Preparation of Gypsum–Urea with Enhanced Sustainability from Flue Gas Desulfurization Gypsum in Saturated Urea Solution

Caiyun Jia (), Jiang Zhao, Xiaoxia Fang, Pujun Wang, Anni Xiao and Haijun Zhang ()
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Caiyun Jia: School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Jiang Zhao: School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Xiaoxia Fang: School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Pujun Wang: School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Anni Xiao: School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Haijun Zhang: School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China

Sustainability, 2024, vol. 16, issue 14, 1-13

Abstract: Gypsum–urea is a kind of urea product with substantially reduced aqueous solubility and lower hygroscopicity that increases the soil retention time of urea and thus enhance its environmental sustainability. Here, gypsum–urea was prepared using bulk industrial solid waste flue gas desulfurization (FGD) gypsum as a raw material in a saturated urea solution via immobilizing urea molecules into the crystal lattice. The preparation process was achieved through a dissolution–recrystallization mechanism during which FGD gypsum dissolved into Ca 2+ and SO 4 2− , which then recrystallized with CO(NH 2 ) 2 to form gypsum–urea. The preparation process was almost completed within 10 min, and the formed gypsum–urea presented a uniform size distribution of 30–90 μm and a much lower hygroscopicity and nitrogen release efficiency than that of urea. With a high efficiency of synthesis, and sustainable features, and the recyclability of the saturated mother urea solution, the dissolution–recrystallization-based urea immobilization approach is highly promising regarding the preparation of gypsum–urea with the desired environmental sustainability and contributes to the realization of the sustainable reutilization of FGD gypsum.

Keywords: urea; FGD gypsum; gypsum–urea; hygroscopicity; sustainability (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2024
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