第一作者:Teer Ba
通讯作者:王晨 教授
通讯单位:齐鲁工业大学环境科学与工程学院
DOI:10.1016/j.jwpe.2023.103716
异质催化臭氧过程(HCOP)的工程应用受到了低效异质催化剂的严重阻碍。在此,我们采用水热法和溶胶-凝胶法制备了一种新型的分层核壳MnO2@mSiO2纳米反应器。在不同的反应参数下,通过阿特拉津(ATZ)在HCOP中的降解和矿化,系统地评估了其催化性能。在最佳参数下(O3/7.5 mg/L,ATZ/15 uM,催化剂/30 mg/L,pH=7),30分钟后可分别获得96.5%和36.1%的ATZ和总有机碳(TOC)的去除率。经过五个循环,MnO2@mSiO2的ATZ去除率只下降了约10%。核心和介孔外壳之间的协同效应对其高效的催化活性起到了至关重要的作用。大的比表面积和封闭的环境有利于臭氧的吸附和传质,并增强了ATZ、中间产物和氧化剂的富集。淬火实验和化学动力学模型表明,羟基自由基(-OH)是主要氧化剂。Mn3+/Mn4+和氧空位(OVs)作为活性位点,通过外壳促进的电子转移来促进臭氧的分解。这项工作为开发高效催化剂以用于HCOP的工程应用提供了新的进展。
在这项研究中,通过水热法和溶胶-凝胶法制备了一个核壳MnO2@mSiO2纳米反应器。该材料被评估为一种异质催化剂,通过HCOP降解水中的ATZ。本研究的主要目的是为HCOP的工程应用提供一种开发高效异质催化剂的新策略。系统地研究了实验参数对ATZ降解的影响,包括催化剂用量、臭氧用量、ATZ浓度和初始溶液pH值。淬火实验和化学动力学模型被用来识别和评估ROS的作用。还研究了活性点对臭氧分解的影响。最后,提出了ATZ降解的机制和途径。
Fig. 1. Preparation of catalyst (a) MnO2, (b) MnO2@mSiO2.Fig. 2. SEM images of MnO2 (a), and corresponding EDS element mapping spectrum (b and c). SEM images of MnO2@mSiO2 (d). HR-TEM images of MnO2@mSiO2 (e). SAED pattern of MnO2 (f). HAADF-STEM images of MnO2@mSiO2 (g), and corresponding element mapping (h-l).Fig. 3. XRD patterns (a), and FT-IR spectra (b) of MnO2 and MnO2@mSiO2. XPS spectra of SiO2 (C), and of MnO2@mSiO2 (d).Fig. 4. (a) ATZ degradation curves, (b) ATZ removal efficiency of various reaction, (c) the linear fit of ln (Ct/C0) versus reaction time, (d) values of the apparent first order reaction rate constant (Kapp) corresponding with linear fit. (e) Residual ozone concentration, (f) TOC removal efficiency. Experimental conditions: [ATZ] = 15uM, [catalyst] = 30 mg/L, [ozone] = 7.5 mg/L, pH = 7.0, T = 25 ± 2 °C, agitation speed = 300 rpm.Fig. 5. The effect of parameters changes. ATZ removal efficiency affected by (a) catalyst dosage, (d) ozone concentration, (g) ATZ concentration and (j) pH. Catalytic activity and synergy effect affected by (b) catalyst dosage, (e) ozone concentration, (h) ATZ concentration and (k) pH. TOC removal efficiency and residual ozone concentration affected by (c) catalyst dosage, (f) ozone concentration, (i) ATZ concentration and (l) pH. Experimental conditions: [ATZ] = 5-25uM, [catalyst] = 10 mg/L-50 mg/L (if used), [ozone] = 2.5 mg/L-12.5 mg/L (if used), pH = 3–11, T = 25 ± 2 °C, agitation speed = 300 rpm.Fig. 6. (a) Adsorbed ozone concentration on catalyst, (b) quenching experiment, (c) the linear fit of ln (Ct/C0) versus reaction time (insert: ozone decay curves), (c) the ozone exposure of SOP, MnO2 and MnO2@mSiO2 (insert: ozone decay curves), (d) ·OH exposure of SOP, MnO2 and MnO2@mSiO2 (linear fit) and contribution of ozone, ·OH and adsorption. Experimental conditions: [ATZ] = 15 uM (if used), [catalyst] = 30 mg/L (if used), [ozone] = 7.5 mg/L (if used), pH = 7, T = 25 ± 2 °C, agitation speed = 300 rpm.Fig. 7. XPS spectra of Mn 2p of (a) MnO2 and (b) MnO2@mSiO2 before and after the degradation reaction. XPS spectra of O 1 s of (c) MnO2 and (d) MnO2@mSiO2 before and after the degradation reaction.Fig. 8. The possible degradation pathway of ATZ in the MnO2@mSiO2 heterogeneous catalytic ozonation system. ATZ degradation initiated by (1) De-alkylation (1), (2) Alkylic-hydroxylation, (3) Alkylic-oxidation, (4) Dechlorination-hydroxylation. Experimental conditions: [ATZ] = 15 uM, [MnO2@mSiO2] = 30 mg/L, [ozone] = 7.5 mg/L (if used), pH = 7, T = 25 ± 2 °C, agitation speed = 300 rpm.Fig. 9. Assessment of acute and chronic toxicity toward fish, daphnia and green algae. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)Fig. 10. The proposed reaction mechanism of in the MnO2@mSiO2 heterogeneous catalytic ozonation system.Fig. 11. Catalyst stability and reusability. (a) SEM images of MnO2@mSiO2 after 5th, (b) TEM images of MnO2@SiO2 after 5th, (c) XRD spectra of MnO2@mSiO2 and (d) ATZ removal efficiency of MnO2@mSiO2.
综上所述,通过水热法和溶胶-凝胶法制备了一种新型的分层核壳MnO2@mSiO2异质催化剂纳米棒。在最佳参数下(O3/7.5 mg/L,ATZ/15 μM,催化剂/30 mg/L,pH=7),SOP、MnO2(HCOP)和MnO2@mSiO2(HCOP)的ATZ和TOC去除率分别为43.8 %和7.6 %,59.8 %和17.9 %,96.5 %和36.1 %。此外,pH值参数对MnO2@mSiO2(HCOP)的ATZ去除效率略有影响。MnO2@mSiO2的高催化活性表明,构建核壳结构是开发高效异质催化剂的有效策略。核心和介孔壳之间的协同效应对其高效的催化活性起到了至关重要的作用。介孔壳的大比表面积有利于臭氧的吸附和ATZ及中间产物的富集,从而使臭氧的利用率、ATZ的去除效率和矿化率都很高。Mn3+/Mn4+和氧空位(OVs)作为活性点,通过电子转移促进臭氧分解成ROS。这项工作为开发高效的HCOP异质催化剂提供了一个新的策略。具有高稳定性和催化性能的MnO2@mSiO2异质催化剂具有大规模工程应用的潜力。
Teer Ba, Chen Wang, Qing Feng, Jing Sun, Xiaoguo Shi, Hierarchical nano-reactor with core-shell structure for efficient removal of atrazine via heterogeneous catalytic ozonation: Experimental parameters, kinetics and performance analysis, Journal of Water Process Engineering, 2023, https://doi.org/10.1016/j.jwpe.2023.103716
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