Enhancing the charge percolation networks through the synergistic effect of conductive additives for the removal of Cr(VI) in FCDI

The natural environment and human health are gravely threatened by the issue of hexavalent chromium (Cr(VI)) contamination in water bodies. Therefore, it is imperative to replace the traditional removal methods with an updated Cr(VI) removal procedure. In this study, mixed activated carbon (AC), carbon nanotubes (CNT) and carbon black (CB) were used as components of the flow electrode slurry low-electrode capacitive deionization (FCDI), which was used for the removal and detoxification of Cr (VI) under various operating conditions. Performance evaluation revealed that, in comparison to traditional pure AC slurry, the filling effect of CB and the bridging effect of CNT effectively enhanced the electrical conductivity. An outstanding removal efficiency of 85.03% within 30 min and an ASRR of 13.53 μg cm⁻² min⁻¹ were achieved under an initial Cr(VI) feed concentration of 100 mg/L and a conductive additive content of 1% (CNT:CB = 1:1). Over the course of 12 cycles, FCDI converted 37.91% of highly toxic Cr(VI) to less harmful Cr(III) and decreased the Cr(VI) removal efficiency by 9.23%. Lastly, computational fluid dynamics (CFD) further validated the ternary composite slurry's capacity to form a robust charge transport network that enhances charge transfer. In conclusion, this study offers a promising FCDI technology for heavy metals removal.