Unraveling the role of field strength on Sr2+ removal in flow-electrode capacitive deionization systems

With the widespread application of nuclear energy, the risk of radioactive wastewater containing Sr 2+ is increasing. Flow-electrode capacitive deionization (FCDI) based on carbonaceous materials is an emerging desalination technique with great promise for treating micro-polluted Sr 2+ wastewater. However, understanding of the key factors that govern the performance is still lacking due to complex mass and electron transfer across multi-scales. Herein, we elucidated the influence of the electric-, concentration- and heat- fields on the deionization performance in FCDI, through which a strategy to enhance the performance for selective removal of Sr 2+ was developed. Such a strategy was fulfilled by first constructing flowing electrodes using two types of one-dimensional carbon nanomaterials with similar pore structure but differ significantly in electrical conductivity. By optimizing properties of the flowing electrode and operation conditions, the driving forces originated from electric-, concentration- and heat-fields were enhanced, delivering a high removal rate of 5.29 μg SrCl 2  cm −2  min −1 and a low energy consumption of 2.89 J g −1 SrCl 2 . The effects of field strength unraveled and the FCDI system constructed in this study would pave the way for practical applications of this technology.