Mass-transfer characteristics of a spiral-channel SLM module in pertraction of phenylalanine

Abstract

Transport of phenylalanine (Phe) through a supported liquid membrane (SLM) containing di-(2-ethylhexyl) phosphoric acid (DEHPA) as carrier in a spiral-channel module was studied. The value of the molar flux of Phe through SLM increases with the velocity of the feed phase in the channel. However, soon at a velocity of about 1.5–4 cm.s−1, the maximum value is achieved. With increasing initial concentration of Phe in the feed phase, the transport rate increases. An increase in the concentration of DEHPA in the solvent did not result in an increase of the transport rate despite the fact that the value of the distribution coefficient increased proportionally. This is related to the slower kinetics of decomposition of the complex on the stripping interface. An analysis of mass-transfer resistances of Phe in pertraction through SLM showed that decisive resistances are based on the kinetics of chemical reactions of complex formation and decomposition, and their share in the overall resistance is about 25 and 35%, respectively. The lifetime of SLM with DEHPA as the carrier is less than 1 day for dilute aqueous feeds unsaturated with the membrane phase. It increases with the concentration of DEHPA that is connected with a relatively high solubility of DEHPA in diluted aqueous solutions. The spiral-channel module can be used for testing solvents for pertraction and membrane-based solvent extraction under defined hydrodynamic conditions.