Ionic liquid@β-cyclodextrin-gelatin composite membrane for effective separation of tea polyphenols from green tea

Abstract

A new kind of multi-component membrane was prepared by combining gelatin solution, porogen and an inclusion complex of ionic liquid (IL) and beta-cyclodextrin (β-CD) in a simple physical manner for selective separation of tea polyphenols (TPs) from green tea crude extracts. After screening, it was found that the resulting membrane containing the IL of dicationic N-vinylimidazole proline salt ([VIm]₂C₃[l-pro]₂) had the excellent performance for the enrichment of the target molecules. Then the newly-developed film was comprehensively characterized by scanning electron microscopy, conductivity, thermogravimetry and spectral analysis. Under pressure driving, the adsorption from an aqueous solution of a mixture of TPs and theophylline on IL@β-CD-Gel membrane showed that the adsorption capacity for TPs was 303.45 mg/g with removal percentages of 94.38%. The experimental data fit well with pseudo-second-order model and Freundlich model. By using this composite material, a new technology of membrane separation for selective adsorption of TPs was finally established.

Keywords: (−)-Epicatechin (PubChem CID: 72276); (−)-Epicatechin gallate (PubChem CID: 107905); (−)-Epigallocatechin (PubChem CID: 72277); (−)-Epigallocatechin gallate (PubChem CID: 65064); 1,3-Dibromopropane (PubChem CID: 8001); Beta-cyclodextrin; Beta-cyclodextrin (PubChem CID: 444041); Caffeine (PubChem CID: 2519); Gelatin; Ionic liquid; Membrane separation; N-Vinylimidazole (PubChem CID: 66171); Tea polyphenols; Theophylline (PubChem CID: 2153); l-Proline (PubChem CID: 145742).