Titanium dioxide mediated photocatalytic degradation of 17beta-estradiol in aqueous solution

Photocatalytic degradation of 17beta-estradiol (E2) in aqueous medium mediated with titanium dioxide (TiO(2)) was studied. Moreover, effect of TiO(2) dosage on the degradation efficiency was investigated. Particular attention was paid to the identification of intermediates and analysis of photocatalytic degradation mechanism of E2 under neutral and alkaline conditions. The degradation efficiency of E2 increased with increasing concentration of TiO(2) but decreased due to light scattering as TiO(2) concentration was greater than 0.5mgml(-1). Several intermediates were formed during photocatalytic degradation of E2. However, only a few of the compounds could be identified and confirmed by LC-MS and LC-MS/MS. Six intermediates were observed by photocatalytic oxidation under alkaline conditions, namely 2-hydroxyestradiol, 10epsilon-17beta-dihydroxy-1,4-estradien-3-one (DEO), 10epsilon-hydroperoxide-17beta-hydroxy-1,4-estradien-3-one and three kinds of dicarboxylic acids formed by the opening of aromatic ring. In addition to the six intermediates mentioned above, 17beta-hydroxy-1,4-estradien-3-one (EO) was observed under neutral conditions and in the presence of methanol. Based on these intermediates, which were hardly degraded even after E2 was fully degraded, the mechanism of E2 degradation by TiO(2) photocatalysis was elucidated.     

Heterogeneous photocatalytic degradation of picloram, dicamba, and floumeturon in aqueous suspensions of titanium dioxide

Heterogeneous photocatalytic degradation of three-selected herbicide derivatives: (1) picloram (4-Amino-3,5,6-trichloropyridine-2-carboxylic acid, (2) dicamba (2-Methoxy-3,6-dichlorobenzoic acid, and (3) floumeturon (N,N-Dimethyl-N-[3-(trifluoromethyl)phenyl]-urea) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique and decrease in total organic carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the herbicide was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO2, and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3), and ammonium persulphate (NH4)2S2O8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts in the case of dicamba (2) and floumeturon (3), whereas Hombikat UV100 was found to be better for the degradation of picloram (1). The herbicide picloram (1) was found to degrade faster as compared to dicamba (2) and floumeturon (3). The degradation products were analyzed by gas chromatography-mass spectrometry (GC/MS) technique, and plausible mechanisms for the formation of products have been proposed.     

日光下黄砂负载TiO2降解邻氯苯酚水溶液

研究了以黄砂为载体,ＴｉＯ２为催化剂,以太阳光为光源对邻氯苯酚水溶液进行光催化降解的可行性。结果表明,锐钛型ＴｉＯ２邓邻氯苯酚有显著的光催化降解作用;ＴｉＯ２的催化活性在焙烧温度３００℃时最高。     

纳米TiO2改性可见光催化降解有机物研究进展

光催化降解水中有机污染物是一项颇有发展前途的废水处理技术.目前主要的研究工作由紫外光逐步向可见光催化方向发展,使这项技术向实用性又迈进了一步.系统介绍了纳米TiO2的光催化降解有机污染物的原理,光催化处理水的现状,并从离子掺杂、表面光敏化和分子筛负载几个方面综述了可见光化的研究现状和发展方向.     

Semiconductor-assisted photocatalytic degradation of reactive dyes in aqueous solution

This work reports the semiconductor-assisted photochemical degradation of reactive dyes. In an oxygenated-UV-ZnO system almost total decolorization of Remazol Brilliant Blue R, Remazol Black B, Reactive Blue 221 and Reactive Blue 222 was observed in reaction times of about 60 min. Extending the photochemical treatment up to 120 min, mineralization higher than 80% for all the dyes was observed. During the same period, the residual acute toxicity was significantly reduced only for Remazol Black B. A systematic optimization study carried out by factorial design showed that for the reactive dyes tested, the ZnO semiconductor exhibits a better efficiency than that observed with anatase TiO2. A synergistic effect in the coupled TiO2-ZnO system was not observed.     

Application of titanium dioxide immobilized on a cellulosic material for the photocatalytic degradation of Acid Black 24 dye in a continuous flow cascade reactor

Environmental Science and Pollution Research - The aim of this work is the study of the photocatalytic degradation of Acid Black 24 dye (AB24), in a continuous flow cascade reactor, using titanium...     

TiO2/EP光催化降解水体中微污染磺胺嘧啶的研究

制备了膨胀珍珠岩（EP）为载体的TiO2催化剂（TiO2/EP）,对使用较为广泛的抗生素磺胺嘧啶（SDZ）进行了光催化降解研究,探讨了TiO2的负载量、溶液的初始浓度、初始pH、无机离子（HCO3^-、SO4^2-和Cl^-）和腐殖酸（HA）对SDZ降解效果的影响。结果表明：SDZ的光催化降解符合一级反应动力学方程;当TiO2最佳负载量为20 wt%,SDZ浓度为5 mg/L,pH=6.7,紫外光照射强度为1 000μW/cm^2,反应时间为45 min时,SDZ的降解率达到96%;HCO3^-在低浓度时能促进SDZ的光催化降解,高浓度时促进作用不明显;SO4^2-和Cl^-对SDZ的光催化降解有轻微的抑制作用;HA对SDZ光催化降解有显著的抑制作用,浓度越高,抑制作用越强。UV-TiO2/EP是一种去除水体中微污染SDZ的有效方法。     

Photocatalytic degradation of amoxicillin from aqueous solutions by titanium dioxide nanoparticles loaded on graphene oxide

Environmental Science and Pollution Research - The photocatalytic degradation of amoxicillin (AMX) by titanium dioxide nanoparticles loaded on graphene oxide (GO/TiO2) was evaluated under UV light....     

ZnIn2S4光催化降解水中痕量药物卡马西平的特性

采用水热合成法制备光催化剂ZnIn2S4,考察其光催化降解水中痕量医药类物质卡马西平的特性。研究表明,卡马西平初始浓度100 μg·L-1、溶液pH 5~9、ZnIn2S4投加量50 mg·L-1与碘镓灯（350~450 nm）光照反应3 h后,卡马西平的去除率为90%。动力学分析表明,卡马西平的光催化降解符合一级反应动力学,添加催化剂时的反应速率常数是不加催化剂的2.85倍,催化剂明显提高了降解反应速率。催化剂循环使用2个周期后,卡马西平的去除率由90%降至70%并保持稳定,表明催化剂结构趋稳后仍具有较高的催化活性。羟基自由基（·OH）实验证实了卡马西平降解过程中·OH为主要活性物种,但卡马西平的矿化率却只有3%,由于反应后的溶液呈酸性,因此推测光催化过程中卡马西平与·OH作用后大都转化为酸性中间产物而未被彻底氧化。     

微波诱导改性活性炭催化降解邻苯二甲酸二甲酯

通过HNO3、H2O2、NaOH对活性炭进行浸渍改性,采用BET、SEM、Boehm、FT-IR对改性前后的活性炭进行表征,研究了改性前后的活性炭在不同反应体系对DMP的降解效果和动力学,探讨了微波诱导改性前后的活性炭催化降解DMP的机理。结果表明,3种改性活性炭的BET比表面积、总孔容、微孔孔容和平均孔径均有所增加。HNO3、H2O2改性后表面酸性基团增加、碱性基团减少,而NaOH改性呈现相反的理化特征变化。活性炭理化特征的变化可能与化学改性剂溶液的酸碱性、氧化还原性有关。微波诱导改性前后的活性炭催化体系对DMP的降解率大于单独吸附或单纯微波辐射体系,且均符合一级反应动力学。在微波诱导改性前后的活性炭催化体系中,改性前后的活性炭通过表面吸附-微波诱导氧化协同作用极大地提高了对DMP的降解率。     

海藻酸钠微胶囊负载纳米铁吸附水中的As(Ⅴ)

利用本实验所制备的海藻酸钠微胶囊负载纳米零价铁材料(M-NZVI)对水中不同浓度的As(V)进行了吸附去除研究,并比较了不同材料的吸附等温曲线。实验结果表明,2 g/L M-NZVI在pH=6.5±0.1,常温常压条件下对5 mg/L的As(V)的吸附去除率为90.35%,吸附速率较快,在30 min即可达到吸附平衡。通过M-NZVI、Ca-ALG和NZVI的热力学对比实验可知,M-NZVI表现出优越的吸附性能。溶液吸附剂添加量、初始pH值、离子浓度等因素对M-NZVI吸附水中砷离子的效率有一定影响:在其他条件不变的情况下,As(V)的去除率随着添加量的增加而逐渐增大;M-NZVI对As(V)的最佳吸附效果在pH=6~7范围之间;溶液中高浓度NaCl能对M-NZVI的吸附性产生较强的干扰。同时,对于As(V) ≤ 5 mg/L的溶液,M-NZVI可以不做任何处理多次利用3~4次。这些结果显示,M-NZVI是一种用于原位修复重金属污染水体的潜在理想材料。     

Cyclodextrin inclusion: catalytic effects on the degradation of organophosphorus pesticides in neutral aqueous solution.

alpha-, beta and gamma-Cyclodextrins were found to have promotive inclusion-catalytic effects on the degradation of organophosphorus pesticides solubilized in neutral aqueous media. Pesticide degradations were especially accelerated in such systems as alpha-cyclodextrin plus diazinon and beta-cyclodextrin plus chloropyrifos. The above findings are in contrast with the inhibitive catalytic effects of cyclodextrins on pesticide degradations in alkaline media. Cyclodextrin catalytic effects found here were considerably affected by differences in the substitutional and hetero-cyclic properties of the aromatic rings of pesticides and also by the sizes of cyclodextrin cavities.     

TiO_2/EP光催化降解水体中微污染磺胺嘧啶的研究

制备了膨胀珍珠岩(EP)为载体的TiO2催化剂(TiO2/EP),对使用较为广泛的抗生素磺胺嘧啶(SDZ)进行了光催化降解研究,探讨了TiO2的负载量、溶液的初始浓度、初始pH、无机离子(HCO3-、SO42-和Cl-)和腐殖酸(HA)对SDZ降解效果的影响。结果表明:SDZ的光催化降解符合一级反应动力学方程;当TiO2最佳负载量为20 wt%,SDZ浓度为5 mg/L,pH=6.7,紫外光照射强度为1 000μW/cm2,反应时间为45 min时,SDZ的降解率达到96%;HCO3-在低浓度时能促进SDZ的光催化降解,高浓度时促进作用不明显;SO42-和Cl-对SDZ的光催化降解有轻微的抑制作用;HA对SDZ光催化降解有显著的抑制作用,浓度越高,抑制作用越强。UV-TiO2/EP是一种去除水体中微污染SDZ的有效方法。     

微波辅助光催化降解水中酚的研究

利用改装的家用微波炉和自制的无电极灯（EDL）试验了5种酚在水溶液中的微波辅助光催化降解效果.结果表明,反应30 min,微波辅助光催化作用（MW/EDL/TiO2）能去除80%以上的苯酚、间硝基苯酚、对氯苯酚和对甲酚,相应溶液的总有机碳（TOC）均减少70%以上,2-萘酚的去除率为59%,溶液TOC减少54%;微波（MW或MW/TiO2）作用对酚的去除率有一定贡献;对上述5种酚的微波辅助光催化反应动力学进行了初步研究,发现均符合准一级动力学方程.     

微波辅助光催化降解水中酚的研究

利用改装的家用微波炉和自制的无电极灯(EDL)试验了5种酚在水溶液中的微波辅助光催化降解效果.结果表明,反应30 min,微波辅助光催化作用(MW/EDL/TiO2)能去除80%以上的苯酚、间硝基苯酚、对氯苯酚和对甲酚,相应溶液的总有机碳(TOC)均减少70%以上,2-萘酚的去除率为59%,溶液TOC减少54%;微波(MW或MW/TiO2)作用对酚的去除率有一定贡献;对上述5种酚的微波辅助光催化反应动力学进行了初步研究,发现均符合准一级动力学方程.     

Photodegradation of Diquat and Paraquat in aqueous solutions by titanium dioxide: evolution of degradation reactions and characterisation of intermediates

The titanium dioxide assisted photodegradation of Diquat and Paraquat herbicides solutions has been the subject of the present investigation, considering its direct application in the treatment of contaminated waters and soils. To have a better understanding of the photodegradation process, different types of TiO2, commercial and 'home prepared' Ti(1-x)FexO2 (x = 0% and 4%), were used as catalysts, using an UV light as radiation source. The degradation reactions were followed by UV spectroscopy and the intermediates and reaction products were characterised by electrospray ionisation mass spectrometry (ESIMS) combined with collision-induced dissociation (CID) and tandem mass spectrometry (MS/MS). The present study shows that, for photocatalytic degradation of Diquat and Paraquat solutions, a basic pH can be determinant, as well as the type of catalyst. The type of catalyst can also strongly influence the degradation pattern of the herbicide. Regarding complete degradation, we were able to show that Diquat is more persistent than Paraquat. During the photocatalytic processes, several intermediate and reaction products are sequentially formed, to which structures are proposed.     

Formation of mutagens by photolysis of amino acids in neutral aqueous solution containing nitrite or nitrate ion

Nine amino acids, i.e., alanine, threonine, cysteine, glutamic acid, arginine, proline, tryptophan, phenylalanine and tyrosine, were irradiated with UV light in water containing nitrite or nitrate ion under neutral conditions. The mutagenicities of the ether extracts and the residual water layers of the reaction mixtures were assayed with and without S-9 mix using $\text{Salmonella typhimurium}$ TA98 and TA100. Three aromatic amino acids, tryptophan, phenylalanine and tyrosine, were found to give direct-acting and frameshift mutagens by irradiation in aqueous nitrite solution. Among them, the ether extract of tryptophan exhibited the strongest mutagenicity toward TA98. In the case of irradiation in aqueous nitrate solution, only the ether extract of tryptophan exhibited weak mutagenicity toward TA98 without S-9 mix. The effects of nitrite concentration, irradiation time and pH on mutagen formation from tryptophan and some characteristics of the produced mutagens were examined.     

Degradation of diuron in aqueous solution by ozonation

Degradation of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] in aqueous solution and the proposed degradation mechanism of diuron by ozonation were investigated. The factors that affect the degradation efficiency of diuron were examined. The generated inorganic ions and organic acids during the ozonation process were detected. Total organic carbon removal rate and the amount of the released Cl^? increased with increasing ozonation time, but only 80.0% of the maximum theoretical concentration of Cl^? at total mineralization was detected when initial diuron concentration was 13.8 mg L^?1. For N species, the final concentrations of NO₃ ^? and NH₄ ⁺ after 60 min of reaction time were 0.28 and 0.19 mg L^?1, respectively. The generated acetic acid, formic acid and oxalic acid were detected during the reaction process. The main degradation pathway of diuron by ozonation involved a series of dechlorination-hydroxylation, dealkylation and oxidative opening of the aromatic ring processes, leading to small organic species and inorganic species. The degradation efficiency of diuron increased with decreasing initial diuron concentration. Higher pH value, more ozone dosage, additive Na₂CO₃, additive NaHCO₃ and additive H₂O₂ were all advantageous to improve the degradation efficiency of diuron.     

采用杂多酸化合物溶液同时脱硫脱氮的实验研究

本文对液相催化氧化脱硫脱氮的新方法进行了研究 ,在鼓泡反应发生器内进行了液相催化氧化脱硫脱氮的实验。采用钼硅酸溶液及其还原产物脱除烟气中的SO2 和NOX,分别就吸收液的浓度、pH值、温度、停留时间等因素对SO2 和NOX 去除效率的影响及其变化规律进行了研究。实验结果表明 ,钼硅酸能十分有效地吸收SO2 ,将SO2 氧化成H2 SO4,并使杂多酸还原为杂多蓝。随后又被用于去除NOX,把NOX 还原成N2 ,蓝色溶液再次被氧化成为黄色溶液     

Continuous monitoring of photocatalytic treatments by flow injection. Degradation of dicamba in aqueous TiO2 dispersions.

The possible use of flow injection (FI) to monitor the photocatalytic mineralization of dicamba (3,6-dichloro-2-methoxybenzoic acid) present at the trace level in aqueous solutions containing TiO2 suspensions has been evaluated. Experiments were performed in a stirred photochemical reactor equipped with a simple FI manifold, integrating an online filtration unit able to perform the monitoring of the UV absorbance of the irradiated solution every 4 min. The light source used was a medium pressure mercury lamp (125 W). During the initial steps of the reaction the formation of UV absorbing intermediates, which completely disappear in less than 80 min, was evidenced. Additional HPLC, DOC and chloride ion measurements carried out on manually taken samples confirmed the complete mineralization of dicamba within about 90 min. The proposed on-line monitoring looks particularly suitable for the control of degradation treatments where primary degradation and mineralization steps take place after a comparable irradiation time.