Wet process phosphoric acid purification by solvent extraction using N‐octanol and tributylphosphate mixtures

Abstract BACKGROUND Solvent extraction using organic extractants is an important technology for purifying wet process phosphoric acid. The purification of the wet process phosphoric acid by liquid–liquid extraction using solvent mixtures of N‐octanol and tributylphosphate has been investigated. RESULTS The purification process comprised extraction, scrubbing and stripping operations. The extraction conditions, i.e. shaking time, temperature, composition of solvent mixtures and P 2 O 5 concentration for purification of the wet process phosphoric acid were studied. The phase diagram of the pseudo‐ternary system H 3 PO 4 ‐H 2 O ‐solvent mixtures at 313.15 K was determined. The McCabe –Thiele diagram showed that three counter‐current stages achieved about 91 wt% P 2 O 5 extraction at 313.15 K. Scrubbing and stripping operations using pure phosphoric acid with 10 wt% P 2 O 5 and doubly distilled water, respectively, were studied. CONCLUSIONS The phosphoric acid finally produced was found to be high grade which met the special requirements of the user. Optimization of the extraction conditions and system was capable of providing academic and technical foundations to realize industrial production. © 2012 Society of Chemical Industry