水中溶解有机物TiO_2-UV-O_2光催化氧化动力学研究

本文对水中溶解有机物TiO2 -UV -O2 光催化氧化反应的动力学研究进行了综述。许多研究结果都证实了一些因素 ,如有机物初始浓度、氧分压 (或溶解氧浓度 )、紫外线波长和强度、pH值、温度和TiO2 浓度等 ,对反应速度有影响。尽管该反应的复杂性使不同研究得到的动力学参数存在不一致 ,但此研究对指导操作工艺条件的优化和反应器构型的设计有一定作用。     

B2O3·TiO2/Ti催化剂对水中腐殖酸吸附行为研究

TiO2光电催化氧化有机物的反应被认为是表面反应,有机物在TiO2表面的吸附是其降解的先决条件,因此系统研究有机物在TiO2表面的吸附行为,可以为进一步的光电催化降解提供实验依据.现采用阳极氧化法在基体钛表面原位合成B2O3·TiO2/Ti催化剂为吸附剂,系统地研究了腐殖酸在膜催化剂上的吸附行为,探讨了温度、溶液pH值、腐殖酸初始浓度、外加偏压等因素对吸附的影响,结果表明:低温、酸性条件下有利于腐殖酸在膜催化剂上吸附,吸附量随初始浓度、外加偏压的增加而增大,B2O3·TiO2/Ti催化剂吸附腐殖酸的等温线数据可用Freundlich等温吸附方程描述,吸附过程遵循Lagergren二级吸附动力学模型.     

纳米级SO4^2—／TiO2固体超强酸的红外光谱及催化活性

用不同晶型的纳米TiO2制备出纳米级SO4^2-/TiO2固体超强酸，利用红外光谱研究了TiO2晶型，硫酸浓度及焙烧温度对SO4^2-/TiO2固体超强酸的影响。制备SO4^2-/TiO2的最优条件是：锐钛型TiO2,c(H2SO4)=1.0mol/L的硫酸浸泡，450℃焙烧，此时其红外光谱的特征吸收峰最强，催化乙酸和丁醇酯化反应可使酯化率达到98.4%。     

纳米TiO2光催化降解有机物的机理及其影响因素的研究

对纳米TiO2光催化降解水中有机物的机理进行了研究，并对溴苯酚降解为目标反应，系统分析了紫外光强度、TiO2浓度、温度、溶液的pH值以及杂质等对光催化降解为溴苯酚程度的影响。优化这些因素可以提高纳米TiO2光催化降解率。     

SO4^2—／TiO2—MoO3催化合成异丁醛1，2—丙二醇缩醛

以固体超强酸SO4^2—／TiO2-MoO3为催化剂，对以异丁醛(Ⅱ)和1，2-丙二醇(Ⅲ)为原料合成异丁醛1，2—丙二醇缩醛(I)的反应条件进行了研究。实验表明：SO4^2—／TiO2-MoO3是合成异丁醛1，2-丙二醇缩醛的良好催化剂，较系统地研究了醛醇摩尔比、催化剂用量、反应时间诸因素对收率的影响。最佳反应条件为：n(异丁醛)：n(1，2-丙二醇)＝1：1．3，催化剂用量为反应物料总质量的1．0％，环己烷为带水剂，反应时间1．0h。上述条件下，异丁醛1，2—丙二醇缩醛的收率可达82．5％。     

天然沸石负载TiO2光催化降解双酚A的研究

以沸石负载TiO2为催化剂,对光催化降解环境内分泌干扰物双酚A（BPA）进行了研究。阐述了沸石负载TiO2的制备过程,研究了溶液的催化剂投加量、初始浓度、pH值、不同试验条件、负载次数、外加氧化剂H2O2对降解效率的影响,并对降解过程的反应动力学进行了探讨,结果表明沸石负载TiO2对BPA有较好的光降解效果,且光降解反应符合一级反应动力学规律。     

SO2-4/TiO2光催化降解邻硝基苯酚

采用硫酸溶液浸渍处理TiO2制得SO2-4/TiO2光催化剂.考察了光催化剂对邻硝基苯酚溶液的光催化行为.发现SO2-4/TiO2的光催化活性高于TiO2,浸渍液中H2SO4的浓度和催化剂的焙烧温度对SO2-4/TiO2的催化活性有一定的影响,H2SO4溶液的最佳浓度为0.5 mol·L-1,最佳焙烧温度为500℃.催化降解过程符合一级反应动力学规律.     

SO4^2-／TiO2光催化降解邻硝基苯酚

采用硫酸溶液浸渍处理TiO2制得SO2-4/TiO2光催化剂.考察了光催化剂对邻硝基苯酚溶液的光催化行为.发现SO2-4/TiO2的光催化活性高于TiO2,浸渍液中H2SO4的浓度和催化剂的焙烧温度对SO2-4/TiO2的催化活性有一定的影响,H2SO4溶液的最佳浓度为0.5 mol·L-1,最佳焙烧温度为500℃.催化降解过程符合一级反应动力学规律.     

B2O3-TiO2-Mg-C体系燃烧反应热力学与产物结构变化过程研究

对B2O3-TiO2-Mg-C体系的燃烧反应热力学进行了研究，结果表明，该体系化学反应机理为:Mg先还原B2O3和TiO2，新生的Ti与B的C反应生成TiB2和TiC；TiO2的还原经历了TiO2→Ti3O2→TiO→Ti2O→Ti的逐步过程，对燃烧合成的产物结构形成机理进行了研究，表明当燃烧区的能量传到预反应区时，B2O3首先熔化并均匀地包裹在Mg,TiO2和C周围，Mg熔化后通过扩散与B2O3和TiO2反应，随着预反应区温升的升高，B2O3与Mg作用还原出B，TiO2与Mg作用还原出Ti，然后Ti与B或C反应形成TiB2或TiC晶核，最后TiB2与TiC及MgO在持续高温下长大。     

可见光下TiO2还原Cr(Ⅵ)光催化反应研究

Cr(Ⅵ)是一种对生态环境和人类健康有极大危害的重金属离子,为研究可见光下TiO2还原Cr(Ⅵ)的光催化反应,首先使用溶胶-凝胶法制备TiO2光催化剂,并对其结构进行表征;然后在可见光下研究其还原Cr(Ⅵ)光催化反应;最后分析光催化反应机理及反应动力学。结果表明,制备的TiO2为锐钛矿,直径约为400~500 nm,禁带宽度为3.2 eV;在最佳条件(Cr(Ⅵ)初始浓度为1.00 mg/L,TiO2投加量为2.00 g/L,pH为4.00,甲醇浓度为0.10 mol/L)下反应150 min,TiO2还原Cr(Ⅵ)可见光催化效率可高达100%;可见光下TiO2催化反应机理为:HCrO4^-吸附在TiO2表面,形成一种具有可见光响应的HCrO4^-/TiO2复合催化剂;TiO2还原Cr(Ⅵ)光催化反应符合假一级反应动力学,反应速率常数为0.0058 min^-1。     

Crystallization of zeolite L from Na2O-K2O-Al2O3-SiO2-H2O system

Zeolite L powder was prepared from the substrate mixture of Na₂O-K₂O-Al₂O₃-SiO₂-H₂O system at temperatures of 373-443 K. In order to investigate the factors which influence the synthesis outcome, a reference system which yields zeolite L in a reproducible manner was chosen and subjected to controlled changes in synthesis parameters. The crystalline zeolite L samples obtained were characterized by elemental chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was established that phase purity, morphology, and the size of crystals of crystalline product were affected by molar ratios of the substrate, such as SiO₂/Al₂O₃, (K₂O+Na₂O)/SiO₂, Na₂O/(K₂O+Na₂O), and H₂O/(K₂O+Na₂O). Amorphous silica powder (Zeosil) was the preferred silica source, and the crystallization rate was promoted by introducing gel aging, seeding, and rapid heating rate.     

Photocatalytic activity of Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions

Cu₂O/TiO₂, Bi₂O₃/TiO₂ and ZnMn₂O₄/TiO₂ heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu₂O, Bi₂O₃ and ZnMn₂O₄ are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu₂O/TiO₂ and Bi₂O₃/TiO₂ by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed.     

碳酸钠—过氧化氢—水体系相图的绘制

进行了Na2CO3-H2O2-H2O体系溶解度的测定并绘制成相图,最后对其应用进行了讨论。     

Synthesis and characterization of Y2O3-ZrO2 and Y2O3-CeO2-ZrO2 precursor powders

Thixotropic gels of the precursor powders of the titled compounds have been prepared by the addition of oxalic acid to the mixed solutions of metal salts at room temperature (≈ 27 °C). The clear sols of yttrium-zirconyl oxalate (YZO) and yttrium-cerium-zirconyl oxalate (YCZO) gelled within a few hours and were oven-dried at 40 °C. The various stages of gelation behaviour of the sols are explained on the basis of DLVO theory. By repeptizing the dried gel powders with water, concentrated sols were prepared. The gelation time as a function of chloride ion concentration is discussed for both sols. The nature of the temperature dependence of the dried gel powders was studied by means of thermogravimetric analysis and differential thermal analysis. Powder X-ray diffraction was used to study the crystallization behaviour of the dried amorphous gel powders. It is found that these powders crystallize in tetragonal phase when calcined at 850 °C for 1 h. Estimation of surface area and infra-red characterization have also been carried out for the prepared powders.     

Preparation and characterization of Cr2O3-TiO2-Al2O3-V2O5 green pigment

Green pigments with high near infrared reflectance based on a Cr₂O₃-TiO₂-Al₂O₃-V₂O₅ composition have been synthesized. Cr₂O₃ was used as the host component and mixtures of TiO₂, Al₂O₃ and V₂O₅ were used as the guest components. TiO₂, Al₂O₃, and V₂O₅ were mixed into 39 different compositions. The spectral reflectance and the distribution of pigment powder were determined using a spectrophotometer and a scanning electron microscope, respectively. It was found that a pigment powder sample S9 with a Cr₂O₃-TiO₂-Al₂O₃-V₂O₅ composition of 80, 4, 14 and 2 wt%, respectively, gives a maximum near infrared solar reflectance of 82.8% compared with 49.0% for pure Cr₂O₃. The dispersion of pigment powders in a ceramic glaze was also studied. The results show that the pigment powder sample S9 is suitable for use as a coating material for ceramic-based roofs.     

Al2O3-SiO2-TiO2一ZrO2复合陶瓷膜的制备与表征

采用Sol—Gel法制备出掺杂SiO2，TiO2及ZrO2改性的γ-Al2O3膜，并通过SEM，EPMA，AFM等测试手段对膜结构和性能进行表征。探讨了制膜工艺条件对膜性能及结构的影响。制备的Al2O3复合膜膜厚为1—2μm，结构均匀无缺陷。     

Crystal Structure of the LiNaZnP2O7 Compound in the Li2ZnP2O7-Na2ZnP2O7 Glass-Forming System

The crystal structure of the LiNaZnP₂O₇ compound is determined using X-ray powder diffraction (space group Cmcm, a = 12.431 Å, b = 7.589 Å, c = 6.283 Å). The structure has a mixed tetrahedral framework consisting of the diortho groups [P₂O₇] and the tetrahedra [ZnO₄] and [LiO₄], which are joined into chains. The [ZnO₄] and [LiO₄] tetrahedra are distributed in the chains in a random manner, because the zinc and lithium atoms statistically occupy one crystallographic position. The sodium cations are arranged in channels of the tetrahedral framework. The atomic coordinates and interatomic distances in the structure are reported. Original Russian Text Copyright ? 2005 by Fizika i Khimiya Stekla, Shepelev, Lapshin, Petrova, Novikova.     

Stable Ti/RuO2-Sb2O5-SnO2 electrodes for O2 evolution

RuO₂-based electrodes are generally known to be unstable for O₂ evolution. In this paper, a stable type of RuO₂-based electrode, Ti/RuO₂-Sb₂O₅-SnO₂, is demonstrated for O₂ evolution. In the ternary oxide coating, RuO₂ serves as the catalyst, SnO₂ as the dispersing agent, and Sb₂O₅ as the dopant. The accelerated life test showed that the Ti/RuO₂-Sb₂O₅-SnO₂ electrode containing 12.2 molar percent of RuO₂ nominally in the coating had a service life of 307 h in 3 M H₂SO₄ solution under a current density of 0.5 A cm⁻² at 25 °C, which is more than 15 times longer than other types of RuO₂-based electrodes. Instrumental analysis indicated that RuO₂-Sb₂O₅-SnO₂ was a solid solution with a compact structure, which contributed to the stable nature of the electrode.     

Investigation of the crystallization of zeolites in the SiO2-Al2O3-Na2O-K2O-(TEA)2O-H2O system

The crystallization of zeolites in the SiO₂-Al₂O₃-Na₂O-K₂O-(TEA)₂O-H₂O system, where (TEA)₂O is tetraethylammonium oxide, has been investigated over a wide range of variations in the SiO₂: Al₂O₃ ratio (from 5 to 19). It has been found that, in the composition region under investigation, zeolites crystallize with structures of paulingite, beta, phillipsite, merlinoite, erionite, mordenite, and garronite. The formation of the aforementioned phases is determined by the composition of the initial gels and the synthesis temperature. The cocrystallization of paulingite, phillipsite, and merlinoite is explained by the structural features of these zeolites.