Recently, the wide application of CuO nanoparticles (NPs) in engineering field inevitably leads to its release into various geologic settings, which has aroused great concern about the geochemical behaviors of CuO NPs due to its high surface reactivity and impact on the fate of co-existing contaminants. However, the redox transformation of pollutants mediated by CuO NPs and the underlying mechanism still remain poorly understood. Here, we studied the interaction of CuO NPs with As(III), and explored the reaction pathways using batch experiments and multiple spectroscopic techniques. The results of in situ quick scanning X-ray absorption spectroscopy (Q-XAS) analysis verified that CuO NPs is capable of catalytically oxidize As(III) under dark conditions efficiently at a wide range of pHs. As(III) was firstly adsorbed on CuO NPs surface and then gradually oxidized to As(V) with dissolved O2 as the terminal electron acceptor. As(III) adsorption increased to the maximum at a pH close to PZC of CuO NPs (~ pH 9.2), and then sharply decreased with increasing pH, while the oxidation capacity monotonically increased with pH. X-ray photoelectron spectroscopy and electron paramagnetic resonance characterization of samples from batch experiments indicated that two pathways may be involved in As(III) catalytic oxidation: (1) direct electron transfer from As(III) to Cu(II), followed by concomitant re-oxidation of the produced Cu(I) by dissolved O2 back to Cu(II) on CuO NPs surface, and (2) As(III) oxidation by reactive oxygen species (ROS) produced from the above Cu(I) oxygenation process. These observations facilitate a better understanding of the surface catalytic property of CuO NPs and its interaction with As(III) and other elements with variable valence in geochemical environments.

中文翻译：

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在宽范围的pH值下，亚砷酸盐的催化氧化和CuO纳米颗粒表面的反应路径。

最近，CuO纳米颗粒（NPs）在工程领域的广泛应用不可避免地导致其释放到各种地质环境中，由于其高的表面反应性和对Co-fate的影响，引起了人们对CuO NPs的地球化学行为的极大关注。现有的污染物。但是，对由CuO NPs介导的污染物的氧化还原转化及其潜在机理仍然知之甚少。在这里，我们研究了CuO NPs与As（III）的相互作用，并使用批处理实验和多种光谱技术探索了反应途径。原位快速扫描X射线吸收光谱（Q-XAS）分析的结果证明，CuO NPs能够在较暗的条件下在宽范围的pH值下有效催化氧化As（III）。As（III）首先吸附在CuO NPs表面，然后以溶解的O2作为末端电子受体逐渐氧化为As（V）。当pH值接近CuO NPs的PZC（〜pH 9.2）时，As（III）的吸附增加到最大值，然后随pH值的增加而急剧下降，而氧化能力随pH值单调增加。批处理实验样品的X射线光电子能谱和电子顺磁共振表征表明，As（III）催化氧化可能涉及两个途径：（1）直接电子从As（III）转移到Cu（II），随后伴随通过溶解的O2将生成的Cu（I）重新氧化为CuO NPs表面上的Cu（II），以及（2）通过上述Cu（I）氧化过程产生的活性氧（ROS）氧化As（III） 。