Improved flotation of arsenopyrite by ultrasonic pretreatment

Several flotation strategies for arsenopyrite have been developed over the last two decades. For refractory gold ores containing arsenopyrite, these flotation techniques have been found to have some limitations. Pretreatment of the ore is necessary to enhance arsenopyrite flotation and thereby increase gold recovery. In the present study, ultrasonic treatment was used as a pretreatment for enhancing arsenopyrite flotation. Pretreatment of naturally oxidized arsenopyrite changed the surface charge characteristics. The zeta-potential values became more positive and the point-of-zero-charge changed, approaching that of the native surface of arsenopyrite. Prolonged sonication reversed the sign of the zeta-potential from negative to positive. The flotation recovery of arsenopyrite increased significantly after sonication in the natural pH range of 5.5 to 6.0. Maximum recovery of arsenopyrite was obtained in the acidic pH range. It was also found that sonication could remove the oxide layer of highly oxidized arsenopyrite, rendering. it floatable. This pretreatment was applied to an actual refractory gold ore containing arsenopyrite, and it was found that recovery of arsenopyrite increased with sonication time. Furthermore, gold recovery increased along with arsenopyrite. Thus, the applicability of ultrasonic pretreatment for refractory gold ores containing arsenopyrite in enhancing flotation recovery of both arsenopyrite and gold is demonstrated.