Continuous purification of phosphoric acid in a microchannel

Solvent extraction is an economically efficient method widely used in the purification of wet phosphoric acid. In this study, microchannel was applied to promote mixing and purification of phosphoric acid during continuous production. For this aim, liquid-liquid extraction was conducted to purify phosphoric acid via methyl isobutyl ketone/tri-butyl phosphate mixtures. Additionally, the Box-Behnken experimental design method was used to survey the liquid-liquid extraction process. The effect of various operational parameters such as solvent concentration (45–65 %wt.), temperature (18-28˚C) and organic/aqueous phase ratio (2:1–6:1) at a constant flow rate of 70 ml/l was examined. Experimental results indicated that the microchannel at the residence time of 6.85 min could promote the extraction percentage of and sulfate removal more than 98% and 60%, respectively, compared to the batch extractor.