第一作者：Minghui Xiang
通讯作者：张进 博士后/李辉 研究员
通讯单位：上海大学环境与化学工程学院
DOI:10.1016/j.cej.2024.154983
在过一硫酸盐（PMS）活化过程中，电子传递过程（ETP）几乎不受半衰期和迁移距离的影响，因为它直接从污染物中提取电子进行氧化。然而，由于 PMS 和污染物的传质能力较差，要提高 ETP 的选择性仍然具有挑战性。在这项研究中，设计了具有高反应物扩散动力学和多种扩散模式的二维多孔掺杂 N 的碳 (PNC)，以诱导层间限制，从而高效活化 PMS 并提高 ETP 选择性。以四溴双酚 A 为目标污染物，封闭的 PNC/PMS 系统显著提高了 PMS 的活化性能，ETP 的选择性高达 97.8%。根据扩散模型，分子通道的构建促进了反应物向催化剂内部层间空间的垂直传质。密度泛函理论计算表明，随后引发的层间限制促进了 PMS/污染物在层间表面的共吸附，缩小了电荷迁移的能隙，从而提高了 PMS 的活化性能和 ETP 的选择性。得益于几乎 100% 的 ETP 选择性，密闭 PNC/PMS 系统大幅提高了 PMS 的利用效率，对各种水基质的抗干扰能力令人赞叹，并且在连续流反应器中具有长期稳定性。这项工作为在水修复中通过层间封闭高效、选择性地活化 PMS 提供了一种新方案。
Fig. 1. a) Schematic illustration of catalyst synthesis, b) SEM and c) TEM image of PNC, d) Raman spectra, e) N2 adsorption–desorption isotherms, f) High-resolution XPS spectra of N 1s, and g) N K-edge NEXAFS spectra of PNC and NC.
Fig. 2. a) TBBPA removal efficiencies in different systems, b) Pseudo-first-order kinetics of TBBPA degradation, the intrinsic activities (kSA) of the catalysts, and the PMS utilization efficiency (UPMS) in different systems, c) EPR spectra of DMPOX, DMPO-O2− and TEMP-1O2, d) TBBPA removal rate in PNC/PMS and NC/PMS systems with different scavengers, e) UV–vis spectra of NBT in different systems, f) UV–vis spectra of DPBF in different system and g) The degradation of DPBF in various systems and kinetic studies of different systems in 1O2 generation. Reaction conditions: [catalysts] = 0.04 g/L, [TBBPA] = 20 mg/L, [PMS] = 0.6 mM, [MeOH] = [TBA] = 500 mM, [p-BQ] = 5 mM, [β-carotene] = 0.2 mM, [DPBF] = 4 mg/L.
Fig. 3. a) Open circuit potential (OCP) in different systems, b) Current change values in the GOS (inset: Schematic illustration of GOS), c) TBBPA degradation and PMS concentration in the GOS, d) In-situ Raman spectra, e) 1O2 steady-state concentration in different systems and f) The contribution of 1O2 and ETP for TBBPA degradation in different systems. Reaction conditions: [catalysts] = 0.04 g/L, [TBBPA] = 20 mg/L, [PMS] = 0.6 mM.
Fig. 4. a) Deff of all sizes of reactants, b) Illustration of the vertical mass transfer of reactants into the internal layers of catalysts, c) The concentration of reactants in different depth below catalysts surface, d) Eads and charge difference distribution of possible active sites in confined and unconfined systems, e) Electron-transfer pathway driven by potential energy difference, and f) Illustration of the enhancement mechanism of PMS activation and ETP selectivity.
Fig. 5. a) The influence of environmental factors on TBBPA degradation, 3D-EEM fluorescence spectra of actual underground wastewater b) before and c) after reaction in the PNC/PMS system, and d) TBBPA degradation in the continuous-flow reactor (inset: diagram of the continuous-flow reactor). Reaction conditions: [catalysts] = 100 mg, [TBBPA] = 10 mg/L, [PMS] = 0.3 mM, flow rate = 100 mL/h, hydraulic retention time = 7 min.
总之，分子隧道的构建使得 PNC 具有快速的反应物扩散动力学和多种扩散模式，从而引发了层间限制，进而促进了 PMS 的活化（kobs = 0.3280 min-1），其 ETP 选择性几乎达到 100%。由于层间限制，PMS/TBBPA 和催化剂之间的电子相互作用增强，TBBPA 和 PMS 之间电荷转移的能隙缩小。密闭的 PNC/PMS 系统不仅有效利用了 PMS，而且在降解 TBBPA 的过程中，由于 ETP 选择性高，对无机离子、天然有机物和 pH 值都有很好的抗干扰能力。更重要的是，PNC/PMS 系统实现了令人赞叹的活性和稳定性，在连续流反应器中 5 天内就降解了 100% 的 TBBPA。这些发现对基于 PMS 的异构水净化具有重要意义。污染物和 PMS 的有效扩散使催化剂能够捕获并降解实际废水修复中的各种微污染物。此外，通过 ETP 选择性活化 PMS 来降解污染物，氧化剂利用效率更高，且无需溶解氧，可降低运行成本，对生态系统的干扰也更小。因此，本研究为诱导层间限制以实现快速、选择性和稳定的水净化提供了一种新方法。
Minghui Xiang, Shiting Zhu, Xinlei Ren, Zhiyuan Yang, Chen Wang, Long Chen, Jin Zhang, Hui Li, Fast diffusion kinetics improves electron transfer regime selectivity to boost peroxymonosulfate activation, Chemical Engineering Journal, 2024, https://doi.org/10.1016/j.cej.2024.154983
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