Adsorption of Cu (II) and Cd (II) by chininous polymers

Abstract

Heavy metal contamination has emerged as a major health problem worldwide. Biosorption, using biological waste products as sorbents, may provide a cost effective treatment strategy. The current study investigated several types of biomass, generated from waste crab shells, as bio-sorbents to remove cadmium and copper in a batch reaction system. Isotherm studies suggested that uptake increased with increasing number of amine groups, i.e. increasing degree of deacetylation (DDA) as measured by hydrogen nuclear magnetic resonance (¹H-NMR) as well as Fourier Transform Infra-red (FTIR) spectroscopy. Potentiometric titration was shown not to be a valid method in measuring the DDA for medium DDA range. pH was proven to be a main factor affecting the adsorption because of the considerable competition of protons for the binding sites at low pH. Cu²+ had higher affinity than Cd²⁺ to the chitinous polymer. Metal adsorption was elevated by high ionic strength because of more adsorption sites becoming accessible as a result of significant expansion of the network under high ionic strength. Sulfate as salt, added in the solution, greatly stimulated the adsorption of metal ions by reducing the repulsion force between the charged surface and the metal cations.