Zinc adsorption in bentonite clay: influence of pH and initial concentration

This paper evaluated the adsorption capacity of zinc by Bofe bentonite clay. Bofe clay was subjected to a thermal treatment for optimizing its adsorption capacity. The kinetic equilibrium of the process was studied in a finite bath system and experiments were performed by varying pH, the amount of adsorbent and initial concentration of the metal. The Langmuir and Freundlich models were used for the analysis of adsorption equilibrium. The physicochemical characterization of clay, before and after the adsorption process, included the techniques of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and N-2 physisorption. The calcined Bofe clay is able to remove zinc from synthetic wastewater. Langmuir model provided the best fit for sorption isotherms with a maximum amount of metal adsorbed of 4.95 mg of metal g(-1) of calcined clay. The adsorption was strongly influenced by the initial conditions and modifies the physicochemical characteristics of the clay.