Electrodeposited polypyrrole/biomass-derived carbon composite electrodes with high hybrid capacitance and hierarchical porous structure for enhancing U(VI) electrosorption from aqueous solution

Effective separation and decontamination of U(VI) from radioactive wastewater is beneficial to both the sustainable development of nuclear energy and the reduction of radioactive pollution. Electrosorption has recently emerged as a promising technology for U(VI) separation from solution. Herein, the biomass-derived carbon/polypyrrole (BC/PPy) electrodes with high hybrid capacitance and hierarchical porous structure were fabricated by the electrodeposition of PPy on the BC surface for using as pseudocapacitive electrodes for enhancing U(VI) electrosorption. The electrochemical measurements showed that the BC/PPy electrodes exhibited a significant capacitance-controlled behavior in which the capacitance contributions could be quantized. The U(VI) electrosorption by BC/PPy was conducted in a capacitive deionization (CDI) system. The results suggested that among different BC/PPy composites, BC/PPy-3 presented best electrosorption performance, owing to the improved electric conductivity, the hierarchical porous structure, and the synergistic effect of hybrid capacitance (EDL and pseudo-capacitance). The electrosorption isotherms and kinetics were found to be well-simulated by Langmuir and PFO models. The BC/PPy-3 showed a maximum electrosorption capacity of 237.9 mg/g for U(VI) at the applied voltage of 0.9 V, it also exhibited good recycling stability after several electrosorption-desorption cycles. This work provides a promising strategy to the fabrication of cost-effective biomass-derived carbon/conductive polymer composite electrodes for the effective CDI treatment of radioactive wastewater.