Fe-Ti-SBA-15介孔材料的制备及光催化性能研究

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3.0 侯斌 2024-11-19 5 4 2.62MB 51 页 15积分

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摘要

水环境污染是当今世界面临的一个重大的亟需解决的问题。据统计，全世界

每年约向自然水体排入 4200 多亿立方米的污水，致使全球径流总量 14%以上的

淡水遭到污染。世界范围内水体污染主要来源于工业废水。工业生产过程的各个

环节都可能会有生产用料、中间产物、副产品随水流失并产生污染物，未经处理

的工业废水、废渣排入自然水体成为水污染的重要原因。源自金属冶炼、电镀、

造纸、纺织印染、皮毛加工及制革等行业的工业废水由于排放量大，废水中含有

大量的重金属离子、有机物等且水质变化大，较难处理，成为水体工业污染的重

要来源。传统的污水处理方法与近年来兴起的生物氧化技术存在着运行费用高，

能耗大，处理不完全等缺点。因此，研究高效低耗的污染物去除方法受到科研人

员的普遍重视。

1972 年首次报道的光催化水分解制氢的研究引发了光催化技术的研究热潮。

在众多的半导体光催化剂中，TiO2因具有性质稳定、无毒价廉、可有效吸收太阳

光中的弱紫外部分以及催化活性强等优点而成为研究的首选。但在实际光催化技

术应用中，TiO2存在的缺点也较为突出，主要集中于光量子效率较低和不易分离

回收等方面，因此对 TiO2进行结构改性和形貌控制尤为重要。已报道的结构改

性方法中，金属离子（非金属）和半导体掺杂对提高二氧化钛光学活性颇为有效。

研究表明， Fe 离子与 Ti 原子具有相当的原子尺寸，能够取代 Ti 原子并嵌入纳

米TiO2的晶格内，引起二氧化钛的吸收边红移和杂质能级的产生，从而提高太

阳光的利用率并降低光生电子和空穴的复合率，提高材料的光催化性能。另外纳

米TiO2在水体中易于团聚，给后期回收利用带来一定困难，也会造成有效作用

面积大大降低，直接影响光催化去除性能。若将改性的纳米 TiO2半导体负载到

合适的介孔材料上，可同时达到增大催化剂的有效作用面积及便于回收利用双重

效果，另外介孔材料的较大比表面积可有效吸附污染物分子，对光催化过程起到

积极的协同作用。

上述复合介孔材料的制备途径一般可分为一步合成法和后嫁接法（后合成

法）。通过前期的试验结果发现，后嫁接法制备的催化材料未能实现铁离子与 TiO2

的有效接触，不能有效地拓展催化材料的光吸收范围，材料在可见光区不具备催

化性能。因此，本研究采取一步合成法直接合成复合介孔催化材料，即以三嵌段

共聚物 P123 为模板剂，正硅酸四乙酯为硅源，钛酸四丁酯为钛源，九水合硝酸

铁为铁源，水热法一步合成 Fe-Ti-SBA-15 复合材料。随后对其进行一系列的结

构和形貌分析表征，如透射电镜（TEM），扫描电镜（SEM），氮气吸附脱附，紫

外可见漫反射（Uv-vis DRS）， X射线粉末衍射光谱（XRD）， X射线光电子能谱

（XPS）等。结果表明，制备的样品均具有规则的六方介孔结构，TiO2部分插入

硅氧四面体晶格，部分以纳米颗粒形态进入 SBA-15 的孔道。Fe 元素主要以 Fe3+

的形式插入 TiO2的晶格中，从而造成 TiO2的吸收边发生明显的红移，进入可见

光区，为材料的可见光催化性能的实现提供了可能。通过光催化性能测试，复合

介孔材料具有良好的可见光光催化还原六价铬离子(Cr(VI))和降解染料亚甲基蓝

（MB）的能力。当 MB 和Cr(VI)同时存在的时候，其相应光催化还原和氧化能

力得到显著增强，归结于材料光生电子和空穴的充分利用，即协同催化。通过光

催化实验结果得出最佳 Fe 和Ti 的掺杂量，并探讨了光催化反应的机理和光催化

性能增强的机制。本实验不仅提供了一种简单快速方便的 Fe-Ti-SBA-15 的合成

方法，还对铁改性二氧化钛的光催化机制进行了有益讨论，为该材料在水体中污

染物的控制及治理应用提供了前期实验基础。

关键词：一步合成法 Fe-Ti-SBA-15 可见光协同降解亚甲基蓝六

价铬离子

ABSTRACT

Nowadays, water pollution as a serious problem is urgently to be solved in the

world. According to statistics, about 4.2×1011 m3 of wastewater is discharged into rivers

and lakes annually, leaving about 5.5×1012 m3 polluted water that is approximately

equal to 14 % the total global fresh water. Worldwide water pollution mainly comes

from industrial wastewater generated in industrial production processes, since raw

materials, intermediates, and some by-products, together with waste residue may leak

out into natural water. Industrial waste water from metal smelting, electroplating,

papermaking, textile printing and dyeing, and fur treament and leather industries

contains a large number of heavy metal ions, organic matters and its quality is largely

changed, becoming the important source of industrial water pollution. The traditional

wastewater treatment methods and biological oxidation technology developed in recent

years have drawbacks of has high operation cost, large energy consumption, and

insufficient remediation. As a result, advancement of efficient pollution destruction

methods with low energy consumption attracts much attention from researchers.

Since the first report of catalytically splitting water to produce gaseous hydrogen

in 1972, a hot wave of researches towards photocatalytic technology has been raised.

Among numerous semiconductors, titanium dioxide (TiO2) is the most important

candidate in terms of photocatalysis, due to its favorable properties of satisfactory

stability, nontoxicity, low cost, and effective absorption of near ultraviolet rays in solar

spectrum. However, real applications of TiO2 greatly suffer from low light quantum

efficiency and difficult separation and regeneration of catalysts after treatment, which

can be overcome through structural modification and morphology control of TiO2.

Metal ions doping and semiconductor coupling are effective to improve photocatalytic

performance of TiO2. It was reported that some metal ions with proper atomic diameters

like Fe ions tend to replace Ti species in the lattice of TiO2 nanoparticles, leading to the

phase change and low recombination of electrons and holes, thus improving

photocatalytic outcome. In addition, nanosized TiO2 is easy to agglomerate in water,

resulting into the difficulty of catalyst recovery and shrinkage of effective area

containing active sites, further affecting photocatalysis. If modified TiO2 nanoparticles

anchor onto mesoporous supports, both enlarged effective area and ease of recovery are

proposed to achieve. Moreover, large specific surface area of mesoporous supports

enhances the pollutants adsorption and catalytic degradation.

Above mentioned mesoporous composites are generally fabricated via one-pot or

post synthetic routes. Basing upon our experimental results, effective contact between

iron ions and TiO2 cannot occurred by means of post synthetic methods, thus visible-

light driven photocatalysis is unable to achieve. Therefore, mesoporous iron-contained

composites in this study were prepared through one-pot hydrothermal synthesis, in which

P123, tetraethoxysilane, tetrabutyl titanate, and ferric nitrate nonahydrate were adopted

as templating reagent, silicon source, titanium source, iron source, respectively. These

samples were exposed to a series of characterizations, such as transmission electron

microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption-

desorption, Uv-vis diffuse reflection (Uv-vis DRS), X-ray diffraction spectra (XRD),

and X-ray photoelectron spectroscopy (XPS). As expected, obtained samples have

hexagonally ordered pore array structures with some Ti species replacing Si atoms in

crystal lattices. Besides, some nanosized TiO2 particles get into pores of SBA-15. .The

light absorption of samples is expanded with the absorption edge obviously blue-shifted,

mainly attributing to the Fe elements inserted into the lattice of TiO2 in the form of Fe3+,

thus causing the capability of photocatalytic degradation in the visible light region.

Composite materials exhibited satisfactory reduction and degradation ability towards

treating hexavalent chromium (Cr (VI)) and dye methylene blue (MB) under visible

light illumination. Especially, the reductive and oxidative abilities of target samples

were greatly enhanced with the coexistence of hexavalent chromium (Cr (VI)) and MB,

ascribing to the full usage of photogenerated electrons and holes when both reducible

and oxidable are present. The Fe and Ti doping amount were optimized by correlating

with the corresponding catalytic performance. Finally, the enhancement of

photocatalysis was explained and a possible mechanism was proposed basing upon

active species trapping experiments.

Key Words: one-step synthetic method, Fe-Ti-SBA-15, visible light,

synergistic, methylene blue, Cr (VI)

中文摘要

ABSTRACT

第一章绪论.................................................................................................................. 1

1.1 研究背景与课题意义......................................................................................... 1

1.2 纳米 TiO2半导体的性质及光催化研究现状 .................................................... 2

1.2.1 纳米 TiO2的结构与性质 ............................................................................ 2

1.2.2 纳米 TiO2的制备 ........................................................................................ 3

1.2.3 改性纳米 TiO2的方法 ................................................................................ 3

1.2.4 纳米 TiO2的固定化研究 ............................................................................. 5

1.3 介孔分子筛 SBA-15 研究进展 ......................................................................... 6

1.3.1 介孔分子筛的合成机理.............................................................................. 6

1.3.2 SBA-15 的性质 ............................................................................................ 7

1.3.3 SBA-15 的改性研究 .................................................................................... 8

1.4 光催化技术的研究进展................................................................................... 10

1.4.1 光催化技术简介........................................................................................ 10

1.4.2 光催化原理与影响因素............................................................................ 11

1.4.3 光催化技术在环境方面的应用研究......................................................... 11

第二章 Fe 掺杂 TiO2的制备与光催化性能研究 ..................................................... 15

2.1 Fe 掺杂纳米 TiO2的制备 ................................................................................. 15

2.1.1 实验试剂与仪器........................................................................................ 15

2.1.2 制备方法.................................................................................................... 16

2.2 Fe 掺杂纳米 TiO2的表征 ................................................................................. 16

2.2.1 Fe 掺杂纳米 TiO2的X射线衍射图谱（XRD） ..................................... 16

2.2.2 Fe 掺杂纳米 TiO2的紫外可见漫反射图谱（UV-vis DRS） .................. 17

2.2.3 光催化性能的测试.................................................................................... 18

2.3 本章小结............................................................................................................ 19

第三章复合光催化剂 Fe-Ti-SBA-15 的合成与光催化性能研究 .......................... 21

3.1 复合光催化剂 Fe-Ti-SBA-15 的制备 .............................................................. 21

3.1.1 试剂与仪器................................................................................................ 21

3.1.2 制备方法.................................................................................................... 22

3.2 表征方法............................................................................................................ 22

3.3 表征结果与分析............................................................................................... 23

3.4 光催化应用的研究........................................................................................... 28

3.4.1 光催化降解 MB 和光催化还原 Cr(VI)实验 ........................................... 28

3.4.2 协同降解 MB 和Cr(VI)实验 ................................................................... 29

3.4.3 光催化机理................................................................................................. 30

3.4.4 复合材料的光催化机制提出.................................................................... 31

3.5 复合材料的重复性利用.................................................................................... 32

3.6 复合材料的磁性分析与分离回收................................................................... 33

3.7.本章小结............................................................................................................ 34

第四章结论与展望.................................................................................................... 35

4.1 Fe 掺杂 TiO2的制备与光催化性能研究 ......................................................... 35

4.2 Fe-Ti-SBA-15 的合成与光催化性能研究 ....................................................... 35

4.3 展望................................................................................................................... 36

参考文献...................................................................................................................... 37

在读期间公开发表的论文和承担科研项目及取得成果.......................................... 46

致谢.............................................................................................................................. 47

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摘要：

摘要水环境污染是当今世界面临的一个重大的亟需解决的问题。据统计，全世界每年约向自然水体排入4200多亿立方米的污水，致使全球径流总量14%以上的淡水遭到污染。世界范围内水体污染主要来源于工业废水。工业生产过程的各个环节都可能会有生产用料、中间产物、副产品随水流失并产生污染物，未经处理的工业废水、废渣排入自然水体成为水污染的重要原因。源自金属冶炼、电镀、造纸、纺织印染、皮毛加工及制革等行业的工业废水由于排放量大，废水中含有大量的重金属离子、有机物等且水质变化大，较难处理，成为水体工业污染的重要来源。传统的污水处理方法与近年来兴起的生物氧化技术存在着运行费用高，能耗大，处理不完全等缺点。因此，研究...

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