Solventless Delignification of Wood Flour with TiO2/poly(ethylene oxide) Photocatalyst System

A novel solventless delignification of a defatted Picea glehnii wood flour sample was performed using a TiO₂/polyethylene oxide (PEO) photocatalyst system. A cell wall structure of the wood flour was directly observed, showing that its lignin fraction was removed by the photodegradation. The total lignin amount was slightly decreased as compared with that of the pristine sample, and the vanillin formation was confirmed by the ¹H-NMR measurement. The TiO₂ worked as a radical initiator, and simultaneously acid and aldehyde compounds produced by the PEO photolysis did as an accelerator for the solventless delignification. Although the photocatalyst system showed high delignification activity even for a low molecular lignin model, the delignification of the wood flour sample was confined to the surface. It was found that the suppressed delignification behavior was due to crosslinked structure of lignin.     

Ozone–dioxane delignification from the cell walls of Japanese cypress (Chamaecyparis obtusa Endl.)

Delignification from the cell walls with a combination of ozone oxidation and dioxane–water extraction using thin sections of a softwood, Japanese cypress (Chamaecyparis obtusa Endl.), was studied to determine its suitability for the production of recyclable cellulose-based materials from wood waste. The visible-light absorption spectra of treated wood sections revealed that delignification from the cell walls with ozone increased with increasing ozonization time. Ozone delignification proceeded from the lumen side toward the middle lamella within the secondary wall of a cell, and it proceeded faster in early wood than in late wood within an annual ring. Mild ozonization for 10–30 min was sufficient for the removal of lignin from the cell walls when sections were extracted with dioxane after ozonization. The results obtained here demonstrate that microspectrometry coupled with the Wiesner reaction is useful for the quantitative analysis of lignin in cell walls.     

A Novel and Formaldehyde-Free Preparation Method for Lignin Amine and Its Enhancement for Soy Protein Adhesive

In this work, a novel two-step process to prepare primary lignin amine was developed. The lignin used in this study was obtained from the residue of cellulosic sugar fermentation for bioethanol (referred as “lignin”). The lignin was initially oxidized through Fenton oxidation. The oxidized lignin was further converted to lignin amine by reductive amination. Ammonia was used in the second step leading to give the highly active primary lignin amine. The oxidation and reduction exhibited relatively high yields of 80.0 and 91.2 % respectively. For comparison, lignin was partially depolymerized via mild hydrogenolysis and then the partial depolymerized lignin was also converted to lignin amine using the same method. The obtained lignin amines were characterized in detail using elemental analysis, proton nuclear magnetic resonance (¹H NMR), and Fourier transform infrared spectroscopy (FTIR). Further, modification of soy protein adhesive by lignin amine was exemplified in wood bonding, and the results indicated that addition of lignin amine greatly increased water resistance of soy protein adhesives.     

Synthesis and identification of graft copolymers of wood pulp and styrene

Based on the graft copolymerization reactions of lignin and vinyl monomers, a series of graft copolymers of wood pulp and styrene (1-phenylethene) has been synthesized. The wood pulps used in this research are unbleached products produced by chemical, thermal, and mechanical pulping. All of them contain a high content of lignin (25–29 wt%). The grafting reaction is a free radical polymerization coinitiated by calcium chloride, hydrogen peroxide, and wood pulp in dimethylsulfoxide at 30°C. The effect of reaction temperature, reaction time, and the amount of the reactants on the conversion of monomer, yield of product, weight increase of pulp, and grafting efficiency of monomer has been studied. The grafted wood pulp was separated from homopolystyrene formed during the reaction by extraction of the reaction product with benzene in a Soxhlet apparatus for at least 48 h. The results show that after the reaction, the weight of all wood pulps was significantly increased and the weight increase of very high yield sodium bisulfite pulp (VHYS) was 333%. This proves that a part of the polymerized styrene was chemically bound to the wood pulp. The Fourier transform infrared (FTIR) spectra of the extracted products show absorbance peaks characteristic of both wood and polystyrene and, thus, provide strong proof of grafting. Grafting has completely changed the surface properties of the starting wood pulp from hydrophilic to hydrophobic, and under ordinary thermal compression conditions, thermoplastic composite objects of good uniformity can be made directly from reaction products which contain up to 52 wt% wood pulp.     

Qualitative and Quantitative Analysis of Lignin Produced from Beech Wood by Different Conditions of the Organosolv Process

Lignins in general have been extensively studied, while beech wood lignin in particular is rarely researched. In the present work, Organosolv isolated lignin from beech wood (OBL) has been characterized. The isolation was done by two methods: (a) by using sulfuric acid at 170 °C and a reaction time of 120 min and (b) at a temperature of 180 °C for 240 min. A range of analytical methods were applied including elemental analysis, FT-IR, UV–Vis, ³¹P NMR, SEC, Pyrolysis-GC/MS and HPLC to gain information about establish the purity, structure, molecular weight, thermal behavior and to determine carbohydrate residues according to the NREL protocol. FT-IR and UV–Vis spectra of OBL revealed expected typical absorptions for lignins. NREL analysis presented a carbohydrate-free lignin fraction which has not been achieved to date. TGA and DSC are used to study the thermal behavior of the isolated lignins and showed a relatively low glass transition temperatures (T_g: 123 °C) and decomposition temperatures of 348 and 381 °C. The pyrograms generated from the pyrolysis–GC/MS at 550 °C consisted mainly of fragments of syringyl, guaiacyl and hydroxyphenyl units, thereby confirming the results of the NMR analysis. Our findings support Organolsolv as an efficient method to isolate pure lignin fractions from beech wood with practical value in industry.     

The decomposition of wood products in landfills in Sydney, Australia

Three landfill sites that had been closed for 19, 29 and 46 years and had been operated under different management systems were excavated in Sydney. The mean moisture content of the wood samples ranged from 41.6% to 66.8%. The wood products recovered were identified to species, and their carbon, cellulose, hemicellulose and lignin concentration were determined and compared to those of matched samples of the same species. No significant loss of dry mass was measured in wood products buried for 19 and 29 years, but where refuse had been buried for 46 years, the measured loss of carbon (as a percentage of dry biomass) was 8.7% for hardwoods and 9.1% for softwoods, equating to 18% and 17% of their original carbon content, respectively. The results indicate that published decomposition factors based on laboratory research significantly overestimate the decomposition of wood products in landfill.     

Extraction of Lignosulfonate from Black Liquor into Construction of a Magnetic Lignosulfonate-Based Adsorbent and Its Adsorption Properties for Dyes from Aqueous Solutions

Journal of Polymers and the Environment - Lignosulfonate, one of the lignin derivatives, was extracted from the black liquor as a byproduct of the wood and paper industry. It was used to prepare...     

Forest products decomposition in municipal solid waste landfills

Cellulose and hemicellulose are present in paper and wood products and are the dominant biodegradable polymers in municipal waste. While their conversion to methane in landfills is well documented, there is little information on the rate and extent of decomposition of individual waste components, particularly under field conditions. Such information is important for the landfill carbon balance as methane is a greenhouse gas that may be recovered and converted to a CO(2)-neutral source of energy, while non-degraded cellulose and hemicellulose are sequestered. This paper presents a critical review of research on the decomposition of cellulosic wastes in landfills and identifies additional work that is needed to quantify the ultimate extent of decomposition of individual waste components. Cellulose to lignin ratios as low as 0.01-0.02 have been measured for well decomposed refuse, with corresponding lignin concentrations of over 80% due to the depletion of cellulose and resulting enrichment of lignin. Only a few studies have even tried to address the decomposition of specific waste components at field-scale. Long-term controlled field experiments with supporting laboratory work will be required to measure the ultimate extent of decomposition of individual waste components.     

Physical Morphology and Quantitative Characterization of Chemical Changes of Weathered PVC/Pine Composites

This study investigated weathering effects on polyvinyl chloride (PVC) based wood plastic composites (WPC), with a focus on the color and structure that is attributed to the material composition. It is directed towards quantifying the main chemical modifications, such as carbonyl and vinyl groups which are formed during weathering. These composites were subjected to three weathering regimes: exterior, accelerated xenon-arc, and accelerated UVA. The change in color was monitored using colorimetry. Fourier transform infrared spectroscopy was used to identify and quantify the chemical modifications (carbonyl formation and vinyl propagation) due to weathering. Additionally, scanning electron microscopy was employed to observe the physical morphological changes that occurred. The results showed that exterior and accelerated xenon-arc and UVA weathering regimes increased the degree of lightness, total color change, carbonyl concentration, and wood loss on the surfaces of the weathered composites. The increased carbonyl concentration during weathering implied that degradation had occurred by oxidation process. Also, oxidation and lignin (from the wood) degradation influenced the color (lightness) of PVC based WPC upon weathering.     

Wood Modification Effects on Weathering of HDPE-Based Wood Plastic Composites

The effects of weathering on the constituents of wood and polymer matrix behavior in wood plastic composites (WPCs) were investigated. WPCs were produced from pine, extractives-free pine, and pine holocellulose fibers (60%) together with HDPE (40%). These composites were subjected to xenon-arc accelerated and outside weathering for a total of 1200 h and 120 days, respectively. The color and chemical changes that occurred on the surface of the WPCs were analyzed using a set of analytical techniques. For pine and extractive-free pine filled composites, the results showed that the total color change, lightness, and oxidation increased, while the lignin content decreased. In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of extracted HDPE decreased with an increase in exposure time of the composites. However, HDPE crystallinity increased with longer exposure time. Lightness of holocellulose-based WPC changed the least while the change in its HDPE crystallinity was not significant compared to the other composite types. Therefore, holocellulose-based WPC may be preferred for applications where color stability is of high priority.     

Contribution to the Study of Fungal Attack on Some Plasticized Vinyl Formulations

The objective of this study was to develop new vinyl flooring formulations with increased resistance to fungi and microorganisms attack, by using plasticizers having a chemical composition different from that of common di-ethylhexyl phthalate (DOP). It is suspected that during the vinyl flooring life service, the attack of fungi and microorganisms leads to the degradation of DOP and the release of some volatile organic compounds (VOC). For this reason the new materials were formulated with plasticizers having chemical composition different of that of DOP i.e.: diethyleneglycol dibenzoate (2–45), tricresyl phosphate (Lindol) and phenol alkylsulphonic ester (Mesamoll). For the same reason in the new flooring formulations the vinyl polymer, vinyl chloride-vinyl acetate copolymer (VC-VAc), was partially replaced with lignin (L) a natural polymer and major component of wood and vascular plants. Besides its other functions in wood, L imparts resistance to the most microorganisms attack. An organosolv lignin Alcell lignin (AL) was utilized as partial replacement of VC-VAc copolymer.The influence of the new plasticizers, as well as the influence of the partial replacement of VC-VAc copolymer with L on the resistance of the new formulations to fungal attack was evaluated following a standard procedure given in ASTM G 21–2002 “Determining Resistance of Synthetic Polymeric Materials to Fungi”. The evaluation has been undertaken for controls (formulated without AL) and blends (formulated with 20 parts AL) specimens. Test specimens were inoculated with a mixture of five fungi. Following 28 days of incubation at 28°C and 95% relative humidity, the specimens were examinated visual and under the microscope and rated for fungal growth. Weight loss, changes in mechanical properties and changes in glass transition temperature due to the effect of biodeterioration were also determined.Although each plasticizer has a specific resistance to hydrolysis due to differences among ester groups, the visible effects of fungal attack, in formulations without AL, is similar for all plasticized controls, with the exception of formulations incorporating diethyleneglycol dibenzoate (2–45) in which a higher degree of biodegradation was always present. Based on the weight loss of specimens formulated without AL, their resistance to fungal attack can be rated as follows: . The same rating is applicable for blend specimens. The results have demonstrated that each particular AL-plasticizer-additives formulation has its specific mechanism of biodegradation.     

Decomposition of forest products buried in landfills

The objective of this study was to investigate the decomposition of selected wood and paper products in landfills. The decomposition of these products under anaerobic landfill conditions results in the generation of biogenic carbon dioxide and methane, while the un-decomposed portion represents a biogenic carbon sink. Information on the decomposition of these municipal waste components is used to estimate national methane emissions inventories, for attribution of carbon storage credits, and to assess the life-cycle greenhouse gas impacts of wood and paper products. Hardwood (HW), softwood (SW), plywood (PW), oriented strand board (OSB), particleboard (PB), medium-density fiberboard (MDF), newsprint (NP), corrugated container (CC) and copy paper (CP) were buried in landfills operated with leachate recirculation, and were excavated after approximately 1.5 and 2.5 yr. Samples were analyzed for cellulose (C), hemicellulose (H), lignin (L), volatile solids (VS), and organic carbon (OC). A holocellulose decomposition index (HOD) and carbon storage factor (CSF) were calculated to evaluate the extent of solids decomposition and carbon storage. Samples of OSB made from HW exhibited cellulose plus hemicellulose (C + H) loss of up to 38%, while loss for the other wood types was 0–10% in most samples. The C + H loss was up to 81%, 95% and 96% for NP, CP and CC, respectively. The CSFs for wood and paper samples ranged from 0.34 to 0.47 and 0.02 to 0.27 g OC g^?1 dry material, respectively. These results, in general, correlated well with an earlier laboratory-scale study, though NP and CC decomposition measured in this study were higher than previously reported.     

Storage stability of biocrude oils from fast pyrolysis of poultry litter

The unstable nature of biocrude oils produced from conventional pyrolysis of biomass is one of the properties that limits its application. In the disposal of poultry litter via pyrolysis technology, the biocrude oil produced as a value-added product can be used for on farm applications. In this study, we investigated the influence of bedding material (wood shavings) on the storage stability of biocrude oils produced from the fast pyrolysis of poultry litter. The biocrude oils produced from manure, wood (pine and oak), and mixtures of manure and wood in proportions (75:25 50:50, and 25:75 w/w%) were stored under ambient conditions in sealed glass vials for a period of 6 months and their stability were monitored by measuring the changes in viscosity over time. The manure oil had the lowest rate of viscosity change and thus was relatively the most stable and the oils from the 50:50 w/w% litter mixtures were the least stable. The rate of viscosity change of the manure biocrude oil was 1.33 cP/day and that of the 50/50 litter mixture was 7.6 cP/day for pine and 4.17 cP/day for oak.The spectrometric analyses of the biocrude oils showed that the presence of highly reactive oxygenated functionalities in the oil were responsible for the instability characteristic of the litter biocrude oils. The poor stability of the biocrude oil from the 50:50 w/w% litter mixtures was attributed to reactions between nitrogenous compounds (amides) from protein degradation and oxygenated compounds from the decomposition of polysaccharides and lignin. The addition of 10% methanol and 10% ethanol to the oil from 50% manure and 50% pine reduced the initial viscosity of the oil and was also beneficial in slowing down the rate of viscosity change during storage.     

Isolation and Characterization of Cellulose Micro/Nanofibrils from Douglas Fir

Cellulose micro/nanofibrils were successfully extracted from softwood Douglas fir in three distinct stages. Initially raw Douglas fir wood chips were subjected to a hot water extraction (HWE) treatment. Then HWE treated cellulosic fibers underwent a bleaching process followed by a mild ultrasonication. Chemical composition analysis according to ASTM standards confirmed that most of hemicelluloses and nearly all lignin were removed during the first two stages, respectively. Microscopy studies showed formation of nanofibrils during the ultrasonication process, and increasing ultrasonication time led to generation of greater percentage of nanofibrils. With the removal of the matrix materials, the crystallinity of the cellulosic fibers was increased, whereas thermal stability was maintained. HWE opened up the cell wall structure, thereby facilitating the subsequent fractionation into micro/nanofibrils. The obtained cellulose micro/nanofibrils could serve as reinforcing material in composite products or raw material for other applications, such as filtration membrane.     

Lignin/Poly(ε-Caprolactone) Blends with Tuneable Mechanical Properties Prepared by High Energy Ball-Milling

Polymer blends between lignin, a natural, widely available, no-cost material, and Poly(ε-caprolactone) (PCL), a biodegradable polymer, have been prepared using the ‘clean’, friendly to the environment, technique of the High Energy Ball Milling (HEBM). Two kinds of lignin have been used, Straw lignin, obtained through the Steam Explosion process (SE lignin), and/or Lignosulphonated one (LS lignin). The tensile mechanical tests have shown that, at certain specific compositions, the blends, in particular those with both SE and LS lignin, have good mechanical properties. In particular, by varying the blend composition it is possible to obtain materials with tuneable properties, therefore useful for different applications. Dynamic-Mechanical-Thermal Analysis (DMTA) reveals substantial immiscibility of the blends. Experiments of UV irradiation show that lignin acts as an UV stabilizer for PCL. The effect is higher with SE lignin, likely due to its low molecular weight, which allows the short lignin chains to diffuse more easily within the amorphous regions of PCL.     

Laccase-Assisted Grafting of Acrylic Acid onto Lignin for its Recovery from Wastewater

The acrylic acid (AA) in the wastewater from paint manufacturing could be recovered by grafting to lignosulfonate in the presence of laccase and tert-butyl hydroperoxide (t-BHP). The low concentration of t-BHP did not inhibit the laccase activity, but improved the radical formation on lignin by laccase reaction, then initiated AA polymerization on lignin. The results showed laccase took a significant role for AA grafting to lignin. 94 % of AA could be polymerized on lignin by laccase/t-BHP, while only 32 % of AA was grafted on lignin with the same condition without laccase. The ratio of lignin to acrylic acid also affected AA recovery, and higher concentration of acrylic acid led to high recovery rate of AA. In this reaction system, the suitable range of temperature was 30–40 °C for the chemo-enzymatic reaction. The AA grafted on lignin could be precipitated by calcium ion and recovered.     

Recovery of Kraft Lignin from OPEFB and Using for Lignin–Agarose Hydrogel

Lignins from the spent pulping liquor were normally acquired as waste product of pulp and paper mills. The possibilities of utilizing kraft lignin have yet been developed for commercial innovation. The objectives of this research are to recovery and utilization of lignin from black liquor of oil palm empty fruit bunches (OPEFBs). Kraft lignins from the OPEFBs black liquor were recovered by acidification procedure. They were precipitated at pH 4, 3, and 2 in order that determine the optimum pH for isolation. It can be clearly seen that the best condition of lignin precipitation was at pH 3. It offered the highest yield and purity. The kraft lignin and agarose were utilized as the crude material for the production of lignin–agarose hydrogel. Lignin–agarose hydrogel could be prepared by using epichlorohydrin as the cross-linking agent. The cross-linking occurrence was recognized by FTIR. Physical and chemical properties of hydrogel were investigated. Gel strength of lignin–agarose hydrogel was characterized by texture personal analysis. The results demonstrated that the gel strength increased with increasing of lignin and epichlorohydrin (ECH) in agarose solutions. 5% lignin, 5% agarose and 10 mL ECH contributed the best gel formation and the great mechanical properties. The effect of cross-linking condition on the gel properties, for example, gel hardness and fracturability, was examined.     

Analysis of the relation between the cellulose,hemicellulose and lignin content and the thermal behavior of residual biomass from olive trees

The heterogeneity of biomass makes it difficult if not impossible to make sweeping generalizations concerning thermochemical treatment systems and the optimal equipment to be used in them. Chemical differences in the structural components of the biomass (cellulose, hemicellulose, and lignin) have a direct impact on its chemical reactivity. The aim of this research was to study the influence of the organic components of the raw material from olive trees (leaves, pruning residues, and wood) in the combustion behavior of this biomass, as well as to find the component responsible for the higher ash content of olive leaves. Accordingly, the study used a thermogravimetric analyzer to monitor the different states and complex transitions that occurred in the biomass as the temperature varied. The decomposition rates of the different samples were analyzed in order to establish a link between each combustion phase and the composition of the raw materials. Two methods were used to determine the hemicellulose and cellulose contents of biomass from olive trees. Significant differences among the results obtained by the different methods were observed, as well as important variations regarding the chemical composition and consequently the thermal behavior of the raw materials tested.     

Styrene/Lignin-Based Polymeric Composites Obtained Through a Sequential Mass-Suspension Polymerization Process

A modified sequential mass-suspension polymerization was employed to ensure adequate dispersion of lignin into the monomeric phase. Due to its complex macromolecular structure and low compatibility with styrene, eucalyptus wood-extracted lignin, via a modified Kraft method, was esterified with methacrylic anhydride to ensure organic phase homogeneity into the reaction medium. Infrared spectroscopy showed a decrease in the hydroxyl band, a characteristic of natural lignin (3200–3400 cm^?1) and an increase in the characteristic ester band (1720–1740 cm^?1) whereas nuclear magnetic resonance measurements exhibited intense peaks in the range from 1.7 to 2.05 ppm (–CH₃) and 5.4 to 6.2 ppm (=CH₂), related to methacrylic anhydride. Comparatively, the esterified lignin also displayed an increase of its glass transition temperature for 98?°C, related to natural lignin, whose T _g was determined to be equal to 91?°C. Styrene/lignin-based polymers exhibited higher average molar masses in comparison to the values observed for polystyrene synthesized with similar amounts of benzoyl peroxide, due to the ability of lignin to act as a free-radical scavenger. Composites obtained with styrene and natural or esterified lignin were successfully synthesized, presenting regular morphology and proper lignin dispersion. Based on a very simple polymerization system, it is possible to enhance the final properties of polystyrene through the incorporation of lignin, which represents an important platform for developing attractive polymeric materials from renewable resources.     

Sustainable Use of Coffee Husks For Reinforcing Polyethylene Composites

The utilization of the coffee husk fiber (CHF) from the coffee industry as a reinforcing filler in the preparation of a cost-effective thermoplastic based composite was explored in this study. The chemical composition and thermal properties of the CHF were investigated and compared with those of wood fiber (WF). CHF proved to be mainly composed of cellulose, hemicellulose and lignin, and exhibited similar thermal behavior to WF. High density polyethylene (HDPE) composites with CHF loadings of from 40 to 70% were prepared using melt processing and extrusion. The processing properties, mechanical behavior, water absorption and thermal performance of these composites were investigated. The effect of maleated polyethylene (MAPE) used as a coupling agent on the composite was explored. The experimental results showed that increasing the CHF loading in the HDPE matrix resulted in an increase in the modulus and thermal properties of the composites, but resulted in poor water resistance. The addition of a 4% MAPE significantly improved the interfacial behavior of the hydrophilic lignocellulosic fiber and the hydrophobic polymer matrix.