Revealing maleic acid role in the preparation of α-hemihydrate gypsum from titanium gypsum through experiments and DFT calculations.

Titanium gypsum (TG) is rarely used to produce α-hemihydrate gypsum (α-HH) because of its poor crystallinity and high impurity and moisture contents. Here, a method is proposed to prepare α - HH by adjusting the reaction temperature, CaCl solution concentration and maleic acid dosage based on acid leaching and heat-treated TG as raw material. The effect of maleic acid and Fe ions on the preparation of α-HH were systematically analyzed using density functional theory (DFT) and typical materials characterization methods, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS).