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

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 (t12 = 20 min) 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.