FLOTATION OF A COMPLEX SULFIDE ORE .1. CU ZN SELECTIVITY CONTROL BY ADJUSTING PULP POTENTIAL WITH DIFFERENT GASES/

To investigate the possibility of using gases with varying oxygen acti vity and their influence on copper-zinc selectivity, flotation tests w ere done in a mechanical laboratory cell on a fine-grained complex sul phide ore with high pyrite and pyrrhotite content. The pulp environmen t was modified by changing the grinding media and by using different g ases in the pre-conditioning and flotation steps. A statistical design with two levels of grinding media, four levels of pre-conditioning, a nd three levels of flotation gas type, was used. It is found that the grinding environment is the most dominant variable influencing the flo tation results. Strong interactions exist between the pre-conditioning type and the flotation gas for mild steel grinding. Such interactions , and even the direct influence of pre-conditioning and flotation gas type, are statistically insignificant for stainless steel grinding, wh ich often gave good copper flotation. The Cu/Zn selectivity shows a st rong dependence on the pre-conditioning type and flotation gases for m ild steel grinding, but not for stainless steel grinding. The best Cu/ Zn selectivity happens for the combination of 5% oxygen pre-conditioni ng and air flotation after mild steel grinding. It seems that galvanic reactions after or during the mild steel grinding facilitate surface oxidation of sulphides. A mechanism similar to ferric leaching is prop osed. As expected, it was observed that the oxidising or reducing envi ronment in the pulp, as measured by the pulp potential, has a strong i nfluence on the flotation results.