Solidification of Phosphorus and Fluorine in Phosphogypsum and Its Effect on Properties of Mine Filling Materials

doi:10.16552/j.cnki.issn1001-1625.2025.0433

Abstract

Abstract: This study focused on the solidification of soluble phosphorus and fluorine impurities in phosphogypsum and its effect on the properties of filling materials. The effects of Ca(OH)₂ content, coal gasification slag (CGCS) content and particle size, free water content, and placement time on the solidification efficiency of soluble phosphorus and fluorine in phosphogypsum were investigated, with the solidification mechanism elucidated through SEM-EDS analysis. Subsequently, both untreated and solidified phosphogypsum were utilized as the primary raw material, supplemented with ordinary Portland cement (OPC) and fly ash (FA), to prepare phosphogypsum-based mine filling materials. The results show that CGCS reduces the total fluorine concentration in the toxic leachate of phosphogypsum and synergistically enhances the solidification of soluble fluorine by Ca(OH)₂. The compressive strength of filling materials prepared from solidified phosphogypsum is significantly increased from 0.25 MPa to 2.54 MPa, while the softening coefficient rises from 0 to 0.85 after 28 d of natural curing. XRD and SEM-EDS analyses further confirm that effective solidification of phosphorus and fluorine significantly promotes the hydration reactions of OPC and FA. Solidification of soluble phosphorus and fluorine impurities in phosphogypsum is a key approach to significantly enhance the mechanical properties and water resistance of filling materials.

Key words: phosphogypsum, filling material, solidification of phosphorus and fluorine, lime neutralization, toxicity leaching

CLC Number:

TQ177.3⁺9

CHEN Yanlong, ZHOU Yingying, FANG Keneng, CHEN Yiheng, CHEN Qianlin. Solidification of Phosphorus and Fluorine in Phosphogypsum and Its Effect on Properties of Mine Filling Materials[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2025, 44(10): 3791-3804.

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