Photocatalytic leaching of sulfide minerals

The addition of silver, in the form of silver chloride or silver sulfide, to a sulfuric acid and chalcopyrite (CP) leach system, is a method to present the formation of a sulfur film on the CP mineral surface. The present investigation shows that mechanisms responsible for effectiveness of the applied silver compound consist of several sustaining electrochemical reactions, including photo catalysis and ion conduction. Previous researchers reported that the only effect of the silver compound on Leaching was ion conduction, and that the silver film was silver sulfide. The present study shows that silver sulfide, a P-type semiconductor, is actually not the active coating. This study shows through Mott-Schottky analysis that the silver coating is an N-type semiconductor. X-Ray diffraction proves the compound is AgCuS, Stromeyerite. In the liquid junction, an N-type semiconductor is required to create a photo diode with the liquid medium containing more hole-carriers. This diode directs Current to flow in the open-circuit condition so electrons flow to the counter electrode.; Many chalcopyrite samples, without the addition of silver sulfate, showed a higher reaction rate in the sulfuric acid Leaching solution. These samples had siliceous clay veins. Frequency and voltage scans with AC EIS (Alternating Current-Electrochemical Impedance Spectroscopy) showed that silicon also forms a liquid-electrolyte photo film on chalcopyrite.; The present study found several prerequisites for silicon photo reactivity on the sulfide surface, including the presence of sulfuric acid, and the presence of copper ions in solution, when pyrite no chalcopyrite is the sulfide mineral. Silicon can be used in the form of SiO₂ or H₂SiF ₆. This evidence contributes to the conclusion that compounds of copper silicide and silicon sulfate have photo-diode properties. Leaching experiments, with Silica and H₂SiF₆, show that these agents enhance metal recovery and they may be economically feasible.; Chalcopyrite is a narrow band gap magnetic semiconductor. When photo catalysic additives are used the Chalcopyrite surface becomes a wide band gap semiconductor with a hydrophilic surface. After Leaching with out additives a passive diffusion layer builds up on chalcopyrite the surface become more magnetic with hydrophobic properties.