected as the test concentrations, resulting in a total glucose conversion rate of 83.92%. Fermentation of hydrolyzed Miscanthus using Saccharomyces cerevisiae resulted in an ethanol concentration of 59.20 g/L at 20% pretreated biomass loading. The results presented here constitute a significant contribution to the production of bioethanol from Miscanthus. PDF
Karaoğlu, M. H., Uğurlu, M., and Kula, İ. (2011). "Adsorption characterization of Co(II) ions onto chemically treated Quercus coccifera shell: Equilibrium, kinetic, and thermodynamic studies," BioRes. 6(2), 1954-1971.
Quercus coccifera shell (QCS), a relatively abundant and inexpensive material, is currently being investigated as an adsorbent to remove cobalt(II) from water. Before the adsorption experiments, QCS was subjected to chemical treatment to provide maximum surface area. Then, the kinetics and adsorption mechanism of Co(II) ions on QCS were studied using different parameters such as adsorbent dosage, initial concentration, temperature, contact time, and solution pH. The loaded metals could be desorbed effectively with dilute hydrochloric acid, nitric acid, and 0.1 M EDTA. The Langmuir and Freundlich models were used to describe the uptake of cobalt on QCS. The equilibrium adsorption data were better fitted to Langmuir adsorption isotherm model. The maximum adsorption capacity (qm) of QCS for Co(II) was 33 mg g-1. Various kinetic models were used to describe the adsorption process. The adsorption followed pseudo second-order kinetic model. The intraparticle diffusion was found to be the rate-limiting step in the adsorption process. The diffusion coefficients were calculated and found to be in the range of 3.11×10−6 to 168.78×10−6 cm2s-1. The negative DH* value indicated exothermic nature of the adsorption. PDF
Magnesium aluminum hydroxides (MAH) of nitrate and carbonate forms were prepared by co-precipitation, dried at different temperatures, and employed as an adsorbent for pitch and stickies in papermaking. Results indicated that MAH that had been heat-treated had higher adsorption capacity to model pitch and stickies at neutral pH. Low-temperature-dried magnesium aluminum hydroxides of nitrate form (MAH-NO3) had higher adsorption capacity to model pitch and model stickies than those of the carbonate form (MAH-CO3). Increasing the drying temperature of MAH reduced the difference of adsorption capacity between MAH-NO3 and MAH-CO3. Higher-temperature-dried magnesium aluminum hydroxides also showed higher adsorption capacity to model pitch and stickies when the drying temperature was lower than 550 oC. MAH displayed higher adsorption capacity while a lower initial adsorption rate of model stickies than of model pitch. The model pitch and stickies were adsorbed on MAH significantly by charge neutralization and distributed mainly on the surface of the platelets of magnesium aluminum hydroxides. The experimental isothermal adsorption data of model pitch and stickies on MAH dried at 500 oC fit well to the Freundlich and Dubinin–Radushkevich isotherm equations. PDF
This paper describes preparation of carboxymethylated and carboxylated cellulosic fibers from waste paper. Chemical properties of the product were distinguished by Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) spectral analysis. To produce carboxylated and crosslinked fibers and also to increase the anionic surface charge of the fibers, maleic anhydride was used in three different batches; 0, 1%, and 5%. The treatment condition for producing carboxymethylated fibers also involved the use of isopropanol, sodium hydroxide solution, and monochloroacetic acid. The product was purified with 70/30 methanol/ water. Then one sample was neutralized with acetic acid and the other was considered as a sample without having been neutralized. Effects of these treatments were evaluated by FTIR and XRD analysis. The results of FTIR analysis indicated that the carboxyl and methyl functional groups had increased in the carboxymethylated fibers and that just carboxyl groups had increased in carboxylated fibers. The results of XRD analysis showed that the crystallinity of cellulose had decreased in both the carboxymethylated and carboxylated fibers. PDF
Switchgrass (Panicum virgatum), a perennial grass native to North America, is a promising energy crop for bioethanol production. The aim of this study was to optimize the enzymatic saccharification of thermo-mechanically pretreated switchgrass using a thermostable cellulase from Geobacillus sp. in a three-level, four-variable central composite design of response surface methodology. Different combinations of solids loadings (5 to 20%), enzyme loadings (5 to 20 FPU g-1 DM), temperature (50 to 70 oC), and time (36 to 96 h) were investigated in a total of 30 experiments to model glucose release from switchgrass. All four factors had a significant impact on the cellulose conversion yields with a high coefficient of determination of 0.96. The use of higher solids loadings (20%) and temperatures (70 oC) during enzymatic hydrolysis proved beneficial for the significant reduction of hydrolysis times (2.67-times) and enzyme loadings (4-times), with important implications for reduced capital and operating costs of ethanol production. At 20% solids, the increase of temperature of enzymatic hydrolysis from 50 oC to 70 oC increased glucose concentrations by 34%. The attained maximum glucose concentration of 23.52 g L-1 translates into a glucose recovery efficiency of 46% from the theoretical yield. Following red yeast fermentation, a maximum ethanol concentration of 11 g L-1 was obtained, accounting for a high glucose to ethanol fermentation efficiency of 92%. The overall conversion efficiency of switchgrass to ethanol was 42%. PDF
Soda lignin was divided into two fractions with different molecular weights by methanol extraction. Lignin amine was synthesized from the low-molecular-weight lignin fraction via Mannich reaction and was used for interfacial modification of poly-(vinylchloride) (PVC)/wood-flour composites. The PVC/wood-flour composites were prepared from surface-treated wood flour and PVC by melt compounding. The lignin amine treatment provided almost equivalent improvement in mechanical performances of composites as aminosilane treatment does. The tensile and impact strengths of composites prepared from 30phr of wood flour treated with 2wt% lignin amine were increased by 21.0% and 43.9%, respectively, compared to those prepared from untreated wood flour. Furthermore, lignin amine treatment could also significantly reduce the water absorption of composites. A significant increase in storage modulus (E’) was observed upon incorporation of wood flour with lignin amine treatment. The improved dispersion of wood flour in polymer matrix was observed by SEM images when the wood flour was treated by lignin amine. The experimental data indicate that the polymer-wood interfacial combination is strengthened. PDF
An activation process involving chitosan was conducted to prepare electroless nickel plated wood veneers for electromagnetic interference (EMI) shielding. In this process Pd(Ⅱ) ions were chemically adsorbed on wood surface modified with chitosan. Then they were reduced and dipped into a plating bath in which Ni-P co-deposition was successfully initiated. The coatings were characterized by SEM-EDS and XRD. The metal deposition, surface resistivity, and electromagnetic shielding effectiveness were measured. The morphology of the coating observed by SEM was uniform, compact, and continuous. EDS results showed that the coating consists of 1.8 wt.% phosphorus and 98.2 wt.% nickel. XRD analysis indicated that the coating was crystalline, which is supposed to be related to the low phosphorus content. The plated birch veneers exhibited electro-conductivity with surface resistivity of 0.24 Ω·cm-2 and good electromagnetic shielding effectiveness of over 50 dB in frequency range from10 MHz to 1.5 GHz. PDF
Köse, C., Terzi, E., Büyüksarı, Ü, Avci, E., Ayrılmış, N., Kartal, S. N., and Imamura, Y. (2011). "Particleboard and MDF panels made from a mixture of wood and pinecones: Resistance to decay fungi and termites under laboratory conditions," BioRes. 6(2), 2045-2054.
Particleboard and medium density fiberboard (MDF) panels were produced using stone pine (Pinus pinea) cones, which were mixed with either wood particles or fibers from pine and beech wood at various ratios. Specimens from the panels were subjected to AWPA E10-06 soil-block tests using two brown-rot fungi, Gloeophyllum trabeum and Postia placenta and two white rot fungi, Trametes versicolor and Pleurotus ostreatus for 12 weeks. Specimens were also subjected to subterranean termites, Coptotermes formosanus, according to the JIS K 1571 standard test method for 3 weeks. Pinecone material in the furnish had no considerable effect on the decay resistance of particleboard and MDF specimens subjected to the brown-rot fungi; however, mass losses in the specimens exposed to the white-rot fungi were gradually decreased as the pinecone ratio in the furnish increased. No increased resistance was observed in the specimens exposed to the termites. In some cases, the specimens containing pinecone furnish had greater mass losses compared to the control specimens. PDF
Roohnia, M., Hashemi-dizaji, S.-F., Brancheriau, L., Tajdini, A., Hemmasi, A.-H., and Manouchehri, N. (2011). "Effect of soaking process in water on the acoustical quality of wood for traditional musical instruments," BioRes. 6(2), 2055-2065.
The damping coefficient of the first mode in the longitudinal vibration of mulberry and walnut woods was characterized to find justifications for the water soaking of woods in traditional musical instrument industries in Iran. Visually clear and sound beams were prepared from Morus alba and Juglans regia, and the damping coefficient in the temporal field was evaluated before and after three continuous cycles of soaking of specimens in distilled water (24 hours, pH 7, and temperature 50 oC). Experiments were conducted with free longitudinal vibration using the free-free bar method in 360 × 20 × 20 (L ×R ×T) dimensions. Soaking cycles homogenized and decreased the damping coefficient in both species. On the basis of such results, the suitability of water soaked specimens is discussed in traditional musical instrument industries in Iran, taking into the account the longitudinal sound velocity, modulus of elasticity, and density affecting the acoustic limits. These two series of testing specimens were suitable in resonators and xylophone bars for backs, sides, and ribs and not for top plates, unless as the outstanding piece, since they marginally meet the density, sound velocity and damping coefficient limits qualified for those applications. PDF
Aspergillus niger NCIM 1207 produced significantly high levels of β-glucosidase and β-xylosidase activities in submerged fermentation. Cellulose induced only β-glucosidase, while xylan induced both β-glucosidase and β-xylosidase activities. Both the enzymes of this strain were found to undergo catabolite repression in the presence of high concentrations of glucose and glycerol. The sudden drop in pH of the fermentation medium below 3.5 caused the inactivation of enzymes when the fungus was grown in glycerol-containing media at lower temperatures. The growth of the organism at 36 oC led to an increase in pH of the fermentation above 6.0 that affected β-xylosidase activity significantly. Highest levels of β-glucosidase ((19 IU mL-1 or 633 IU g-1 of substrate) and β-xylosidase (18.7 IU/mL-1 or 620 IU g-1 of substrate) activities were detected when A. niger was grown at 30 oC for first five days followed by further incubation at 36 oC. Such a process of growing the organism at lower temperatures (growth phase) followed by producing the enzymes at higher temperatures (production phase) in case of fungal systems has not been reported so far. The zymogram staining of the β-glucosidase demonstrated that A. niger produced only single species of β-glucosidase. We feel that A. niger NCIM 1207 is a potential candidate to produce both β-glucosidase and β-xylosidase in high amounts that can be used to supplement commercial cellulase preparation. PDF
Area, M. C., Felissia, F. E., Carvalho, M. G. V. S., Ferreira, P. J., Barboza, O. M., and Bengoechea, D. I. (2011). "Caracterization of Eucalyptus grandis kraft pulps treated with phosphontates in different stages of TCF bleaching," BioRes. 6(2), 2077-2090.
The addition of a phosphonated chelant (DTPMPA) at different points of a TCF bleaching sequence and its effect on pulp properties were studied in this work. An industrial Eucalyptus grandis kraft pulp was submitted to a counter-ion exchange (Ca2+ or Na+ form) and was then bleached using DTPMPA in the washing or in the bleaching stages of two distinct sequences: OOpP and OQOpP (20 pulps). The counter-ion exchange affected fibre length, as well as the handsheets bulk and air permeability (higher for Na+-based pulps) and handsheet tensile strength, brightness, skeletal density, and total porosity based on Hg porosimetry (higher for Ca2+-based pulps). The hydrogen peroxide consumption in Op and P stages achieved the lowest values when the chelant was distributed rather than applied in a separate Q stage. The addition of chelant in the P stage provides pulps with higher ISO brightness (>85%). The chelant effects were always more noticeable in Ca2+-based pulps. PDF
Bamboo timber is very vulnerable to mould fungi, a characteristic that is attributed to the rich sugar, starch, and protein present in bamboo. Solvents including cold water, hot water, benzene/ethanol, ethanol/ether, 1% NaOH, and 1% HCl can dissolve corresponding components from bamboo, which might be helpful to the resistance of bamboo against mould fungi. In order to study the relationship between surface nutrition and mildew of bamboo, mould resistances of bamboo blocks treated with different solvents were tested in the laboratory and field. Results showed that bamboo treated with cold water, hot water, benzene/ethanol or ethanol/ether had almost the same resistances with the controls against mould fungi, and the surfaces became covered with mycelium within 10 days in laboratory tests, and 5 weeks in field tests. 1% NaOH and 1% HCl were helpful to the mould resistance of bamboo, of which, 1% HCl treatments behaved the best, especially in the field tests. PDF
This paper reports on the synthesis of Cannabis indica fiber-reinforced composites using Urea-Resorcinol-Formaldehyde (URF) as a novel matrix through compression molding technique. The polycondensation between urea, resorcinol, and formaldehyde in different molar ratios was applied to the synthesis of the URF polymer matrix. A thermosetting matrix based composite, reinforced with lignocellulose from Cannabis indica with different fiber loadings 10, 20, 30, 40, and 50% by weight, was obtained. The mechanical properties of randomly oriented intimately mixed fiber particle reinforced composites were determined. Effects of fiber loadings on mechanical properties such as tensile, compressive, flexural strength, and wear resistance were evaluated. Results showed that mechanical properties of URF resin matrix increased considerably when reinforced with particles of Cannabis indica fiber. Thermal (TGA/DTA/DTG) and morphological studies (SEM) of the resin, fiber and polymer composite thus synthesized were carried out. PDF
This study was carried out to determine the effects of adhesive ratio and pressure time on thickness swelling (TS), internal bond (IB), modulus of rupture (MOR), and modulus of elasticity (MOE) properties of oriented strand board (OSB). For this purpose, 80 mm long strands made of Scots pine (Pinus sylvestris L.) were bonded with phenol-formaldehyde resin at three different ratios (3, 4.5, and 6%) to produce three-layer cross-aligned OSBs. Strands used for the production of OSB panels were made up 40% of core layer and 60% of outer layers. The panels were pressed for three different press times, from 3, 5, to 7 minutes, under 0.4 MPa pressure, aiming for a target density of 0.70 g/cm3. TS, IB, MOR, and MOE properties of OSB panels were evaluated according to the standards (TSE EN 117-319-310). Results showed that MOR and MOE values were changed in the ranges 25.31 to 42.27 N/mm2, and 2848.90 to 6545.63 N/mm2, respectively. Also, the results showed that as adhesive ratio and pressure time increased, the TS, MOR, and MOE values increased too. PDF
Studies on the softening behavior of in situ lignin of normal wood in a given species have never been performed before due to the relatively narrow lignin content and lignin structural variation within one species. Using transgenic trees with different levels of lignin content and/or syringyl to guaiacyl propane (S/G) ratio helped us to overcome this problem. Submersion three-point bending and parallel-plate compression-torsion dynamic mechanical analyses were conducted on one-year-old wild type and transgenic aspen (Populus tremuloides Michx.). The different genetic modifications included groups with reduced lignin content, increased S/G ratio, and both reduced lignin content and increased S/G ratio. Measurements with both methods revealed a statistically significant decrease in glass transition temperature in the reduced-lignin genetic group compared to the wild-type. Increase in the S/G ratio did not affect the thermo-mechanical properties; these results contradict claims that increasing the methoxyl groups would reduce lignin cross-linking and the glass transition temperature. PDF
de Palacios, P., Esteban, L. G., García Fernández, F., García-Iruela, A., González-Adrados, J. R., and Conde, M. (2011). "Comparative study of the 35 oC sorption Isotherms of cork stripped from the tree in 1968 and 2006," BioRes. 6(2), 2135-2144.
A study was made of the hygroscopicity of two samples of cork with the same characteristics, taken from trees of the same age but with a 38-year gap between debarking. This was achieved by plotting the 35ºC sorption-desorption isotherms and fitting them using the GAB model. Infrared spectra were used to determine any chemical changes in the cell wall. Extended exposure to controlled relative humidity and temperature did not cause hygroscopic changes to the cork. The equilibrium moisture content values were not significantly different in the two samples, but the monolayer saturation moisture content values were significantly lower in the older cork. This may be due to partial saturation of the moisture sorptive sites in the cell wall over time. PDF
Electrochemical generation of oxidants was studied to find new solutions to control microbial contamination at paper mills. Laboratory and semi-pilot trials using a Wet End Simulator indicated that the combination of an electrochemically produced halogen-containing oxidant together with sodium percarbonate was an efficient new biocide concept, especially in fine papermaking. Addition of sodium percarbonate considerably reduced the need for halogen-containing biocides, thus lessening risk of corrosion. The trials with samples from fine paper machines indicated that the new concept required halogenated biocides to be dosed first, and the time delay between additions of biocide needed to be sufficient to ensure that no residual halogen was left when sodium percarbonate was added. Electrochemical generation enables on-site biocide production, which decreases transportation cost, risk associated with storage of hazardous chemicals, and biocide lost due to degradation. Thus, on-site generation of biocides together with potential reduction in amount of halogen containing oxidants make this dual concept economically attractive and environmentally positive. PDF
Recent years have seen explosive growth in research concerning the use of cellulosic materials, either in their as-recieved state or as modified products, for the removal of heavy metal ions from dilute aqueous solutions. Despite highly promising reports of progress in this area, important questions remain. For instance, it has not been clearly established whether knowledge about the composition and structure of the bioadsorbent raw material is equally important to its availability at its point of use. Various physical and chemical modifications of biomass have been shown to boost the ability of the cellulose-based material to bind various metal ions. Systems of data analysis and mechanistic models are described. There is a continuing need to explain the mechanisms of these approaches and to determine the most effective treatments. Finally, the article probes areas where more research is urgently needed. For example, life cycle analysis studies are needed, comparing the use of renewable biosorbents vs. conventional means of removing toxic metal ions from water. PDF