Phosphoric acid purification by a membrane process: Electrodeionization on ion-exchange textiles

The electroextraction of mineral impurities from phosphoric acid was achieved by electrodeionization process (EDI) combining ion-exchange membranes (IEM) and textiles (IET). The treated solution was an industrial phosphoric acid solution at high concentration (54% P2O5) and five times diluted (11% P2O5) containing mainly the following heavy metals: magnesium, iron, chromium, zinc, cadmium. Immersion of textiles in phosphoric acid solutions at various concentrations showed their good chemical resistance in this medium. Exchange kinetics with IET was very fast. The use of two kinds of textiles (cation and anion exchange) indicated that the metal pollutants may be found in both cationic and anionic form. From EDI measurements, purification ratios close to 30% for all elements (excepted for Fe) were obtained after 5 h of treatment.