ZnO site-occupying effect assisted regulation of nanoporous carbon network to enhance capacitive deionization for copper ions removal

Abstract

Capacitive deionization (CDI) technology, based on the electric field ion capture mechanism, holds significant application prospects for purifying copper ions (Cu²⁺) from industrial wastewater. The development of electrode materials is crucial for enhancing capacitive Cu²⁺ removal. Herein, the three-dimensional nanoporous carbon network is prepared from agricultural waste rice husk using basic zinc carbonate as the pyrolytic activator. It is found that the ZnO site-occupying effect, stemming from the pyrolysis activator, exerts a pronounced regulatory influence on the porous structure of carbon network. The carbon electrode exhibits a satisfactory specific capacitance of 256.2 F g⁻¹ at 0.5 A g⁻¹. More importantly, the assembled symmetrical CDI cell demonstrates an excellent electrochemical adsorption capacity of 60.5 mg g⁻¹ for Cu²⁺. Such exceptional capacitive deionization performance can be attributed to the synergistic effect of the electrochemical double-layer and electrochemical reduction during the adsorption process of Cu²⁺. Thus, this research offers a promising strategy for efficient wastewater treatment.