Accelerated carbon mineralisation recently emerged as a promising approach for long-term carbon sequestration. This process involves reacting naturally abundant minerals (e.g. basalt, rich in Ca²⁺ and Mg²⁺) with aqueous CO₂ solution to form stable carbonate minerals.^[1] However, its molecular mechanism remains largely unknown due to the lack of direct experimental data probing structures and forces near the solid-liquid interface.^[2] Nonclassical 2-step crystallisation is now widely recognised as pathways of carbonate mineral formation.^[3-5] A common feature to such nonclassical mechanism is the formation of ionic clusters prior to crystallisation. The formation of these hydrated clusters and the drainage of solvents are closely related to the ordering of the water near the solid-solution interface. Our work uses surface force balance to measure the force between mineral surfaces across electrolyte solutions with micro-Newton and Angstrom precision. We observed unexpected long-range repulsive forces that cannot be explained by the Derjaguin-Landau-Verwey-Overbeek theory, and it is insensitive to ionic strength (beyond a threshold concentration) and pH. Our work provides key experimental results and insights to understand the specific ion effects at the solid-liquid interface, which is critical to the design and engineering of solution processes and colloidal systems such as carbon mineralisation.

References:
[1]    JM Matter et al., Science 352, 1312 (2016).
[2]    JJ De Yoreo, et al., Science 349, aaa6760 (2015).
[3]    PJM Smeets et al., PNAS, 114 (38) E7882 (2017).
[4]    H Jiang et al., J. Chem. Phys. 150, 124502 (2019).
[5]    B Jin et al. Nat. Mater. 24, 125 (2025).