CHARACTERISTICS OF LEAD REMOVAL BY CRAB SHELL PARTICLES

The characteristics of lead removal by crab shell particles were inves tigated. The removal efficiency of lead was dependent on contact time, initial solution pH, crab shell dose, ionic strength, co-ion concentr ation and settling time. Approximately 99% of the lead was removed wit hin 2 h after contact with crab shell particles. The removal efficienc y 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% remova l efficiency improved to 99.8% at initial pH 2.0. Maximum uptake of le ad was 870 mg Pb/g crab shell at initial pH 3.0. Removal efficiency wa s 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 si gnificantly. All the solids formed in 'crab shell-free' solutions were difficult to settle. In contrast, in 'crab shell' solutions, the soli ds quickly settled which might be as a result of the adsorption of lea d precipitates on the surface of the crab shell particles. (C) 1998 El sevier Science Ltd. All rights reserved.