Optimizing and Redesigning of Flow Electrode Deionization Cell for High Desalination Performance

Abstract

Clean water is fundamental to life on earth and to many other human existence elements. Nevertheless, natural freshwater sources are unable to fulfill the increasing demand for clean drinking water. Hence, the world must seek new, sustainable, and environmentally friendly desalination technologies to address the growing demand for clean water across the globe. The Flow electrode capacitive deionization (FCDI) technology has been recently developed and shows a potential solution to desalinate saline water efficiently with low energy consumption. However, the FCDI desalination approach is still in its early stage and faces several challenges that limit its applicability in real-life desalination applications. This research focuses on optimizing the flow electrode materials and developing innovative methodologies for the charges and ions transferring within the FCDI cell. For flow electrode material optimization, carbon is an ideal option to be used as flow electrode material due to its exceptional conductivity and large specific surface area that benefit from efficient ion-capacitive adsorption processes. However, the problem of bare carbon is the agglomeration and sedimentation in aqueous electrolyte leads to instability in the flow electrode, standing as a challenge for this desalination technology. In this research, we proposed a novel approach to address this issue by modifying the surface of carbon particles using direct blue (DB) molecules. Hence, increasing the affinity toward the aqueous electrolyte allows the formation of concentrated, stable carbon slurry electrodes and leads to highly active, long-term durable FCDI performances. Furthermore, to prompt charges and ions transfer within the FCDI cell, we employed carbon foam as current collectors to enhance the charge pathways in the flow electrode compartments. Additionally, we improved the ion diffusion kinetics and migration process by integrating the ion exchange resin (IER) approach in the feedwater channel. Through these improvements, our enhanced FCDI system displayed remarkable efficiency in desalinating seawater to the drinking water level. These improvements highlight the practicality of FCDI technology towards an efficient and low energy consumption technique and its applicability in real-world desalination.