The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Vanessa J. Pereira - One of the best experts on this subject based on the ideXlab platform.
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Integration of nanofiltration, UV Photolysis, and advanced oxidation processes for the removal of hormones from surface water sources
Separation and Purification Technology, 2012Co-Authors: Vanessa J. Pereira, Joana Galinha, Maria T. Barreto Crespo, Cristina T. Matos, João G. CrespoAbstract:This study evaluates the integration of nanofiltration with direct and indirect UV Photolysis for drinking water treatment in order to guarantee effective removal of different hormones with endocrine disruption capabilities - mestranol, octylphenol, nonylphenol, progesterone, estrone, estriol, 17α-ethynylestradiol, and β-estradiol - from real surface water matrices. The integration of nanofiltration previously to low pressure ultraviolet direct or indirect Photolysis reduces the level of turbidity as well as the micropollutant contamination levels in drinking water supplies, due to rejection based on size exclusion and molecular interactions with the nanofiltration membrane surface. The use of nanofiltration in the treatment of surface waters spiked with different hormones allowed their rejection at levels higher than 71% for all target hormones except estriol. Low pressure indirect Photolysis with 100 mg/L of hydrogen peroxide was also efficient to degrade the selected hormones with percent degradations higher than 74% achieved for all the hormones, except nonylphenol (55%). The integrated process (nanofiltration followed by direct Photolysis or indirect Photolysis) is extremely efficient to remove all the target hormones from a real surface water matrix and guarantees the production of water with extremely high chemical quality. © 2012 Elsevier B.V. All rights reserved.
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drinking water treatment of priority pesticides using low pressure uv Photolysis and advanced oxidation processes
Water Research, 2010Co-Authors: Sandra Sanches, Maria Teresa Barreto Crespo, Vanessa J. PereiraAbstract:Abstract This study reports the efficiency of low pressure UV Photolysis for the degradation of pesticides identified as priority pollutants by the European Water Framework Directive 2000/60/EC. Direct low pressure UV Photolysis and advanced oxidation processes (using hydrogen peroxide and titanium dioxide) experiments were conducted in laboratory grade water, surface water, and groundwater. LP direct Photolysis using a high UV fluence (1500 mJ/cm 2 ) was found to be extremely efficient to accomplish the degradation of all pesticides except isoproturon, whereas Photolysis using hydrogen peroxide and titanium dioxide did not significantly enhance their removal. In all matrices tested the experimental Photolysis of the pesticides followed the same trend: isoproturon degradation was negligible, alachlor, pentachlorophenol, and atrazine showed similar degradation rate constants, whereas diuron and chlorfenvinphos were highly removed. The degradation trend observed for the selected compounds followed the decadic molar absorption coefficients order with exception of isoproturon probably due to its extremely low quantum yield. Similar direct Photolysis rate constants were obtained for each pesticide in the different matrices tested, showing that the water components did not significantly impact degradation. Extremely similar Photolysis rate constants were also obtained in surface water for individual compounds when compared to mixtures. The model fluence and time-based rate constants reported were very similar to the direct Photolysis experimental results obtained, while overestimating the advanced oxidation results. This model was used to predict how degradation of isoproturon, the most resilient compound, could be improved.
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uv degradation kinetics and modeling of pharmaceutical compounds in laboratory grade and surface water via direct and indirect Photolysis at 254 nm
Environmental Science & Technology, 2007Co-Authors: Vanessa J. Pereira, Howard S Weinberg, Karl G Linden, Philip C SingerAbstract:Direct and indirect Photolysis of pharmaceutically active compounds (PhACs) was investigated in laboratory-grade water (LGW) and a local surface water using a low-pressure ultraviolet batch reactor. The PhACs selected in this study belong to different therapeutic classes and are known to occur in environmental samples. Fundamental Photolysis and advanced oxidation process parameters obtained in LGW (such as the decadic molar absorption coefficient, quantum yield, and degradation rate constants) are reported and discussed. These parameters, together with the incident photon irradiance, solution depth, and solution absorbance were used to develop UV and UV/H2O2 Photolysis models that were compared with experimental results obtained in the surface water. The model predicted the experimental UV Photolysis removals well but underestimated the UV/H2O2 Photolysis results. These models were used to discuss the effects of optical path length and H2O2 concentration on the UV-based rate constant predictions.
Jingwen Chen - One of the best experts on this subject based on the ideXlab platform.
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Photolysis mechanism of sulfonamide moiety in five-membered sulfonamides: A DFT study.
Chemosphere, 2018Co-Authors: Pu Ge, Hang Yu, Jingwen Chen, Jingping QuAbstract:Abstract Quantum chemical calculations have been performed to investigate the Photolysis mechanism of relatively susceptible sulfonamide moiety of five-membered sulfonamide (SA) antibiotics, such as sulfamethoxazole, sulfisoxazole, sulfamethizole, and sulfathiazole. The results show that the ·OH-mediated indirect Photolysis of sulfonamide linkage has two possible multi-step reaction pathways, viz., H-abstraction and electrophilic C1-attack, which is contrast to previously reported one-step cleavage manner. The newly proposed indirect Photolysis mechanisms could be applied to six-membered SAs such as sulfadimethoxine. It has been found that the dissociation of S N bond is easier in direct Photolysis than ·OH-mediated indirect Photolysis. Wiberg bond index and LUMO-HOMO energy gap are investigated to clarify the origin of the discrepant reactivity of sulfonamide moiety of SAs at singlet and triplet states. In comparison with singlet states, the S N bond of SAs is weaker at triplet states of SAs and thus results in higher reactivity of sulfonamide moiety, as also suggested by smaller LUMO-HOMO energy gap. This study could add better understanding to the Photolysis mechanisms of SAs, which would be also helpful in utilizing quantum chemistry calculation to investigate the behavior and fate of antibiotics in the aquatic environment.
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disappearance of polycyclic aromatic hydrocarbons sorbed on surfaces of pine pinua thunbergii needles under irradiation of sunlight volatilization and Photolysis
Atmospheric Environment, 2005Co-Authors: Degao Wang, Jingwen Chen, Zhen Xu, Xianliang Qiao, Liping HuangAbstract:Abstract The solar photodegradation of 16 polycyclic aromatic hydrocarbons (PAHs), sorbed on surfaces of pine [ Pinua thunbergii ] needles was investigated. The PAHs were produced by combustion of polystyrene and exposed onto the surfaces of pine needles. The disappearance of PAHs sorbed on the pine needle surfaces is mainly caused by volatilization and Photolysis, with Photolysis playing a major role. The volatilization rates correlate with PAH molecular weight significantly. The Photolysis of the 16 PAHs follows first-order kinetics and their Photolysis half-lives ( t 1/2,P ) range from 12.9 h for naphthalene to 65.4 h for fluorene. The PAHs have similar half-lives whether they are sorbed on spruce or pine needles. Compared with water, the cuticular waxes of pine needles can stabilize Photolysis of PAHs and facilitate accumulation of PAHs. t 1/2,P for selected PAHs correlate with semi-empirically calculated energy of the highest occupied orbital ( E HOMO ). Photochemical behaviors of PAHs are dependent not only on their molecular structures but also the physical–chemical properties of the substrate on which they are adsorbed.
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correlation between Photolysis rate constants of polycyclic aromatic hydrocarbons and frontier molecular orbital energy
Chemosphere, 1996Co-Authors: Jingwen Chen, L. R. Kong, Qin Huang, L S WangAbstract:In the present study, pseudo-first-order direct Photolysis rate constants of 17 PAHs were determined. Basing on the frontier molecular energy, Ehomo and Elumo, a QSPR equation was obtained. The obtained equation can be used to predict Photolysis rate constants of PAHs under the irradation of medium pressure mercury lamp. As shown in the following equation, the obtained relationship between the logarithm of Photolysis rate constants(logkexp) and Elumo-Ehomo gap was parabolic. logkexp=−32.738+9.770 (Elumo−Ehomo)−0.715(Elumo−Ehomo)2 n=17, r=0.921, SE0.322, F=38.911, p=0.0000 Where r is the multiple correlation coefficient, SE is the standard error of estimates for the full regression, F is the F value for analysis of variance, p is the significance level. The obtained parabolic relationship is reasonable when internal and external factors controlling Photolysis rate are considered.
João G. Crespo - One of the best experts on this subject based on the ideXlab platform.
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Integration of nanofiltration, UV Photolysis, and advanced oxidation processes for the removal of hormones from surface water sources
Separation and Purification Technology, 2012Co-Authors: Vanessa J. Pereira, Joana Galinha, Maria T. Barreto Crespo, Cristina T. Matos, João G. CrespoAbstract:This study evaluates the integration of nanofiltration with direct and indirect UV Photolysis for drinking water treatment in order to guarantee effective removal of different hormones with endocrine disruption capabilities - mestranol, octylphenol, nonylphenol, progesterone, estrone, estriol, 17α-ethynylestradiol, and β-estradiol - from real surface water matrices. The integration of nanofiltration previously to low pressure ultraviolet direct or indirect Photolysis reduces the level of turbidity as well as the micropollutant contamination levels in drinking water supplies, due to rejection based on size exclusion and molecular interactions with the nanofiltration membrane surface. The use of nanofiltration in the treatment of surface waters spiked with different hormones allowed their rejection at levels higher than 71% for all target hormones except estriol. Low pressure indirect Photolysis with 100 mg/L of hydrogen peroxide was also efficient to degrade the selected hormones with percent degradations higher than 74% achieved for all the hormones, except nonylphenol (55%). The integrated process (nanofiltration followed by direct Photolysis or indirect Photolysis) is extremely efficient to remove all the target hormones from a real surface water matrix and guarantees the production of water with extremely high chemical quality. © 2012 Elsevier B.V. All rights reserved.
Wenlong Wang - One of the best experts on this subject based on the ideXlab platform.
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light source dependent role of nitrate and humic acid in tetracycline Photolysis kinetics and mechanism
Chemosphere, 2013Co-Authors: Yang Li, Wenlong WangAbstract:Abstract To elucidate the environmental fate of tetracycline (TC), we reported the light-source-dependent dual effects of humic acid (HA) and NO 3 - on TC Photolysis. TC Photolysis rate was highly pH- and concentration-dependent, and was especially enhanced at higher pH and lower initial TC concentrations. Under UV-254 and UV-365 irradiation, HA inhibited TC Photolysis through competitive photoabsorption or reactive oxygen species (ROS) quenching with TC; under solar and xenon lamp irradiation, TC Photolysis was enhanced at low HA concentration due to its photosensitization, whereas was suppressed at high HA concentration due to competitive photoabsorption or ROS quenching with TC. Similarly, the effect of NO 3 - on TC Photolysis varied with light irradiation conditions. Even under the same light irradiation conditions, the effects of HA or NO 3 - on TC Photolysis varied with their concentrations. The electron spin resonance spectrometer and ROS scavenger experiments demonstrated that TC Photolysis was involved in O 2 - -mediated self-sensitized Photolysis. The Photolysis pathways were involved in hydroxylation and loss of some groups. More toxic intermediates than TC were generated under different light irradiation conditions. These results can provide insight into the potential fate and transformation of TC in surficial waters.
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Photolysis of enrofloxacin in aqueous systems under simulated sunlight irradiation kinetics mechanism and toxicity of Photolysis products
Chemosphere, 2011Co-Authors: Yang Li, Wenlong WangAbstract:Abstract Photolysis of Enro in water was investigated under simulated sunlight irradiation using a Xenon lamp. The results showed that Enro Photolysis followed apparent first-order kinetics. Increasing Enro concentration from 5.0 to 40.0 mg L −1 led to the decrease of the Photolysis rate constant from 1.6 × 10 −2 to 3.0 × 10 −3 min −1 . Compared with the acidic and basic conditions, the Photolysis rate was faster at neutral condition. Both of nitrate and humic acid can markedly decrease the Photolysis rate of Enro because they can competitively absorb photons with Enro. The electron spin resonance and reactive oxygen species scavenging experiments indicated that Enro underwent self-sensitized photooxidation via OH and 1 O 2 . After irradiation for 90 min, only 13.1% reduction of TOC occurred in spite of fast Photolysis of 58.9% of Enro, indicating that Enro was transformed into intermediates without complete mineralization. The Photolysis of Enro involved three main pathways: decarboxylation, defluorination, and piperazinyl N 4 -dealkylation. The bioluminescence inhibition rate using Vibrio fischeri increased to 67.2% at 60 min and then decreased to 56.9% at 90 min, indicative of the generation of some more toxic intermediates than Enro and then the degradation of the intermediates. The results will help us understand fundamental mechanisms of Enro Photolysis and provide insight into the potential fate and transformation of Enro in surface waters.
Jochen Stutz - One of the best experts on this subject based on the ideXlab platform.
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oh formation by hono Photolysis during the berlioz experiment
Journal of Geophysical Research, 2003Co-Authors: B Alicke, A Geyer, A Hofzumahaus, F Holland, S Konrad, H W Patz, J Schafer, Jochen StutzAbstract:[1] The Photolysis of nitrous acid (HONO) in the early morning hours is an important source of OH radicals, the most important daytime oxidizing species. Although the importance of this mechanism has been recognized for many years, no accurate quantification of this OH source is available, and the role of HONO Photolysis is often underestimated. We present measurements of HONO and its precursor NO2 by Differential Optical Absorption Spectroscopy (DOAS) during the Berliner Ozonexperiment (BERLIOZ) field campaign in July/August 1998 at Pabstthum near Berlin, Germany. HONO concentrations, formation rates, and simultaneously measured HONO Photolysis frequencies are used to calculate the total amount of OH formed by HONO Photolysis during a full diurnal cycle. A comparison with the OH formation by Photolysis of O3 and HCHO and by the reaction of alkenes with ozone shows that HONO Photolysis contributed up to 20% of the total OH formed in a 24 hour period during this campaign. In the morning hours, HONO Photolysis was by far the most important OH source during BERLIOZ. INDEX TERMS: 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0394 Atmospheric Composition and Structure: Instruments and techniques; KEYWORDS: HONO, photochemistry, OH, Photolysis, HCHO, ozone
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impact of nitrous acid Photolysis on the total hydroxyl radical budget during the limitation of oxidant production pianura padana produzione di ozono study in milan
Journal of Geophysical Research, 2002Co-Authors: B Alicke, U Platt, Jochen StutzAbstract:[1] The Photolysis of nitrous acid (HONO) in the early morning hours is believed to be a significant source of hydroxyl radicals (OH), the most important daytime oxidizing species. Although the importance of this mechanism has been recognized for many years, no accurate experimental quantification is available. Here we present measurements of HONO, NO2, SO2, O3 and HCHO by Differential Optical Absorption Spectroscopy (DOAS) during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono (LOOP/PIPAPO) study in May–June 1998 in Milan, Italy. The concentration of NO and J(NO2)/J(HONO) were simultaneously monitored by in situ monitors. The Photolysis frequencies of HCHO and O3 were determined with a radiative transfer model. High nocturnal HONO mixing ratios of up to 4.4 ppb were regularly observed. Elevated daytime HONO levels during cloudy periods show that the formation of HONO proceeds after sunrise and therefore also represents a source of hydroxyl radicals throughout the day. Averaged over 24 hours, HCHO Photolysis is the most important source of OH in Milan, followed by either ozone or HONO Photolysis. Our observations indicate that on certain days the OH production from HONO can be even more important than that from ozone Photolysis. The diurnal variation of the different OH formation mechanisms shows that HONO Photolysis is by far the most important source in the early hours of the morning, and can be as large as and even surpass the total OH production at noon.
