Molybdenum(VI) removal from aqueous solutions using bentonite and powdered cockle shell; Optimization by response surface methodology

Abstract

Removal of Mo(VI) from aqueous solutions by using bentonite and powdered cockle shell was conducted in this research. First, the effects of pH and initial Mo(VI) concentration on the Mo removal efficiency via shell and bentonite were studied. Results showed that Mo removal effectiveness increased as pH increased until 3.5. Removal efficiency of Mo via bentonite and shell also increased as initial Mo(VI) concentration increased to 30 or 40 mg/L, respectively, after which the removal efficiency decreased. Response surface methodology and central composite design were applied to optimize removal effectiveness. Initial concentration of Mo(VI) (mg/L), pH, and shaking time (min) were selected as independent factors. These results showed that bentonite is more effective in removing Mo from water than the shell. At the optimum condition of 5.8 pH, initial Mo concentration of 39.2 mg/L, and shaking time of 38.6 min, bentonite could remove 81.3% of Mo.