Magnetic CNT-based electrode for efficient electro-adsorption of uranium

Various magnetic carbon materials have been employed for nuclide adsorption, yet there exists a research gap concerning their application in electro-adsorption for nuclide removal. In this study, a magnetic carbon nanotube nanocomposite (Fe3O4/CNT) was successfully synthesized as an electrode material through the hydrothermal method, involving the modification of minute Fe3O4 nanoparticles onto the surface of carbon nanotubes (CNT). Electrochemical assessments revealed that the Fe3O4/CNT nanocomposite exhibited a higher specific capacitance compared to Fe3O4 and CNT individually. The HRTEM image reveals a heterojunction structure formed directly between Fe3O4 and CNT, which facilitates electron transmission. The Fe3O4/CNT nanocomposite was utilized as an electrode in a capacitive deionization (CDI) device for U (VI)-contaminated wastewater purification. Experimental results demonstrated that the maximum U (VI) adsorption capacity of the Fe3O4/CNT electrode reached 287.53 mg/g at 298 K, and the adsorption process conformed to the Langmuir isotherm model. Kinetic analysis further indicated that the adsorption of U (VI) by Fe3O4/CNT followed a pseudo-second-order kinetic model. Additionally, the Fe3O4/CNT nanocomposite was transformed into a flowable electrode liquid and applied in a flow-electrode capacitive deionization (FCDI) system for U (VI) removal from aqueous solutions. Leveraging its superparamagnetic properties, the Fe3O4/CNT flow-electrode within the FCDI system could be rapidly recovered via a straightforward magnetic separation procedure. Notably, after nine consecutive runs of the FCDI device, the Fe3O4/CNT flow-electrode successfully concentrated a low-concentration U (VI) solution of 120 mg/L into a high-concentration solution of 1230 mg/L, thereby achieving the goal of water resource conservation and reduced storage requirements.