Study of the current waveform effect on the formation of cathode deposits during direct electrolysis.
Part 1. Electrolysis of fresh water

Summary

During the electrochemical processing of chloride-containing natural water in a membraneless electrolyzer, salts of hypochlorous acid are formed that are exhibiting oxidizing properties. This process is widely used for the production of sodium hypochlorite disinfectants. The raw material for the production of sodium hypochlorite can be not only artificially prepared saline solutions, but also natural mineral water containing chlorides. The electrolysis of such solutions results in the formation of insoluble calcium and magnesium salts at the cathode of the electrolyzer thus inhibiting mass transfer in the interelectrode space and the occurrence of emergency situations. The first part of the article presents the results of studies of direct electrolysis of fresh water with constant and reverse current in Dong Hoi city, Republic of Vietnam. In the conducted tests the effect of reverse current in comparison with direct current on the reduction of the formation of insoluble substances at the cathodes of the electrolyzer was determined. The experiments have shown the advantage of reverse current over direct current. So, during the electrolysis with reverse current for a period of up to 6 hours, the amount of deposits on the electrodes did not increase, however, with direct current the deposits accumulated from the very beginning of the electrolysis process. This is due to the fact that the precipitate formed during the cathodic half cycle is dissolved during the anodic half cycle by acid, a product of water oxidation. The current output of chlorine for tap water was no more than 23% with a current density of 100 A/m².

Key words

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