Enhanced capacitive deionization of Cr(VI) using functionalized metal carbide 2D framework and badam tree leaf-derived carbon as the asymmetric electrode materials

The development of high-value-added biomass-derived carbonaceous as electrode material from agricultural wastes has received considerable attention. In this study, the activated biochar (AB) derived from the badam tree leaves (BTL) and functionalized 2D metal-carbide materials, V2AlC-OHx, have been successfully synthesized by alkaline treatment and microwave-assisted hydrothermal method, respectively, and then used as the asymmetric electrode materials for capacitive deionization application to remove Cr(VI) ions from aqueous solutions. The large specific surface area and the interconnected meso- and macro-porous channels of AB provide active sites and short ion diffusion paths to accelerate ion transport and electrosorption. In addition, the highly crystalline 2D architecture of V2AlC-OHx offers suitable lattice fringes for electron transfer. The conversion of Cr(VI) into Cr(III) on the surface of V2AlC-OHx, followed by the capture of Cr(III) onto the AB cathode has triggered the enhanced removal of Cr(VI). The AB//V2AlC-OHx asymmetric CDI device exhibits superior deionization performance for Cr(VI) removal with a specific electrosorption capacity of 47.2 mg g−1 and removal efficiency of 99 %. Excellent cyclic performance for at least 20 adsorption–desorption cycles is also observed, indicating the excellent durability of the fabricated materials. These results demonstrate that AB and V2AlC-OHx are promising CDI electrodes for the removal of metal ions and other hazardous pollutants from industrial effluents.