SO2-4/TiO2光催化降解苯酚

以工业硫酸氧钛为原料水解制得SO42-/TiO2光催化剂,并以苯酚为目标降解物,考察了SO24-/TiO2的光催化性能。结果表明:随着SO42-/TiO2制备过程中焙烧温度的升高,其光催化活性逐渐增加,650℃焙烧获得的SO24-/TiO2的光催化活性最好,此后再升高温度会因催化剂中硫的挥发而下降;在确定苯酚原液初始浓度为50 mg/L条件下,SO42-/TiO2的光催化降解苯酚的最佳工艺条件为反应时间2 h、苯酚pH为7、催化剂用量1 g/L。XRD、SEM和FTIR的分析结果显示实验温度下制得的SO42-/TiO2均为锐钛型TiO2;其间掺杂的SO24-在TiO2表面分散性较好,没有聚集成大的颗粒;红外分析的结果初步判定低温(<550℃)焙烧制得的催化剂SO42-在TiO2表面是螯合双配位吸附,高温焙烧时(>550℃)SO42-在TiO2表面是桥式配位吸附。     

TiO2 photocatalytic degradation of PCBs in soil-water systems containing fluoro surfactant

Titanium dioxide-mediated photodegradation of Polychlorinated biphenyls (PCBs) in soil/aqueous systems with added fluorinated surfactant was investigated. PCBs can bind tightly to organic matter in the soil, especially in aged, contaminated soil. Experiments showed an effective PCB photocatalytic degradation in mixed systems of soil/clay with anionic fluorinated surfactant FC-143 and TiO2. The FC-143 surfactant is stable in this photochemical process. PCB degradation rates in samples followed the order: spiked clay > spiked soil > Hudson River bank soil. The results suggest that anionic fluorinated surfactant may form semimicelles and/or admicelles on the surface of positively charged TiO2. The hydrophobic surface of TiO2 can provide a nonpolar phase that acts as a partioning medium for hydrophobic PCBs. Therefore, PCBs in soil can be released to the semimicelle and/or admicelle on the TiO2 surface and are effectively photodegraded in a dispersion containing anionic fluorinated surfactant. The combination of surfactant extraction and photooxidation forms the basis for a novel two-stage process for the removal and destruction of PCBs from soil.     

A combined photolytic-electrolytic system for the simultaneous recovery of copper and degradation of phenol or 4-chlorophenol in mixed solutions

The effects of the presence of copper on the photooxidation of phenol and 4-chlorophenol and of the presence of the phenols on the recovery of copper by electrodeposition are studied in three systems: a photolytic cell in the presence and absence of TiO2 as a catalyst or H2O2 as an oxidant; an electrolytic cell and a combined photolytic-electrolytic system. The optimum system for the simultaneous removal of copper and destruction of the phenols which overcomes the effects of copper-phenol reactions is a combined system with concentrator electrode technology incorporated into the electrolytic cell. This combined system achieves >99% removal of copper and destruction of phenol or 4-chlorophenol in an 8 h period.     

Modification of carbon-coated TiO2 by iron to increase adsorptivity and photoactivity for phenol

Carbon-coated TiO(2) modified by iron, were prepared from TiO(2) of anatase structure and PET modified by FeC(2)O(4). Catalysts were prepared by mixing powders of TiO(2) and modified PET and heating at different temperatures, from 400 to 800 degrees C under flow of Ar gas. High adsorption of phenol was observed on the catalyst heated at 400 degrees C, confirmed by FT-IR analysis. On this catalyst, fast rate of phenol decomposition was achieved by addition of small amount of H(2)O(2) to the reaction mixture. Phenol decomposition proceeded mainly through the direct oxidation of phenol species adsorbed on the catalyst surface due to the photo-Fenton reaction. Iron-modified carbon-coated TiO(2) catalysts heated at 500-800 degrees C showed almost no phenol adsorption or oxidation.     

Effect of the carbon coating in Fe-C-TiO(2) photocatalyst on phenol decomposition under UV irradiation via photo-Fenton process

Fe-C-TiO(2) photocatalysts which contained the residue carbon (0.2-3.3 mass%) were prepared from a mixture of TiO(2) and FeC(2)O(4) through the heating at 673-1173 K in Ar. These photocatalysts did not show a high adsorption of phenol, but they were active in photo-Fenton reactions during decomposition of phenol under UV irradiation with addition of H(2)O(2). It was proved that Fe(2+) governed the photoactivity of Fe-C-TiO(2) photocatalysts, it decreased with heat-treatment temperature above 773 K. For comparison, Fe-TiO(2) photocatalyst was prepared by heating TiO(2) and FeC(2)O(4) at 823 K in air for 3h. Phenol decomposition was going much slower on Fe-TiO(2) photocatalyst in comparison with Fe-C-TiO(2), of which mechanism was different, on the former phenol was decomposed by the radical reaction, on the latter through a complex reaction with iron and intermediates of phenol decomposition. Therefore carbon-coating TiO(2) was found to be advantageous for mounting iron and its application for the phenol decomposition via photo-Fenton process.     

负载TiO2/Fe^3＋的玻璃纤维反应器光催化苯酚

以玻璃纤维为载体,将TiO2负载到其表面形成了空间玻璃纤维反应器,引入Fe3＋作为掺杂改性离子,形成了负载TiO2/Fe^3＋的空间玻璃纤维光催化反应器,并以高压汞灯为光源进行了光催化降解水中苯酚的实验研究,考察了影响苯酚光催化降解的因素,确定了在UV365-250 W光源照射下,pH为3-5,O2通入量1.0 L/（min.L）,反应器内上升流速为0.7 m/min等实验条件下,初始浓度为30 mg/L的苯酚废水经120 min光催化反应后,降解率可达到85%,矿化率可达80%。     

Photooxidation mechanism of nitrogen-containing compounds at TiO2/H2O interfaces: an experimental and theoretical examination of hydrazine derivatives

The photocatalytic oxidation of oxalyldihydrazide, N,N'-bis(hydrazocarbonyl)hydrazide, N,N'-bis(ethoxycarbonyl)hydrazide, malonyldihydrazide, N-malonyl-bis[(N'-ethoxycarbonyl)hydrazide] was examined in aqueous TiO2 dispersions under UV illumination. The photomineralization of nitrogen and carbon atoms in the substrates into N2 gas, NH4+ (and/or NO3-) ions, and CO2 gas was determined by HPLC and GC analysis. The formation of carboxylic acid intermediates also occurred in the photooxidation process. The photocatalytic mechanism is discussed on the basis of the experimental results, and with molecular orbital (MO) simulation of frontier electron density and point charge. Substrate carbonyl groups readily adsorb on the TiO2 surface, and the bonds between carbonyl group carbon atoms and adjacent hydrazo group nitrogen atoms are cleaved predominantly in the initial photooxidation process. The hydrazo groups were photoconverted mainly into N2 gas (in mineralization yields above 70%) and partially to NH4 ions (below 10%). The formation of NO3- ions was scarcely recognized.     

负载TiO2/Fe3+的玻璃纤维反应器光催化苯酚

以玻璃纤维为载体,将TiO2负载到其表面形成了空间玻璃纤维反应器,引入Fe3+作为掺杂改性离子,形成了负载TiO2/Fe3+的空间玻璃纤维光催化反应器,并以高压汞灯为光源进行了光催化降解水中苯酚的实验研究,考察了影响苯酚光催化降解的因素,确定了在UV365～250 W光源照射下,pH为3～5,O2通入量1.0 L/(min.L),反应器内上升流速为0.7 m/min等实验条件下,初始浓度为30 mg/L的苯酚废水经120 min光催化反应后,降解率可达到85%,矿化率可达80%。     

外负载Ce-TiO_2/活性炭复合体对亚甲基蓝光催化

用超临界流体沉积法处理过的活性炭（AC）为载体,钛酸丁酯为前驱物,硝酸铈为掺杂剂,乙醇为溶剂,制备了外负载TiO2-Ce/Csurf复合材料。在紫外灯照射下,以亚甲基蓝溶液为标准模拟降解物,研究了复合体不同热处理温度、不同浓度、不同亚甲基蓝浓度、不同铈掺杂量以及不同反应温度对光催化性能的影响。结果表明：外负载催化剂的催化性能要高于纯TiO2和体负载催化剂。铈离子掺杂能抑制TiO2晶粒生长,阻碍了TiO2由锐钛矿型向金红石型的转变。当铈离子掺杂量为1.5%,热处理温度为600℃,亚甲基蓝溶液初始浓度为5.5 mg/L,样品浓度为1.5 g/L时,光催化性能最好。     

TiO2-catalyzed photooxidation of arsenite to arsenate in aqueous samples

The TiO2-catalyzed photooxidation of arsenite (As(III)) to arsenate (As(V)) was studied in aqueous TiO2 suspensions using a solar simulator which emitted ultraviolet and visible radiations. The concentration of As(III) was varied between 50 microg l(-1) and 10 mg l(-1), and the concentration of TiO2 between 1 mg l(-1) and 50 mg l(-1). Total oxidation of As(III) to As(V) occurred within minutes. The concentration of As(III) declined exponentially which indicates first-order kinetics. In the pH range between 5 and 9 there was no significant influence of the pH of the suspension on the reaction rate. Batch experiments without irradiation showed that part of the arsenic was adsorbed on the TiO2 surface. When using 100 microg l(-1) As and between 1 mg l(-1) and 50 mg l(-1) TiO2, 8-39% of As(III) and up to 73% of As(V) were adsorbed by TiO2. As(III) was also oxidized by UV radiation in the absence of TiO2, but the reaction was slower than in the presence of TiO2 resulting in an irradiation time too long for practical use. In addition, oxidation of As(III) in the presence of TiO2 was also observed under solar irradiation within a few minutes.     

Improvement of water resistance by Fe2O3/TiO2 photoelectrocatalysts for formaldehyde removal: experimental and theoretical investigation

Environmental Science and Pollution Research - TiO2-based photocatalysts are a potential technology for removing indoor formaldehyde (CHOH) owing to their strong photooxidation ability. However,...     

Performance of photocatalytic reactors using immobilized TiO2 film for the degradation of phenol and methylene blue dye present in water stream

TiO2 thin film photocatalyst was successfully synthesized and immobilized on glass reactor tube using sol-gel method. The synthesized TiO2 coating was transparent, which enabled the penetration of ultra-violet (UV) light to the catalyst surface. Two photocatalytic reactors with different operating modes were tested: (a) tubular photocatalytic reactor with re-circulation mode and (b) batch photocatalytic reactor. A new proposed TiO2 synthesized film formulation of 1 titanium isopropoxide: 8 isopropanol: 3 acetyl acetone: 1.1 H2O: 0.05 acetic acid (in molar ratio) gave excellent photocatalytic activity for degradation of phenol and methylene blue dye present in the water. The half-life time, t1/2 of photocatalytic degradation of phenol was 56 min at the initial phenol concentration of 1000 microM in the batch reactor. In the tubular photocatalytic reactor, 5 re-circulation passes with residence time of 2.2 min (single pass) degraded 50% of 40-microM methylene blue dye. Initial phenol concentration, presence of hydrogen peroxide, presence of air bubbling and stirring speed as the process variables were studied in the batch reactor. Initial methylene blue concentration, pH value, light intensity and reaction temperature were studied as the process variables in the tubular reactor. The synthesized TiO2 thin film was characterized using SEM, XRD and EDX analysis. A comparative performance between the synthesized TiO2 thin film and commercial TiO2 particles (99% anatase) was evaluated under the same experimental conditions. The TiO2 film was equally active as the TiO2 powder catalyst.     

固体超强酸SO4^2-／TiO2-SnO2／Ce^4＋光催化降解含酚废水

采用共沉淀-浸渍法制备了固体超强酸SO4^2-／TiO2-SnO2／Ce^4＋,并用XRD、SEM等方法对其结构进行了表征。以苯酚的光催化降解为反应模型,确定了最佳的工艺条件和催化剂再生方法。结果表明：在pH值为6,苯酚初始浓度为50mg／L,催化剂投加量4g／L,光照距离12cm,光照时间为150min,降解率达67．73％,添加助催化剂H2O2后,反应60min,苯酚降解率达到86．33％,催化剂的最佳再生方法是先用1mol／L的硫酸浸渍24h后,在450℃下焙烧6h。     

Photocatalytic reactions of pyrene at TiO2/water interfaces

The photocatalytic oxidation of pyrene preadsorbed on TiO2 is examined in aqueous suspension under UV irradiation. Chemical oxygen demand measurements, UV-VIS spectrophotometer, infrared spectrometer and GC-MS analytical techniques were used to monitor the formed intermediates. During the oxidation processes, the ring-open reaction, hydroxylation and ketolysis occurred to produce some intermediate products (4-oxapyrene-5-one, 1,6- or 1,8-pyrenediones, 4,5-phenanthrenedialdehyde, cyclopenta[def]phenanthrene). Some factors affecting the photodegradation rate were also studied. The results were different from other studies: The pH of the dispersion, ratio of Py/TiO2:water had little effect on the photooxidation rate of pyrene catalyzed by TiO2, while the surface coverage, addition of Fe3+ affected it greatly.     

外负载Ce-TiO2/活性炭复合体对亚甲基蓝光催化

用超临界流体沉积法处理过的活性炭(AC)为载体,钛酸丁酯为前驱物,硝酸铈为掺杂剂,乙醇为溶剂,制备了外负载TiO2-Ce/Csurf复合材料。在紫外灯照射下,以亚甲基蓝溶液为标准模拟降解物,研究了复合体不同热处理温度、不同浓度、不同亚甲基蓝浓度、不同铈掺杂量以及不同反应温度对光催化性能的影响。结果表明:外负载催化剂的催化性能要高于纯TiO2和体负载催化剂。铈离子掺杂能抑制TiO2晶粒生长,阻碍了TiO2由锐钛矿型向金红石型的转变。当铈离子掺杂量为1.5%,热处理温度为600℃,亚甲基蓝溶液初始浓度为5.5 mg/L,样品浓度为1.5 g/L时,光催化性能最好。     

Radiolysis of aqueous phenol solutions with nanoparticles. 1. Phenol degradation and TOC removal in solutions containing TiO2 induced by UV,gamma-ray and electron beams

Aqueous phenol solutions containing TiO(2) nanoparticles were irradiated with ultraviolet (UV), gamma-ray and electron beams. Organic compounds were fully removed by each type of radiation in the presence of the particles. The absorbed energy of the ionizing radiation (gamma-ray and electron beams) needed for removal was much lower than that of UV photocatalysis. Phenol was decomposed by the ionizing radiation in the absence of the nanoparticles and the addition of TiO(2) had no significant effect on phenol decomposition rate. Instead, total organic carbon (TOC) removal using the ionizing radiation was accelerated drastically by TiO(2). It is suggested that TiO(2) particles affect the intermediate compounds produced through the decomposition of phenol. The amount of removed TOC per absorbed energy were compared in the absence and the presence of TiO(2) nanoparticles. Radiolysis with the nanoparticles showed consistently high rate and high efficiency of TOC removal.     

Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

Environmental Science and Pollution Research - In this study, the newly synthesized TiO2 and N doped TiO2 clusters were added to silica sol to synthesize N-TiO2/SiO2 composites via the...     

Solar TiO2-assisted photocatalytic degradation of IGCC power station effluents using a Fresnel lens

The heterogeneous TiO2 assisted photocatalytic degradation of wastewater from a thermoelectric power station under concentrated solar light irradiation using a Fresnel lens has been studied. The efficiency of photocatalytic degradation was determined from the analysis of cyanide and formate removal. Firstly, the influence of the initial concentration of H2O2 and TiO2 on the degradation kinetics of cyanides and formates was studied based on a factorial experimental design. Experimental kinetic constants were fitted using neural networks. Results showed that the photocatalytic process was effective for cyanides destruction (mainly following a molecular mechanism), whereas most of formates (degraded mainly via a radical path) remained unaffected. Finally, to improve formates degradation, the effect of lowering pH on their degradation rate was evaluated after complete cyanide destruction. The photooxidation efficiency of formates reaches a maximum at pH around 5-6. Above pH 6, formate anion is subjected to electrostatic repulsion with the negative surface of TiO2. At pH<4.5, formate adsorption and photon absorption are reduced due to some catalyst agglomeration.     

The enhancement of TiO2 photocatalytic activity by hydrogen thermal treatment

In this study, conventional TiO2 powder was heated in hydrogen (H2) gas at a high temperature as pretreatment. The photoactivity of the treated TiO2 samples was evaluated in the photodegradation of sulfosalicylic acid (SSA) in aqueous suspension. The experimental results demonstrated that the photodegradation rates of SSA were significantly enhanced by using the H2-treated TiO2 catalysts and an optimum temperature for the H2 treatment was found to be of 500-600 degrees C. The in situ electron paramagnetic resonance (EPR) signal intensity of oxygen vacancies (OV) and trivalent titanium (Ti3+) associated with the photocatalytic activity was studied. The results proved the presence of OV and Ti3+ in the lattice of the H2-treated TiO2 and indicated that both were contributed to the enhancement of photocatalytic activity. Moreover, the experimental results presented that the EPR signal intensity of OV and Ti3+ in the H2-treated TiO2 samples after 10 months storage was still significant higher than that in the untreated TiO2 catalyst. The experiment also demonstrated that the significant enhancement occurred in the photodegradation of phenol using the H2-treated TiO2.     

Photocatalytic degradation of the herbicide pendimethalin using nanoparticles of BaTiO3/TiO2 prepared by gel to crystalline conversion method: a kinetic approach

Photocatalytic degradation of the herbicide, pendimethalin (PM) was investigated with BaTiO3/TiO2 UV light system in the presence of peroxide and persulphate species in aqueous medium. The nanoparticles of BaTiO3 and TiO2 were obtained by gel to crystallite conversion method. These photo catalysts are characterized by energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), x-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) adsorption isotherm and reflectance spectral studies. The quantum yields for TiO2 and BaTiO3 for the degradation reactions are 3.166 Einstein m(-2) s(-1) and 2.729 Einstein m(-2) s(-1) and catalytic efficiencies are 6.0444 x 10(-7) mg(-2)h(-1)L2 and 5.403 x 10(-7) mg(-2)h(-1)L2, respectively as calculated from experimental results. BaTiO3 exhibited comparable photocatalytic efficiency in the degradation of pendimethalin as the most widely used TiO2 photocatalyst. The persulphate played an important role in enhancing the rate of degradation of pendimethalin when compared to hydrogen peroxide. The degradation process of pendimethalin followed the first-order kinetics and it is in agreement with Langmuir-Hinshelwood model of surface mechanism. The reason for high stability of pendimethalin for UV-degradation even in the presence of catalyst and oxidizing agents were explored. The higher rate of degradation was observed in alkaline medium at pH 11. The degradation process was monitored by spectroscopic techniques such as ultra violet-visible (UV-Vis), infrared (IR) and gas chromatography mass spectroscopy (GC-MS). The major intermediate products identified were: N-propyl-2-nitro-6-amino-3, 4-xylidine, (2, 3-dimethyl-5-nitro-6-hydroxy amine) phenol and N-Propyl-3, 4-dimethyl-2, 6-dinitroaniline by GC-MS analysis and the probable reaction mechanism has been proposed based on these products.