Effect of fulvic acid on the sorption of Cu and Pb onto γ-Al 2O 3

Abstract

This work investigated the adsorption of Cu and Pb at the surface of γ-Al 2O 3 in the presence of fulvic acid to address the significance of dissolved organic matters on metal partitioning. Fulvic acid, obtained from International Humic Substance Society, represented dissolved organic matter. Fulvic acid concentrations employed herein were 1, 5, and 10 mg C/L, which simulated the relevant environmental conditions. Ion selective electrodes were employed to ascertain free Cu and Pb measurements. The maximum adsorption of 10 mg C/L fulvic acid on γ-Al 2O 3 was 5×10 −2 mg C / mg γ-Al 2O 3. Fulvic acid promoted Cu adsorption in low pH conditions. The effects of fulvic acid on Pb adsorption were similar to those of Cu. The conditional stability constants of sorbed fulvic acids with Cu and Pb were determined to be in the order of 4 to 6 ( log K) . Cu and Pb species were modeled in heterogeneous systems using triple-layer model. Simulation results indicated that metal species are dominantly in complexation with fulvic acid, both in solution and at the γ-Al 2O 3 surface.