纳米TiO_2/粘土复合材料的制备及其对甲基橙的光催化降解研究
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摘要
紫外光催化降解技术是近年来出现的一种先进的水处理技术，能破坏有机污染物，没有二次污染，能耗和原材料消耗低，工艺简单，因而是一种很有前途的水处理方法。目前，对这种方法的理论和实验研究是水处理方面的热门课题，但是直接利用纳米光催化剂容易在污水中团聚而降低其活性且不利于回收利用。将光催化剂负载在无机矿物表面，制备一定形状的滤料，不仅提高了光催化材料的活性，也有利于回收再利用。本文针对光催化技术在实际应用中存在的光催化剂的固定与活性之间的矛盾这一问题，利用酸性溶胶法制备了纳米TiO_2／粘土复合光催化剂，并考察了制备条件对其物理结构与光催化效能的影响；在此基础上，研究了光催化降解有机污染物甲基橙的能力。
单纯的纳米TiO_2在废水处理中由于部分颗粒团聚，降低降解效率，部分悬浮在水溶液中，难以回收而造成二次污染。纳米TiO_2／粘土复合光催化剂是将TiO_2固定在粘土矿物的表面形成纳米薄层或分散均匀的TiO_2纳米晶体。该矿物复合材料兼具多孔性、高比表面积、光活性和容易回收反复利用等特性。本文对纳米TiO_2／粘土复合光催化剂的酸性溶胶合成、表征及其光催化活性进行了一系列的研究。X射线衍射(XRD)测试表明，多次涂覆TiO_2高岭土表面形成了TiO_2膜，但是其晶形不好，近似于无定形TiO_2；红外光谱(IR)分析发现，Si—O—Si发生了偏移，但是没有Si—O—Ti形成；进一步的高分辨率透射电镜分析研究发现，在涂覆一次的复合材料中的大部分高岭石表面未被TiO_2覆盖，只有少部分高岭石的表面被TiO_2纳米颗粒覆盖。TiO_2纳米颗粒主要吸附在高岭石的边缘和棱角处；随着涂覆次数的增加，有更多由纳米TiO_2颗粒形成的结晶聚合体，大部分还是附着在高岭石表面，不仅在其端面及边缘处，而且在高岭石表面上也出现了TiO_2结晶聚合体；经过四次涂覆的高岭土／纳米TiO_2复合材料，TiO_2纳米颗粒结晶聚合体有些不与高岭石颗粒相连，但大部分附着在高岭石的表面和端面。其中一些高岭石的结构发生破坏，有一部分Al溶出。TiO_2纳米颗粒在高岭石端面的吸附情况较好，可以看出其吸附层的厚度明显增大。
本研究制备的纳米TiO_2／粘土复合光催化剂降解甲基橙效果比较显著，通过影响因素的研究，得到在pH=2，甲基橙浓度为20mg／L，催化剂使用量为5g／L时对甲基橙有最好的降解效果，其平均回收率达到92％，有助于进一步探索提高光催化氧化反应效率的方法与途径，对实际的废水处理也有很好的指导意义。
Photocatalytic degradation method is an advanced waste -water treatment technique. It can degrade organic pollutants entirely and without secondary pollution. It does not need other materials except for ultraviolet light so that energy and materials consumption can be decreased. And the technological process is simple. So it is a prospective wastewater treatment technique. During the past years, the semiconductor photocatalytic process has been applied more and more in wastewater treatment, new energy exploitation, air purification and organic synthesis. Lots of researchers have proved that a great deal of the most organic pollutants can be destroyed by photocatalytic degradation technique. Now, the research of theory and practice about this technique is becoming one of important advanced tasks in environment engineering. In this paper, the active nanoscale TiO2/kaolin composite photocatalyst was synthesized and characterized. The effects of preparing conditions such as calcination temperature on the physica
l characteristics and the photoactivity were investigated. Moreover, the photodegradation of MO was also discussed in detail.
Nano titanium dioxide suspension in the liquid when treating waste water can not be recovered easily, leading to secondary pollution. TiO2/clay nanocomposite is characted as cellularity and superficial, and can be exploited repeatedly and economically when it takes the form of the bulky grain. In this paper, was carried out research on the preparation nanocomposite by the acid-catalyzed sol method of TiO2, and something about the photocatalysis of TiO2. X-ray diffraction tells us that on the surface of kaolin film has formed but it's crystal form is not good. Through infra-red spectum, we know that the band of Si - O- Si has shifted but we do not find Si - O - Ti band. By high resolution transimission electron microscope, we only find TiO2 on the base surface of a small part of kaolin. Nano titanium dioxide is adsorpted on the edge and edge angle of kaolin mainly. More and more TiO2 form aggregates, some of which have not been adsorpted on the kaolin, but the most have adsorpted on the surface of kaolin, not
only on the side and edge, but also on the base plate. In the TiCVkaolin nanocomposite which coated with TiO2 4 times, some of the TiO2 aggregates do not attach to the surface
of kaolin. Some of the kaolin's structure have been damaged and some of the Al has dissolved.
The nano titanium dioxide composite which has been produced by us can degrade methyl orange effectively. Through the research of influencing factors, we know that TiO2 has the optimum degradation effect when pH is 2, the concentration of methyl orange is 20mg/L and the addition of photocatalyst is 5g/L. These results help us to find the way to improve the efficiency of the photocatalytic reactions.
单纯的纳米TiO_2在废水处理中由于部分颗粒团聚，降低降解效率，部分悬浮在水溶液中，难以回收而造成二次污染。纳米TiO_2／粘土复合光催化剂是将TiO_2固定在粘土矿物的表面形成纳米薄层或分散均匀的TiO_2纳米晶体。该矿物复合材料兼具多孔性、高比表面积、光活性和容易回收反复利用等特性。本文对纳米TiO_2／粘土复合光催化剂的酸性溶胶合成、表征及其光催化活性进行了一系列的研究。X射线衍射(XRD)测试表明，多次涂覆TiO_2高岭土表面形成了TiO_2膜，但是其晶形不好，近似于无定形TiO_2；红外光谱(IR)分析发现，Si—O—Si发生了偏移，但是没有Si—O—Ti形成；进一步的高分辨率透射电镜分析研究发现，在涂覆一次的复合材料中的大部分高岭石表面未被TiO_2覆盖，只有少部分高岭石的表面被TiO_2纳米颗粒覆盖。TiO_2纳米颗粒主要吸附在高岭石的边缘和棱角处；随着涂覆次数的增加，有更多由纳米TiO_2颗粒形成的结晶聚合体，大部分还是附着在高岭石表面，不仅在其端面及边缘处，而且在高岭石表面上也出现了TiO_2结晶聚合体；经过四次涂覆的高岭土／纳米TiO_2复合材料，TiO_2纳米颗粒结晶聚合体有些不与高岭石颗粒相连，但大部分附着在高岭石的表面和端面。其中一些高岭石的结构发生破坏，有一部分Al溶出。TiO_2纳米颗粒在高岭石端面的吸附情况较好，可以看出其吸附层的厚度明显增大。
本研究制备的纳米TiO_2／粘土复合光催化剂降解甲基橙效果比较显著，通过影响因素的研究，得到在pH=2，甲基橙浓度为20mg／L，催化剂使用量为5g／L时对甲基橙有最好的降解效果，其平均回收率达到92％，有助于进一步探索提高光催化氧化反应效率的方法与途径，对实际的废水处理也有很好的指导意义。
Photocatalytic degradation method is an advanced waste -water treatment technique. It can degrade organic pollutants entirely and without secondary pollution. It does not need other materials except for ultraviolet light so that energy and materials consumption can be decreased. And the technological process is simple. So it is a prospective wastewater treatment technique. During the past years, the semiconductor photocatalytic process has been applied more and more in wastewater treatment, new energy exploitation, air purification and organic synthesis. Lots of researchers have proved that a great deal of the most organic pollutants can be destroyed by photocatalytic degradation technique. Now, the research of theory and practice about this technique is becoming one of important advanced tasks in environment engineering. In this paper, the active nanoscale TiO2/kaolin composite photocatalyst was synthesized and characterized. The effects of preparing conditions such as calcination temperature on the physica
l characteristics and the photoactivity were investigated. Moreover, the photodegradation of MO was also discussed in detail.
Nano titanium dioxide suspension in the liquid when treating waste water can not be recovered easily, leading to secondary pollution. TiO2/clay nanocomposite is characted as cellularity and superficial, and can be exploited repeatedly and economically when it takes the form of the bulky grain. In this paper, was carried out research on the preparation nanocomposite by the acid-catalyzed sol method of TiO2, and something about the photocatalysis of TiO2. X-ray diffraction tells us that on the surface of kaolin film has formed but it's crystal form is not good. Through infra-red spectum, we know that the band of Si - O- Si has shifted but we do not find Si - O - Ti band. By high resolution transimission electron microscope, we only find TiO2 on the base surface of a small part of kaolin. Nano titanium dioxide is adsorpted on the edge and edge angle of kaolin mainly. More and more TiO2 form aggregates, some of which have not been adsorpted on the kaolin, but the most have adsorpted on the surface of kaolin, not
only on the side and edge, but also on the base plate. In the TiCVkaolin nanocomposite which coated with TiO2 4 times, some of the TiO2 aggregates do not attach to the surface
of kaolin. Some of the kaolin's structure have been damaged and some of the Al has dissolved.
The nano titanium dioxide composite which has been produced by us can degrade methyl orange effectively. Through the research of influencing factors, we know that TiO2 has the optimum degradation effect when pH is 2, the concentration of methyl orange is 20mg/L and the addition of photocatalyst is 5g/L. These results help us to find the way to improve the efficiency of the photocatalytic reactions.
引文
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[6] 邢核，王怡中．多相光催化水处理技术发展过程中反应器研究的现状及发展趋势[J]．环境科学，2001，22(4)：123-127
[7] 王有乐，张庆芳．提高废水处理中TiO_2光催化活性途径的探讨[J]．工业水处理，2001，21(12)：5-8
[8] 王连生．有机污染物化学[M]．科学出版社，1990
[9] Kirilll, Zamaracv. Studies in Surface Science and Catalysis[J]. 1996, 101: 35～50
[10] MartinST, HerrmannH. Trans Taraday Soc [J]. 1994, 90: 3315-3323
[11] 张立德，牟季美．纳米材料学[M]．辽宁科学出版社，1994
[12] 符小荣，宋世庚．感光科学与光化学(J]，1997，15(3)：234
[13] Sauer M L, Ollis D F. Acetone Oxidation in a Photocatalytic Monolith Reactor [J]. Catal, 1994, 149: 81-91
[14] LuMC, Roam GD, Chen J Netal. Factors affecting the photocatalytic degradation of dichlorvos over titanium dioxide supported on glass[J]. Photochem, 1993, 76: 103-110
[15] 贺飞，唐怀军，赵文宽等．纳米TiO_2光催化剂负载技术的研究[J]．环境污染治理技术与设备，2001，2(2)：47-58
[16] LiuXS, lukk, Thomas J K. Encapsulation of TiO_2 in zeolite Y[J]. Chem. Phys. Lett, 1992, 195: 163-168
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