Anodic reaction of a PbO
2(Pb) electrode in suspension-electrolysis of β-ZnS was studied by the interfacial impedance method.
The experimental results obtained are as follows :
(1) The double layer capacitance of the PbO
2(Pb) electrode prepared is very high. The equivalent circuit at the interface consists of a frequency-dependent polarization resistance and the double layer capacitance in parallel.
(2) On the anode of suspension-electrolysis, the graphite particles are oxidized electro-chemically to (C-O) or (C-OH) at the surface of PbO
2(Pb) anode and the oxidation current increases with increasing suspension amount.
(3) The PbO
2(Pb) anode reaction in the electrolyte suspending only β-ZnS is the oxidation of H
2S with the active oxygen generated by the discharge of water. In a low electrode potential region, the oxidation is controlled by both the charge-transfer process of the producing the active oxygen and the diffusion process of the product H
+. In a high electrode potential region, the anode reactions are dominated by the first order chemical reaction process of the oxidation of H
2S by the active oxygen and the diffusion process of the product H
+.
(4) In the case of the suspension system β-ZnS+graphite powder with the addition of Fe
3+, the oxidation current is remarkably larger than the electrolyte without these substances. The reactions are mainly the oxidation of Fe
2+ and the oxidation reaction of H
2S, which is generated by the leaching of β-ZnS in acidic solution, with the subsequently produced Fe
3+. The processes of the first order chemical reaction of the oxidation of H
2S by Fe
3+ and the diffusion of Fe
2+ dominate the anode reaction.
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