In this work, the processes of electrochemical processing of sodium chloride solutions with the production of iron (III) chloride and alkali in a three-chamber electrolyzer with MA-41 anion-exchange membrane and MK-40 cation-exchange membrane were investigated. The conditions for the removal of sodium chloride from water in a three-chamber electrolyzer using an iron anode were determined depending on the anode current density and the reaction of the medium in the anode region. The parameters of the process of concentrating iron chloride in the anode region were established at relatively low concentrations of sodium chloride solution. It was shown that during the electrolysis of a sodium chloride solution with a concentration of 370 mg-eq/dm 3 at a current of 0.2 A in a three-chamber electrolyzer with an iron anode, an iron chloride solution is formed in the anolyte at pH <4.9. The rate of concentration of NaOH to catholyte and FeCl 3 to anolyte increased along with the current density. It was found that in order to increase the concentration of iron (III) chloride in the anolyte at relatively low concentrations of sodium chloride solution, it is advisable to gradually renew the demineralized solutions in the working chamber.
In this work the reagent purification of aqueous solutions from sulfates with the use of red sludge of the Nikolaev alumina plant processes were investigated. This sludge, according to chemical analysis, contains a sufficiently large amount of alumina (up to 18 %) and calcium oxide (up to 10 %) and along with calcium silicate and iron oxides contains sodium and calcium aluminates. The ability of sodium aluminate to be deposited from a solution of sulfates in the form of calcium sulfoaluminates was used in the work to purify water from sulfate anions. The process takes place when treating the solution with sludge and lime suspension. It is shown that when red sludge is applied in the amount of 1–50 g/dm3 during magnesium sulfate solutions liming, water is purified from sulfate anions. The degree of water purification reaches 50–70 %. It was found that the efficiency of sulfate extraction is significantly dependent on the consumption of lime and increases slightly with increasing sludge consumption over 1 g/dm3. The dependence of the efficiency of sulfate extraction from water on their initial concentration is determined. It was found that at the initial concentration of sulfates up to 1000 mg/dm3 at the expense of lime 3–12 mg-eq/dm3 the residual concentration of sulfates decreases to 236–460 mg/dm3, and at the concentration of sulfate anions about 2000 mg/dm3 their concentration decreases to 550–830 mg/dm3 at a lime consumption of 30 mg-eq/dm3 regardless of the sludge consumption. The degree of extraction of sulfates from solutions reaches 40–73 %.
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