Membrane-Current Collector-Based Flow-Electrode Capacitive Deionization System: A Novel Stack Configuration for Scale-Up Desalination

Abstract

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

Enhanced Desalination Performance by a Novel Archimedes Spiral Flow Channel for Flow-Electrode Capacitive Deionization

“…During the continuous desalination process, the ASRR gradually decreased from 4.06 to 0.54 μmol cm –2 min –1 as the current decline. This is because a decrease in the salt concentration of saline water would reduce the ASRR due to the higher ion resistance . Additionally, the Donnan potential is caused by the low permeability of the ion exchange membrane, which effects the portion of the applied voltage for driving the ion migration. − In the whole desalination process, the Donnan potential was changed from the same direction as the applied voltage to the opposite direction with the increase of NaCl concentration in the flow electrode.…”

Engineering bimetallic capture sites on hierarchically porous carbon electrode for efficient phosphate electrosorption: multiple active centers and excellent electrochemical properties

“…Electro-assisted adsorption has attracted increasing attention due to its distinct benets such as efficient performance, rapid reaction, and environmental friendliness, making it a promising technology for pollutants elimination. [8][9][10][11] In the electrosorption process, charged ions can be rapidly adsorbed and stored in the oppositely charged electrode when an external voltage is applied. 12 Compared to conventional adsorption, phosphate anions are able to migrate faster and reach deeper adsorptive sites with the assistance of the electric driving force.…”

Electron Transfer of Activated Carbon to Anode Excites and Regulates Desalination in Flow Electrode Capacitive Deionization

“…Electroadsorption has been widely studied because of its low energy consumption, − particularly flow electrode capacitive deionization (FCDI). − FCDI overcomes the problems of low adsorption capacity and noncontinuous operation of traditional capacitive deionization (CDI). ,, The working principle of FCDI is similar to that of CDI, and ion removal is mainly realized by the electric double layer formed by the flow electrodes. − Therefore, many researchers have focused on the development of high-performance flow electrodes, including capacitive materials (activated carbon, , carbon nanotubes, − carbon black, , and improved carbon-based materials − ) and redox materials (vanadium, hydroquinone, and BTMAP-Fc). Due to the low price and stable performance, powdered activated carbon (PAC) has become the main material for FCDI flow electrodes. − Therefore, further optimization of the desalination performance of PAC has become a major problem at the present stage. The premise is to understand the influence of the physicochemical properties of PAC on the desalination performance of FCDI, particularly to determine the key factors.…”