Steady growth in human population and rapid industrial development have led to greater demands for water production and global water demand is expected to increase by 70% from 2016 to 2050. At the same time, anthropogenic activities (e.g., water softeners, road salt), agricultural practices, and the disposal of wastewater treatment plant effluent have led to salinization of natural freshwater resources. Desalination is one of the most viable options to address issues of freshwater scarcity and rising freshwater salinity. Recently, we have developed an electrochemical desalination technology 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^-. Our desalination battery is composed of a Bi electrode that serves as the Cl-storage electrode and a nickel hexacyanoferrate electrode that serves as the Na-storage electrode. Unlike reverse osmosis and electrodialysis that non-selectively remove all ions present in the feedwater, our desalination battery selectively removes Na⁺ and Cl^-. Therefore, when only Na⁺ or Cl^- need to be removed, our device can offer the most cost-effective solution. For example, Na⁺ and Cl^- specifically cause toxicity in many crops and the removal of only Na⁺and Cl^- from a water source would make it usable for irrigation. Additionally, many Midwest industrial and municipal wastewater treatment facilities have concerns about elevated Cl^- concentrations in wastewater as Cl^- is toxic to freshwater aquatic species. For these applications, the use of RO and ED that unnecessarily remove all other ions to lower the Na⁺ and Cl^- concentrations and consume a corresponding amount of additional energy is cost-prohibitive. Also, unlike RO or ED brine reject that contains a concentrated mixture of all ions present in the feedwater and cannot be easily valorized, brine produced from our desalination battery contains only Na⁺ and Cl^-, providing a unique opportunity for facile resource recovery. In this presentation, we will discuss the operating principles and applications of our Bi-based desalination battery in detail.

Do-Hwan Nam

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