Sustainable capacitive deionization process for enhanced chromium reclamation using functionalized biochar electrode

Abstract

Water pollution, driven by urbanization and industrial growth, poses a significant threat, with chromium (Cr(VI)) discharge from industries like electroplating and tanneries. To address this issue, capacitive deionization (CDI) is explored for its low energy consumption and efficient removal of ionic contaminants. However, CDI faces challenges related to electrode costs and internal resistance. So, it is necessary to find a low-cost sustainable, functional electrode for the hazardous Cr(VI) reclamation without conventional additives to prevent internal resistance. Industrial Biochar, a product of pyrolysis enriched with carbon content, replaces conventional activated carbon and possesses better physicochemical properties. Similarly, Chitosan is a natural derived functional material enriched with functional groups that can adsorb the Cr(VI) ions. Apart from their functionality, they also improve the electrochemical stability and capacitance of the electrode. In response, the present study focuses on developing cost-effective functional electrodes using a biochar/chitosan (BC-CS) composite. The utilization of the chitosan enriches the physico-electrochemical properties and replaces the requirement of binder for the electrode development. The crosslinked BC-CS composite demonstrates a three-fold increase in specific capacitance compared to biochar electrode. Optimizing the ratio, the 1:1 BC-CS composite achieves a remarkable 96.7% chromium removal from a 100 ppm Cr(VI) solution in 3 h at 2 V. The composite also exhibits promising regeneration capabilities and shows potential in treating real-time chrome wash effluent from electroplating industries, indicating its viability for chromium water reclamation.