摘要
以混合相磷石膏为主要原料,掺入矿渣、赤泥、偏高岭土、熟料制备混合相磷石膏基胶结材,通过抗压强度、pH和浸出毒性测试研究其早期性能,采用X射线衍射(XRD)、扫描电镜(SEM)和傅里叶变换红外光谱(FT-IR)测试分析水化机理.结果表明:53.76%(质量分数,下同)混合相磷石膏、9.68%矿渣、9.68%赤泥、16.13%偏高岭土和10.75%熟料可制备出性能最优的混合相磷石膏基胶结材,其3、5、7 d抗压强度分别达到8.93、10.99、13.14 MPa,pH碱性低于传统水泥基材料,总磷、氟化物浸出浓度均满足污水综合排放标准要求;磷石膏在400℃下煅烧60 min形成半水-无水混合相磷石膏,其中半水石膏和无水石膏的相对含量分别为31.7%和68.3%.混合相磷石膏基胶结材水化生成的水化硅酸钙凝胶、钙矾石和透钙磷石等物质形成致密结构,提升材料强度,阻隔污染物F-、PO43-浸出.混合相磷石膏基胶结材具有良好的力学性能和环境相容性,可为磷石膏规模化消纳提供新途径.
Abstract
Mixed phase phosphogypsum was used as the main raw material,and slag,red mud,metakaolin and clinker were added to prepare mixed phase phosphogypsum-based cementing material.Its early performance was studied by compressive strength,pH and leaching toxicity tests,and the hydration mechanism was elaborated by X-ray diffraction(XRD),scanning electron microscope(SEM)and Fourier transform infrared spectroscopy(FT-IR)tests.The results showed that 53.76%(mass fraction,the same below)of mixed phase phosphogypsum,9.68%of slag,9.68%of red mud,16.13%of metakaolin and 10.75%of clinker could prepare the mixed phase phosphogypsum cementing material with optimized performance,and its compressive strength at the 3,5 d and 7 d were 8.93,10.99 MPa and 13.14 MPa respectively.Its pH alkalinity was lower than that of traditional cement-based materials,and the leaching concentration of PO43-and F-were lower than the limit of the integrated wastewater discharge standard.The results of microscopic analysis showed that phosphogypsum was calcined at 400℃for 60 min to form hemihydrate-anhydrate mixed phase phosphogypsum,in which the relative contents of hemihy-drate and anhydrate gypsum were 31.7%and 68.3%respectively.The hydrated calcium silicate gel,ettringite and brushite generated by hydration of mixed phase phosphogypsum-based cementing materials formed dense structures,which would improve the strength of materials and block the leaching of pollutants.The mixed phase phosphogypsum-based cementing material had good mechanical properties and environmental compatibility,which provided a new potential way for the large-scale consumption of phosphogypsum.
基金项目
三峡库区生态环境教育部工程研究中心开放基金课题项目(KF2022-11)
宜昌市自然科学研究项目(A23-2-020)
NETL
NSTL
万方数据