Extraction of Tungsten with Trialkylamine- Effect of pH

0166184 - UCHP-M 20013040 RIV CZ eng J - Journal Article
Procházka, Jaroslav - Heyberger, Aleš - Horáček, Jan - Volaufová, Eva - Voborská, Jitka - Macháčková, Eva
Extraction of Tungsten with Trialkylamine- Effect of pH.
Collection of Czechoslovak Chemical Communications. Roč. 66, č. 9 (2001), s. 1407-1419. ISSN 0010-0765
R&D Projects: GA ČR GA104/98/1440
Institutional research plan: CEZ:AV0Z4072921
Keywords : liquid-liquid extraction * ion-exchange * equilibrium
Subject RIV: CI - Industrial Chemistry, Chemical Engineering
Impact factor: 0.778, year: 2001

Extraction equilibrium in the system aqueous solution of sodium tungstate-solution of trialkylamine in a mixed diluent was investigated. A tertiary amine with C-7-C-9 straight alkyl chains was dissolved in a mixture of tributyl phosphate and kerosene and presaturated with sulfuric acid to give normal trialkylamine sulfate. Extraction isotherms at 25 degreesC and at several constant values of equilibrium pH were measured in a broad range of aqueous tungstate concentrations. pH 2.0-6.0 was adjusted by addition of sulfuric acid during equilibration. The equilibrium tungstate and sulfate contents in both phases were determined. A typical tungstate isotherm exhibits a steep ascending part in the low concentration range, corresponding to the region of anion exchange, and a flat part in the high concentration range, where the acid content in the organic phase is virtually exhausted. The level of the flat part decreases with growing pH, corresponding to the increasing number of negative charges per tungsten atom in the tungstate polyanions extracted. At pH > 5, also the effect of hydrolysis of amine sulfate could be detected.
Permanent Link: http://hdl.handle.net/11104/0063329