Effect of Sodium Sulphide on the Prevention of Copper Activation for Sphalerite

Abstract

The effect of sodium sulphide on the prevention of copper activation for sphalerite was studied. The adsorption of copper ions on sphalerite was measured in a solution containing copper ions and sodium sulphide by varying the pH value of the solution. From the results obtained, it was recognized that the adsorption of copper ions was prevented completely in an alkaline solution containing sodium sulphide. When sodium cyanide was used as a depressant, the effect of sodium sulphide on the prevention of copper activation was investigated. Up to a certain amount of sodium cyanide, the floatability of sphalerite increases with the increase of sodium cyanide. It was confirmed that this phenomenon was caused by coating copper sulphide particles or copper complexes precipitated by sodium sulphide on the sphalerite surface. However, by increasing the concentration of sodium cyanide to over 30 mg/1 and by the addition of sodium sulphide, it was seen that the depressing effect of sodium cyanide was considerable. In the case where sulphurous acid was used as a depressant, the floatability of sphalerite did not decrease at the low pH value, and colloidal sulphur was formed by the decomposition of sodium sulphide. However, with the increase of the pH value and the amounts of sulphurous acid, the depressing effect of sulphurous acid in the presence of sodium sulphide was most marked. Consequently, it may be considered that copper activation for sphalerite is prevented completely when using sodium sulphide.