A new study has found a way to produce sand-like materials—not through traditional mining, but by growing them in seawater using electricity and CO2. The researchers explored how factors like applied voltage, current density, and CO2 flow rate influence the electrochemical precipitation of minerals from seawater.
Study: Electrodeposition of Carbon‐Trapping Minerals in Seawater for Variable Electrochemical Potentials and Carbon Dioxide Injections. Image Credit: wing-wing/Shutterstock.com
Background
Producing magnesium hydroxide (Mg(OH)2) and calcium carbonate (CaCO3) from seawater via electrochemical methods offers a sustainable alternative to conventional material sourcing. These minerals are vital to the construction industry, used in everything from cement and concrete to paints, plasters, and fillers.
Despite its promise, this electrochemical approach has historically been slow and energy-intensive—barriers that have limited its industrial viability. However, growing interest in ocean-based carbon sequestration has revived attention toward electrodeposition techniques, particularly those that enable simultaneous mineral production and carbon capture. In this context, the formation of CaCO3 is especially valuable, as it directly traps CO2.
This study explores how introducing CO2 during electrochemical mineral synthesis in seawater can improve both efficiency and carbon sequestration. Through a detailed set of experiments, the researchers aimed to better understand the conditions under which Mg(OH)2 and CaCO3 can be reliably and efficiently precipitated.
Methods
The process centers on applying an electric current to seawater while injecting CO2 gas. Electrodes are placed in the water, and as electricity is applied, solid minerals begin to form. Meanwhile, CO2 is bubbled through the solution, contributing to the formation of CaCO3, which directly captures carbon and supports further reactions with Mg(OH)2 for additional sequestration.
Two main sets of experiments were conducted. In the first, CO2 was introduced at a fixed flow rate of 5 sccm for varying durations (0–100 minutes) prior to applying electrical energy. This allowed researchers to assess how different amounts of pre-injected CO2 (100–500 cm3) affected mineral precipitation once the current was applied.
In the second set, the same CO2 volumes were injected during the electrical stimulation phase, which was carried out under constant voltages over a 72-hour period. These tests evaluated how the timing of CO₂ injection—instead of just the amount—impacted the quality and yield of mineral deposits. Notably, the flow rates in these trials (0–0.45 sccm) were considerably lower than the reference case, which used a steady 5 sccm flow.
Results and Discussion
The experiments demonstrated that Mg(OH)2 and CaCO3 can be grown into sand-like mineral aggregates, with their properties largely shaped by controllable parameters such as applied voltage, current density, CO2 injection rate and timing, and seawater recirculation.
Depending on these variables, the resulting materials ranged from porous and flaky to dense and robust. Precipitation occurred either around the electrodes or freely within the solution. With proper tuning—particularly of the overpotential and CO2 flow—mineral aggregates several centimeters in size were successfully grown.
One notable finding was that maintaining a constant potential over longer periods led to decreasing current density due to mineral buildup near the cathode. This, in turn, promoted further growth while helping the deposit remain anchored to the electrode. However, this effect was less pronounced in longer-duration tests, likely due to sustained higher current densities.
Electrode geometry also played a role. Cylindrical and slender cathodes initially led to cylindrical mineral deposits, which gradually became more rounded due to electric field edge effects. This suggests that varying electrode shapes could be a practical way to control the final structure and morphology of the materials.
Conclusion
This study presents a practical method for growing carbon-sequestering minerals directly from seawater using electrical energy and CO2 injection. By fine-tuning process variables like voltage, gas flow rate, and recirculation timing, researchers were able to synthesize Mg(OH)2 and CaCO3 aggregates with customizable forms, textures, and carbon-trapping capabilities.
Immediate precipitation in the water minimized energy demand, while sustained mineral growth on cathode surfaces enabled the formation of larger, more structured aggregates. These materials hold strong potential as substitutes for sand and gravel in concrete—components that typically account for 60–70 % of this essential building material. Beyond that, they offer utility in producing cement, plaster, and paint—core elements of the built environment.
Journal Reference
Devi, N. et al. (2025). Electrodeposition of Carbon‐Trapping Minerals in Seawater for Variable Electrochemical Potentials and Carbon Dioxide Injections. Advanced Sustainable Systems, 9(3). DOI: 10.1002/adsu.202400943, https://advanced.onlinelibrary.wiley.com/doi/10.1002/adsu.202400943
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