Development of equipment for the electro-chemical recovery of gold from the watery effluent of the bijouterie industry

Abstract

In the city of Limeira, in the state of São Paulo, is concentrated a national pole for the production of bijouterie (semi-jewels), where around 400 small enterprises generate and discard, daily, industrial effluents with a high load of metals into the river Piracicaba. Generally, in the semi-jewel production process effluents are formed containing heavy metals (copper, nickel, zinc, cadmium and others) and gold deriving from degreasing baths and metal plating from the successive phases and the waters from the washing of pieces between one stage and another. The effluent with the metal impurities is treated conventionally through chemical precipitation, an unprofitable and inappropriate process. This work intends to develop and optimize an electrochemical reactor aimed at recovering gold from the effluents generated by the semi-jewel industry, replacing the present chemical process. To do this, it is intended to place the metal with a high deposition speed in a region of potential/current in which the reduction reaction will be controlled by mass transport, aiming to obtain a thick layer of gold and low adherence to the cathode surface. The low adherence of the gold deposited will facilitate its later mechanical removal, which will make it detachable from the electrode surface.With this aim, it is intended to evaluate different materials for the cathode in this type of process: stainless steel, copper and tin, among others. (AU)