Study of the processes of electrochemical synthesis of alkaline oxidizing agent – sodium ferrate

Summary

Internationally in the process of purifying industrial wastewater containing organics resistant to oxidation advanced oxidation technologies that provide for the use of oxidizing agents that possess extended oxidizing potential are gaining around. Alkaline sodium ferrate solution is one of the most active oxidizing chemicals. Laboratory studies were carried out to investigate the process of sodium ferrate production by electrolytic treatment of strong sodium hydroxide solution (30–40%) in a membrane electrolyzer with a steel anode. It is shown that in the process of 40% solution of sodium hydroxide activation in the membrane electrolyzer with the laminar steel anode for five hours (anode current density 100 А/m², specific quantity of electricity 20.5 A.h/l) the concentration of sodium ferrate in the anolite reached 7.2 g/l. The current efficiency of sodium ferrate output changed from 0.54 during the starting period of the electroactivation treatment to 0.28 at the end of the process. It was determined experimentally that during the storage of sodium ferrate for seven days its concentration in 40% sodium hydroxide solution dropped from 7.2 to 1.8 g/l. The use of sodium ferrate, alkaline oxidizing agent possessing extended oxidizing potential in the process of industrial wastewater disruptive treatment will provide for the significant reduction of resistant to oxidation organics present in it.

Key words

industrial wastewater , physical and chemical treatment , sodium ferrate , membrane electrolyzer , поверхностный сток , electroactivation , sodium hydroxide

Methods of supplementary chlorination in the long sections
of the water mains in Novokuznetsk

Summary

According to SanPiN 2.1.4.1074-01, while supplying water to the distribution network, the concentration of residual free chlorine in it should be from 0.3 to 0.5 mg/l, and that of residual combined chlorine – from 0.8 to 1.2 mg/l; in the distribution network, the concentration of residual free chlorine is not regulated; however, the quality of drinking water should be epidemically safe. To address this problem, the specialists of the chief process engineer department at Vodokanal LLC studied the technologies of supplementary chlorination in the water transportation system at one or several stages, and of chlorammoniation at the water treatment facilities. It has been established that chlorammoniation provides for a prolonged action of chlorine in water and prevents the formation of carcinogens. However, after the introduction of ammonia, a foreign odor and aftertaste (pharmaceutical, medicinal) appeared in all analyzed samples. It was experimentally proved that during chlorammoniation in summer during hot periods and with the presence of foreign moldy odor in the river water, ammoniation did not either prevent or reduce the intensity of foreign odor and aftertaste in drinking water. Various technologies of supplementary chlorination in the water transportation system were studied and local supplementary chlorination of drinking water by membrane electrolysis was recommended.

Key words

chlorammoniation , residual chlorine , membrane electrolyzer , supplementary chlorination , water odor and aftertaste

Скачать/download (PDF) free access