Magnetite is a ubiquitous iron mineral in nature and its iron ions are usually isomorphically substituted by Ti and V cations, which shows a high ability for degradation of organic contaminants via the photo-Fenton process. However, numerous reports pay more attention to the activity of synthetic magnetite rather than natural magnetite. Here, three types of natural magnetite (HG01, HG02, and GCL01) with different Ti and V contents were investigated from the perspective of the difference in structural property, catalytic activity, HO decomposition, and reactive oxygen species generation. Structural characterization exhibited that the purity of natural magnetite obeyed the order: GCL01 > HG02 > HG01. HG01 contained the highest Ti content in the form of ilmenite, followed by HG02 and GCL01. Moreover, HG01 yielded the highest photo-Fenton catalytic activity with 99.5 % of naphthol degradation and 96.0 % of HO decomposition after 60 min reaction. The superior activity of HG01 was attributed to the relatively high Ti and V content as demonstrated by redundancy analysis. Mechanistic investigation implied that the Ti and V in the octahedral sites of the magnetite surface can accelerate the electron transfer from Fe(III) to Fe(II), resulting in higher Fenton activity. Besides, ilmenite in HG01 enhanced naphthol degradation because HO accelerated the separation of photoelectron-holes pairs to promote O production. Furthermore, as revealed by gas chromatography-mass spectrometry and the toxicity of identified products predicted by the ECOSAR model, the toxicity of naphthol can effectively reduce accompanied by the harmless products generated. The high reusability, low iron ions residual in water, harmless end products, and easily recycled with magnetic separation suggest that natural magnetite has a promising application prospect for wastewater purification.

中文翻译：

---

深入了解天然磁铁矿对萘酚的异质光芬顿降解：冗余分析和毒性评估

磁铁矿是自然界中普遍存在的铁矿物，其铁离子通常被Ti和V阳离子同构取代，通过光芬顿过程表现出很强的有机污染物降解能力。然而，许多报道更关注合成磁铁矿的活性而不是天然磁铁矿。本文从结构性能、催化活性、H2O分解和活性氧生成的差异的角度研究了不同Ti和V含量的三种天然磁铁矿（HG01、HG02和GCL01）。结构表征表明，天然磁铁矿的纯度顺序为：GCL01>HG02>HG01。 HG01 以钛铁矿形式含有最高的 Ti 含量，其次是 HG02 和 GCL01。此外，HG01 产生了最高的光芬顿催化活性，反应 60 分钟后萘酚降解率为 99.5%，H2O 分解率为 96.0%。冗余分析表明，HG01 的优异活性归因于相对较高的 Ti 和 V 含量。机理研究表明，磁铁矿表面八面体位点的Ti和V可以加速电子从Fe(III)到Fe(II)的转移，从而产生更高的芬顿活性。此外，HG01中的钛铁矿增强了萘酚的降解，因为H2O加速了光电子-空穴对的分离，促进了O的产生。此外，气相色谱-质谱分析和ECOSAR模型预测的鉴定产物的毒性显示，萘酚的毒性可以有效降低，同时生成无害产物。天然磁铁矿具有高可重复使用性、水中铁离子残留量低、最终产品无害、易于磁选回收等优点，在废水净化方面具有广阔的应用前景。