UO22+ capture using amidoxime grafting low-cost activated carbon (AO-AC) from solution: Adsorption kinetic, isotherms and interaction mechanism

Uranium, an efficient energy source and potential radioactive contamination, mainly existed in the form of UO22+ or [UO2(CO3)3]4− complexes in liquid-phase environmental. Effective recovery of uranium is of great significance to global energy supply and ecological environment protection. Herein, we sought to immobilize amidoxime groups on inexpensive, readily available activated carbon surfaces for UO22+ capture. Sequencing batch adsorption experiments showed that the maximum adsorption capacity of amidoxime-functionalized activated carbon (AO-AC) reached 65.33 mg/L. Linear fitting demonstrated that the adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. Besides, AO-AC exhibited excellent selectivity and removal efficiency in a variety of coexisting ions and low concentration uranium-spiked aqueous solution. AO-AC can easily regeneration in 0.1 M HCl solution, and the removal efficiency was maintained at 88.32 % after five consecutive adsorption-desorption experiments. XPS and FTIR analysis confirmed that the simultaneous complexation of UO22+ with C-NH2 and -C-NOH was the main removal mechanism.