Optimization of efficient stable reagent of alkaline thiourea solution for gold leaching

Abstract

Na₂SiO₃ and Na₂SeO₃ were chosen as stable reagents of alkaline thiourea solution substituting Na₂SO₃, according to the structure-property relationship between the stability of alkaline thiourea and the structure of thiourea and sulfite ion, and the effect of the stable reagents on stability of alkaline thiourea was investigated. The results show that contrary to Na₂SeO₃, Na₂SO₃ and Na₂SiO₃ affect the stability of alkaline thiourea solution remarkably. The stable effect of Na₂SiO₃ on alkaline thiourea is obviously better than that of Na₂SO₃. The stable reagents Na₂SO₃ and Na₂SiO₃ decrease the decomposition rate of alkaline thiourea solution greatly, and the decomposition rate of alkaline thiourea reduces from 72.5% to 33.8% with addition of 0.3 mol · L⁻¹ Na₂SiO₃. Dissolution currents of gold in the alkaline thiourea solution containing Na₂SO₃ and Na₂SiO₃ are 2.0 mA · cm⁻² and 3.5 mA · cm⁻² at the potential of 0.42 V, respectively, and Na₂SO₃ is consumed excessively due to the oxidation reaction of Na₂SO₃ occurring in the studied potential range. Na₂SiO₃ is an efficient stable reagent of alkaline thiourea solution, and gold dissolution is accelerated much more obviously by Na₂SiO₃ than by Na₂SO₃.

Keywords

alkaline thiourea / gold leaching / stable reagent / Na₂SiO₃ / Na₂SO₃ / Na₂SeO₃

References

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