Study on high-efficiency vanadium removement using sulfate radical-based AOPs and its oxidation mechanism of landfilled metallurgical residues

Silicate-encapsulated vanadium is the predominant form of vanadium found in landfilled metallurgical residues (LMR), which are by-products of vanadium production. This poses obstacles to the recovery and recycling of vanadium. In this study, Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) was proposed as an effective alternative for treating LMR. Based on the Ultrasonic wave + O₂ leaching method (UOL) as a blank experiment, the advantages of the Ultrasonic wave + persulfate leaching method (UPL) as a new oxygen supply method were investigated. Under the optimal conditions, the vanadium leaching rate increased by 33.56 % after 15 min of UPL treatment. Through quenching experiments, it was found that the contribution of oxidative free radicals in the UPL reaction process was ranked as follows: SO₄^•−>^•OH >¹O₂. Compared to UOL, UPL generated a large amount of SO₄^•− through ultrasonic and thermal activation, which facilitated the oxidative dissociation of silicate structures. Moreover, the reactive oxygen was involved in the reaction in molecular form during the reaction process to protect the original stabilized system. The leaching kinetics were investigated using the shrinking nucleus model. It was found that UPL and UOL were diffusion-controlled and mixing-controlled, respectively, and the activation energy of the UPL reaction was 16.24 kJ/mol, which was 46.77 % lower than that of the UOL reaction. The application of LMR not only mitigated the environmental impact associated with waste accumulation, but also enriched the slag phase with high-purity Fe, Mn, and Cr, thereby facilitating their subsequent recycling.