Synthesis And Application Of Graft Copolymerization Of AM And DMAEMA Onto CTS Using Ammonium Persulfate

With industrial development, a large number of heavy metal ions in wastewater are discharged to the water environment which causes some certain hazards to the environment. Conventional sewage treatment methods are subject to many restrictions, such as the high cost of adsorbent (Functional Polymers), the investment and operating costs run high in the membrane separation project, the level of technology can not meet water quality standards, and will cause secondary pollution. In resent years, the researches of some polymer treatment agents, which have special selectivity and strong chelating ability, are getting hotter and hotter. Natural polymer chitosan contains amino and hydroxyl on its molecular structure, which can form coordination bond, so it has a strong chelate ability to the metal ions. Researchers have been paying attention to this area, and some modified products have been applied to deal with heavy metals in wastewater.1) In this article, with ammonium sulfate as initiator,the graf-copolymerization derivative of acrylamide(AM) and N,N-Diethylaminoethyl methacrylate (DMAEMA) on chitosan(CTS) is prepared. The grafting percentage relate to the different reaction conditions (initiator concentration, monomer amount, reaction time, reaction temperature, the time of the monomer dropwise and the proportion of ammonium persulfate and sodium bisulfite). We have considered the grafting ratio and grafting efficiency to get the best reaction conditions by uniform design. The results are as follows: the optimum ratio of DMAEMA in the monomer is 10%, the best ratio of chitosan and monomer is 1:6, the concentrations of initiator is 2mmol/L, the reaction temperature is 50℃, the monomer (DMAEMA) for dropping time is 1h, the reaction time is 1h.2)The structure of products are characterized by the IR,SEM and XRD, Changes in the group of characteristic absorption peaks, the diffraction peaks and the surface structure showing that the acrylamide and N, N-Diethylaminoethyl methacrylate have been successfully grafted to the main chain of the chitosan molecules. 3)The adsorption performance of the chitosan graft copolymer to the Hg²⁺,Cr⁶⁺,Cu²⁺,Pb²⁺ and Cd²⁺ are studied by the single-factor test method. The effect of the adsorption conditions (the synthesis conditions of the chitosan graft copolymer, the amount of adsorbent, metal ion concentration, adsorption time and pH value of solution etc) to the removal of metal ions and the absorption capacity to the metal ions are researched. The conclusions are as follows:â‘ in the same conditions, compared with the ordinary chitosan, the adsorption effects of the 2nd, the 12th and the 18th of chitosan graft copolymer have significantly enhanced, separately to the Pb²⁺, Hg²⁺and Cr⁶⁺, the adsorption capacity increases 56.31,36.19 and 26.87mg / g than chitosan.â‘¡Heavy metal removal rate with the increase in adsorbent dosage increased, when the removal rate to the heavy metals ions Hg²⁺,Cr⁶⁺,Cu²⁺,Pb²⁺ and Cd²⁺ reach the highest, its required the amount of modified chitosan sorbents as follows: 0.3g / L, 2.5g / L, 1.5g / L, 0.5g / L and 1.5g / L.â‘¢the adsorption isotherm curve show that the adsorption behavior of modified chitosan to Hg²⁺,Cr⁶⁺,Pb²⁺ and Cd²⁺ are in line with the Langmuir model and the Freundlich model, the adsorption of Cu²⁺ only in line with the Langmuir model; the adsorption of Hg²⁺,Cu²⁺,Pb²⁺ and Cd²⁺ is mainly physical adsorption, and the adsorption of Cr⁶⁺ is mainly chemical adsorption.â‘£The adsorption kinetics show that the modified chitosan have the largest adsorption rate to Cr⁶⁺ , adsorption of Cu²⁺ on the rate of the second, and Hg²⁺ is the smallest, all of them are in line with the second-order reaction kinetics.⑤the solution pH value impact the adsorption effect of adsorbent. The best adsorption pH value is 5.5 to Hg²⁺, Pb²⁺; 3, 4 and 5 to Cr⁶⁺, Cu²⁺, Cd²⁺ respectively.â‘¥In the four mixed systems of the Hg²⁺-Cu²⁺-Pb²⁺-Cd²⁺, the adsorption capacity of the 2nd and the 14th of chitosan graft copolymer can adsorb the Cu²⁺ selectively, and the 2nd adsorbent hardly absorb the Cd²⁺.The 12th adsorbent can selectively adsorbed Hg²⁺.