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Pure deep eutectic solvents (DESs) system of choline chloride (ChCl)/Lactic acid (Lac) were demonstrated to be an effective strategy for extraction of lignin. In this study, two kinds of different promising solid acid (SA) with DESs were designed to promote the pretreatment of lignocellulose. The SA of phosphotungstic acid (H3O40PW12) and iron bromide (FeBr3) were introduced into DESs to extract poplar wood lignin and evaluate the antioxidant activity. It was found that 82.2% and 80.9% of lignin were obtained from poplar wood under H3O40PW12-ChCl/Lac acid and FeBr3-choline ChCl/Lac system with 4 h and 8 h, respectively. The lignin fractions with a high purity (>89%), low molecular weight (Mw 1800–2000 g/mol). Besides, the antioxidant activities of lignin fractions were better than butyl hydroxyanisole (BHA). Therefore, DES lignin has prominent antioxidant activity and could developed a potential natural cosmetics and food packaging.

Due to great advantages, such as simple operation, high porosity, and good fiber continuity, the working principle and research progress of electrospinning technology was studied and polyvinyl alcohol (PVOH) nanofibers were prepared via this process. Air filter paper was used as the receiving substrate to prepare electrospun nano air filter paper (NAFP). The PVOH concentration, static voltage, and receiving distance, were tested to explore the influence of spinning parameters on the filtration performance. Further, the microfiber morphology of the electrospun NAFP was observed. The performance of filter paper, including air permeability, pore size, initial resistance, filtration efficiency, and dust retention, were tested. The results showed that the electrospun NAFP had better filtration performance compared to the air filter paper, and simultaneously they had lower initial resistance and higher precision filtration efficiency. The nanofiber influenced the surface of the air filter paper, as it sharply reduced the pore size. When the spinning condition was 10%, 21 kV, and 15 cm, the pore size decreased approximately 0.6 times of the original, which meant the electrospun NAFP could capture particles ≥ 0.2 μm in size. Finally, after three repeated uses, the good filtration performance was maintained.

As a simple and effective biorefinery method, deep eutectic solvent (DESs) treatment was proposed to isolate lignin from lignocellulose. In this study, choline chloride/lactic acid (ChCl/Lac) was applied to extract high-purity and antioxidative lignin. Under the optimized conditions (120 °C for 12 h), the lignin profiling indicated that the recovered lignin had a high purity (94.18%), low molecular weight (Mw 1967 g/mol), and excellent thermal stability as compared with milled wood lignin. The lignin samples were characterized by using Fourier transform infrared spectrometry and nuclear magnetic resonance (NMR) spectra. In addition, the NMR spectra indicated the functional groups of the lignin extracted via DESs were less damaged and the backbone structure was not significantly modified. To further determine the potential application of DES-Lignin, the antioxidant activity was evaluated by radical scavenging ability. The IC50 values of a treatment time of about 12 h was 0.174. As expected, DES-Lignin showed obvious advantage in oxidation resistance. In short, the proposed process was considered as a promising biorefinery strategy for lignin first production.

The in-situ synthesis of calcium silicate in the fiber can not only meet the requirements for high loading of paper, but also make up and improve the reduction of paper performance caused by filling. In this investigation, the effects of pulp type, beating degree, fiber ratio, reaction time, rotational speed, dosage of lime milk and dispersant on calcium silicate loading and paper properties were investigated. The results showed that when the beating degree was 40 °SR, the ratio of softwood and hardwood pulp was 1:1, the reaction time was 60 min, the rotation speed was 600 r·min−1, the dosage of lime milk was 1.33 times of the theoretical amount, and the dosage of cationic polyacrylamide was 0.3 % (absolutely dry pulp), the ash content of hand-made sheet was 41.2 %, and the loading amount of calcium silicate was 26.3 %. Under this condition, the comprehensive performance of paper was the best.

Steam explosion (SE) pretreatment is a widely adopted method for enhancing enzymatic hydrolysis of lignocellulosic biomass in biorefinery. In this work, moderate SE pretreatment was employed to overcome the recalcitrance of cell wall through systematically assessing physicochemical and structural modifications. The hydrolysis yield of pretreated poplar by SE pretreatment (up to 69.7%) was higher than untreated poplar (26.8%). With increasing SE severity from 3.5 to 4.5, the contents of hemicellulose and lignin were reduced from 15.7 to 5.3% and 25.4 to 20.7%, respectively. Furthermore, it was observed that the cell wall structure became rough and collapsed. Meanwhile, channels emerged in the internal cell wall primarily due to the removal of hemicellulose and lignin along with the migration of lignin from inside to the out surface of cell wall. These results induced more exposure of cellulose to enzyme attacking, thus improved accessibility to cellulolytic enzymes. Addition of bovine serum albumin (BSA) obtained equal hydrolysis efficiency of 70.1% with a 33% reduction of enzyme loading, which was advantageous for enzyme costs effective.

Pretreatment of steam-exploded poplar by Fenton oxidation was used to effectively biodegrade lignin. The structure of lignin samples (LS from steam-exploded poplar and LSF from samples further treated by Fenton oxidation) obtained by enzymatic hydrolysis during pretreatment were characterized and compared. The results showed that the demethoxy reaction occurred in the process of Fenton oxidation. GPC results indicated that the weight average molecular weight (Mw) of LSF did not change significantly, indicating that that there was no significant condensation during Fenton oxidation pretreatment. Heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) results suggested that the proportion of the three-unit basic structural units of poplar (H, G, and S) were significantly changed during Fenton oxidation process, and more lignin S units were removed than lignin G units. The content of β-O-4 linkages was lower in LSF (74.0%, as a fraction of β-O-4 + β-5 + β-β) than in LS (78.2%), which indicated that β-O-4 linkages were destroyed to a certain extent during Fenton oxidation process, and the content of total lignin interunit linkages including β-O-4, β−β, and β-5 linkages over total lignin aromatic subunits (Ar%) in LSF was higher, reaching 49.9%.

A high-performance hydrogel was successfully fabricated using xylan-rich concentrated steam explosion liquid (CSEL). The method used was a free-radical graft copolymerization of acrylic acid (AA) and acrylamide (AM) onto a primarily xylan backbone in CSEL, with a redox system of ammonium persulfate/anhydrous sodium sulfite as the indicator and N,N`-methylenebisacrylamide (MBA) as the cross-linker. The effects of independent parameters (the dosages of the indicator, AM, AA, and the cross-linker) on the swelling ratio of the as-prepared hydrogel were studied via an optimal design of the response surface methodology (RSM). Under the optimal conditions (80.9 mg of initiator, 349.6 mg of AM, 988.7 mg of AA, and 9.39 mg of cross-linker), the swelling ratio of the prepared hydrogel (Xyl-AM-co-AA) was 276.6 g/g, which was close to the predicted value (255.7 g). The swelling behaviors of Xyl-AM-co-AA at different temperatures and pH values were also analyzed. The results showed that the swelling ratios varied at different temperatures and pH values, implying their potential use as smart materials. Analysis by Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the cross-linked and hygroscopic behavior of Xyl-AM-co-AA.

Ionic conductive hydrogels have been widely applied in sensors, energy storage and soft electronics recently. However, most of the polyvinyl alcohol (PVA) based ionic hydrogels are mainly fabricated by soaking the hydrogels in high concentration electrolyte solution which can induce the waste of electrolyte and solvent. Herein, we have designed cellulose nanofibrils (CNF) and ZnSO4 reinforced PVA based hydrogels through a one-pot simple freezing-thawing method at low ZnSO4 concentration without any soaking process. Furthermore, the hydrogel with 0.4% CNF exhibited stress up to 0.79 MPa (242% strain) and high ionic conductivity of 0.32 S m−1 (0.07 M ZnSO4). Moreover, hydrogel sensor displayed high linear gauge factor 1.70 (0–200% strain), excellent stability, durability and reliability. The integrated hydrogel sensor also showed excellent sensor performance for human motion monitoring. This work provides a new prospect for the design of cellulose reinforced conductive hydrogels via a facile method.

Cellulose nanocrystals (CNCs) is an exciting class of sustainable and carbohydrate material, which has great potential applications in molecular adsorption. However, the complex preparation process and limited adsorption capacity of CNCs hinder its commercial application. In this study, we design a novel functional cellulose nanocrystals-based adsorbent by an ingenious mixing of lignin-containing cellulose nanocrystals (LCNCs), sodium alginate (SA), and calcium chloride solution. Benefiting from the sulfonate groups of lignin, carboxyl groups of SA, the maximum adsorptive capability of LCNCs/SA beads for methylene blue was found to be 1181 mg g−1, which was significantly higher than previously reported biomass-based adsorbents. More importantly, LCNCs/SA beads can be reused several times. This strategy can not only improve the adsorption performance of CNCs-based materials, but also simplify the production technology of CNCs, which greatly promote the commercial application of CNCs materials.

To understand the modifications of lignin in the steam explosion process (209°C, 7 min), lignin samples in native poplar (LP), steam explosion solid residue (LS) and steam explosion liquid (LL) were separated and studied. The lignin samples (LP, LS and LL) were characterized and analyzed by size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance [carbon 13 numclear magnetic resonance (13C-NMR) and heteronuclear single quantum coherence or heteronuclear single quantum correlation experiment NMR (HSQC) NMR] analysis. The results revealed that the pretreatment induced reductions in amounts of β-O-4′, β-β′, and spirodienone structure, and increases in the syringyl/guaiacyl (S/G) ratio from 1.14 (LP) to 1.70 (LS) and 1.86 (LL). The HSQC NMR spectra also gave more information about the predominance of G and S units, and only small amounts of p-hydroxyphenyl (H) units. Moreover, SEC demonstrated the depolymerization and repolymerization of lignin, which were the main reasons for the increase in the average molecular weight of LS and the decrease in average molecular weight of LL, respectively. In brief, after steam explosion treatment, the lignin structure changed, but the backbone structure was not noticeably modified.

Pretreatment of steam-exploded wheat straw by ethanol has been used to dissolve lignin. Different pretreatment conditions were explored by varying reaction temperature, time, and the ratio of solid to liquid to determine that the rate of dissolution was approximately 51.6%. The examination of structural changes in LP (lignin from ethanol pretreatment pulp) showed that the conjugated carbonyl/carboxyl of lignin was partly destroyed during ethanol pretreatment and alkali extraction process. The content of total hydroxyl groups was increased with increasing ethanol pretreatment. Higher intensities of the aromatic ring in LP and LL (lignin from black liquor) fractions compared to that of weak pretreatment conditions indicated that some extent of lignin condensation occurred during the ethanol pretreatment. The ratios of S/G in LP were higher than in LL and removal of the methoxyl groups happened during the ethanol pretreatment process, and this led to changes in proportions of lignin structural units.

High filler retention would contribute to the good performance of reconstituted tobacco sheet (RTS), especially for adjusting its combustion speed. In this work, the cationic nanofibrillated cellulose (CNFC), as a retention additive for precipitated calcium carbonate (PCC), was applied for the RTS preparation following the conventional handsheets making. The PCC retention was increased significantly in the sheets, and the physical properties were improved obviously as well. The results showed that the PCC retention in RTS increased from 32.71% to 44.74% with the CNFC addition of 7 wt% (of oven dried PCC) when the initial dosage of PCC was 30 wt% (of oven dried pulp). The tensile strength of sheets increased from 11.92 N⋅m/g to 12.25 N⋅m/g, indicating that CNFC can play an important role in improving the physical properties of RTS. Also, the air permeability and softness could be improved greatly from 4.90 μm/pa·s to 5.64 μm/pa·s and from 114.99 to 83.33 respectively. The novel concept of CNFC acting as a retention additive of PCC for the RTS preparation was demonstrated to improve the performances of RTS products.

Biomass liquefaction is a major process used to obtain fuel additives, valuable chemicals, and high-quality activated carbon. In this work, three major biomass components (cellulose, hemicellulose, and lignin) and corn stalk were liquefied, and the corresponding liquefaction residue yields were 0.62%, 14.56%, 1.98%, and 1.29%, respectively, using polyhydric alcohols and acid catalysis under atmospheric pressure. The liquefaction residues from the corn stalk and biomass components were analyzed by thermogravimetric analysis, pyrolysis-gas chromatography/mass spectrometry, X-ray diffraction, and scanning electron microscopy. It was found that the corn stalk residues were mainly large molecules produced by interactions of some small molecules and incompletely degraded cellulose; condensation polymers generated from the reaction of degraded substances derived from lignin or hemicellulose; and insoluble components containing reactants from the degraded substances of the three major components and the insoluble substances generated by the liquefaction agents during the process.

γ-Valerolactone (GVL), a biomass-derived green chemical, offers an environmentally responsible solvent for conversion of lignocellulose to high value-added chemicals. Herein, we report a two-step process for directly producing cellulosic residual, furfural and lignin from Miscanthus × giganteus (M. × giganteus) bypassing the isolation of xylose, which exhibits promising advantage in energy reduction. The optimized pretreatment (100 mM FeCl

The requirement of continuous and stringent growth on filtration performance, including longer life span, higher overall efficiency, lower initial pressure drop and more cost effective, has still drove filter media manufactures to research and develop. One of the possible way to achieve these challenges, was to utilize a dual-channel head-box with two sets of pulp conveying system, which can produce filter media with bulky and gradient properties. In this study, three kinds of commercial cellulose were chosen to make two layers filtration media, analyzed the effect of fiber blend on physical properties and filtration performance. By fine-tune the slurry ratio of top layer, we made one single layer and two layers composition filter media, the thickness and air permeability of composition media were higher than single layer media. According to ISO 5011, filtration performance test has been done to compare single layer media with composition media, this composition gradient profiles that provided the life span 37.0% improvement to the terminal pressure drop during dust injecting, and the dust hold capacity improved 34.7%, the main contributor of dust hold capacity was decided by top layer, however, the overall efficiency was depended on wire side layer.

Air filter paper with a high filtration efficiency that can remove small-size pollutant particles and toxic gases is vital for human health and the environment. We report a nanofiltration paper that is based on wood fiber filter paper with good mechanical properties and a three-dimensional network structure. The filter paper was prepared by impregnation with multi-walled carbon nanotubes (MWCNTs) and phenol-formaldehyde (PF). The results showed that MWCNTs were present on the surfaces of the fibers and between the pores, which increased the specific surface area of the fibers and enhanced the effective interception of the particles. The optimum impregnation concentration of the MWCNT was 0.1%. Compared with the cellulose fibers (CFs), the average pore diameter of the 0.1% MWCNT–CF filter paper was reduced by 8.05%, the filtration efficiency was increased by 0.64%, and the physical properties were slightly enhanced. After impregnation with PF, the mechanical properties of the air filter paper were significantly enhanced. The PF on the fiber surfaces and at the junction of the fibers covered the MWCNTs. Based on the change in the filter paper properties after impregnation, the optimal filter paper strength index and filtration performance were observed at a solid PF content of 8.4%.

We prepared super-hydrophobic nanocellulose films using a non-toxic octadecylamine/polydopamine system. Octadecylamine, a low surface energy material, was used to provide hydrophobic alkyl long chains. Polydopamine was produced by dopamine under alkaline conditions, creating an adhesive substance, which reinforced the hydrophobic long chains and increased the surface roughness of nanocellulose. The effects of reagent concentration, reaction temperature, and reaction time on hydrophobicity were then investigated. The results showed that with a 1:1 mass ratio of nanocellulose to octadecylamine, and reacting at 60 °C for 4 h, the contact angle of the obtained composite membrane reached 168.2°. Scanning electron microscope images revealed that the modified nanocellulose had a smaller particle size and more uniform distribution, which effectively improved the hydrophobicity of the nanocellulose. Thus, the green preparation of superhydrophobic films with high-temperature resistance and wear resistance was realized, which contributed to the high-value utilization of nanocellulose.

The proper selection of solvents is important during liquefaction of biomass process to produce fuel additives and valuable chemicals. In this study, novel low-cost liquefying agents such 1,2-propanediol (PG), diethylene glycol (DEG), and 1,4-butanediol (BDO), as well as the traditional liquefying agent, ethylene glycol (EG), were used. It was found that the liquefaction yield of corn stalk in the presence of PG at the optimum temperature of 180 °C was up to 99.2%, which was higher than that of the other three liquefying agents. The main components and functional groups of bio-oil with an acid catalyst were characterized by gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). The chief constituents of bio-oil were complex, and corn stalk could be effectively degraded with PG liquefaction. Moreover, the thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) data also revealed that the fiber structure of the liquefied corn stalk was destroyed and essentially liquefied during PG liquefaction. Consequently, all the results in the study successfully confirmed that PG can provide an efficient and environmental process for generating bio-oil from lignocellulosic mass at a low cost in liquefaction of corn stalk.

Dialdehyde cellulose (DAC) was produced by the selective oxidation of pulp fibers, and was used to bind bovine serum albumin (BSA) by forming Schiff bases. The best binding conditions were as follows: a content of DAC aldehyde groups of 5.15 ± 0.13 mmol/g, a reaction time of 4 h, a reaction temperature of 40 °C, an initial medium pH of 8.0, and a DAC/BSA ratio of 1:50 (g/mL). After the binding of BSA, the FT-IR intensity of the characteristic absorption band (C O) of DAC was weakened, which indicated the formation of imine linkages. The Schiff bases formed between DAC and BSA gave the resulting material a higher thermal stability than that of DAC, and the slender fibers were twisted out of shape. Based on this Schiff base reaction, three different crude polysaccharide solutions (CPSs) were treated with DAC to deproteinize them under best bonding conditions. The results revealed that the DAC method had a higher deproteinization efficiency and polysaccharide recovery than the classical Sevag method. Therefore, the DAC treatment may be an ideal technique for the removal of proteins from CPSs for large-scale purification of polysaccharides.

With the increase in lignin availability, materials derived from micro- and nano-scale lignin developed rapidly. However, the tedious processes of raw-lignin pretreatment and poor stability seriously restrict the large-scale applications of lignin nanoparticles. To overcome these problems, in this work, a novel green and simple approach was developed to produce super long-term stable lignin nanoparticles (LTSL NPs). The LTSL NPs were prepared directly from black liquor via an acid precipitation method. The obtained LTSL NPs exhibited well uniformity, excellent dispersibility, controllable size, and super long-term stability in aqueous media (no apparent size increase or any particle precipitation for 90 days in neutral water medium). Analyses of nuclear magnetic resonance and ion chromatography revealed that LTSL NPs exhibited higher S/G ratio and higher content of hemicellulose comparing with the lignin nanoparticles which obtained from traditional solvent exchange (ethanol/H

Background Butanol is an important biofuel and chemical. The development of butanol-tolerant strains and the identification of functional butanol-tolerant genes is essential for high-yield bio-butanol production due to the toxicity of butanol. Results Escherichia coli BW25113 was subjected for the first time to error-prone PCR-based whole-genome shuffling. The resulting mutants BW1847 and BW1857 were found to tolerate 2% (v/v) butanol and short-chain alcohols, including ethanol, isobutanol, and 1-pentanol. The mutants exhibited good stability under butanol stress, indicating that they are potential host strains for the construction of butanol pathways. BW1847 had better butanol tolerance than BW1857 under 0–0.75% (v/v) butanol stress, but showed a lower tolerance than BW1857 under 1.25–2% (v/v) butanol stress. Genome resequencing and PCR confirmation revealed that BW1847 and BW1857 had nine and seven single nucleotide polymorphisms, respectively, and a common 14-kb deletion. Functional complementation experiments of the SNPs and deleted genes demonstrated that the mutations of acrB and rob gene and the deletion of TqsA increased the tolerance of the two mutants to butanol. Genome-wide site-specific mutated strains DT385 (acrB C1198T) and DT900 (rob AT686–7) also showed significant tolerance to butanol and had higher butanol efflux ability than the control, further demonstrating that their mutations yield an inactive protein that enhances butanol resistance characteristics. Conclusions Stable E. coli mutants with enhanced short alcohols and high concentrations of butanol tolerance were obtained through a rapid and effective method. The key genes of butanol tolerance in the two mutants were identified by comparative functional genomic analysis. Electronic supplementary material The online version of this article (10.1186/s13068-019-1405-z) contains supplementary material, which is available to authorized users.

Additional file 1.

The hemicellulose, cellulose and lignin were directly separated from corn stalk, and their liquefaction processes were investigated via acid-catalyzed solvolysis treatment with 1,2-propylene glycol (PG) and diethylene glycol (DEG) to produce bio-oil and residues. The main components, functional groups and organics structure of bio-oil were analyzed by the FTIR, 1H-NMR, 13C-NMR, GCMS, and TGA. It was found that there had a similar tendency in the liquefaction processes of cellulose, hemicellulose and lignin. Corn stalk and its biomass components were degraded and formed plentiful low-molecular polymers by acid catalysis, prior to polymers were converted into corresponding PG/DEG-derivatives. Finally, low-molecular weight soluble substances and insoluble residues were generated by decomposition and polymerization. Additionally, more than 80% compounds' carbon number in four bio-oils was below 25. The residues were mostly stemmed from macromolecules produced by degradation products and PG/DEG or re-polymerization between degraded small molecules.

Effects of the pretreatment of wheat straw by steam explosion and ethanol were evaluated relative to the structural changes of lignin from the pretreated pulp. The lignin from steam explosion pulp (LS), lignin from steam blasting residual liquid (LL), lignin from ethanol pretreatment pulp (LE), lignin from black liquor (LB), and lignin from wheat straw (LW) were separated, and the structural characteristics of the lignin fractions were compared based on analyses of Fourier transform-infrared, ultraviolet, thermogravimetric, and 1H and 13C nuclear magnetic resonance spectra. The proportions of the three structural units in all lignin fractions clearly changed during the pretreatment process because of inter-conversion reactions. The conjugated structure of lignin was destroyed in the pretreatment process and was also affected by the alkali extraction process. The alcoholic hydroxyl links on the aliphatic side chain were partly transformed into carbonyl groups during ethanol pretreatment. Demethoxylation occurred in all lignin fractions during the ethanol pretreatment and steam explosion process. The thermal stability of the LB fraction was relatively high because of the condensation reaction.

A new method was developed to characterize the cellulose fiber (hardwood dissolving pulp) size distribution after 50 wt% sulfuric acid hydrolysis at different hydrolysis temperatures with exponential and Rosin-Rammler (R-R) laws. The results show that the two above laws can be effective to explain the cellulose hydrolysis process. The exponential and the R-R laws were found to be well fitted to the sulfuric acid hydrolyzed cellulose fiber length distribution. The cumulative number distribution from Fiber Tester was shown to fit the exponential distribution well, while the cumulative mass distribution obtained from the acid hydrolysis was found to be suitable to the R-R law via an approximation process. The results from SEM analyses also supported the above conclusions. This approach can be used to characterize the cellulosic fiber properties before a further process of biorefinery, nanocellulose preparation, or other application of lignocellulosic fibers.

Synthetic fibers have characteristics that plant fibers do not have, such as water resistance, chemical resistance, heat resistance, and thermal stability. If mixed with plant fibers and applied to make air filter paper, then the required properties of paper could be obtained. Two kinds of synthetic fiber, polypropylene (PP) and polyester (PET), were mixed with softwood pulp to make air filter base paper. The effects of the mixing ratio, the beating degree of softwood pulp, the variety and addition amount of reinforcing agents, and the process of pressing and drying on the properties of base paper were explored. Samples were found to meet the requirements of the physical properties and porosity of the filter paper base paper at the same time when the mixing ratio of synthetic fiber and plant fiber was 20/80, the beating degree of softwood pulp was 22 °SR, and the added amount of cationic polyacrylamide (CPAM) was 0.06%. The PP fiber fell off easily from the page, but PET fiber did not. The addition of PET fiber increased the porosity, tear index, and folding endurance of the paper. In sum, PET fiber was more suitable for making air filter paper than PP fiber.

Industrial hemp is a non-wood fiber material that can be used for papermaking due to a high yield of hemp raw material and high-quality physical properties of its pulp. Hemp is already used as a raw material for papermaking and other industrial productions. The chemical composition of hemp root bast (HRB) was analyzed. HRBs were pulped using a soda-anthraquinone (Soda-AQ) process and bleached with oxygen (O), chlorine dioxide (D), and alkali (E) using the bleaching sequence OD0ED1. The results showed that HRB can be a suitable raw material for papermaking; the HRB pulp had a high viscosity (893 mL g-1) and brightness (85.52% ISO-brightness).

Without any fillers and optical brightening agents (OBAOBAOBAs), 15%–20% substitution of high-yield pulps (HYPs) for the hardwood bleached kraft pulp (BKP) in a paper furnish can decrease the brightness stability significantly because HYP contains a large amount of lignin. However, using mineral fillers such as precipitated calcium carbonate (PCC) and OBAOBAOBA in a HYP-containing paper can essentially eliminate the negative effect of HYP substitution on the brightness stability of uncoated wood-free paper. During the commercial production of traditional wood-free paper products, which usually use both PCC and OBAOBAOBA, 15%–20% HYP substitution for the hardwood BKP will not have practical impact on the paper brightness stability. Results from commercial printing and writing paper production support the same conclusion.

Acetic acid-catalyzed steam explosion pretreatment was applied to wheat straw at temperatures of 190 and 210 °C for 2, 6, and 10 min of residence time. The effects of pretreatment conditions on the total gravimetric recovery, hemicellulose sugars, glucose content, and yield of the enzymatic hydrolysis of cellulose were studied. The results indicated that the total gravimetric recovery decreases while the solubility of hemicellulose and the yield of cellulose enzymatic hydrolysis increase as the pretreatment severity increases. Pretreatment at 190 °C with a 2-min residence time resulted in the highest total gravimetric recovery, 58.9%. The optimum defiberation, glucose content, and enzymatic hydrolysis yields of 70.4 and 79.6%, respectively, occurred following pretreatment at 210 °C with a 10-min residence time. The optimal pretreatment condition was determined to be 190 °C for 10 min. Under the optimum conditions, the recovery yield of all sugars reached 42.7%. This pretreatment resulted in the highest recovery yield of all sugars.

The research aimed at optimizing the conditions of pretreatment of wheat straw and of enzymatic hydrolysis of the cellulose (ethanol pulp). The ethanol pretreatment process involving acid-catalytic and enzymatic hydrolysis were evaluated for bioconversion of wheat straw to glucose. The influence of the independent process variables on cellulose yields, cellulose contents, lignin contents, and the rate of lignin removed were analyzed over a broad range by the response surface methodology (RSM). The results of the factorial experiment showed that the significant external factors affecting acid-catalytic ethanol pretreatment of wheat straw were ethanol concentration, maximum temperature, acid dosage, and time at maximum temperature. By analyzing the response surface plots, the optimum process parameters for pretreatment were obtained as follows: ethanol concentration 65%, maximum temperature 180 ºC, acid dosage 1.2%, and time at maximum temperature 60 min. Pulps with residual klason lignin ranging from 9.27% to 13.56% (w/w) were prepared from wheat straw using the acid-catalytic ethanol pretreatment process and were evaluated for bioconversion using enzymatic hydrolysis of the cellulose fraction to glucose. The effects of temperature, pH value, time of enzymolysis, and cellulase dosage on the hydrolysis yield of cellulose were separately examined.

In an effort to resolve problems related to the difficulty of degradation of the chelating agents EDTA and DTPA, this study used a kind of water treatment agent, 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), as the chelating agent in the OPQP bleaching sequence of Acacia mangium kraft pulp. The Q stage was optimized with the use of response surface methodology (RSM) based on the Box-Behnken design (BBD). The results showed that the optimum chelating conditions for subsequent hydrogen peroxide bleaching were the following: Temperature of 54 °C, hold time 32 min, and dosage of agents 0.4%. These conditions resulted in the highest brightness value of 80.12% ISO and the selectivity coefficient of 0.46. Under these optimum chelating conditions, the results showed that the effect of HEDP in bleaching is better than that of EDTA with regard to viscosity of pulp, and that HEDP is similar to EDTA and DTPA in other properties.

By following the solute exclusion technique, we determined the pore characteristics of 3 hardwood high-yield pulps (aspen, birch, maple). The fiber saturation point (FSP) was 1.40, 1.36 and 1.19 g water/g pulp, for aspen, birch, maple, respectively, which is lower than that of chemical pulps. Different fractions obtained from the Bauer-McNett classifier showed that the HYP fines have much more pore volume than their long fiber counterparts. The effects of beating, drying and re-wetting on the pore characteristics of HYP were also studied. Beating led to increased total pore volumes. Upon drying and re-wetting, much of the small pores from the HYP underwent permanent closure while the big pores were only slightly affected. Finally, the relationship between the water retention value (WRV) and FSP for HYP was examined.