磷石膏浮选-常压盐溶液转晶制备α-半水石膏

Preparation ofα-hemihydrate gypsum from phosphogypsum by flotation and atmospheric trans⁃crystallization in solution

为了实现磷石膏的高值化利用,以湖北某地磷石膏为原料,采用泡沫浮选-常压Na2SO4溶液转晶法制备α-半水石膏。结合SEM-EDS、XRF、XRD、FT-IR、TG-DSC、白度测试与力学强度分析等手段表征产物形貌、组成与力学性能。结果表明:产物尺寸均匀、长径比为1.50±0.271;产物建材白度为84.6%,纯度高于95%;原料中大部分Si、F和P类杂质得以脱除,达到磷石膏用于石膏建材原料GB/T 23456—2018《磷石膏》中的I级磷石膏要求;转晶产物烘干抗压强度、2 h抗折强度分别高于36.3、7.7 MPa,满足相关国家标准与行业标准对高强石膏力学强度等级的要求。实验证明该工艺可以制备出高白度、高纯度和高强度的α-半水石膏,实现了磷石膏的无害化与资源化。

In order to realize the high value utilization of phosphogypsum,froth flotation-atmospheric Na2SO4 solution crys-tallization method was used to convert phosphogypsum sampled from Hubei province intoα-hemihydrate gypsum.The mor-phology,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 na-tional and industrial standards for the mechanical strength grade of high strength gypsum.The research was illustrated thatα-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.