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1.

Purpose  

TiO2 photocatalytic degradation of 4-chlorobiphenyl (PCB3) in aqueous solution under UV irradiation was investigated as affected by different environmental factors, including initial PCB3 concentration, TiO2 content, UV intensity, H2O2 concentration, cosolvents, and surfactants.  相似文献   

2.
The oxidation of di-(2-ethylhexyl) phthalate (DEHP) in solution using UV/H2O2 and direct UV photolysis are analyzed in this study. It was found that DEHP was 100% removal in the solution by 180-min UV/H2O2 treatment and 73.5% removal by 180-min direct UV photolysis. The effect of different factors, such as DEHP concentration, H2O2 concentration, and UV light intensity, on photochemical degradation was investigated. The degradation mechanism of DEHP and the acute toxicity of intermediates were also studied. The photochemical degradation process was found to follow pseudo-first-order kinetics. The results of our study suggested that the concentration with 40 mg/L H2O2 and 5 μg/mL DEHP in the solution at pH 7 with 10.0?×?10?6 Einstein l?1?s?1 UV was the optimal condition for the photochemical degradation of DEHP. The photochemical degradation with UV/H2O2 can be an efficient method to remove DEHP in wastewater.  相似文献   

3.
The adsorption and photocatalytic degradation of methyl orange (MO) aqueous solution under visible light illumination by polythiophene/titanium dioxide (PTh/TiO2) composite particles were studied. The experimental observations from UV–vis spectrophotometer indicate that MO molecules were degraded in a different degree during the visible light-induced photocatalysis reaction. We propose a new degradation mechanism of MO during the photocatalytic reaction, based on blue shift of UV–vis absorption spectra of MO solution and other researches. The data from total organic carbon analyzer definitely prove that MO can be mineralized to CO2 and H2O, and some intermediate products are generated during the photocatalysis degradation of MO.  相似文献   

4.
The partial phase transformation of nanometer TiO2 powder from anatase phase to rutile phase was realized by heat-treatment and a new TiO2 photocatalyst which could be excited by visible light was obtained. The heat-treated TiO2 powder at different stage of transition crystal was characterized and monitored by XRD, TEM, FT-IR and UV–vis DRS methods. The test of photocatalytic activity of the heat-treated TiO2 powder was carried out by the photocatalytic degradation of rhodamine B and acid orange II dyes, respectively, in aqueous solution under visible light irradiation. The results indicate that the nanometer TiO2 photocatalyst heat-treated at 500°C for 60 min shows the highest photocatalytic activity, that is, it can effectively degrade the rhodamine B and acid orange II under visible light irradiation. The remarkable improvement of photocatalytic activity of heat-treated TiO2 powder at 500°C for 60 min was mainly illustrated by the formation of special interphase between rutile and anatase phases, which not only restrains the recombination of photogenerated electrons and holes, but also reduces the adsorbability of nanometer anatase TiO2 powder properly for various dyes. Additionally, the effects of dye-assisting chemicals such as Na2CO3 and NaCl on the photocatalytic degradation were also studied.  相似文献   

5.
CoFe2O4/Zn2SnO4 composite was synthesized using a simple two-step process and applied as a novel-efficient photocatalyst for the rhodamine B degradation from aqueous solution. Characterization techniques such as X-ray diffraction (XRD), N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), EDS analysis, and diffuse reflectance spectroscopy were employed in order to investigate the physical and chemical properties of composite. Higher values of the specific surface area, pore volume and diameter, and a smaller band-gap energy promoted a greater catalytic activity of CoFe2O4/Zn2SnO4 composite when compared to Zn2SnO4. A rapid decolorization of dye solution was observed at 40 min of reaction using the CoFe2O4/Zn2SnO4 catalyst, being 2.5 times faster than the Zn2SnO4 alone. Therefore, the CoFe2O4/Zn2SnO4 composite shows extraordinarily high photocatalytic activity toward the degradation of rhodamine B dye from aqueous solution.  相似文献   

6.

Purpose

An efficient method was developed for treating polychlorinated biphenyl (PCB)-contaminated soil by soil washing and subsequent TiO2 photocatalytic degradation, and the photocatalytic degradation mechanism of PCBs was explored.

Materials and methods

Hydroxypropyl-??-cyclodextrin (HP??CD) and polyoxyethylene lauryl ether (Brij35) were used to extract PCBs from contaminated soil at first, and then the degradation of PCBs in the soil extracts was performed by TiO2 photocatalysis under UV irradiation.

Results and discussion

Washing conditions including washing time, the concentration of HP??CD/Brij35, and the ratio of soil mass to solution volume for extracting 2,4,4??-trichlorobiphenyl (PCB28) from a PCB28-spiked soil were investigated at first. The results indicated that both HP??CD and Brij35 exhibited good performance. The intermediates of photocatalytic degradation of PCB28 were from its dechlorination and hydroxylation in the HPCD and aqueous solutions, respectively. A field PCB-contaminated soil from e-waste recycling sites was treated by this method. The results showed that the extracting percentage was significantly affected by the chlorination degree of PCBs, and HP??CD slowed down the photocatalytic degradation efficiency of overall PCBs.

Conclusions

Soil washing and subsequent TiO2 photocatalytic degradation was successfully applied for treating PCB-contaminated soil, and HP??CD strongly altered the pathways of the photocatalytic degradation of PCBs.  相似文献   

7.
In this study, photocatalytic degradation of bisphenol A (BPA) was investigated using two types of catalysts (TiO2 and ZnO) with various metal ion concentrations and amounts of added H2O2. A kinetic test was performed to observe the changes of BPA over time under UV irradiation in a photocatalytic reactor. Experimental results demonstrated that degradation efficiency of ZnO was higher than that of TiO2. The degradation rate increased as catalyst dosage increased until reaching optimum dosage, after which degradation rate decreased. The addition of H2O2 improved the degradation efficiency of BPA, with the degradation efficiency increasing with the amount of H2O2. All metal ions, including Fe2+, Ni2+, and Cu2+, inhibited the degradation of BPA by ZnO at natural pH, whereas Fe2+ and Ni2+ enhanced degradation efficiency of BPA at acidic pH. Comparison of BPA degradation with H2O2 only, ZnO/H2O2, Fe2+/H2O2, and ZnO/Fe2+/H2O2 revealed that Fe2+/H2O2 was more efficient than other processes at lower pH (pH?=?3.44), whereas ZnO/H2O2 the most efficient at higher pH (pH?=?6.44). These results indicate that ZnO/H2O2 process was observed to be the most efficient of all processes. Degradation efficiency of BPA by ZnO was also influenced by additional parameters, including H2O2 concentration, metal ions, and solution pH.  相似文献   

8.
In this work, photocatalytic degradation of two reactive dyes, Reactive Yellow 84 (RY 84) and Reactive Black 5 (RB 5), on FeTiO3/TiO2 heterojunction in the presence of UV–visible radiation and H2O2 has been reported. FeTiO3/TiO2 heterojunction has been prepared from ilmenite FeTiO3 and anatase TiO2 by employing oxalic acid as an organic linker. FeTiO3/TiO2 ratios have been varied from 1 to 5 wt.%, and the materials were characterized by X-ray diffraction, scanning electron microscope and diffused reflectance UV–visible spectroscopic analysis. The photocatalytic activity of FeTiO3/TiO2 heterojunction for the degradation of the organic dyes RY 84 and RB 5 in the presence of UV–visible light was found to be higher than that of pure TiO2. The addition of H2O2 increases the rate of degradation of both dyes on FeTiO3/TiO2 heterojunction. It facilitates the fast degradation of dye solutions even when their concentration was above 100 mg/l, which is otherwise very slow due to the low transmittance of light by the dye solution. The extent of mineralisation of the reactive dye during photocatalytic degradation was estimated from chemical oxygen demand analysis. FeTiO3/TiO2 heterojunction photocatalyst was also found to have good photostability; the material retains almost 97 % of its initial activity even in the fifth cycle.  相似文献   

9.
The efficiency of the photocatalytic degradation of the herbicide quinmerac in aqueous TiO2 suspensions was examined as a function of the type of light source, TiO2 loading, pH, temperature, electron acceptors, and hydroxyl radical (?OH) scavenger. The optimum loading of catalyst was found to be 0.25?mg?mL?1 under UV light at pH?7.2, with the apparent activation energy of the reaction being 13.7?kJ?mol?1. In the first stage of the reaction, the photocatalytic degradation of quinmerac (50???M) followed approximately a pseudo-first order kinetics. The most efficient electron acceptor appeared to be H2O2 along with molecular oxygen. By studying the effect of ethanol as an ?OH scavenger, it was shown that the heterogeneous catalysis takes place mainly via ?OH. The results also showed that the disappearance of quinmerac led to the formation of a number of organic intermediates and ionic byproducts, whereas its complete mineralization occurred in about 120?min. The reaction intermediates (7-chloro-3-methylquinoline-5,8-dione, three isomeric phenols hydroxy-7-chloro-3-methylquinoline-8-carboxylic acids, and 7-chloro-3-(hydroxymethyl)quinoline-8-carboxylic acid) were identified and the kinetics of their appearance/disappearance was followed by LC?CESI?CMS/MS. Tentative photodegradation pathways were proposed and discussed. The study also encompassed the effect of quality of natural water on the rate of removal of quinmerac.  相似文献   

10.
This study concentrated on the direct immobilization of anatase nano titanium dioxide particles (TiO2, 44?nm particle size) into or onto a biodegradable polymer, polycaprolactone, by solvent-cast processes. The photocatalytic properties of the produced materials were tested by photocatalytic removal of organic contaminant 4-chlorophenol. Produced TiO2 immobilized polymer successfully removed 4-chlorophenol (4-CP, 20?ppm which is equal to 1.56?×?10?4?M) from aqueous solution without additional pH arrangement employing a UV-A light (365?nm) source. Immobilization of n-TiO2 onto polycaprolactone (PCL) produced improved 4-CP removal percentages, reaching to nearly 85?%. Increased PCL mass significantly increases the removal percentage of 4-CP. When a UVC lamp emitting 254?nm light is used, the removal percentage reaches to 89?%. UV irradiation did not cause any change in the microstructure of the polymeric material (confirmed with ATR-FTIR analysis). This is an important evidence that the material could be reused for further photocatalytic treatments. Produced material seems to be highly promising for successful removal of organic pollutants beside its biodegradable nature.  相似文献   

11.
The present study focused on the degradation of mixed pesticides using UV-induced photocatalytic degradation of lindane (1α,2α,3β,4α,5α,6β-hexachlorocyclohexane), methyl parathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate), and dichlorvos (2,2-dichlorovinyl-O-O-dimethyl phosphate). Different grades of TiO2 were prepared through the acid route (AR), alcohol route (AlR), and surfactant route (SR) and their photocatalytic activity were compared with commercially available Degussa P-25 TiO2. The rate of degradation of pesticides was high for TiO2 prepared through the SR compared to the other three catalysts. The crystalline structure and morphology of SR TiO2 was identified with scanning electron microscope, energy dispersive X-ray analyzer, UV, and transmission electron microscope analyses and was compared with that of Degussa P-25 TiO2. Degradation studies of individual as well as mixed pesticides were carried out. The intermediate formed during the photodegradation of methyl parathion, lindane, and dichlorvos were identified by gas chromatography–mass spectrometry analysis.  相似文献   

12.
该文对TiO2纳米粒子气固光催化降解果蔬贮藏环境乙烯技术进行了初步研究。采用溶胶-凝胶法制备的纳米TiO2薄膜作光催化剂,利用自行设计的气固光催化实验系统,研究了乙烯浓度、紫外光作用时间对光催化降解反应的影响,探讨了乙烯的光催化降解的动力学。结果显示:该研究所制备的TiO2锐钛矿型含量为48.766%,比表面积为47.186 m2/g,具有良好的光催化性能;光催化降解乙烯比直接紫外线光降解效果显著,光照10 min时光催化乙烯降解率比直接紫外线光降解提高23.76%;乙烯的降解率随着其浓度的增加而降低;乙烯的光催化降解的动力学可以用Langmuir-Hinshelwood动力学方程加以描述。  相似文献   

13.
钙和NO对NaCl胁迫下黄瓜幼苗生长和活性氧代谢的影响   总被引:1,自引:0,他引:1  
采用营养液培养的方法,研究了Ca2+对外源一氧化氮(Nitric oxide,NO)所诱导的NaCl胁迫下黄瓜幼苗生长、活性氧代谢的影响。结果表明,添加外源NO或Ca2+显著缓解了NaCl胁迫对黄瓜幼苗生长的抑制,叶片和根系超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性较单独NaCl胁迫处理显著提高,丙二醛(MDA)和过氧化氢(H2O2)的含量、超氧阴离子(O.-2)产生速率明显下降;添加NO的同时添加Ca2+通道抑制剂La3+抑制了NO的这些调节作用。结果表明Ca2+对NO诱导的NaCl胁迫下黄瓜幼苗植株活性氧清除能力的提高起重要作用,NO的作用可能依赖于胞浆Ca2+。  相似文献   

14.
In order to enhance the photocatalytic activity of the TiO2 films, Co surface doped TiO2-SiO2 composite films were synthesized by the improved sol-gel method, in which tetrabutyl titanate (Ti(OC4H9)4) and tetraethyl orthosilicate were chosen as the precursors and cobaltous nitrate hexahydrate (Co(NO3)2·6H2O) was chosen as cobalt source. The field emission scanning electron microscopy and X-ray diffraction results indicated that the films were composed of nanoparticles or aggregates. The photoluminescence results revealed that the recombination rate of the photogenerated electrons and holes was prohibited via SiO2 composite and Co doping in TiO2 film. The Brunauer?CEmmett?CTeller results showed that the surface area of the modified TiO2 was 301.7?m2?g?1, while that of the pure TiO2 was 68.4?m2?g?1. The photocatalytic activities of the films were evaluated by degradation of an organic dye in aqueous solution. With the SiO2 composite and Co doping, the modified TiO2 films with high photocatalytic activity and clearly responsive to the visible light were obtained. The mechanisms of photoactivity enhancement for composite films have also been discussed.  相似文献   

15.
Nanocomposite of CeO2?CSnO2 containing different CeO2 contents was prepared by coprecipitation process. The material obtained was characterized by X-ray diffraction and N2 adsorption?Cdesorption isotherms. Its photocatalytic activity was tested in the degradation of azo dye of leather, Direct Black 38, in aqueous solution under sunlight. The photocatalytic activity of the coupled CeO2?CSnO2 oxide ranged depending on the CeO2 contents. The optimum amount of CeO2 for the synthesis of CeO2?CSnO2 was 7?wt.% since the nanoparticles showed high photocatalytic activity in the degradation of the dye, similar to that of the TiO2?CP25 photocatalyst. The kinetics of photocatalytic degradation and total organic carbon removal under sunlight were found to follow a first-order rate law. The results indicated that CeO2?CSnO2 can be used for the removal of dyes from wastewater.  相似文献   

16.

Purpose

TiO2 photocatalytic degradation of tetracycline (TC) in aqueous solution under UV irradiation was investigated as affected by different environmental factors, including cations, anions, organic acids, and surfactants.

Materials and methods

The solution of TC with TiO2 was irradiated by medium mercury lamp. The concentrations of TC and metal ions were analyzed by HPLC and AAS, respectively. The degradation efficiency of TC was calculated based on TC disappearance.

Results and discussion

Photocatalysis was very effective for TC removal. The degradation efficiency of TC was significantly enhanced in the presence of Cu2+/Pb2+, SO4 2?/Cl?, and humic acid (HA) in the examined range, but did no change with Ni2+, Cd2+, or Zn2+. In addition, the results also showed that solution Cu2+ and Pb2+ ions could be reduced during the process, while Ni2+, Cd2+, and Zn2+ were still kept in the solution. However, tannic acid (TA), gallic acid (GA), citric acid (CA), salicylic acid (SA), hydroxypropyl-β-cyclodextrin (HPCD), polyoxyethylene lauryl ether (Brij35), or polyoxyethylenesorbitan monooleate (Tween80) significantly decreased the degradation efficiency of TC.

Conclusions

The photocatalytic approach could be successfully applied to remove TC, and environmental factors significantly influenced its degradation efficiency. It would be useful to understand the environmental behaviors of TC and for the implementation of remediation strategies of TC.  相似文献   

17.
Photocatalytic methods were applied to remove the recalcitrant or toxic pollutants from the water. The two models of wastewater containing either non-ionic surfactant Triton X-100 or commercially available wash-up liquid were tested in a self-constructed band reactor during the laboratory studies. The photocatalyst, being typed TiO2, was supported by porous Al2O3 and modified by the addition of Cu, Fe, Zn, Ni, Mo or Co. The photocatalysts were characterised by N2 adsorption?Cdesorption, XRF, XRD, SEM-EDX, Raman and UV?CVis spectroscopy. All catalysts were efficient in the photocatalytic oxidation of surfactants, and they enabled at least 85?% COD reduction. TiO2/Al2O3 photocatalysts modified by the transition metals were efficient only for more complicated compositions of surfactants. The effect of H2O2 (0.01?vol.%) addition was also examined and compared with a type of compound and catalyst used??in this case a positive effect for Triton X-100 was only observed over the photocatalyst modified by Ni. When it comes to the wash-up liquid photoremoval, all studied photocatalysts seem to be slightly influenced by H2O2 addition. It was also observed that it is not economically justified to conduct such treatment for more than 2?h.  相似文献   

18.
The present work focused on treatment of eosin (EO) by photocatalysis (PC) combined with electrocatalysis (EC) process. Bismuth oxychloride/titanium dioxide (BiOCl/TiO2) hybrid particles, which were used as new heterogeneous photocatalysts, were exploited in a reverse microemulsion approach and were characterized by XRD, UV?CVis diffuse spectra, BET, and SEM technologies. All degradation experiments were performed using a self-assemble experimental setup, in which PC and EC could be carried out simultaneously or individually. The results indicated that BiOCl/TiO2 showed enhanced photocatalytic performance under UV irradiation, and 50% BiOCl/TiO2 exhibited the best photoactivity due to its high degree of crystallization, the mesoporous structure and corresponding large special surface area, improved absorption ability in UV region, and the heterojunction formed between two coupling particles. The combined degradation process displayed synergistic effect on the degradation of EO owing to the generation of H2O2 at graphite cathode. The parameters such as, pH, reaction current, and initial concentration of EO were monitored in order to optimize the operating conditions. Pseudo-first-order kinetics was proposed and roughly fitted the combined degradation of EO. The combined system in this work suggested a new research idea for the degradation of dye wastewater.  相似文献   

19.
Photocatalytic reduction of CO2 in seawater into chemical fuel, methanol (CH3OH), was achieved over Cu/C-co-doped TiO2 nanoparticles under UV and natural sunlight. Photocatalysts with different Cu loadings (0, 0.5, 1, 3, 5, and 7 wt%) were synthesized by the sol–gel method and were characterized by XRD, SEM, UV–Vis, FTIR, and XPS. Co-doping with C and Cu into TiO2 remarkably promoted the photocatalytic production of CH3OH. This improvement was attributed to lowering of bandgap energy, specific catalytic effect of Cu for CH3OH formation, and the minimization of photo-generated carrier recombination. Co-doped TiO2 with 3.0 wt% Cu was found to be the most active catalyst, giving a maximum methanol yield rate of 577 μmol g-cat?1 h?1 under illumination of UV light, which is 5.3-fold higher than the production rate over C-TiO2 and 7.4 times the amount produced using Degussa P25 TiO2. Under natural sunlight, the maximum rate of the photocatalytic production of CH3OH using 3.0 wt% Cu/C-TiO2 was found to be 188 μmol g-cat?1 h?1, which is 2.24 times higher than that of C-TiO2, whereas, no CH3OH was observed for P25.  相似文献   

20.
In this investigation, the photocatalytic activity of α-Bi4V2O11 in the degradation of 2-naphthol under simulated solar light was evaluated. Bismuth vanadate α-Bi4V2O11 was synthesized by the solid-state reaction method and by co-precipitation in aqueous media, with the aim of comparing their performance in the photodegradation of the aromatic pollutant. The latter method (co-precipitation) has not been previously reported for the synthesis of α-Bi4V2O11. Structural evolution of the oxides precursors was determined by X-ray diffraction. Morphology and optical properties of the solids were analyzed by scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (UV-vis), respectively. The results showed that at 800 °C, only α-Bi4V2O11 was formed in both preparations. The SEM micrographs revealed that the powders were composed of agglomerates with sizes between 0.8–2 μm for those synthesized by co-precipitation and 2–10 μm for those obtained by solid-state reaction. The optical properties indicated that α-Bi4V2O11 was activated with visible light during the photocatalytic process. The photocatalytic degradation of 2-naphthol was largely influenced at basic pH, degrading 79% of the contaminant in 240 min, with the powder obtained by co-precipitation; meanwhile, for the solid-state preparation, the degradation reached only 55%.  相似文献   

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