Gold Dissolution In Dry Salt Melts In The Presence Of Sio2 As A Function Of P(O-2)

The solubility of gold was measured in dry NaCl salt melt at 860 degrees C in closed systems with SiO2 (silica glass). The reactions do not occur in a closed system without oxidizer. Reaction of SiO2 with salt in the presence of an oxidizer (KClO4) results in the formation of water-soluble sodium silicates (a mixture of meta-, ortho-, and pyrosilicates). Gold mobilization by a salt melt is limited by the diffusion of Na in SiO2. In a closed system with the addition of a strong oxidizer (dry KClO4 salt), the solubility of gold increase with increasing amount of KClO4 and the saturation level is estimated to be similar to 3 wt % Au. For ampoule configurations used in our experiments, 5.5 g of gold dissolved per 1 g of KClO4. Only cheap, non-toxic reagents were used in our model experiments on gold dissolution in a salt melt, which did not require elevated pressures. The solubility of 30 g Au per 1 kg NaCl will eliminate geochemical problems associated with the compact leaching of gold ores using cyanide.