Silver recovery and concentrate grade improvement for scavenger concentrates through regrinding and selective aggregation

摘要

A process scheme has been devised to improve the silver recovery and the grade of concentrates from the scavenger concentrate of a silver ore flotation circuit. Based on modal analysis studies it was found that silver sulfide minerals in the scavenger concentrate were associated as simple binary particles and finely disseminated in sulfide and non-sulfide gangues. Fine grinding of the concentrate improved the grade-recovery curve of silver to a very limited extent owing to heterocoagulation between liberated fine silver sulfides and coarse particles of gangue. This heterocoagulation phenomenon was prevented by grinding the concentrate in the presence of the dispersing reagent sodium hexametaphosphate. The silver grade-recovery curve was improved by practicing, before the conventional flotation step, a selective aggregation step for the fine silver sulfide particles using the non-polar oil kerosene, the sulfhydryl collector Aerophine 3418 and conditioning the pulp under strong agitation conditions.