Two-Step Preparation of Quasi-Spherical α-Calcium Sulfate Hemihydrate from Flue Gas Desulphurization Gypsum

The quasi-spherical alpha-calcium sulfate hemihydrate (alpha-CSH) with the size of 6 similar to 10 mu m has been synthesized from flue gas desulphurization (FGD) gypsum by two-step hydrothermal method under the regulation of N,N'-methylenediacrylamide (MBA). The effect of MBA addition on the morphology and size of alpha-CSH product and the regulation mechanism was investigated by FTIR and EDS measurements as well as ethylene glycol concentration-dependent experiments. MBA could be preferentially absorbed on the (111) plane of alpha-CSH to inhibit the growth of alpha-CSH along c axis, and form a three-dimensional gel network to exert the confinement effect on the nucleation and growth of alpha-CSH particles. In addition, after undergoing physical washing and two-step chemical hydrothermal treatment, the whiteness of the synthesized alpha-CSH was improved from 39.22% to 92.06%.

Automated summary

In this study, quasi-spherical alpha-calcium sulfate hemihydrate (alpha-CSH) was synthesized from flue gas desulphurization gypsum using a two-step hydrothermal method, with N,N'-methylenediacrylamide (MBA) playing a crucial role in regulating the morphology and size of the product. The addition of MBA inhibited the growth of alpha-CSH along the c-axis and improved the whiteness of the synthesized alpha-CSH after undergoing physical washing and two-step chemical hydrothermal treatment.