The Study On The Electrochemical Oxidization Of Sulfide In Alkaline Solution

Hydrogen sulfide existing in wastewater, petroleum and natural gas frequently contaminates environments and, in some case, causes local corrosion even stress corrosion cracking to the metallic equipments. H2S is also quite toxic, and may cause permanent physical harm and even death to human. Many techniques have been developed to remove H2S from the system for above purposes. One of them is electrochemical oxidation, which has the advantage of low cost, higher efficiency, simple operation. and is especially suitable to wastewater with low H2S concentration. Therefore, the mechanism study of electrochemical oxidization of sulfide in aqueous solution has been increasingly paid much attention in recent years. In this paper. electrochemical oxidization of sulfide on platinum electrode in alkaline solution has been studied by electrochemical techniques. Results showed that two oxidation processes of sulfide existed in the range from ?00mV to +800rnV(SCE). Sulfides were first oxidized to sulphur and polysulphides. at ~OOmV, deposited on the surface of electrode. and the sulphur deposited in the first step was further oxidized at 25OmV to sulfate entering solution. Oxidization under lower potential was the reversible reaction and the rate-determining step of this reaction was sulfide ions-diffusion control. The reaction that suphur was further oxidized to sulfate under higher potential was the irreversible reaction. These two processes were closely correlated with each other. During the whole electrochemical process, neither sulfite ions or its oxidation, nor the sulfide ions oxidation to sulfate were detected. In addition, the results also showed that pH value, stirring, concentration of sulfide, temperature and sodium chloride concentration had considerable effects on these two processes, and different electrode materials greatly affected oxidation rate in the whole case. The characteristics of electrochemica] oxidation processes of sulfide in alkaJine solution had been summarized and the best technical conditions on which sulfides in solution were removed by electrochemical oxidization were proposed.