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.