In view of the resource utilization of phosphogypsum,flotation method was used to remove the black organic matter.The effects of flotation agents on the whiteness of phosphogypsum,and on the water demand,coagulation time and mechanical properties of natural high-strength gypsum were explored.The results showed that different types of flotation agents had a great influence on the flotation whiteness of phosphogypsum.After flotation by flotation agent A(Oxane compounds),the samples had the lowest whiteness,which was 34.27％.After flotation by flotation agent D(MIBC),the samples had the highest whiteness,which was 42.9％.The flotation agent had little effect on the standard water requirement and coagulation time of natural high-strength gypsum,but it reduced the mechanical properties of natural high-strength gypsum,among which flotation agent A had the least effect on it.At the same time,the autoclaved hydrothermal method was used to prepare high-strength gypsum,which was prepared by phosphogypsum after impurity removal by flotation agent A,phosphogypsum after washing impurities and untreated phosphogypsum,and the 1 d absolute dry compressive strengths of the three groups high-strength gypsum were compared.The results showed that the compressive strengths of flotation pretreated high-strength phosphogypsum and water-washing pretreated high-strength phosphogypsum were 37.0 MPa and 30.7 MPa,increased by 222％ and 167％ respectively compared with untreated high-strength phosphogypsum,which meant the flotation pretreatment was more conducive to improving the compressive strength of high-strength gypsum.
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