combined method for processing spent acid etching solution obtained during manufacturing of titanium products

Possessing high strength, low density and significant chemical resistance, titanium has found wide application in various fields of the national economy – the chemical industry, aviation and rocket technology, mechanical engineering, medicine, etc. the production of titanium products is hampered by a fairly strong oxide film covering its surface. removal of the oxide film from the surface of titanium workpieces is carried out by etching in solutions of mineral acids of various compositions. a spent acid etching solution (saes) is formed, containing titanium salt and the remainder of unreacted acids. almost all etching solutions contain hf and one of the strong acids. this is h2so4, hcl or hno3. thus, the saes includes ions of titanium, fluorine or chlorine, orsulfate, or nitrate. saes is quite toxic and must be diluted or cleaned several times before being discharged into a reservoir. most of the methods used to extract impurities contained in saes lead to a decrease in their content. as a result of such purification, there is a loss of substances contained in saes in significant quantities and of interest for further use. the work presents experimental results obtained from the combined processing of saes containing titanium fluoride, hydrofluoric and hydrochloric acids. at the first stage, saes is treated with sodium hydroxide. the resulting titanium hydroxide precipitate is filtered off. at the second stage, the filtrate containing sodium fluoride and chloride is processed in a membrane electrolyzer. in this case, not only the extraction of sodium salts from the filtrate occurs, but also the production of sodium hydroxide and a mixture of hydrofluoric and hydrochloric acids. sodium hydroxide can be used for processing saes, and a mixture of acids for etching titanium workpieces.