Accelerated vanadium (IV)/(V) redox cycle and hydroxyl radical generation by hydroxylamine in peroxymonosulfate activation: from synthetic vanadium oxides to natural minerals

Vanadium-based catalysts face challenges in advanced oxidation processes (AOPs) due to the instability of expensive V(IV) and the weak catalytic activity of V(V). This study, leveraging the strong reducing ability of hydroxylamine (HA), developed the HA/V 2 O 5 /peroxymonosulfate (PMS) system. Under the condition of 100 μM PMS and 0.2 g/L V 2 O 5 , the addition of 200 μM HA accelerated the vanadium (IV)/(V) redox cycle, thereby increasing the degradation efficiency of sulfamethoxazole (SMX) from 18.3 % to 98.3 %. HO • was identified as the dominant reactive oxygen species (ROS) by quenching and probe experiments in the system, which was capable of non-selectively and efficiently degrading a wide range of micro-pollutants. Additionally, the degradation pathways and intermediate products of SMX and HA were investigated. HA was primarily converted into environmental friendly N 2 and NO 3 − , and significant reductions in the bioaccumulation factor, developmental toxicity, and mutagenicity of most SMX intermediate products were achieved. Finally, a comparative study evaluated the activation efficiency of natural vanadium‑titanium magnetite (VTM) and synthetic vanadium oxides in practical application scenarios, highlighting the high efficiency, stability and low cost of VTM compared to other reported catalysts.