Shuangxi Nie

Surface characterization and chemical analysis of bamboo substrates pretreated by alkali hydrogen peroxide.

The surface characterization and chemical analysis of bamboo substrates by alkali hydrogen peroxide pretreatment (AHPP) were investigated in this study. The results tended to manifest that AHPP prior to enzymatic and chemical treatment was potential for improving accessibility and reactivity of bamboo substrates. The inorganic components, organic solvent extractives and acid-soluble lignin were effectively removed by AHPP. X-ray photoelectron spectroscopy (XPS) analysis indicated that the surface of bamboo chips had less lignin but more carbohydrate after pre-treatment. Fiber surfaces became etched and collapsed, and more pores and debris on the substrate surface were observed with Scanning Electron Microscopy (SEM). Brenauer-Emmett-Teller (BET) results showed that both of pore volume and surface area were increased after AHPP. Although XRD analysis showed that AHPP led to relatively higher crystallinity, pre-extraction could overall enhance the accessibility of enzymes and chemicals into the bamboo structure.

Removal of hexenuronic acid by xylanase to reduce adsorbable organic halides formation in chlorine dioxide bleaching of bagasse pulp.

Xylanase-aided chlorine dioxide bleaching of bagasse pulp was investigated. The pulp was pretreated with xylanase and followed a chlorine dioxide bleaching stage. The ATR-FTIR and XPS were employed to determine the surface chemistry of the control pulp, xylanase treated and chlorine dioxide treated pulps. The hexenuronic acid (HexA) could obviously be reduced after xylanase pretreatment, and the adsorbable organic halides (AOX) were reduced after chlorine dioxide bleaching. Compared to the control pulp, AOX could be reduced by 21.4-26.6% with xylanase treatment. Chlorine dioxide demand could be reduced by 12.5-22% to achieve the same brightness. The ATR-FTIR and XPS results showed that lignin and hemicellulose (mainly HexA) were the main source for AOX formation. Xylanase pretreatment could remove HexA and expose more lignin, which decreased the chlorine dioxide demand and thus reduced formation of AOX.

Efficient extraction of bagasse hemicelluloses and characterization of solid remainder

To reduce the degradation of cellulose and obtain high molecular weight of hemicellulose from the extracts, pH pre-corrected hot water pretreatment was developed by employing sodium hydroxide (3.9mol/L). The response surface model was established to optimize the extraction process. The species composition and purity of hemicellulose extract was analyzed by High Performance Liquid Chromatography (HPLC). The obtained solid remainder was analyzed by FTIR and SEM. The results showed that the component of xylose in hemicellulose extract was similar with commercial xylan. FTIR and SEM were shown to be able to evaluate solid remainder composition and surface characterization of the bagasse. The biggest balance between solid remainder and dissolved solid was obtained. Not only the yield of dissolved solid was improved, but the structure of solid remainder was also proved, which was beneficial to pulping and papermaking.

Enzymatic pretreatment for the improvement of dispersion and film properties of cellulose nanofibrils

In the present study, cellulose nanofibrils (CNF) were produced from unbleached eucalyptus pulp, and the effect of enzymatic treatment on the properties of CNF was studied. Moreover, the mechanism of enzymatic treatment on the dispersion and film properties of CNF was speculated. The xylanase pretreatment facilitated the deconstruction of pulp into CNF via mechanical shearing and high-pressure homogenization, while the hemicellulose composition was preserved. Compared to the control, the CNF suspensions made from the xylanase pretreated pulp were more crystalline with higher dispersion, optical and rheological properties. CNF films were produced with a vacuum filtration process. The optical and mechanical strength properties of the CNF films were improved by the removal of hemicellulose. It was found that the carboxyl and hydroxyl groups played key roles in affecting the dispersion and film properties of the CNF. The carboxyl group content increased after the enzymatic pretreatment, which benefits the even distribution of CNF in water. The mechanical strength of the CNF films was further improved by exposing the hydroxyl group when lignin-carbohydrate complexes were de-structured by the enzymes. This study expanded the application of CNF produced from unbleached pulp. The theoretical foundation for stabilizing the CNF suspension and the high-speed dehydration of CNF films were explored for the continuous roll to roll production of CNF film.

Enzyme-assisted mechanical production of microfibrillated cellulose from Northern Bleached Softwood Kraft pulp

This paper examines the mechanism of an enzyme pre-treatment on mechanical preparation of microfibrillated cellulose (MFC), the effects of hemicellulase and cellulase, on enhancing of the PFI refining efficiency of Northern Bleached Softwood Kraft pulp for fiber’s devillicate, and changing of morphologies and physical characteristics on fibers, such as specific surface area were investigated, respectively. It was revealed that the enzyme pre-treatment could promote (1) an acceleration of fine productivity from the fibers, (2) intensive reduction of the size of the fibers through mechanical cutting and (or) fibrillation, and (3) energy efficiency in the reduction of fiber length without productivity impairment. However, distinct mechanical actions on the fibers pre-treated with hemicellulase and cellulase were indicated, according to the dissimilar fibrillation patterns and morphological properties found in the MFC product through intensive mechanical refining.

Effect of hot chlorine dioxide delignification on AOX in bagasse pulp wastewater

This work describes the effect of the hot chlorine dioxide delignification (DHT) on the properties of bagasse fiber and the formation of AOX. The bagasse pulp was subjected to both DHT and normal temperature chlorine dioxide delignification (D0), and the AOX contents in the effluent were determined respectively. The GC–MS results showed that the main components of the D0 stage wastewater were chlorinated hydrocarbons and chlorinated diphenyls. In contrast, those AOXs in the DHT stage wastewater were very few. The GC–MS, ATR-FTIR, and XPS results showed the DHT process is more effective in the removal of the residual phenolic lignin and the hemicellulose-linked HexA compared with D0. Furthermore, in comparison, the AOX content could be reduced by 50% with DHT. The fully bleached pulp obtained via DHTEpD process has a higher brightness than that obtained by D0EpD, which provides a reliable theoretical basis for industrial application.

Facile synthesis of a molybdenum phosphide (MoP) nanocomposite Pt support for high performance methanol oxidation

Metal phosphides are of great recent interest as promoters to precious metal-driven catalytic oxidation of alcohols in direct alcohol fuel cells. In this work, a novel approach for facile and environmentally friendly synthesis of molybdenum phosphide (MoP) nanocrystals anchored on graphitized carbon is developed by one-step pyrolysis of a phosphorus-containing resin exchanged with Mo5+. A significant promotion effect of MoP on Pt in methanol electrooxidation is observed. The Pt–MoP/C catalyst exhibits ultrahigh electroactivity, and compared to commercial Pt/C, this catalyst reaches a −140 mV more negative onset potential and has 10 times the mass activity at 0.4 V vs. SCE and 5.1 times the peak mass activity. In addition, Pt–MoP/C has also excellent stability and CO tolerance, including a peak mass activity retention of 81.4% after 1000 cycles as compared to that of 51.6% on commercial Pt/C and a 140 mV more negative COad oxidation potential. The noteworthy promotion effect of MoP on Pt in methanol electrooxidation is also evaluated by theoretical calculations.