The effect of sodium nitrobenzene sulfonate on the galvanic interactions between gold and pyrite in cyanide solution

Sodium nitrobenzene sulfonate (NBS) is widely used as an oxidant in intensive cyanidation, yet its influence on galvanic interactions between gold and associated sulfide minerals remains unexplored. This study presents the first systematic investigation of galvanic interactions between gold and pyrite electrodes in cyanide solutions containing NBS. Galvanic current and potential measurements were performed under nitrogen purging and air bubbling using pure gold, silver–gold alloy (1 % and 10 % Ag), and rotating disc electrodes coupled with pyrite. In the absence of an oxidant, galvanic coupling produced only small current densities; however, introducing dissolved oxygen via air bubbling increased both the galvanic current density and the anodic potential of gold. NBS induced an anodic shift in the gold potential under deaerated conditions, and increasing NBS concentration proportionally increased the galvanic current density under nitrogen purging. Under aerated conditions, galvanic current densities were markedly higher in the presence of NBS than without it. 10 % silver content in the gold electrode reduced the galvanic current density, probably attributed to surface passivation. Lead ions enhanced galvanic currents by depolarising the gold surface. Plant process water had lower galvanic current densities than synthetic NaCl solutions, reflecting the influence of complex solution chemistry on electrochemical behaviour. Gold dissolution increased with galvanic current density, confirming that the observed electrochemical trends correspond to enhanced gold dissolution. These findings clarify the electrochemical role of NBS in gold–pyrite galvanic systems.