Gurgul, S;
Williams, G;
Seng, G;
(2021)
Particle Engineering of Gypsum Through Templating with Starch.
Industrial and Engineering Chemistry Research
, 60
(16)
pp. 5852-5860.
10.1021/acs.iecr.1c00032.
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Abstract
The conversion of CaSO_{4}·0.5H_{2}O to CaSO_{4}·2H_{2}O (gypsum) is of great importance industrially, being the reaction behind plasterboard production and the setting of medical plasters. This hydration process is inherently slow, and to ensure that it occurs on a practical timescale, “seeds” of gypsum are typically added to accelerate the reaction. The seeds used in industry are mostly produced by milling quarried gypsum, resulting in huge variations in their accelerant properties between batches. Here, we develop a bottom-up process to prepare gypsum seeds with a tightly defined morphology, using starch as a templating agent during precipitation from water/ethanol mixtures. When the seeds thereby generated are dried, they tend to aggregate, which results in diminished accelerant properties. The hydration (or setting) time can be markedly reduced if these aggregates are broken up and suspended in a liquid medium. This indicates that directly adding the suspension reaction product to an industrial production line could be a powerful way to accelerate the setting reaction. However, the use of ethanol in the seed synthesis precludes this (because the ethanol would halt the setting reaction). Therefore, a direct one-step process involving evaporation of ethanol was developed to produce gypsum seeds in a water suspension with no ethanol present. The resultant “liquid seeds” are highly potent in accelerating the hydration process of CaSO_{4}·0.5H_{2}O to CaSO_{4}·2H_{2}O, resulting in shorter setting times than a commercial standard gypsum accelerant.
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