Wheat Straw Pulp Research Articles

Ultrasonic-assisted Method of Graphite Preparation from Wheat Straw

Graphite production was achieved unexpectedly in the course of demonstrating a new ultrasonic-assisted wheat straw pulping method at room temperature and at atmospheric pressure. The graphite material was found in the ultrasonic-assisted pulp (UP) ash, as shown by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and TEM analysis. UP ash contained both inorganic and organic components. The total content of inorganic components in the ash was 81.9%, while the content of organic component (graphite material) was 18.1%. The graphite content in the pulp was calculated to be approximately 4.5%. This work describes a new meaningful approach for the facile preparation of graphite materials. The graphitization was based on the ultrasonic cavitation mechanism of extreme condition, while the process would be divided into three steps, degradation of lignin, graphene formation, and graphitization process.

The promotional effect of water-soluble extractives on the enzymatic cellulose hydrolysis of pretreated wheat straw

Enzymatic cellulose hydrolysis of pretreated wheat straw pulp to glucose is enhanced when the hydrolysis is performed in the presence of an aqueous extract of the wheat straw. A relative digestibility increase of about 10% has been observed for organosolv, alkaline and dilute acid pretreated wheat straw pulp (enzyme dose 2.5FPU/g pulp). At lower enzyme doses, the extract effect increases leading to an enzyme dose reduction of 40% to obtain a glucose yield of 75% within 48h using organosolv wheat straw pulp. Possibly, cellulase deactivation by irreversible binding to pulp lignin is reduced by competition with proteins in the extract. However, since the extract effect has also been demonstrated for lignin-lean substrates, other effects like improved accessibility of the pulp cellulose (amorphogenesis) cannot be excluded. Overall, this contribution demonstrates the positive effect of biomass extractives on enzymatic cellulose digestibility, thereby reducing costs for 2G biofuels and bio-based chemicals.

Sulfite-Formaldehyde Pulping and Oxygen Delignification of Wheat Straw

Sulfite-Formaldehyde Pulping and Oxygen Delignification of Wheat Straw

Preparation and Characterization of Hydrophobic Non-Crystal Microporous Starch (NCMS) and its Application in Food Wrapper Paper as a Sizing Agent

Non-crystal microporous starch (NCMS) containing microporous and amorphous structures was prepared from native corn starch by heat treatment and solvent exchange. NCMS can be used as fillers, coatings, and raw materials in the preparation of various denatured starch because of its specific surface area and amorphous region. However, the hydrophilicity of NCMS limits its applications in papermaking. Thus, in this study, NCMS was reacted with alkyl ketene dimer (AKD) to prepare hydrophobic NCMS (H–NCMS), which is more stable, and convenient for storage and use in surface sizing. The optimal preparation conditions were selected using single-factor tests. The product, which was prepared at 55 °C for 3 h with an AKD dosage of 80%, had a sizing degree of 67 s. Characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy confirmed that NCMS, H–NCMS, and sized paper were obtained. The thermal stability and hydrophobicity of the paper were measured using thermogravimetric analysis (TGA) and water contact angles, respectively. The results indicated that the sized paper has excellent thermal stability and hydrophobicity after surface sizing with 0.9% H–NCMS. Food wrapping paper with excellent strength and hydrophobicity was successfully prepared using H–NCMS and ultrasonic-assisted wheat straw pulp (UWP).

Modification of Different Pulps by Homologous Overexpression Alkali-Tolerant Endoglucanase in Bacillus subtilis Y106

Cellulase (mainly endoglucanase, EG) has been used in pulp modification for improving paper quality through environmentally friendly process. But low activity in alkaline pH and high filter paper activity (FPA) were still obstacles for extending the cellulase application in papermaking industry. In the study, an alkali-tolerant EG gene of Bacillus subtilis Y106 was homologous over-expressed for obtaining suitable enzyme used in pulp modification. The engineering strain could produce the crude enzyme with more alkali-tolerant EG and little PFA. Potential of the crude enzyme in modification of different pulps were investigated. It was found that the enzyme could be used for improving drainage and strength properties of pulps from softwood, hardwood and non-wood materials, especially non-wood pulp such as wheat straw pulp. The underlying mechanisms of pulp modification and different effects on various types of pulps by the EG treatment were also discussed by studying the change in fibers characteristics and fiber bonding.

Novel Medium-density Fibreboard Produced by Ultrasonic-assisted Pulp with Superhydrophobic and Flame-Resistant Properties

A novel medium-density fibreboard produced by an ultrasonic-assisted wheat straw pulp (UWP) was obtained without adhesives. It was then coated with a superhydrophobic sol solution integrated with an in vitro addition of two fire retardants (polyhedral methyl-silsesquioxane and ammonium polyphosphate) during the process of sol-gel reaction involving the two silane precursors tetraethyl orthosilicate (TEOS) and tridecafluorooctyltriethoxysilane (FAS). The coated UWP medium-density fibreboard (UPB) had good strength properties and possessed excellent hydrophobicity (water contact angle (WCA) above 150°), and flame-resistant properties (limiting oxygen index (LOI) improved by 5% compared with the original sample with a LOI of 18%). Meanwhile, the fibreboard also exhibited outstanding anti-permeability towards water (kept constant WCA for more than 1 h).

An integrated process to produce bio-ethanol and xylooligosaccharides rich in xylobiose and xylotriose from high ash content waste wheat straw

A bio-refinery process of wheat straw pulping solid residue (waste wheat straw, WWS) was established by combining prewashing and liquid hot water pretreatment (LHWP). The results showed that employing a prewashing step prior to the LHWP remarkably improved enzymatic glucose yields from 39.7% to 76.6%. Moreover, after 96h simultaneous saccharification and fermentation (SSF), identical ethanol yields of 0.41g/g-cellulose were obtained despite varied solid loadings (5–30%). Beyond ethanol, enzymatic post-hydrolysis of the prehydrolyzate effectively increased xylobiose and xylotriose yields from 15mg/g-WWS and 14mg/g-WWS to 53mg/g-WWS and 20mg/g-WWS, respectively. For mass balance, about 10.9tons raw WWS will be consumed to produce 1ton ethanol, in addition to producing 614.8kg xylooligosaccharides (XOS) containing 334.3kg xylobiose and 124.8kg xylotriose. The results demonstrated that the integrated process for the WWS bio-refinery is promising, based on value-adding co-production in addition to robust ethanol yields.

Conversion of various types of lignocellulosic biomass to fermentable sugars using kraft pulping and enzymatic hydrolysis

The aim of this work was to assess the utility of seven different kraft pulps produced from softwood (pine), hardwood (poplar, birch and beech), wheat straw and hemp (bast and harl) as potential sources of sugar feedstocks for fermentation processes. The pulps contained low amounts of hemicelluloses (1.9–8.2% d.w.) and lignin (1.7–15% d.w.). The crystallinity index values ranged from 55% (wheat straw pulp) to 79% (hemp bast pulp), while the average DP varied from around 230 (hemp bast pulp) to 1482 (poplar and birch pulps). The results of enzymatic hydrolysis showed that not only the residual lignin content but also the cellulose crystallinity index decided on the sugar yields while the average polymerization degree had a weak impact. More reducing sugars were obtained from the hardwood pulps and wheat straw pulp (100% d.w.) than from the pine pulp (around 89% d.w.) and two hemp pulps (40.5% d.w. and 44.7% d.w. from the bast and harl pulps, respectively). Glucose was the dominating (69–79% w/w) soluble sugar in enzymatic hydrolysates of the pulps. The sugar profiles of these hydrolysates make them suitable sugar feedstocks for fermentation processes.

Utility of co-expressed alkali-tolerant endoglucanase and xylanase in ameliorating wheat straw chemical pulp properties

Because of the inferior properties of wheat straw pulp compared with wood pulp, wheat straw pulp needs to be ameliorated to meet the requirements of high-grade paper production. Enzymatic treatment with cellulase and/or xylanase is recognized as an environmentally friendly and effective method for pulp modification; however, an improper enzyme system and low enzyme activity in alkaline pH are still the main obstacles to the industrial application of the enzymes. In this study, we co-expressed alkali-tolerant endoglucanase (EG) and xylanase in Bacillus subtilis Y106-WT and successfully produced alkali-tolerant enzymes that simultaneously contained high EG and xylanase activity, but little FPA and cellobiohydrolase (CBH) activity, i.e., the activities of EG, xylanase, FPA and CBH of the crude enzyme from the fermentation liquor were 8.20, 60.40, 0.12 and 0.02 IU/ml, respectively, after 64 h of fermentation. Compared to the control, the pulp brightness, breaking length, burst index and tear index of wheat straw chemical pulp increased by 2.0% ISO, 8.7%, 16.6% and 9.3%, respectively, and the beating degree decreased by 15% after treatment using the recombinant enzyme with 0.20 IU/ml EG and 1.5 IU/ml xylanase. The synergistic effect between endoglucanase and xylanase occurred during the enzymatic treatment. The possible mechanism of pulp modification was also discussed.

Research on Wheat Straw Pulping with Ionic Liquid 1-Ethyl-3-Methylimidazole Bromide

Research on Wheat Straw Pulping with Ionic Liquid 1-Ethyl-3-Methylimidazole Bromide

The Properties and Application of an Ultrasonic-Assisted Wheat Straw Pulp having Enhanced Tendency for Ash Formation

Ultrasonic-assisted pulping technology integrates pulping and bleaching processes in one reactor with good yields performance of approximately 60% to 70%. The properties of ultrasonic-assisted wheat straw pulp were compared, i.e., composition, strength, and whiteness, with those of other conventionally pulps. The ash content of ultrasonic wheat straw pulp (the content is 27.81%) was much higher than that of traditional wheat straw pulp (the content was approximately 15%). Upon comparison with the ash content of the raw material, X-ray diffraction analysis, and thermogravimetry, the authors believe that some heat-resistant material was produced during the ultrasonic pulping process. The strength and whiteness performance of ultrasonic wheat straw pulp was better than that of traditional wheat straw pulp and was close to that of reed soda-anthraquinone (soda-AQ) pulp. Offset paper was successfully made using ultrasonic wheat straw pulp.

Isolation and characterization of lignocellulose nanofibers from different wheat straw pulps

Wheat straw was cooked under different pulping processes: Soda (100°C, 7% NaOH, 150min), Kraft (170°C, 16% alkalinity, 25% sulfidity, 40min) and Organosolv (210°C, 60% ethanol, 60min). Once the pulps were obtained, lignocellulose nanofibers (LCNF) were isolated by mechanical process and TEMPO-mediated oxidation followed by a high pressure homogenization. After pulping process, the different pulps were characterized and its chemical composition was determined. The pulps characterization indicates that the Soda process is the process that, despite producing less delignification, retains much of the hemicelluloses in the pulp, being this content a key factor in the nanofibrillation process. Regarding the LCNF obtained by mechanical process, those nanofibers isolated from Organosolv wheat pulp (OWP) and Kraft wheat pulp (KWP) show low values for nanofibrillation yield, specific surface area and greater diameter. However, those nanofibers isolated from Soda wheat pulp (SWP) reach much higher values for these parameters and presents a diameter of 14nm, smaller than those obtained by TEMPO-mediated oxidation from OWP. Smaller diameters are generally obtained in TEMPO-oxidized LCNF. This work concludes that the lignin content does not affect greatly to obtain LCNF as does the hemicellulose content, so it is accurate to use a soft pulping process.

Composition, texture and methane potential of cellulosic residues from Lewis acids organosolv pulping of wheat straw

Cellulosic pulps have been successfully isolated from wheat straw through a Lewis acids organosolv treatment. The use of Lewis acids with different hardness produced pulps with different delignification degrees. The cellulosic residue was characterised by chemical composition, X-ray diffraction, FT-IR spectroscopy, N2 physisorption, scanning electron microscopy and potential for anaerobic digestibility. Surface area and pore volume increased with the hardness of the Lewis acid, in correspondence with the decrease of the amount of lignin and hemicellulose in the pulp. The non linearity of the correlation between porosity and composition suggests that an agglomeration of cellulose fibrils occurs in the early stages of pulping. All organosolv pulps presented a significantly higher methane potential than the parent straw. A methane evolution of 295Ncm3/g OM was reached by a moderate improvement of the accessibility of the native straw.

Mixing Bleached White Poplar and Wheat Straw Chemimechanical Pulps to Improve the Mechanical and Optical Characteristics

The aim of this study was to determine the optimum combination of wheat straw and white poplar (P. alba) chemimechanical pulps (CMPs) for producing newsprint paper. The CMP was prepared separately from the two raw materials. Cooking conditions included 10%, 12%, and 14% chemical charge based on w/w oven dry raw materials, maximum cooking temperatures of 120, 140, and 160 °C, and cooking time of 45 min. Hydrogen peroxide was used for bleaching the selected pulp. The results indicated that screened pulp yields were in the range of 54.3% to 61% and 80.9% to 85.9% for 18 cooking trials of wheat straw and white poplar, respectively. Handsheet brightness reached up to 52.9% and 61.9% for wheat straw and white poplar, respectively. The highest breaking length and burst index were related to CMP produced from 25% white poplar/75% wheat straw pulp blend. The best tear index was obtained using a mixture of 50% white poplar and 50% wheat straw pulp. Averages of breaking length, burst and tear indices ranged between 4.61 and 3.80 km, 2.31 and 2.55 kPa•m2/g, and 7.29 and 11.1 mN•m2/g, respectively. The strength properties of handsheets were higher than those reported for commercial newsprint except the breaking length of 50%/50% blend.

麦わらパルプシートの低密度化特性および表面自由エネルギーの変化

麦わらパルプシートの低密度化特性および表面自由エネルギーの変化

Modification in the properties of paper by using cellulase-free xylanase produced from alkalophilic Cellulosimicrobium cellulans CKMX1 in biobleaching of wheat straw pulp.

Alkalophilic Cellulosimicrobium cellulans CKMX1 isolated from mushroom compost is an actinomycete that produces industrially important and environmentally safer thermostable cellulase-free xylanase, which is used in the pulp and paper industry as an alternative to the use of toxic chlorinated compounds. Strain CKMX1 was previously characterized by metabolic fingerprinting, whole-cell fatty acids methyl ester analysis, and 16S rDNA and was found to be C. cellulans CKMX1. Crude enzyme (1027.65 U/g DBP) produced by C. cellulans CKMX1, having pH and temperature optima of 8.0 and 60 °C, respectively, in solid state fermentation of apple pomace, was used in the production of bleached wheat straw pulp. Pretreatment with xylanase at a dose of 5 U/g after pulping decreased pulp kappa points by 1.4 as compared with the control. Prebleaching with a xylanase dose of 5 U/g pulp reduced the chlorine charge by 12.5%, increased the final brightness points by approximately 1.42% ISO, and improved the pulp strength properties. Xylanase could be substituted for alkali extraction in C-Ep-D sequence and used for treating chemically bleached pulp, resulting in bleached pulp with higher strength properties. Modification of bleached pulp with 5 U of enzyme/g increased pulp whiteness and breaking length by 1.03% and 60 m, respectively; decreased tear factor of pulp by 7.29%; increased bulk weight by 3.99%, as compared with the original pulp. Reducing sugars and UV-absorbing lignin-derived compound values were considerably higher in xylanase-treated samples. Cellulosimicrobium cellulans CKMX1 has a potential application in the pulp and paper industries.

Fractionation of epidermal cells from wheat straw pulp by flotation

The wide availability of wheat straw makes it a promising raw material for various fiber products, but its heterogeneity makes it a challenging material to use. In addition to reducing paper properties, some cell types cause processing problems such as silicate deposition and poor dewatering. The aims of this work were to examine the fractionation tendency of wheat straw pulp cells in flotation and to determine the effect of fractionation on paper strength properties. A cell type categorization based on automatic optical fiber analysis was used to assess fractionation. The results showed that epidermal cells can be selectively enriched from unbleached wheat straw pulp by flotation and other short cells had a tendency to become enriched in the overflow fraction. The underflow fraction consisted mostly of fibrous material, as well as vessel elements and long parenchyma cells. Removal of the epidermal cells from pulp will reduce its silicate content and improve the strength properties of the paper.

Impact of Causticizing Calcium Carbonate from Soda Pulping of Wheat Straw on AKD Sizing

The causticizing calcium carbonate (CCC) produced in the causticizing stage of the chemical recovery process in alkaline pulping of wheat straw has a high silicate content and is difficult to convert to calcium oxide in the lime kiln. The CCC can be utilized as a paper filler to avoid costly lime re-burning, but the silicate content of the CCC can have a negative impact on the wet-end chemistry of the papermaking process. In this paper, the effect of the silicate content of the CCC filler on AKD sizing was investigated. CCC fillers of various silicate contents were prepared in the lab by causticizing green liquor from the soda pulping of wheat straw and were added to fiber suspensions at the wet end of the papermaking process. The results show that the impact of the CCC filler on AKD sizing was associated with its silicate content. As the silicate content increased, the specific surface area and negative charge density of the CCC particles markedly increased, resulting in more AKD adsorption onto the CCC particles instead of fibers.

The influence of chloride-based 1-butyl-3-methylimidazolium ionic liquid on the pulping process of wheat straw cooking

The chloride-based 1-butyl-3-methylimidazolium ionic liquid was applied in the wheat straw pulping process, and its related parameters were investigated in this paper. Single factor and orthogonal experimental methods were used to optimize the parameters of pulping process. The results showed that the optimum pulping parameters of ionic liquid for wheat straw cooking were: cooking temperature 100°C, cooking time 60min and the mass ratio of wheat straw to ionic liquid 1:9 at normal atmospheric pressure. Under these conditions, the pulp yield was up to 85%. According to the physical properties of the handsheets prepared at an amplified scale, pulp obtained by ionic liquid cooking had better properties than that from a standard chemical pulping process. Moreover, the ionic liquid solvent can be reused, and the recovery rate was more than 93.16%.

Method of Black Liquor Combustion to Remove Silicon from Wheat Straw Pulping

The effects of aluminium sulphate and sodium aluminate on physical and chemical properties of wheat straw pulp black liquor were studied. Results showed that the expansion rate was enhanced by increasing the aluminum salt content; furthermore, the effect of sodium aluminate was better than that of aluminum sulfate. The maximum desilication rate of 92.31% was reached with the addition of 3% sodium aluminate. A rheometer showed that aluminum salt had little impact on the viscosity of thick black liquor, so even at a high temperature it could be conveyed by pumps in paper mill at 110 °C. The effect of aluminium salt on the silicon removal rate during black liquor combustion was also studied. The experimental results showed that both aluminium sulphate and sodium aluminate helped to remove silicon. The desilication rate of sodium aluminate reached 62.33%, higher than that of aluminum sulphate. SEM-EDX illustrated that the aluminum and silicon ions were formed into insoluble precipitates. It was optimal to use 3% sodium aluminate as desilication agent.