Recovery of high grade phosphoric acid from wet process acid by solvent extraction with aliphatic alcohols

High grade phosphoric acid was obtained using liquid-liquid extraction with aliphatic alcohols to separate metal and fluoride ion impurities in the aqueous phase. The influence of alcohol chain length, alcohol concentration, organic/aqueous phase ratio, temperature, shaking time and phosphoric acid concentration on P2O5 extraction was studied. Scrubbing with acid and stripping with water were also investigated. n-Octanol proved to be the most efficient and selective alcohol. The temperature had a slight positive effect and the extraction was enhanced by increasing P2O5 and with the increase of organic/aqueous phase ratio. The optimum organic/aqueous phase ratio for stripping was determined to be 2.0. For 9.2 M H3PO4, 98% of fluoride ion was removed whereas almost complete removal of iron, manganese, copper, cadmium and zinc was attained. (C) 2010 Elsevier B.V. All rights reserved.