EXTRACTION OF PHOSPHORUS, ARSENIC AND OR SILICA FROM SODIUM TUNGSTATEOR MOLYBDATE SOLUTIONS WITH PRIMARY AMINE AND TRIBUTYL-PHOSPHATE AS SOLVENTS .2. MECHANISM OF EXTRACTION OF PHOSPHORUS, ARSENIC AND SILICA FROM TUNGSTATE AND MOLYBDATE SOLUTIONS/

The mechanism of the removal of phosphorus, arsenic and silica from tu ngstate or molybdate solutions by synergistic extraction with primary amine and tributyl phosphate (TBP) was investigated. Phosphorus, arsen ic and silica were considered to be extracted into the organic phase a s heterotungstic or heteromolybdic acids. The composition of the extra cted species is strongly dependent on the concentration of tungsten an d molybdenum and equilibrium pH values of the aqueous phase, An extrac tion mechanism based on the formation of hydrogen bonding between the primary amine, TBP and heteropoly acids is proposed. The loaded organi c phase was characterized by UV and IR spectra and by molar conductanc e, It is proposed from the experimental results that the proton transf er from the heteropoly acids to the primary amine in the extracted spe cies occurs intramolecularly, resulting in the formation of ion-associ ated species, because the primary amine is a weak base and heteropoly acids are strong acids. The mechanism of proton transfer is also propo sed.