Separation Science and Technology, Vol.38, No.9, 2003-2024, 2003
Cadmium decontamination from aqueous media using lateritic minerals
In this study, lateritic minerals were exploited to evaluate their potential for the decontamination of cadmium ions from aqueous solutions as well as for understanding the nature of the decontamination mechanism. Various physicochemical parameters, such as selection of appropriate electrolyte, equilibration time, amount of adsorbent, concentration of adsorbate, effect of diverse ions, and temperature, were studied to simulate the best conditions in which this material can be used as an adsorbent. Maximum adsorption was observed at 0.005 mol L-1 acid solutions (HNO3, HCl, and HClO4) using 0.2 g of adsorbent for 8.89x10(-5) mol L-1 cadmium concentration in 10 minutes equilibration time. Studies show that the adsorption of cadmium decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the range of 1.78x10(-5) to 1.78x10(-3) mol L-1 cadmium concentration. The characteristic Freundlich constants, i.e., l/n=0.61+/-0.02 and K=5.14x10(-4)+/-1.14x10(-5) mol g(-1) have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 10.1+/-0.60 mol(-1), indicating an ion-exchange mechanism of chemisorption. The uptake of cadmium increases with the rise in temperature (278 to 323 K). Thermodynamic quantities, i.e., DeltaG, DeltaS, and DeltaH were also been calculated for the system. The sorption process was found to be exothermic.