(450l) Three-dimensional electrode for Electrodialysis unit

Surging population and climate change will push society, ever more urgently, to harvest lower quality or impaired water supplies (e.g., sea water or brackish groundwater) for drinking water. For example, desalination of sea water has become a promising technique for providing additional sources of fresh water along coastal communities. However, the widespread adoption of desalination technologies (Reverse Osmosis and electrodialysis) is currently limited due to its energy intensive nature and/or limited membrane lifetime and performance, especially during high operation rates. This work focuses on developing a novel, cost-effective, integrated sunlight driven electrodialysis (ED) unit. Specifically, we have replaced planar electrodes in traditional electrodialysis units with 3-D circulating photoelectrodes that generates the required electrochemical potential gradient upon illumination to drive ion transport across the membranes. The 3-D circulating photoelectrode bed configuration provided large surface area per unit volume, thereby allowing high currents to be drawn at current densities short of the diffusion-limited regime, a criteria needed to prevent unwanted secondary reactions such as water splitting. Effect of temperature (20, 30, and 40 ⁰C) and flow rate of sea water (0.1, 0.2, 0.4 ml/s) on salt-ion rejection was also investigated.