North-Caucasian Mining-Metallurgical Institute, Vladikavkaz, Russia:

L. A. Voropanova, Professor, e-mail: lidia_metall@mail.ru
N. B. Kokoeva, Post-Graduate Student

Method of selective extraction of Fe (III) and Zn (II) ions by extraction from aqueous solutions was developed. Tributyl phosphate (С₄Н₉О)₃РО, relating to the oxygen-containing neutral extraction agents, was used as extraction agent. Mother liquors contained the soluble complex metal polychlorides. Water-soluble coordination compounds, containing complex anions ([ZnCl₃]^–, [ZnCl₄]^2–, [FeCl₄]^–, [FeCl₆]^3–, [Fe(H₂O)Cl₅]^2–, [Fe₂Cl₉]^3– etc) are formed during the dissolution of iron and zinc chlorides in NaCl and HCl solution. Formation of coordination (complex) compound between tributyl phosphate and metal polychlorides may be considered as a process of solvation of extracted metal salts by extraction agent. In the described process, extraction agent is portionwise added, having the concentrations of 2 mol/dm³ of HCl, 240 g/dm³ of NaCl, temperature of 60 оС and minimal contact time of solution and extraction agent. This makes possible the almost complete extraction of iron in the first portions of extraction agent with minimal extraction of zinc. After iron extraction, zinc is almost completely extracted by tributyl phosphate extraction with concentrations of 3 mol/dm³ of HCl, 240 g/dm³ of NaCl and temperature of 20 ^оС. This method provides high selectivity of the process of iron ion extraction from aqueous solutions of iron and zinc salts. This method is cost-effective due to the reduction of the cost of extraction agent during its portionwise addition. There is given the principal technological scheme of selective extraction of iron and zinc ions from aqueous solutions of their salts.

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