Membrane-based solvent extraction and stripping of phenylalanine in HF contactors

Simultaneous membrane-based solvent extraction (MBSE) and membrane-based solvent stripping (MBSS) of phenylalanine (Phe) in hollow fiber (HF) contactors with a solvent containing 0.75 kmol m−3 of di(2-ethylhexyl)phosphoric acid (DEHPA) in n-alkanes have been studied. A circulating and one pass flow mode of operation of HF contactor in MBSE was used. The overall mass-transfer coefficient of Phe in MBSE and MBSS is concentration dependent, but in MBSE its value is practically constant at the feed concentrations above 20 mol m−3. The reaction-diffusion model fits experimental data well. While in modelling MBSE, the reaction of the complex formation on extraction interface of the first order is considered, the stripping reaction can be described by a general order rate equation of the order 1.8. The mean values of the lumped rate constant of the extraction and stripping reaction are 3.15 × 10−6 m s−1 and 6.74 × l0−8 mol(q−1) m(3q−2) s−1, respectively. The diffusion model overestimates greatly the value of the overall mass-transfer coefficient both in MBSE and MBSS. The structure of the complex considered was Phe(DEHPA)4(H2O)2. The analysis of mass-transfer resistances showed, that individual resistances based on the kinetics of acid-extractant complexes formation in MBSE and decomposition of the complex in MBSS are dominant and their contribution to the overall resistances is about 60 and 77%, respectively.