Scale-up desalination: Membrane-current collector assembly in flow-electrode capacitive deionization system

Abstract

Salt removal from seawater/wastewater using flow-electrode capacitive deionization (FCDI) is of particular interest, but scale-up desalination is limited by low water production, high energy consumption and complex cell configuration. In this study, an innovative FCDI system is described that uses integrated desalination modules equipped with membrane-current collector (MCC) assembly, and thereby named as MCC-FCDI system. A single desalination module design provides an average salt removal rate (ASRR, 0.3 - 0.44 µmol/(cm2·min)) close to that of the classic FCDI system (with a graphite current collector design), but the design requires a much lower infrastructure investment, device size and energy cost. More importantly, our design enables simultaneous operation of multiple modules in the shared flow-electrode tank, easily realizing scale-up desalination. Evidence is provided by the results of the multi-module operation: multi-modules isolated closed-cycle (MICC) and multi-modules short-circuited closed-cycle (MSCC). For instance, the MICC configuration showing nearly twice the desalination performance over ~ 50 h of operation compared to that of the single ICC operation. The results indicated that in addition to making the device suitable for practical application, the Ti-mesh MCC with a woven network enables the flow electrode to achieve substantial ion adsorption capacity due to the efficient update of fresh carbon particles. In short, the results of this study showed that MCC-FCDI is a promising desalination system for scale-up applications, providing a new reference and guidance for device design.