磁性介孔氧化硅复合材料的功能化制备及应用

发布时间：2018-01-24 16:52

  本文关键词： 介孔材料 磁性核壳结构 功能化 光催化 吸附　出处：《西安建筑科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：工业废水的大量排放,使得环境压力越来越大。其中冶金工业中的重金属废水和染料废水的污染尤为严重。由于传统的物理法、化学法和生物法处理废水存在成本昂贵、二次污染和出水难以达到国家排放标准的问题。所以亟待寻找新型的废水处理办法,近年来以介孔氧化硅作为载体的吸附剂或光催化剂的功能材料,被广泛运用于重金属吸附和光催化领域。但是如何高效的利用介孔材料发达的孔道结构和光催化剂(TiO_2)仍然困扰着人们。故而研发可回收的、利用率高的介孔氧化硅吸附剂或光催化剂是目前热点的研究课题。本文采用溶剂热法制备了纳米四氧化三铁微球,采用改进St?ber法制备了核壳结构的磁性介孔氧化硅材料。通过扫描电镜(SEM)和透射电镜(TEM)对材料的形貌特征进行表征分析,发现可以改变正硅酸乙酯(TEOS)的添加量,可以得到不同尺寸介孔二氧化硅壳层。合成磁性介孔氧化硅的最佳的制备条件为:0.15g Fe_3O_4、0.45mL正硅酸乙酯(TEOS),醇水比(V:V)为3:4,0.6g十六烷基三甲基溴化铵(CTAB),反应时间12h。此时制备的磁性介孔氧化硅分散性良好,具备很好的核壳结构,磁饱和强度在30.97emu·g~(-1)。在磁性介孔氧化硅基础上采用浸渍法制备了“磁核-介孔硅-半导体”三元体系光催化剂,研究了负载不同量TiO_2的光催化剂降解亚甲基蓝的性能,发现钛酸四丁酯(TBOT)的添加量为2.5mL的Fe_3O_4@SiO_2@mSiO_2@TiO_2光催化剂催化效率最高。研究发现是由于磁性介孔氧化硅特殊的孔道结构,使得二氧化钛在结晶时被限制,在特殊的孔道内部生长为纳米颗粒,纳米尺寸的二氧化钛结构使得光生空穴-电子对的复合概率降低,从而提高了光生载流子浓度,进一步提高其光催化性能。通过研究不同pH和温度下复合光催化剂降解亚甲基蓝,得出在25℃,pH=7时,复合光催化剂降解效率最高。为了进一步探究磁性介孔氧化硅的吸附性能,我们在磁性介孔氧化硅基础上合成了氨基化修饰的磁性介孔氧化硅复合材料。通过N_2吸脱附测试,得到氨基功能化的磁性核壳微球的比表面积和孔容分别为413.46 m2·g~(-1)和0.21 cm~3·g~(-1)。氨基功能化磁性介孔氧化硅吸附Cr(Ⅵ)的过程中以准二级动力学模型为主,其吸附Cr(Ⅵ)的机理是溶液中离子形态的Cr(Ⅵ)与氨基化修饰的磁性介孔氧化硅复合材料表面的氨基通过电子共用或静电作用实现的。
[Abstract]:The heavy metal and dyestuff wastewater in metallurgical industry are especially polluted because of the traditional physical method. The treatment of wastewater by chemical and biological methods is expensive, the secondary pollution and effluent are difficult to meet the national discharge standards, so it is urgent to find a new treatment method of wastewater. In recent years, mesoporous silica as a carrier adsorbent or photocatalyst functional materials. It is widely used in the field of heavy metal adsorption and photocatalysis. However, how to efficiently utilize the developed pore structure of mesoporous materials and photocatalyst TiO2 still puzzles people. Mesoporous silica adsorbent or photocatalyst with high utilization rate is a hot research topic at present. In this paper, nano-sized ferric trioxide microspheres were prepared by solvothermal method, and modified St3 microspheres were used. Magnetic mesoporous silica materials with core-shell structure were prepared by ber method. The morphologies of the materials were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the addition of tetraethyl orthosilicate (TEOS) could be changed. The mesoporous silica shell with different sizes can be obtained. The optimum preparation conditions for the synthesis of magnetic mesoporous silica are as follows: 0.15g Fe3O-1, 0.45ml tetraethyl orthosilicate (TEOS). The ratio of alcohol to water (V: v) is 3: 4 0. 6 g cetyltrimethylammonium bromide (CTABN), and the reaction time is 12 h. The magnetic mesoporous silicon oxide has good dispersion and good core-shell structure. The magnetic saturation intensity is 30.97 emu 路g ~ (-1). On the basis of magnetic mesoporous silicon oxide, a ternary system of "magnetic nucleus-mesoporous silicon-semiconductor" photocatalyst is prepared by impregnation method. The degradation of methylene blue with different amount of TiO_2 photocatalyst was studied. It was found that tetrabutyl titanate (TBOT). The addition of 2.5 mL Fe_3O_4@SiO_2@mSiO_2@TiO_2 photocatalyst has the highest catalytic efficiency. It is found that the special pore structure of magnetic mesoporous silicon oxide is the main reason. The TIO _ 2 is limited in crystallization and grows into nanocrystalline particles in a special pore. The nano-sized TIO _ 2 structure reduces the recombination probability of photogenerated hole-electron pairs. Therefore, the photocatalytic activity was further improved by increasing the concentration of photogenerated carriers. By studying the degradation of methylene blue by the composite photocatalyst at different pH and temperature, it was found that pH = 7:00 at 25 鈩，

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