(338e) Analysis of an Integrated Photoelectrochemical Redox Flow Device for Brackish Water Desalination Using a Dye-Sensitized Photoanode

Electrochemical desalination is a promising approach to desalinating water for human, agricultural, and industrial use. Among the various electrochemical methods, including electrodialysis and capacitive deionization, redox flow desalination represents a high throughput, energy-efficient alternative.¹ We investigated a sunlight-driven process for solar redox flow desalination of brackish water. Instead of using a separate solar cell for electrical power generation and a redox flow electrochemical cell for desalination, the two devices were integrated into a single unit capable of light-powered salt removal from water.² The electrochemical cell consisted of redox electrolyte channels, one adjacent to each electrode, through which a redox electrolyte was recirculated at a constant flow rate. Each channel was bounded by the electrode (photoanode or cathode) on one side and by a cation exchange membrane (CEM) on the other. There were two other channels formed by an anion exchange membrane between the CEMs. The water to be desalinated was fed through these channels. The process effluents were the diluate (freshwater) and concentrate (brine) streams, generated by electrochemically driven ion transport through the ion exchange membranes. The desalination process was studied under the short-circuit current generated by illuminating a dye-sensitized titanium dioxide photoanode with AM1.5G light, as well as using various applied current densities. Feed streams with different sodium chloride concentrations and flow rates were used. Single-pass and closed-loop flow systems were investigated. This paper will compare the experimentally measured effluent stream concentrations and electrochemical cell voltages with those predicted by a mathematical model for the process.

References:

1. Mohandass G, Chen W, Krishnan S, Kim T. Asymmetric and Symmetric Redox Flow Batteries for Energy-Efficient, High-Recovery Water Desalination. Environmental Science & Technology. 2022;56(7):4477-4488. https://doi.org/10.1021/acs.est.1c08609

2. Mohandass G, Kim T, Krishnan S. Continuous Solar Desalination of Brackish Water via a Monolithically Integrated Redox Flow Device. ACS ES&T Engineering. 2021;1(12):1678-1687. https://doi.org/10.1021/acsestengg.1c00266