An investigation on gold electrowinning from acidic thiourea solutions

The use of thiourea as a gold leaching reagent has been extensively studied by many researchers, and it has proved to be promising for some cases as refractory ores. Otherwise, the recovery of gold from these solutions did not receive so much attention. In this paper the electrowinning of gold in acidic thiourea solutions was studied by voltammetry and chronopotentiometry. An adsorption step was detected prior to Au(I) reduction and the diffusion coefficients at 25 degrees C for Au-TU complex and FD were found to be 1.00 x 10(-5) cm(2) S-1 and 1.98 x 10(-5) cm(2) s(-1) respectively. At -0.350 V (SCE) a passivation probably due to TU adsorption was observed. For higher overpotentials hydrogen evolution was the main reaction.