ISOTERMAS DE ADSORÇÃO DE COBRE POR BENTONITA

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 copper adsorption process by bentonite clay and to evaluate the electrolyte type and pH influence on this process. In order to quantify the adsorbed copper, 2 g of bentonite clay were equilibrated for 24 hours with 20 mL of a NaNO3 (0,01 mol L-1) solution and with 20 mL of water containing different quantities of copper (5, 10, 20, 40, 60, 80, 100,120 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. Langmuir isotherms presented two distinct adsorption regions at both pH 4 and pH 6, showing that the adsorptive phenomenon occurs in two distinct stages. The adsorption of copper depends on pH and ionic strength and it increased with an increase in pH and decreased slightly with an increase in ionic strength. The maximum capacity of adsorption and the bonding energy varied with the pH, with electrolyte used and with the adsorption regions.