Imidazolium-functionalized stable gel materials for efficient adsorption of phenols from aqueous solutions

Abstract

Abstract Recyclability of supramolecular gel adsorbents remains a challenging despite their efficiency in removal of organic pollutants from aqueous solutions. To solve the recyclability problem, stable supramolecular gel adsorbents have been developed based on imine chemistry. Ring-formation functionalization of imine gels based on polymerization of tetrafunctional amines tetrakis(4-aminophenyl)ethylene (TAPE) or tetrakis-(4-aminophenyl)methane (TAPM) with glyoxal yields imidazolium-functionalized gel materials, TAPE-G-Im and TAPM-G-Im. The gel materials have hierarchical porosity as indicated by SEM and N 2 adsorption–desorption isotherms, and are used as adsorbents for removal of phenolic compounds (phenol, p-cresol, bisphenol A, and 1-naphthol) from aqueous solutions. The materials pose excellent adsorption abilities towards the bicyclic phenols (bisphenol A and 1-naphthol). The maximum adsorption capacities on TAPE-G-Im are 175.42 mg g−1 for 1-naphthol and 153.20 mg g−1 for bisphenol A, and on TAPM-G-Im are 94.63 mg g−1 for bisphenol A and 81.38 mg g−1 for 1-naphthol, respectively. In comparison, tetraphenylethylene-based gel material has better performance. The gel adsorbents are stable without loss of the adsorption capacity up to at least 5 cycles, suggesting that the materials are promising phenols adsorbents in wastewater treatment.