第一作者：Muhammad Bilal Asif
通讯作者：Cafer T. Yavuz
通讯单位：沙特阿拉伯
DOI:10.1016/j.cej.2024.149352
在水处理中应用高级氧化工艺（AOPs）需要解决一些技术难题，如开发低成本的纳米催化剂合成技术、克服传质限制以及提高活性氧（ROS）的产量。本研究采用基于硼氢化钠（NaBH4）的简单还原技术合成超薄无定形氧化钴铁纳米片（A/Co3-Fe ONS），以激活过硫酸盐（PMS）。研究发现，由于这些纳米片具有丰富的反应位点、氧空位以及通过 O-O 和 S-O 键裂解产生 ROS 的能力，其性能优于晶体纳米片。与批量 PMS 介导的 AOP 反应器相比，将 A/Co3-Fe ONS 转化为片状膜可显著提高反应活性和功效（1290 倍），这是由于纳米钙化效应的缘故。淬火实验、固态和基于溶液的电子顺磁共振（EPR）光谱有助于确定涉及自由基和非自由基途径的反应机制。最后，A/CoFeOx 膜通过氧化还原电位差和氧空位促进的氧化还原再循环，实现了对各种有机微污染物（OMPs）的高效去除（>95%）、超快破坏（318 毫秒）和出色的稳定性（48 小时）。这种策略提供了一种低温成本效益高的替代方法，可考虑在水处理中加以推广。
Fig. 1. Schematic representation of the Co3-Fe ONS synthesis and membrane preparation.
Fig. 2. The structural characterization of Con-Fem ONS (n/m = 1/1, 1/3, 3/1) nanosheets. (a) SEM image, (b) EDS mapping (Co: dark cyan, Fe: green, O: red), (c, d) TEM images (inset: a detailed HR-TEM image), (e) XRD patterns, and (f) ATR-FTIR spectra. Unless otherwise stated, all the SEM and TEM images are obtained for the Co3-Fe ONS. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. Cross-section of the membranes with different thickness prepared using Co3-Fe ONS dispersion (a-e); mapping of Co (f), Fe (g), and O (h) in cross-section of the selected membrane; N2 adsorption/desorption isotherm (i), and pore size distribution of the selected membrane estimated using BJH model (j); and XPS survey spectrum (k) of the selected membrane.
Fig. 4. Performance of Con-Fem ONS and membranes for removal of BPA. (a) overall removal efficiency by PMS only, A/Co3-Fe ONS, and C/Co3-Fe ONS, as well as A/Co3-Fe ONS membrane. (b) The reaction rate constant (k) of different reaction systems; (c) comparison of different reaction systems with literature based on the normalized k values. This figure is based on the comparison and data presented in Table S2. (d) impact of catalyst loading and active layer thickness on membrane performance. (e) impact of retention time within membrane active layer on removal. The inset represents the k value of the membrane. Unless otherwise stated, Reaction parameters are as follows: [catalyst] = 50 mg/L; [PMS] = 0.5 mM; and [BPA] = 5 mg/L.
Fig. 5. EPR spectroscopy analysis for identification of SO4•– and HO• radicals (a): and 1O2 (b), the contribution of ROS to BPA degradation by A/Co3-Fe ONS membrane (c). Unless otherwise stated, reaction parameters are as follows: [catalyst] = 0.6 mg/cm2, [PMS] = 0.5 mM, [BPA] = 5 mg/L; [DMPO] = 60 mM, [TEMP] = 50 mM, [TBA] = 90 mM, [EtOH] = 90 mM, [L-his] = 0.5 mM, and [p-BQ] = 1 mM.
Fig. 6. The interaction between PMS and catalysts. (a-b) Electron density difference along with adsorption energies (Ead) and active bond length. Green and yellow isosurfaces represent charge accumulation and depletion, respectively. (c-d) Reaction pathways for PMS dissociation into radicals using the transition state searching method. The initial state (IS), transition state (TS), and final state (FS) are also shown. (e-g) Deconvoluted XPS spectra of Co 2p, O 1 s, and Fe 2p. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
这项研究首次证明了在膜封闭式 AOP 中使用 A/Con-Fem ONS 纳米催化剂的可行性。与晶体催化剂相比，A/Co3-Fe ONS 在降解探针污染物双酚 A 方面表现出更优越的反应动力学。理化表征、EPR 光谱和 DFT 表明，A/Co3-Fe ONS 性能的增强可归因于其丰富的活性位点、对 PMS 分子更强的亲和力、多种 PMS 解离/活化途径（如 O-O 和 S-O 裂解）以及充足的氧空位。为了进一步提高活性并解决批量 AOPs 中的传质限制等技术难题，A/Co3-Fe ONS 被加入到层状膜中，以便在其纳米多孔水通道（<25 nm）内进行密闭 AOP。在这种纳米级限制条件下，膜的 PMS 活化效率和反应动力学均有所提高。性能最好的反应膜的降解速度比批量 AOP 快 1290 倍。利用 XPS 分析对新鲜膜和使用过的膜进行的评估显示，活性物种（包括≡Co2+/≡Fe2+ 和 ≡Co3+/≡Fe3+）之间存在高效的氧化还原循环，使膜的性能在 48 小时内保持稳定。然而，同时存在的阴离子污染物，尤其是 HCO3-，可能会阻碍反应膜的去除。
Muhammad Bilal Asif, Seok-Jin Kim, Thien S. Nguyen, Javeed Mahmood, Cafer T. Yavuz, Highly efficient micropollutant decomposition by ultrathin amorphous cobalt-iron oxide nanosheets in peroxymonosulfate-mediated membrane-confined catalysis, Chemical Engineering Journal, 2024, https://doi.org/10.1016/j.cej.2024.149352
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