Membrane-Current\nCollector-Based Flow-Electrode Capacitive\nDeionization System: A Novel Stack Configuration for Scale-Up Desalination

Abstract

The stack configuration in flow-electrode\ncapacitive deionization\n(FCDI) has been verified to be an attractive and feasible strategy\nfor scaling up the desalination process. However, challenges still\nexist when attempting to simultaneously improve the desalination scale\nand the cell configuration. Here, we describe a novel stack FCDI configuration\n(termed a gradient FCDI system) based on a membrane-current collector\nassembly, in which the charge neutralization enables the in situ regeneration\nof the flow electrodes in the single cycle operation, thereby realizing\na considerable increase in the desalinating performance. By evaluating\nstandardized metrics such as the salt rejection, productivity (<i>P</i>), average salt removal rate (ASRR), energy-normalized\nremoved salt (ENRS), and TEE, the results indicated that the gradient\nFCDI system could be a performance-stable and energy-efficient alternative\nfor scale-up desalination. Under optimal operating conditions (carbon\ncontent = 10 wt %, feed salinity = 3000 mg L^–1,\ncell voltage = 1.2 V, and productivity = 56.7 L m^–2 h^–1), the robust desalination performance (ASRR\n= 1.07 μmol cm^–2 min^–1)\nand energy consumption (ENRS = 7.8 μmol J^–1) of the FCDI system with a desalination unit number of four were\nverified at long-term operation. In summary, the stacked gradient\nFCDI system and its operation mode described here may be an innovative\nand promising strategy capable of enlarging the scale of desalination\nwhile realizing performance improvement and device simplification.