INTERACTION BETWEEN FINELY GROUND PYRITE AND POTASSIUM AMYLXANTHATE IN FLOTATION .1. INFLUENCE OF ALKALINE GRINDING

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Hallimond tube flotation tests, microelectrophoresis experiments and X-ray photoelectron spectroscopy (XPS) have been used to study the reactions involved in the adsorption-abstraction of K-amyl xanthate on pyrite after fine grinding in a special stainless steel laboratory rod mill. Freshly wet ground pyrite exhibits surface oxidation products which are mainly iron hydroxides or oxy-hydroxides, sulphur and iron sulphates. All these degradation products are present at the pyrite surface during the flotation process when relatively small quantities of collectors are used. For all samples prepared after grinding in basic conditions (pH betweeen 9.0 and 12.0; regulators were NaOH and CaO), only diamyl dixanthogen was identified on the pyrite surface after flotation. Hence, dixanthogen is responsible for the hydrophobicity of the surface. It is demonstrated that in basic conditions, iron compounds and sulphoxy species are responsible for the process of oxidation of xanthate to dixanthogen.