Chemistry Department Seminar: Dr. Margaret Lumley, ChloBis Water
Development of Desalination Batteries for Energy-Efficient Seawater Desalination and Selective Chloride Removal
Steady growth in human population and rapid industrial development have led to greater demands for water production. At the same time, anthropogenic activities, agricultural practices, and the disposal of municipal and industrial wastewater have led to salinization of natural freshwater resources. A recent study estimated that 7,700 lakes in the Midwest and Northeast may be at risk for elevated Cl- concentrations, which is problematic because high Cl- concentrations are harmful to freshwater aquatic species. Municipal wastewater treatment and food processing plants are among the highest Cl- dischargers and so these facilities will be our first target customers. Although there are regulations in place to limit Cl- concentrations in wastewater effluent, they are difficult to enforce because there is no cost-effective technology available for Cl- removal. Reverse osmosis and electrodialysis are the primary options that can be used for Cl- removal, but they must remove all ions from the feedwater to decrease the Cl- concentration and are cost-prohibitive for applications that only require Cl- removal.
The technology that we have developed to overcome these limitations is called a desalination battery. Like conventional batteries, the desalination battery stores and releases energy during the charging and discharging processes but, in the desalination battery, these processes are coupled with the storage and release of Na+ and Cl-. As the energy consumed during charging is recovered during discharging, the net energy required for desalination is drastically reduced. The desalination battery requires both a Na-storage electrode and a Cl-storage electrode. Our state-of-the-art desalination battery is composed of a nickel hexacyanoferrate (NiHCF) electrode that serves as the Na-storage electrode and a Bi electrode that serves as the Cl-storage electrode. While various Na-storage electrodes are available due to the development of Na-ion batteries, Cl-storage electrode materials are rare. Thus, our patented discovery that Bi can serve as a practical Cl-storage electrode was critical to enable this technology. The desalination battery manages water, salts, and energy completely differently from conventional desalination methods to overcome their limitations and offer new water treatment strategies. Once commercialized, this technology has enormous potential to comprehensively address issues related to water treatment, environment protection, and resource recovery.