A STUDY BY IMPEDANCE SPECTROSCOPY OF THE REACTIVITY OF FRESHLY POLISHED GALENA ELECTRODES - OXIDATION AND INTERACTION WITH ETHYLXANTHATE

The electrochemical behaviour of natural galena (PbS) is studied in re lation to mineral flotation, Following a previous paper mainly devoted to the study of the semiconducting properties of such electrodes, the present one is focused on two important problems related to mineral p rocessing; the sample oxidation at high positive potentials and the re activity with two collection reagents, ethylxanthate (EtX(-)), a colle ctor, and Na2S, a depressant. By electrochemical impedance spectroscop y, it is found that the surface oxidation begins beyond +0.14 V (SCE) in the absence of these reactants. The kinetic law for the growth of t he oxidised films is established, However, the competition between the adsorbabilities of OH-, collector and depressant, seems to play a det ermining role in the recovery or depression of galena.