Liquid-Liquid Equilibria of the (water + phosphoric acid + propyl acetate) system

Phosphoric acid (PA) is an important chemical in production of detergents, agricultural feeds, activated carbon, soaps, and several phosphate fertilizers. Moreover, the importance of this acid is quickly increasing in many other fields. Phosphoric acid can be mainly produced by chemical wet and dry processes. Therefore, the extraction of this acid from water is an important problem in the wet process method. Solubility and tie-line data for the ternary system of water + phosphoric acid + organic solvent (propyl acetate) were determined and correlated at 308.15 K and atmospheric pressure. The solubility data were determined by cloud-point titration method. The tie line data were determined using acid-base titration and refractive index measurements. The material balance and cloud point procedure was used to check the experimental tie-line values. Since two liquid pairs are totally miscible (water + acid) and (acid + ester) and one liquid pair is partially miscible, a type-1 LLE phase diagram was obtained for this ternary system. The experimental tieline data were fitted using the UNIQUAC and NRTL thermodynamic models. The reliability or quality of the experimental data was determined through the Othmer-Tobias plot. Experimental distribution coefficients and separation factors were evaluated over the immiscibility area. The experimental results show the ability of propyl acetate for the extraction of phosphoric acid from aqueous solutions.

Extraction; ternary system; Phosphoric acid; ester; UNIQUAC; NRTL model