Abstract:
In order to investigate the reduction performance of U(Ⅵ) in seawater by electrochemical technology, TiO
2 nanotube array electrode was firstly prepared by anodizing method, and then the amidoxime-modified TiO
2 electrode (PAO/TiO
2 electrode) was prepared by using the drip coating method to make the amidoxime functional groups loaded on the surface of TiO
2 electrode. The electrode was characterized by scanning electron microscopy, infrared spectroscopy and X-ray Auger electron spectroscopy. The uranium extraction performance of PAO/TiO
2 electrode in spiked seawater and real seawater was investigated respectively. The reaction mechanism was also proposed. The results of scanning electron microscopy and infrared spectroscopy show that the surface of the prepared TiO
2 nanoarray is smooth and the tube diameter is uniform. PAO containing amidoxime functional groups is successfully introduced on the surface of TiO
2 electrode. The results of performance test in spiked seawater show that PAO/TiO
2 electrode has a good ability to extract uranium. The extraction rate of uranium is 89.01% when the reaction time is 600 min. The pseudo-second-order kinetic model (
R2=
0.99583) can better describe the adsorption kinetic process of U(Ⅵ) on PAO/TiO
2 electrode than the first-order kinetic model (
R2=
0.98208), indicating that the adsorption process of the electrode material is dominated by chemical adsorption. The selective adsorption performance of U(Ⅵ) on PAO/TiO
2 electrode is better than that of other competitive metal ions (such as \mathrmVO_3^- , Fe
3+, Co
2+, Ni
2+, Cu
2+, Na
+, Mg
2+, Ca
2+). The desorption test was carried out on the electrode material after uranium adsorption, and the results show that the desorption rate of the electrode is 92.12% when 0.4 mol/L Na
2CO
3 used as the desorption agent. The test results in real seawater show that the extraction rate of uranium is 59.4% and the adsorption capacity of uranium is 4.07 mg/g when the reaction time is 28 h. X-ray Auger electron spectroscopy was used to characterize PAO/TiO
2 electrode before and after uranium adsorption. The results show that the electrode can reduce part of U(Ⅵ) to U(Ⅳ), and U(Ⅵ) is deposited in the form of UO
2 on the surface of PAO/TiO
2 electrode. PAO/TiO
2 electrode can extract uranyl ions from seawater by electroadsorption and electrodeposition, which is a potential electrode material. These results are expected to lay the foundation for the development of large scale sustainable uranium extraction systems from seawater.