Concentration and purification of wet industrial phosphoric acid by electro-electrodialysis

The concentration of phosphoric acid by electro-electrodialysis is limited by proton leakage through the AEM. Two membranes are studied RAI 5035 from RAIPORE (USA) and ARA from Solvay (France). With the ARA membrane, the concentrated phosphoric acid (4 m) was obtained with an interesting yield and a low concentration of metal impurities (Fe3+, Al3+, Mg2+). The introduction of ammonium in the anolyte reduced the proton leakage and increased the current efficiency of the acid recovery.