Application Of Ultrafiltration And Electrochemical Technology In Metallurgy And Hydrolysis Of Biomass

Today more and more attentions on environmental protection, use of renewable resources and treatment of wastewater are paid. One of the problems is to utilize biomass. The biomass resources are rich in China, but rather limited used. For exemple, corn stem, much of this material is disposed by burning, which results in environmental pollution. Biomass consists mainly of cellulose, hemicellulose and lignin. Xylan extractived from corncob can be utilized to produce xylooligosaccharides. Also, pretreatment, enzymatic hydrolysis and fermentation of corn stem can be used to produce fuel ethanol, reaching renewable resource and environmental protection. Therefore, the present study on hydrolysis of biomass and treatment of wastewater with ultraflltration and electrochemical technology is very important. In this dissertation, a review has been made systematically on the field of membrane separation technique and the treatment of organic pollutants in water by electrochemical oxidation. The solvent flux of the ultraflltration of xylan extractives, coupling of ultraflltration technique and enzymatic hydrolysis of xylan, recovery of cellulase and purifying of nickel-containing electroplating wastewater by ultraflltration technique, and treatment of xylan desalting effluent with electrochemical method have been studied.As a new separation technique, ultraflltration can solve sach problems as high cost and low efficiency to conventional ion-exchange. It is found that increasing in the solvent flux was with increasing transmembrane pressure, and there exists a limiting flux at some transmembrane pressure. A membrane model has been applied to explain the limiting flux and relations between solvent flux and xylan concentration. The technique has been used in industry production.Recovery of cellulase with ultraflltration technique was also studied.The optimum conditions of cellulase obtained by ultrafiltration technique and enzymatic hydrolysis were determined. Based on the experment, a new way for production of fuel ethanol from corn stem was proposed.The effect of coupling the reactor processes with membrane units was studied. It is shown that the coupling could enhance the selectivity and conversion of reaction, or keep high reaction rate by removing the toxic parts which effect on reaction. The effects of variety of conditions on the enzymatic hydrolysis of xylan were studied in the coupling of ultrafiltration technique and enzymatic hydrolysis of xylan. The optimum conditions of enzymatic hydrolytes of xylan were obtained. A comparison of the results on enzymatic hydrolysis with the conventional reactor is made. In order to enhance the extent of renewable resource and the purity of products, the effect of coupling of ultrafiltration technique and enzymatic hydrolysis of xylan was studied. It is indicated that the ratio of xylooligosaccharides to total sugar was related with the operating condition and the mode of feed. Therefore, enzymatic hydrolysis of xylan using the purified xylanases decreases greatly xylose in the yield, the ratio of xylooligosaccharides to total sugar being up to 0.99.Ultrafiltration technology was also studied for treatment of the nickel-containing wastewater, which is advantage over the conventional technology, not only in purifying wastewater, but also indirect recovery of NiCl2, decreasing in discharge of pollution.Electrochemical treatment of xylan desalting effluent can make chroma, CODcr and BOD5 of the wastewater meet the requirement of the discharge standard. The mechanism of electrochemical oxidation was discussed.