BACKGROUND
Reactive extraction is an efficient and highly selective technique for the separation of polar organic compounds. In this work, we used three kinds of extractants, namely acidic di(2‐ethylhexyl)phosphoric acid (D2EHPA), neutral tributyl phosphate (TBP) and basic trioctyltertiaryamine (7301) dissolved in three diluents with different polarity (strong‐polar n‐octanol, weak‐polar butyl acetate and non‐polar solvent oil) for optimization of a reactive extraction system. Based on the result, the reactive extraction kinetics of glycine by D2EHPA and the factors that affect the distribution ratio (D) were discussed in detail. Finally, the reactive extraction mechanism was analyzed, and an extraction model was proposed.
RESULTS
D2EHPA + n‐octanol is the best system for the reactive extraction of glycine. The apparent equilibrium constant K was calculated to be 1.71 L mol−1 and the physical extraction distribution constant (m) was 0.10. The reactive extraction equilibrium of glycine by D2EHPA can be reached in 1 h and room temperature is suitable for the extraction. D2EHPA reacted with glycine to form a 1:1 type ion‐pair complex, and the structure of the complex is less affected by aqueous pH. Chemical extraction is dominant in the extraction process. The distribution ratio D increases with the increase of D2EHPA concentration. pH and polarity of the diluent also have an influence on extraction efficiency.
CONCLUSION
The results provide preliminary practical information and a theoretical basis for the separation of glycine, which would be beneficial for the purification of glycine and the treatment of wastewater containing glycine. © 2021 Society of Chemical Industry (SCI).