The U.S. Bureau of Mines investigated the effect and control of grinding conditions on the collectorless floatability of chalcopyrite. Single electrodes of high-carbon steel and chalcopyrite were used for anodic and cathodic polarization curves to determine the extent of galvanic coupling between the two materials. The effects of varying ph and additions of corrosion inhibitors on polarization behavior were examined. Typically, increasing concentrations of sodium tetraborate, sodium nitrite, or lime (i.e., more alkaline conditions) reduced the current response and passivated the electrode, decreasing the extent of galvanic interaction. Marked ball wear tests (10 marked balls) when grinding silica in a nitrogen atmosphere was about 0.06 G and was considered to be abrasive wear, while similar tests grinding silica in air increased to 0.085 Due to corrosive effects. An additional increase in ball wear was observed when a silica-chalcopyrite mixture was ground in air and was attributed to galvanic interactions between the sulfide mineral and the balls. When sodium borate or nitrite was added to the ball mill, ball wear was reduced to about the abrasive wear level for inhibitor concentrations greater than 0.5 To 1.0 pct. When batch flotation tests were performed using n2 as the flotation gas, chalcopyrite recovery was about 15 pct in the absence of inhibitor and increased to 84 and 88 pct with 0.57 pct borate or 1.0 pct nitrite, respectively. Using air as flotation gas, after grinding with inhibitors, chalcopyrite recoveries increased slightly.
Abs. 32 in Extended Abstracts, V. 91-1. Electrochem. Soc., 1991, PP. 48-49