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Abstract
In the separation processes of amino acids, zwitterionic species are prevented from being exchanged because of the spatial proximity of two opposite charges on the molecule. There would be a high chemicals cost due to the need to change the solution pH. It is therefore desirable to develop a novel recovery technology for amino acids in the middle pH range. A series of extraction equilibrium experiments for L-phenylalanine (L-phe) with di(2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in n-octane was carried out. The effects of L-phe concentration, D2EHPA concentration, and pH on the distribution ratio were discussed in detail. The infrared spectrogram of the organic-phase-loaded solute illustrated that the pH condition had little effect on the structure of the complex. There are proton-transfer and ion-exchange reactions in the extraction. One L-phe molecule is extracted by forming a complex with two dimeric D2EHPA molecules. An expression of the equilibrium distribution was proposed.
ACKNOWLEDGMENTS
Valuable advice from and discussions with Prof. Lilian Xu and Prof. Weizhi Li, Analytical Center of the Chemical Engineering Department, are greatly appreciated.