Solvent extraction of tungsten and molybdenum from acidic solutions

Solvent extraction of tungsten and molybdenum has been investigated using tri-n-octylamine (TOA) and di-2-ethylhexyl phosphoric acid (D2EHP) in benzene. Tungsten and molybdenum were very well extracted by TOA and no problem was encountered from the point of view of the industrial application of the method. The lack of extraction of tungsten from acidified tungstate solution using D2EHP as the extractant confirmed that tungsten does not exist as a cationic form in the acidic solution. The extraction of molybdenum from acidic solution using D2EHP as the extractant confirmed that molybdenum exists in acidic solutions as both anion and cation species in equilibrium. The results show that the anionic species are much more predominant in the aqueous phase. The extractibility of molybdenum with D2EHP suggested the possibility of separating tungsten and molybdenum by a solvent extraction method. The extraction of molybdenum in the presence of tungsten with 10% D2EHP in benzene was investigated. Full extraction system with D2EHP was not achieved with the higher concentrations of tungsten present. (author)