Haisong Wang

Magnetic cellulose–chitosan hydrogels prepared from ionic liquids as reusable adsorbent for removal of heavy metal ions

Magnetic hybrid hydrogels with a novel polymeric coating consisting of chitosan and cellulose were prepared. By coating cellulose and chitosan, we combined the renewability and biocompatibility of cellulose and chitosan as well as the magnetic properties of Fe(3)O(4) to create a hybrid system to adsorb heavy metals.

A novel approach for the preparation of nanocrystalline cellulose by using phosphotungstic acid

In this work, a sustainable and green process to prepare nanocrystalline cellulose (NCC) from bleached hardwood pulp was demonstrated. Rod-like nanocrystalline cellulose with the size of 15-40 nm in width and hundreds of nanometers in length was obtained through H3PW12O40 (HPW)-catalyzed hydrolysis of bleached pulp fibers under the mild reaction conditions. Thermogravimetric analysis revealed that the resulting NCC exhibited much higher thermal stability than the partially sulfated NCC (prepared by sulfuric acid). In addition, the concentrated HPW could be easily recovered and recycled through the extraction with diethyl ether, and the recovered HPW could be reused for several rounds of cellulose hydrolysis without activity lost. These fundamental studies are of crucial importance for the development and application of NCC products/NCC-based biomaterials with good thermal stability.

Comparison of different alkali-based pretreatments of corn stover for improving enzymatic saccharification

Corn stover was treated with NaOH, NaOH+anthraquinone (AQ), NaOH+Na(2)SO(3) (alkaline), NaOH+Na(2)SO(3) (neutral), and NaOH+Na(2)S, respectively. The treated corn stover was subjected to hydrolysis with cellulase (20 FPU/g dry biomass) and β-glucosidase (10I U/g dry biomass). Compared with other pretreatment methods, alkaline sodium sulfite pretreatment (ASSP) at a relatively low temperature of 140°C provided for the best lignin removal of about 92%. After ASSP with 10 wt.% of the total alkali charge (Na(2)SO(3):NaOH=1:1) at 140°C for 30 min and subsequent enzymatic hydrolysis, a total sugar yield of 78.2% was obtained on the basis of the amount of glucose and xylose released from raw corn stover. This yield was 24.0% higher than that achieved with NaOH only under the same conditions. Therefore, the supplement of Na(2)SO(3) in alkali pretreatment can facilitate delignification and significantly improve the enzymatic saccharification.

Hemicellulose isolation, characterization, and the production of xylo-oligosaccharides from the wastewater of a viscose fiber mill

Viscose fiber mills generate a lot of wastewater enriched with hemicelluloses. The structure of the hemicellulose in the wastewater was characterized and the hemicellulose was isolated to produce xylo-oligosaccharides (XOS). It was confirmed that the hemicellulose was mainly 4-O-methylglucuronoxylan with a small amount of glucomannan and xyloglucan. The 4-O-methylglucuronoxylan was completely de-acetylated and linear with a few 4-O-methyl glucuronic acid attached. After purified by the acid precipitation and washing, the hemicellulose was pretreated by dilute acid, and then subjected to xylanase hydrolysis. After the dilute H2SO4 pretreatment at pH 2.6 and 150°C for 30min and the followed xylanase hydrolysis (65IU/g xylan), the total XOS yield was improved from 0.215 to 0.578g/g xylan. The percentage of XOS in the final sugar product was 68.9%. These results demonstrated the potential economical and environmental benefits of the process to utilize the byproducts from viscose fiber mills.

Combined Deacetylation and PFI Refining Pretreatment of Corn Cob for the Improvement of a Two-Stage Enzymatic Hydrolysis

A combined deacetylation and PFI refining pretreatment was applied to corn cob for the improvement of a two-stage enzymatic hydrolysis. In stage 1, the pretreated corn cob was first hydrolyzed by xylanase to produce xylo-oligosaccharides (XOS). In stage 2, the solid residue isolated from stage 1 was further hydrolyzed by cellulase and β-glucosidase. NaOH, Na2CO3, and Ca(OH)2 were tested to remove acetyl groups in the process of deacetylation, and it was found that Ca(OH)2 could be the most suitable alkali for deacetylation in this work. After deacetylation using 0.8 mmol of Ca(OH)2/g of substrate and PFI refining, 50.5% xylan in the raw material could be hydrolyzed into XOS. The corresponding xylan yield of stage 1, the glucan yield of stage 2, and the total sugar yield (all sugars released in the hydrolyzate) after the two-stage enzymatic hydrolysis were 0.306, 0.305, and 0.661 g/g of corn cob, respectively.

Production of furfural from waste aqueous hemicellulose solution of hardwood over ZSM-5 zeolite

This study aimed to produce furfural from waste aqueous hemicellulose solution of a hardwood kraft-based dissolving pulp production processing in a green method. The maximum furfural yield of 82.4% and the xylose conversion of 96.8% were achieved at 463K, 1.0g ZSM-5, 1.05g NaCl and organic solvent-to-aqueous phase ratio of 30:15 (V/V) for 3h. The furfural yield was just 51.5% when the same concentration of pure xylose solution was used. Under the optimized condition, furfural yield was still up to 67.1% even after the fifth reused of catalyst. Catalyst recycling study showed that ZSM-5 has a certain stability and can be efficiently reused.

Quantitative characterization of the impact of pulp refining on enzymatic saccharification of the alkaline pretreated corn stover

In this work, corn stover was refined by a pulp refining instrument (PFI refiner) after NaOH pretreatment under varied conditions. The quantitative characterization of the influence of PFI refining on enzymatic hydrolysis was studied, and it was proved that the enhancement of enzymatic saccharification by PFI refining of the pretreated corn stover was largely due to the significant increment of porosity of substrates and the reduction of cellulose crystallinity. Furthermore, a linear relationship between beating degree and final total sugar yields was found, and a simple way to predict the final total sugar yields by easily testing the beating degree of PFI refined corn stover was established. Therefore, this paper provided the possibility and feasibility for easily monitoring the fermentable sugar production by the simple test of beating degree, and this will be of significant importance for the monitoring and controlling of industrial production in the future.

Optimization of Alkaline Sulfite Pretreatment and Comparative Study with Sodium Hydroxide Pretreatment for Improving Enzymatic Digestibility of Corn Stover

In this study, alkaline sulfite pretreatment of corn stover was optimized. The influences of pretreatments on solid yield, delignification, and carbohydrate recovery under different pretreatment conditions and subsequent enzymatic hydrolysis were investigated. The effect of pretreatment was evaluated by enzymatic hydrolysis efficiency and the total sugar yield. The optimum pretreatment conditions were obtained, as follows: the total titratable alkali (TTA) of 12%, liquid/solid ratio of 6:1, temperature of 140 °C, and holding time of 20 min. Under those conditions, the solid yield was 55.24%, and the removal of lignin was 82.68%. Enzymatic hydrolysis rates of glucan and xylan for pretreated corn stover were 85.38% and 70.36%, and the total sugar yield was 74.73% at cellulase loading of 20 FPU/g and β-glucosidase loading of 10 IU/g for 48 h. Compared with sodium hydroxide pretreatment with the same amount of total titratable alkali, the total sugar yield was raised by about 10.43%. Additionally, the corn stover pretreated under the optimum pretreatment conditions was beaten by PFI at 1500 revolutions. After beating, enzymatic hydrolysis rates of glucan and xylan were 89.74% and 74.06%, and the total sugar yield was 78.58% at the same enzymatic hydrolysis conditions. Compared with 1500 rpm of PFI beating after sodium pretreatment with the same amount of total titratable alkali, the total sugar yield was raised by about 14.05%.

Effects of Extraction Methods on Structure and Valorization of Corn Stover Lignin by a Pd/C Catalyst

With the significant development of efficient pretreatments of lignocellulosic biomass towards using carbohydrate compositions for biofuel production, the valorization of associated lignin products into valuable chemicals has gained much attention. Four lignins obtained by pretreatment of corn stover with emerging ionic liquid‐based mixed organic electrolytes (ILOE) and alkaline twin‐screw extrusion (ATSE) pretreatment technologies were characterized by gel permeation chromatography (GPC), FTIR, HSQC, 31P NMR spectroscopy, and SEM. These lignins were valorized by using Pd/C under various conditions, followed by an elucidation of the relationship between the lignin structure and valorization efficiency and selectivity. The pretreatment/separation methods have a significant effect on lignin structure and subsequent valorization efficiency. HSQC spectra revealed that corn stover lignin consisted of β‐O‐4, β‐5, β‐1 linkages, and cinnamyl alcohol end groups. The extracted lignins (EL) showed less carbohydrates and β‐O‐4 units than those of enzymatic hydrolytic lignins (EHL). The yields of bio‐oils were 61.7 % and 57.9 % for ATSE‐EL and ILOE‐EL, and 34.2 % and 45.1 % for ATSE‐EHL and ILOE‐EHL under optimal and comparative conditions, respectively. Part of the syringyl (S) units were converted into guaiacyl or p‐hydroxyphenyl (H) units by release of methoxyl groups on the aromatic ring through hydrogenolysis, which led to a decreased proportion of S units and an increased proportion of H units in oil compared with in lignin.

Preparation and characterization of antibacterial paper coated with sodium lignosulfonate stabilized ZnO nanoparticles

We report a simple method to synthesize spherical and irregular sodium lignosulfonate (SLS)-stabilized zinc oxide (ZnO) nanoparticles using water as a solvent, SLS as a stabilizing agent, and sodium hydroxide as a precipitation agent. The presence of SLS on the surface of ZnO nanoparticles can improve the dispersion of the nanoparticles and make them negatively charged. The negatively charged SLS-stabilized ZnO nanoparticles can be deposited onto cellulose paper through a layer-by-layer (LBL) approach. The resultant cellulose paper samples, coated with ZnO nanoparticles, show good antibacterial activity against both Gram-positive Bacillus subtilis and Gram-negative Escherichia coli.