Gold is frequently found in nature associated with sulfides, as pyrite and arsenopyrite. Usually, these sulfides are concentrated by flotation and submitted to posterior hydrometallurgical treatment. The flotability of the sulfide minerals depends on the hydrophilic/hydrophobic balance, which is induced respectively by the oxidation products formed on the minerals surface and by the collector adsorption that can not be completely interrupted by the presence of oxidation products. In the present work, rest potentials measurements for pyrite and arsenopyrite indicated that after the addition of hydrogen peroxide solution 10 % v/v in a 1 mL/min rate, these minerals were oxidized to Fe(OH)3 and FeOOH, respectively. Cyclic voltammetries indicated that ferric xanthate and dixanthogen are the species responsible for the hydrophobicity of pyrite and arsenopyrite respectively. Furthermore, the minerals oxidation leads to the formation of those species at more elevated potentials. Rest potentials measurements indicated that the formation of Fe(OH)3 on the pyrite surface due its oxidation is inhibited when this mineral is connected to arsenopyrite. The rest potential of arsenopyrite in the presence of nitrogen bubbling is more elevated when connected to pyrite, indicating its anodic behavior.
Pyrite; arsenopyrite; oxidation; adsorption of xanthate; galvanic interaction
