鉛精鉱の半導体物性と酸性懸濁液の酸化反応速度の関係

抄録

The results of previous studies on the thermoelectric power measurement of 12 kinds of Pb concentrates and the potentialdependence of the oxidation rate of the same samples were in summary discussed to elucidate the correlation between the semiconducting property and the oxidation rate.
The oxidation in acidic suspension follows the quasi-first order kinetics. The reaction process is tentatively considered to consist of 4 steps:(1) the formation of a positive hole in the valence band by a jump of an electron from the valence band to an impurity level at the PbS surface, (2) the electron migrates through the solid-solution interface to combine with the acceptor (Fe³⁺) in the solution, (3) adsorption of Cl^-onto the surface, follovved by (4) two positive holes react with PbS to yield PbCl₂ and S^o.
For the concentrates with low Cu contents (Cu<1-2%), the rate below 0.35V (suspension potential) is represented by _??_where T_0.5, d_o,
E_m,
E_o, E^α*, k, T, and e_o are the half life time of the oxidation, the diameter of PbS particle, the suspension potential, a constant, the ionization energy for the thermoelectric power, the Boltzmann constant, the absolute temperature, and the charge of an electron, respectively. The second term in the right side corresponds to the step (2), i.e. the cathodic reduction of Fe3+, and the third term is considered to correlate with the step (1) and (4).
For a few concentrates contaminated with CuFeS₂ (Cu>2%), the thermoelectric power and the rate are closely concerned with the Cu content. It is found that the transfer coefficient (0.6 in above eq.) increases with an increase in Cu content.