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频繁的工业生产活动排放了越来越多成分复杂的废水,导致了严重的环境问题,造成了极大的环境压力。工业过程产生的废水中大多都含有毒有害的污染物,不适合直接利用传统的污水处理技术进行处置。当前,膜分离、吸附、混凝等技术只能将污染物富集或从水中物理分离,而不能将其降解或矿化。化学氧化技术尽管能将有机污染物转化或矿化,但有可能产生毒性更强的中间产物而带来二次污染。
以半导体催化剂(TiO2、ZnO、Fe2O3)为基础的光催化技术能对持久性有机污染物部分或完全分解,甚至可以彻底矿化成CO2、H2O、
${\rm{NO}}_3^- $ 、${\rm{PO}}_4^{3-} $ 和卤离子等[1]。在众多新兴光催化材料中,金属-有机骨架(MOFs)在光催化降解有机污染物方面展现出优异的性能。MOFs由金属离子或簇和多齿状有机配体(如芳香族羧酸、咪唑等)配位,并通过自组装方式形成高度有序的无机-有机杂化材料[2]。除结构多样、可调外,MOFs还具比表面积巨大、暴露的活性位点丰富以及易与其它功能材料复合等优势,因此受到各领域科研人员的极大关注[3-7]。2-甲基咪唑锌(又称ZIF-8或MAF-4)是一种具类沸石结构的MOF材料,由中山大学陈小明院士课题组首先合成并报道[8]。研究表明,ZIF-8能通过多种方法制备,例如溶剂热(N,N-二甲基甲酰胺、甲醇为溶剂)、微波辅助、声化学、机械化学、干凝胶等[9]。ZIF-8具有比表面积大、孔径尺寸较小(用于分子筛的ZIF-8的有效孔径在4.0 nm至4.2 nm的范围内[10])等特点,因此可以对H2和CH4等气体进行分离。然而,研究显示,动力学直径大于4.2 nm的大分子也能被ZIF-8缓慢吸附并进入孔笼,表明其结构具有柔性[11]。由于ZIF-8独特的结构和性能,使其在气体存储[12]、吸附与分离[13-17]、(光)催化[18-19]、药物缓释[20]等领域广泛应用。目前,越来越多的研究者对ZIF-8光催化性能产生兴趣,王崇臣课题组首先发现ZIF-8在紫外线照射下可实现光催化降解有机染料亚甲基蓝,基于质谱分析数据分析亚甲基蓝的光催化降解路径,并根据活性物质的种类研究了其光催化反应机理[21]。但是,ZIF-8因具有宽带隙(Eg = 5.1 eV)而仅能被紫外光激发。为进一步增强ZIF-8的光催化性能,相关研究者将其与半导体光催化剂进行复合,使所得到的复合物在可见光照射下能表现出令人满意的光催化性能。
本文将选择一些典型的ZIF-8复合物,介绍其制备的方法,并详细探讨其光催化还原Cr(Ⅵ)和光催化降解染料、农药、药物及个人护理品(PPCPs)的性能与机理,总结其优势与不足,以期为相关研究者提供系统的文献梳理与总结。
ZIF-8复合物光催化去除水体污染物
Photocatalytic removal of water pollutants in ZIF-8 composites
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摘要: 金属-有机骨架及其复合物材料由于具有独特的结构和卓越的性能,逐渐在水处理研究领域得到了广泛关注。本综述详细探讨了ZIF-8复合材料的一般合成方法及其光催化去除各类水体污染物的研究进展,旨在为ZIF-8复合物光催化去除水体污染物的研究方向提供一个便于理解的概述。根据ZIF-8复合物研究现状和进展,本文对其在光催化去除环境污染物方面的发展趋势做出展望。Abstract: Metal-organic frameworks and its composite materials have been paid more and more attention in the field of water treatment due to their unique structure and excellent properties. In this review, the general synthesis methods of ZIF-8 composite materials and the research progress of photocatalytic removal of various pollutants from water are discussed in detail, aiming to provide a convenient overview for the research direction of photocatalytic removal of pollutants from water by ZIF-8 composite materials. According to the research status and progress of ZIF-8 composites, the development trend of its photocatalytic removal of environmental pollutants is prospected in this paper.
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图 3 (a)样品的XPS;(b) ZIF-8和MZ-15的孔径分布;(c)样品的XRD图谱;(d)和(e)为MoO3纳米线和ZIF-8纳米粒子的TEM图像;(f) MoO3@ZIF-8核-壳纳米棒(MZ-15)的TEM图像[41]
Figure 3. (a)XPS of as prepared samples; (b)Pore size distribution of ZIF-8 and MZ-15; (c)XRD patterns of as prepared samples; (d) and (e) TEM images of MoO3 nanowires and ZIF-8 nanoparticles; (f) TEM of MoO3@ZIF-8 core-shell nanorods (MZ-15)[41]
图 4 (a)样品的紫外-可见漫反射谱图,嵌入图显示了样品的带隙值;(b) MZ-15在可见光照射下的光催化性能;(c) MZ-15(50 mg催化剂,100 ml Cr(Ⅵ),20 mg·L−1)的循环实验;(d) Cr(Ⅵ)的还原机理图[41]
Figure 4. (a) UV-vis spectra of samples. The inset figures exhibited the corresponding band gap of samples; (b)Photocatalytic performance of MZ-15 under visible light irradiation; (c)Cycling runs of MZ-15 (50 mg catalyst, 100 ml Cr(Ⅵ), 20 mg·L−1); (d) Schematic illustration of the Cr(Ⅵ) reduction mechanism[41]
图 5 (a)ZIF-8,B@Z-7,B@Z-10和B@Z-25的XRD图谱; (b) Bi2S3,(c)纯ZIF-8,(d) B@Z-10的SEM图像;(e) Bi2S3的TEM图像,(f) B@Z-10的TEM图像[37]
Figure 5. (a)XRD patterns of ZIF-8, B@Z-7, B@Z-10 and B@Z-25; SEM images of (b) Pristine Bi2S3,(c) Pure ZIF-8, (d) B@Z-10; (e) TEM image of the obtained Bi2S3, (f) TEM images of the B@Z-10[37]
图 6 (a) 不同光催化剂可见光下降解RhB(C0=10 mg·L−1)的效率图;(b)B@Z-10光催化降解RhB循环实验;(c) B@Z-10降解RhB活性物质捕捉;(d) B@Z-10光催化降解RhB的机理简图[37]
Figure 6. (a) Photocatalytic degradation of RhB (C0 =10 mg·L−1) over the samples under visible light irradiation; (b) The cycling of the degradation of RhB in B@Z-10; (c) Effects of different scavengers on RhB degradation in the presence of B@Z-10; (d) A simplified diagram of photocatalytic RhB degradation mechanism of B@Z-10[37]
图 7 (a) g-C3N4,ZIF-8和C3N4-ZIF-8 (ZC)复合材料的XRD图谱(标为•的峰表示C3N4相,其余峰均为ZIF-8);(b) g-C3N4,(c) ZIF-8,(d) C3N4-ZIF-8 (ZC)复合材料的SEM图像; (e) g-C3N4,ZIF-8和C3N4-ZIF-8 (ZC)复合材料的N2吸附-脱附等温线[23]
Figure 7. (a)XRD patterns of the as prepared g-C3N4, ZIF-8, and C3N4-ZIF-8 (ZC) composite (Peaks marked • represent C3N4 phases and the remaining peaks are all of ZIF-8); SEM images of (b) g-C3N4, (c) ZIF-8, (d) C3N4-ZIF-8 (ZC) composite; (e)N2 adsorption-desorption isotherms of g-C3N4, ZIF-8, and C3N4-ZIF-8 (ZC) composite[23]
图 8 (a)g-C3N4,ZIF-8和C3N4-ZIF-8 (ZC)复合材料的紫外可见吸收光谱;(b)g-C3N4,ZIF-8和C3N4-ZIF-8 (ZC)复合材料对TC(C0= 200 µmol·L−1)的光催化降解;(c) C3N4-ZIF-8 (ZC)复合材料的吸附与光催化降解的循环实验;(d) C3N4-ZIF-8 (ZC)复合材料对四环素的吸附和光催化降解机理图[23]
Figure 8. (a) UV-vis absorption spectra of g-C3N4, ZIF-8, and C3N4-ZIF-8 (ZC) composite; (b)Photocatalytic degradation profile of TC(C0= 200 µmol·L−1) using g-C3N4, ZIF-8, and C3N4-ZIF-8 (ZC) composite; (c)The repetitive adsorption and photocatalytic degradation cycles of C3N4-ZIF-8 (ZC) composite; (d)Schematic illustrating the adsorption and photocatalytic degradation mechanisms of tetracycline by C3N4-ZIF-8 (ZC) composite[23]
表 1 ZIF-8复合物光催化去除水体污染物的典型案例
Table 1. Typical cases of photocatalytic removal of water pollutants by ZIF-8 composites
ZIF-8复合材料
ZIF-8 composites污染物
Pollutants反应时间/min
Reaction time去除率/%
Removal efficiency参考文献
ReferencesBi2MoO6/ZIF-8 亚甲基蓝 100 66.88 [22] C3N4-ZIF-8 四环素 60 96 [23] Ag/AgCl@ZIF-8/g-C3N4 左氧氟沙星(LVFX) 60 87.3 [24] ZIF-8@Fe2O3 活性红198 90 94 [25] Fe3O4@ZIF-8 亚甲基蓝 120 98.5 [26] MoS2/ZIF-8 环丙沙星和四环素盐酸盐 180 93.2 [27] ZIF-8/NF-TiO2 磺胺二甲嘧啶 180 81.3 [28] ZIF-8/TiO2 酸性蓝92 180 96 [29] ZIF-8/MnFe2O4 四环素 100 92 [30] Ag/AgCl@ZIF-8 亚甲基蓝 20 100 [31] Ag/AgCl@ZIF-8 对乙酰氨基酚 90 99 [32] Cd0.5Zn0.5S@ZIF-8 六价铬 30 100 [33] Pt/ZIF-8/TiO2NTs 苯酚 120 18.6 [34] Ag@AgCl/Ag纳米膜/ZIF-8 亚甲基蓝 12 53.39 [35] Ag/AgCl/ZIF-8 罗丹明B 60 98 [36] Bi2S3@ZIF-8 罗丹明B 90 97 [37] WO3@ZIF-8 亚甲基蓝 120 90.6 [38] TiO2/ZIF-8 罗丹明B 24 100 [39] ZnO@ZIF-8 六价铬 70 100 [40] MoO3@ZIF-8 六价铬 40 100 [41] CuPd@ZIF-8 六价铬 60 89 [42] ZIF-8/Ag/AgCl/TiO2 亚甲基蓝 180 96 [43] ZIF-67@ZIF-8@MIL-125-NH2 α-萘酚 120 98.9 [44] CuInS2@ZIF-8 罗丹明B 30 91 [45] Fe3O4-COOH@ZIF-8/Ag/Ag3PO4 二嗪农 55 99.7 [46] ZIF-8/g-C3N4 四环素 30 74 [47] ZIF-8/g-C3N4 罗丹明B 75 100 [47] ZIF-8/g-C3N4 甲基橙 180 786 [47] AgBr/ZIF-8 亚甲基蓝 60 80 [48] 注:NF即N和F元素.
Note: NF means N and F elements, respectively.表 2 不同材料在可见光下的光催化性能[46]
Table 2. Photocatalytic performances of different materials under visible light[46]
样品
Sample吸附的二嗪农a /%
Adsorbed Diazinon a降解的二嗪农b /%
Degraded Diazinon b二嗪农去除率c/%
Diazinon removal efficiency cFe3O4 2.5 33.2 35.7 ZIF-8 12.6 29.8 42.4 Ag/Ag3PO4 31.6 54.7 86.3 Fe3O4-COOH@ZIF-8 2.5 34.5 37.0 Fe3O4-COOH@ZIF-8/Ag/Ag3PO4 36.3 63.4 99.7 Fe3O4-COOH@ZIF-8/Ag/Ag3PO4 M 18.4 48.9 77.3 a在黑暗中搅拌20 min后用紫外-可见分光光度法测定,b在可见光照射55 min后用紫外-可见分光光度法测定,c反应75 min后去除的染料总量。反应条件:Co二嗪农 =20 mg·L−1,光催化剂用量0.2 g·L−1,在黑暗20 min和在可见光下55 min,pH = 7。 a Determined with UV–vis after 20 min of stirring in dark, b Determined with UV–vis after 55 min of vis-light irradiation, c The total amount of dye removal after 75 min of reaction.Reaction conditions: Co Diazinon =20 mg L−1, the photocatalyst dosage: 0.2 g·L−1, at 20 min dark and 55 min under visible light at pH = 7[46]. -
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