Indole-functionalized cross-linked chitosan for effective uptake of uranium(vi) from aqueous solution

Abstract

Herein, a novel indole-modified cross-linked chitosan aerogel (IAA-CTSA) was fabricated by grafting 3-indoleacetic acid onto chitosan and adding glutaraldehyde as a crosslinking agent through a facile two-step one pot method. The uptake properties and mechanism of uranium (U(VI)) by the constructed IAA-CTSA were discussed. IAA-CTSA was discovered to be a powerful and effective adsorbing material for the capture of U(VI) at pH 6.5. Equilibrium was achieved within 6 h, and the adsorption process accorded well with the pseudo-second-order kinetic model, inferring the chemical adsorption was the rate controlling step. The maximum capture capacity for U(VI) reached 847.5 mg g⁻¹ calculated from the Langmuir model at 289 K. The removal efficiency for U(VI) of IAA-CTSA was strongly pH-dependent but insensitive to ionic strength. Furthermore, the removal efficiency of IAA-CTSA for U(VI) was maintained above 80% after 4 successive cycles using HCl and NaOH as eluents. The practical potential was tested using simulated U(VI) wastewater and illustrated that the resulting IAA-CTSA could be a competitive candidate for the elimination of U(VI) in simulated water environments. FTIR and XPS results illustrated that complexation, electrostatic and cation–π interactions were involved in the capture of U(VI). Briefly, the IAA-CTSA possesses good application prospects for wastewater remediation.