DOI 000000

UDC 628.166:661.418

Guzii V.

Study of the corrosion and electrochemical properties of anodic coatings in conditions of chlorine electrolysis

Summary

Traditionally for water purification and disinfection various oxidizing agents have been used, usually chlorine-containing products including low-concentration sodium hypochlorite obtained by electrolysis of aqueous solution of table salt at the point of consumption. The greatest influence on the electrolysis efficiency (current active chlorine yield), electrical and electrochemical performances, effectiveness of the process and operational practices, design of devices and their durability is exerted by the anode material; the main requirement to it being the chemical resistance in the mode of anodic polarization in the chemically active environment. Ruthenium-titanium oxide anodes have become widely used in practice owing to their high-wearing properties. A decrease in the rate of continuous decrease in the thickness of the active layer and the loss of ruthenium oxide can be achieved by using a three-component coating of the anode with the addition of a platinum group metal – iridium. Three-component coatings of anodes containing iridium (iridium-ruthenium-titanium oxide anodes), with a mass percentage of iridium to ruthenium of 80:20 provide for 8-fold increasing the corrosion resistance of the anodes (service life). As the iridium oxide concentration increases, the anode coatings consume less energy for generating sodium hypochlorite owing to the lower voltage across the electrolyzer. The corrosion resistance of anodes with different ruthenium and iridium oxide fills as well as their characteristics, i. e. chlorine yield in terms of current efficiency, electrolyzer voltage, dynamics of active chlorine concentration increase were determined.

Key words

low-concentrated sodium hypochlorite , oxide coatings , iridium , ruthenium , corrosion resistance of anodes , current chlorine yield , electrolysis of 3% solution of table salt

DOI 000000

UDC 628.166

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

Study of the optimal electrolysis mode while producing sodium hypochlorite from Mediterranean Sea water

Summary

The theoretical substantiation, as well as the research results of developing the technology for producing low-concentration sodium hypochlorite by direct electrolysis of Mediterranean water for the biocidal treatment of the cooling circuit of nuclear and thermal power plants are presented. The optimal process parameters have been determined. Methods for preventing the formation of cathode deposits have been studied. It has been established that during the electrolysis of seawater with an anode current density of 1000 A/m² the maximum concentration of active chlorine 7.9 g/dm³ can be achieved; whereas at 600 A/m² – up to 6.8 g/dm³ is achieved on iridium-ruthenium-titanium oxide anodes. The current chlorine yield is within 10%. It has been shown that the current chlorine yield and specific power consumption per 1 kg of generated active chlorine reach their optimum values ​​(85–90% and 3–3.5 kWh/kg) at an active chlorine concentration in the electrolysis product of 2 ± 0.2 g/dm³. This determines the process and economic feasibility of producing sodium hypochlorite from sea (ocean) water.

Key words

disinfection , decarbonization , low-concentrated sodium hypochlorite , membraneless electrolysis , inhibition , acid-washing , electrolysis of Mediterranean water

bbk 000000

UDC 628.166.094.3

FESENKO L. N., Skryabin A. Yu., Breus S. A., Pchel'nikov I. V.

Field tests of drinking water disinfection by direct electrolysis

Summary

The results of studying direct electrolysis of natural underground water with the purpose of determining possible production of low concentration sodium hypochlorite for drinking water disinfection before supplying it to the residents of Grushevskaia village of the Aksaisk District, Rostov Area are presented. The use of natural surface or underground water as electrolyte provides for eliminating the stage of artificial chloride solution making; that will simplify the technology of disinfectant production at the point of application and reduce the operation expenses. The studies were carried out in a full-scale plant in two directions: determination of the optimal parameters of the flow-through electrolyzer; determination of the lifetime of electrodes. The results of the full-scale studies confirmed possible disinfection of chloride-containing natural water (chloride concentrations 200–233 mg/dm3) by direct electrolysis. The process parameters of the electrolyzer operation with underground fresh water were determined: current density; water flow to the elect­rolyzer (flow rate); the time of electrode operation as an anode and as a cathode. The optimal composition of electrode coating was determined: in ruthenium –iridium oxide coating the weight ratio of Ru to Ir was 20:80. The use of iridium in the coating effects the formation of active chlorine and the electrode lifetime. The presence of ruthenium in the oxide layer in 20:80 weight ratio to iridium increases the anode lifetime tenfold (up to 4000 hours) compared to the anode without iridium.

Key words

potable water , disinfection , water treatment , direct electrolysis , electrolyzer , low-concentrated sodium hypochlorite

DOI 10.35776/VST.2022.10.03
UDC 628.166

FESENKO L. N., Tcherkesov A. Yu., Pchel'nikov I. V., Pchel’nikova Anastasiia, Skryabin A. Yu.

Comparative evaluation of the economic effectiveness of using chlorine-containing media in water disinfection technologies

Summary

An engineering and economic comparison of three methods of water disinfection using: gaseous chlorine, high concentrated sodium hypochlorite and low concentrated sodium hypochlorite is presented. A comparative analysis was carried out using the example of an operating chlorination plant located on the territory of the wastewater treatment facilities in the city of Leninsk-Kuznetsky, Kemerovo Region. The economic analysis has shown that the use of low concentrated sodium hypochlorite compared to high concentrated sodium hypochlorite is beneficial, as the payback period is reduced. This confirms the expediency of using this technology since it provides for implementing a socially oriented tariff policy for consumers to a greater extent. Besides, while choosing a chemical, its advantages should be sought in the safety of delivery and storage, technological effectiveness in use, the amount of by-products in the preparation of the product at the place of use, as well as the delivery price of a chlorine-containing chemical or the cost of apparatus that produce it directly at the premises of the water treatment facilities from purchased raw materials.

Key words

gaseous chlorine , low-concentrated sodium hypochlorite , direct water electrolysis , high concentrated sodium hypochlorite , comparative analysis