Recycling of Cellulosic Fibers by Enzymatic Process

In this research, enzymatic treatment as an environmental friendly process has been used for recycling process of old cellulosic wastes such as cotton, viscose, and lyocell. Cellulase hydrolyses cellulosic chains and shortens cellulosic fibers. This study investigates to detect the optimum enzyme concentration and time of treatments for suitable changes of length and weight loss. The main purposes of this article are shortening of cellulosic fibers and evaluating of enzymatic treatment in different kind of cellulosic fibers. According to the data of experiments, with the increase of enzyme concentration and the treatment time, the length and weight loss percentage of the cellulosic fibers has been decreased. The length and weight loss percentage of treated viscose is more than that of lyocell and cotton fibers. Optimized condition, reaction time, and enzyme concentration have been determined by mean length of treated cellulosic samples. Suitable longitudinal distribution of fiber for papermaking industries is in the range of 0 to 4 mm. Optimum enzyme concentration and treatment time for recycling cotton, lyocell, and viscose fibers are 2% and 48 h for cotton and lyocell and 0.5% and 48 h for viscose, respectively. According to the data of experiment, the length of treated fibers is appropriate for its usage as a raw material in papermaking industries.     

Isolation and Identification of Residual Chromophores in Cellulosic Materials

A general procedure was developed for the isolation of residual chromophores in or on cellulosic material, which were hitherto inaccessible to structure elucidation due to their extremely low content in the ppb concentration scale. It is applicable to cellulosic pulp, cellulosic fibers (viscose, Lyocell) and cellulose derivatives (acetate, carbonyl-labeled cellulose) as well. The chromophore identification comprises treatment of the cellulosic material with boron trifluoride – acetic acid complex (BF₃*2HOAc) containing sulfite, chromatographic separation of the resulting chromophore-containing mixture, and structure determination of the main constituents by NMR / MS and comparison to authentic samples. Both adsorbed and covalently bound aromatic and quinoid compounds are selectively released by the treatment. Covalent ester, ether and secondary alkyl links between chromophore and cellulose are broken. Two cellulosic example substrates have been analyzed for their chromophore content: Lyocell fibers and non-bleached viscose fibers, and up to eleven chromophores per sample have been identified.     

Preparation and adsorption of novel cellulosic fibers modified by β‐cyclodextrin

Novel cellulosic fibers modified by β‐cyclodextrin (CFEC) were prepared for adsorption for heavy metal ions like copper (II) and organic dye like neutral red from their aqueous solutions. The modified cellulosic fibers gave higher copper ion adsorption, and showed copper ion uptake values of 6.24 mg/g at 293°C, as against no adsorption for unmodified cellulosic fibers. Adsorption isotherm model indicated the adsorption of the novel modified fibers for heavy metal ions best fitted for Langmiur model. The adsorption was an exothermic reaction, and the reaction caloric was 6.295 kJ/mol. Copper ions could form a 7:4 complex with β‐cyclodextrin (β‐CD). The novel modified cellulosic fibers could also form inclusion complexes with neutral red via β‐CD molecules. In addition, it was found that the novel modified cellulosic fibers had nearly the same mechanical and thermal properties as the unmodified cellulosic fibers because the modification did not destroy the main chain of cellulose molecules. Copyright © 2008 John Wiley & Sons, Ltd.     

Graft Copolymerization of Acrylonitrile on Bleached Holocellulose

The mechanism by which ceric ions interact with cellulosic materials in the presence of vinyl monomers to initiate graft copolymer formation is generally believed to involve propagation by radicals generated on the cellulosic substrate [1–5]. However, the relatively high levels of homopolymerization and low efficiencies of grafting associated with graft copolymerization suggest that loci of initiation other than radicals formed on the cellulosic materials may be important in graft copolymerization [6].     

Adsorption and inactivation behavior of horseradish peroxidase on cellulosic fiber surfaces

The physical immobilization behavior of horseradish peroxidase (HRP) on cellulosic fiber surfaces was characterized using adsorption and inactivation isotherms measured by the depletion method followed by fitting of Langmuir’s and Freundlich’s models to the experimental data. The adsorption and inactivation behavior of simpler and relatively non-porous high and low crystalline cellulosic substrates (microcrystalline cellulose and regenerated cellulose) as well as more complex and porous cellulosic pulp fibers (bleached kraft softwood fibers) were investigated. The effect of the sorbent surface energy on HRP adsorption was demonstrated by increasing the hydrophobicity of the cellulosic fibers using an internal sizing agent. The influence of the fiber surface charge density on HRP adsorption was studied via modification of the cellulosic fibers using TEMPO (2,2,6,6-tetramethyl-1-piperidiniloxy radical)-mediated oxidation methods. Results showed that hydrophobic interactions had a much larger effect on HRP adsorption than electrostatic interactions. More hydrophobic fiber surfaces (lower polar surface energy) result in larger enzyme-fiber binding affinity constants and higher binding heterogeneity. It was also found that oxidation of the cellulosic fiber substrate reduces enzyme adsorption affinity but significantly increases the loading capacity per unit weight of the surface.     

Distinct splitting of polymeric cellulosic signals in cashew shell: a TG-diagnosis

Distinct splitting of the cellulosic polymer signal was seen in thermogravimetric analysis of cashew shell (CS). The splitting was more pronounced in CS as compared to cashew shell cake. The splitting of cellulosic polymer peaks was ascribed to cellulosic depolymerization occurring in two phases during thermal degradation of CS. Three protective tissue configurations of CS was considered responsible for this phenomenon. Kinetics were compared by using two model free isoconversional methods, namely the Friedman and Ozawa-Flynn-Wall.     

Cellulose reinforced polymer composites and nanocomposites: a critical review

This review provides a critical assessment of the use of cellulosic materials for reinforcement in polymer composites. The review focuses on structure–property interrelationships and the compatibilization of cellulosic materials for optimal performance of the resulting composite materials. Optimal material and physical properties are characterized on the basis of the reinforcement’s physical dimension and the nature of the interface between reinforcement and matrix. We explore how very different cellulosic materials—bacterial, microcrystalline, microfibrillated or nanocrystalline—can cause distinctly different reinforcment.     

Cellulosic fiber: mechanical fibrillation-morphology-rheology relationships

Cellulose - This study aims to investigate the relationship between mechanical fibrillation, morphological properties, and rheological behavior of cellulosic fiber. Three types of cellulosic fibers...     

RAFT mediated polysaccharide copolymers

Graft copolymers were prepared using the RAFT process via a Z-group approach, where xanthate esters were formed directly on a cellulosic substrate. Grafting of vinyl acetate onto the modified cellulosic materials was then carried out via the reversible addition fragmentation chain transfer (RAFT) process. The xanthate RAFT agents on the backbone of the cellulosic materials were identified by Fourier-transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV-vis). The number average molar masses of the graft copolymers were determined using size exclusion chromatography (SEC) and further characterization was conducted via liquid adsorption chromatography (LAC). The chromatographic results showed that the modified cellulosic materials were successfully grafted with polyvinyl acetate in a controlled manner. Grafted polyvinyl acetate (on the surface) and nongrafted polyvinyl acetate (in the solution) have almost the same molar mass and polydispersity index.     

Physicochemical properties of chemically and enzymatically modified cellulosic surfaces

Surface characteristics of modified cotton fibers have been studied using electrokinetic analysis (EKA), inverse gas chromatography (IGC) and dynamic contact angle (DCA) determinations. Modifications of cotton surfaces included mercerization, water-proofing, cross-linking, dyeing with a bifunctional reactive dye and cellulase biopolishing. Comparisons are made to linen as an example of a natural cellulosic fiber other than cotton and to rayon as a representative of a regenerated cellulosic fiber. Generally all cellulosic surfaces were bipolar with a slightly higher acidic contribution in the case of the cotton samples. EKA indicated ion dissociation as the predominant mechanism for surface charge in aqueous medium for all cellulosic samples, with the exception of greige cotton and the cotton sample with the hydrophobic finish. Results from EKA and IGC showed good correlation, while DCA yielded unreasonably high basic contributions most likely due to fiber swelling.     

Enhancing the inter-fiber bonding properties of cellulosic fibers by increasing different fiber charges

Cellulosic fiber has been increasingly used in many fields. The fiber charge, including the surface charge and inner charge, affects the properties of cellulosic fiber and fiber-based materials significantly. In this study, the cellulosic fiber was subjected to different treatments, including 2,2,6,6-tetramethyl-piperidine-1-oxyl radical-mediated oxidation, carboxymethyl cellulose attachment and mechanical refining, to alter the fiber charge selectively. The effects of the fiber surface charge and inner charge on fiber performances and inter-fiber bonding strength for improving the high-value application of cellulosic fibers, respectively, were discussed. The results showed that the performances of cellulosic fiber can be improved with the increase of either surface or inner fiber charges, including the increased water retention value, flexibility and inter-fiber bonding strength, but with slightly decreased drainability. An increasing bulk fiber charge showed more significant enhancement of the inter-fiber bonding strength than only an increase of the fiber surface charge on cellulosic fiber. This was because the fiber inner charge contributed to the increase of fiber flexibility and deformability, which could benefit the inter-fiber bonding indirectly. As a consequence, the bulk fiber charge enhancement was better for tensile strength improvement of handsheets (fiber-based material) than only fiber surface charge enhancement. Increasing both the surface charge and inner charge improved the tensile strength effectively with less change of the bulky fiber network than the refining treatment.     

纤维素乙醇产业化

由于能发挥缓解能源紧张、减少环境污染、促进农村发展等重要作用,利用年产量巨大的植物纤维资源,生产可再生性液体替代燃料乙醇的技术受到了巨大的关注,成为工业生物技术的研究热点。酶法生产纤维素乙醇面临多种困难:纤维素原料比重轻,收集运输不便;原料结构复杂,需要深度预处理;纤维素酶系的酶解效率有待提高;半纤维素中的木糖难以发酵转化为乙醇等。经过多年研究,新技术已经取得重大进展,开始接近实用化。紧迫的社会需求正在迫使国内外政府和企业界大量投资,开展纤维素乙醇的中试研究和试生产,力求在短时期内克服上述难点,尽快实现产业化。充分利用植物纤维资源中的多种组分,联合生产乙醇和部分高值产品的生物精练技术,是实现纤维素乙醇产业化的重要突破口和必然途径。玉米芯生物精练生产乙醇和木糖相关产品的技术正在进行产业化。本文综述了纤维素乙醇产业化的研究进展并做了展望。     

The fire-retarding effect of inorganic phosphorus compounds on the combustion of cellulosic materials

The pyrolysis and combustion of cellulosic substances treated with MAP and DAP have been studied using thermal analysis, flame spread tests and a specifically designed apparatus for smoldering combustion test. The samples used were: cotton string, cotton fabric and pure cellulose powder. Diammonium Phosphate (DAP) and Monoammonium Phosphate (MAP) can reduce the combustion and pyrolysis maximum mass loss temperature, decrease the initial pyrolysis temperature and considerably increase mass residue. Moreover, MAP and DAP reduce the flaming combustion rate of cellulosic materials and completely inhibit smoldering combustion. This study can facilitate a better understanding of the mechanism of pyrolysis and combustion of fire-retarded cellulosic materials.     

Microwave-Assisted Graft Copolymerization of Cellulosic Fibers for Removal of Heavy Metal Ions from Aqueous Solution

Functional materials obtained from cellulosic biofibers have gained attention due to the growing demand for them in the field of wastewater remediation. In view of the technological significance of functionalized cellulosic biofibers in wastewater treatment, the present study is a green approach to functionalized cellulosic fibers through graft copolymerization under microwave irradiation. The grafted cellulosic polymers were subsequently subjected to heavy metal ion adsorption studies in order to assess their application in wastewater remediation. The effects of pH, contact time, temperature, and metal ion concentration were studied in batchwise adsorption experiments. The Langmuir, Freundlich, and Tempkin models were used to show the adsorption isotherms. The maximum monolayer capacities, q _m. calculated using the Langmuir isotherm for Zn²⁺, Cd²⁺, and Pb²⁺ were found to be 37.79, 69.68, and 96.81 mg/g respectively. The thermodynamic parameter ΔH° and ΔG° values for metal ion adsorption on functionalized cellulosic fibers showed that adsorption process was spontaneous as well as exothermic in nature.     

The Effect of Magnesium Chloride Hydrate on the Fire Retardation of Cellulosic Fibers

Thermal analysis was used to investigate the effect of the addition of magnesium chloride hexahydrate as a fire retardant to cellulosic fibers. The kinetics of the decomposition of the cellulosic material were first studied. The decomposition of the dry salt was also investigated and three steps disclosed. Then, the fabrics were impregnated into salt solutions of different concentrations and the loss in mass was followed by thermal analysis. The percent loss in mass was compared to that of pure cellulosic fabric at different temperatures. It was found that there is an appreciable improvement in fire retardation at a minimum percent add-on of the salt of 35%. This revised version was published online in August 2006 with corrections to the Cover Date.     

High Yielding Acid-Catalysed Hydrolysis of Cellulosic Polysaccharides and Native Biomass into Low Molecular Weight Sugars in Mixed Ionic Liquid Systems

Ionic media comprising 1-butyl-3-methylimidazolium chloride and the acidic deep eutectic solvent choline chloride/oxalic acid as co-solvent-catalyst, very efficiently convert various cellulosic substrates, including native cellulosic biomass, into water-soluble carbohydrates. The optimum reaction systems yield a narrow range of low molecular weight carbohydrates directly from cellulose, lignocellulose, or algal saccharides, in high yields and selectivities up to 98 %. Cellulose possesses significant potential as a renewable platform from which to generate large volumes of green replacements to many petrochemical products. Within this goal, the production of low molecular weight saccharides from cellulosic substances is the key to success. Native cellulose and lignocellulosic feedstocks are less accessible for such transformations and depolymerisation of polysaccharides remains a primary challenge to be overcome. In this study, we identify the catalytic activity associated with selected deep eutectic solvents that favours the hydrolysis of polysaccharides and develop reaction conditions to improve the outcomes of desirable low molecular weight sugars. We successfully apply the chemistry to raw bulk, non-pretreated cellulosic substances.     

Photooxidative degradation of cellulose: Reactions of the cellulosic free radicals with oxygen

Photooxidative degradation of cellulose resulted in decreases of degree of polymerization (DP) and α-cellulose content, concurrently producing chromophoric groups; namely, carbonyl, carboxyl, and hydroperoxide groups within the polymer. Electron spin resonance (ESR) studies revealed that cellulosic carbon free radicals readily reacted with oxygen molecules at 143–160 K to produce peroxy radicals, whereas cellulosic oxygen free radicals were inert toward oxygen molecules throughout the photooxygenation reactions. At 77 K it is feasible that only photoexcited oxygen molecules reacted with cellulosic carbon free radicals to produce peroxide radicals. These radicals were themselves stabilized at 273 K by abstraction of hydrogen atoms from cellulose to produce polymer hydroperoxides. Simultaneously, new radical sites, which exhibited three-line ESR spectra, were generated in cellulose.     

Conductivity and flame retardancy of polyaniline-deposited functional cellulosic paper doped with organic sulfonic acids

Two kinds of organic sulfonic acids, i.e., p-toluenesulfonic acid (PTSA) and sulfosalicylic acid (SSA), were used as doping acid to prepare the polyaniline-deposited functional cellulosic paper, and both the conductivity and flame retardancy of the functional cellulosic paper were investigated. The results indicated that both the conductivity and the flame retardancy of the paper composite had a close relationship with the incorporation of doping acid. Both the conductivity and the oxygen index (OI) value increased with the increase of the acid concentration. SSA performed much better than PTSA and the inorganic acids studied previously for both the conductivity and the OI value of functional cellulosic paper. The conductivity of the paper doped with SSA was more stable than that of the paper doped with PTSA, and the OI value only decreased about 1 % within 40 days for the functional cellulosic paper doped with the two doping acids. Compared with the polyaniline-deposited paper doped with PTSA, both the much higher doping level and the much smaller and more compact polyaniline particles deposition were probably responsible for the significantly better conductivity and flame retardancy of the polyaniline-deposited paper doped with SSA.     

Industrial Sustainability of Competing Wood Energy Options in Canada

The amount of sawmill residue available in Canada to support the emerging cellulosic ethanol industry was examined. A material flow analysis technique was employed to determine the amount of sawmill residue that could possibly be available to the ethanol industry per annum. A combination of two key trends—improved efficiency of lumber recovery and increased uptake of sawmill residues for self-generation and for wood pellet production—have contributed to a declining trend of sawmill residue availability. Approximately 2.3 × 10⁶ bone-dry tonnes per year of sawmill residue was estimated to be potentially available to the cellulosic ethanol industry in Canada, yielding 350 million liters per year of cellulosic ethanol using best practices. An additional 2.7 billion liters of cellulosic ethanol might be generated from sawmill residue that is currently used for competing wood energy purposes, including wood pellet generation. Continued competition between bioenergy options will reduce the industrial sustainability of the forest industry. Recommendations for policy reforms towards improved industrial sustainability practices are provided.     

Production of highly electro-conductive cellulosic paper via surface coating of carbon nanotube/graphene oxide nanocomposites using nanocrystalline cellulose as a binder

Electro-conductive cellulosic paper has attracted great attention as a promising alternative material in the emerging field of flexible and portable electronic devices. However, the environmentally friendly fabrication of electro-conductive cellulosic paper still remains challenging. Herein, green multi-walled carbon nanotube (MWCNT)/graphene oxide (GO) nanocomposites towards the sustainable development strategy were developed and subsequently used to impart electro-conductivity to cellulosic paper via surface coating process. GO exfoliated from graphite powder was used as a dispersant to improve the dispersion of MWCNTs in water media, and nanocrystalline cellulose (NCC) derived from cotton fibers was employed as a binder for the MWCNT/GO nanocomposites. Effect of NCC amount on the rheological behavior, particle size distribution, sedimentation stability and zeta potential of MWCNT/GO nanocomposites as well as the electro-conductivity and mechanical properties of coated paper was investigated. Results demonstrated that NCC enhanced the dispersion of MWCNT/GO nanocomposites in addition to serving as a binder. Surface coating application of MWCNT/GO nanocomposites was found to impart high electro-conductivity of up to 892 S m^?1 to the cellulosic paper while improving its mechanical properties.