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RECOVERY OF GOLD FROM ELECTRONIC WASTE BY IODINE-IODIDE LEACHING

Gold recovery by iodine-iodide solution is an effective and environment-friendly method. The aim of this research is to investigate the possibility of iodine-iodide gold recovery from gold-plated metal, which is a waste product of the electronic industry. Leaching experiments were carried out in solutions, containing 25 g l-1 iodine and 100 g l-1 KI, under room temperature, rotating speed of 500 rpm and mass ratio of 1:10. The degree of gold recovery for 1 minute leaching was 97,55 %. The concentrations of copper and nickel in the solution were about 0.05 g l-1, while the iron concentration was equal to that of the gold. It had been found that when gold concentration in the solution reached 1 g l-1, the iodine concentration decreased with 20 %. The optimal parameters of reducing dissolved gold iodide salts to gold metal are determined as 20 g KOH and 4 ml 10 % N2H4.H2O per one liter of the solution. Simultaneously with gold, iron and nickel almost completely precipitated (90 %), while the copper precipitation degree was around 25 %, because a large part of it precipitated as CuI during the leaching. The gold was separated from the precipitate by HNO3 treatment.The overall gold recovery is 94,56 %. Experiments were conducted to regenerate the solution by decreasing pH with H2SO4 and by adding of H2O2, as an oxidizing agent. The achieved regeneration degree was 80 %. The main disadvantage of iodine-iodide leaching is the great consumption of reagents and the need for a significant number of filtrations.