Parametric investigation of the desalination performance in multichannel membrane capacitive deionization (MC-MCDI)

Abstract

Recently, multichannel membrane capacitive deionization (MC-MCDI) has garnered significant attention due to its remarkable desalination performance over traditional CDI systems. However, for implementation in practical desalination applications, significant advances in the desalination performance of MC-MCDI are still needed, especially in enhancing the engineering design as well as understanding and optimizing the operating conditions. In this study, we propose an innovative approach to enhance the desalination performance of MC-MCDI by optimizing the operational conditions, such as the half-cycle time (HCT) for the charging step, operational cell voltage, salinity of the electrolyte, and feed flow rate. An optimized HCT (3 min) and the reverse-voltage mode (1.2 V and −1.2 V for charging and discharging) led to an increase in cumulative salt adsorption capacity (cSAC) of 49 mg/g, which was calculated based on the total amount of removed ions over 30 min of charging time. Furthermore, a significant cSAC of 160 mg/g was achieved with a highly saline electrolyte in the side channel (500 mM NaCl), while the change in the feed flow rate could maximize the ion removal rate of 0.035 mg/g/s. With these optimized operational conditions, MC-MCDI is highly stable over 100 cycles with an average charge efficiency of 96%. These results provide valuable insight into how desalination performance can be drastically enhanced through judicious engineering of the system, and selection of operational conditions. Finally, these results suggest that MC-MCDI has a high potential to become a remarkably effective cell design for industrial and environmental applications. Also, we emphasize the generality of our electrochemical configuration, which can be adapted also with novel electrode materials that can further enhance the overall system performance.