REVERSE MICELLAR EXTRACTION AND BACKEXTRACTION OF L-LYSINE WITH 3 DIALKYL SODIUM PHOSPHINATES IN PENTANOL/ISOOCTANE MIXTURES

The effects of pH, salt concentration, and structure of the surfactant head on the reverse micellar extraction and backextraction of L-lysine in pentanol/isooctane mixtures have been comparatively studied. The surfactants used were bis(2,4,4-trimethylpentyl) sodium phosphinate (NaPOO), bis(2,4,4-trimethylpentyl) sodium monothiophosphinate (NaPSO), and bis(2,4,4-trimethylpentyl) sodium dithiophosphinate (NaPSS). Since all three surfactants have the same two hydrocarbon tails and differ only in their polar heads, their comparative study gives some insight into the effect of the surfactant head group on the reverse micellar extraction and backextraction of amino acids. The results show that the nature of the surfactant head, the pH, and the salt concentration have a major effect on the reverse micellar extraction of L-lysine. The percent of L-lysine extracted to the organic phase, at fixed surfactant and pentanol concentrations, decreased in the order NaPSS > NaPSO > NaPOO. The exchange with the three surfactants can be easily reversed for the backextraction of amino acids into a new surfactant-free aqueous solution.