Quantifying accidental activation. Part II. Cu activation of pyrite

As a case study to quantify the flotation response, Cu activation of pyrite was examined. Two particle sizes, 106/150 and 37/74 μm (surface area 304 and 901 cm2/g), were used. Micro-flotation was performed to determine the rate constant, k, as a function of surface concentration of copper, [Cu]surf. The [Cu]surf was determined by EDTA extraction and controlled by contact with Cu salt solution or with chalcopyrite and chalcocite particles. The rate constant relative to zero copper, kCu/k0, followed the same trend against [Cu]surf for both particle sizes. Chalcocite gave a surface concentration about 40 times higher than chalcopyrite, corresponding to their relative ion production (the b-values in Part I). An estimate of mineral grade likely to cause activation was made assuming the grade was inversely dependent on b and taking the critical grade of chalcocite as 0.1% (Petruk, 2000). This gave a critical chalcopyrite grade of ca. 2%.