关键词: 磷石膏, α-半水石膏, 浮选, 盐溶液, 转晶剂

Abstract:

In order to realize the high value utilization of phosphogypsum，froth flotation-atmospheric Na₂SO₄ solution crystallization method was used to convert phosphogypsum sampled from Hubei province into α-hemihydrate gypsum.The morphology，composition and mechanical strength of the product were characterized through various characterization methods（like SEM-EDS，XRF，XRD，FT-IR，TG-DSC，whiteness test and mechanical strength test）.Experimental data revealed that the final product had uniform particle size with aspect ratio of 1.50±0.271.Whiteness and purity（based on CaSO₄） of the product was found to be around 84.6% and 95%，respectively.Most of the Si，F and P impurities was removed during the treatment，and final impurity level met the requirement of Grade I phosphogypsum in the National Standard GB/T 23456—2018 as the raw material of gypsum building materials.The compressive and 2 h flexural strength of hardened body of the crystallized product were higher than 36.3 MPa and 7.7 MPa，respectively，which met the requirements of the relevant national and industrial standards for the mechanical strength grade of high strength gypsum.The research was illustrated that α-hemihydrate gypsum with high whiteness，high purity，and high mechanical strength could synthesize by the process，and could be considered as a potential option for phosphogypsum.

Key words: phosphogypsum, α-hemihydrate gypsum, flotation, saline solution, crystal modifier