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Docta Complutense author Cuesta Mayorga, Iris author Astilleros García-Monge, José Manuel author Fernández Díaz, María Lourdes 2023-06-17T13:27:27Z 2023-06-17T13:27:27Z 2019-03-13 2075-163X 10.3390/min9030178 https://hdl.handle.net/20.500.14352/13531 https://www.mdpi.com/2075-163X/9/3/178 In this work, we aimed to experimentally study the nucleation and growth of CaCO3 phases precipitated from supersaturated aqueous solutions in the presence of varying concentrations of sulphate oxyanion. The experiments were conducted under pH conditions close to neutral (7.6) and by considering a wide range of initial (SO42−)/(CO32−) ratios (0 to approx. 68) in the aqueous solution. We paid special attention to the evolution of the precipitates during ageing within a time framework of 14 days. The mineralogy, morphology, and composition of the precipitates were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and EDX microanalysis. The concentration of sulphate ions in the reacted aqueous solution was studied by ICPs. The experimental results showed that the mineral composition of the precipitate recovered in each run varied with the (SO42−)/(CO32−) ratio in the parental solution, which influenced the mineral evolution of the precipitates during ageing. We observed that high concentrations of sulphate in the aqueous solution stabilized the vaterite precipitates and inhibited calcite formation. Furthermore, aragonite never precipitated directly from the solution, and it was only formed via a dissolution-precipitation process in solutions with a high (SO42−)/(CO32−) ratio after long reaction times. Finally, gypsum only precipitated after long ageing in those aqueous solutions with the highest concentration of sulphate. The reaction pathways during ageing, the morphology of the calcite crystals, and the composition of vaterite and calcite were discussed considering both kinetic and thermodynamic factors. These results showed a considerably more complex behavior of the system than that observed in experiments conducted under higher pHs and supersaturation levels and lower (SO42−)/(CO32−) ratios in the aqueous phase. eng Atribución 3.0 España Precipitation of CaCO3 Polymorphs from Aqueous Solutions: The Role of pH and Sulphate Groups journal article URL https://docta.ucm.es/bitstreams/b6804024-0ee7-4d72-8bbc-b6a6e9f16d3f/download File MD5 4790a660a34f31c885ce21e9e6aa62e7 3964464 application/pdf Precipitation of CaCO3 Polymorphs from Aqueous Solutions.pdf