Liquid-liquid extraction process of amino acids by a new amide-based functionalized ionic liquid

The cost of separation and purification of amino acids accounts for more than 80% of their total production expenditure. Thus, investigation into new separation technology is of great importance. In this paper, a new hydrophobic amide-based functionalized ionic liquid ([EimCH 2 CONHBu]NTf 2 ) was designed and synthesized for the extraction of amino acids. From the preliminary experiments we found that the ionic liquid has a special selectivity for tryptophan (Trp) when pH = 0.5, and that its partition coefficient ( P IL/W ) can reach up to 10.02. Subsequently, important factors that affect the extraction process by [EimCH 2 CONHBu]NTf 2 were studied systematically. It was found that the extraction equilibrium could be achieved in 30 min. It was found that pH influences the P IL/W greatly; the smaller the pH value, the higher the P IL/W . When pH > p K 2 , the P IL/W is close to zero. With the increase of the volume ratio of the ionic liquid, extraction efficiency increases, while the P IL/W decreases. As for the effect of the initial concentration ( C 0 ) of tryptophan, P IL/W decreases with an increase of C 0 when [EimCH 2 CONHBu]NTf 2 is used as the extractant. From the investigation of the effect of temperature if was found that the extraction process of amino acid by functionalized ionic liquids is exothermic. Experiments on the recycling and reuse of [EimCH 2 CONHBu]NTf 2 were also performed, and it was found that the extraction efficiency of [EimCH 2 CONHBu]NTf 2 does not change after four cycles. Finally, the mechanisms were probed and the results show that the hydrogen bond formed between the acetyl group of the ionic liquid and the NH 2 group of tryptophan accounts for the higher extraction efficiency. A new functionalized ionic liquid [EimCH 2 CONHBu]NTf 2 is designed and synthesized with high extraction efficiency and special selectivity for tryptophan.