Dual Function of Sugarcane Bagasse Ash in Removing Au(III) from Aqueous Solution

Abstract

Removal of Au(III) on a purified bagasse ash (BA) has been examined. The purified BA adsorbent was prepared through purification of a crude BA obtained from Madukismo sugarcane industry, Yogyakarta, Indonesia, using a mixed solution of HCl 0.1 M and HF 0.3 M and followed by HNO3 3 M. The HCl-HF-HNO3 purified BA contained quartz with silanol (Si-OH) and siloxane (Si-O-Si) functional groups and aromatic component. Removal of Au(III) on the HCl-HF-HNO3 purified BA was maximum at pH 4.2 with siloxane and silanol functional groups, but not aromatic component, took important role on the removal. At this optimum pH, the removal of Au(III) on the HCl-HF-HNO3 purified BA fitter to the second order removal kinetics model than the pseudo-first and pseudo-second order kinetics models indicating that adsorption was not the only mechanism for the Au(III) removal. The second order removal rate constants (k2) of Au(III) by HCl-HF-HNO3 purified BA was 3.32 x 102 L/mol min. In fact, reduction of Au(III) to Au metal also occurred as an addition to adsorption for the removal of Au(III) from aqueous solution.