بررسي ميزان حذف كادميوم از آب به وسيله كربن فعال دانه اي GAC

Study on water cadmium decontaminetion by granular activated carbon (GAC)

Background and purpose: Cadmium is one of the toxic elements which contaminate water resources through industrial, domestic, agricultural effluents and un hygienic burdening of industrial and urban waste materials. Studies shows that surface and subsurface waters in some areas near to the pollutant sources arc contaminated with cadmium 0.1 to 1.0 mg/l. No study has been done about omiting the low concentrations of cadmium ( present in the contaminated resources) with the help of activated carbon, determination of isotherms and the influencing factors on it. The aim of this study was to determine cadmium absorption isotherm on activated granular carbon GAC, and also determine the effect of temperature and water pH on absorption isothenns. And finally determine the rate of efficacy of using activated carbon column in omition of cadmium from water. Materials and methods: Certain weights of activated carbon (0.05-0.07 gram) were added seperately to 250 ml of water with certain concentration of cadmium present in flask and pH was adjested, the flasks were kept in refrigerated incubater equiped with shaker, temperature was edjusted. In order to determine the time equilibrium of abserption, the flasks were shaked with duration of 30 minutes to 6 hours in incubator. At each time interval the concentration remained cadmium in solution after filtration of the samples were measured according to the standard by atomic absorption mwthod. With the help of data concerning experiments on determination of isotherms, synthetic of cadmium absorption on sctivated carbon, the effect of activated carbon on the speed of absorption, effect of initial cadmium concetration on coefficient of absorption. As well as the effect of temperature changes and pH on isotherms was determined. The rate of cadmium absorption on activated carbon column at work conditions, was comared with the expected rate on isotherm. Break through curves related to cadmium containing water for concontration of D.26 mg/L. for at the of EBCT for 30 minuts and for the Concentration of 0.59 mg/Li for at two contact time of 30 and 60 minuts were plotted. Results : The rate of cadmium absorption on activted carbon increased with increasing in pH and temperature. Though by increasing initial concentration of cadmium the rate of its absorption on Unit Weight of autivated carbon(9) increased. But removing efficiency Certain amount of activated Caobon declined. Cadmium absorption on activated Carbon Fllew the first order of kinetic. By increasing the rate of cutivated Carbon, absorption of Cadmium increased. For Concentration of of Cadmium, the break through offer passing water was 55 folds more on bed volume and for Coccntration of 0.59 mg/Lifor after Passing was 40 fold of volume accured The rate of Cadmium uptake on Column of Gac was more than the expected rate of isotherm. Conclusion: Though Complate removal of 0.26 mg/Lifor and 0.59 mg/Lifor of Cadmium of water through activated Carbon column is possible. But the break through in the plot related to the performance of the Column is partially happens soon.