Preparation Of Oligomeric Chitosan And Its Application In Wastewater Treatment

In this paper, firstly the chitin and chitosan are introduced, and summarized on chitosan oligosaccharide physical, chemical and biological properties, preparation method and ways of application research in recent years at home and abroad. Then the research status of sewage treatment additives is introduced at home and abroad.Industrial grade chitosan was selected as raw material and collaborative oxidative degradation method of HAc-H2O2 was used, in order to study the effects of reaction time, dosage, reaction temperature, concentration of hydrogen peroxide and acetic acid on the reaction. The optimal degradation conditions obtained by single factor experiment were as follows: reaction time was 3h, dosage of chitosan was 8%, reaction temperature was 90℃, concentrations of hydrogen peroxide and acetic acid were 10% and 2%, respectively. Under these conditions, the yield, viscosity, and degree of deacetylation were 59.70%, 2.3mPa·s and 89.05%. A set of L16(45) orthogonal experiment was also designed, using R analysis of each index of the most important impact factors. The results were as follows: acetic acid concentration was the most important impact factor for the yield and degree of deacetylation, and the most important impact factor for the temperature was reaction time. The optimum reaction conditions for the preparation of high yield, low viscosity and high deacetylation degree of chitosan oligosaccharide through comprehensive balance analysis method were as follows: the reaction time was 4h, chitosan dosage was 6%, reaction temperature was 100 ℃, concentrations of hydrogen peroxide and acetic acid were 10% and 4%, respectively, which was a scientific reference to the industrialized production of chitosan oligosaccharide by using industrial grade chitosan as raw material.Fourier transform infrared spectroscopy(FTIR), X-ray diffraction and scanning electron microscope(SEM) were used for the characteristic analysis of products. By comparing the characteristics of the peak, it was found that the original molecular structure unit and biological activity ofproduct were maintained after degradation, though its molecular weight decreased. Through X-ray diffraction, it was proved that the ability to crystallize and hydrogen bonding between molecules were both weakened, and crystal grains were smaller. The latter was also observed through SEM.The best reaction conditions for the treatment of ferrous ion rich wastewater by using chitosan products after degradationwere also researched, and the results were as follows. Flocculation time was 40 min, reaction temperature was 30 ℃, pH value was 5, chitosan oligosaccharide dosagewas 2g/L. Under these conditions, adsorption capacity of Fe2+was397.81mg/g.