Method of Obtaining of Metal Oxide Anodes That Do Not Contain Noble Metals

Abstract

In the mining and industrial regions of Ukraine, a large amount of mine and quarry waters is formed. Due to high mineralization, they cannot be discharged into natural hydrographic objects without deep processing, including demineralization. Most of such waters are significantly contaminated with concentrates of sulfides and dissolved iron compounds, which hinder their further purification. At the same time, thermal power plants located in these regions consume a significant amount of scarce drinking water for their needs. Deep processing of mine and quarry waters allows to clean them and obtain feed water for heating systems, boilers of TPPs and CHPs. A method of obtaining stable inert titanium-based anodes with an active coating of PbO2, which do not contain noble metals and their compounds, has been developed. The method consists in protecting titanium from passivation with an oxide film by thermally applying a MnO2 coating, and later applying to the base with this coating a thin layer of PbO2 from an alkaline complex electrolyte containing 2.5 mol/dm3 NaOH, 0.6 mol/dm3 EDTA, ethylene glycol additive and is a saturated PbO. The main 3–5 mm thick layer of coating is applied from the nitrate electrolyte, which includes Pb(NO3)2 1 mol/dm3, Cu(NO3)2 0.4 mol/dm3, Al(NO3)3 0.2 mol/dm3 and the gelatin additive. A method of extending the service life of an alkaline electrolyte by reduction of Pb (IV) compounds during the contact with the active surface of metallic plumbum is described. The conducted resource tests of this anode for 1400 hours proved its stability when processing solutions containing a mixture of sodium sulfate and sodium chloride. On the basis of this anode, the technology of electrochemical deironing of mine waters and removal of sulfides from them before demineralization was developed and experimentally tested. This technology is the only possible method of reagent-free iron removal and removal of sulfides from waters with high mineralization. Such anodes significantly expand the scope of application of electrochemical processes. They can be used not only for water treatment in thermal power generation, but also for the treatment of wastewater of various mineral and organic composition, chemical and technological processes for obtaining oxidants, etc.