Photoreductive Stripping of Vanadium in Solvent Extraction Process for Separation of Vanadium and Molybdenum

Abstract

The separation of vanadium and molybdenum by solvent extraction followed by photoreductive stripping was investigated, using tri-n-octylmethylammonium chloride (TOMAC) as extractant. A low-pressure mercury lamp and a halogen lamp were used as light sources. Pentavalent vanadium was reduced photochemically to tetravalent or trivalent vanadium in organic solution as well as in aqueous solution, using isopropyl formate as a radical scavenger. The photoreduction of vanadium in TOMAC/benzene phase containing vanadyl and molybdate anions allowed the vanadium to be stripped into an aqueous phase selectively, leaving the molybdenum in the organic phase. The stripping yield of vanadium reached 100%. The separation factor of vanadium and molybdenum by single extraction followed by single selective stripping was 1000–2000 when using the mercury lamp and 170–430 when using the halogen lamp. The organic solution was not damaged by the photoreductive stripping and was reusable for repeated extraction and stripping. © 1993, The Society of Chemical Engineers, Japan. All rights reserved.