OXYGEN REDUCTION AT SULFIDE MINERALS .3. THE EFFECT OF SURFACE PRETREATMENT ON THE OXYGEN REDUCTION AT PYRITE

According to the mixed potential model for flotation of sulphide miner als, oxygen reduction constitute the cathodic reaction. The mechanism and kinetics of oxygen reduction is largely dependent on the propertie s of the surface. Pyrite is a relatively good catalyst for oxygen redu ction and the reaction proceeds through the formation of soluble hydro gen peroxide. Since the surface of pyrite in the flotation pulp can di ffer from the composition of bulk pyrite it is important to investigat e the influence of different surface layers on the oxygen reduction. I n the present paper the oxygen reduction was studied using the rotatin g ring-disc electrode technique. Three different pre-treatments were m ade to produce (i) an oxidised surface, (ii) a metal deficient surface and (iii) a surface of deposited sulphur. The results show that for a ll the pre-treatments made the oxygen reduction will be inhibited. The amount of soluble hydrogen peroxide also changes, decreasing in the o rder pyrite > metal deficient pyrite > oxidised pyrite. For the sulphu r covered surface, no soluble hydrogen peroxide could be detected. The results are discussed in the light of flotation of pyrite.