Capacitive deionization for removal of rare earth elements from aqueous solutions

Abstract

During the master’s thesis work the capacitive deionization system was constructed and the removal efficiencies at different concentrations for several rare earth elements from water solutions by capacitive deionization method were obtained using seven different electrode materials in the CDI-system. The electrode materials were fabricated based on the porous carbon. Each electrode material consists of the different porous carbon components and has different properties. The tested electrode materials were characterized using various characterization methods: Fourier-Transform Infrared Spectroscopy Analysis, Cyclic Voltammetry Analysis, Surface Area and Pore Size Analysis (BET-analysis), Scanning Electron Microscopy Analysis. Removal efficiency, electrosorption kinetics and electrosorption isotherms for electrosorption of metal ions by various electrode materials used in the process were studied here to examine each electrode material and to select the best one for the separation of each studied rare earth metal individually at different applied voltage in the system. The differential capacitance and thickness of electric double layer at the electrodes were calculated and compared to each other according to the certain parameters including the rare earth metal ions used during separation, applied potential and initial concentration of the metal ions in the solution. Some methods for improvement of separation efficiency as well as the future research ideas were suggested.