Study On The Removal Of Cadmium In Micro-polluted Source Water By Zeolite Filter Loaded Chitosan

In order to remove cadmium in micro-polluted source water, the zeolite filter wasprepared by modified, shaping and cacined. The effects of adhesive, calcinationstemperature and time on the hardness and removal capable of the filter wereinvestigated. The results show that when the dosage of the attapulgite reached1/8ofzeolite, the filter calcined1h at500°C, its strength can meet the requirements ofapplication; the removing effect of cadmium will decline when calcined temperatureis too high. This filter is impregnated in chitosan-acctate solution to prepare a newzeolite filter which loaded chitosan,1%concentration of the chitosan-acctate solutionwill significantly improve the removing effect of cadmium.The characterization of the natural zeolite, the zeolite filter and the zeolite filterloaded chitosan were analysis by surface area analyzer, SEM, XRD and FTIR.Compare with the natural zeolite, the quantity of the mesopores and macropores isincreased and the pore size distribution range becomes large, BET ratio surface area,average pore diameter and total pore volume are increased too. The surface of zeolitefilter appear porous and the zeolite filter loaded chitosan covered with the filaments.The crystal structure of zeolite filter is more significant, while impurity content isreduce, the characteristic peaks of chitosan appears in the XRD pattern of zeolite filterloaded chitosan. Water molecules are evaporated from the zeolite filter, the FTIRpattern of zeolite filter loaded chitosan contains the vibrational band of-NH2and-CH3, which is the further evidence of the presence of chitosan.The adsorptive properties and the desorption of these zeolite materials in staticadsorption is investigated under different situation.The results show that, comparedwith the natural zeolite and the zeolite filter, the rate and capable of adsorption of thezeolite filter loaded chitosan are faster; higher pH is conducive to the removal ofcadmium;2mol/L calcium chloride solution can preferably reach the desorption rateof96.5%. They are in line with the Freundlich isotherm adsorption model and thetheoretical and the adsorption capacity of the zeolite filter loaded chitosan is the best,the three adsorption kinetics process in line with the Lagergren second-order rate equation, the adsorption rate is controlled by the liquid film diffusion process.The zeolite filter loaded chitosan is applied to the dynamic adsorption to removecadmium, the effects of the filtration rate, cadmium concentration and thickness of thefilter bed on the breakthrough curves were investigated. The results showed that thelower velocity and concentration, the greater thickness of the filter bed is, the filter isharder to be breakthrough, and compared with the static adsorption, the dynamicadsorption capacity can be significantly improved. When the cadmium ionconcentration is25μg/L, the filtration speed is10m/h, the height of the filter bed is300mm, the effluent concentration of cadmium can meet drinking water standards(GB5749-2006) in17h.