Electrochemical utilization of sodium chloride solutions with obtaining iron chlorides

Abstract

The problem of demineralization of natural mine waters and other waters with high mineralization today is acute. Based on the analysis of scientific publications in recent years, the main trends in the field of water treatment and wastewater treatment have been identified. When choosing a method of natural and wastewater treatment should pay attention to the peculiarities of the processes.The most appropriate approaches to the processing of concentrated solutions to produce useful products. If the sulfates, calcium and magnesium, were relatively easy to distinguish from the water, the most problematic is the recycling of sodium chloride. The purpose of this article is to determine the electrochemical recycling of sodium chloride with obtaining concentrated solutions of iron (III) chloride and alkali.In this work, the processes of electrochemical processing of sodium chloride solutions to obtain iron (III) chloride and alkali in a three-chamber electrolyzer with anion exchange membrane MA-41 and a cation exchange membrane MK-40 and in a two-chamber electrolyzer with a cation exchange membrane MK-40 were investigated.In the processing of concentrates with a relatively low level of salinity in three-chamber electrolytic cell with an iron anode to achieve a sufficient concentration of ferric chloride in anolyte necessary in the working chamber continuously feeding fresh solution of sodium chloride, after reducing its concentration to values below 10 mg-equiv/dm 3 . The concentration of alkali in the cathode region, it is advisable to raise to ~1500 mg- equiv/dm 3 . With a further increase of the alkali concentration in catholyte significantly increase the electrical resistance of the system.Studies have shown that to increase the concentration of iron (III) chloride in anolyte at relatively low concentrations of sodium chloride solution useful in the working chamber to progressively upgrade desalinated solutions for the starting ones. It should be noted that each load of fresh sodium chloride solution into the working chamber after 4 hours of electrolysis, the degree of removal of chlorides has reached 98-99 %.Also, the research results show that the process of electrolysis of sodium chloride in a two-chamber cell with a cationic membrane MK-40 is effective at the initial stage of the process at high concentrations in the anolyte of sodium cations. Despite the obvious shortcomings of this cell at the initial stage of the process, the yield of alkali current reached 46-75 %. Subsequently, due to poisoning of the membrane by iron cations, the process stops.To increase the current yield of ferric chloride (III) in the anolyte, iron shavings in contact with the anode were added to the anode chamber with an iron anode. It was found that when using iron shavings in contact with the anode in the anode region, the yield of soluble iron chloride does not exceed 15 % due to the precipitation of a significant amount of iron oxychloride in the sediment with increasing pH to 5.1-5.7. Maintaining a three-chamber electrolyzer with an iron anode in the anode region during the electrolysis of sodium chloride pH at the level of 1–2 in the anolyte allows to obtain a concentrated FeCl 3 solution at high current yield of both FeCl 3 in the anolyte and NaOH in the catholyte.