(460a) Solar-Driven Electrochemical Desalination of Seawater

Providing access to clean water is a major global issue, which has been listed as one of the grand challenges of the 21^stcentury. To address this challenge, alongside efforts such as water conservation and recycling, several desalination techniques based on reverse osmosis and electrodialysis have been developed to meet the clean water demands. However, the present techniques either have a low salt rejection or high energy requirement for a desirable salt rejection. Here we propose a solar-powered electrochemical cell utilizing bipolar membranes to produce desalinated water from the seawater. A stack consisting of a bipolar membrane, an anion-exchange membrane, a cation-exchange membrane, and a bipolar membrane separated by seawater is used to electrodialyze seawater to create a desalted stream and two brine streams. The bipolar membranes simultaneously trap salt ions while producing counter-ions to neutralize the brine streams, and prevents salt ions from contacting the electrodes. To analyze the feasibility and robustness of the design, modeling and simulation of the solar-driven electrodialysis were performed using COMSOL Multiphysics. Preliminary results show that at least 99% of salt rejection can be attained from the initial brine concentration of 3.4 M to yield near-neutral pH water containing 0.015 M of salt. The effect of various parameters such as the resistance of seawater, conductivity, and permeability of membrane, flowrate, applied current density, and seawater concentration on the efficiency of desalination will be discussed. The successful implementation of this design could be used in water-stressed areas as well as research facilities on the ocean and in the remote locations. Solar-driven electrodialysis for desalination of water would make the technology portable and easily accessible.