introduction of nucleation and growth process of alkali promoted MgO during CO2 capture

https://doi.org/10.1039/D2TA02897B

“Kinetic analysis of CO₂ absorption on AMS promoted MgO using thermogravimetric analysis (TGA) has revealed that the formation of MgCO₃ is characterized by a nucleation and growth process.¹⁰ In such a process the nucleation and growth of magnesium carbonate would rely on the dissolution of MgO and CO₂ in the AMS leading to a supersaturated solution of a magnesium carbonate precursor (e.g. [Mg²⁺…CO₃²⁻]) yielding ultimately crystalline MgCO₃. A recent study into the growth process of MgCO₃ has shown that MgCO₃ grows in the form of 2D crystals with a sector plate morphology at the interface of NaNO₃/MgO, providing further evidence for a nucleation and growth process in which MgCO₃ precipitates as crystals from a supersaturated solution.¹⁵ While there is a general agreement on the nucleation and growth process for MgCO₃ formation,^14,16 the location at which MgCO₃ precipitates most favorably is still unclear. Conceptually, MgCO₃ can form within the molten salt, at the interface of the salt and MgO (NaNO₃/MgO), often referred to as the “buried interface” or at the triple phase boundary (TPB), i.e. the interface of NaNO₃/MgO that is exposed to the CO₂ atmosphere. Answering this question, will provide important sorbent design guidelines as to whether an effective sorbent shall have a high TPB length or a large NaNO₃/MgO interface area.”