Mechanism of Polyethylene Glycol Assisted Crystallization of Magnesium Carbonate trihydrate research

To enhance the preparation of high-aspect-ratio magnesium carbonate trihydrate (MgCO₃·3H₂O) via polyethylene glycol (PEG)-assisted coprecipitation, MgCO₃·3H₂O was synthesized and characterized by XRD, SEM, TG-DSC, FTIR, and particle size analysis. The effect of PEG concentration on the aspect ratio was investigated, and in situ 2D imaging was employed to explore the growth mechanism over a 240 min reaction under the optimal PEG addition. The results indicated that the aspect ratio decreased with increasing PEG content. At 0.2 wt% PEG, rod-like crystals with an aspect ratio of 11.53 and an average length of 46.69 μm were obtained. In situ imaging revealed initial nucleation at approximately 15 min, enabling real-time monitoring of crystal evolution. Crystals up to 167.24 μm in length were formed, with a Mg2+ conversion rate of about 91%. The transformation between MgCO₃·3H₂O and Mg₅(CO₃)₄(OH)₂·5H₂O via dissolution–recrystallization was observed during prolonged reaction. This study provides a novel analytical approach for investigating MgCO₃·3H₂O and offers a practical reference for synthesizing high-aspect-ratio crystals using PEG.