Ultrasonic Irradiation during the Calcium Sulfate Hemihydrate to Dihydrate Transformation Process

Abstract

The ultrasound-assisted transformation of calcium sulfate hemihydrate (CSH) to calcium sulfate dihydrate (CSD) was studied using three ultrasonic power settings. In addition to continuously measuring the variation in the conductivity value with time, the process was followed by X-ray diffraction and scanning electron microscopy (SEM) analysis. Thermogravimetric analysis, Fourier transform infrared, mass spectrometry, and filtration analyses helped to determine the physicochemical properties of the as-obtained crystals. The morphological changes in the surface morphology were observed by SEM. The experimental results indicate that ultrasonic irradiation and its intensity have a significant effect on the crystal size, morphology, adsorption, and filtration characteristics. Mandelic acid in combination with ultrasonic irradiation can be used as an accelerator for the transformation process from CSH to CSD.

Controlled degradation of chitosan-coated strontium-doped calcium sulfate hemihydrate composite cement promotes bone defect repair in osteoporosis rats

“…Figure 5 shows the thermogravimetric curves of SrCSH and CS-SrCSH. The weight loss of SrCSH is obvious between 100 and 200 • C, which is mainly due to the evaporation of 0.5 mol crystalline water contained in SrCSH at temperatures higher than 100 • C. The weight loss of SrCSH did not decrease once the temperature increased above 300 • C. The final weight loss rate of SrCSH was 90.36%, which is basically consistent with the theoretical value [32]. The CS-SrCSH microspheres exhibit obvious weight loss between 100 • C-200 • C and 300 • C-500 • C, which is mainly due to the gradual carbonization and decomposition of CS film encapsulated on the surface of the microspheres [33,34].…”

Improvement of Plasterboard Properties by the Control of Polymethylhydrosiloxane Dosage, Stirring Time, and Drying Temperature Applied to the Calcium Sulfate Hemihydrate and Water Mixture

“…This is known as a hydration reaction. Some researchers, such as Singh and Middendorf [ 1 ] and Cheng et al [ 3 ], agree that HH hydration leading to DH formation occurs through a dissolution mechanism, i.e., HH particles dissolve in water and then DH precipitates from the aqueous solution by being less soluble than HH [ 4 , 5 , 6 , 7 ]. Using smaller HH particles ensures rapid dissolution before setting begins, which prevents the formation of mesopores [ 8 ].…”

Revealing Mechanism of Hemihydrate–Dihydrate Phosphogypsum Transformation and Minimizing Phosphorus Loss in Wet Process Phosphoric Acid

“…Kondratieva et al 20 found that the adding of SiC accelerates the hydration process of hemihydrate gypsum and increases the length of crystals. Polat and Sayan 21 found that the ultrasound irradiation can shorten the CaSO 7 studied the influence of process parameters on hydration kinetics of hemihydrate phosphogypsum in the simulation of wet process phosphoric acid recrystallization process. Yang et al 22 showed that the exposures of the crystal cylinders of α-HH are positive to hydration reactivity, whereas the exposures of the conical surfaces are negative to hydration reactivity.…”

“…Kondratieva et al found that the adding of SiC accelerates the hydration process of hemihydrate gypsum and increases the length of crystals. Polat and Sayan found that the ultrasound irradiation can shorten the CaSO 4 ·0.5H 2 O–CaSO 4 ·2H 2 O transformation time and generate more deformed and smaller-sized CaSO 4 ·2H 2 O crystals. Wang et al studied the influence of process parameters on hydration kinetics of hemihydrate phosphogypsum in the simulation of wet process phosphoric acid recrystallization process.…”