DOI 10.35776/VST.2021.12.04
UDC 628.166:541.135

Pchel'nikov I. V., Nguen Tkhi Tuan Z’ep, FESENKO L. N.

Study of the current waveform effect on the formation of cathode deposits during direct electrolysis
Part 2. Electrolysis of sea water

Summary

Sodium chloride is a raw material for the production of sodium hypochlorite; however, the cost of its purchase and delivery is up to 25–30% of the total cost of the disinfectant produced. An alternative raw material for the production of sodium hypochlorite can be chlorides present in natural mineral water, e. g., underground, sea and oceanic water. Mineral water will be the raw material for obtaining sodium hypochlorite solution of a sufficiently high concentration that can then be added to the treated water. The experience of operating CHLOREFS units manufactured by EKOFES SPE LLC showed that the main problem related to the electrolyzer operation reliability is associated with the formation of deposits of hardness salts – calcium carbonate on the surface of the cathodic electrode, and magnesium hydroxide on the surface of the electrolyzer cathodes. This results in a negative electrolysis regime, an increase in voltage, overheating and warping of the electrode system, destruction of the oxide coating of the anodes, etc. The results of studies of direct electrolysis by direct and reverse current of salt water of the South Vietnam Sea are presented. During the tests the effect of reverse current in comparison with direct current on the reduction of the formation of insoluble substances on the cathodes of the electrolyzer was estimated, and besides, the electrolysis process parameters were determined. The current chlorine yield for seawater was above 100% in the reverse mode with a current density of 100 A/m².

Key words

disinfection , water treatment , sea water , sodium hypochlorite , direct electrolysis with constant and reverse current

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