Equilibrium and Thermodynamic Studies of Zinc Adsorption on Expanded Vermiculite

Abstract

Because of industrial growth, large amounts of effluents are generated, which need to be treated. Among the micropollutants usually present in industrial effluents, heavy metals are especially dangerous to aquatic environment because they are bioaccumulated along the food chain. This work aims to study the removal of zinc ions in aqueous solution by adsorbing them onto expanded vermiculite. In addition, equilibrium and thermodynamics studies were carried out to verify the spontaneity and the characteristics of the process. Langmuir, Freundlich and Dubinin–Radushkevich's models were applied to the data obtained from isotherms at temperatures of 273, 293, 313 and 333 K. Furthermore, experiments in static system were carried out to choose a suitable eluent to this process, to find the metal concentration and identify a method for effective recovery of the adsorbent. This adsorption process was found to be spontaneous, favourable, endothermic and physical. The best eluting agent was ethylenediaminetetraacetic acid (0.1 M); however, for cycle adsorption experiments the best agent was CaCl 2 (0.1 M).