Removal of metronidazole and amoxicillin mixtures by UV/TiO2 photocatalysis: an insight into degradation pathways and performance improvement

Environmental Science and Pollution Research - The degradation efficiencies and pathways of metronidazole (MNZ) and amoxicillin (AMX) in binary mixtures by UV/TiO2 photocatalysis were studied. The...     

Fe/TiO2光催化降解水溶液中的4-氯苯酚

以TiO2-P25及FeC2O4为前驱物制备了Fe3 掺杂TiO2光催化剂--Fe/TiO2.X射线衍射结果表明,500 ℃煅烧温度下的Fe/TiO2主要是锐态矿晶型,当掺Fe3 量为0.5%(质量分数,下同)时,Fe3 以取代掺杂形式进入TiO2晶格,而当掺Fe3 量达5.0%时,则出现α-Fe2O3的特征衍射峰;900 ℃煅烧温度下的Fe/TiO2则均为金红石晶型,掺Fe3 量达2.0%～5.0%时,出现Fe2TiO5的特征衍射峰.4-氯苯酚的光催化实验结果表明,煅烧温度及Fe3 掺杂量对Fe/TiO2的光催化活性有显著影响,以煅烧温度500 ℃及掺Fe3 量0.5%的Fe/TiO2为光催化剂,反应80 min,4-氯苯酚的降解率达100%,总有机碳去除率约95%.     

Decolorizing of lignin wastewater using the photochemical UV/TiO2 process

Studies on applying the photochemical UV/TiO2 oxidation process to treat the lignin-containing wastewater for dissolved organic carbon (DOC), color and reducing A254 (the absorption at the wavelength of 254 nm) have been carried out. The data obtained in this study demonstrate that the UV/TiO2 process is effective in oxidizing the lignin thus reducing the color and DOC of the wastewater treated. The combined UV/TiO2 treatment can achieve better removal of DOC and color than the UV treatment alone. Color removal, based on American Dye Manufacture Index (ADMI) measurement, is greater than 99% if the pH is maintained at 3.0 with the addition of 1 g l(-1) TiO2. When 10 g l(-1) TiO2 is applied, the oxidation reduction potential (ORP) value is reached to result in an 88% removal of both DOC and color. A model was developed based on the variation of ORP during the photochemical reaction to simulate the decoloring process. The proposed model can be used to predict the color removal efficiency of the UV/TiO2 process.     

Degradation of short-chain alkyl- and alkanolamines by TiO2- and Pt/TiO2-assisted photocatalysis

The photooxidation of C2H5NH2, (C2H5)2NH, HOC2H4NH2, (HOC2H4)2NH and (HOC2H4)3N using TiO2 and Pt/TiO2 as photocatalysts has been investigated. A laboratory set up was designed and a study on the influence of the concentration of the photocatalyst, the pH-value and the structure of the amine performed. The photocatalytic process was optimized with respect to the concentrations of the model substances during degradation. The decrease of the amine concentrations was found to be maximum at a pH of 10. The time-dependence of the formation of cationic breakdown products, such as NH3/NH4 and short-chain alkyl- and alkanolamines was studied by analyses with single column ion chromatography. The experimental data show that the photodegradation follows a Langmuir-Hinshelwood kinetic. The mineralization of the model substances also was monitored by measurements of the decrease of the TOC and of the formation of NO2 and NO3. The different mineralization efficiencies for the model substances studied are discussed with regard to their structure and adsorption behaviour on the photocatalyst. A possible breakdown mechanism involving the electrophilic attack of the hydroxyl radical is given. The applicability of the TiO2-assisted photocatalytic degradation of C2H5NH2 and (C2H5)2NH was tested at the pilot plant-scale with real solar radiation. The degradation rates and products obtained were similar to those found in the laboratory experiments.     

TiO2/H2O2/UV和TiO2/O3/UV降解对氯苯甲酸和喹啉的试验研究

主要叙述TiO2/H2O2/UV和TiO2/O3/UV体系降解对氯苯甲酸(4-CBA)和喹啉的试验研究.研究表明,(1)在TiO2/H2O2/UV体系里目标物降解速度先随过氧化氢投加量的增加而提高,但超过一定浓度之后便开始下降;(2)在TiO2/O3/UV体系中,目标降解物的反应速度都非常快,且臭氧浓度高的时候降解速度更快;(3)二氧化钛催化剂在TiO2/O3/UV体系中作为积极因素有助于提高反应速率,而在TiO2/H2O2/UV体系是消极因素,会降低反应速率.     

TiO2/H2O2/UV和TiO2/O3/UV降解对氯苯甲酸和喹啉的试验研究

主要叙述TiO2/H2O2/UV和TiO2/O3/UV体系降解对氯苯甲酸（4-CBA）和喹啉的试验研究.研究表明,（1）在TiO2/H2O2/UV体系里目标物降解速度先随过氧化氢投加量的增加而提高,但超过一定浓度之后便开始下降;（2）在TiO2/O3/UV体系中,目标降解物的反应速度都非常快,且臭氧浓度高的时候降解速度更快;（3）二氧化钛催化剂在TiO2/O3/UV体系中作为积极因素有助于提高反应速率,而在TiO2/H2O2/UV体系是消极因素,会降低反应速率.     

Simultaneous decontamination of hexavalent chromium and methyl tert-butyl ether by UV/TiO2 process

Hexavalent chromium and methyl tert-butyl ether (MTBE) are two important environmental pollutants. Simultaneous decontamination of Cr(VI) and MTBE was studied by UV/TiO2 process. The influences of pH and the concentrations of pollutants on the kinetics of the photocatalytic reactions were evaluated. Dark adsorption tests showed that the acidic pH favored the adsorption of Cr(VI) while neutral pH favored the adsorption of MTBE. Under UV irradiation, Cr(VI) reduction was observed in Cr(VI)/TiO2 system, and MTBE oxidation was observed in MTBE/TiO2 system. The system containing Cr(VI) and MTBE by UV/TiO2 process demonstrated the synergistic effect between oxidation of MTBE and reduction of Cr(VI). The results demonstrated that two pollutants Cr(VI) and MTBE could be eliminated simultaneously by UV/TiO2 process. tert-Butyl formate, tert-butyl alcohol and acetone were identified as primary degradation products of MTBE by gas chromatography-mass spectrometry in the degradation of MTBE by UV/TiO2 process.     

Decomposition of gas-phase trichloroethene by the UV/TiO2 process in the presence of ozone.

The decomposition of gas-phase trichloroethene (TCE) in air streams by direct photolysis, the UV/TiO2 and UV/O3 processes was studied. The experiments were carried out under various UV light intensities and wavelengths, ozone dosages, and initial concentrations of TCE to investigate and compare the removal efficiency of the pollutant. For UV/TiO2 process, the individual contribution to the decomposition of TCE by direct photolysis and hydroxyl radicals destruction was differentiated to discuss the quantum efficiency with 254 and 365 nm UV lamps. The removal of gaseous TCE was found to reduce by UV/TiO2 process in the presence of ozone possibly because of the ozone molecules could scavenge hydroxyl radicals produced from the excitation of TiO2 by UV radiation to inhibit the decomposition of TCE. A photoreactor design equation for the decomposition of gaseous TCE by the UV/TiO2 process in air streams was developed by combining the continuity equation of the pollutant and the surface catalysis reaction rate expression. By the proposed design scheme, the temporal distribution of TCE at various operation conditions by the UV/TiO2 process can be well modeled.     

Degradation of bisphenol A by the UV/H2O2 process: a kinetic study

A theoretical and experimental study of bisphenol A (BPA) degradation by the UV/H₂O₂ process in water is presented. The effects of the H₂O₂ concentration and the specific rate of photon emission (E_P,0) on BPA degradation were investigated. A kinetic model derived from a reaction sequence was employed to predict BPA and hydrogen peroxide concentrations over time using an annular photochemical reactor in batch recirculation mode. The local volumetric rate of photon absorption (LVRPA) inside the photoreactor was computed using a Line Source with Parallel Plane emission model (LSPP). From the proposed kinetic model and the experimental data, the second order rate constants of the reactions between hydroxyl radicals and the main reacting species (H₂O₂ and BPA) were estimated applying a nonlinear regression method. A good agreement between the kinetic model and experimental data, for a wide range of operating conditions, was obtained. For BPA, H₂O₂, and TOC concentrations, the calculated root means square errors (RMSE) were 2.3?×?10^??2, 9.8?×?10^??1, and 9.0?×?10^??2 mmol L^??1, respectively. The simplified kinetic model presented in this work can be directly applied to scaling-up and reactor design, since the estimated kinetic constants are independent of the reactor size, shape, and configuration. Further experiments were made by employing low BPA initial concentration (100 μg L^??1) in water and real wastewater. A lower degradation rate of BPA was observed in the real wastewater, although the UV/H₂O₂ process has also been able to completely degrade the target pollutant in less than 1 h.

     

The direct photolysis and photocatalytic degradation of alachlor at different TiO2 and UV sources

Direct photolysis and photocatalytic degradations of alachlor, a widely used herbicide, were studied using three different monochromatic UV lamps (254, 300 and 350 nm) and two TiO(2) sources. Both the direct photolysis and photocatalytic degradations of alachlor follow pseudo-first-order decay kinetics. TiO(2)-P25 was found to be an effective photocatalyst compared to TiO(2)-BDH. The direct photolysis of alachlor was dominant at 254 nm even if TiO(2) was present in the solution. Among the three UV wavelengths used, the highest photocatalysis quantum yield was obtained at 300 nm. The photocatalytic degradation rate of alachlor increased with the dosages of TiO(2), but an overdose of TiO(2) would retard the reaction due to light attenuation. Photocatalytic reactions were slightly enhanced in an alkaline medium, and the different proton sources causing various degrees of rate retardation were due to the presence of the corresponding counter anions. This effect was diminished at a later stage after the reaction intermediates were formed.     

臭氧与TiO2/UV协同降解对氯苯酚

利用O3／UV、TiO2／UV和O3／TiO2／UV降解对氯苯酚表明，臭氧与TiO2／UV具有明显的协同作用，如在本实验条件下降解5min后，上述3者对对氯苯酚的去除率分别为55％、10％和77%。O3／TiO2／UV协同作用的本质是由于臭氧能带走二氧化钛光致电子空穴对中的电子，从而产生了更多的羟基自由基，加速了有机物的降解。     

复合纳米Fe2O3/TiO2可见光催化降解邻甲酚溶液的研究

以复合纳米Fe2O3／TiO2作为催化剂,日光色镝灯为光源,研究了邻甲酚溶液的可见光降解。考察了催化剂制备方法、催化剂使用量、溶液pH、催化剂重复使用等条件对可见光降解的影响。实验结果表明,1％Fe2O3／TiO2（n）对邻甲酚溶液的可见光降解效果最优,比Ti02（p25）的降解率提高了2．6倍。在实验条件下,可见光降解3h,邻甲酚溶液的浓度去除率达95．4％,TOC去除率为72．3％。在较宽的浓度范围内,邻甲酚的反应服从一级动力学反应方程,随着浓度的增大,反应速率常数不断降低。     

UV/H2O2工艺降解环丙沙星的研究

采用UV/H2O2工艺去除水体中的喹诺酮类抗生素环丙沙星（CIP）。考察了溶液pH值、H2O2投加量以及水体基质对环丙沙星降解效率的影响,分析了降解产物的生成情况。研究表明,环丙沙星的降解符合拟一级反应动力学模型。降解速率受溶液pH值的影响,酸性及中性条件,有利于环丙沙星的降解。H2O2投加量的增大,使得降解速率逐渐增大,但速率增幅逐渐变缓;最佳H2O2/环丙沙星摩尔比为2 000。实际水体中存在的NOM、NO3-,促进了单独UV作用下,环丙沙星的降解。水体中的.OH焠灭剂,抑制了UV/H2O2联合作用下,环丙沙星的降解;实际水体中的光解速率常数低于超纯水中的光解速率常数。GC-MS分析表明,UV/H2O2工艺,使环丙沙星氧化降解生成氨基乙酸、丙二酸、丙三醇和对苯二甲酸等小分子有机物。     

V/Ce共掺杂TiO2光催化降解甲醛的实验研究

采用溶胶-凝胶法制备了不掺杂、V掺杂、Ce掺杂、V/Ce共掺杂纳米TiO2光催化剂,并将其分别负载于瓷砖上,利用X射线衍射分析（XRD）和扫描电镜分析（SEM）技术对薄膜样品的结构和形貌进行了表征。通过对甲醛的降解实验评价光催化剂的光催化活性。实验结果表明,光催化剂的负载量、共掺杂离子的掺杂量、掺杂配比、煅烧温度影响纳米TiO2的光催化活性。V/Ce共掺杂TiO2光催化剂产生了协同效应,其光催化活性优于纯TiO2和单掺杂TiO2样品。     

UV／TiO2薄膜体系光降解酞酸酯研究

采用自制玻璃负载TiO2薄膜，研究了UV-Vis／TiO2以及UV／TiO2／H2O2体系对2种酞酸酯DBP和DEHP的光催化降解情况。研究结果表明，TiO2在暗处对酞酸酯没有降解作用；UV／TiO2体系能有效光降解DBP和DEHP，TiO2具有明显的光催化作用，增强因子分别为，fDBP=2．06，fDEHP=1．53；在一定浓度范围内DBP在UV／TiO2体系中的降解速率与其初始浓度成负一级动力学关系；UV／TiO2／H2O2体系对DBP的光降解能力远大于UV／TiO2和UV／H2O2体系，H2O2能显著提高TiO2的光催化活性。     

UV/TiO2薄膜体系光降解酞酸酯研究

采用自制玻璃负载TiO2薄膜,研究了UV-V is/TiO2以及UV/TiO2/H2O2体系对2种酞酸酯DBP和DEHP的光催化降解情况。研究结果表明,TiO2在暗处对酞酸酯没有降解作用;UV/TiO2体系能有效光降解DBP和DEHP,TiO2具有明显的光催化作用,增强因子分别为fDBP=2.06,fDEHP=1.53;在一定浓度范围内DBP在UV/TiO2体系中的降解速率与其初始浓度成负一级动力学关系;UV/TiO2/H2O2体系对DBP的光降解能力远大于UV/TiO2和UV/H2O2体系,H2O2能显著提高TiO2的光催化活性。     

Evaluation of UV/TiO(2) and UV/ZnO photocatalytic systems coupled to a biological process for the treatment of bleaching pulp mill effluent

This paper presents an exploratory study of pulp mill bleaching effluent treatment by a biological-photocatalytic coupled system. A fungus, Trametes pubescens, immobilized on polyurethane foam was used to inoculate the biological pre-treatment system. The pretreated effluent was then exposed to a photocatalytic treatment in which two catalysts (TiO₂ and ZnO) and two supports (aluminum foil and Luffa cylindrica) were tested. Catalyst characterization was carried out by means of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Information about crystalline structure, chemical composition, morphology, homogeneity and distribution on the support surface area was obtained. The overall biological-photocatalytic coupled system achieved degradation of 96% of initial total organic carbon (TOC), 97% of 2-chlorophenol (2-CP), 90% of 2,4-dichlorophenol (2,4-CP) and 99% of 2,4,6-trichlorophenol (2,4,6-TCP). This approach of synergistic coupling of T. pubescens and a semiconductor photocatalyst appears to be a viable alternative for the treatment of these non-biodegradable effluents.     

臭氧光催化降解地下水中天然有机物的研究

在现场开展了中试规模的臭氧光催化降解天然有机物的研究。研究表明，对大分子天然有机物占很大比例且重碳酸盐含量较高的地下水，臭氧投加量10mg／L和反应时间10min条件下，TOC的去除率不到20％，但uV254和三卤甲烷生成潜力（THMFP）去除率分别达到近60％和33．5％。臭氧光催化与活性炭吸附相连，能显著提高UV254的THMFP的去除率，但TOC去除率并不明显高于单独活性炭吸附。臭氧光催化使大分子有机物转化为小分子有机物，后者在活性炭上的吸附性提高且生化性改善，可望在生物活性炭上更有效地去除。     

Treatment of phenylmercury salts by heterogeneous photocatalysis over TiO(2)

UV/TiO(2) photocatalysis of phenylmercury salts in aqueous solutions has been performed starting from both acetate (C(6)H(5)HgCH(3)CO(2), PMA) and chloride (C(6)H(5)HgCl, PMC) salts, in the presence or the absence of oxygen at acidic pH. Removal of Hg(II) in solution took place with the simultaneous deposit of dark or pale gray solids on the photocatalyst, identified as metallic Hg (when starting from PMA) or mixtures of Hg(0) and Hg(2)Cl(2) (when starting from PMC). Partial mineralization of the organic part of both compounds has also been achieved. Hg(II) removal and mineralization were enhanced in the absence of oxygen. PMA photocatalysis followed a saturation kinetics, going from first order at low concentration to zero order at higher concentrations (>0.5mM). For PMA, reaction was faster at high pH (11) with formation of mixtures of Hg and HgO. Phenol was detected as a product of the reaction in both cases, PMA and PMC, and no formation of dangerous methyl- or ethylmercury species was observed in the first case. A mechanism for the photocatalytic reaction has been proposed. The fact that calomel was found as a deposit when starting from PMC under nitrogen suggests that the mechanism of Hg(II) transformation proceeds through successive one-electron transfer reactions passing by mercurous forms.     

臭氧光催化降解地下水中天然有机物的研究

在现场开展了中试规模的臭氧光催化降解天然有机物的研究.研究表明,对大分子天然有机物占很大比例且重碳酸盐含量较高的地下水,臭氧投加量10 mg/L和反应时间10 min条件下,TOC的去除率不到20%,但UV254和三卤甲烷生成潜力(THMFP)去除率分别达到近60%和33.5%.臭氧光催化与活性炭吸附相连,能显著提高UV254的THMFP的去除率,但TOC去除率并不明显高于单独活性炭吸附.臭氧光催化使大分子有机物转化为小分子有机物,后者在活性炭上的吸附性提高且生化性改善,可望在生物活性炭上更有效地去除.