Effect of regrinding conditions on pyrite flotation in the presence of copper ions

• Regrinding conditions affected pyrite flotation in the cleaner stage in the presence of Cu2 +.
• Pyrite flotation was depressed after regrinding with both stainless and mild steel media.
• An additional amount of collector increased pyrite flotation to some extent.
• Further adding Cu2 + decreased or increased pyrite flotation depending on the medium type.
• Pyrite flotation is governed by the modified property of the carried and new created surfaces.

In this study, the effect of regrinding conditions on copper activation on the pyrite surface and subsequent pyrite flotation in the cleaner stage was investigated. Pyrite was activated by copper ions during primary grinding, and the rougher flotation concentrate was reground in a tumbling mill prior to the cleaner flotation. The regrinding condition was manipulated by two types of grinding media, stainless steel and mild steel. It was found that pyrite flotation in the cleaner stage was depressed especially when mild steel media was used during regrinding. An additional amount of collector improved pyrite flotation especially when stainless steel media was used during regrinding. An additional amount of copper ions further increased pyrite flotation after regrinding with mild steel media but decreased pyrite flotation after regrinding with stainless steel media. XPS (X-ray photoelectron spectroscopy) analyses and EDTA (ethylene diamine tetraacetic acid) extraction revealed that the different response of pyrite flotation in the cleaner stage to stainless steel and mild steel media used during regrinding was associated with the modified property of the Cu-activated pyrite surface carried from the rougher flotation concentrate and the new pyrite surface created during regrinding.