The adsorption of Cd(II) and Pb(II) to chitin in seawater

Abstract

The adsorption of Cd2+ and Pb2+ to the surface of chitin has been studied in seawater as a function of pH (2 to 8), temperature (5 to 60°C), salinity (4 to 36), and the presence of other transition metals. The rates of adsorption were quite rapid () and were affected by the presence of other metals such as Cu2+. For Pb2+, a Langmuir-type adsorption equilibrium was used to represent the experimental data. The Langmuir stability constant, KHs, was 1.9 × 10−10 mg mol−1 and the complexing capacity was 4.4 × 10−8 mol g−1. For Cd2+, a single linear adsorption with a slope of 515.1 ± 8.7 ml g−1 was found. A decrease in the temperature resulted in greater adsorption for both Cd2+ and Pb2+. For Pb2+, an increase in the salinity resulted in a decrease of the adsorption. For Cd2+, the reverse behavior was observed as a consequence of a direct competition between the chitin surface groups and the Cl− ions in solution.