Preparation Of Modified Chitosan Microspheres And Its Adsorption Of Methyl Orange In Dyeing Wastewater

Dyeing wastewater with high organic content, complicated water quality, highly toxic, and high color and other characteristics, will cause serious environmental pollution if it is discharged directly to the environment. As a natural polymeric flocculant, chitosan not only has strong adsorption capacity for dye molecules, but also has good biocompatibility, biodegradable and antibacterial properties. However, chitosan is difficult to be separated from an aqueous solution after treatment of wastewater, as well as easily soluble in an acidic solution. These drawbacks limit its application in treatment of dyeing wastewater. In order to improve the separation efficiency and enhance its acid resistance, chitosan microspheres modified by quaternary ammonium and hyperbranched polyamide were prepared. And the adsorption properties and adsorption kinetics of these two microspheres for methyl orange in simulated dyeing wastewater were systematically studied. The details are as follows:(1) Grafting of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride onto chitosan chains, chitosan modified by quaternary ammonium salt(HTCC) was prepared. Then, chitosan microspheres modified by quaternary ammonium salt(Q-HTCC) were successfully prepared by using emulasion crosslinking method with HTCC. Scanning electron microscope(SEM) showed that these prepared microspheres had smooth surface and preferably spherical shape. And particle size analysis showed that the diameter of Q-HTCC was range from 5 to 48 μm.(2) The simulated dyeing wastewater containing methyl orange were processed by chitosan, HTCC and Q-HTCC respectively. The effect of pH of wastewater, the adsorption of time, the mount of microspheres, the initial concentration of methyl orange, temperature and speed on the adsorption properties were systematically investigated. The results showed that colour removal of methyl orange by Q-HTCC was obove 93% when pH between 2.92 ~ 10.55. Colour removal of methyl orange: Q-HTCC(99.57%) > HTCC(93.04%)> chitosan powder(23.17%). The study of adsorption kinetics showed adsorption isotherm curves of methyl orange by Q-HTCC fit Freundlich equation, it was revealed that the behavior of adsorption was belongs to multilayer adsorption.(3) The hyperbranhced polyamides(HBPE) were synthesized by using 1, 3, 5-benzenetricarboxylic acid and ethylenediamine. Then their chemical structures were characterized with FT-IR, 1H NMR and 13 C NMR. Thermal gravimetric analysis(TG) showed that HBPE had good themal stability. Gel permeation chromatography(GPC) showed that the average molecular weight and polydispersity index of HBPE that was synthesized by using optimum conditions, were 4.3 × 104 and 1.59 respectively.(4) HBPE-CS was prepared by grafting HBPE onto chitosan chains, which was determined by FT-IR and 1H NMR. GPC showed that the average molecular weight and polydispersity index of HBPE-CS were 5.1 × 104 and 9.33 respectively. Q-HBPE-CS was futher prepared by using emulasion crosslinking method with HBPE-CS. In adsorption tests for methyl orange, colour removal: Q-HBPE-CS(99.78%) > HBPE-CS(72.57%)> chitosan powder(23.17%). These results showed that Q-HBPE-CS had better adsorption property for methyl orange than HBPE-CS and chitosan at same conditions...