Innovative synthesis of high-strength α-hemihydrate gypsum: Effects and mechanisms of TA modification under microwave hydrothermal conditions

Titanium gypsum (TG), a byproduct of the titanium dioxide industry, is recognized as a significant contributor to environmental pollution due to high water content, poor crystallinity and other characteristics that make it difficult to be reused/recycled effectively. This study evaluated the feasibility to recycle TG to produce α-hemihydrate gypsum via microwave hydrothermal method, wherein tricarballylic acid (TA) was employed as modifier to modulate the crystallization of α-HH. The impact of TA dosage on the characteristics of α-HH crystals is comprehensively assessed through a series of microscale analyses. The findings reveal a notable reduction in the Length/Diameter ratio (L/D ratio) of α-HH crystals, diminishing from 17.79 to 0.96, in response to the incremental introduction of TA, ranging from 0 % to 0.13 %. An optimum TA dosage of 0.1 % is found to yield a commendable compressive strength of 37.4 MPa. Additionally, this study validates the interaction between TA and α-HH crystals. Based on the experimental results, it is further postulated that microwave heating is conducive to expediting the rate of Ca2+ and SO42− ion accumulation at the (002) surface, thus altering the degree of solution supersaturation and consequently accelerating the growth kinetics of α-HH crystals. This study offers valuable insights into the utilisation of this methodology in various industrial and scientific applications.