Preparation Of Novel Amphoteric Chitosan Derivative And Interaction With Dye Wastewater

The carboxymethyl-polyaminate chitosan (DETA-CMCHS), which not only held non-toxic and harmless, biodegradability characteristics of chitosan, but also had better water-solubility and extensive application domain, were derived from chitosan. In this thesis, the interactive relationship between carboxymethyl-polyaminate chitosan (DETA-CMCHS) and simulated dye solution, mixed two kinds of dye solution, actual dyeing wastewater had been studied, which in order to provide theoretical guidance to the practical application.1. The preparation of amphoteric chitosan derivative carboxymethyl-polyaminate chitosan: DMSO was used as Non-proton solvent in place of literature commonly used isopropyl alcohol. Chitosan was reacted with chloroacetic acid in alkaline to get carboxymethyl chitosan (CMCHS) and then cross-linked by epichlorohydrin and amine modificated by diethylenetriamine. So the resulting amphoteric chitosan derivative contained both carboxyl and relatively high amine groups. The optimal conditions of carboxymethylation, crosslinking, amine reaction were investigated. The structure of DETA-CMCHS was characterized by elemental analysis, IR and 1HNMR. Results showed that: Carboxymethyl and amine degrees of DETA-CMCHS are 1.39 and 0.71 respectively computed by elemental analysis. IR and 1HNMR can show that carboxymethyl-polyaminated reaction have been taken place.2. The interactive relationship between DETA-CMCHS and single dye solution: Effects of different pH and adsorbent dosage on decolorization rate and adsorption capacities of reactive blue (RB2) and reactive yellow (RY86) were discussed and adsorption kinetics, thermodynamics and adsorption balance of single dye solution were investigated under different initial conditions. Results were shown as following: (1) Adsorption capacities of both two dyes on DETA-CMCHS was up to the largest at pH = 3; (2) The adsorption capacities and decolorization rate of two dyes are not proportional, an increase in adsorption dosage leads to a decrease in adsorption capacities and an increase in decolorization rate; (3) The adsorption of reactive blue (RB2) and reactive yellow (RY86) on DETA-CMCHS fit well with pseudo second-order kinetic model, the rate-limiting step of the chemical adsorption mainly controlled by electrostatic force; (4) The equilibrium adsorption data have a better correlation with Langmuir and Freundlich isotherm; (5) The adsorption of two dyes on DETA-CMCHS is spontaneous and irreversible exothermic process. 3. The relationship between DETA-CMCHS and mixed two dyes solution: the adsorption kinetics and adsorption equilibrium of the two dyes in the same and different addition sequence were studied. Results were shown as following: (1) An increase in another dye concentration leads to a decrease in one dye adsorption and the decrease in adsorption capacity of reactive Yellow (RY86) was more evident in case of fixed one dye concentration and the same or different addition sequence of another dye; (2) adsorption capacity and competitive coefficient of the first dye in addition the first dye is higher than in addition the second dye first, and the extent was increased with the initial concentrations of reactive blue (RB2) and reactive yellow (RY86) increased, the impact on reactive blue (RB2) is more obvious; (3) the competitive adsorption isotherm of two kinds of dye on DETA-CMCHS has a better correlation with Langmuir isotherm.4. The relationship between DETA-CMCHS and actual dyeing wastewater: Orthogonal experiments for treatment of dyeing wastewater by DETA-CMCHS were studied, the wastewater pollutant removal performance of CTS, CMCHS and DETA-CMCHS were compared, the effects of different initial conditions on wastewater chemical oxygen demand (COD), adsorption degradation kinetics and adsorption thermodynamics of dyeing wastewater were investigated. Results were shown as following: (1) The optimum conditions of decolorization and COD removal rate: pH = 2, 90 mL wastewater volume, 40 min stirring time, 160 mg/L adsorbent dosage; (2) The sequence of decolorization and COD removal rate is DETA-CMCHS> CMCHS> CTS at different pH; (3) COD degradation kinetic data are consistent with pseudo-first-order kinetic model under different pH and ionic strength; (4) Adsorption equilibrium data can be used Langmuir and Freundlich isotherms to describe; (5) The adsorption of wastewater on DETA-CMCHS is an exothermic process, and the increase in temperature and initial COD concentration are not conducive to adsorption.