Integrating MnO2 nanostructures into activated carbon fiber felt for enhanced chromium ions removal in capacitive deionization

Capacitive deionization is a highly effective and potential approach for removing harmful substances from wastewater. This study investigated the impact of integrating MnO2 nanostructures onto activated carbon felt material (ACF/MnO2) by a hydrothermal technique to eliminate both Cr(VI) and Cr(III) under various conditions. It indicated a notable rise in the specific capacitance of the prepared material, with ACF/MnO2 exhibiting 65.8 F/ g as compared to ACF with 31.5 F/g for the Cr(VI) electrolyte. ACF/MnO2 demonstrated superior efficacy compared to ACF under similar initial concentrations and pH. During the charging phase at 5th cycle, a significant adsorption amount for Cr(VI) (8.5 mg/g) compared to Cr(III) (3.0 mg/g) was observed for ACF/MnO2. After undergoing 9 cycles at 1.2 V, the adsorption capacity of ACF/MnO2 reached 7.9 mg/g, surpassing the pristine ACF at 6.7 mg/g for Cr(VI) removal. The recovery rate during the discharging phase for Cr(III) at 65.4 % was higher than the 63.3 % recovery rate for Cr(VI) using ACF/MnO2 at 10th cycle. Moreover, the adsorption capacity and recovery rate for Cr species improved with increased potential. This study highlights the possibility of incorporating MnO2 nanostructures into activated carbon to remove Cr(VI) and Cr(III), offering an environmentally advantageous and sustainable solution through CDI.