Synthesis of Amidoxime-Grafted Activated Carbon Fibers for Efficient Recovery of Uranium(VI) from Aqueous Solution

A novel fibrous sorbent, amidoxime-grafted activated carbon fibers (ACFs-AO), was prepared using a chemical grafting method and tested for the efficient removal of uranium from aqueous solution. The sorbent was characterized using X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, elemental analysis, thermogravimetric analysis, and Brunauer–Emmett–Teller. The effects of pH, contact time, initial concentration, and temperature on the sorption of U(VI) were investigated. The sorption of U(VI) on ACFs-AO obeyed the pseudo-second-order model and Langmuir isotherm. The sorption capacity of ACFs-AO for U(VI) (about 191.6 mg/g) was much higher than that of activated carbon fibers (ACFs) (about 70.52 mg/g), which was mainly attributed to surface complexation between U(VI) and the amidoxime group on ACFs-AO. Additionally, the thermodynamic parameter results showed that the sorption process of U(VI) was spontaneous, feasible, and endothermic. Moreover, ACFs-AO adsorbed U(VI) selectively in an aqueous solution containing competitive ions, and was regenerated and reused efficiently. The findings of this work indicate that ACFs-AO could be a promising sorbent for the effective removal of U(VI) from aqueous solution.