Resource utilization of phosphate tailings by calcination and leaching with dilute H3PO4 solution

Phosphate tailing is a solid waste from the process of phosphate resource utilization. It is rich in phosphorus, calcium, and magnesium. Exploring a profitable comprehensive utilization route of phosphate tailings is crucial for the disposal of phosphate tailings. A utilization route of P, Ca and Mg in phosphate tailings was proposed in this work. Phosphate tailings were first calcinated and leached with dilute H₃PO₄. The Ca and Mg from dolomite in phosphate tailings were selectively dissolved into leaching liquor, followed by the precipitation of CaHPO₄ and MgNH₄PO₄ from the leaching liquor through pH adjustment. After leaching, the unreacted fluorapatite and silicates became a phosphate concentrate with a P₂O₅ content of 29.89 wt%. The phosphorus in the tailings was recovered in the form of concentrated phosphate ore with a recovery rate of 99.86 %. Decomposition kinetics of dolomite in the calcination process was studied. The activation energy is 195.82 kJ/mol and the pre-exponential factor is 1.73 × 10⁹ s⁻¹. The results provide an effective route of utilizing phosphate tailings.