Simultaneous Fractionation, Desalination, and Dye Removal of Dye/Salt Mixtures by Carbon Cloth-Modified Flow-electrode Capacitive Deionization

Efficient remediation and synchronous recovery of uranium by phosphate-functionalized magnetic carbon-based flow electrode capacitive deionization

Through the design of flow electrodes, flow electrode capacitive deionization (FCDI) enables the efficient remediation of uranium-contaminated water to meet World Health Organization (WHO) standards (uranium ≤ 30 ppb), while concurrently facilitating the recovery of uranium from the flow electrode slurry. In this work, the phosphate-functionalized magnetic carbon-based flow electrode (OMPAC) was synthesized by simply co-precipitation and oxygen plasma treatment. The enhanced conductivity of OMPAC accelerated the efficient remediation of surface water contaminated with multiple nuclides, due to the improved charge-transfer capability facilitated by the introduced magnetic particles (Fe, Fe3O4, Fe3C) and heteroatoms (O, P). The uranium in feed solution was selectively adsorbed by OMPAC in flow electrode slurry, benefiting from the multiple strong sorption interactions between U(VI) and C=O/P=O/P-O groups, as well as the redox reactions between U(VI) and Fe (0/II). After four batch cycles, the average uranium removal rate by OMPAC was maintained at 97.84 %, while the recovery rate of uranium from OMPAC reached 78.2 %, demonstrating the excellent long-term performance and synchronous uranium recovery capability in FCDI. This study provides feasibility guidance for the remediation of radioactive pollution and the strategic reuse of resources via the FCDI technology.

Interface gypsum deposition in flow-electrode CDI treating brackish water: Impacts and mechanisms

Flow-electrode capacitive deionization (FCDI) is a promising electrically driven technology for brackish water desalination, but it suffers from scaling issues in the concentrate chamber when treating brackish water with high levels of SO42- and Ca2+. In addition, how the key components (e.g., flow electrodes, spacer and ion exchange membranes) induce scaling in the concentrate chamber remains poorly understood. Therefore, this study systematically investigated the roles of the FCDI's components playing in the scaling process. Results showed substantial pressure loss in the concentrate chamber, which increased by 108% due to the scaling. The characterization results revealed that the scale attached to the surface of the spacer and membranes was gypsum. Gypsum crystallization experiments highlighted the crucial role of the cation exchange membrane and spacer in the heterogeneous nucleation process, which significantly shortened the induction time compared to the homogeneous nucleation process. The surface properties, such as the surface energy and surface charge, were found closely related to gypsum nucleation. In summary, the results of this work pave the way for understanding the gypsum nucleation process in FCDI continuously desalinating brackish hard water, potentially aiding in scaling removal and system optimization for broader environmental applications.

Exploring the potential of flow-electrode capacitive deionization for domestic and industrial wastewater treatment: a review

Flow-electrode capacitive deionization (FCDI) is an innovative approach for removing charged ions from untreated water, utilizing the interaction between ions and flow carbon electrodes. A review of recent publications on FCDI reveals a predominant focus on salt removal from water (desalination) and electro-sorption processes. Though desalination is just one step in improving the water quality, it is worthwhile looking at the research in the context of FCDI techniques that involve other water treatment methods. This paper offers a detailed review of recent literature on FCDI applications in wastewater treatment. Given the broad scope of wastewater treatment, the specific areas where FCDI shows promise, including removal of heavy metal and radioactive elements, organic micropollutant elimination, halogen removal, and resource recovery, are addressed. Additionally, we assess the current research landscape and propose potential future directions in this evolving field.

Electro-intensified simultaneous decontamination of coexisting pollutants in wastewater

The treatment of wastewater has become increasingly challenging as a result of its growing complexity. To achieve synergistic removal of coexisting pollutants in wastewater, one promising approach involves the integration of electric fields. We conducted a comprehensive literature review to explore the potential of integrating electric fields and developing efficient electro-intensified simultaneous decontamination systems for wastewater containing coexisting pollutants. The review focused on comprehending the applications and mechanisms of these systems, with a particular emphasis on the deliberate utilization of positive and negative charges. After analyzing the advantages, disadvantages, and application efficacy of these systems, we observed electro-intensified systems exhibit flexible potential through their rational combination, allowing for an expanded range of applications in addressing simultaneous decontamination challenges. Unlike the reviews focusing on single elimination, this work aims to provide guidance in addressing the environmental problems resulting from the coexistence of hazardous contaminants.