Flotation Purification of Phosphogypsum and Preparation of β-hemihydrate Gypsum
The large-scale stockpiling of phosphogypsum poses a significant environmental challenge,mainly due to its high impurity content and low whiteness,which critically limit its potential for high-value applications.This study investigated phosphogypsum from a plant in Hubei Province,integrating process mineralogy with graded flotation for efficient purification.The results showed that the use of hydrochloric acid,water glass,collector ZX-4-4 and frother Q1 in a closed circuit flotation process-consisting of one rougher flotation,two cleaner flotations and a sequential middle return-significantly improved the quality of the material.Specifically,the CaSO4-2H2O content of the phosphogypsum was increased from 89.65%to 98.15%,while the whiteness improved from 37.10%to 52.44%.The overall recovery rate reached 83.47%with a significant reduction in impurities:silica content decreased from 6.16%to 0.58%and iron content was minimized to 0.006 2%.The whiteness of the β-hemihydrate gypsum produced by direct calcination of the purified phosphogypsum exceeded 80%,significantly exceeding the first grade specifications of the national standard GB/T 23 456-2018 for phosphogypsum.Thus,the flotation process significantly improved both the quality of the phosphogypsum and the performance of the derived products.
phosphogypsumprocess mineralogyflotationimpurity removal and whiteningβ-hemihydrate gypsum
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