Catalytic production of antimonate through alkaline leaching of stibnite concentrate

• The kinetics of a single-step leaching-oxidation process for antimony is addressed.
• A high leaching rate of antimony from stibnite concentrate is obtained.
• The oxidation of antimony is performed in alkaline hydroquinone electrolyte.
• The reaction rate parameters and optimum conditions for oxidation are introduced.
• Antimony (V) can be recovered as sodium hydroxyantimonate.

A hydrometallurgical treatment based on leaching and oxidation of trivalent antimony in hydroquinone-catalyzed alkaline electrolyte and precipitation of sodium hydroxyantimonate was elucidated. The influences of temperature and hydroquinone concentration on both the leaching and oxidation processes were discussed. Similar trends for recovery curves of antimony were obtained at different temperatures and hydroquinone concentrations in oxygen-rich alkaline electrolyte. The antimony recovery was calculated to be 90% within 1 h at 80 °C in 0.4 g⋅L− 1 HQ. The complete trivalent to pentavalent antimony oxidation was achieved within 4 h under optimum conditions in a single-stage process. The oxidation rate equation is as follows:rSbIII=−dCSbIIIdt=5.09.CSbIII1.02.CHQ1.05The precipitation product was found to be sodium hydroxyantimonate (mopungite) with pseudo-cubic crystal morphology. It is concluded that O2 was unlikely to be the most powerful oxidant, but rather the HQ is responsible for the rapid oxidation of Sb (III) by the formation of H2O2. The leaching and oxidation reaction mechanism for the formation of pentavalent antimony was proposed, resulting in intermediate species such as SbS33 −, SbO2− and Sb2O3.