Characteristics of lead removal by crab shell particles

Abstract

The characteristics of lead removal by crab shell particles were investigated. The removal efficiency of lead was dependent on contact time, initial solution pH, crab shell dose, ionic strength, co-ion concentration and settling time. Approximately 99% of the lead was removed within 2 h after contact with crab shell particles. The removal efficiency was slightly affected by initial solution pH over 3.0. In addition, when the crab shell dose increased from 0.5 to 1.5 g/litre, 84% removal efficiency improved to 99.8% at initial pH 2.0. Maximum uptake of lead was 870 mg Pb/g crab shell at initial pH 3.0. Removal efficiency was not affected by ionic strength up to 1.0 M of NaNO3. Co-ions such as Cd2+, Cu2+, Fe2+, and Zn2+ did not decrease the removal efficiency significantly. All the solids formed in 'crab shell-free' solutions were difficult to settle. In contrast, in 'crab shell' solutions, the solids quickly settled which might be as a result of the adsorption of lead precipitates on the surface of the crab shell particles. (C) 1998 Elsevier Science Ltd. All rights reserved.