Application and Mechanism of Waste Engine Oil in Phosphogypsum Flotation for Impurity Removal

Impurity removal and whiteness improvement are crucial for the high−value utilization of phosphogypsum. This study investigated the effects of waste engine oil, kerosene, and dodecylamine on the flotation purification of phosphogypsum sourced from a phosphate chemical plant in Hubei Province. Waste engine oil exhibited slightly superior flotation performance compared to kerosene, aligning with the green resource utilization concept of "waste−treating−waste". The mechanism of waste engine oil was elucidated through characterization techniques including X−ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X−ray photoelectron spectroscopy (XPS). The results demonstrated that under optimized conditions—pulp pH of 2, waste engine oil dosage of 100 g/t and MIBC dosage of 300 g/t in the reverse flotation stage, and sodium silicate dosage of 1000 g/t, dodecylamine dosage of 150 g/t, and MIBC dosage of 300 g/t in the direct flotation stage—the whiteness of phosphogypsum increased from 19.00% to 49.23%, with a yield of 75.46% and a calcium sulfate dihydrate grade of 93.55%. This research provides technical support for the high−value utilization of phosphogypsum through the "waste−treating−waste" approach.