Alkaline Sulphide Leaching of Lead Oxide Slag and Purification of the Pregnant Solution for Antimony Recovery

A lead oxide slag formed in an attempt to separate Sb from valuable elements like Cu, Ag and Au has been investigated. In the study, alkaline sulphide leaching of As and Sb from the lead oxide slag as well as purification of the pregnant solution for Sb recovery through precipitation and crystallization techniques has been investigated.Leaching was conducted using alkaline sulphide solutions containing 10-30 g/L NaOH and 30 g/L S2-. Leaching parameters investigated were NaOH concentration and temperature. A synthetic solution containing 45 g/L Sb prepared by dissolving antimony (III) sulphide chemical in NaOH-Na2S system was used in the precipitation experiments. Crystallization experiments were conducted using 45 g/L Sb solution made by dissolving antimony (III) sulphide chemical in the system NaOH-S .It was found that, As and Sb leaching was influenced by NaOH concentration and temperature. Leaching recoveries of 91% As and 82% Sb were achieved in 24 hours period. Sb precipitation by H2O2 was influenced by time and H2O2 dosage, while temperature and conditioning time influenced the precipitation of Sb by So addition. In 6 hours, 99.7% Sb precipitation was achieved using H2O2, while in 72 hours, 69% Sb was precipitated from the solution by So addition. H2O2 precipitated Sb as NaSb(OH)6, while Na3SbS4 and Na3SbS4.9H2O were the phases into which Sb was precipitated by So. 34% Sb was crystallized from the alkaline solution with Na3SbS4.9H2O being the main phase in the crystals. Sb precipitation by H2O2 was recommended as the suitable method for solution purification. However, due to its high cost, it was further recommended that, under large scale operations, the use of air would be more economical.Validerat; 20110905 (anonymous