| abstract |
An aqueous solution of at least one valuable oxyanion containing molybdenum, tungsten, vanadium, or uranium is refined to lower the content of contaminant anions such as PO 4 -3 , SO 4 -2 , NO 3 - , Cl - , ClO 3 - , and ClO 4 - , by subjecting the solution to electrolysis at a pH of from 0.5 to 4.0 between a cation-permselective membrane and an anion-permselective membrane having tertiary amine or quaternary ammonium anion exchange groups, to cause contaminant anions to pass from the solution into the anolyte. Ammonium molybdates, tungstates, vanadates, and uranates are formed from the thus-refined solution by subjecting it to a second stage of electrolysis at a pH of at least 7 between a cation-permselective membrane and an anion-permselective membrane to cause valuable oxyanions to pass from the solution into an anolyte which comprises an aqueous solution of ammonia and to form the desired ammonium compound. |