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 reac tions involved in the adsorption-abstraction of K-amyl xanthate on pyr ite after fine grinding in a special stainless steel laboratory rod mi ll. Freshly wet ground pyrite exhibits surface oxidation products whic h are mainly iron hydroxides or oxy-hydroxides, sulphur and iron sulph ates. All these degradation products are present at the pyrite surface during the flotation process when relatively small quantities of coll ectors are used. For all samples prepared after grinding in basic cond itions (pH betweeen 9.0 and 12.0; regulators were NaOH and CaO), only diamyl dixanthogen was identified on the pyrite surface after flotatio n. Hence, dixanthogen is responsible for the hydrophobicity of the sur face. It is demonstrated that in basic conditions, iron compounds and sulphoxy species are responsible for the process of oxidation of xanth ate to dixanthogen.