Investigation of the photocatalytic activity of TiO2--polyoxometalate systems

The present study reports the investigation of polyoxometalate catalyzed electron transfer from the conduction band of photoexcited TiO2 to molecular oxygen. The oxidation of 1,2-dichlorobenzene (DCB) was used as an index reaction for evaluating the photocatalyst systems TiO2-PW12O40(3-), TiO2-SiW12O40,4- and TiO2-W10O32(4-) in oxygenated aqueous solution. Addition of these polyoxometalate (POM) anions to TiO2 suspensions resulted in significant rate enhancement for DCB oxidation. Photodegradation kinetics exhibited [POM] dependence, experiencing different maximum (k = 0.0318 min(-1), 0.0108 min(-1), and 0.0066 min(-1)) for each POM at different [POM] (0.1 mM PW12O40(3-), 0.07 mM SiW12O40,4- and 1 mM W10O32,4-respectively). The probability that the difference in the adsorption affinity of POMs on TiO2 surface could account for the observed ranking of photodegradation rates was ruled out by adsorption isotherm experiments that revealed similar binding constants for each POM (467 M(-1), 459 M(-1), and 417 M(-1) for PW12O40(3-), SiW12O40(4-), and W10O32(4-), respectively). DCB degradation over TiO2 with O2 or POM+O2 systems can be modeled by the Langmuir-Hinshelwood (saturation kinetics) model. The concentration-independent rate constants (kL-H) for TiO2-O2, TiO2-W10O32(4-), TiO2-SiW12O40(4-), and TiO2-PW12O40(3-) were 0.0818, 0.152, 0.421, and 0.638 min(-1), respectively. An analysis of deltaG for electron transfer from the conduction band of TiO2 to POMs in this study shows that the electron transfer takes place even when it is endothermic.     

TiO2光触媒纺织品抗菌性能的测试标准

简单介绍TiO2光触媒抗菌制品标准的发展和TiO2光触媒纺织品抗菌性能测试原理及方法.通过对GB/T23763-2009、ISO 27447-2009(E)和JIS R 1702-2006进行了比较,指出了各标准存在的问题,提出了采用转移法或转印法的新接种方法.     

Improvement in photocatalytic activity of TiO2 under visible irradiation through addition of N-TiO2

This work is focused on improvement in photocatalytic activity of anatase-TiO2 (a-TiO2) photocatalyst under visible-light irradiation by adding nitrogen-doped TiO2 (N-TiO2) for depression of recombination rate between photoexcited electron and hole. The composites (a-TiO2/N-TiO2) were prepared by grinding in ethanol solvent at 200 rpm for 15 min with change in weight ratio of N-TiO2. In addition to the characterizations by X-ray diffraction and X-ray photoelectron spectroscopy, measurements of existing singlet oxygen by chemiluminescens method and photocatalytic activity by using NO(x) decomposition were conducted. The increases in singlet oxygen and photocatalytic activity have been observed and the phenomena are discussed based on the efficient prevention of recombination between photoexcited electron and hole within the prepared composite.     

Fe3+/TiO2负载型活性炭的制备及其光催化活性的研究

以TiCl4为原料，采用沉淀法制备了Fe^3＋掺杂的TiO2溶胶。研究了溶胶浓度与负载方式对活性炭负载Fe^3＋／TiO2溶胶光催化降解亚甲基蓝的影响。对Fe^3＋／TiO2溶胶进行XRD、UV-Vis的表征显示，该溶胶为纯锐钛矿型TiO2，粒径约为12．6nm。紫外光照射300min，活性炭负载型Fe^3＋／TiO2可降解溶液中80％的亚甲基蓝，且该溶胶可多次回收利用，具有较高的重复利用率和催化降解效率。     

静电纺丝制备WO3-TiO2纳米纤维及其光催化性能研究

采用静电纺丝法制备了WO3掺杂的有机无机PVP/WO3-TiO2纤维,经高温焙烧得到WO3-TiO2纳米纤维.通过DSC-TGA、FT-IR、SEM、XRD和比表面积分析等对样品进行了表征.以模拟印染废水10 mg/L亚甲基蓝溶液为底物,研究了WO3掺杂量和焙烧温度等对亚甲基蓝太阳光催化降解效果的影响.结果表明,WO3掺杂摩尔分数为0.1%,焙烧温度为500℃时,WO3-TiO2纳米纤维的光催化降解效果最好,太阳光照射6 h降解率达到99.5%,重复使用10次降解率仍在97%以上.     

二氧化钛纳米管的制备及其光催化性能

为提高TiO_2的光催化性能,通过电化学阳极氧化法在金属钛箔基体上制备了结构有序的TiO_2纳米管(TiO_2NTs),并以此为基础通过连续离子层吸附反应技术(SILAR)制备了Ag、CdS共修饰的TiO_2纳米管(AgCdS/TiO_2NTs)。采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、元素分析仪和紫外可见漫反射光谱等表征手段,对Ag-CdS/TiO_2NTs形貌结构、元素组成和光吸收特性等进行了表征,并研究了Ag、CdS修饰后的TiO_2纳米管的光催化性能。结果表明:Ag和CdS纳米粒子被成功沉积在TiO_2纳米管上;与纯TiO_2纳米管的吸收光谱相比,Ag-CdS/TiO_2NTs对光的吸收范围延伸到整个可见光区域;与纯TiO_2纳米管或CdS修饰的TiO_2纳米管相比,Ag(3)-CdS/TiO_2NTs对甲基橙脱色率最高,70 min后脱色率达100%。     

尿素氮源掺杂二氧化钛对染料可见光脱色的研究

采用溶胶-凝胶法制备不同尿素氮源掺杂量的光催化剂尿素N/TiO2。尿素氮源掺杂后溶胶平均粒径仍在30-50nm之间,对溶胶粒径影响不大。尿素氮源掺杂可见光区域的吸收强度明显提高,但没有使吸收光波长产生明显的红移。红外谱图表明尿素与TiO2形成新的共价键以此参与钛酸四正丁酯的水解过程。0.01%和0.1%尿素掺杂可以提高催化剂可见光活性,继续增加掺杂量活性反而下降。染液初始浓度提高,催化剂脱色率则下降。0.01%尿素N/TiO2可见光下脱色4mg/L亚甲基蓝溶液,脱色率达92.8%。     

织物负载TiO2光催化剂的制备及其性能

常温条件下采用溶胶-凝胶法制备纳米TiO2溶胶,并采用浸轧→烘干→焙烘工艺施于棉织物上;X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电镜(TEM)等方法对样品结构和形貌进行的分析和表征证明,形成了织物表面负载TiO2薄膜,常温制备的TiO2主要为锐钛矿型,薄膜较均匀地负载在纤维表面.以酸性橙Ⅱ为降解物,模拟废水进行光催化降解,考察了催化剂浓度和溶液pH值对酸性橙Ⅱ的降解效果,结果表明,TiO2浓度为0.441 mol/L,初始染液pH值为3的条件下,酸性橙Ⅱ的降解率最大,可达97.7％,且该光催化材料可循环使用.     

TiO2-based photocatalytic degradation of 2-chlorophenol adsorbed on hydrophobic clay

The combination of adsorption and heterogeneous photocatalysis has been investigated as a promising technology for the removal of organic water pollutants. A laboratory study of the removal and decomposition of 2-chlorophenol (2-CP) as a toxic organic pollutant was carried out under various conditions with an organophilized clay mineral (hexadecylpyridinium chloride-modified montmorillonite; HDPM) as adsorbent and Degussa P25 TiO2 as photocatalyst. Three different oxidation processes leading to the degradation of 2-CP were compared: direct photolysis, heterogeneous photocatalysis in a TiO2 suspension, and the decomposition of substrate adsorbed on HDPM in the presence of TiO2. Both the degradation of 2-CP and the formation of intermediates were analyzed by HPLC, the total organic carbon content and the total organic and inorganic chloride contents were measured to monitor the mineralization process, and X-ray diffraction and thermoanalytical measurements were made to characterize the hydrophobic clay adsorbent. The heterogeneous photocatalytic degradation of dissolved (2-CP/UV/TiO2) and desorbed 2-CP (2-CP/HDPM/UV/TiO2) appeared to be equally efficient, whereas direct photolysis of 2-CP was far less efficient in the oxidative destruction. HDPM proved to be a suitable adsorbent, capable of adsorbing toxic organics from water. It was demonstrated that the adsorbent (at relatively high concentration) did not decrease the rate of mineralization of 2-CP. The results confirmed that the adsorbent retains its structure and composition during the mineralization process, and thus it can be reused without regeneration. The combination of adsorption and heterogeneous photocatalysis studied may be an efficient and economical means of accumulating, removing, and oxidizing organic water contaminants, and its application is in accordance with the growing environmental demands.     

The hydrogen peroxide-assisted photocatalytic degradation of alachlor in TiO2 suspensions

Photocatalytic degradations of alachlor in TiO2 suspensions with and without the use of hydrogen peroxide were studied using two different monochromatic UV irradiations (300 and 350 nm). Direct photolysis of alachlor was a rather slow process, but the addition of TiO2 enhanced the reaction rates by 12 and 26 times using 300 and 350 nm UV irradiation, respectively. The results showed that a low H2O2 dosage in photocatalysis using 300 nm UV would enhance the rates by 3.3 times, but an overdose of H2O2 will retard the rate due to the hydroxyl radicals are consumed. However, this process is impracticable at 350 nm due to the absorption characteristic of H2O2. A neutral initial pH level was found to favor the H2O2 assisted photocatalysis at 300 nm UV illumination. Eleven major intermediates were identified by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and MS/MS. The major degradation mechanisms of H2O2-assisted alachlor photocatalysis include dechlorination, dealkylation, hydroxylation, cyclization, scission of C-O bond, and N-dealkylation. Bell-shaped evolution profiles of different intermediates were observed. Degradation pathways were proposed accordingly to illustrate series of degradation steps. The TOC analysis revealed the different stages of the reaction.     

掺镧TiO_2光催化降解罗丹明B的研究

采用溶胶-凝胶法制备了掺镧TiO2微粒.以罗丹明B为目标降解物,分别在太阳光和紫外灯下照射,考察了掺镧TiO2光催化活性.结果表明:在紫外光下,pH值为6时,用4 g/L掺镧0.25%TiO2降解罗丹明B光催化活性最佳;在太阳光下,pH值为6时,用5 g/L掺镧0.075%TiO2降解罗丹明B光催化活性最佳;加入H2O2都能提高光催化效果,在太阳光下,由于TiO2和H2O2的协同作用,催化降解率能达到90%以上.     

Association of photosynthesis and photocatalytic inhibition of algal growth by TiO2

The relationship of photosynthesis and photocatalytic inhibition of algal growth (Chroococcus sp.) by TiO2 was investigated by an ATP assay under ultraviolet (UV) and fluorescent light (FL) irradiations. The adverse effects of what on Chroococcus sp. growth in the TiO2+FL+UV run are larger than those in the TiO2+UV run. The difference is considered to be caused by oxygen generated by Chroococcus sp. under FL irradiation. A rate equation for the relationship of light irradiation intensity to rate of decrease in the Chroococcus sp. population on the basis of the Langmuir-Hinshelwood model has been proposed. The experimental data are in good agreement with the proposed model. In this study, the optimum FL intensity is 0.51 mW/cm2.     

TiO2光催化降解乳酸反应动力学研究

以TiO2为催化剂,紫外灯为光源,对乳酸的光催化降解进行动力学研究.乳酸降解反应动力学拟合结果表明,降解动力学规律符合Langmuir-Hinshelwood动力学模型,反应速率常数k=0.0085g/(L·min),一级反应动力学模型与实验数据拟合较好,方差R2大于0.99,乳酸初始降解速率r0随乳酸初始浓度增大而增大.     

纳米TiO2光催化氧化降解甲基橙动力学研究

以钛酸四丁酯为前驱体、聚乙二醇为模板剂,用溶胶-凝胶法合成了粒径分布均匀的纳米TiO2;用x射线衍射(XRD)、透射电镜(TEM)等对产物进行了表征.以高压汞灯为光源,研究了甲基橙在TiO2水悬浮液中的降解动力学.结果表明,所制备的纳米TiO2为锐钛型结构,粒径为15～20 nm,分布均匀.甲基橙的光催化降解动力学符合Langmiur-Hinshelwood动力学模型,反应速率常数k=0.43 mg/L·min),表观吸附平衡常数K=0.037 L/mg,其半衰期随着甲基橙初始质量浓度p0的增加而延长.     

Enhanced degradation in nanocomposites of TiO2 and biodegradable polymer

Nanocomposites of titamium dioxide (TiO2) particles and biodegradable poly (butylene succinate) (PBS) were fabricated by melt-blending using a high-shear extruder. TiO2 particles were highly dispersed in the PBS matrix by high-shear processing, and the addition of TiO2 particles into PBS did not decrease its mechanical strength. The photocatalytic decomposition and biodegradable properties of the nanocomposites were evaluated by UV irradiation or enzymatic degradation methods in vitro. It was found that both the esterase enzyme and UV irradiation decomposed the nanocomposites. Photocatalytic decomposition of PBS clearly depended on the size and dispersibility of TiO2 particles in PBS polymer. Higher dispersibility and smaller size of TiO2 particles were effective on the photocatalytic oxidation of PBS. In addition, decomposition rate under a simultaneous UV irradiation treatment and immersion in an enzyme solution was higher than those under UV irradiation or immersion in an enzyme solution. These results indicate that the nanocomposites can easily be decomposed not only by an enzyme in soil or compost, but also by photocatalytic oxidation of TiO2 under sunlight.     

Fe_2O_3/TiO_2异质结的制备及光催化降解性能

结合静电纺丝技术和水热法制备Fe_2O_3/TiO_2异质结光催化材料.利用扫描电镜(SEM)、X射线衍射(XRD)、傅立叶转换红外光谱(FT-IR)及比表面分析等方法,对Fe_2O_3/TiO_2异质结的形貌、晶型、化学组成等进行表征.利用Fe_2O_3/TiO_2材料对罗丹明B(RB)进行光催化降解,结果表明,Fe_2O_3/TiO_2对RB的降解速率高于纯TiO_2纳米纤维,而且掺铁量为0.5%时降解效果最好.     

纳米SnO2/TiO2/MMT制备及其光催化性能

比较不同制备方法制得的复合催化剂,由超临界干燥法制备的光催化剂具有粒径小,分散性好,光催化活性高等特点.以TiCl4为原料,采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级SnO2TiO2/MMT(蒙脱土)复合光催化剂.采用XRD和TEM对样品进行了表征.结果表明:TiO2以锐钛矿型形式存在,催化剂粒径在13～20 nm.以活性红X-3B溶液、活性橙K-NG和活性紫X-2R为反应模型,对所得催化剂的催化活性进行了评价,降解率分别达到99.9％、99.6％和99.5％,化剂循环利用时仍具有较高的催化活性.     

改性TiO2/蒙脱土的制备及其吸附催化性能

以钛酸丁酯为原料,采用溶胶-凝胶法制备TiO₂光催化材料,再以蒙脱土（MMT）为复合基质制备TiO₂/MMT复合材料,并以表面活性剂对其改性。扫描电镜和氮吸附曲线分析表明,经有机离子改性的TiO₂/MMT,其表面相对于蒙脱土原土表面更为细化,粉体颗粒粒径明显减小,表面结构卷曲松散,孔径由中孔变为大孔,且氮吸附能力提高一个数量级,吸附-催化性能显著提升。     

反相微乳液水热法合成锐钛矿TiO2微球及其光催化性能

以钛酸丁酯（TBT）为钛源、辛烷基苯酚聚氧乙烯醚(Triton X-100)为表面活性剂,采用反相微乳液水热法制备锐钛矿TiO2微球,并研究了反应体系中水含量对生成的锐钛矿TiO2微球性能的影响。采用粉末X射线粉末衍射（XRD）、傅里叶变换红外光谱（FTIR）、场发射扫描电子显微镜（FE-SEM）、透射电子显微镜（TEM）、荧光光谱（PL）对锐钛矿TiO2微球的结构、形貌和物相等进行表征。结果表明：在一定范围内增加钛酸丁酯/水（TBT/H2O）摩尔比,锐钛矿TiO2微球形貌由无规则形态向规则形貌转变,颗粒尺寸也随之变均匀。同时,以亚甲基蓝为目标降解物,对其光催化活性进行评价,结果表明颗粒尺寸和形貌的变化对其催化活性有较大影响,当TBT/H2O摩尔比为1:25时,微球尺寸均匀,催化活性最好,优于商业化P25。     

Visible-light-Induced photocatalytic degradation of azodyes in aqueous AgI/TiO2 dispersion

Agl/Ti02 was prepared by the deposition-precipitation method and was found to be a novel visible light driven photocatalyst. The catalyst showed high efficiency for the degradation of the nonbiodegradable azodyes reactive red K-2G, reactive brilliant red X-3B, reactive red K-2BP, and reactive yellow KD-3G under visible light irradiation (lambda > 420 nm). The catalyst's activity was maintained effectively after successive cyclic experiments under visible irradiation without the destruction of AgI. On the basis of the characterization of X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, the structure of AgI loaded on TiO2 did not significantly change before and after reaction. K-2G was completely decolorized and partly mineralized. The main intermediates are the small organic acids besides CO2 and cyanuric acid, which is photostable. The *OH is the main active oxygen species in the photocatalytic reaction by the studies of electron spin resonance and the effect of radical scavengers.