Novel Synergistic Process of Impurities Extraction and Phophogypsum Crystallization Control in Wet-Process Phosphoric Acid

Phosphogypsum, as a byproduct of wet-process phosphoricacid reaction,has caused many environmental pollution problems. To improve the propertyand purity of phosphogypsum in the wet-process phosphoric acid process,a liquid-solid-liquid three-phase acid hydrolysis synergisticextraction reaction system was established by adding a certain amountof extractant in the actual production process. In order to studythe extraction effect and residue of impurities in the reaction system,the phase, morphology, and impurity occurrences of phosphogypsum weresystematically analyzed. The results showed that when the reactiontime was 7 h, the reaction temperature was 80 & DEG;C, the reactionspeed was 200 r/min, the volume ratio of the extractant to diluent(dilution ratio) was 1:4 and the volume ratio of the oil phase/aqueousphase (O/A ratio) was 1:1, P2O5 conversion wasthe highest in phosphate rock, and the residual P2O5 content in phosphogypsum was as low as 0.36%. The morphologyof the phosphogypsum crystal was uniform and coarse long strip. Themain forms of residual impurities were silicate, aluminum fluoridewith crystal water, aluminate, phosphate, and fluoride. Meanwhile,the residual amount of main impurities in phosphogypsum was significantlyreduced. Through this novel method, the property of phosphogypsumcan be improved through the generation process and is greatly beneficialfor its utilization and the recycling development of the wet-processphosphoric acid industry.