Activation of Persulfate for Degrading Tetracycline Using the Leaching Residues of the Lead-Zinc Flotation Tailing

Inappropriate disposal of leaching residues from the lead-zinc tailings recovery process may result in environmental pollution. Its recycling and reuse remain a prevalent topic in environmental science and technology. It was roasted to prepare leaching residues-based materials (TLRS) in this work, and the TLRS were creatively used as the catalyst to active sodium persulfate (PS) to degrade organic pollutants. Degradation of tetracycline using the TLRS–PS system was evaluated, and the treating parameters were optimized. Roasting resulted in the exposure of active sites on TLRS surface, in which transition metals can donate electrons to PS to form SO₄^·−. SO₄^·− can further react with OH⁻ to form ·OH. Formation of these radicals was confirmed by both quenching experiments and EPR analysis. Under optimized conditions, 85% of the TC can be degraded in 3.0 h, and ~50% of degraded TC was mineralized to CO₂ and H₂O. The performance of TLRS barely changed after four reuses, suggesting the chemical stability of TLRS. The presence of dissolved substance in the water matrix could weaken the performance of the TLRS–PS system. A mechanism of TC degradation was proposed based on the experimental results and literature. These preliminary results provide us new insight on the reuse of lead-zinc flotation tailings.