Hydrometallurgical Technology Reseach On Golg Recovery From Waste Circuit Boards

Electronic waste has become one of the fastest growing waste, cyanide and aqua regia extraction metal in circuit board have gradually been eliminated, due to its high-pollution effect. Gold recovery from circuit boards by environmental and friendly ways have become one of the current research focus. Gold content was determinated by aqua regia in the circuit board. It was found that gold content was 47g/t and that copper was 303.5g/t,which had very high recycling value.The exsit of copper and zinc had a bad effect on gold leaching ,so nitric acid was be used to leach copper and zinc from Waste Circuit Board .Lime-sulphur-synthelic-solution,hypochlorite and bromination were selected to leach gold from the Waste Circuit Board (WCB). All of the three methods have the advantages of low toxicity and easy-operation. Three experimental methods were designed based on the three experimental program, optimum leaching conditions were(1) sodium sulfite concentration 0.1 mol/L, cupric sulfate concentration 0.03mol/L, ammonia concentration 0.5mol/L, reaction time 2.5h, reaction temperature 40℃, in this experimental condition, the gold leaching percent can reach 85%.(2) sodium hypochlorite concentration 6mol/L, sodium hydroxide concentration 8mol/L, solid-to-liquid ratio 1:6, reaction time 40min, in this experimental condition, the gold leaching percent can reach 94.5%(3) sodium bromide concentration 25g/L, manganese dioxide dose 10g, reaction time 80min, solid-to-liquid ratio 1:6, in this experimental condition, the gold leaching percent can reach 97.2%.Comparing the three methrods from the economic and environmental benefits, the lime-sulphur-synthelic-solution involves the lowest cost. Excluding equipment and reagent consumption, 687.58 yuan could be recovered in a ton of WCB, although compared with cyanide, its cost was a little higher, its environmental-friendly would meet the concept of clean production. Under the premise of sustainable development in today's society, with the improvement of leaching conditions, lime-sulphur-synthelic-solution with low pollution, might become the development trend of leaching methods .