Efficient lead ion removal from water by a novel chitosan gel-based sorbent modified with glutamic acid ionic liquid

Three novel and highly effective AAIL-modified Chitosan (CS) adsorbents are presented. These three new CS-gels were prepared by an innovative synthetic method that uses amino acid ionic liquids (AA-ILs) to cross-link CS with, separately, glutamic acid, aspartic acid and alanine to give novel adsorbents Glu-AA-IL-CS (1), Asp-AA-ILCS (2) and Ala-AA-IL-CS (3) respectively. The effectively incarcerating host-structures (1)-(3) were characterized by a whole range of techniques including FT-IR, SEM, EDS and XRD. The differences amongst novel adsorbents (1)-(3) with regard to their rate and efficiency of removal of Pb2+ from aqueous solutions are explained in terms of the different electronic, structural and steric features of the three amino acids. The glutamic acid variant (1) is clearly shown to be the best-performing adsorbent by experimental tests and data in combination with infrared spectroscopy. The behaviour of adsorbents (1) follows pseudo-second-order kinetics, and accord best with the Freundlich adsorption isotherm.