ABSTRACT
The use of thiourea as an alternative lixiviant to gold cyanidation for processing gold-bearing ores or concentrates was first developed by Soviet metallurgists in the 1940s. However, the interest for thiourea leaching of gold mainly came during the 1980s and 1990s to establish a parallel process. The chemistry of thiourea is simpler than thiosulfate complexation with gold, forming a cationic complex of gold. Various oxidants like oxygen, ozone, sodium peroxide, hydrogen peroxide, ferric ions, dichromate, and manganese dioxide are employed to enhance the leaching of gold in thiourea solution. Temperature plays an important role for the enhancement of leaching kinetics; hence, plenty of works have been carried out in this regard. For processing the complex ores/concentrates by leaching in thiourea solution, several pretreatments have been suggested for breaking the physical encapsulation and chemical interference to liberate the gold into the solution.
