Shuangfei Wang

Anaerobic biological treatment of high strength cassava starch wastewater in a new type up-flow multistage anaerobic reactor

Anaerobic treatment of cassava starch wastewater using an up-flow multistage anaerobic reactor was investigated. The results showed that startup was successfully accomplished in 22d. The maximum 87.9% chemical oxygen demand (COD) was removed at hydraulic retention time (HRT) of 6.0 h at fixed concentration 4000 mg/L. In addition, 77.5-92.0% COD were removed as organic loading rates at 10.2-40.0 kg COD/(m(3) d) at fixed HRT of 6.0 h. The Grau second-order kinetic model and modified Stover-Kincannon model were successfully used to develop a kinetic model of the experimental data. Furthermore, the specific methanogenic activity were 0.31 and .73 g COD(CH(4))/(g VSS d) for the first and second feed, respectively. Finally, morphological examination of the sludge revealed Methanothrix spp. and Methanosarcina spp. were dominant microorganisms. All the results indicated that the UMAR could be used efficiently for treatment of wastewater containing high COD concentration from cassava starch processing.

A kinetic model for oxidative degradation of bagasse pulp fiber by sodium periodate.

In this paper, some key parameters, such as the system pH, the periodate concentration, and the reaction temperature, on the influence of the bagasse fiber degradation were studied based on the oxygenant of periodate. And the feasible reaction mechanism was also discussed through the FTIR characterization for bagasse fiber before and after the oxidizing reaction. As the results shown, the crystallinity of bagasse fiber decreased with the oxidation level increasing. It was interesting that the aldehyde content of the reaction system rose gradually along with cellulose degradation. Based on this result, the selective oxidation kinetics was constructed by introducing of variable factor R (the ratio of aldehyde content to the degradation of cellulose fiber), and the results shown that there was a better correlation between the dynamic model and the experimental data, so the oxidation degree of bagasse fiber oxidized by periodate can be quantitative evaluated based on this model.

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.

Modification of eucalyptus CTMP fibres with white-rot fungus Trametes hirsute - Effects on fibre morphology and paper physical strengths.

White-rot fungus Trameteshirsute (T.h. 19-6) was used for modifying the eucalyptus CTMP fibres. Results show that the T.h. 19-6 removed mainly lignin (by 7.42%) and extractive (by 11.52%) after a short period of 5days incubation. Due to the fungal degradation of the fibre wall materials, the middle lamella remainder on the fibre surface was significantly reduced and the fibre wall structure was loosened, which led to an increase in fibre internal bonding strength by 32% and an increase in handsheet tensile index and tear index by 49%, and 34%, respectively. A subsequent PFI refining process further amplified the fungal treatment effect, resulting in extensive fibre internal fibrillation. Compared with untreated pulp, fungus-treated pulp reached the same freeness levels with less PFI revolutions, indicating potential energy saving in the refining process.

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.

Acetylation improves thermal stability and transmittance in FOLED substrates based on nanocellulose films

Bleached softwood pulp was used to prepare nanofibrillated cellulose (NFC) by mechanical grinding and a high-pressure homogenization process. Acetylation improved the aspect ratio and dispersion of the NFC; however, highly acetylated NFC was not able to form a film by vacuum filtration if the NFC : acetic anhydride (AA) ratio was greater than 1 : 6. An NFC film prepared by acetylated NFC has potential as a flexible organic light-emitting device (FOLED) substrate. Acetylation improved the thermal stability and transmittance of NFC films, which were optimal at 5.43 ppm K−1 and 65%, respectively, when the ratio of NFC : AA was 1 : 3. Moreover, both the mechanical properties and flexibility of the NFC films were well maintained when the NFC : AA ratio was 1 : 3. Additionally, all NFC films prepared by acetylated NFC were smooth, flat, and uniform.

The influence of mechanical refining treatments on the rheosedimentation properties of bleached softwood pulp suspensions

To study the effect of mechanical treatments on the rheosedimentation behaviour of pulp fiber suspensions, the settling behaviour, gel point, compressive yield stress and hindered settling function of bleached softwood pulp with different beating degrees at low concentrations were investigated. Over the range of test concentrations, it was found that the settling rates for refined softwood pulps were slower than that without mechanical treatments, and the values of gel points increased approximately linearly with freeness; Both the compressive yield stresses and hindered settling functions of all pulp suspensions increased non-linearly with increasing crowding number, and the hindered settling function was found to be dependent on the crowding number through a power law relationship. Moreover, the compressive yield stresses for softwood pulp suspensions with mechanical treatment were higher than that without refining. However, the same tendency for hindered settling functions was observed only for suspension at crowding number more than 16. The rheosedimentation studies on softwood pulp suspensions revealed that fiber morphology has a great influence on the settling and compressive behaviour.

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.