Gold adsorption from cyanide solution by chitinous materials

Abstract

AbstractAdsorption of AuCN2− by chitinous materials such as acid‐washed crab‐shells burnt crab‐shells, as well as by chitin modified by quaternization of amine was affected by the pH of the sorption system. The maximum AuCN2− uptake by acid‐washed crab‐shells occurred at pH 3.7 corresponding to a final Au concentration of 0–0.025 mM. While this material did not bind any AuCN2− at pH 10, crab‐shells burnt in a non‐oxidizing atmosphere removed 90% of the metal under these alkaline conditions. SEM with EDXA analysis of the biosorbent showed that the heat treatment changed the ratio of C/O and created a highly porous material structure. FTIR results indicated that phenolic groups were the main sites responsible for AuCN2− binding on burnt acid‐washed shells. Chitin, the main component of crab‐shells, was modified by grafting tertiary amine to C‐3 and C‐6 on chitin to create quaternary amine groups. The presence of quaternary amine groups also made AuCN2− uptake possible at pH10. The results confirmed that certain chitinous materials are capable of effectively removing and concentrating anionic gold cyanide from both acidic and alkaline solutions if pretreated by appropriate physical or chemical methods.© 2001 Society of Chemical Industry