AN ELECTROKINETIC STUDY OF PYRITE OXIDATION

The electrokinetic properties of pyrite have been studied as a function of pH in various pretreatment conditions: conditioning in argon, nitrogen, air and oxygen atmospheres, at several conditioning pH values and for several conditioning times. The zeta potential of "virgin" pyrite is negative over the pH range from 3-10. Upon exposure to oxygen, a reversal of zeta potential from negative to positive occurs at low pH values. This reversal takes place more rapidly at lower conditioning pH values. The isoelectric point of "virgin" pyrite has been estimated to lie at a pH of 1.2 +/- 0.4. A mechanism for dissolution of iron from the surface followed by electrostatic adsorption of positively charged iron hydroxide species onto negatively charged surface sites on pyrite has been proposed to account for the observed results. Good agreement has been found between the experimental and the calculated zeta potential data using electrical double layer theories.