Synergistic depassivation of ZVI intensifies persulfate activation for high-efficiency vanadium leaching in a...

Vanadium-bearing metallurgical residue, a typical hazardous solid waste, poses significant challenges for resource recovery because vanadium is predominantly locked within dense, multilayered encapsulations composed of iron spinel, fayalite, and silicate phases. Herein, a novel ultrasound-assisted, zero-valent-iron-activated ammonium persulfate advanced oxidation process referred to as US/ZVI-AOPs was developed to enable highly efficient oxidative leaching of vanadium from V-MR through an effective synergy that integrates sonochemistry, heterogeneous catalysis, and interfacial electron transfer. The vanadium leaching efficiency of the US/ZVI-AOPs system reached 91.57%, while that of the conventional ZVI-AOPs process was 81.63% and that of the externally aerated oxygen system was less than 52%. Ultrasonic cavitation continuously stripped the Fe₃O₄/Fe₂O₃ passivation layer from ZVI, sustaining ferrous iron release and persulfate activation. The resulting synergistic oxidation by multiple reactive oxygen species proceeded with SO₄^•-, •OH, and ¹O₂ contributing 30.6%, 22.1%, and 11.9%, respectively. The leaching process followed a shrinking-core model, and its apparent activation energy decreased to 5.05 kJ mol^-1, which is 72.4% lower than the conventional value of 18.26 kJ mol^-1, indicating significantly alleviated diffusion limitations. This work provides a green, high-value pathway for V-MR valorization and a mechanistic paradigm for intensifying heterogeneous AOPs in complex solid-waste treatment.