Thiourea Leach Gold From Waste Printed Circuit Board And The Research On The Process Of Power Generation Recovery

This article describes the status,use value,metal content,the distribution of gold and the significance of recycling of electronic waste, it also summarizes the methods of gold recovery from waste printed circuit board. In this paper, gold was leached from circuit board by thiourea, and be recovered by the power generation process, making precious metals recycling and reuse of resources.In this study, the circuit board was pretreated using manual disassembly methods, and then comminuted the disassembed circuit board. Using nitric acid to leach base metal until no response happen, circuit board was filtered and washed several times, then got the raw materials which were required in the second step. Leach them with thiourea, let the gold of the waste printed circuit boards enter into the solution. Then the activated graphite electrode is used as cathode material and zinc as anode material, constituting the generation system, metallic gold was obtained from the cathode. Using electrochemical to research the complex solution of thiourea gold .The results show that:1) The optimum conditions of thiourea leaching are: solid-liquid ratio is 1:5, the leaching temperature is 35℃, thiourea concentration is 12g/L, pH is 1.5, ferric ion mass fraction is 0.3%, the leaching time is 1h, In this condition, the gold recovery rate is about 93%.2) The best conditions of recovery gold by generation method are: at 35℃,using zinc as anode electrodes, 0.1mol·l(-1) of KCl as anode region solution, graphite electrode as cathode, gold thiourea complex solution as the cathode region solution. Under the stirring condition, lasts 2000 min of eledctrogenerat experimental,available gold recovery is 95% or more. Researching the factors of the maximum output power found that the three factors of temperature,the anode zone solution,the anodic solution concentration do not affect the maximum output power corresponding to the load resistance. But affect the value of the maximum output power. Using optimal conditions, the maximum power generation reach to 1620 mW.3) Gold thiourea solution was researched by cyclic voltammetry, under the scanning speed is 0.05mV/s, the oxidation peak occurs at 0.0336mV, It is indicate that the reaction of +2[Au(SC(NH₂)₂)₂]⁺+2e=2Au+4SC(NH₂)₂ happened in 0.0336 mV. Increasing scan rate, peak current increased significantly, indicating that the irreversible process of anodic reaction, scanning speed increases, the peak shift positively.The SEM images of the experimental graphite electrode shows that the layer of gold was deposited relatively smooth and dense on carbon rod.