Gold adsorption from cyanide solution by chitinous materials

Adsorption of AuCN2- by chitinous materials such as acid-washed crab-shells burnt crab-shells, as well as by chitin modified by quaternization of amin e 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 c oncentration of 0-0.025mM. While this material did not bind any AuCN2- at p H 10, crab-shells burnt in a non-oxidizing atmosphere removed 90% of the me tal under these alkaline conditions. SEM with EDXA analysis of the biosorbe nt showed that the heat treatment changed the ratio of C/O and created a hi ghly porous material structure. FTIR results indicated that phenolic groups were the main sites responsible for AuCN2- binding on burnt acid-washed sh ells. Chitin, the main component of crab-shells, was modified by grafting t ertiary amine to C-3 and C-6 on chitin to create quaternary amine groups. T he 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 acid ic and alkaline solutions if pretreated by appropriate physical or chemical methods. (C) 2001 Society of Chemical Industry.