Interaction of Pb2+ and Cd2+ with gum kondagogu (Cochlospermum gossypium): A natural carbohydrate polymer with biosorbent properties

Gum kondagogu (Cochlospermum gossypium), an exudates tree gum from India was explored for its potential to decontaminate toxic metals (Pb2+ and Cd2+). Optimum biosorption of metals were determined by investigating the contact time, pH, initial concentration of metal ions and biosorbent dose at 25 +/- 2 degrees C. The maximum metal biosorption capacity for gum kondagogu was observed for Pb2+ (48.52 mg g(-1)) and Cd2+ (47.48 mg g(-1)) as calculated by Langmuir isotherm model. Kinetic studies showed that the biosorption rates could be described by pseudo-second-order expression. The metal interactions with biopolymer were assessed by FT-IR, SEM-EDXA and XPS analysis. Results based on these techniques suggest that mechanism of metal binding by the biopolymer involves micro-precipitation, ion-exchange and metal complexation. (C) 2009 Elsevier Ltd. All rights reserved.