Partially carboxymethylated and partially cross-linked surface of chitosan versus the adsorptive removal of dyes and divalent metal ions

Abstract

Industrial wastes and their effluents containing dyes and heavy metals are a tremendous threat to the environment, and to treat these toxic waste streams, effective and environmentally benign methods are needed. In this study, NaCS-GL was used as an effective adsorbent, for the removal of dyes and metal ions from their aqueous solution. The presence of carboxylate groups on the NaCS-GL surface has altered the protonation of amino groups. The adsorption kinetics of dyes on NaCS-GL was initially controlled by the film diffusion or chemical reaction after which the intra-particle or pore diffusion started to govern the rate. Leaching of sodium ion confirmed the crosslinking of two carboxylate groups of NaCS-GL with the metal ions. Modeling of the adsorption isotherms revealed that the different active surface sites of NaCS-GL were involved in the adsorption of dyes and metals, suggesting the simultaneous removal of these components from the wastewater.