Extraction of Gold,Platinum and Palladium from Waste Carbon

After waste carbon being roasted by controlling temperature,salts in the ash are eliminated with 1.38 mol/L HCl.The gold,platinum and palladium are leached with 2～3 mol/L HCl25 g/L NaClO 3.The gold is selective reduced by FeCl 2 at a mass ratio of FeCl 2·4H 2O to Au of 7 to 1,then platinum and palladium are reduced with zinc powder.By roasting and removing copper and other base metals with dilute H 2SO 4,and puriting by NH 4ClNH 3·H 2ON 2H 4·H 2O,the purity of platinum and palladium are more than 99%.The recovery of gold,platinum and palladium are more than 93%.