New nucleation to advance climate resilience and clean energy technologies

A new study led by researchers at Washington University in St. Louis investigates an innovative method for capturing carbon dioxide (CO₂) while recovering nickel (Ni), a critical metal for clean energy technologies. The study focuses on carbonation — converting CO₂ into solid carbonates — and sulfidation, which forms sulfide minerals, to recover nickel from sources, such as low-quality ores, mining waste and industrial sludge.

The study, led by Young-Shin Jun, professor of energy, environmental & chemical engineering in the McKelvey School of Engineering, was recently published April 25, 2025 in The Journal of Physical Chemistry C.

"By combining these processes, we can store CO₂ as solid carbonates while recovering nickel in a form that can be easily separated using existing infrastructure," Jun said.

The experimental conditions were designed to mimic real-world industrial processes, specifically ex-situ carbon mineralization where CO₂ is captured and stored in solid forms, while simultaneously unlocking its potential as a useful chemical feedstock.

"Our research group is well-equipped to conduct studies using high-pressure, high-temperature reactor systems to simulate subsurface or industrial process conditions," Jun explained.

The study revealed that solid nucleation during carbonation and sulfidation processes can be systematically controlled. During carbonation, hydromagnesite forms initially and converts to magnesite over time through dehydration. Similarly, nickel bicarbonate forms early and transitions into an anhydrous Mg/Ni solid solution carbonate as the reaction progresses. This behavior is attributed to the similar crystalline structures of magnesite (MgCO₃) and gaspéite (NiCO₃). In the case of sulfidation, the study found that amorphous nickel sulfide forms at both neutral and slightly basic pH levels, unaffected by magnesium ions due to its low solubility equilibrium constant. When two processes are combined, separate phases of magnesium carbonate and nickel sulfide formed simultaneously, simplifying the processing of both carbon mineralization and critical metal recovery.

Beyond its industrial applications, the study also found new insights into natural environmental processes, such as the formation of nickel and magnesium carbonates and their conversion to sulfides.

Jun and the team suggested this method has broad applications in critical element extraction and recovery from unconventional low-quality resources, enhancing resource efficiency and promoting sustainable development. Looking ahead, they plan to explore applying these methods to other critical metals.

"The principles we have established with nickel and magnesium can be extended to the recovery of other critical elements from diverse resources," Jun emphasized. "The key is precisely controlling the solid nucleation and interfacial processes. By building on these findings, we can help society move toward a more sustainable and climate-resilient future."

Wang Y, Alexakos C, Zaidman TJ, Houghton J, Xie Z, Fike DA, Jun Y. Carbonation and sulfidation of Mg- and Ni-containing solutions: Implications for carbon mineralization and critical element recovery. The Journal of Physical Chemistry C, online April 25, 2025. DOI: https://doi.org/10.1021/acs.jpcc.4c08473

This work was supported by the U.S. Department of Energy Office of Science (DE-SC0023390), the Stanford Synchrotron Radiation Lightsource and the Chemical and Environmental Analysis Facility and the Institute of Materials Science & Engineering at Washington University in St. Louis.

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