State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China.
Key Laboratory of Songliao Aquatic Environment, Ministry of Education, School of Municipal and Environmental Engineering, Jilin Jianzhu University, Changchun, 130118, China.
Water Res. 2020 Apr 1;172:115504. doi: 10.1016/j.watres.2020.115504. Epub 2020 Jan 15.
Activation of persulfates (i.e., peroxydisulfate (PDS) and peroxymonosulfate (PMS)) by nanoscale zero-valent iron (nZVI) is reported to be effective in oxidative treatment of environmental contaminants. It has been widely accepted in numerous literature that sulfate radical (SO) formed from the decomposition of persulfates activated by aqueous Fe(II) released from nZVI corrosion is responsible for the oxidative performance in nZVI/persulfates systems. In this work, by employing methyl phenyl sulfoxide (PMSO) as a probe, we demonstrated that the activation of persulfates by nZVI through electron transfer led to SO formation, while the homogeneous activation of persulfate by the released Fe(II) resulted in ferryl ion species (Fe(IV)) generation in nZVI/persulfates systems. Similarly, nanoscale zero-valent aluminum (nZVAl) and zinc (nZVZn) were also demonstrated to be able to donate electron to persulfates leading to SO formation. However, the insulative aluminum oxide shell hindered the electron transfer leading to the poor persulfates decomposition, while the conductive iron and zinc oxide shell enabled the electron transfer process resulting in a continuous generation of SO. Further, it was obtained that the relative contribution of SO and Fe(IV) in nZVI/persulfates systems was independent of the initial concentration of nZVI and PDS, but was positively correlated with PMS concentration. In addition, the increase of pH from 3 to 7 led to the decrease of the relative contribution of Fe(IV), which was rationalized by the decrease of availability of aqueous Fe(II) at higher pH. Our findings not only shed lights on the nature of the reactive intermediate formed in the nZVI/persulfates systems, but also unprecedentedly distinguished the surface activation of persulfates from the homogeneous catalysis process.
纳米零价铁（nZVI）激活过硫酸盐（例如过二硫酸盐（PDS）和过一硫酸盐（PMS））已被报道在环境污染物的氧化处理中非常有效。在大量文献中，广泛接受的观点是，由 nZVI 腐蚀释放的水相 Fe(II) 激活过硫酸盐分解产生的硫酸根自由基（SO）是 nZVI/过硫酸盐体系中氧化性能的主要原因。在这项工作中，我们通过采用甲基苯基亚砜（PMSO）作为探针，证明了 nZVI 通过电子转移激活过硫酸盐导致 SO 的形成，而释放的 Fe(II) 均相激活过硫酸盐则导致 nZVI/过硫酸盐体系中生成高铁离子（Fe(IV)）物种。类似地，我们还证明纳米零价铝（nZVAl）和锌（nZVZn）也能够向过硫酸盐供电子，导致 SO 的形成。然而，绝缘的氧化铝壳阻碍了电子转移，导致过硫酸盐的分解较差，而导电的铁和氧化锌壳则使电子转移过程得以进行，从而持续生成 SO。此外，我们发现 nZVI/过硫酸盐体系中 SO 和 Fe(IV)的相对贡献与 nZVI 和 PDS 的初始浓度无关，而是与 PMS 浓度呈正相关。此外，pH 值从 3 增加到 7 导致 Fe(IV)的相对贡献降低，这可以通过较高 pH 值下水相 Fe(II)的可用性降低来解释。我们的研究结果不仅阐明了 nZVI/过硫酸盐体系中形成的反应中间体的性质，而且前所未有地区分了过硫酸盐的表面激活和均相催化过程。
