Recovery of gold from acidic thiourea solutions by reduction with iron powder under the influence of additives

Cementation of gold from acidic thiourea solution by reduction with metals consumes large amounts of reductant owing to the presence of reducible ions such as H⁺, Fe³⁺, and Cu²⁺. In order to reduce the influence of these ions on gold reduction, the additive X was introduced to enhance the gold cementation by reduction with iron powder. An experimental study on the reduction of gold in acid thiourea solution by iron powder under the influence of additive X was carried out, in which the effects of additive X dosage, reaction time, reaction temperature, stirring rate and iron powder dosage on the degree of gold reduction were investigated. The experimental results show that the degree of gold reduction is close to 100 % under the optimum conditions as follow:additive dosage 0.02 g/L, reaction time 90 min, reaction temperature 35 ℃, stirring rate 300 r/min and iron powder dosage 0.2 g/L. A comparison test with or without additive X was carried out, confirming that the use of additive X significantly improved the gold reduction from acidic thiourea solution by iron powder.