Study On Hydrometallurgical Extraction Of Gold From Discarded Computer Circuit Boards

In addition to a large number of precious metal resources,electronic waste also contains many harmful materials.If not handled properly,it will not only be a waste of amount of resources,but result in serious damage to the environment.In this paper,the discarded computer circuit board was used as raw material.After digestion,the gold content in the circuit board was measured to be 0.056 mg/g,and the copper content was 311 mg/g.Due to the influence of copper in the circuit board on the leaching of gold,the ordinary metal such as copper in the circuit board was pretreated with nitric acid.Then the gold in the circuit board was leached by thiourea and sodium hypochlorite,the best gold leaching condition were determined.Finally,the extraction experiment of gold with 3,5,5-trimethyl amide as extractant was curried out,the results was shown as the following:?1?The concentration of nitric acid in copper nitrate leaching was the main factor affecting copper leaching.The optimal leaching conditions optimized by orthogonal experiment were:nitric acid concentration 6mol/L;solid-liquid ratio 1:4;reaction temperature 40°C;reaction time 1h.The best conditions were selected for three parallel experiments,the average leaching rate of copper was 96.7%.?2?The optimum conditions for thiourea leaching gold were:thiourea mass concentration 12g/L,reaction time 60min,reaction temperature 30?,Fe³⁺concentration 0.45%,pH 1.5,and the leaching rate of gold reached 90.93%under this condition.?3?The optimum conditions for sodium hypochlorite leaching were:sodium hypochlorite concentration 6 mol/L,HCl concentration 10 mol/L,reaction temperature30°C,reaction time 90 min,the gold leaching rate under this condition was 92.8%.?4?3,5,5-trimethyl amide can selectively extract gold,at a reaction temperature of30°C,reaction time 30 min,a hydrochloric acid concentration of 6 mol/L,when A/O=1,the extraction of gold was up to 93.1%.