ZINC ADSORPTION IN BENTONITE CLAY: PARTICLE SIZE AND pH INFLUENCE

Abstract

In environmental studies is important to know the adsorption process of heavy metals in clay minerals, since they are able to immobilize these metals. Knowing the cations adsorption is influenced for several factors, the objective of this research was to study the zinc adsorption process by bentonite clay and to evaluate the particle size of clay and pH influence on this process. In order to quantify the adsorbed zinc, 2 g of bentonite clay, dried at room temperature and sieved at 0.5 and 2-mm-mesh, were equilibrated for 24 hours with 20 mL of water containing different quantities of zinc (10, 15, 20, 30, 50, 100, 150 and 200 mg L-1) as background solutions of pH values 4 and 6. Langmuir's adsorption equation in its linearized form was applied and the values of the maximum capacity and those of the constant related to the bonding energy were obtained. The results showed that Langmuir equation was adequate to describe zinc adsorption at different pH values and particle size of bentonite clay. Zinc adsorption in bentonite clay depended on pH and particle size, decreasing as they increased. The maximum retention capacity, 3.24 mg g-1, was obtained in pH 4 using particle size of bentonite clay < 0,5 mm.