Synergistic solvent extraction studies of uranium(VI) using a combination of naphthenic acid and various neutral donors into benzene

The equilibrium extraction behavior of uranium(VI) using a benzene solution containing naphthenic acid either alone or combined with one of the adductants viz., diphenyl sulphoxide, dinonyl sulphoxide, tri-n-butyl phosphate, triphenyl phosphine oxide, tri-n-octyl phosphine oxide, triphenyl arsine oxide, 2,9 dimethyl 1,10-phenanthroline, 1,10-phenanthroline, 4,7-diphenyl 1,10-phenanthroline, 2,2′-bipyridyl and 2,2′-biquinoline is described. The enhancement in the extraction by addition of such neutral adducts is explained in terms of adduct formation of the metal chelates in the organic phase. The composition of the extracted species is obtained from slope analysis and pH0,5 values are also obtained. The effect of various parameters such as equilibrium pH, extractant concentration, various diluents on the extraction of U(VI) with 2% naphthenic acid has been carried out. Stripping or back extraction with various mineral acids was also studied.