2012 Volume 53 Issue 4 Pages 760-765
This research work focused on the simultaneous recovery of gold (40.5 mg/dm3) and iodine (748 mg/dm3) from the waste rinse water of the semiconductor industry using activated carbon. A batch study was conducted to optimize process parameters, such as contact time and carbon dose, for the recovery of gold and iodine from the waste water. The loading capacity of the activated carbon for adsorption of gold and iodine was found to be 33.5 mg Au/g carbon and 835 mg I2/g carbon, respectively. Gold was found to exist on the activated charcoal surface in two forms: ionic gold and elemental gold. Aqua regia was used to convert metallic gold to its ionic form, and the iodine and the small amount of ionic gold were removed from the activated carbon by elution with aqua regia. Gold was recovered from the eluate by reduction with hydrazine. Iodine from the diluted aqua regia was then precipitated by adding sodium hydrosulfite (Na2S2O4). A complete process flow sheet was developed to recover both gold and iodine from the waste water of the semiconductor industry, which conserves the resources while meeting environmental pollution requirements.