光催化辅助高浓度臭氧循环工艺降解对氯苯酚及协同机理

针对臭氧(O3)降解对氯苯酚(4-CP)中效率有限且尾气排放高的问题,采用光催化辅助高浓度臭氧循环工艺并对TiO2浓度、循环气量以及pH值等因素进行研究,结合对苯醌变化及猝灭剂试验分析其协同机理.循环气量为2.0 L·min-1,TiO2投加量为250 mg·L-1时,O3/TiO2/UV体系的降解动力学系数为0.29...     

Optimisation of degradation conditions of 1,8-diazabicyclo[5.4.0]undec-7-ene in water and reaction kinetics analysis using a cocurrent downflow contactor photocatalytic reactor

The photocatalytic degradation of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, a non-biodegradable nitrogenous organic compound) in water was optimised under UV radiation using titanium dioxide photocatalyst. The reactor used was a pilot scale cocurrent downflow contactor photocatalytic reactor (CDCPR), a system offering very high mass transfer efficiency. The effect of photocatalyst loading, initial substrate concentration, temperature, pH, and different combinations of UV, O₂, H₂O₂ and TiO₂ on the photocatalytic oxidation of DBU was investigated. The TiO₂ photocatalyst used was Degussa VP Aeroperl P25/20, a granulated form of Degussa P-25, recently developed to ameliorate downstream catalyst separation problems. The CDCPR was fitted with an internally and vertically mounted 1.0 kW UV lamp. The reactions were carried out at 40–60 °C and 1 barg, with the reactor being operated in closed loop recycle mode and suspended photocatalyst being re-circulated. Optimisation of reaction conditions using a combination of TiO₂, UV radiation and O₂ gave the most rapid degradation and mineralisation of the DBU in comparison with other processes. Under optimised conditions, 100% degradation of DBU was achieved in 45 min, with a quantum yield of 7.39, using a 1 kW lamp, 0.5 g/dm³ TiO₂, 100 mg/dm³ DBU, 1 barg, 50 °C and pH of 3.17. Investigating the reaction pathway and its modelling showed a first order dependency, incorporating the effect of first intermediates of degradation. The activation energy was found to be 54.68 kJ mol⁻¹ showing a significant influence of temperature on the photocatalytic degradation of DBU.     

不同物相TiO2对H2O2/O3氧化效能的影响

研究了不同物相TiO₂对H₂O₂/O₃氧化效能的影响,目标有机物为羟基自由基探针化合物乙酸。结果表明,在初始pH为7.0和10.0时,加入TiO₂反而降低了H₂O₂/O₃的氧化效率,其中锐钛矿TiO₂比金红石TiO₂的减弱作用更为明显。当初始pH为3.0时,金红石TiO₂能显著提高H₂O₂/O₃的氧化效率,但锐钛矿TiO₂影响不明显。机理分析表明,H₂O₂浓度及其衰减速率与乙酸的去除效率有很大的相关性。在pH为7.0和10.0时,两种物相TiO₂均能加快H₂O₂的分解,其中锐钛矿TiO₂作用更为显著。此条件下HO₂^-能有效引发臭氧分解产生羟基自由基,故H₂O₂过快分解反而降低了乙酸的去除效果。在pH为3.0时,H₂O₂去质子化反应困难,故O₃/H₂O₂氧化效率极低,H₂O₂浓度也几乎不变。加入TiO₂能明显提高H₂O₂的分解速率,相比金红石TiO₂,锐钛矿TiO₂使H₂O₂在5 min内基本分解完毕,但其对H₂O₂/O₃氧化效率几乎没有影响。饱和臭氧水分解速度的批处理实验也有相似的结果。由此可见,合适引发剂浓度可能是保证臭氧类高级氧化技术较高效率的关键,否则只会导致氧化剂的无效过快分解。利用氯化硝基四氮唑蓝法对比分析了酸性条件下H₂O₂/O₃、锐钛矿TiO₂/H₂O₂/O₃和金红石TiO₂/H₂O₂/O₃体系产生超氧自由基(·O₂^-)的量,其大小顺序为:H₂O₂/O₃< 金红石TiO₂/H₂O₂/O₃< 锐钛矿TiO₂/H₂O₂/O₃,这与前面结果吻合很好。     

Photocatalytic activation of TiO2 under visible light using Acid Red 44

The activation of TiO₂ photocatalyst for photocatalysis under the visible light using Acid Red 44 (C₁₀H₇N=NC₁₀H₃(SO₃Na)₂OH) is described. Adjustment of the pH enhanced the photocatalytic activation of TiO₂ in the presence of visible light. This confirms that the adsorption of a dye on TiO₂ surface is an important factor in dye-photosensitization. The differences in the photocatalytic activation mechanism under visible irradiated conditions with that of UV irradiated condition are proposed. The dye-sensitized photocatalysis under visible light was applied to the decomposition of phenol, is a toxic chemical used in industry and frequently discharged into water.     

金属氧化物掺杂高岭土纳米 二氧化钛光催化复合材料研究

以高岭石为载体,以钛酸四丁酯为前驱体,采用溶胶-凝胶法制备金属氧化物掺杂高岭土纳米二氧化钛光催化复合材料。采用X射线衍射（XRD）、红外光谱（FT-IR）和拉曼光谱（Raman）对复合材料进行表征,并通过在紫外光下降解云母珠光工业废水来考察其光催化性能。研究了不同金属氧化物掺杂浓度对复合材料光催化活性的影响。实验结果表明：金属氧化物三氧化二铁、氧化锌掺杂使锐钛矿二氧化钛晶相特征衍射峰宽化,掺杂生成钛铁矿、红锌矿新相,影响锐钛矿二氧化钛结晶度。在紫外光下降解6 h,掺杂质量分数为0.5%的三氧化二铁对废水降解率为98.8%,掺杂质量分数为1.5%的氧化锌对其降解率为91.4%。     

色氨酸辅助合成光催化活性增强的球形纳米TiO2

以L-色氨酸（L-Trp）为生物模板,采用简单水解及煅烧后制备了球形结构TiO₂纳米光催化剂。通过X射线衍射、扫描电子显微镜、红外光谱、紫外-可见漫反射光谱、光致发光光谱和N₂吸附-解吸等方法对制得的TiO₂纳米材料进行表征。在催化剂合成过程中,L-Trp作为生物模板发挥至关重要的作用,能够指导球形结构纳米TiO₂的形成。考察了不同煅烧温度下制备的TiO₂样品光催化活性,结果表明550℃时制备的TiO₂样品具有优异的光催化活性,紫外光照射30min对甲基橙溶液的降解率达到95%左右,主要是由于较大比表面积和球形结构的协同效应。光催化剂稳定性实验表明,所制备的TiO₂纳米材料可作为一种实用有效的光催化剂用于紫外光照射下降解有机染料。同时,对L-Trp辅助下球形结构TiO₂纳米颗粒的可能生长机理进行讨论。     

TiO2纳米管/UV/O3对腐殖酸的降解动力学

用自制的TiO₂纳米管（TNTs）作为催化剂,对腐殖酸进行TNTs/UV/O₃工艺降解研究.从动力学角度分析了光催化、臭氧化的协同作用及催化剂煅烧温度的影响,考察了反应温度、初始pH值、催化剂投加量和臭氧投加量对降解速率的影响,建立了新型动力学模型.结果表明,光催化和臭氧化有很强的协同作用,催化剂最佳煅烧温度为400℃,腐殖酸的TOC降解过程符合零级反应,模型显示当原水pH值为7.35,TNTs投加量0.806g·L^-1,O₃投加量0.49g·h^-1时TNTs/UV/O₃对腐殖酸TOC的降解取得最佳反应速率,当反应温度T为25℃时,最佳k为0.8095mg·L^-1·min^-1,当反应温度T为30℃时,最佳k为0.8231mg·L^-1·min^-1.试验结果和模型结果对比得出试验值基本符合动力学模型.     

H2O2强化光催化处理苯胺化工废水的应用试验

研究者在苯胺模拟废水高级氧化处理方面开展了很多研究,但针对炼化企业苯胺装置废水含盐高、色度高、COD降解难等问题尚未开展工程应用。为解决苯胺生产废水的实际问题,本研究开展了TiO₂/UV-H₂O₂氧化降解苯胺废水（1~2m³/h）的现场试验研究。考察了苯胺废水在单独TiO₂/UV、单独H₂O₂氧化及TiO₂/UV-H₂O₂协同作用下的处理效果,提出了苯胺废水的最佳处理工艺方案,并进行了成本核算。结果表明,单独TiO₂/UV和单独H₂O₂氧化对苯胺废水的脱色率和COD去除率偏低,而TiO₂/UV-H₂O₂协同作用时苯胺废水脱色率和COD去除率可达95%以上。协同氧化体系中,H₂O₂的氧化降解作用显著,H₂O₂投加量1%~2%;酸性条件利于苯胺废水的降解,特别是pH=3.8~4.2时;TiO₂/UV和H₂O₂协同作用一段时间后,停止UV而凭借残余H₂O₂可以将体系中的中间产物继续降解直至矿化成CO₂。TiO₂/UV- H₂O₂协同处理炼化企业苯胺生产废水,出水COD≤60mg/L,色度≤20倍,单位能耗约18.44kW·h/m³,明显低于文献报道值,具有显著的技术性与经济性。     

Photocatalytic degradation of omethoate using NaY zeolite-supported TiO2

The degradation of omethoate was conducted using H₂O₂ as oxidant, TiO₂ supported on NaY zeolite as photocatalyst and a 300 W lamp as light source. The effect of the calcination temperature of the photocatalyst, the amount of TiO₂ loaded on NaY zeolite, the photocatalyst amount, the pH value and the radiation time on the degradation ratio of omethoate were investigated. The results show that TiO₂/NaY zeolite photocatalyst prepared by sol-gel method had good photocatalysis. The photocatalytic optimum oxidation conditions of omethoate are as follows: the calcination temperature of the photocatalyst is 550°C,the amount of TiO₂ loaded on NaY zeolite is 35.2 wt-%, the amount of photocatalyst is 5 g/L, pH=8 and the radiation time is 180 min. Under these conditions, the removal ratio of omethoate is up to 93%.     

碳酸银光催化性能研究

银系光催化剂制备方法简单且带隙较窄,在可见光照射下具有良好的光催化效果,因此受到人们的广泛关注。以罗丹明B为降解物,在模拟可见光条件下利用碳酸银进行光催化降解实验,比较同等条件下碳酸银和二氧化钛的光催化性能,探究了碳酸银在不同pH、降解物质量浓度和催化剂投加量条件下的光催化活性,并利用总有机碳（TOC）分析矿化程度。通过X射线衍射仪（XRD）、激光拉曼光谱仪（RRS）、傅里叶变换红外光谱仪（FT-IR）和紫外吸收光谱仪（UV-Vis）对碳酸银进行表征并分析其晶相组成。结果表明,在同等条件下碳酸银对罗丹明B的光催化降解速率远大于二氧化钛,并且在溶液pH小于7、碳酸银投加量为 1 g/L条件下催化剂对质量浓度为5 mg/L的罗丹明B染料的光催化降解效果最好,紫外灯照射100 min后罗丹明B染料降解率达到98%以上,最终矿化率达到66%。     

Efficient photodegradation of phenol assisted by persulfate under visible light irradiation via a nitrogen-doped titanium-carbon composite

To realize the utilization of visible light and improve the photocatalytic efficiency of organic pollutant degradation in wastewater, a nitrogen-doped titanium-carbon composite (N-TiO₂/AC) prepared by sol-gel methods was applied in the photodegradation of phenol assisted by persulfate under visible light irradiation (named N-TiO₂/AC/PS/VIS). The results show that a synergistic effect exists between visible-light photocatalysis and persulfate activation. Compared with TiO₂/PS/VIS, the phenol degradation rate was found to be observably improved by 65% in the N-TiO₂/AC/PS/VIS system. This significant increase in degradation rate was mainly attributed to the following two factors: 1) The N and C doping can change the crystal structure of TiO₂, which extends the TiO₂ absorption wavelength range to the visible light region. 2) As an electron acceptor, PS can not only prevent electrons and holes from recombining with each other but can also generate strong oxidizing radicals such as ∙SO₄^– and ∙OH to accelerate the reaction dynamics. The process of phenol degradation was found to be consistent with the Langmuir pseudo-first-order kinetic model with an apparent rate constant k of 1.73 min^–1. The N-TiO₂/AC/PS/VIS process was proven to be a facile method for pollutant degradation with high pH adaptability, excellent visible-light utilization and good application prospects.     

微波助离子液体中硫-钕共掺杂TiO2催化剂的制备及其微波强化光催化活性

在离子液体介质中,采用溶胶-凝胶法,以钛酸四丁酯为前驱物,用微波干燥法合成S和Nd共掺杂纳米TiO₂光催化剂TiO₂-S-Nd。分别采用IR、XRD、BET和SEM对催化剂结构进行测试与表征,以甲基橙为模拟污染物,在微波超声波组合催化合成仪中,恒温（25 ℃）下分别利用微波辐射、紫外光照及微波辐射+紫外光照3种降解条件,着重考察Nd掺杂量和S掺杂量对TiO₂-S-Nd光催化活性的影响。结果表明,在离子液体用量5.6 mL、n(Nd)∶n(Ti)=0.015和n(S)∶n(Ti)=2时,经功率为350 W的微波加热干燥处理20 min的半成品催化剂,再在700 ℃高温炉焙烧2 h,制得TiO₂-S-Nd催化剂,具有较高的光催化降解活性。且在3种降解条件下,TiO₂-S-Nd对甲基橙降解率分别为12.11%、88.91%和100%,表明微波与紫外光照有较好的协同作用,即微波-紫外光照具有强化S和Nd共掺杂TiO₂-S-Nd催化剂降解甲基橙的效果,并且所制得的共掺杂TiO₂-S-Nd催化剂的光催化活性均高于单一S 或Nd掺杂TiO₂的光催化活性,说明S和Nd共掺杂也具有协同作用。     

二氧化钛纳米结构形貌可控合成及光催化性能

以不同方法制备棒状、球状和花状3种形貌的TiO_2纳米粒子,采用X粉末衍射、扫描电子显微镜、荧光光谱和紫外-可见漫反射等对TiO_2纳米粒子进行结构及形貌分析。以亚甲基蓝为降解模型,分别在紫外光与可见光条件下对TiO_2纳米粒子进行光催化性能研究,分析TiO_2的形貌结构影响光催化性能的机理。结果表明,花状TiO_2纳米粒子光催化性能最好,其中高能晶面与微观形貌尺寸对TiO_2光催化性能具有重要影响。     

C2H2 oxidation by plasma/TiO2 combination: Influence of the porosity, and photocatalytic mechanisms under plasma exposure

Plasma/catalyst combination is an active solution to reach high conversion rates at low energetic cost. TiO₂ is one of the catalysts frequently used in dielectric barrier discharges. Plasma/TiO₂ synergy was already exhibited but the mechanisms still have to be understood. This work distinguishes three main effects involved in the synergy: (a) effect of catalyst on the injected power, (b) the effect of porosity on C₂H₂ oxidation, and (c) the photocatalytic degradation of C₂H₂ on TiO₂ under plasma exposure. Different glass fibres-based catalytic materials coated with SiO₂ and/or TiO₂ nano-particles are used to separate these three contributions regarding to C₂H₂ conversion. It is reported that at constant voltage the injected power is mainly increased by the presence of glass fibres. C₂H₂ oxidation is mainly enhanced by the macroporosity of glass fibres and in a minor way by the nano-particles. The production of O atoms close to the surface is probably responsible for the higher C₂H₂ removal efficiency with porous material. The photocatalytic activity of TiO₂ is negligible in the plasma except if additional UV lamps are used to activate TiO₂. With external UV, photocatalytic activity is more efficient in the plasma phase than in a neutral gas phase. This plasma/photocatalysis synergy is due to the use of O atoms in photocatalytic mechanisms.     

ESR study of the initial stages of the photocatalytic oxidation of toluene over TiO2 powders

In the present work, the initial stages of the photocatalytic oxidation of toluene over two commercial TiO₂ powders were investigated at the molecular level by ESR spectroscopy. UV-irradiation of the TiO₂ samples, which present different phase composition and surface area, gave rise to several oxygenated radicals like O⁻, O₂⁻ and O₃⁻, as well as Ti³⁺ centers. The proportion of these species generated depends on the gaseous environment (vacuum or oxygen), and the structural and morphological characteristic of the TiO₂ samples. In contrast, co-adsorption of toluene and oxygen on any of the TiO₂ samples studied yields upon UV illumination slightly different ESR signals, which have been assigned to the formation of benzylperoxy radicals, Ph-CH₂OO, adsorbed on the semiconductor. Such species are only detected when TiO₂ is exposed to toluene–oxygen mixtures enriched in the organic, and under these conditions neither of the other oxygenated radicals is formed. The reasons for this behavior are discussed on the basis of the mechanism for the photocatalytic oxidation of toluene.     

Photocatalytic treatment of water-soluble pesticides by photo-Fenton and TiO2 using solar energy

The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems of special interest because natural-solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors (CPCs) specially designed for solar photocatalytic applications. Experimental conditions allowed disappearance of pesticide and degree of mineralisation achieved in the two photocatalytic systems to be compared. In order to assure that the photocatalytic results are consistent, hydrolysis and photolysis tests have been performed with the four pesticides. The initial concentration tested with imidacloprid, formetanate and methomyl was 50 and 30 mg/l with diuron, and the catalyst concentrations were 200 mg/l and 0.05 mM with TiO₂ and iron, respectively. Total disappearance of the parent compounds and 90% mineralisation have been attained with all pesticides tested, methomyl being the most difficult to be degraded with both treatments. First-order rate constants, initial rate, time necessary for mineralising 90% of the initial TOC and hydrogen peroxide consumption were calculated in all cases, enabling comparison both of treatments and of the selected pesticide reactivity.     

Formation of singlet molecular oxygen associated with the formation of superoxide radicals in aqueous suspensions of TiO2 photocatalysts

The production and decay of singlet molecular oxygen (¹O₂) in TiO₂ photocatalysis were investigated by monitoring its phosphorescence under various reaction conditions. First, the effects of additives such as KBr, KSCN, KI, H₂O₂, and ethanol on the amount of ¹O₂ produced by photo excitation of P25 TiO₂ were measured. The same additives were employed to investigate the effect on the amount of O₂⁻ produced. Comparison between the effects on ¹O₂ and O₂⁻ suggested that ¹O₂ is formed by the electron transfer mechanism, the reduction of molecular oxygens to O₂⁻ by photogenerated electrons and the subsequent oxidation of O₂⁻ to ¹O₂ by photogenerated holes. The formation of ¹O₂ decreased at pH < 5 and pH > 11, indicating that the intermediate O₂⁻ is stabilized at the terminal OH site of the TiO₂ surface in the pH range of 5 < pH < 11. Eighteen commercially available TiO₂ photocatalysts were compared on the formation of ¹O₂ and O₂⁻ in an aqueous suspension system. The formation of ¹O₂ was increased with decreasing size of TiO₂ particles, indicating that a large specific surface area causes a higher possibility of reduction producing O₂⁻ and then a large amount of ¹O₂ is formed. The difference in the crystal phase (rutile and anatase) did not affect the formation of ¹O₂.     

The effect of platinum and silver deposits in the photocatalytic oxidation of resorcinol

The effects of platinum (Pt) and silver (Ag) metallisation in the photocatalytic oxidation of resorcinol at pH 3 ± 0.5 have been investigated. The photocatalytic degradation of resorcinol was significantly improved by Pt/TiO₂, while the presence of Ag/TiO₂ enhanced the initial photocatalytic degradation rate of resorcinol slightly. Likewise, the photocatalytic mineralisation of resorcinol continued to be enhanced by Pt/TiO₂, but it was retarded when Ag/TiO₂ was used.

The function of Pt and Ag deposits on the surface of TiO₂ has been found to be markedly influenced by the interaction of resorcinol and its degradation products with the metal deposits. The presence of Pt or Ag on the surface of TiO₂ altered the distribution of degradation products of resorcinol as well as the production of photoactive species for the photocatalytic oxidation of resorcinol. The X-ray photoelectron spectroscopy (XPS), zeta potential and transmission electron microscopy (TEM) analyses have indicated that the contrasting effect of Pt and Ag deposits were governed by the oxidation states and the catalytic property of metal deposits. In addition to that, it has been found that the roles of metal deposits are specific and should not be generalised.     

Yb-La/TiO_2光催化剂的制备工艺研究

采用溶胶-凝胶法制备镱镧共掺杂二氧化钛光催化剂Yb-La/TiO_2,在紫外光照射下,以罗丹明B作为目标降解染料,考察催化剂的光催化性能。结果表明,制备Yb-La/TiO_2光催化剂的最佳条件为:n(La)∶n(Yb)∶n(Ti)=1.2∶1.0∶100,钛酸丁酯用量10 m L,无水乙醇用量50 m L,聚乙二醇用量0.4 g,冰醋酸用量2 m L,pH=2.3,陈化4天,150℃干燥24 h,550℃焙烧2 h。此条件下制备的Yb-La/TiO_2光催化剂对罗丹明B的降解率达93.37%,重复使用3次后,降解率仍高于80%。     

稀土元素Ce掺杂TiO_2光催化剂制备及微波强化光催化活性

在[Bmim]PF6离子液体介质中微波辅助制备稀土元素Ce掺杂改性的TiO_2光催化剂TiO_2-Ce,以甲基橙溶液和苯酚溶液为模拟污染物,在紫外光照和微波辐射-紫外光照降解条件下考察TiO_2-Ce催化剂的光催化活性。利用荧光技术以对苯二甲酸作为荧光探针检测TiO_2-Ce催化剂表面产生的羟基自由基,并对光催化降解反应进行动力学分析,以了解光催化降解反应机理。结果表明,通过优化反应条件制得的TiO_2-Ce催化剂具有较高光催化降解活性和热稳定性,在紫外光照和微波辐射-紫外光照条件下降解60 min后,甲基橙降解率分别为98.6%和99.3%,苯酚降解率分别为96.6%和97.2%。荧光光谱分析表明,TiO_2-Ce在微波辐射-紫外光照条件下产生的羟基自由基比紫外光照多,因而微波辐射-紫外光照具有强化TiO_2-Ce降解模拟污染物作用的效果。反应动力学数据表明,TiO_2-Ce光催化降解甲基橙溶液反应呈一级反应动力学规律,其表观速率常数k最大值为0.056 2 min-1。