Removal of toxic heavy metal lead (II) using chitosan oligosaccharide-graft-maleic anhydride/polyvinyl alcohol/silk fibroin composite.

The present work was aimed to investigate the efficiency of novel chitosan oligosaccharide-graft-maleic anhydride(COS-g-MAH)/Polyvinyl alcohol (PVA)/silk fibroin (SF) composite for removing the toxic heavy metal lead (II) ion from aqueous solution by batch adsorption studies. Initially the chitosan oligosaccharide-graft-maleic anhydride copolymer has been prepared by utilizing ceric ammonium nitrate as an initiator and the optimised graft copolymer was then used for synthesizing COS-g-MAH/PVA/SF composite. The prepared samples were analyzed through FTIR and XRD studies. The FTIR results indicate that the grafted chitosan oligosaccharide copolymer was mixed homogeneously with silk fibroin and polyvinyl alcohol through intermolecular hydrogen bonding. The XRD results elucidate the changes in the crystalline behaviour of the prepared COS-g-MAH/PVA/silk fibroin composite. Both FTIR and XRD results revealed a strong interaction among COS-g-MAH, PVA and silk fibroin components. To evaluate the adsorption potential of the synthesized composite, the parameters such as pH, adsorbent dosage, contact time and initial Pb(II)ion concentration was investigated. The adsorption isotherms of Pb(II) could be described very well by Langmuir model and the kinetic results revealed that pseudo second order kinetics shows a better fit. This work provides a practical and high-efficient method for water treatment at moderate concentration of toxic heavy metals.