Effect of grinding media and NaHS on copper recovery at Northparkes Mines

Abstract

The flotation behaviour of copper minerals in the Northparkes Mines copper-gold ore is dependent on grinding media (and hence grinding Eh) and aeration during conditioning. Laboratory grinding and flotation tests were conducted using mild steel and stainless steel rods with and without the addition of sodium hydrosulphide (NaHS) in the conditioning stage. In the absence of NaHS, grinding using stainless steel media increased the kinetics of subsequent copper mineral flotation compared to the use of mild steel media. Flotation kinetics after grinding using mild steel media were increased by aeration prior to reagent addition. The addition of NaHS after grinding using mild steel rods increased the froth stability by increasing froth mineralisation, thus increasing the flotation kinetics of the copper minerals. When stainless steel grinding media was used, the copper flotation recovery was very high (>90 % in the rougher stage) without the addition of NaHS, so its use was not warranted. The flotation of the bornite was not reduced by oxidation, in fact copper mineral recovery was the highest under the most oxidising grinding conditions.