Wheat Straw Pulp Research Articles

Research of Cooking Methods for Producing Wheat Straw Pulp by Microwave Irradiation Mixed-Alkali Method at Atmosphere Pressure

Cooking method of wheat straw pulp was investigated by microwave radiation at ambient pressure. In the microwave irradiation, wheat straw was cooked with mixed-alkali at normal pressure. The optimum process conditions determined by single-factor and orthogonal experiments were provided as follows: total alkali content was 16%, the ratio of solid to liquid was 1:6,and microwave irradiation time was 45min. Paper performance tests was run and showed that the index was equal or better than those produced by conventional methods. A consistent yield (around 60.1%) of wheat straw pulp was observed after repeated experiments.

Biobleaching of Wheat Straw Pulp using Laccase and Xylanase

Wheat straw pulp can be considered to be one of most important raw materials for specialty and functional paper products. Bleaching sequences involving laccase and xylanase were applied to bleach wheat straw pulp. The bleached pulp properties after a sequence of xylanase (X), laccase (L), and extraction (E), i.e. XLE, were compared with those of LE and LEX sequences. It was found that the XLE bleaching sequence was the most suitable sequence for laccase and xylanase synergetic biobleaching. The bleaching results of OXLEQP and OQP beaching sequences (where O stands of an oxygen stage, Q indicates a chelation stage, and P means peroxide) were compared. For a specific target brightness level of over 80% ISO, XL pretreatment was found to save 28.6% of the H2O2 requirement and increase the viscosity by 6.7% compared with the OQP bleaching sequence. It was also found that synergetic biobleaching could decrease the consumption of refining energy. There were no detectable adsorbable organic halides found in the biobleaching effluents.

Using of Magnesium Hydroxide and Sodium Hydroxide in DP Beaching of NaOH-AQ Wheat Straw Pulp

Sodium hydroxide (NaOH) substituted by magnesium hydroxide (Mg(OH)2) as control agent and alkali source were investigated in chlorine dioxide bleaching and hydrogen peroxide bleaching of NaOH-AQ wheat straw pulp. The effects of alkali sources on pulp properties, including brightness and tensile strength, were investigated. The four experimental groups, including DNaOHPNaOH, DNaOHPMg(OH)2, D Mg(OH)2PNaOH and DMg(OH)2PMg(OH)2, were studied in this paper. The results showed that the brightness and tensile strength of DMg(OH)2PMg(OH)2 pulp was slightly lower than that of DNaOHPNaOH pulp. But there were more residual ClO2 and residual H2O2 in the effluents of DMg(OH)2PMg(OH)2 bleaching process than that in the effluents of DNaOHPNaOH bleaching process, which illustrated that DMg(OH)2PMg(OH)2 bleaching process had higher bleaching efficiency than DNaOHPNaOH bleaching process. The influence of Mg(OH)2 replacing NaOH was more obvious when it was used in the bleaching process of P stage than that in the D stage. The replacement of NaOH with Mg(OH)2 in D Stage can lower the dosage of alkali used in the following P stage.

PAPER PHYSICS: Fractionation of wheat straw pulp cells in a hydrocyclone

PAPER PHYSICS: Fractionation of wheat straw pulp cells in a hydrocyclone

Xylanase and laccase aided bio‐bleaching of wheat straw pulp

AbstractThis paper illustrates the application of enzymes (e.g. xylanase and laccase) in the bio‐bleaching of non‐woody material (e.g. wheat straw). The objective of this paper is to develop an alternative bleaching sequence avoiding the use of chlorine during bleaching. In the study, wheat straw pulp has been treated with commercially available xylanase and laccase separately and sequentially. Optimised parameters for the xylanase pre‐treatment are pH 5.5, temperature 60°C, enzyme dose 6 IU/g, pre‐treatment time 75 min and speed of agitation 80 rpm. Similarly, optimum parameters for laccase delignification are pH 3.5, temperature 60°C, enzyme dose 22.5 IU/g of oven dried pulp, mediator concentration 1.5% of oven dried pulp (odp), delignification time 10 h and speed of agitation 120 rpm. On the other hand, sequential treatments such as xylanase pre‐treatment (X) followed by laccase (L) and alkaline perdoxide (E) in presence of mediator have shown better reduction in kappa number, that is 24.84% as compared to LE in presence and absence of a mediator.

Alkali consumption of aliphatic carboxylic acids during alkaline pulping of wood and nonwood feedstocks

Abstract The carbohydrate degradation products have been examined, which are formed during the conventional kraft pulping of a softwood, hardwoods, bamboo, and wheat straw as well as soda and soda-anthraquinone pulping of wheat straw. The focus was on “volatile” acids such as formic and acetic acids and “nonvolatile” hydroxy monocarboxylic and dicarboxylic acids. The different consumption profiles were obtained for the charged alkali required for the neutralization of these aliphatic acids depending on the feedstock and the cooking method. The relative composition of the acid fraction in the black liquors of softwood and hardwood and nonwood feedstocks showed characteristic variations. However, in the case of wood kraft pulping, the variations in cooking conditions (effective alkali 19–21% and cooking temperature 155–170°C) had no significant effect on the acid composition. The total amount of volatile and hydroxy acids formed during pulping at a typical target κ number level for each feedstock ranged from 78 to 174 kg ton-1 based on o.d. feedstock. It was highest in birch kraft pulping and lowest in wheat soda-anthraquinone pulping.

Removal of silicon from green liquor with carbon dioxide in the chemical recovery process of wheat straw soda pulping

Green liquor in the chemical recovery process of wheat straw pulping was treated with carbon dioxide to precipitate silicon by a one-step process and a seeding process to address problems caused by high silicon content. The total silicon removal, the particle size, and the sedimentation performance of silica were investigated. The results showed that the pH of green liquor decreased with increasing amounts of carbon dioxide, becoming stable after the pH decreased to 8.2. Reaction temperature had no significant effect on the removal of silicon. About 99% of silicon removal was achieved at a pH of 9.2 at room temperature. In the one-step process, the particle size increased and the silica sedimentation performance improved with decreasing pH. The particle size decreased and the sedimentation performance improved with increasing reaction temperature. At a pH of 9.5 and reaction temperature of 80°C, the particle size was 10.43 μm. In the seeding process, 40% green liquor was treated with carbon dioxide at 80°C until the pH was about 10.5, then the 40% treated green liquor was mixed with the remaining 60% of green liquor. The mixture was then treated with carbon dioxide at a reaction temperature of 80°C until the pH reached 9.5. In that situation, the particle size reached 14.11 μm. Compared with the one-step process, the particle size of silica generated by the seeding process was bigger and the sedimentation performance was improved.

Characteristics of Poplar Preconditioning Followed by Refining Chemical Treatment Alkaline Peroxide Mechanical Pulp Fiber Fractions and Their Effects on Formation and Properties of High-Yield Pulp Containing Paper

High-yield pulp (HYP) has various fractions, and they not only play an important role in the papermaking process but also affect paper properties. Hence, it is necessary to clarify the impact of different HYP fractions on paper formation and properties. In this study, the characteristics of poplar preconditioning followed by refining chemical treatment alkaline peroxide mechanical pulp fractions were determined, and their effects on paper formation and paper properties were investigated. The results show that the HYP fiber is not as flexible as the bleached wheat straw pulp fiber. Compared with the HYP long-fiber fraction, the short-fiber fraction can improve the formation index more favorably. It was also found that the long-fiber fraction can maintain the strength properties, while having a negligible effect on the light-scattering coefficient; on the contrary, the short-fiber fraction can improve the light-scattering coefficient effectively but reduces the strength properties.

Comparative study of toxic chlorophenolic compounds generated in various bleaching sequences of wheat straw pulp

This study compared the chlorophenolic com- pounds generated during the bleaching of wheat straw pulp. The six different bleaching sequences used in present study were: (i) chlorine-extraction-hypo (CEH); (ii) persul- phate-peroxide-chlorine-extraction-hypo (Px-P-CEH); (iii) oxygen-chlorine-extraction-hypo (OCEH); (iv) chlorine dioxide-extraction-chlorine dioxide (DED); (v) persulphate- peroxide-chlorine dioxide-extraction-chlorine dioxide (Px- P-DED); and (vi) oxygen-chlorine dioxide-extraction- chlorine dioxide (ODED) bleaching. The concentrations of a large number of identified chlorophenolic compounds often exceed their threshold concentrations in CEH effluent. Therefore, the untreated effluent generated from the CEH bleaching sequence of wheat straw pulp can be considered toxic. Prebleaching (PxP) reduces the generation of chloro- phenolic compounds by 36 % in the (PxP)CEH sequence. Oxygen prebleaching reduces the generation of chloro- phenolic compounds by 86 % in the OCEH bleaching effluent. The PxP also reduces the generation of chlorophenolic compounds by 46 % in the (PxP)DED bleaching sequence and oxygen delignification substantially reduces the generation of the compounds by 78 %.

Bleach boosting effect of xylanase A from Bacillus halodurans C-125 in ECF bleaching of wheat straw pulp

Past studies have revealed major difficulties in applications of xylanase in the pulp and paper industry as enzymes isolated from many different species could not tolerate high temperatures or highly alkaline conditions. The thermostable xylanase A from Bacillus halodurans C-125 (C-125 xylanase A) was successfully cloned and expressed in Pichia pastoris with a yield as high as 3361U/mL in a 2L reactor. Its thermophilic and basophilic properties (optimal activity at 70°C and pH 9.0), together with the fact it is cellulase-free, render this enzyme attractive for compatible applications in the pulp and paper industry. The pretreatment of wheat straw pulp with C-125 xylanase A at pH 9.0 and 70°C for 90min induced the release of both chromophores (Ab237, Ab254, Ab280) and hydrophobic compounds (Ab465) into the filtrate as well as sugar degradation. Moreover, the addition of 10U xylanase to 1g wheat straw pulp (dry weight) as pretreatment improved brightness by 5.2% ISO and decreased the kappa number by 5.0% when followed by hydrogen peroxide bleaching. In addition, compared with two commercial enzymes, Pulpzyme HC and AU-PE89, which are normally incorporated in ECF bleaching of wheat straw pulp, C-125 xylanase A proved to be more effective in enhancing brightness as well as preserving paper strength properties. When evaluating the physical properties of pulp samples, such as tensile index, tearing index, bursting index, and post-color (PC) number, the enzymes involved in pretreating pulps exhibited better or the same performances as chemical treatment. Compared with chemical bleaching, chlorine consumption can be significantly reduced by 10% for xylanase-pretreated wheat straw pulp while maintaining the brightness together with the kappa number at the same level. Scanning electron microscopy revealed significant surface modification of enzyme-pretreated pulp fibers with no marked fiber disruptions.

Molecular Mass Distribution of Lignin from the Alkaline Pulping of Hardwood, Softwood, and Wheat Straw

The behavior of lignin during kraft (hardwood, softwood, and wheat straw) and soda-AQ (wheat straw) pulping was studied, mainly in terms of delignification degree and molecular mass distribution (MMD). In the initial delignification phase (at 140°C for 15–60 min), a prominent part of the dissolved softwood kraft lignin (18–25 g/L, MM mostly > 3,000 Da) was found in the liquid phase of chip cavities, rather than in the external bulk black liquor (5–7 g/L, MM mostly < 3,000 Da). The maximum weight average MM values ( w) of the soluble lignin under conventional cooking conditions were detected for the kraft softwood (4,100 Da), and kraft birch (3,400 Da) when the degree of delignification was 65–75%, corresponding to a residual lignin content of 5–10%. The maximum w of the dissolved wheat straw kraft (5,050 Da) and soda-AQ (5,900 Da) lignins was clearly higher than that of wood-based kraft lignins (2,950–4, 100 Da).

Study on Synthesis of Cationic Water in Water Polyacrylamide Emulsion Strength Agent

Emulsion copolymerization of acrylamide (AM) and cationic monomer DMC (methyl acrylacyl oxyethyl trimethyl ammonium chloride) was studied. A series of cationic polyacrylamide (CPAM) emulsion were synthesized using Water in water emulsion polymerization. Influence of polymerization conditions such as cationic monomer (DMC) ratio, reaction time, the initiator dosage on synthetic product strengthening effect to paper pulp was studied. It was showed that the CPAM emulsion optimal synthetic conditions was that AM monomer second adding amount was 60% AM total amount, ammonium persulfate initiator and sodium hydrogen sulfite initiator dosage was 0.138g and 0.03g respectively, mass ratio of DMC and AM was 15:85, reaction time was 7 hours. When the dosage of CPAM emulsion was 1.0% to absolute dry bleached wheat straw pulp, distinct strengthening effect was acquired, tensile index and tearing index of handsheet was increased by 27.2% and 26.8% respectively.

Study on Application as Paper Strengthening Agent of Homemade CPAM Emulsion with other Cationic Strengthening Agent

Application in paper pulp as dry strengthening agent of homemade water in water cationic polyacrylamide (CPAM) emulsion was studied. Good collaborative effect was achieved when Homemade CPAM was used in bleached wheat straw pulp with strengthening agent E and with cationic additives L as paper pulp strengthening agent. It was also showed that distinct strengthening effect was obtained when homemade CPAM emulsion was applied in mixture of wood pulp which was needle bleached kraft pulp (NBKP) and straw pulp, breaking length and tearing index of hand sheet made of mix pulp was respectively increased by 22.2% and17.0% when the dosage of CPAM was 0.8% of dry fiber. Through analysis of handsheet section scanning electron microscopy (SEM) photos, strengthening mechanism of CPAM emulsion to paper pulp was preliminary studied.

Xylanase and Ultrasound Assisted Pulping of Wheat Straw

In the present work, a novel approach to pretreat wheat straw pulping was investigated with ultrasound and xylanase to achieve maximum reduction in lignin content. Sequential xylanase pretreatment and alkaline pulping was found to reduce kappa number by 0.31 to 4.84 % compared with only alkaline pulping alone at different pulping conditions. Although Klason lignin of ultrasound-treated straw was found to be 7.37 % less compared with untreated straw, sequential ultrasound pretreatment and alkaline pulping could not show any significant reduction in kappa number compared with alkaline pulping alone. Also, sequential xylanase and ultrasound pretreatment could not show any significant reduction in kappa number. Total yield of the pulp was found to be less in ultrasound-assisted processing compared with both alkaline pulping alone and sequential xylanase pretreatment and alkaline pulping.

Improvement of bleached wheat straw pulp properties by using aspen high-yield pulp

The bleached wheat straw pulp (BWSP) accounts for about 25% of the virgin fiber supply in the Chinese Pulp and Paper Industry. As a non-wood chemical pulp, BWSP is known to have low bulk, low light scattering coefficient and poor drainage due to its high content of parenchyma cells. In this study, a high-quality aspen high-yield pulp (HYP) was used to improve the BWSP properties at the laboratory scale. The results indicate that adding 5–20% aspen HYP into unrefined or refined BWSP can minimize many of the drawbacks associated with the BWSP: improving its drainage, bulk, light scattering coefficient and opacity. The addition of a small amount (up to 20%) of aspen HYP can also significantly increase the tear index of BWSP with only a slight decrease of the tensile index.

Mass balance of silica in straw from the perspective of silica reduction in straw pulp

The high silica content of wheat straw is an important limiting factor for straw pulping. High silica content complicates processing and black liquor recovery, wears out factory installations, and lowers paper quality. Each section of wheat straw has different cells and chemical compositions and thus different silica content. In this work, the silica content of balled straw samples were examined according to their physical components, including internodes, nodes, leaves (sheath and blade), rachis, grain, other plant bodies, and other plant spikes. Mass distribution of silica was determined by a dry ashing method. Half (50.90%) of the silica comes from leaves, and its mechanical separation will reduce the silica content in wheat straw pulp significantly. Destroying silica bodies by sonication will increase the strength properties of straw pulp.

Effect of prior mechanical refining on biobleaching of wheat straw pulp with laccase/xylanase treatment

Wheat straw pulp was mechanochemically processed in a PFI mill in order to improve the effect of laccase/xylanase system (LXS) treatment before bleaching. The delignification and bleachability of the prepared pulp were investigated. The delignification of the prepared pulp could be enhanced with the mechanochemical processing (refining) and LXS treatment. The delignification was increased by 29.8% with refining 7000 revolutions and 5 IU/g enzyme dosage. The LXS treatment after the mechanochemical process could save 28.6% effective usage of chlorine in the subsequent hypochlorite bleaching process, compared with the traditional bio-bleaching. The crystallinity of cellulose was increased by the co-treatment with mechanochemistry and LXS treatment. This result was further supported by the observations from SEM. This co-treatment with mechanochemistry and bio-treatment enhanced the delignification and bleachability of pulp.

Aspects on bleaching and tempo-mediated oxidation of wheat straw pulp fractions

This study outlines research concerning wheat straw fines, including their impact on pulp bleachability, their modification by chemical means, and their use as a dry strength enhancer in a paper application. Results show that primary fines constituting about 23% of the whole wheat straw pulp had a large negative impact on pulp bleachability. The differences in response to bleaching were due to the different properties of the fines, i.e. higher kappa number, higher metal ion content, lower brightness, and lower viscosity compared to that of fibers. It was also shown that the fines fraction is more difficult to oxidize and does not reach as high fiber charge levels as that of the other fractions. However, at a dosage of ≥ 3 mmol hypochlorite/g it was possible to prepare nanofibers from wheat straw fines that showed a good strength-enhancing effect in a paper product. The fact that removal of fines from wheat straw pulps by fractionation improves bleachability and also drainage properties at the same time, while simultaneously the fines can be modified and used as a strength enhancer, is very interesting when evaluating the potential of this type of annual plant as a source for production of different paper products.

β-Glucosidase immobilisation on synthetic superparamagnetic magnetite nanoparticles and their application in saccharification of wheat straw and Eucalyptus globulus pulps

β-Glucosidase from Trichoderma reesei was immobilised on synthetic superparamagnetic magnetite (Fe3O4) nanoparticles with a mean diameter of 10 nm and were used to supplement cellulase in the enzymatic hydrolysis of three substrates: wheat straw pretreated by steam explosion, Eucalyptus globulus pretreated by hydrothermolysis and E. globulus pretreated by hydrothermolysis followed by alkaline extraction. The hydrolysis yields for each pretreated material, using immobilised β-glucosidase (I-βG) and free cellulase, were 76.1%, 83.6% and 75.6%, respectively, and resulted in an improved hydrolysis yields compared with only cellulase. These yields were at most 10% lower than yields reached with free enzymes. The (I-βG) was magnetically recovered and successfully reused twice. The differences in the hydrolysis yields were not significant (p > 0.05) in the case of steam-exploded wheat straw and E. globulus pretreated by hydrothermolysis followed by alkaline extraction. The immobilisation of enzymes provides an opportunity to reduce the costs of enzymes in the bioethanol production process.

Hydrolysis of organosolv wheat pulp in formic acid at high temperature for glucose production

Organosolv methods can be used to delignify lignocellulosic crop residues for pulp production or to pretreat them prior to enzymatic hydrolysis for bioethanol production. In this study, organic solvent was used as an acidic hydrolysis catalyst to produce glucose. Hydrolysis experiments were carried out in 5–20% formic acid at 180–220°C. Wheat straw pulp delignified with a formicodeli™ method was used as a raw material. It was found that glucose yields from pulp are significantly higher than yields from microcrystalline cellulose, a model component for cellulose hydrolysis. The results indicate that cellulose hydrolysis of real fibers takes place more selectively to glucose than hydrolysis of microcrystalline cellulose particles does. The effect of the particle size on pulp hydrolysis was investigated, the crystallinity of hydrolyzed pulp was measured by XRD analysis, and the product distribution and its influence on the process was discussed.