High-Throughput Automated Platform for In-Situ Monitoring of CaSO₄ Formation

Capturing short-lived intermediate phases during crystallization is critical to understanding and improving the sustainability of mineral processing, but conventional ex situ methods often miss these transient species. We present a novel automated flow-through synthesis platform that enables simultaneous in-situ X-ray diffraction/scattering and Raman spectroscopy measurements to investigate crystallization processes in real time. This setup captures transient reaction intermediates and tracks crystallization mechanisms during wet-chemical reactions, providing direct insight into dissolution–reprecipitation pathways and amorphous phase transitions.

Using calcium sulfate (CaSO₄) as a model system, we demonstrate how the platform reveals complex crystallization dynamics: real-time monitoring of gypsum-to-bassanite conversion in a hypersaline solution captured intermediate nanoparticle formation and a clear dissolution–reprecipitation mechanism. By enabling such controlled synthesis and monitoring, the method supports sustainable mineral use and the potential recycling of calcium sulfate materials through optimized reaction pathways.

The modular design of our platform —incorporating a glass capillary flow cell and peristaltic pumps for continuous circulation—minimizes contamination and allows uninterrupted in-situ analysis, with all components programmed via a Python-based control system for improved reproducibility. This high level of automation also opens opportunities for self-optimization of syntheses via machine learning algorithms. While demonstrated on calcium sulfate, the versatile system is readily extendable to other material classes including polyoxometalates (POMs), metal–organic frameworks (MOFs), and covalent organic frameworks (COFs).