Розробка способу перероблення концентратів процесів опріснення води з отриманням алюмінієвих коагулянтів

The process of processing concentrates and eluates formed during desalination of natural surface, artesian, and mine waters with increased mineralization by reverse osmosis and ion exchange methods has been studied. Specifically, this study examined the processes of processing sodium chloride solutions and mixtures of sodium chloride and sodium sulfate via electrodialysis, and obtaining alkaline and aluminum salt solutions, were examined. Aluminum salts were produced using AD-31 aluminum anodes. A stainless-steel plate of grade 12H18N10T was used as the cathode. The process was conducted at current densities ranging from 1.67 to 8.33 A/dm² in two- and three-chamber electrolyzers using MK-40 cation-exchange membranes and MA-41 anion-exchange membranes. In all experiments, alkaline solutions were obtained in the cathode region and aluminum salt solutions in the anode region. When using a three-chamber electrolyzer, the salt solution was placed in the working chamber, separated by a cation-exchange membrane from the catholyte and an anion-exchange membrane from the anode zone. During electrolysis, alkali concentration occurred in the catholyte and aluminum salts in the anolyte. In the three-chamber electrolyzer, desalination occurred in the working chamber due to the diffusion of sodium ions through the cation-exchange membrane into the catholyte and the diffusion of anions (chlorides and sulfates) through the anion-exchange membrane into the anode area. Aluminum oxidation in the anode area resulted in the formation of Al³⁺ cations, and in the presence of chlorides, aluminum chloride was formed. Hydrolysis of aluminum chloride partially produced aluminum hydroxychlorides, predominantly forming 1/3 aluminum hydroxychloride. Before electrolysis, the anode chamber pH was adjusted to 2.5 with hydrochloric acid. During electrolysis, the pH was maintained at 2.5–3 due to electrode reactions. The salt content in the working chamber decreased to 2–20 mg-eq/dm³. In a two-chamber electrolyzer, electrolysis produced alkali in the catholyte and aluminum chloride in the anolyte. Conversion of sodium chloride in the anolyte was limited due to poisoning of the cation-exchange membrane by aluminum ions.