【作者】 邓培昌；

【导师】 王海增；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2009， 博士

【摘要】 半导体TiO₂可有效降解环境中难生物降解的有机污染物。本文采用水热法、利用廉价原料,制备了纯TiO₂、卤族元素（ F、Cl、Br、I ）掺杂TiO₂ （HDT）,并以硅胶为载体、利用水热原位负载法制备了硅胶负载卤族元素掺杂TiO₂ （HDTS）。运用X射线粉末衍射（XRD）表征了催化剂的晶相组成、X射线光电子能谱（XPS）和X射线荧光光谱（XRF）测定了催化剂的元素组成、低温氮吸附（BET）测定了催化剂比表面积和孔结构、电子透射电镜（TEM）观察了催化剂的形貌结构,最后通过紫外-可见漫反射吸收光谱（UV-Vis DRS）测定了催化剂的吸光特性。以苯酚为模型污染物考察了催化剂的光催化性能,研究不同的制备条件对光催化性能的影响,筛选出最佳催化剂。以硫酸钛为钛源,含卤盐为卤源,去离子水为溶剂,制备HDT纳米粒子。制备工艺参数对其光催化活性影响较大,其影响主要为卤盐加入量、煅烧温度。卤族元素的掺杂可促进锐钛矿相TiO₂的生成、抑制其向金红石相的转化,拓宽TiO₂的光吸收范围。适量F、Cl、Br、I的掺杂可提高TiO₂的光催化活性,最佳掺杂量nx/nTi分别为0.30、0.15、0.40、1.00。煅烧温度可影响催化剂的晶粒尺寸、晶型、光吸收特性、晶格畸变和膨胀程度以及掺杂离子进入TiO₂晶格的能力,从而对掺杂纳米TiO₂的光催化性能产生影响。F、Cl、Br、I掺杂TiO₂的最佳煅烧温度依次为80℃、750℃、700℃、340℃。I掺杂TiO₂在低于340℃的煅烧条件下,在紫外部分具有强烈的吸收、从而体现很好的光催化活性;在340℃的煅烧条件下,I掺杂TiO₂形成紫色的TiO₂包裹碘单质纳米颗粒,该催化剂在可见光范围具有强烈的吸收、并且呈现很高的可见光光催化活性。HDT经硅胶负载后,在保持纳米光催化剂光催化活性的前提下,形成了较大的颗粒,使催化剂易于分离;硅胶进一步促进锐钛矿相TiO₂的生成、抑制其向金红石相TiO₂的转化,抑制TiO₂晶粒的长大,增强催化剂的热稳定性;除此之外,一定量硅胶的加入还可以改变催化剂的吸光特性,增强可见光范围的吸收。HDT经硅胶负载后,比表面积增大、吸附能力增强。由于吸附和光催化的双重作用,可使有机污染物快速降解。通过对甲基橙的光催化降解,比较了催化剂光催化活性的强弱、研究了光催化降解规律。所制备的光催化剂,在无光照条件下、均无活性。在全谱光源照射下,按FTi（30）080→ClTi（15）750→BrTi（40）700→ITi（100）340→ITi（100）080的顺序对甲基橙的降解活性递增。经硅胶负载后、活性顺序没有变化,光催化活性都有大幅提高。HDT降解甲基橙时,呈典型的零级反应动力学特征。表观速率常数K与甲基橙初始浓度有关。除了ITi（100）080和ITiSi（100）080-2在较宽的pH值范围内具有较强光催化活性,其它各催化剂都在pH为3和7时、体现较高的催化活性,当pH为其它值时、催化活性下降明显。通过对海水中苯酚的降解,考察了催化剂的在海水环境中的活性。除了ITi（100）340和ITiSi（100）340-2仍保持较高的催化活性外,P-25和制备的其它光催化剂的光催化活性都很差,HDTS的催化活性皆弱于对应的HDT的催化活性。更多还原

【Abstract】 Semiconductor TiO₂ can degrade organic pollutants in environment efficiently, which is difficult to be degraded by biologic methods. In the current work, pure TiO₂, halogen elements （F, Cl, Br and I）doped TiO₂ （HDT） were prepared by hydrothermal method, using cheapness stuff. Halogen elements doped TiO₂ supported on SiO₂ （HDTS） were prepared by in situ hydrothermal method. The crystal phase composition of catalysts was studied by using the X-ray powder diffraction （XRD）. The elements component of catalysts was mensurated by using the X-ray photoelectron spectroscopy （XPS） and the X-ray fluorescence spectrometry （XRF）. The surface area and pore structure was studied by using BET. The morphology was observed by using TEM. The optical absorbance performance of catalysts was studied by using the UV - visible diffuse reflectance absorption spectra （UV-Vis DRS）. The photocatalytic degradation of phenol is used as model reaction to evaluate the photocatalytic activity of the photocatalysts. The effects of preparation and reaction conditions on the photocatalytic performances are studied.The HDT was prepared through a mild hydrothermal route, using Ti（SO₄）₂ as the precursor, containing halogen salt as the halogen source and deionized water as solvent. The photocatalytic activity of samples was influenced greatly by processing parameter. The influence factors were mainly the volume of containing halogen salt and the calcination temperature. Halogen elements, which were doped in TiO₂, can promote anatase phase formation, can inhibit anatase to rutile phase, can broaden the scope of TiO₂ optical absorption. When the amounts of the doping F, Cl, Br and I were moderate, halogen elements can enhance photocatalytic activity of TiO₂. The best doping amounts of F, Cl, Br and I were 30.0%, 15.0%, 40.0% and 100.0%, respectively. Calcined temperature could influence crystal size, phase transformation, light absorption property, distortion and expansion degree of crystal lattice and the ability of doped ions entering into lattice TiO₂, and then influenced the photocatalytic activity of TiO₂. The best calcination temperatures of F-doping, Cl-doping, Br-doping and I-doping TiO₂, were 80℃, 750℃, 700℃and 340℃, respectively.Before calcination at 340℃, the white I-doping TiO₂ showed a much better photocatalytic activity under full-spectrum light irradiation for its drastic photoabsorption in the range of wavelengths from 200 to 325 nm. After calcination at 340℃for two hours, the white I-doping changed into the purple nanoparticles, which were （I2）n encapsulated inside TiO₂. The purple nanoparticles exhibited an obvious photocatalytic activity under visible light illumination for its strong absorption in the range of wavelengths from 384 to 700 nm.HDTS was synthesized by a mild and easy hydrothermal route using Ti（SO4）2, containing halogen salt and commercial silica material. Besides the benefit of nanoparticles catalytic activity enhancement, HDTS can be separated from the suspension solution easier than TiO₂ nanoparticles. The SiO₂ can promote anatase phase formation, inhibit the transformation of anatase to rutile phase, inhibit the growth of TiO₂ nanoparticles, and then enhance the thermal stability of the catalyst. In addition, adding a certain amount of SiO₂ can also change the light absorption property of the photocatalysis, enhance the absorption of visible-light range. The surface area of HDT that is supported by SiO₂ is improved significantly, and then their absorption capacity is enhanced. Organic pollutants could be degraded fleetly because of the dual function of adsorption and photocatalysis.Then research on the process of photocatalytic decomposition of methylene orange, the activity of photocatalysis was compared and the law of photocatalytic decomposition was studied. The results of vacancy study and dark study show that the photocatalysis are noneffective. Under full-spectrum light irradiation, according to the order of FTi（30）080→ClTi（15）750→BrTi（40）700→ITi（100）340→ITi（100）080, the activities of the photocatalysis to decomposed methylene orange are more and more efficient. After silica gel loading, the order of activity does not change, but the activity is enlarged. When the HDT decomposed methylene orange, the model of the reaction is zero order dynamics characteristic. The speed constant K, which is apparent, concerns on the initial concentration of methyl orange. ITi（100）080 and ITiSi（100）080-2 have the better activity in a wide pH value scope. When the pH value is 3 or 7, the other photocatalysis have the best activity. Researching on the process of photocatalytic decomposition of phenol in seawater, the photocatalysis compatibility is inspected. ITi（100）340 and ITiSi（100）340-2 still maintained their high activity, but the other photocatalysis and P-25 did not. The activity of the HDTS is not better than that of HDT.更多还原