Approach for Capacitive Deionizing the RO Reject via Developed Carbon-Coated Nickel Foam-Based Electrode

Abstract

Reverse osmosis (RO) has been an extensively implemented membrane technology for both domestic and industrial use. This wide implementation has been possible due to the availability of potable drinking water with high quality, but the RO concentrate volume associated with this technology has a significant limitation. As an alternative, a desalting technique, called capacitive deionization (CDI), was explored for purifying/treating salt contaminated water. In the present article, biomass-derived active material was coated on nickel foam, which resulted in efficient electrodes for ion sorption. The developed electrode was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which revealed a specific capacitance of 49.72 F/g and a resistance of 2.15 Ω. Moreover, its implications were explored for deionizing a concentrated stream of 500–1,500 ppm total dissolved solids (TDSs) in batch mode via the potential application of 1.2 V. An electrosorption capacity of 22.98 mg/g was obtained with salt adsorption rates of 0.51 mg · g−1 · min−1. The application of fabricated biochar-coated nickel foam electrodes was explored by treating the collected samples from domestic and commercial RO units located in Malviya Nagar, Jaipur, India, and it was found that treated water characteristics were well within the prescribed standards.