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UiO-66复合材料的制备及其对有机污染物的吸附光催化性能研究
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/9/9 8:51:19  

摘要:随着工业和农业的不断发展,流入到水体的污染物与日俱增。其中,最典型的代表就是工业生产中的印染废水以及农业生产中的农药残留液。而且这两种类污染物都属于不易降解,能长期污染生态和人体的污染物。因此有效去除这些污染物势在必行。吸附法和光催化法由于操作简单,能耗低,无二次污染和高效率的优点,在环境污染物去除方面有着广泛地应用。因此,开发环境友好和有效的新型吸附剂和光催化剂将是一项有趣且必要的尝试。

金属有机骨架(MOFs)是近年来流行的新型微孔材料。由于具有高表面积,高孔隙率和可调性的特性,MOFs在气体储存,吸附,微电子和催化等许多领域出现。其中,Zr基MOFs(UiO-66)是有Zr6O4(OH)4和1,4-对苯二甲酸(H2BDC)连接体形成12配位高度填充的面心立方(fcc)结构(MOF的最高报告配位),因此其具有独特的性质,如稀有的水稳定性,优异的热稳定性和化学稳定性,光化学性质,即使在强酸和强碱环境下也能保持高稳定性。因此被成功运用于吸附,催化等诸多领域。本文中,我们选用UiO-66作为母体,通过原位精密合成和后合成修饰法制备了一系列新型的材料,致力于吸附和光催化领域的应用。具体工作如下:

(1)首先,我们在已有的Zr-MOFs材料UiO-66合成方法上进行加工,运用苯甲酸调节和氯仿活化的组合制备了UiO-66-A,UiO-66-B和UiO-66-BA吸附剂。通过XRD,FTIR,SEM,Zeta电位,N2 吸附脱附和TGA表征技术发现,在合成过程中引入苯甲酸和合成后用氯仿浸泡对UiO-66的成核和晶体生长有着很大影响。所制备的UiO-66-B和UiO-66-BA吸附剂对刚果红染料溶液的最大吸附量可达1100 mg·g–1和1371 mg·g–1,是常规UiO-66吸附量的5~7倍,且具有高达5次的重复利用率。吸附机理通过吸附动力学,等温线,热力学和溶液pH实验得出,UiO-66-BA吸附剂对刚果红的吸附过程属于单层均匀的物理吸热反应。更大的比表面积,更多的吸附活性位点以及更好的疏水性可以解释吸附量增加的原因。同时与类似吸附剂进行比较发现,用苯甲酸调节和氯仿活化制备的UiO-66在液相吸附刚果红染料方面具有优越性。

(2)其次,我们采用化学质子化涂层法合成了一种新型MOFs复合材料UiO-66/g-C3N4,并进一步采用光沉积法制备了三元复合光催化剂UiO-66/g-C3N4/Ag。通过XRD,FT-IR,TEM,SEM-EDS,XPS,N2 吸附脱附,TGA,PL,UV-vis DRS和EIS表征技术研究了这些催化剂的物理和化学参数,晶体形态,光学性能和电化学性质。结果表明,添加质量比为15%的g-C3N4使得UiO-66/g-C3N4/Ag(15)具有最佳的可见光光催化活性。目标污染物如罗丹明B染料和2,4-二氯苯氧基乙酸(2,4-D)的降解实验表明,UiO-66/g-C3N4/Ag(15)的光催化能力较母体材料大大提高。在罗丹明B染料降解实验实验中,UiO-66/g-C3N4/Ag(15)对其降解率高到92 %,催化降解速率分别是母体材料g-C3N4和UiO-66的26.7和4.6倍。在2,4-二氯苯氧基乙酸农药降解实验实验中,UiO-66/g-C3N4/Ag(15)对其降解率高到84 %,催化降解速率分别是母体材料g-C3N4和UiO-66的18.8和5.2倍。此外,该复合材料UiO-66/g-C3N4/Ag在6个循环中表现出稳定性和重复使用性。活性物质的捕获实验表明,·O2-,h+和·OH是罗丹明B和2,4-D光催化降解的主要原因。

With the continuous development of industryand agriculture, contaminants that flow into water bodies are increasing. Amongthem, the most typical representatives are printing and dyeing wastewater inindustrial production and pesticide residues in agricultural production.Moreover, these two types of pollutants are non-degradable and can pollute theecological and human pollutants for a long time. Therefore, it is imperative toeffectively remove these pollutants. The adsorption method and thephotocatalytic method have wide application in environmental pollutant removalbecause of simple operation, low energy consumption, no secondary pollution andhigh efficiency. Therefore, the development of environmentally friendly andeffective new adsorbents and photocatalysts will be an interesting andnecessary attempt.

Metal-organic frameworks (MOFs) are newmicroporous materials that have become popular in recent years. Due to theirhigh surface area, high porosity and tunability, MOFs have emerged in manyfields such as gas storage, adsorption, microelectronics and catalysis. Amongthem, Zr-based MOF (UiO-66) is a face-centered cubic (fcc) structure with a12-coordinated height-filled Zr6O4(OH)4 and 1,4-terephthalic acid (H2BDC)linker (MOFs' highest reported coordination). Therefore, it has uniqueproperties such as rare water stability, excellent thermal stability chemicalstability, and photochemical properties, which maintain high stability even instrong acid and alkali environments. Therefore, it has been successfullyapplied to many fields such as adsorption and catalysis. In this paper, UiO-66is used as the matrix, and a series of new materials have been prepared byin-situ precision synthesis and post-synthesis modification, which are devotedto the application in adsorption and photocatalysis. The specific work is asfollows:

(1) First, we processed the existingZr-MOFs material UiO-66 synthesis method. UiO-66-A, UiO-66-B and UiO-66-BAadsorbents were prepared using a combination of benzoic acid conditioning andchloroform activation. It was found that the introduction of benzoic acidduring synthesis and chloroform immersion after synthesis had a great influenceon the nucleation and crystal growth of UiO-66 through XRD, FTIR, SEM, Zetapotential, N2 adsorption desorption and TGA characterization techniques. Theprepared UiO-66-B and UiO-66-BA adsorbents could absorb up to 1100 mg·g–1 and1371 mg·g–1 of Congo red dye solution, which was 5-7 times the amount ofconventional UiO-66 adsorption, and be reused up to 5 times. The adsorptionmechanism was obtained by adsorption kinetics, isotherm, thermodynamics andsolution pH experiments. The adsorption mechanism was obtained by adsorptionkinetics, isotherm, thermodynamics and solution pH experiments. The adsorptionprocess of Cono red by UiO-66-BA adsorbent belongs to a single layer of uniformphysical endothermic reaction. A larger specific surface area, more adsorptionactive sites, and better hydrophobicity can explain the increase in adsorption.At the same time, compared with similar adsorbents, it was found that UiO-66prepared by benzoic acid adjustment and chloroform activation has superiorityin liquid phase adsorption of Congo red dye.

(2) Secondly, a new MOFs composite materialUiO-66/g-C3N4 was synthesized by chemical protonation coating method, and theternary composite photocatalyst UiO-66/g-C3N4/Ag was prepared byphotodeposition method. The physical and chemical parameters, crystalmorphology, optical properties and electrical properties of these catalystswere investigated by XRD, FT-IR, TEM, SEM-EDS, XPS, N2 adsorption-desorptionisotherm, TGA, PL, UV-vis DRS and EIS characterization techniques. The resultsshow that the addition of g-C3N4 with a mass ratio of 15% makes UiO-66/g-C3N4/Ag(15)have the best visible light photocatalytic activity. Degradation experiments oftarget pollutants such as Rhodamine B dye and 2,4-dichlorophenoxyacetic acid.

关键词:UiO-66;染料;农药;吸附;光催化

UiO-66; Dye; Pesticide; Adsorption;Photocatalysi

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