Isobaric vapor-liquid equilibrium for binary system related to the organophosphoric extractant of D2EHPA + n-dodecane and TBP + n-dodecane at 0.13, 2.40 and 6.67 kPa

Abstract

Vacuum distillation is selected as a technique for recycling in order to separate the mixture of a hydrometallurgical organophosphoric extractant from an organic diluent because of their low volatility and high selectivity. The experimental isobaric vapor-liquid equilibrium (VLE) data for the binary systems of di-(2-ethylhexyl) phosphoric acid (D2EHPA) + n-dodecane and tri-butyl phosphate (TBP) + n-dodecane were measured at pressures of 0.13, 2.40 and 6.67 kPa, using a glass vapor-liquid equilibrium ebulliometer. VLE data were generated in the form of T−x−y diagrams and checked for thermodynamic consistency via Herington area test and Van Ness point test. Data for all mixtures met the criteria of thermodynamic consistency and were found suitable for process modeling. At each pressure point, no azeotropic phenomenon was observed. Reduction in pressure of the system can significantly enhance the relative volatility and separation efficiency of both mixtures. At all pressure points, D2EHPA was noted to be more separable than TBP. Additionally, the experimental VLE results for all systems were found to have a good correlation with Raoult's law, Wilson and nonrandom two-liquid (NRTL) models. The corresponding binary interaction parameters were obtained by minimizing the deviation between the experimental and the calculated vapor phase composition and total pressure.