july 20-23, novosibirsk, russia - nsc.ru adding radical scavengers. results showed chloramphenicol...
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Abstracts of Russian-Chinese Workshop on Environmental Photochemistry
July 20-23, Novosibirsk, Russia
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The Workshop is organized by
Voevodsky Institute of Chemical School of Resources
Kinetics and Combustion and Environmental
Sciences,
of Siberian Branch Wuhan University,
of Russian Academy of Sciences, Wuhan, Hubei, P.R.
China
Novosibirsk, Russia
Russian Foundation of Basic Research
National Natural Science Foundation of China
Organizing Committee
Prof. Nikolai M. Bazhin, Voevodsky Institute of Chemical Kinetics
and Combustion, Novosibirsk (co-chairman).
Prof. Wu Feng, Wuhan University, Wuhan (co-chairman)
Prof. Nansheng Deng, Wuhan University, Wuhan
Prof. Victor Plyusnin, Voedovsky Institute of Chemical Kinetics and
Combustion, Novosibirsk
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Dr. Evgeni Glebov, Voedodsky Institute of Chemical Kinetics and
Combustion, Novosibirsk (conference secretary)
Dr. Ivan Pozdnyakov, Voevodsky Institute of Chemical Kinetics and
Combustion, Novosibirsk
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Section I. Photodegradation of Pollutants in Homogeneous Aqueous Systems
Photochemical Reaction in Circulatory Water Treatment System of Upper-Tidal Pond
Feng Wu, Linjing Zhang
Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University,
430079, P. R. CHINA E-mail: [email protected].
In this work, the experimental facility is designed according to the principle of the circulatory water treatment system of upper-tidal pond. The photochemical reaction occurred in it has been investigated. Three water samples were irradiated by
simulating light sources, and the concentration of main ROS (include OH, 1O2 and
H2O2) produced by them was detected. In addition, the photodegradation of the two model antibiotics (chloramphenicol and tetracyline) were studied.
The concentrations of main ROS produced by the three water sample under irradiated were detected by HPLC and spectrophotometry. The results indicated that ROS was produced in all three water samples under illumination. They had similar variation tendency in three water samples. The Cumulative concentration of singlet oxygen showed an upward trend in all the three water samples. The production of hydrogen peroxide was not very significant and increased first and then stabilized. The hydroxyl radical concentration increased at the initial stage of the reaction, then decreased and stabilized. According to calculations, the concentration of ROS detected in three water samples is consistent with the literature.
The photodegradation of chloramphenicol and tetracycline in the water sample of Xing Lake and East Lake were investigated respectively, and it fit to the pseudo-first order kinetics. The photodegradation rate decreased with the decrease of illumination intensity. Result showed that •OH, rather than 1O2, was the predominant oxidant in photodegradation of chloramphenicol. And photodegradation efficiency of chloramphenicol was inhibited from 30% to 17% by addition of radical scavengers. While the photodegradation efficiency of tetracycline was inhibited from 71% to 60% by adding radical scavengers. Results showed chloramphenicol and tetracycline have different photodegradation pathways.
Acknowledgements Many thanks to the supports from Natural Science Foundation of China
(21077080), the NSFC-RFBR cooperation project (21211120159), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (20100141110046).
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The Photolysis of Phenoxyacetic Acidic Herbicides under Excilamps Irradiation in Aquatic Systems
Irina V. Sokolova1, Nikolay O. Vershinin1, Olga N. Tchaikovskaya1, Elena A. Karetnikova2
1Siberian Physical Technical Institute, Tomsk State University, pl. Novosobornaya 1, Tomsk, 634050 Russia,
2Institute of Water and Ecological Problems of the Far Eastern Branch of Russian Academy of Sciences, 65, Kim-Yu-Chen St., Khabarovsk 680000, Russia
The development and use of herbicides have played an important role in the increase of agricultural productivity. On world level, herbicide production accounts for 46% of the total pesticide production. Acidic herbicides are widely used for the control of broad-leaved weeds and other vegetation. They are relatively inexpensive and very potent even at low concentrations. The majority of herbicides is directly applied to soil or sprayed over crops fields and as consequence of large production and high stability, they are released directly on environment. The presence of the chlorine groups causes such compounds to be more resistant to biodegradation than the unsubstituted analogs. Nowadays studies of the effectiveness of UV modern sources are still very important. The irradiation of these sources is absorbed by the high-lying electronically excited states of the organic molecules and may lead to the influence of radiation wavelength on optimal canals of the molecule phototransformation [1]. This paper describes investigations into the photolysis of 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in water. The UV-radiation sources used for investigations were four barrier discharge excilamps (Xe2, KrCl, XeBr and XeCl), emitting maximum UV-radiation at 172, 222, 283 and 308 nm, respectively. Irradiation of MCPA solution with a KrCl excilamp yield 2-methylhydroquinone and lactone of 2-hydroxy-3-methyl-5-chlorophenoxyacetic acid as the main photoproducts and with a XeBr lamp – yield 2-methylhydroquinoneas the main photoproduct.
This work is supported by the Grants for the Support of RFBR № 10-08-90706_mob_st and of Leading Scientific School № 512.2012.2.
1. Sosnin E.A., Sokolova I.V., Tarasenko V.F. / In Book: Photochemistry Research Progress (Eds. by A. Sanchez, S.J. Gutierrez). Nova Science Publishers, 2008. P. 225-269.
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Degradation of Environmental Endocrine Disruptors by Photolysis of Fe(III)-Citrate Complex
Lei Wang1, Changbo Zhang2, Zhongqi Liu2, Feng Wu3, Gilles Mailhot4 1National Center for Nanoscience and Technology, Beijing 100190, P. R. China
2Agro-environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, P. R. China 3School of Resources and Environmental Science, Wuhan University, 430079, P. R. China.
4Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF)-ENSCCF, BP 10448, F-63000 Clermont-Fd, France.
E-mail: [email protected]
In the aqueous solution containing 60.0/30.0 mol L-1 Fe(III)/citrate and 7.0
mmol L-1 benzene at pH 3.0, 96.66 mol L-1 ·OH was produced after irradiation by
250W metal halide light (≥313 nm) for 160 minutes. The average generation rate
was 0.6 mol L-1 min-1. Results showed that Fe(III)-Citrate complexes can degrade
environmental endocrine disruptors (EEDs). The photodegradation efficiency of DES was 57%, E1, EE2 and E2 were about 46%, NP and BPA were nearly 27%. The photodegradation of EEDs were all pseudo-first order reaction.
0 20 40 60 80 100 120 140 160
0.4
0.5
0.6
0.7
0.8
0.9
1.0 E
1 EE
2
DES E2
BPA NP
C/C
0
Irradiation time/min
Figure 1. Photodegradation efficiency of EDDs induced by Fe(III)-citrate Complexes
Table 1. Kinetic analysis of EEDs Photodegradation (n=9, rc=0.8471, a=0.001)
EEDs -r1 Kinetic equation k (min-1)
E1 0.9888 lnC/C0= 0.00395-0.00371t 0.00371
EE2 0.9877 lnC/C0= -0.03959-0.0039 t 0.0039
DES 0.9885 lnC/C0= 0.00927-0.00489 t 0.00489
E2 0.9669 lnC/C0= -0.06032-0.00339 t 0.00339
BPA 0.9735 lnC/C0= -0.03688-0.0019 t 0.0019
NP 0.9861 lnC/C0= 0.01153-0.00206 t 0.00206
Acknowledgements This work was supported by NSFC (Grant No.21107055), China Postdoctoral Science Foundation funded project, Scientific Research Foundation for Returned Scholars, Ministry of Education of China, and the K. C. Wong Education Foundation, Hong Kong. The authors acknowledge the funding of Central Public Research Institutes Basic Funds.
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Direct and Indirect Photodegradation of Estriol in Aqueous Solutions
Yong Chen1, Yuegang Zuo2 1 School of Environmental Science and Engineering, Huazhong University of Science and Technology,
Wuhan 430074, China. 2 Chemistry & Biochemistry Department, University of Massachusetts Dartmouth, North Dartmouth,
MA 02747
E-mail: [email protected].
Estriol (E3) as one of typical representatives of steroid estrogens is detrimental to endocrine systems of animals and humans due to its potential estrogenic activity. Photodegradation of E3 in the presence of two main photoreactive species humic acid (HA) and nitrate in the natural water was investigated under simulated sunlight. The direct and indirect photodegradation of E3 was speciation-dependent. The deprotonated speciation of E3 was more favorable for the direct photolysis and hydroxyl radicals-induced indirect degradation compared to its protonated form. The direct photolysis increased with the increasing incident light intensity and the decreasing initial concentration of E3. The presence of nitrate always enhanced the decay of E3 in the aqueous solutions. For HA, the enhancement or inhibition effect was first found to be dependent on the light intensity. Under weak irradiation, the direct photodegradation of E3 is less important compared to the photosensitized degradation by HA due to the generation of hydroxyl radicals. However, humic acid played the role of light screening in the direct photodegradation of E3 under intense irradiation. By GC-MS analysis, the photoproducts of E3 were identified and the photodegradation pathway was proposed.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (21007018 and 51078161), Natural Science Foundation of Hubei Province (2010CDB01104), Chenguang Youth Found of Wuhan (201050231074), and Research Fund for the Doctoral Program of Higher Education of China (20100142120004).
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Photolysis of Herbicide 2,4,5-Trichlorophenoxyacetic Acid in Aqueous Solution
Maria Yurkova, Ivan Pozdnyakov, Victor Plyusnin, Vjacheslav Grivin
Institute of Chemical Kinetics and Combustion SB RAS, 630090, Russia, Novosibirsk Institutskaya, 3,
2,4,5 trichlorophenoxyacetic acid (2,4,5-T) is one of the widely used herbicides in agricultural field and its world production exceeds tens of thousands tons per year. 2,4,5-T is a toxic contaminant and its introducing into the water systems leads to deterioration of drinking water. Photochemical technique is one of perspective approach of water purification. The report presents obtained data of initial stages of 2,4,5-T photodegradation by stationary and nanosecond laser (266 nm) flash photolysis.
UV-excitation 2,4,5-Т leads to its photoionization with generation of hydrated electron – cation-radical pair (Figure 1), that is typical feature of photochemistry of chlorophenols. Former intermediate is characterized by absorption band with maximum at 720 nm, cation-radical demonstrates absorption band with maximum at 490 nm. In deoxygenated solutions the main decay channels of hydrated electron are
capture by 2,4,5-Т (ke 7109 М-1s-1) and recombination with cation-radical. Cation-
radical of 2,4,5-Т undergoes hydrolysis by water molecule (kh 1.4105 М-1s-1) with
generation of long-lived phenoxyl radical. The latter decays apparently in recombination reaction with formation of final photolysis products.
This work was supported by RFBR (grants 11-03-00268, 12-03-00482, 12-03-91153-GFEN).
Figure 1. (а) – Transient absorption spectra recorded 0.05 (1), 0.4 (2), 1.6 (3), 4 (4) and 48 (5) s
after flash excitation of 2,4,5-T. (b) - kinetic curves at 500 (1) and 720 (2) nm.
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Photodegradation of Sulfamethoxazole in Water
Jing Xu, Zhaohuan Mai, Feng Wu
Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University,
430079, P. R. CHINA E-mail: [email protected].
Antibiotics and their derivatives, which are considered as micro-pollutants in aqueous environment (usually in the level of μg/L to mg/L), are raising public concerns recently. Antibiotics have become a new kind of pollutants as they get into environment constantly because of their widely usage, and this made them become a threat to ecological environment and human health. Therefore, it is important to figure out how to effectively treat water containing antibiotics, and minimize their harm to human beings and the environment.
In this research, 250W high pressure mercury lamp was used as light source and sulfamethoxazole (SMX) was used as the representation of antibiotics. Photodegradation of sulfamethoxazole was studied under the condition of Fe(III)/oxalate/UV system. Box-Behnken design and response surface methodology (RSM) were used to design and analyze the experiment. The influences of experimental factors, including pH of solutions, concentrations of Fe3+, C2O4
2-/Fe3+ ratio, and initial concentrations of SMX, were examined. The photodegradation rate was calculated by its degradation percentage per minutes and the interaction between each factor was analyzed by RSM.
The results show negative correlation between initial concentrations of SMX and photodegradation rate, meanwhile, other factor like pH, concentrations of Fe3+ and C2O4
2-/Fe3+ ratio show positive correlation to photodegradation rate. According to estimated coefficient, the influence ability decreases in the order: pH > [Fe3+] > C0-SMX > [Ox2-]/[Fe3+] ratio. Of these interaction factors, pH and [Fe3+], [Fe3+] and [Ox2-]/[Fe3+] ratio show more obvious interaction effect than other interaction factors. Optimization condition is also obtained by RSM: pH=4.24, C0-SMX=5.00mg/L, [Fe3+]=59.43, Ox/Fe3+ ratio=15.26 and under the optimization condition the photodegradation rate is 0.2993%.
Acknowledgements
This work was supported by the NSFC-RFBR cooperation project (21211120159).
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Direct and Indirect Photolysis of Chloramphenicol in Water: Kinetics and Influencing Factors
Danna Zhou
College of Material Science and Chemical Engineering, China University of Geosciences, Wuhan 430074, PR China. E-mail: [email protected]
In the last decade, pharmaceuticals and personal care products (PPCPs) have
been one of the most important groups of contaminants, which have been frequently studied in environmental chemistry for their extensive distribution in environmental media and potential impacts on environmental quality and biological species as well. The photochemistry in water plays very important role in the environmental behavior of PPCPs and may also be applied in the treatment of PPCPs for the purpose of water purification.
The photodegradation (direct and indirect photolysis) of antibiotic chloromycetin (Cm) in aqueous solutions in the presence of iron and humic acid were investigated under UV-C light (254 nm) and UV-Vis light (≥ 365 nm) respectively. Effects of pH, ionic strength, the initial concentration of Cm, iron and humic acid were inspected. Results showed that at pH 5-7, Cm underwent direct photolysis with higher degradation efficiency over 90% and the quantum yield was 0.084. Higher salt content (NaCl, 0.01 - 0.5 mol l-1) was beneficial to the direct photolysis. Indirect photolysis of Cm in the presence of iron under UV-Vis light was attributed to the photochemical production of ·OH radicals at acidic pH values close to 3. Increasing pH value made the rate of indirect photolysis of Cm decreased significantly. Both direct and indirect photolysis reactions obeyed the pseudo first order kinetics law. Humic acid played an inhibitory effect on the photodegradation of Cm under the conditions in this work which implied that photosensitization of humic acid did not play its role in the photodegradation of Cm.
Acknowledgements
This work was supported by the NSFC (41103066) and NSFC-RFBR cooperation project (21211120159).
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Study of Quantum Yields of 2, 4-D Degradation Photoinduced by Fe(III)-Carboxylate complex
Changbo Zhang1, Lei Wang2, Zhongqi Liu1, Feng Wu3, Gilles Mailhot4 1Agro-environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, P. R. China
2National Center for Nanoscience and Technology, Beijing 100190, P. R. China 3School of Resources and Environmental Science, Wuhan University, 430079, P. R. China
4 Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF)-ENSCCF, BP 10448, F-63000 Clermont-Fd, France.
E-mail: [email protected]
The 2, 4-Dichlorophenoxyacetic acid (2, 4-D) degradation photoinduced by Fe(III)-Carboxylate complexes (Fe(III)-Tar, Fe(III)-Pyr and Fe(III)-Cit) were studied in the aqueous solution under monochromatic irradiation. The quantum yields of 2, 4-D disappearance and Fe(II) formation were studied and analysed in detail. Effect of
irradiation wavelength, pH and oxygen on the Φ2, 4-D and Fe(II) were all studied in this
work. Results indicate that the quantum yields of 2, 4-D disappearance were decreased with the increase of the pH value. It was concluded that acidic condition was more favourable for the degradation of 2, 4-D in the presence of Fe(III)-Carboxylate complexes. The quantum yields of 2, 4-D disappearance were optimal at
pH 3.0 in the presence of Fe(III)-Pyr complexes (2, 4-D = 0.046).
Oxygen played a very important role in the photochemical process. Different gas medium of reaction solutions were obtained by bubbling oxygen or argon 10 min into the solutions before irradiation. In the deaerated solution, the quantum yield of 2, 4-D was negligible, especially in the presence of Fe(III)-Cit and Fe(III)-Tar complexes. The quantum yield of Fe(II) formation in oxygenated solution was almost five times higher than that those obtained in the absence of oxygen. In these experiments, the quantum yields of Fe(II) formation and 2, 4-D disappearance were higher in the presence of Fe(III)-Pyr than with other complexes.
Acknowledgements
This work was supported by NSFC (Grant No. 21107055), China Postdoctoral Science Foundation funded project, Scientific Research Foundation for Returned Scholars, Ministry of Education of China, and the K. C. Wong Education Foundation, Hong Kong. The authors acknowledge the funding of Central Public Research Institutes Basic Funds.
12
Environmental Photochemistry: From Theory to Application
Nansheng Deng, Feng Wu
Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University,
430079, P. R. China E-mail: [email protected].
Environmental photochemistry is one of important front fields of environmental chemistry, which has been divided into two branches, one is the natural environmental photochemistry and the other is applied environmental photochemistry. The main scopes of the first branch include: 1) photochemical processes and mechanisms in the environment; 2) effects of human’s activities on the photochemical processes and the disrupting mechanisms; 3) results of human’s disruption on the environment, biosphere and mankind.
While in the applied environmental photochemistry, there are mainly three areas. The first is solar energy and chemical energy conversion. The second is environmental remediation mainly related with Advanced Oxidation Processes (AOPs). And the third is photo-functional materials, for examples superhydrophilicity, self-cleaning, sanitary Coating, and UV-blocking materials.
Theoretical environmental photochemistry and applied environmental photochemistry are interrelated with each another. For example, aquatic photochemical processes focus on the environmental behaviors (mainly transfer and transformation) of pollutants in aquatic system usually induced by the abundant components in the natural waters like iron, humic substance, alga and so on. While, some applied environmental photochemistry researches on the photochemical methods for pollution control by using AOPs were based on the photochemistry of iron species. The systems include traditional photo-Fenton and photo-Fenton-like systems. Theory of environmental photochemistry help us in finding new and more efficient systems for applied environmental photochemistry to destroy the emergent contaminants. In reverse, simulative research of the photooxidation or photoreduction for the purpose of pollutant removal helps to reveal the chemical mechanisms of the photochemical processes of such pollutants in the natural environments.
Acknowledgements
The author thanks the financial support from the NSFC-RFBR cooperation project (21211120159).
13
Photodegradation of Propranolol by Fe(III)-Citrate Complexes: Kinetics, Mechanism and Effect of
Environmental Media
Zizheng Liu
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China.
E-mail: [email protected]
As one of the subclass of PPCPs, -blockers have been used for the treatment
of hypertension, angina pectoris, cardiovascular system and lately chronic heart
failure. -blockers cannot be completely eliminated in sewage treatment plants and
they have been widely detected in surface waters. The existence of -blockers are
detrimental to aquatic organisms. It has been demonstrated that most -blockers had a
specific toxicity towards the green algae Desmodesmus subspicatus. Among these -
blockers, propranolol has the highest acute and chronic toxicit. In this research, 150-W Xenon Short Arc Lamp was used as light source and
photodegradation of propranolol was studied under the condition of Fe(III)/citrate
system. Photogeneration of HO was optimized in Fe(III)-citrate solution within the
pH range of 3.0 to 9.0 to investigate its photoreactivity at neutral pH without addition
of H2O2 under simulated sunlight. The generation of HO decreased with increasing
pH within the range of 6.09.0 at the Fe(III)-to-citrate ratio of 10:50 (M). However,
when the concentration of citrate increased to 150 M, the formation rate of HO
increased in the order of pH 9.0 3.0 7.0 4.0 5.0. The pH-dependent HO
production was governed by the stability of Fe(II)/Fe(II)-citrate and the amount of
O2 in the solution. Propranolol can be efficiently photodegraded in Fe(III)-citrate
system at pH 7.0 with pseudo-first-order constant 3.1 104 s1. HO was verified to
be the main reactive oxygen species (ROS) responsible for the photodegradation of propranolol. The presence of metal ions inhibited the Fe(III)-cit-induced photodegradation in the order of Mn2+ > Cu2+ > Ca2+ > Mg2+. Both humic acid (HA) and fulvic acid (FA) markedly suppressed the degradation of propranolol. Moreover, the iron in Fe(III)-citrate system was reused by a simple addition of citrate to the reaction solution. By GC-MS analysis, the photoproducts of the propranolol were identified and the degradation pathway was proposed. This work suggests that Fe(III)-citrate complexes are good alternative for the advanced treatment of organic pollutants at neutral pH in aqueous solution.
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Section II. Photocatalysis
Recent Developments and Trends in Molecular Photocatalytic Systems for Pollutants Abatement
Alexander V. Vorontsov
Boreskov Institute of Catalysis, Novosibirsk 630090, Russian Federation e-mail: [email protected]
The stricter standards for water and air quality and larger attention paid by people to their environment caused the higher intensity of research on new and more efficient methods of environment purification. Among these methods, such advanced oxidation technology (AOT) as photocatalysis has become attractive since it allows room temperature pollutants removal and destruction using solar and artificial irradiation. Semiconductor nanoparticles and diverse molecules are usually efficiently used for photocatalytic oxidation (PCO). Homogeneous molecular photocatalytic systems are acting in natural waters and can be heterogenized in order to allow easy separation from the reaction mixture. The mechanism of their action can include the stages of energy transfer, electron transfer, proton or hydrogen atom transfer, ligand expulsion, isomerization, and dissociation. The major types of molecular photocatalysts are atoms of metals (Hg, Zn, Cd), organic sensitizers (including dyes), polyoxometallates, and metal complexes. The last type includes solvated metal cations and macrocyclic complexes. Except atomic systems, all these types of molecular photocatalysts can be applicable for water and, sometimes, air purification. The issues of stability can arise for compounds containing organic ligands. However, such homogeneous photocatalysts can be disposable single use water purification systems provided their low toxicity and environmental impact. Currently, photo-Fenton type systems are considered as the most efficient for aqueous media purification [1]. The main trend in development of water and air purification molecular systems consists in heterogenization and stabilization of photocatalysts [2].
Literature 1. A. Antoniadis, V. Takavakoglou, G. Zalidis, I. Poulios, Catal. Today, 2007, v. 124, p. 260 – 265. 2. J. Herney-Ramirez, M.A. Vicente, L.M. Madeira, Appl. Catal. B: Environ., 2010, v. 98, p. 10 – 26.
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Design of the Nanocrystalline CdS/TiO2 Photocatalyst
Ekaterina A. Kozlova1, Natalya S. Kozhevnikova2, Ariadna A. Lemke2, Svetlana V. Cherepanova1, Tatyana P. Lyubina1, Eugeny Yu. Gerasimov1, Sergey V. Tsybulya1,
Yury A. Shchipunov3, Andrey A. Remplel2
1Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia 2Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
3Institute of Chemistry FEB RAS, Vladivostok, Russia E-mail: [email protected]
Purification of air from organic pollutants is currently an acute problem. Photocatalysis on semiconductors is widely used as a purification method. The photocatalytic air treatment method usually uses TiO2 as the catalyst. The major drawback of TiO2 is its rather wide band gap and, as a result, low photoactivity under sunlight. Therefore, to enhance the catalytic process efficiency, it is necessary to shift the absorption band of the TiO2 toward longer wavelengths.
The present work was aimed at designing a complex semiconductor photocatalysts. The narrow band gap CdS is applied to the wide band gap TiO2, and this leads to the extension of the light sensitivity range of the catalyst from 365 to 515 nm. Catalysts active under visible light on the basis of the composite of cadmium sulfide and titania CdS/TiO2 were obtained in an aqueous medium by a two-stage process. The first stage was the synthesis of nanocrystalline CdS particles by chemical deposition from aqueous solutions in the presence of the complexation agents, and the second stage was the deposition of CdS on a commercially available TiO2 Hombifine N and Degussa P25.
The CdS/TiO2 catalyst activity was studied for the ethanol oxidation to acetaldehyde in a batch system under visible light irradiation (λ > 400 nm). The catalytic activity of the CdS/TiO2 Degussa P25, 0.34 μmol acetaldehyde per hour, turned out to be close to the values for the CdS/TiO2 Hombifine N. The activity of CdS/TiO2 Hombifine N without adding a complexation agent was 0.10 μmol acetaldehyde per hour, which is considerably lower than the activity of all systems containing complexation agents. The highest activity was exhibited by the samples obtained from solutions of ammine and citrate cadmium complexes where the complex ion formation constants were minimal but sufficient to prevent the formation of cadmium oxygenous impurities.
Authors acknowledge SB RAS (project #35), UB RAS (12-C-3-1002) and FEB RAS (12-II-0-04-009) for financial support.
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Photochemical Decomposition Acid Orange 7 in the Presence of Peroxydisulfate and Activated Carbon
Supported Cobalt Catalyst
Hui Zhang, Liguo Wang, Hong Gao
Department of Environmental Engineering, Wuhan University, P.O. Box C319 Luoyu Road 129#, Wuhan 430079, China.
Email: [email protected]
Textile dyes which constitute a large group of organic compounds are difficult to be degraded by conventional treatment methods owing to their non-biodegradability, complex structure and the stability. Azo dyes contribute to about 50% of all textile dyes and are widely used for the industrial applications. Acid Orange 7 (AO7), a conventional azo dye, was commonly used as a model organic contaminant for the study of the dye degradation. Sulfate radical based advanced oxidation process (SR-AOP), an emerging oxidation technology, is often used for the treatment of non-biodegradable wastewater. Sulfate radical has an oxidation potential of 2.6 V, which is next only to hydroxyl radical. Sulfate radical could be generated from the activation of persulfate by thermal, ultraviolet, ultrasound and transition metals.
In this work, activated carbon supported cobalt catalyst (Co-AC) was prepared and used as the heterogeneous catalyst in the activation of peroxydisulfate for the removal of AO7 in the presence of ultraviolet irradiation. The effect of important parameters such as peroxydisulfate concentration, catalyst loading, initial pH and temperature on the decolorization of AO7 was investigated. The result showed that ultraviolet irradiation could enhance color removal by Co-AC heterogeneous activation of peroxydisulfate. The decolorization efficiency increased with peroxydisulfate concentration, catalyst loading and temperature. AO7 could be efficiently removed at the initial pH range of 3 to 9 though acid condition favored the decolorization rate. Over 96% decolorization efficiency could be achieve under the conditions as follows, 1.0 g/L peroxydisulfate concentration, 0.8 g/L catalyst loading, 5 W UV light, neutral pH condition and room temperature.
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New Photocatalysts Based on Cadmium and Zinc Sulfides for Hydrogen Evolution From Aqueous Na2S–Na2SO3
Solutions Under Visible Light
Tatyana P. Lyubina, Ekaterina A. Kozlova
Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia E-mail: [email protected]
The rapid depletion of oil resources necessitates extensive mastering of alternative energy and raw material sources for the chemical industry. Serious attention is presently given to use of hydrogen as a fuel. An advantage of hydrogen is its high heating value. Furthermore, the product of its combustion is water, an environmentally friendly substance. The photocatalytic hydrogen production is one of the most promising methods of the solar energy use and storage.
Cadmium sulfide was the first photocatalyst to be employed in hydrogen production by irradiation of its aqueous solutions with visible light using sulfide ions as electron donors. CdS is characterized by a band gap of 2.4 eV, and the positions of its valence and conduction bands are suitable for the photocatalytic decomposition of water. However, the sulfide ion is readily oxidized to sulfate by the photogenerated holes, with Cd2+ ions escaping into the solution. A possible way of enhancing the photocatalytic activity of cadmium sulfide is to develop composite materials based on CdS and broader band semiconductors, for example, ZnS. Zinc and cadmium sulfides have similar crystal structures, so they fairly readily form Cd1-xZnxS solid solutions. In the present work, we propose a two-step method for preparation of cadmium-zinc mixed sulfides with a large specific surface area and developed porous structure.
The activity of the synthesized materials was estimated in the photocatalytic hydrogen evolution from aqueous solutions of Na2S/Na2SO3 (λ > 420 nm). The highest activity was shown by Cd0.3Zn0.7S, whose band gap is Eg = 2.71 eV. We studied the influence of the catalyst concentration, pH, and the initial substrate concentration on the rate of photocatalytic H2 evolution. At optimal process parameters, the quantum efficiency of photocatalytic hydrogen evolution was up to 12.9%, which is a large value for a process occurring under irradiation with visible light on a catalyst containing no noble metal.
Authors acknowledge Russian Federation Department of Education & Science for financial support (GK P1360).
18
Effect of Adsorbent Presence on the Kinetics of Pollutant Vapor Photocatalytic Oxidation
Dmitry S. Selishchev, Denis V. Kozlov
Boreskov Institute of Catalysis, Novosibirsk, 630090, Russian Federation E-mail: [email protected]
In the present time environmentally friendly technologies based on catalysis and adsorption phenomena are being extensively investigated. Heterogeneous photocatalytic oxidation (PCO) over TiO2 is a good method to remove volatile organic compounds (VOCs) from indoor air, because it allows a lot of pollutants to be oxidized with the formation of CO2 and H2O as final products. However, there are some limitations of TiO2-mediated photocatalytic oxidation. Firstly, it is low adsorption capacity of TiO2 and insufficient PCO rate requiring a long time to mineralize organic admixtures completely. Secondly, it is a formation of intermediates, which could be more harmful than starting pollutant. Adsorption properties of photocatalysts play important role in process of purification. One of promising way to improve photocatalyst adsorption ability, increasing adsorption rate and capacity, is addition of adsorbent in the photocatalytic system (i.e., separate usage of photocatalytic and adsorption filters) or making TiO2/adsorbent composite system, in which TiO2 is deposited on adsorbent surface.
In the first part of work influence of adsorbent on the kinetics of PCO processes was simulated using the simple single and double stage reaction
mechanisms with the adsorption stages corresponding to Langmuir model. In the static reactor in all cases the usage of adsorbent leads to the prolongation of substrate removal and product accumulation kinetic curves, but the substrate concentration becomes lower during almost all photocatalytic process. Fitting of experimental data points demonstrated a good correlation with
proposed reaction scheme. Kinetics simulation of photocatalytic reaction with intermediate demonstrates, that adsorbent could accumulate additional intermediate quantity thus keeping catalyst surface more active and contributing to faster substrate removal.
In the second part of present work activated carbon (AC) was used as an adsorbing support with TiO2 particles deposited by thermal hydrolysis of TiOSO4 in water suspension. Composite TiO2/AC catalysts were studied using some physicochemical techniques: BET, SEM, XRD, UV-Vis diffusion.
19
Gaseous acetone and cyclohexane vapor photocatalytic oxidation was investigated in the static and continuous flow photoreactors with the synthesized TiO2/AC composite photocatalysts. Complete photocatalytic mineralization of both model pollutants without formation of gaseous intermediates was observed. The same amounts of individual TiO2 and AC powders as in the case of composite sample were placed separately in the static reactor. Faster decrease of cyclohexane concentration in the beginning was followed by slower rate of photoreaction in the end of kinetics if to compare individual TiO2 and AC powders with composite sample. The most likely reason of this difference is the absence of reagents and intermediates surface transfer between individual TiO2 and AC powders. L.-H. kinetic model was used to describe experimental data in flow reactor. Obtained results demonstrated that effective adsorption constants for TiO2/AC photocatalysts were about 2 times higher than for pure TiO2.
20
Section III. Heterogeneous Processes in Model and Natural Aquatic Systems
Landfill Leachate Treatment by a Coagulation–Photooxidation Process
Zongping Wang
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
E-mail: [email protected]
Landfill leachate is generated as a result of precipitation, surface run-off, and infiltration or intrusion of groundwater percolating through a landfill. The discharge of landfill leachate can lead to serious environmental problems, since the leachate contains a large amount of organic matter (both biodegradable and non-biodegradable carbon), ammonia-nitrogen, heavy metals, chlorinated organic and inorganic salts. Although some of these pollutants can be degraded by microorganisms, the limitation of common biological processes (degradation is only a part of COD and limited removal of bio-refractory organic pollutants) has made it difficult to meet the correlative discharge standard (GB8978 (1996), China, COD < 100 mg−1). The treatment of landfill leachate by a photooxidation processes has become popular during the last 5 year, owing to the short reaction time and acceptable costs.
In this research, 15 W low-pressure UV lamp was used as light source and the effect of treatment of landfill leachate by a coagulation–photooxidation process was investigated. The effects of different dosages of coagulant and different pH values on the coagulation processes were compared. The effect of different concentrations of sodium oxalate (Na2C2O4) on the treatment process was also studied after the coagulation was performed using FeCl3·6H2O. The experimental results show that in the pH range of 3–8, the lower the pH value, the higher the efficiency of the treatment. A 24% removal of COD (chemical oxygen demand, mg(O2) L−1) can be attained by the addition of 1000 mg L−1 FeCl3. A 31% removal of COD can be attained after 4 h of irradiation alone, and a 64% removal of COD can be attained after 4 h irradiation at pH 3 with the addition of 500 mg L−1 FeCl3·6H2O.
21
Fenton’s Heterogeneous Catalytic Systems Based on Fe-Containing Zeolites and Clays
M.N. Timofeeva1, M.A. Mel’gunov1, V.N. Panchenko1, S.H. Jhung2
1 Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia 2 Department of Chemistry, Kyungpook National University, 702-701, Daegu, Korea
E-mail: [email protected]
Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species (Fe2+/Fe3+/H2O2) is of interest to environmental catalysis, because the increasing water utilization in industrial processes and agricultural activities leads to the expansion of wastewater. Nowadays for direct elimination the pollutions considerable attention has been given to the development of new Fe-containing materials as heterogeneous replacement of homogeneous systems.
Table 1. Oxidation of phenol with H2O2 over Fe-containing systems
Sample pH a (h)
Fe leaching (wt. %) c
VSB-5 8.2 > 30 -
3.1%Fe-VSB-5 8.2 9 < 0.1
6.5%Fe-VSB-5 8.2 7 (7, 7.5)c < 0.1 (n.d., <0.1)
1.8%Fe-MMM-2(2.4) b 6.2 10 0.2
1.8%Fe,Al-MMM-2(4.4) b 6.2 2.5 < 0.1
1.8%Fe,Al-MM(4.4) b 6.2 1.5 < 0.1
a pH of reaction mixture in the presence of catalyst; b pH of synthesis of Fe-containing materials;c Catalyst was used in second and third cycles.
We review herein major aspects of our research in this field synthesis and catalytic properties of iron-containing high-surface-area pillared clays (Fe-PILC and Fex,Aly-PILCs), iron-containing mesoporous molecular sieves (Fe-MMM and Fex,Aly-MMMs) and iron-containing microporous nickel phosphate molecular sieves (Fe-VSB-5) in phenol and dye oxidation with H2O2. It was demonstrated that for the high catalytic activity of Fex,Aly-PILCs and Fex,Aly-MMMs and stability to leaching of metal from solids were (1) pH of the synthesis mixture; (2) agglomeration and isolation of iron ions; (3) iron and aluminum content in the samples. The maximal activity of Fex,Aly-PILCs and Fex,Aly-MMMs was at pH 3-4 of reaction mixture, which is typically for homogeneous Fenton’s systems, and is accompanied with substantial iron leaching. It was found that pH of the reaction mixtures in the presence
22
of Fe-VSB-5 and Fe-containing materials were different due to the different surface acid-base properties (Table 1). In the presence of Fe-VSB-5 and Fex,Aly-containing materials The pH of the reaction mixtures was 8.2 and 5.6, respectively. For this reason PhOH oxidation with H2O2 over Fe-VSB-5 needs slightly hard conditions. Activity of Fex,Aly-MMMs was higher than that of Fex,Aly-PILCs at 40-50 0C due to the decrease of diffusion limitation.
23
Photooxidation of Arsenite on Kaolinite Clay Surface
Yajie Wang, Wei Ding, Jing Xu, Feng Wu
Departement of Environmental Science, School of Resources and Environmental Sciences, Wuhan University, Wuhan, 430079, China.
Email: [email protected]
The toxicity, mobility and bioavailability of arsenic in natural environment strongly depend on its speciation. Inorganic arsenic is considered to be more toxic and higher concentration than organic arsenic in natural environment. The two common inorganic forms of arsenic in soils are arsenite (As(III)) and arsenate (As(V)), which differ in their environmental behavior and fate. The transformation between the two species may be chemically and/or microbiologically mediated redox reaction. The photooxidation of As(III) to As(V) in sunlight-exposed soil could be a potential process of the transformation of arsenic species.
In our study, photooxidation of arsenite on kaolinite clay was investigated under the irradiation of simulated sunlight in a model system to preliminarily explore the kinetics and mechanism of photooxidation of arsenite on soil surface. The results suggested that photooxidation may be an important process for arsenite sorbed to sunlit soil surface, as well as to suspended clays in surface waters. The photooxidation efficiency was 11.6% when the initial concentration of As(III) was 100ug/g at pH 7.0. We observed that both addition of iron ion and decrease of pH to increase the photoreactive iron speices from clay could strongly accelerate arsenite photooxidation. The photooxidation efficiency reached 89.4% in the addition of 1mg/g ferric ion to kaolinite clay, and it reached 67.7% in the decrease of pH value to 1.0. Experiments with radical scavengers like isopropanol showed that iron could have a significant effect on arsenite photooxidation on clay surface through the production of reactive oxygen species (ROS), most likely hydroxyl (HO●) and superoxide (O2
●−) radicals. However, we found that dissolved organic matters slightly promoted arsenite photooxidation in our experiments.
Acknowledgements Many thanks to the supports from Natural Science Foundation of China
(21077080), the NSFC-RFBR cooperation project (21211120159), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (20100141110046).
24
The Study of Complexation Features of Humic Acids Macromolecules with Metal Ions by the Spectral
Dependence of the Fluorescence Quenching Efficiency
Nikolai L. Lavrik, Nurullo U. Mulloev
Institute of Chemical Kinetics and Combustion, 630090 Institutskaya3, Novosibirsk, Russia. [email protected]
Humic acids (HA) are an essential component of the environment. They are found in soil, water (dissolved) and air (aerosols). HA origin are organic material, which is synthesized by oxidation of complex natural organic molecules such as carbonilhydrates, proteins, lignins and contained in the remains of plants and non-living organisms. The structure of HA macromolecules contains many different chemical functional groups (catechols, quinones, phtalates, phenolamines, salicylates, ets.) capable of forming complex with metals. Due to this property, HA’s affect the concentration of dissolved pollutants. In this work, the complexation constants KMe method based on the observation of HA fluorescence quenching by metal ions was used. KMe value is determined by the Stern-Volmer (SV) equation.
I0 / I = 1 + KSV[Q] (1)
where [Q] is metal ions concentration; I0 and I are the fluorescence intensity (integral or at a certain wavelength) values with [Q] = 0 and [Q] ≠0, respectively; KSV is the SV constant determining the quenching efficiency. In all available studies information about the efficiency of complexation of individual sites of HA is lacked. This question can be solved by the analysis of the spectral dependence of the quenching efficiency. In the present work the fluorescence quenching of HA IHSS by Cu2+ and Cd2+ cations was studied. Fluorescence spectrum of HA were shown to contain two bands with maxima at 455 (blue component) and 505 nm (red component), for which KSV constants were determined. It was found that the efficiency of quenching by Cd2+ ion for blue and red components differ by 20%, while for Cu2+ ion this difference is higher than 3.5 times. This means that the complexing ability of HA sites with metal ions varies considerable, but the charge of the ion does not play a significant role. One possible reason for the observed differences may be the ion size: the radii of Cu2+ and
Cd2+ cations are 0.8 and 1.03 Å respectively. The ion size can determine the
availability of an ion to firm a complex at a definite site of HA. The difference in the efficiencies of fluorescence quenching for blue and red components may indicate that the ions with large radii (Cd2+) can obey steric hindrances in reaching of the complexing sites, while for the smaller cation (Cu2+) the complex formation is always possible.
25
Photocatalytic Properties of Iron-Containing Clays: Primary Processes
Evgeni M. Glebov1, Ivan P. Pozdnyakov1, Vjacheslav P. Grivin1, Victor F. Plyusnin1, Xu Zhang2, Feng Wu2, Maria N. Timofeeva3
1Institute of Chemical Kinetics and Combustion SB RAS, Novosibirsk, 630090, Russia 2Department Department of Environmental Science, Hubei Key Lab of Biomass
Resource, Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, 430079, P. R. China
3Boreskov Institute of Catalysis SB RAS, Novosibirsk, 630090, Russia E-mail:[email protected]
Clay minerals are used as heterogeneous catalysts for the remediation of wastewater [1]. Clay-induced photochemistry plays an important role in self-purification of natural aqueous systems. Both Fenton-like and direct photooxidation of organic impurities assisted by iron-rich clays are possible. The goal of this work was to compare the primary photochemical processes for the synthetic iron-rich clay montmorillonite KSF and materials prepared from natural iron-rich clays. Pillared layered aluminosilicates (LAS) were obtained from natural iron-containing montmorillonite clays [2]. Khumuulut (Mongolia) montmorillonites and Mukhortala (Buryatia) montmorillonites were used for preparation of LAS [3].
Mechanisms of clay-assisted photooxidation of organic impurities were studied by means of nanosecond laser flash photolysis. Two different situations were observed. For montmorillonine KSF homogeneous photochemical reactions of Fe(III)
leached from the clay material result in the formation of OH radical, which oxidizes
the organic molecules. On the contrary, for LAS materials the heterogeneous catalysis of phenol photooxidation was observed. For the three of four studied materials an increase in the quantum yield of phenol photodissociation was observed, indicating the catalytic effect of LAS’s in the reaction. Therefore, the photocatalytic effect of KSF was explained by the direct photolysis of Fe(OH)aq
2+ complex in the solution
bulk with the OH radical formation. For LAS’s the heterogeneous processes are
responsible for photocatalysis.
The financial support of the Russian Foundation of Basic Research (grants №№ 12-03-00482-а, 12-03-91153-ГФЕН_а) is gratefully acknowledged.
References
1. J. Feng, X. Hu, P.L. Yue, Environ. Sci. Technol., 38 (2004) 5773. 2. M.N. Timofeeva, S.Ts. Khankhasaeva, Kinet. Catal., 50 (2009) 63. 3. M.N. Timofeeva, S. Ts. Khankhasaeva, Yu.A. Chesalov, S.V. Tsybulya, V.N. Panchenko, E.
Ts. Dashinamzhilova, Appl. Catal., B, 88 (2009) 127.
26
Enhancement of Heterogeneous Cr (VI) Reduction Using Clay Minerals in the Presence of Organic Carboxylic Acids
Under UV-Vis Irradiation
Yanxiang Liu1, Feng Wu2, Nansheng Deng2 1School of Chemical and Environmental engineering, Jianghan University, Wuhan, 430056, P. R.
China 2School of Resources and Environmental Science, Wuhan University, Wuhan, 430072, P.R. China
Email: [email protected]
Clay minerals are widespread layer type aluminosilicates in the environment, which is important constituents of soils, sediments and aquifer materials, and have potential applications in pollution control and environmental protection. Especially iron-containing clay minerals are both potential reducing and binding agents for chromium. In this study, a series of experiments were conducted to investigate the effect of the properties of clay minerals and organic carboxylic acids on the reduction of Cr (VI) in aqueous solution under UV-vis illumination. Two common clay minerals (montmorillonite, kaolinite) and two typical organic carboxylic acids - oxalate and citrate) were utilized in our system. The experimental results confirmed that the existence of oxalate or citrate can markedly accelerated the Cr (VI) photoreduction reaction on the clay minerals in aqueous solution compared to clay minerals alone. This process of photo-reduction follows approximately zero order kinetics. The effects of pH, dissolved oxygen and initial Cr (VI) concentration, and clay mineral dose on removal ratio were also investigated. The photo-reduction ratio of chromium was favorable under acidic pH than in the weakly alkaline pH. Furthermore, it was found that the dissolved oxygen exerted an inhibition effect on the Cr (VI) removal comparing to the deoxygenated system.
Acknowledgement
This work was financed by the Natural Science Foundation of Hubei, China (No. 2009CDB159).
27
Section IV. Basic Photochemical Processes
Dimercaptoquinolate Ni(II), Disulfide and Photochromic Processes
Victor F. Plyusnin,1,2 Alexander V. Kolomeets 1, Vjacheslav P. Grivin,1,2 Stanislav V. Larionov 3, Helge Lemmetyinen4
1Institute of Chemical Kinetics and Combustion SB RAS, 630090 Novosibirsk, Russia 2Novosibirsk State University, 630090 Novosibirsk, Russia
3 Institute of Inorganic Chemistry SB RAS, 630090, Novosibirsk, Russia
4Institute of Materials Chemistry, Tampere University of Technology, Tampere, Finland [email protected]
Photochromic systems attract considerable attention due to their potential use in various engineering applications. Thus, discovery and investigation of new photochromic systems is not only of theoretical but also significant practical interest. Recently, we proposed novel photochromic systems that operate on the principle of reversible coordination of sulfurcontaining radicals (S-radicals) to flat dithiolate complexes of divalent nickel [1-5]. The ability of planar Ni(II) complexes to reversibly coordinated extra ligands of the pyridine type forms the basis for the designing of such systems. In order to convert Ni(II) complexes into photochromic systems, it is necessary that extra ligands be produced by the action of light. Disulfides are good objects for this purpose, since they dissociate to S-radicals under UV irradiation. It was shown [1-5] that S-radicals coordinate to flat Ni(II) dithiolate complexes with a high rate constant. The coordination is reversible, resulting in recombination of S-radicals to the parent disulfide and, thus, imparting photochromic properties to such systems. The lifetime of radical complexes depends on the nature of both the radical and the Ni(II) complex and varies from microseconds to milliseconds. Repeated coordination can increase the effective lifetime of the radical complexes to periods on the order of seconds.
In this study [6], we examined the spectroscopy and kinetics of transient species in a novel photochromic system containing perfluoro-2.2'-
dinaphthyl disulfide (SNF)2
and the flat nickel(II) dimercaptoquinolate complex (Ni(SR)2) (Fig.1).
The optical absorption spectrum of Ni(SR)2 in benzene exhibits charge transfer
400 500 600 7000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 2000 4000 6000 8000 10000
-20
-15
-10
-5
0
5
7
1
6
b
Abs
orba
nce
Wavelength / nm
h
1
6 kT
a
Ab
sorb
an
ce1
02
Time / s
460 nm
555 nm
Fig. 1. (a) Change in optical absorption spectrum of a benzene solution of (SNF)2 and the complex Ni(SR)2 during steady state photolysis and the reverse dark reaction. (b) Kinetics of change in absorption at 460 and 555 nm during the reverse dark reaction.
28
bands with maximums at 555. 396, 336, and 308 nm and absorption coefficients of 5900, 7240, 12270,
and 11970 M–1
cm–1
, respectively. Perfluoro-2.2'-dinaphthyl disulfide is characterized by an absorption band peaked at 350
nm (ε = 10500 M–1
cm–1
). The photolysis of a Ni(SR)2 and (SNF)2
solution in benzene leads to disappearance of the absorption band of the complex at 555 nm and to the formation of a new spectrum (Fig. 1a). The isosbestic points at 406, 500, and 602 nm are retained during the course of photolysis. After cessation of irradiation, the optical spectrum returns to the initial state with the same isosbestic
points. Thus, the solution of the complex Ni(SR)2 and the disulfide (SNF)2 is a
photochromic system.
During the flash photolysis of (SNF)2 in the presence of Ni(SR)2, absorption due
to the S-radical appears after a laser pulse and within a few microsecond it transforms with isosbestic points at 361, 407, 500, and 682 nm into a new spectrum (Fig. 2a)
belonging to the radical complex (•SNF)Ni(SR)2. The kinetics of reaction is shown in
the inset (Fig. 2b). The absorption due to the
radical complex (•SNF)Ni(SR)2
begins to disappear on the millisecond time scale (Fig. 3). Remaining at the time of 100–200 ms is the absorption whose spectrum corresponds to the difference of the spectra recorded in the case of steady state photolysis. In Fig. 3a, this difference (difference of the spectra before and after irradiation, Fig.1a) is depicted by the solid line (spectrum 2). The kinetics of change in absorbance (430 nm, Fig. 3b) follows the second order rate law, which can be explained by the dimerization reaction of the radical complex:
400 500 600 700 800-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0 5 10 15 200.0
0.1
0.2
0.3
A
bsor
ban
ce
Wavelength / nm
1 0 mcs2 0.8 mcs3 1.6 mcs4 3.2 mcs5 6.3 mcs6 43.7 mcs7 Ni(SR)28 (SNF)2
1
6a
7
8
A
bsor
banc
e
Time / s
430 nm
390 nmb
Fig. 2. (a) Transient spectra arising during laser flash photolysis (308 nm) of a benzene solution of (SNF)2 and Ni(SR)2: (1–6) spectra at 0, 0.1, 0.3, 0.7, 1.3, and 5
s, respectively. (b) Kinetics of change in absorption at 430 and 560 nm.
0 50 100 1500
2
4
6
8
10
12
400 450 500 550 600 650-4
-2
0
2
4
6
8
10
12
14
Abs
orb
ance
10
2
Time / ms2
Abs
orb
ance
102
Wavelength / nm
1
a b
Fig. 3. (a) Change in the spectrum of the complex
(•SNF)Ni(SR)2 during flash photolysis of a solution of (SNF)2 and Ni(SR)2
(1) the initial
spectrum of the radical complex and (2) the spectrum of the dimer [(SNF)Ni(SR)2]2 after 100
ms. (b) Decay kinetics of (•SNF)Ni(SR)2 absorption at 430 nm.
29
Thus, the nature of photochromic processes has been determined for the system composed of perfluorodinaphthyl disulfide and the planar di(mercapto-quinolinato)nickel(II) complex. It has been shown that after the photodissociation of the disulfide, the S-radicals
coordinate to the Ni(SR)2
complex at a high rate to yield radical complexes
(•SNF)Ni(SR)2, which disappear
on the millisecond timescale in the dimerization reaction (Fig.4). The dimer
[(SNF)Ni(SR)2]2 in which two
nickel ions are tied up by the disulfide molecule, degrades into the free disulfide and the two parent complexes over a few tens of minutes, completing
the photochromic transformation cycle.
The work was carried out with financial support of RFFI (grants 11-03-00268, 09-03-00330) and Program of Integrated Projects of SB RAS (grant 70).
References
1. Yu.V. Ivanov, V.F. Plyusnin, V.P.Grivin, S.V. Larionov, J. Photochem. Photobiol. A: Chem., 1998, V. 119, P. 33. 2. Yu.V. Ivanov, V.F. Plyusnin, V.P.Grivin, S.V. Larionov, Chem. Phys. Lett., 1999, V. 310, P. 252. 3. D.Yu. Vorobyev, V.F. Plyusnin, Yu.V. Ivanov, V.P. Grivin, S.V. Larionov, H. Lemmetyinen, J. Photochem. Photobiol. A: Chem., 2002, V. 149, P. 101. 4. D.Yu. Vorobyev, V.F. Plyusnin, Yu.V. Ivanov, V.P. Grivin, S.V. Larionov, H. Lemmetyinen, Chem. Phys., 2003, V289, p. 359. 5. D.Yu. Vorobyev, V.F. Plyusnin, Yu.V. Ivanov, V.P. Grivin, S.V. Larionov, H. Lemmetyinen, Izv. Akad. Nauk, Ser. Khim., 2005, № 10, P. 2291. 6. A.V. Kolomeets, V.F. Plyusnin, V.P. Grivin, High Energy Chem., 2012, V. 46, P. 240.
Ni+2N
SN
S
SFF
FFF
F F
Ni+2N
SN
S
S F F
F F F
FF
Ni+2N
SN
S
SFF
FFF
F F
Ni+2N
SN
S
S F F
F F F
FF3 13.2 10 c
Ni+2N
SN
S
SFF
FFF
F F
Ni+2 N
SN
S
S F F
F F F
FF
Ni+2N
SN
S
SFF
FFF
F F
Ni+2 N
SN
S
S F F
F F F
FF
7 -1 -13.3 10 Mc
Ni+2 N
SN
S
Ni+2 N
SN
S
S F F
F F F
FF
S F F
F F F
FF9 -1 -15 10 Mc
3
2
1
Fig. 4. Scheme of photochemical transformations of the disulfide (SNF)2 and the Ni(SR)2 complex in benzene: (1)
the coordination reaction of the •SNF radical with the Ni(SR)2 complex; (2) the reaction of two radical complexes yielding the dimer [(SNF)Ni(SR)2]2; and (3) the final reaction of photochromic transformations, the dissociation of the dimer to give the disulfide and two parent complexes
30
Towards to Enhancement of UV Protecting Efficiency of Human Eye UV Filters
Peter S. Sherin,1 Jakob Grilj,2 Yuri P. Tsentalovich,1 Eric Vauthey3 1International Tomography Center SB RAS, Novosibirsk, Russia
2 Stanford PULSE Institute, SLAC Linear Accelerator Center, Menlo Park, CA, USA 3University of Geneva, Geneva, Switzerland
E-mail: [email protected]
The UV protection of human eye is based on the absorption in 300-400 nm region by natural derivatives of the amino acid tryptophan - kynurenine (KN) and its derivatives. In protic solvents, these molecules exhibit ultrafast S1->S0 radiationless transition, with a mechanism that consists of two key steps: (i) a large charge transfer in the molecule after optical excitation and (ii) a dissipation of the electronic excitation energy into the surrounding medium via intermolecular hydrogen bonds and/or via tautomeric transformations.[1,2] Here we show that an unsaturated bond can augment the efficiency of the UV protection as it introduces an excited-state intramolecular proton transfer, which enables a very effective deactivation of the S1 excited states even in aprotic solvents.
The main object of this study is a deaminated kynurenine (carboxyketoalkene, CKA) – a product of the thermal decomposition of KN. The optical spectroscopy with femtosecond time resolution reveals that the CKA excited state decays with a characteristic time constant of about 0.7 ps in aqueous solution, 4 ps in ethanol and 9 ps in DMSO. i.e. at least 40 times faster than that for KN [1]. The origin of this tremendous acceleration is the presence of unsaturated bond, which acts as a donor of additional electron density for the carbonyl oxygen in the excited state. This also results in formation of a strong intramolecular hydrogen bond between amino and carbonyl groups leading to very effective deactivation of S1 state via a fast reversible proton transfer between these groups. From the photochemical point of view, the obtained results indicate CKA as an ideal UV filtrating molecule.
Authors appreciate RFBR projects #11-04-00143, 11-0300296, FASI state contract 14.740.11.0758 and grant № 11.G34.31.0045, grant NSh-2429.2012.3, RAS № 21.13.
[1] P.S. Sherin et al., J. Phys. Chem. B 2009, 113, 4953-4962.
[2] V.V. Yanshole et al., Phys. Chem. Chem. Phys. 2010, 12, 9502-9515.
COOH
NH2O
NH2
COOH
O
NH2 CKAKN
31
Novel Class of Double Action UV Filters for Sun-Protecting Formulations
V. V. Yanshole1,2, Yu. P. Tsentalovich1,2, Yu. F. Polienko3, S.V. Morozov3, I. A. Grigoryev3
1International Tomography Center, Institutskaya str., 3a, 630090, Novosibirsk, Russia 2Novosibirsk State University, Pirogova str., 2, 630090, Novosibirsk, Russia
3Novosibirsk Institute of Organic Chemistry, Acad. Lavrentieva ave., 9, 630090, Novosibirsk, Russia
E-mail: [email protected]
In order to protect skin from excessive sun irradiation, modern cosmetology offers wide variety of sunscreens. The major disadvantage of sunscreens is the formation of free radicals from the active components under UV irradiation. Recent investigations have revealed that presence of free radical scavengers – stable nitroxide radicals – in sunscreen formulations may substantially reduce effect of free radical damage to skin.
A modern trend in medical chemistry is the design of double action molecules such as UV absorbers covalently bound to nitroxides, which provides both UV protection and antioxidant properties combined in the same molecule. In the present work, we report the synthesis of conjugates of the natural UV filter kynurenine (KN) with the number of nitroxides (KN-RNO• conjugates) and the study of their photochemical properties in aqueous and methanol solutions. Due to the spin-exchange interaction between KN and nitroxide moieties, the triplet lifetimes in conjugates are much shorter than in KN molecule, but the triplet quantum yields are significantly higher. The reaction of intramolecular electron transfer between photoexcited KN and nitroxide moieties is the main factor determining the quantum yield of KN-RNO• conjugates photodecomposition. Consequently, KN-RNO• conjugates in aqueous solution are photochemically less stable than the parent KN molecule. Nevertheless, the photostability of KN-RNO• conjugates is much higher than that of cinnamates which are widely used as UV absorbers in modern sunscreen formulations. Thus, the combination of the endogenous chromophore KN with nitroxides is very promising for medical applications.
Acknowledgements. This work was supported by the: RFBR projects 11-04-00143, 11-0300296, FASI state contract 14.740.11.0758 and grant № 11.G34.31.0045, grant NSh-2429.2012.3, RAS № 21.13.
32
Properties and Reactivity of Phenoxyl rRadicals
Ivan P. Pozdnyakov1, Victor F. Plyusnin1, F. Wu2 1Institute of Chemical Kinetics and Combustion, Novosibirsk, Institutskaya 3, 630090,
Russia 2Department of Environmental Science, Wuhan University, Hubei, P. R. China, 430072
E-mail: [email protected]
Phenols are important feedstock for chemical and pharmaceutical industry and are widely used for production of polymers, glues, dyes, paint-and-lacquer materials, surfactants, drugs and antioxidants. So phenols themselves as well as their oxidation products and intermediates exhibit great influence on a human health and environment [1, 2]. Phenoxyl radicals (PRs) are primary species in oxidation of phenols and play important role in ecological, biochemical and (photo)catalytic processes [2, 3].
In this report the next themes will be briefly discussed: 1. Main experimental techniques of PRs generation and investigation of their
spectral and kinetic properties (including pulse radiolysis, flash photolysis and chemical oxidation)
2. General physical and chemical properties of PRs (spectroscopy, red-ox potential, reactivity, nature and toxicity of recombination products)
3. Possible implication of PRs in medicine (on example of investigation of chemical properties of reactive intermediates of common drug – paracetamol (acetaminophen)) [4].
4. PRs as intermediate species in photodegradation of chemical wastes and pesticides (on example of investigation of photodegradation of Bisphenol E and Diphenolic Acid in aqueous solution) [5].
5. Influence of environmental factors (pH, concentration of O2 and Fe(III) ions) on reactivity of phenols and PRs (on example of investigation of photochemistry of salicylic acid derivatives in a wide pH range and in presence of Fe(III) ions) [6].
This work has the support of RFBR (grants 11-03-00268, 12-03-00482, 12-03-91153-GFEN).
[1] M.-Y. Chen, M. Ike, M. Fujita, Environ. Toxicol., 17, 80 (2002). [2] C.D. Claassen, Toxicology. The basic Science of poisons. New York-Chicago-Toronto-London. Sixth Edition. 2001, 1236 р. [3] Y. Gong, X. Zhang, L. Bai, N. Deng, React Kinet. Catal. Lett., 98, 249 (2009). [4] A.V. Litke, I.P. Pozdnyakov, V.F. Plyusnin, V.P. Grivin, N.M. Bazhin, X. Zhang, F. Wu, N. Deng, High Energy Chemistry, 43, 44, (2009) [5] I. P. Pozdnyakov, L. Guo, E. M. Glebov, F. Wu, V. P. Grivin, V. F. Plyusnin, N. Deng, High Energy Chemistry, 45, 214, (2011). [6]. I.P. Pozdnyakov, V.F. Plyusnin, V.P. Grivin, D.Yu. Vorobyev, N.M. Bazhin, S. Pagés and E. Vauthey, J. Photochem. Photobiol., A: Chem., 182, 75 (2006).
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Section V. Atmosphere and Aerosols
Photochemistry and Chemistry of the Atmosphere
Nikolai M. Bazhin
Institute of Chemical Kinetics and Combustion, Novosibirsk State University, Novosibirsk 630090, Russia
A huge number of the substances penetrate to the atmosphere from the earth surface in the molecular and aerosol form. All substances undergo to the chemical transformations due to reactions with the active chemical intermediates. These active intermediates arise due to photochemical reactions induced by solar radiation. The photochemical reactions are different at the low (troposphere) and the upper part of the atmosphere (stratosphere). We begin with consideration of the reaction at the stratosphere. The photochemical processes at the stratosphere begin with the oxygen reaction ozone layer formation described by Chapman cycle. The stratospheric pollutions produce the destroy of the ozone layer and formation of the ozone hole. Ozone hole arises due to low temperatures at the stratosphere, vortex and CFC. The photochemical processes at the troposphere begin with the ozone reaction under UV light followed by the active oxygen atom formation O(1D). The ozone penetrates to the troposphere from stratosphere and arises in the process of methane oxidation. The reaction O(1D) with water molecule accompanies by two OH radicals formation. The OH concentration at the noon is equal near 106 1/cm3 and the lifetime is near 1 s. In spite of such low concentration the OH radical is main oxidizing intermediate which provides the cleaning of the low atmosphere due to high reactivity. OH radical reacts with SO2, NO2, CO, CH4, H2CO and other compounds. The lifetime of the atmospheric pollution is controlled by OH reactions. The lifetime of CH4 is near 10 years due to low reaction rate constant between OH and methane; the lifetime of SO2 is near one week. Some of the OH reactions result in the formation of the HO2 radicals. Theoretical consideration of the kinetics of the chemical reactions at troposphere is in a good agreement with the experiment.
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Oxygen Collisional Complexes X-O2 as a New Source of
Singlet Oxygen O2(1g) Photogeneration
Aleksandra P. Trushina1,2, Veniamin G. Goldort3, Sergei A. Kochubei3, Alexey V. Baklanov1,2
1 Institute of Chemical Kinetics and Combustion, Institutskaya Str. 3, 630090, Novosibirsk, Russia
2 Novosibirsk State University, Pirogova Str. 2, 630090, Novosibirsk, Russia 3 Institute of Semiconductor Physics, Lavrentiev Ave. 13, 630090, Novosibirsk, Russia
E-mail: [email protected]
The molecular environment in gas or condensed phase dramatically changes the oxygen photochemical properties providing the collision-induced enhancement of UV-radiation absorption by oxygen. This enhancement is governed by encounter complexes X-O2. Recent investigations revealed that UV-photoexcitation of oxygen encounter complexes O2-O2 is followed by process of reactive singlet oxygen species
O2(1g) formation [1]. This source and mechanism of O2(
1g) generation was
unknown before. In present work the main attention is paid to the qualitative and quantitative description of the mechanism of this new photochemical process proceeding via UV-photoexcitation of O2-O2, nitrogen-oxygen N2-O2 and isoprene-oxygen C5H8-O2 encounter complexes in the gas phase. In the experiments the pure oxygen or oxygen mixture where oxygen pressure was elevated up to 150 bar have been excited by laser radiation within 238-285 nm spectral region. Singlet oxygen
O2(1g) observed and detected by its IR-luminescence centered at 1.27 m was found
to be generated via two processes due to absorption by individual O2 molecules and
encounter complexes X-O2 respectively. The quantum yield of O2(1g) molecules
photogenerated by the encounter complexes O2-O2 has been measured in the overall investigated spectral region 238-285 nm and was found to possess rather high maximum value close to 2 at 262.6 nm. The analysis of the colliding O2-O2 pair potential energy surface revealed that the UV-absorption by O2-O2 pair gives rise to
oxygen in Herzberg III state O2(A′ 3u) which is assumed to be responsible for singlet
oxygen production in the relaxation process
O2(A′ 3Δu)+O2(X
3g-)2 O2({a1g},{b1g
+})
with further collisional relaxation of b to a state. Singlet oxygen generation is assumed to follow the excitation of any encounter complexes X-O2 in the media (gas or condensed) containing oxygen.
The authors gratefully acknowledge the financial support of this work by the Russian Foundation for Basic Research (Grant № 12-03-00170-а), and Trushina A.P. is grateful for support from OPTEC company.
[1] A.P. Trushina, V.G. Goldort, S.A. Kochubei, A.V. Baklanov, Chem. Phys. Letters 2010, 485, 11-15.
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Physicochemical Transformations and Photochemical Reactions of High Disperse Pesticide Chemicals Relevant to
Ambient Conditions
Yuri N. Samsonov Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk Russia
The high-disperse substance state is a natural phenomenon. Many hundreds millions of tons of particulate matter enter the atmosphere annually from both the natural and anthropogenic sources. Anthropogenic portion is caused by heat-and-power engineering, motor fuel combustion, chemical industry, and application of pesticide chemicals in agriculture and forestry. Chemical reactions, which occur in the environment with pesticide chemicals (reactions with OH radicals, nitrogen oxides and ozone, direct and induced photodecompositions, photo-oxidation, photo-catalytic reactions), result in their chemical conversions and decomposition. Decomposition induced by sunlight seems to be very important for pesticide pollutants in the environment. Just the photochemical stage of decomposition, which generally is a many-stage chemical process, predetermines often the overall decomposition rate.
The high-disperse state demonstrates specific features for the rates and mechanisms of physicochemical transformations and photochemical reactions, which differ from the processes in coarse dispersal particulates and, even more, in ordinary liquid and solid “test-tube” assays. The point is that, due to fast evaporation of some chemical components (e.g., solvents) out of fine particles/films, their sizes, chemical compositions and phase states are permanently changing. The quickest changes should be in the smallest particles. Consequently, current chemical compositions of the particles of different diameters should be variable and dissimilar from both the initial formulation and each other. Solvent evaporation can cause the solidification and stratification of the residual intra-particle matter resulting in very slow diffusion of reagents within particle/film bodies, and in other specific physicochemical and chemical changes. In this regard, a chemical reaction in a fine particle/film is not a certain elementary chemical act, but a succession of the above physicochemical and chemical events depending on the particle size (film thickness) and the bulk structure, but the expressivities of the above-listed factors can be diverse and spontaneous under different conditions.
The reaction rates and the mechanisms of the direct and sensitized photochemical decompositions of several pesticide chemicals have been studied and hypothesized as applied to aerosol particles 0.12-1.3 μm in diameter deposited on glass plates, and films 0.03–0.3 μm thick. The plates with the particles or films have been exposed to a long-time, 3-20 h, artificial or solar irradiation, which simulated the sunlight photolysis of either the pesticide aerosols levitated in the air or the pesticide residues/spots at plants.
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Author index B Mel’gunov, M.A. 21
Bazhin, N.M. 33 Mulloev, N.U. 24
Baklanov, A.V. 34 Morozov, S.V. 31
C P Chen, Y 7 Pozdnyakov, I. 8, 25, 32
Cherepanova, S.V. 15 Plyusnin, V. 8, 25, 27, 32
D Panchenko, V.N. 21
Deng, N. 12, 26 Polienko, Yu.F. 31
Ding, W. 23 R G Remplel, A.A. 15
Gao, H 16 S Gerasimov, E.Yu. 15 Samsonov, Yu. N. 34
Glebov, E.M. 25 Selishchev, D.S. 18
Grigoryev, I.A. 31 Shchipunov, Yu.A. 15
Grilj, J. 30 Sherin, P.S. 30
Grivin, V. 8, 25 Sokolova, I.V. 5
Goldort. V.G. 34 T
J Tchaikovskaya, O.N. 5
Jhung, S.H. 21 Timofeeva, M.N. 21, 25
K Trushina, A.P. 34
Karetnikova, E.A. 5 Tsentalovich, Yu.P. 30, 31
Kochubei, S.A. 34 Tsybulya, S.V. 15
Kolomeets, A.V. 27 V
Kozhevnikova, N.S. 15 Vauthey, E. 30
Kozlov, D.V. 18 Vershinin, N.O. 5
Kozlova, E.A. 15, 17 Vorontsov, A.V. 14
L W Larionov, S.V. 27 Wang, Lei 6, 11
Lavrik, N.L. 24 Wang, Liguo 16
Lemke, A.A. 15 Wang, Yajie 23
Lemmetyinen, H. 27 Wang, Zongping 20
Liu, Yanxiang 26 Wu, F. 4, 6, 9, 11, 12, 23,
25, 26, 32
Liu, Zhongqi 6, 11 X
Liu, Zizheng 13 Xu, J 9, 23
Lyubina, T.P. 17 Y M Yurkova, M. 8
Mailhot, G 6, 11 Yanshole, V.V. 31
Mai, J. 9
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Z Zhang, Changbo 6, 11 Zhang, Hui 16 Zhang, Linjing 4 Zhang, Xu 25 Zhou, D. 10 Zuo, Y 7