EDTA-induced flotation of sulfide minerals

Abstract

The native and induced floatabilities of pyrite, galena, arsenopyrite, and glaucodot were investigated by flotation tests in the absence and in the presence of EDTA. The dissolution and electrokinetic behavior of the minerals in EDTA solutions was studied as a function of pH and of EDTA concentration. It was found that the flotation and dissolution of these minerals in EDTA solutions depend strongly on the pH values and on EDTA concentration. At a moderate EDTA concentration, the floatabilities and the released metal concentration are low or absent at pH below 5 and above 10. In the range of pH 6–10, both the flotation recovery and the dissolution of these minerals exhibit a plateau. The amount of released metal species increases with increasing EDTA concentration. The floatabilities of these sulfides first increase with an increase in EDTA concentration. However, a further increase in EDTA concentration to above 10 −3 M leads to a significant decrease in flotation recovery. ζ-Potential measurements show that in the presence of EDTA the IEP of the sulfide minerals is shifted considerably to lower pH values. The principles underlying the phenomena are discussed in terms of the results obtained from electrochemical studies of these sulfides and the instabilities of iron hydroxides in EDTA solutions.