Reversible calcium-ion removal using redox-active intercalation materials for energy-efficient water hardness treatment
A novel electrochemical water treatment technology using redox-active ion intercalation materials (IMs), such as Prussian blue analogues, to remove hardness ions (calcium) more efficiently than conventional capacitive deionization. By storing ions volumetrically in the solid state rather than at electric double layers, the approach promises lower energy consumption, higher treatment rates, and reduced wastewater generation for water softening applications.
Overview
This technology addresses the inefficiencies of conventional capacitive deionization (CDI) for water hardness removal. Standard CDI relies on electric double layers (EDLs) at electrode interfaces, which limits charge storage capacity and requires thick, high-impedance porous electrodes. The proposed approach instead uses redox-active ion intercalation materials (IMs), such as Prussian blue analogues (PBAs), which absorb calcium ions volumetrically into the solid electrode structure. This volumetric mechanism enables approximately ten-fold higher molar charge storage compared to interfacial EDL storage, potentially delivering significant reductions in energy consumption, faster water treatment rates, and lower wastewater volumes during hardness removal cycles.
Technical specifications
Key features:
- Volumetric ion storage: Reversible calcium-ion absorption driven by electron transfer in redox-active IMs, achieving roughly ten-fold higher molar charge storage than conventional EDL-based CDI.
- Thin-film electrode format: IMs can be fabricated in films less than 10 micrometers thick with low impedance, replacing the thick porous electrodes (greater than 100 micrometers) required for EDL-based systems.
- Prussian blue analogue chemistry: Novel PBA formulations have been demonstrated to cycle stably in relevant electrolytes, including sodium chloride solutions representative of feedwater conditions.
- Deionization cell design: A cell architecture optimized to maximize water treatment rate, incorporating thin-film electrodes to reduce cell impedance.
- Validated baseline performance: Prior work has modeled and demonstrated deionization cell cycling using 0.1 molar NaCl feedwater, producing ten-fold increased productivity relative to previous demonstrations.
Technology readiness level
The technology is at an early-to-mid stage of development. Reversible calcium intercalation into PBA materials has been characterized, and a novel PBA formulation with stable cycling in relevant electrolytes has been developed. Initial deionization cell cycling has been demonstrated with sodium chloride feedwater at improved productivity levels. Future validation efforts will focus on fabricating and benchmarking a hardness-removal electrochemical process using PBA IMs in porous electrodes, then reducing cell impedance through a novel thin-film fabrication process, and ultimately integrating thin-film electrodes into a deionization cell designed for high water treatment rates. Funding is currently sought for equipment and personnel to advance the technology.
About University of Illinois, Urbana-Champaign
The University of Illinois Urbana‑Champaign is a flagship public research university with large‑scale research capacity and a broad academic portfolio. An on‑campus Research Park co‑locates corporate R&D teams and startups with faculty, while the National Center for Supercomputing Applications provides advanced computing and data capabilities for collaboration. Integration with a regional health system and an engineering‑based college of medicine enables clinical translation, and a long‑standing extension network links campus innovation to partners statewide. Research is supported by competitive federal funding from NSF, NIH, DOE, USDA, and DoD. A technology transfer office streamlines IP, licensing, and startups, complemented by incubators and prototyping in the Research Park.
delivered to your inbox.