Study On Gold Leaching Process By Thiocyanate Method

Cyanide leaching is a mature gold leaching method,which has been widely used in Chinese gold industry.A large number of three-step precipitated slag is produced in the process of gold leaching by cyanidation.If the waste slag is not treated properly,it will cause serious environmental pollution.The main component of the precipitated slag is cuprous thiocyanate.SCN-can be directly degraded to form a new "three wastes".At the same time,the cost is high.It is considered to recycle and use it for gold extraction to make waste.In this paper,thiocyanate method is used to study the gold leaching process.The results can provide theoretical basis and experience for the industrial application of this type of gold leaching method.The cyanogen bearing tailings of low sulfur gold concentrate and the cyanogen bearing tailings of roasted gold concentrate were used as raw materials to study the gold leaching process by thiocyanate method.The effects of sodium thiocyanate concentration,leaching time,liquid-solid ratio,blast volume,manganese dioxide addition and other factors on the gold leaching results were investigated,and the best gold leaching conditions were obtained.In the best condition,cuprous thiocyanate solution of equal concentration prepared by the laboratory instead of sodium thiocyanate was used for gold leaching and the results were compared.Under the best conditions of leaching time 3 h,concentration of sodium thiocyanate 0.3 mol/l,liquid-solid ratio 2:1 and blast volume 1 L/min,the gold content in the residue decreased from 1.50 g/t to 0.82 g/t.The gold content in the cyanide bearing tailings of the low sulfur gold concentrate was leached by the copper thiocyanate solution with the concentration of 0.3 mol/1 under the optimum conditions.After leaching,the gold content in the tailings was reduced from 1.50 g/t to 0.83 g/t.Under the optimum conditions of 3 hours leaching time,0.2 mol/L sodium thiocyanate concentration,2:1 liquid-solid ratio and blast volume 1 L/min,the gold content in the slag was reduced from 1.09 g/t to 0.81 g/t.The gold in the cyanogen bearing tailings of the roasted gold concentrate was leached with the copper thiocyanate solution with the concentration of 0.2 mol/1 under the optimum conditions.After leaching,the gold content in the tailings was reduced from 1.09 g/t to 0.82 g/t.The leaching process of low sulfur gold concentrate and roasted gold concentrate was studied by thiocyanate method.The effects of sodium thiocyanate concentration,leaching time,pH,liquid-solid ratio,manganese dioxide content,glycine content and other factors on the leaching results were investigated.The best conditions for gold leaching were obtained and compared with cyanidation in terms of gold leaching rate and gold leaching rate.Under the optimum conditions of sodium thiocyanate concentration of 1 mol/L,leaching time of 48 h,pH of 1,liquid-solid ratio of 2:1,manganese dioxide content of 1 g/kg and glycine content of 1 g/kg,the gold content of the low sulfur gold concentrate is reduced from 47.22 g/t to 9.11 g/t,and the gold leaching rate is 80.7%.Compared with cyanidation,the result and rate of gold leaching need to be improved.Under the optimum conditions of sodium thiocyanate concentration 0.6 mol/L,leaching time 48 h,pH 1,liquid-solid ratio 2:1,manganese dioxide content 1 g/kg and glycine content 1 g/kg,the gold content in the roasted gold concentrate is reduced from 51.90 g/t to 1.50 g/t,and the gold leaching rate is 97.1%.Compared with cyanidation,the results and rate of gold leaching are close to that of cyanidation.The results show that thiocyanate leaching can achieve the similar gold leaching rate as cyanidation,and has good selectivity for gold and silver,fast gold leaching rate,environmental protection and low cost,so it has a good industrial application prospect.