Polymorphs and morphological changes during dissolution in aging of CaCO₃

In this study, an experimental setup was designed to achieve accelerated aging of CaCO₃ crystals in the laboratory to simulate the aging of calcite precipitates and biominerals caused by ocean acidification. CaCO₃ was formed in the calcium aqueous solution through the inflow of CO₂ from the atmosphere, and CaCO₃ aging was conducted in the absence and presence of polyacrylic acid (PAA). When PAA increased, the maximum amount of deposited CaCO₃ reduced, and the time to reach the maximum CaCO₃ deposition was longer. However, there was a late onset of dissolution during aging. In the absence of PAA, typical rhombohedra eroded in the form of a plate or irregular sheet, but in the presence of PAA, some calcite nanofibers broke into nanoparticles. During aging, the calcite polymorph was not changed, but the relative intensity of the (104) plane to other peaks became weaker. This observation implied that the crack in the calcite crystals propagated mainly in the (104) plane during aging. This experimental setup demonstrated that CaCO₃ aging caused by ocean acidification can be simulated in the laboratory.

Lee H. C. & Lee S., 2020. Polymorphs and morphological changes during dissolution in aging of CaCO₃. Journal of Advanced Marine Engineering and Technology 44 (4): 351-356. Article (subscription required).

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