Isolation of highly purity cellulose from wheat straw using a modified aqueous biphasic system

Cellulose samples with molecular weights ranging from 8.39 × 10⁴ to 11.00 × 10⁴ g/mol were obtained from wheat straw. The dewaxed wheat straw was pretreated with aqueous hydrochloric acid followed by delignification using an environmentally benign poly(ethyleneglycol)/salt aqueous biphasic system. The yield of cellulose was in the range of 48.9%–55.5% and the cellulose contained 1.2%–3.2% hemicelluloses, and 0.97%–3.47% lignin. All the isolated cellulose samples could be directly dissolved in a 6 wt-% NaOH/4 wt-% urea aqueous solution through a precooling-thawing process to form a homogenous solution. The separation process was investigated and the obtained cellulose and its solution were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray apparatus, and X-ray diffraction. The results revealed that aqueous soluble cellulose can be directly prepared from wheat straw by this method and this study opens a novel pathway to prepare cellulosic materials from agricultural waste.     

Beyond waste: Transforming wheat straw into oxygen and UV-resistant cellulose films

Regenerated cellulose membrane is a biomaterial obtained by activating, dissolving, solidifying, and regenerating cellulose powder using solvents of different polarities. It has the characteristics of high oxygen resistance and high strength. However, its low water vapor barrier and single function limit its application. In order to improve the water resistance of regenerated cellulose membranes and endow them with UV resistance, lignin was extracted from waste wheat straw using formic acid method. The extracted formic acid lignin (FAL) was added to the cellulose solution to prepare a series of regenerated lignocellulosic membranes (RC-FAL) with different lignin contents. The results indicate that lignin can not only improve the water vapor barrier, tensile strength, and water resistance of the film, but also enhance the oxygen barrier and UV absorption of the film. Compared with pure cellulose film, the contact angle of lignocellulose film can be increased by 66.2%, the UV absorption rate can reach 100%, and the oxygen transmission coefficient has no significant effect. In this paper, a new kind of biological packaging material with high oxygen resistance, strong ultraviolet absorption, and water resistance was prepared by recycling waste wheat straw, it has a broad application prospect in the industrial production of packaging materials.     

Fractionnement de deux bois tropicaux (eucalyptus et wapa) par traitement thermomécanique en phase aqueuse. Partie I: Conversion et profils de solubilisation

The conversion and solubilization profiles of two species of tropical woods have been studied via an aqueous phase thermo-mechanical treatment. An aqueous wood suspension having a consistency of 8% solids is preheated (digestion at 135°C) and caused to flow through a capillary at speeds between 50 and 115 m/s. At the exit of the capillary, a flash decompression facilitates disaggregation of the hemicelluloses–lignin–cellulose complex. The separation of hemicelluloses and lignin has been studied as a function of the treatment severity (150–230°C). The results presented lead to the conclusion that a selective and sequential fractionation of the compound lamella lignin and the hemicelluloses is possible for the tropical species studied. The optimum operational conditions are discussed based on the experimental observations.     

Comparative study of cellulose isolated by totally chlorine‐free method from wood and cereal straw

Highly purified cellulose preparations were obtained by pretreatment of dewaxed barley straw, oil palm frond fiber, poplar wood, maize stems, wheat straw, rice straw, and rye straw with 2.0% H₂O₂ at 45°C and pH 11.6 for 16 h, and sequential purification with 80% acetic acid–70% nitric acid (10/1, v/v) at 120°C for 15 min. The purified cellulose obtained was relatively free of bound hemicelluloses (2.3–3.2%) and lignin (0.4–0.6%) and had a yield of 35.5% from barley straw, 39.6% from oil palm frond fiber, 40.8% from poplar wood, 36.0% from maize stems, 34.1% from wheat straw, 23.4% from rice straw, and 35.8% from rye straw. The weight‐average molecular weights of the purified cellulose ranged from 39,030 to 48,380 g/mol. The thermal stability of the purified cellulose was higher than that of the corresponding crude cellulose. In comparison, the isolated crude and purified cellulose samples were also studied by Fourier transform IR and cross‐polarization/magic‐angle spinning ¹³C‐NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 322–335, 2005     

Valorization of residual woody biomass (Olea europaea trimmings) based on aqueous fractionation

BACKGROUND: Olive tree trimmings, a widely available agricultural residue lacking added value applications, were subjected to treatments with hot, compressed water under a variety of operational conditions. As a result of treatments, hemicelluloses were solubilized, and the treated solids were enriched in cellulose and lignin. Spent solids from autohydrolysis were assayed as substrates for enzymatic hydrolysis and for bioethanol production by simultaneous saccharification and fermentation. RESULTS: Liquors from the aqueous fractionation stage resulted in the formation of soluble hemicellulose‐derived saccharides (mainly of oligomeric nature) at yields up to 26.2 g per 100 g oven‐dry raw material. Enzymatic hydrolysis of spent solids from the aqueous fractionation step led to solutions containing up to 58.8 g glucose L^?1 (corresponding to cellulose to glucose conversions up to 83.2%). Simultaneous saccharification and fermentation assays using spent solids as substrates enabled the production of media containing up to 38.2 g ethanol L^?1, corresponding to 72% of the stoichiometric amount. CONCLUSION: Aqueous (or hydrothermal) processing is a technology enabling the recovery of hemicelluloses (as soluble saccharides) and the production of spent solids with high susceptibility to enzymatic hydrolysis (suitable for bioethanol production by simultaneous saccharification and fermentation). Copyright © 2011 Society of Chemical Industry     

新型橡胶助剂——高沸醇木质素的研制

采用1,4 丁二醇水溶液为溶剂的高沸醇溶剂法,从松木、稻草等原料制备纤维素与高沸醇木质素。使用上述原料,在190～220℃的1,4 丁二醇水溶液中蒸煮1～3h后,分离反应产物,得到固体纤维素与高沸醇木质素-丁二醇溶液。不溶于水的高沸醇木质素通过加水沉淀的方法,从反应后的液体混合物中分离。从松木和稻草制备沸醇木质素的得率分别大于25%和11%。从松木中提取的沸醇木质素的w(灰分)=0 6%,而传统造纸黑液制得木质素磺酸钙的w(灰分)=21 4%。沸醇溶剂法是一种节能、无污染的制备纤维素与木质素的好方法。高沸醇木质素具有较高的反应活性,可以与甲醛反应,形成木质素改性树脂。添加高沸醇木质素改性树脂可以改善NBR橡胶的性能,尤其是扯断伸长率从270%提高到540%,其改性效果优于木质素磺酸盐改性树脂(扯断伸长率330%)。沸醇木质素是一种新型的橡胶添加剂,有良好的应用前景。     

Adsorption removal of Cu2+ and Ni2+ from waste water using nano‐cellulose hybrids containing reactive polyhedral oligomeric silsesquioxanes

Cellulose is an important biomass in natural material fields. Reactive polyhedral oligomeric silsesquioxane (R‐POSS) bearing multi‐N‐methylol groups is novel high reactive POSS monomer. The nano‐cellulose hybrids containing R‐POSS were synthesized by crosslinking reaction. It was interesting to investigate properties and applications of hybrids containing R‐POSS. In this work, nano‐cellulose hybrids as novel biosorbent were used for adsorpting copper and nickel ions in aqueous solution. Adsorption kinetics and equilibrium isotherm of Cu²⁺ and Ni²⁺ on the nano‐cellulose hybrids were investigated. The results showed that R‐POSS had been grafted to cellulose macromolecule. The nano‐cellulose hybrids could form new adsorptive position for heavy metal ions. The adsorption capacities of hybrid materials were obviously higher than that of control cellulose. The adsorption of heavy metal ions on nano‐cellulose hybrids followed the second‐order model. The equilibrium isotherms for adsorpting copper and nickel ions on the hybrids followed Langmuir isotherm model. Nano‐cellulose materials containing POSS as biosorbents or ultrafiltration membranes would be used in separation of toxic heavy metal ions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

农业秸秆半纤维素分离及纯化技术研究进展

我国是农业大国,每年有大量的农业秸秆没有完全充分利用。农业秸秆中半纤维素含量一般在28%～35%之间。在秸秆细胞壁中,半纤维素与木质素之间有化学键的联接,与纤维素之间有氢键的联接,因此限制了半纤维素从细胞壁中的分离。分离半纤维素的技术有化学法、机械法与化学法相结合、热处理法、膜分离等,但到目前为止还没有一种分离技术能够较完整地将半纤维素从植物细胞壁中分离出来。文章综述近年来农业秸秆半纤维素的分离技术,并提出了存在的主要问题。     

Adsorption of copper(II) and chromium(III) ions onto amidoximated cellulose

Chemical modification of cellulose powder is performed by successive reactions with acrylonitrile in an alkaline medium followed by aqueous hydroxylamine to prepare amidoximated cellulose. Due to complexation, the amidoxime groups immobilize heavy cations from buffered solutions at various pH values. The capacity of adsorption for Cu(II) and Cr(III) ions is related to the amount of amidoxime groups in the support and to the metal concentration of the polluted solution. The formation of a 1/1 complex is proved by the adsorption limit values. Desorption of the cations is possible by treatment with a stronger complexing agent such as ethylenediaminetetracetic acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1624–1631, 2000     

Composition of the cell wall in the stem and leaf sheath of wheat straw

The composition of the cell wall of the stem and leaf sheath of extracted wheat straw was studied with X‐ray photoelectron spectroscopy and with a field emission scanning electron microscope equipped with an energy‐dispersive microanalysis system. The outer side (epidermal side) had more lignin, and the inner side (lumen side) of the stem was rich in cellulose. The compositions of the two sides of the leaf sheath were a little different. The chemical components for the same tissue at different growth stages were essentially constant, and this indicated that cellulose, lignin, and hemicelluloses deposited in constant proportions in the cell wall of the same tissue during growth. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1236–1240, 2007     

Removal of Hexavalent Chromium by Different Modified Spruce Bark Adsorbents

In this work, spruce bark was used as a raw material to remove Cr(VI) ions from aqueous solutions. Three kinds of chemically modified bark adsorbents were prepared by treatment with formaldehyde (FB), dilute sulfuric acid (AB), and concentrated sulfuric acid (CB), respectively. The chemical modifications mainly changed the relative lignin content in the bark. Lower pH facilitated the adsorption of Cr(VI) ions because reduction of Cr(VI) ions to Cr(III) ions occurred during the adsorption process which consumed a large amount of H⁺ ions. Higher temperature accelerated the adsorption process, owing to the endothermic nature of the redox reaction. At initial solution pH around 1, the adsorption capacities of Cr(VI) ions on FB, AB, and CB were as high as 423, 503, and 759 mg/g, respectively, which were much higher than the reported adsorption capacities by other agricultural and forest biosorbents in the literatures. XPS analysis revealed the adsorption mechanism was adsorption-coupled reduction involving the electron-donor groups of lignin moieties.     

Poly(hydroxamic acid) ligand from palm-based waste materials for removal of heavy metals from electroplating wastewater

Heavy metals pollutants are nonbiodegradable and their bioaccumulation results in detrimental environmental consequences. Therefore, it is important to effectively remove toxic heavy metal waste from industrial sewage. Thus, the main goal of this research is to synthesize an ideal cellulose-based adsorbent from palm-based waste materials (agro waste) in order to be utilized in real-life practical applications with low cost as such removing common toxic heavy metals from industrial effluents. A poly(methyl acrylate) grafted palm cellulose was synthesized via a free-radical initiation process, followed by an oximation reaction to yield poly(hydroxamic acid) ligands. The adsorption capacity (q_e) of poly(hydroxamic acid) ligands for metal ions such as copper (Cu²⁺), iron (Fe³⁺), and lead (Pb²⁺) were 325, 220, and 300 mg g⁻¹, respectively at pH 6. In addition, the X-ray photoelectron spectrometry results are to be proved the binding of metal ions, for instance, Cu(II) ions showed typically significant BEs of 932.7 and 952.0 eV corresponding to the Cu2p3/2 and Cu2p1/2 species. The heavy metal ions adsorption followed a pseudo-first-order kinetic model pathway. The adsorption capacity (q_m) is also derived from the Langmuir isotherm linear plot, which does not showed good correction coefficients. However, the results were correlated to the Freundlich isotherm model, where the R² value showed significance (>0.98), indicating that multiple layer adsorption occurs on the synthesized ligand. The synthesized polymeric ligand is an excellent adsorbent for the removal of heavy metals from the industrial wastewater. In addition, the metal analysis results showed that about 98% removal of copper and iron ions from electroplating wastewater including lead, nickel, and chromium can be removed up to 85–97%.     

废水重金属的生物吸附研究进展

生物吸附法是目前处理重金属废水的一种行之有效的方法,特别是对于低浓度废水,其优势明显,还可达到以废治废的目的。对废水重金属的生物吸附进行了综述,详细介绍了目前最具代表性的四种生物吸附机理以及已经开发出来的五种吸附工艺,同时还探讨了影响生物吸附重金属的多种因素和生物吸附剂的类型,展望了生物吸附废水中重金属在工业生产中的应用前景。     

Fractional Separation and Structural Characterization of Chlorophyll and Lignin from Perennial Ryegrass (L. perenne) and Cocksfoot Grass (D. glomerata)

Abstract

One chlorophyll rich fraction and two lignin preparations were separated from perennial grass and cocksfoot grass by sequential three‐stage treatments with 80% ethanol containing 0.2% NaOH, 2.5% H₂O₂?0.2% EDTA containing 1.5% NaOH, and 2.5% H₂O₂?0.2% TAED containing 1.0% NaOH at 75°C for 3 h, respectively, which released 4.6 and 3.6% chlorophyll rich fraction, 2.3 and 5.8%, and 0.9 and 1.0% lignin preparations, except for releasing 8.0 and 10.4%, 79.1 and 77.0%, and 12.9 and 12.5% of the original hemicelluloses, respectively. The lignin fractions obtained from the two different grasses had very similar molecular weights and structural composition. The NMR spectra of the lignin preparations revealed the presence of p‐hydroxyphenyl, guaiacyl, and syringyl structures, and the lignin in chlorophyll rich fraction contained more guaiacyl and syringyl units than p‐hydroxyphenyl unit, whereas the reverse trend was found in the two lignin preparations. The lignin preparations are distinguished with straw and wood lignins by relatively higher contents of p‐hydroxyphenyl unit and lower amounts of condensed units (β‐5 and 5‐5′) and resinol units (β‐β). This difference in distribution of structural units indicated some structural heterogeneity between grass and straw/or wood lignin.     

Elucidation of the interaction among cellulose,xylan, and lignin in steam gasification of woody biomass

The reaction mechanism for gas and tar evolution in the steam gasification of cellulose, lignin, xylan, and real biomass (pulverized eucalyptus) was investigated with a continuous cross‐flow moving bed type differential reactor, in which tar and gases can be fractionated according to reaction time. In the steam gasification of real biomass, the evolution rates of water‐soluble tar (derived from cellulose and hemicelluloses) and water‐insoluble tar (derived from lignin) decrease with increasing reaction time. It was found that the evolution of water‐soluble tar occurs earlier than in the gasification of pure cellulose, indicating an interaction of the three components. The predicted yield of water‐insoluble tar is substantially less than that of real biomass. This implies that the evolution of tar from the lignin component of biomass is enhanced, compared with pure lignin gasification, by other components. The gas evolution rate from real biomass is similar to that predicted by the superposition of cellulose, lignin, and xylan. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

Development of a fixed‐bed column with cellulose/chitin beads to remove heavy‐metal ions

Environmental friendly cellulose/chitin beads, having relatively high mechanical properties, were successfully prepared from a blend of cellulose and chitin in 6 wt % NaOH/5 wt % thiourea aqueous solution by coagulating with 5% H₂SO₄ aqueous solution. The ability of the beads to adsorb Pb²⁺ in an aqueous solution was measured with a fixed‐bed column. The effects of important parameters, to design an adsorption column of the cellulose/chitin beads for fixed‐bed columns, were investigated. The breakthrough curves for the adsorption behavior indicated that the column performance was improved with decreasing initial lead concentration, ionic strength, flow velocity or bead size, as well as increasing pH dependence and bed height. Column studies showed that constants, calculated from the experimental data, and the Bed Depth Service Time (BDST) model had a good correlation. The columns were easily regenerated by treating with 0.1 mol/L HCl aqueous solution after the adsorption of metals, providing a simple and economical method for removal and recovery of heavy metals. After four adsorption–desorption cycles, the efficiency of column for the removal of lead was not significantly reduced (not more than 5%). It is shown that heavy‐metal biosorption processes in fixed‐bed columns could give a broad range of potential industrial applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 684–691, 2004     

Preparation,characterization, and behavior of cellulose–titanium(IV) oxide modified with organosilicone

Cellulose–titanium(IV) oxide modified with organosilicone (CTSN) was prepared by a reaction of cellulose powder with titanic chloride, followed by a reaction with 4‐aza‐6‐aminohexyl triethoxysilane, and was characterized by infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis. An SEM image of titanium(IV) oxide‐coated cellulose and a Ti mapping image showed that titanium oxide was well dispersed on the cellulose surface. Titanium and silicon mapping images of CTSN, obtained with SEM, indicated that both oxides were uniformly dispersed on the cellulose surface. The atomic ratio of Ti to Si was obtained with X‐ray energy spectral composition analysis. The adsorption behavior of CTSN toward Hg(II), Cu(II), Pb(II), Fe(III), and Cr(III) ions in aqueous solutions was determined. The adsorption behavior of CTSN toward human serum protein was preliminarily examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 61–66, 2002; DOI 10.1002/app.10188     

蔗渣纤维组分的常压一步分离

蔗渣纤维组分的分离是实现其综合利用的关键,对蔗渣纤维组分进行了常压一步分离研究。采用溶剂-酸-水体系分离工艺,响应面法优化最佳工艺条件。结果表明,溶剂浓度69.63%(体积分数)、酸浓度(体积分数)6.41%、反应时间4h,蔗渣半纤维素分离率为98.07%、木质素分离率为66.72%、纤维素得率为92.49%,验证试验半纤维素分离率99%、木质素分离率67.06%、纤维素得率92.08%,分离条件可靠、分离结果较理想。最佳分离工艺条件下木糖得率90.01%,木质素回收率62.15%、分离的生物质总的可利用率71.53%。     

Tetrahydrofurfuryl Alcohol (THFA) Pulping of Rice Straw

Abstract

A 80–95% solution of tetrahydrofurfuryl alcohol (THFA) added with 0.15–0.5% catalytic hydrochloric acid (HCl) was used to pulp rice straw. The pulping conditions applied for organosolv digestions of the straw at atmospheric pressure and 120°C cooking for 4 h. The characteristics of the digestion, chemical properties of the resulting pulp, and the handsheet physical properties were evaluated. As for the pulp yields, the method has high delignification specificity, at kappa number 20, the yield was ca. 60%, about 15–20% higher than the traditional alkaline pulping method. Furthermore, with increasing THFA concentrations, efficacies of delignification also increased. Increasing the catalyst dosage also caused an increase in delignification. Delignification rate of 120°C cooking are not so appreciable, but high yield were retained. If cooking temperatures were increased to 130 and 150°C, although even higher delignification rates were achievable, the yield decreased as well. During the cooking the dissolution of carbohydrate was low, at most 23%, consisting of mostly hemicelluloses, which was as high as 78% of the dissolved carbohydrates. The optimal conditions of the THFA/HCl cooking applied 95% THFA, 0.50% HCl, temperature of 120°C, and cooking time of 240 min. Residue lignin in the resulting pulp was low, and can be bleached to high brightness easily with a conventional bleaching sequence. If, however, energy and operation efficiency was a primary consideration, then a procedural heating scheme could be employed. The physical properties of the THFA pulp handsheets were inferior to those of the kraft pulp. The main reason was the damage to cellulose sustained during the acidic cooking condition.     

Miscanthus sinensis fractionation by different reagents

Miscanthus sinensis L. was fractionated by different reagents (ethanol, soda and soda–ethanol) in order to obtain cellulose, hemicelluloses and lignin. Characterization of original M. sinensis fibres (66.6% holocellulose, 36.1% α-cellulose, and 15.5% lignin) was done and compared with other biomass species chemical composition (alternative raw materials, agriculture residues, coniferous and leafy plants). Obtained solid fractions were chemically characterized and compared with solid fractions from other biomass products (palm oil empty fruit bunches (EFB) and rice straw) generated by similar fractionation processes (soda and organosolv). Soda process produced the solid fraction with the highest content in α-cellulose and lowest content in lignin revealing a strong fractionation effect. On the contrary, soda–ethanol process was found to present low fractionation capability. Obtained cellulose samples were characterized by FTIR to complete the chemical structure analysis. Lignin samples isolated from the liquid fractions were submitted to FTIR, ¹H NMR, GPC, DSC and TGA in order to suggest suitable applications for the products based on their properties.