Reduction of Bromate in Water using Zerovalent Cobalt 2,6-Pyridine Dicarboxylic Acid Crosslinked Chitosan Nanocomposite

Abstract

Zerovalent cobalt 2,6-Pyridinedicarboxylic acid crosslinked chitosan (ZVCo-PDCA-CHIT) nanocomposite, which was obtained by chemical reduction of cobalt (II) ion chelated nanocomposite with NaBH4, was tested for bromate reduction in water. 2,6-pyridinedicarboxylic acid (PDCA) was used for intramolecular crosslinking of the chitosan linear chains. The products were characterized by FT-IR, XRD and SEM. The FT-IR analyses revealed the presence of coordinating –NH2 and –OH functional groups in chitosan while crosslinked chitosan showed –COOH absorption peaks. The XRD spectrum revealed a typical fingerprint of semi-crystalline chitosan which disappeared in crosslinked chitosan due to disruption of the interpolymer bonds. SEM image revealed a smooth surface for the Chitosan while large pores were observed for the PDCAcrosslinked Chitosan (PDCA-CHIT). ZVCo-PDCA-CHIT nanocomposite showed significant morphological changes with the surface structure being smooth with the disappearance of the holes observed in the crosslinked chitosan structure, indicating a very strong binding of cobalt with most of the functional groups. The applied ZVCo-PDCA-CHIT nanocomposite reduced bromate ions to bromide with possible adsorption onto the nanocomposite. The result showed that bromate reduction in water was significantly higher and near completion under 1 h using ZVCo-PDCA-CHIT (99 ± 1.1%) as compared to PDCAcrosslinked Chitosan (65 ± 1.47%) and Chitosan (53 ± 0.25%).