Preconcentration of gold by rice husk ash

The goal of this research was to develop a new, efficient adsorbent of gold-thiourea complex, [Au(CS(NH2)(2)](+) In this experiment, rice husk was heated at three different temperature. 300 degrees C, 400 degrees C and 500 degrees C. Rice husk ash heated at 300 degrees C adsorbed gold thiourea complex, whereas rice husk ash heated at 400 degrees C and 500 degrees C did not. The structure of rice husk ash heated at 300 degrees C had specific silanol groups and oxygen functional groups of carbon, while rice husk ash heated at 400 degrees C and 500 degrees C contained siloxane groups. Maximum gold adsorption of rice husk ash heated at 300 degrees C and activated carbon, was 21.12 and 33.27 mg Au/g adsorbent respectively. However, rice husk ash absorbed 0.072 mg thiourea/g adsorbent which was less than activated carbon adsorbed (0.377 mg thiourea/g adsorbent). In addition, the adsorbed gold could be eluted from this rice husk ash by sodiumthiosulfate more easily than from activated carbon. The results revealed that rice husk ash heated at 300 degrees C can be used as a new adsorbent for gold thiourea complex. (C) 2000 Elsevier Science Ltd An rights reserved.