Theses of PhD Dissertation
University of Pannonia Doctoral School of Chemical and Environmental Sciences
Heterogeneous photocatalytic degradation of some X–CH2–CH(NH2)COOH amino acids
Written by Szabóné dr. Bárdos Erzsébet Chemical engineer
Supervisor Dr. Horváth Attila Associate Professor
University of Pannonia, Institute of Chemistry Department of General and Inorganic Chemistry Veszprém, 2013
1. INTRODUCTION, AIMS Most of the pollutants released from households, industry and agriculture can be decontaminated by traditional biological and physicochemical wastewater treatment. In spite of this fact more and more toxic materials come into the freshwaters (predominantly from industry) that could not be mineralized by these procedures. Therefore significant developments in chemical wastewater treatment technologies then their applications are required. It is important to use limited type and quantity of chemical additives, dominantly those decompose to natural materials, for economical, technological and health reasons. Further requirements are the applicability against very different pollutants and the low energy consumption. Common characteristic of the Advanced Oxidation Processes adequate to these challenges is the production of oxidative radicals, dominantly hydroxyl radicals, using solar energy or other kinds of energy, that oxidize the great variety of organic compounds. The heterogeneous photocatalysis became to be intensively studied research field at the end of the XXth. century. Many research groups study the methods based on photoactivity of the semiconductor particles using laboratory and pilot plant scale experimental set ups. The photocatalyst should be inert chemically and biologically, should be produced by relatively simple technology and finally, it should be rather cheap. Among the semiconductors investigated in photocatalytic systems it is the TiO2 that proved to be most advantageous from rather different points of view. However, the efficiency that can be achieved for decomposition of certain substrates, and which is determined by the efficiency of recombination of charge pair generated by photon absorption, is rather low. Hence, the activity of photocatalyst can be enhanced by the reduction of the probability of electron-hole pair recombination. For this purpose, one of the possible procedures is the photochemical deposition of noble or transition metal particles to the surface of the semiconductor particles. The oxalic acid, which is the simplest dicarbonic acid and produced by side products of various industrial procedures (metallurgical and textile industry) has been selected as reducing agent in our experiments preparing metal-deposited TiO2 nanoparticles. It has been proved by the preliminary experiments, that the efficiency of photocatalytic oxidation of the oxalic acid has been significantly enhanced by copper(II)- and silver(I)ions. Therefore one of the objectives of our studies was the careful investigation of photocatalytic decomposition of the oxalic acid in reaction mixtures containing TiO2 semiconductor particles and copper(II) and silver(I) ions, respectively.
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Recently, considerable attention has been directed to the photochemical study of the biologically active molecules. The various radical treatments are widely used procedures in medicine, hence it is very important to investigate the reactions of the fundamental materials of our organization, such as proteins with reactive radicals generated by photons. The amino acids as the building blocks of proteins are environmentally friendly molecules and excellent model substances in photocatalytic systems. Moreover, both functional groups of the amino acids (amino and carboxyl groups) may react with species generated by the excited semiconductor and other species formed at the surface of the excited semiconductor particles. We wanted to investigate in detail the photocatalytic decomposition, effects of pH of the aqueous phase of the reaction mixtures to the formation of surface complexes and to the initial rate of the photodecomposition of amino acid of type X–CH2–CH(NH2)COOH (where X= –OH, –SH, –COOH, –C6H5). Efficient hole scavenger (oxalic acid) and electron acceptor (silver(I)ion) have been applied separately and in combination to refine the mechanism of the photocatalytic decomposition of amino acids proposed earlier. Comparison of the results obtained by anaerob and aerob photocatalytic decomposition of C6H5–CH2–CH(NH2)COOH and using additives, such as H2O2 we wanted to reveal the reaction steps responsible for the opening of aromatic ring.
2. APPLIED EXPERIMENTAL METHODS The internal light sources of 40 W power showing emission spectrum peaking at 350 nm developed for photochemical applications and used for irradiation of the heterogeneous reaction mixtures are located at the central axis of the photoreactors. The constructions of the reactor mantles surrounding the light source are different due to the various procedures applied for homogenization of the reaction mixture and for feeding of the oxidizing agents, electron donating and accepting species, hole and electron scavengers, etc. The reactor mantle of the photoreactor in which the reaction mixture is circulated by continuously fed gas (air or inert gas, such as argon, nitrogen) with a flow rate of 40 dm3 h-1 has a glass tube between the internal (quartz) and external (glass) walls that separates the reactor volume of 2.8 dm3 into two parts. The gas fed up through a glass filter built in the bottom of the reactor pumps up the suspension of three phases (gas, liquid and solid particles) in the internal sphere, while the reaction mixture consist of solid particles and solution is moving down in the external part of the reactor. Feeding the model compound and semiconductor nanoparticles and the sampling can be performed through septum constructed near to the bottom of the reactor. Gas leaves the
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reactor at the top of the reactor through a stump. The absorbers and adsorbers built in the front of the reactor provide the purification of the feed gases, while those of hooked up after the reactor allows for the analysis of volatile products. This reactor is very useful when constant concentration of oxidizing agent (e.g. O2 in air) is required and the detailed analysis of volatile intermediates and products is not necessary. The other reactor has an undivided volume and it is connected to a buffer vessel and a peristaltic pump. The pump provides the continuous flow and mixing of the heterogeneous reaction mixture while the buffer vessel has several functions, such as homogenization of the reaction mixture by magnetic stirring, sampling and feeding oxidizing agent, electron donors, electron acceptors etc. Using this reactor sophisticated analytical procedures for identifying and quantitative analysis of intermediates and final products have been performed. The liquid phase of the samples taken from the reaction mixture by syringe have been separated by Millipore Millex-LCR membrane filter of 0.45 µm. The pH of the solutions was measured by SP10T electrode connected to Consort C561 instrument, the carbon content of the reaction mixtures has been determined by TOC-TN 1200 analyzer. The concentration of oxalic acid has been determined by classical titrimetric method using permanganate as oxidizing agent. The analytical concentration of silver(I)ion has been measured by (i) chloride ion selective electrode and (ii) ICP method, respectively. The concentration of copper(II) has been determined by atomic absorption method using Zeiss AAS 30 photometer. The concentration of the amine function of serine and aspartic acid was determined by fluorescamine. The luminescence spectra originated from the product of the reaction of amino acid and fluorescamine. The concentration of NH4+, NO2- and NO3- formed under irradiation was measured by spectrophotometric method. The changes in absorption and emission spectra of the liquid phase of the samples have been followed by S100 diode array spectrophotometer and Perkin Elmer LS 50B spectrofluorometer, respectively. The HPLC-MS investigations were performed by an Agilent 1100 Series LC/MSD Trap VL System.
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3. THESES I. It has been pointed out that the rate of photocatalytic oxidation of oxalic acid occurring in aqueous suspension of TiO2 nanoparticles is significantly increased by silver(I) and copper(II) ions. The photocatalytic oxidation undergoes in two periods in the presence of these metal ions. (i) The metal ions are reduced in the induction period, and silver(0) and copper(0) are deposited, and Cu(I) complexes are adsorbed onto the surface of the semiconductor particles. The reduced copper species are reoxidized by oxygen in thermal and photochemical reactions, while the deposited silver is not oxidized in the same conditions. (ii) In the second stage of the decomposition of oxalic acid the reaction rate is significantly increased. Then, it is constant until the considerable decrease of the concentration of organic substrate. The catalytic oxidation and reduction reactions also contribute to the oxidation of oxalic acid in aqueous suspension of TiO2 containing copper species under aerobic conditions. The increase of the analytical concentration of the metal ions leads to higher decomposition rate of oxalic acid, then a maximum of reaction rate is obtained – c(Cu2+)=2x10-4 M, c(Ag+)=10-4 M – and finally, the reaction rate decreases at higher metal concentrations. The increase in the rate of photocatalytic oxidation of oxalic acid is eight and fifth times at the optimal concentration of copper and silver, respectively. II. It has been proved that the photoinduced reaction of silver ion and oxalic acid occurring in aqueous suspension containing TiO2 nanoparticles (reduction of silver ion by the electron excited to the conduction band of semiconductor and the oxidation of oxalic acid by the hole of valence band left due to the promotion of the electron by absorbed photon) is stoichiometric (2Ag+ + H2C2O4 + 2hν → 2Ag + 2CO2 + 2H+). The oxygen absorbed from air does not influence the electron transfer reactions taking place at the surface of the excited semiconductor particles. It means that the photoinduced reduction of oxygen does not occur beside the ptotoinduced reduction of silver ion. III. The metal and metallic particles deposited on the surface of the semiconducting photocatalyst significantly increase the rate of the photocatalytic oxidation of oxalic acid. This is the consequence of the following effects: (i) The absorption spectrum of semiconductor is shifted to longer wavelengths, and hence the light fraction absorbed by the photocatalyst increases.
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(ii) The metal clasters deposited on the surface of the semiconductor particles are efficient electron traps, therefore the probability of recombination of electron-hole pairs is reduced and the lifetimes of these pairs get longer. (iii) A silver clusters of nanosize deposited on the surface of TiO2 can trap more than one electron excited to the conduction band of semiconductor. Therefore peroxide ion can be formed by two steps electron transfer from the silver cluster to the oxygen molecule adsorbed on the surface of Ag–TiO2 and the peroxide ion can dissociate to O- ions and the reaction of O- ion with photogenerated hole may lead to the formation of excited oxygen atom. This oxygen atom, as a very reactive species, can mineralize one oxalic acid molecule. IV. The parameters characterizing the equilibrium of the surface complexes and the rate of photocatalytic decomposition of amino acids of X–CH2–CH(NH2)COOH (X= –OH, –COOH, –C6H5) have been determined as a function of pH of the aqueous phase of the suspension containing TiO2 semiconductor nanoparticles, and it was proved, that: (i) The surface complex formation of the studied amino acids is favorable in the pH range, in which the zwitterionic form of the amino acid is the dominant species. The pH values of the border of this range and the pH at the maximum of the surface complex concentration (pHmax) are characterized by properties (electronic, protic, and stereo) of the X group. The order of the surface complex concentration measured at pHmax and equivalent concentrations of TiO2 (1 g dm-3) and amino acids (1 mM) is: aspartic acid >phenylalanine>serine. (ii) The strong correlation between the reaction rate and the equilibrium parameters confirms the key role of the surface complex formation in the photocatalytic decomposition of amino acids. V. Considering the data obtained by detailed study of photocatalytic decomposition of cysteine (CysSH) (H2S evolves from aqueous suspension containing cysteine and TiO2; pH of the aqueous phase increases in the initial stage of the photocatalytic reaction, then it is decreasing; sulfate ions are detected in the irradiated suspension; the concentration of sulfate ion increases and then it achieves a limiting value) the following conclusions have been drawn: (i) The significant increase of pH experienced at the initial stage of the photocatalytic reaction of cysteine is the consequence of the formation of NH3/NH4+. These species can be formed by:
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a.) Electron transfer from the conduction band of the excited semiconductor particle to the protonated amino group (–NH3+) followed by homolytic fission of C–N bond. b.) Electron accepting of –SH group results in H2S. The radical centre formed by the loss of thiol group in this reaction step migrates to the α-carbon atom, and the attack of a hydroxyl radical to this radical centre may lead to the formation of NH3/NH4+. (ii) Due to the deprotonation of thiol group an electron donating –S- is formed at pH values higher than 6, which can readily transfer electron to the photogenerated hole resulting in –S• radical centre. This radical centre reacts with oxidizing radicals (•OH, HO2•) formed at the surface of semiconductor particles and sulfate ion is formed by multistep reactions trough sulfenic (CysSOH), sulfinic (CysSO2H) and sulfonic (CysSO3H) acids as intermediates. These reactions lead to a relatively fast decrease in pH of the aqueous phase of the reaction mixture. The reaction between radicals (CysS•) formed in the primary electron transfer can also undergo resulting in cystine (CysS–SsyC) which is a reactive intermediate too. VI. The experimental results obtained by photocatalytic decomposition of aspartic acid, and serine over silver deposited titanium-dioxide confirm the key role of the formation of the surface complex of the substrate in photocatalytic systems. Increase in the formation constant of surface complex of serine and in the efficiency of the primary electron transfer processes over Ag–TiO2 compared to pure TiO2 results in the significant increase of the photocatalytic degradation of serine when the TiO2 is replaced by Ag–TiO2. In the initial stage of the photocatalytic reaction of cysteine over Ag–TiO2 photocatalyst Ag2S „catalyst poison” is formed, which is followed by a significant decrease in the rate of photocatalytic reaction. VII. The results of comparative photocatalytic experiments carried out by application of various TiO2 and their silver deposited form using oxalic acid as hole scavenger, coumarin as hydroxyl radical scavenger and aspartic acid which readily reacts with hole, electron and hydroxyl radical pointed out that: (i) It is the Aldrich TiO2 (100% anatase) that has the smallest photoactivity against the coumarin, while the most hydroxyl radicals are produced over its silver-deposited version under excitation. (ii) The increase in the photoactivity due to the silver deposition on titanium-dioxide surface is more effective for Aldrich and Fluka (100% rutile) than for Degussa P25 TiO2.
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(iii) The separation of the charge pair {ecb-, hvb+} generated by absorption of photons of higher energy than the band gap of given semiconductor is relatively efficient for bare Degussa P25 photocatalyst (25±5% rutile, 75±5% anatase), therefore the probability of charge recombination is slightly reduced by silver clusters deposited on the surface of
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semiconductor, while the silver nanoclusters acting as efficient electron traps on the surface of the other two titanium-dioxides significantly reduce the probability of recombination of photogenerated {ecb-, hvb+} pairs. VIII. It has been demonstrated that in aqueous suspension of TiO2 containing oxalic acid and amino acid (either aspartic acid or serine) the two reactants mutually inhibit the photocatalytic reactions of one another. It has been confirmed by a series of DRIFT spectra that the concentration of the surface complex of oxalic acid decreases faster than that of amino acid at the initial stage of the photocatalysis. The efficiency of the mutual inhibition is significantly reduced over silver deposited titanium-dioxide and thus, the concentration of surface complexes of both reactants decreases proportionally. These experimental facts have been interpreted by: (i) The first step of the photocatalytic reaction of amino acid is the electron transfer from the conduction band of the excited semiconductor particle to the protonated amino group of amino acid. (ii) This step can be followed by NH3 formation. The breaking of C–N bond competes with hydrogen abstraction forced by suitable molecules or radicals, such as •OH. In the aqueous suspensions of TiO2 containing oxalic acid of relatively high concentration (∼1 mM) the electron transfer from the surface complex of oxalic acid to the valance band hole of the excited semiconductor efficiently competes with the formation of hydroxyl radical. Thus, the formation of •COOH is dominant, and due to the c(•COOH)>>c(•OH) the hydrogen is abstracted from –NH3• with significantly higher efficiency by •COOH than by •OH, and the formation of ammonia is inhibited. The formic acid formed by this reaction is mineralized by two holes. It means that the oxidation of oxalic acid requires three holes in this case, while the photocatalytic oxidation of oxalic acid consumes only two holes in the absence of amino acid. (iii) The silver clusters deposited onto the titanium-dioxide nanoparticles are efficient electron traps, therefore the probability of recombination of electron-hole pairs decreases and on the other hand, the distance between the radicals formed by the primary electron transfer reaction (–NH3• and •COOH, respectively) increases. Thus the efficiency of the reaction
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taking place between these radicals and being responsible for the mutual inhibition of the photocatalytic decomposition of both reactants decreases. (iv) Considering the proposed mechanism it has been concluded that application of Ag– TiO2 photocatalyst and using molecules efficiently trapping holes together may be a useful method to reveal the rate determining reaction steps of photocatalytic reactions. IX. On the basis of careful analysis of the results obtained by photocatalytic decomposition of phenylalanine carried out in anaerobic and aerobic conditions the following conclusions have been drawn. (i) The primary reaction steps leading to the decomposition of the phenylalanine are: a.) electron transfer reaction steps occurring between the reactant adsorbed on the surface of photocatalyst and the excited semiconductor photocatalyst resulting in ammonia and carbon-dioxide, respectively, b.) attack of hydroxyl radical formed by the electron transfer between H2O/OH- and the photon generated hole on the phenyl group of phenylalanine. (ii) The carbon-dioxide produced by the reaction of radicals formed by primary electron transfer processes (Ph–CH2•CHCOO-surf, Ph–CH2•CHNH3+) contributes to the evolution of CO2 in the initial stage of the photocatalytic reaction of phenylalanine. (iii) The ammonia formed in the initial stage of the photocatalytic reaction of phenylalanine under aerobic condition is equivalent to that of obtained under anaerobic condition, that can be explained by the efficient electron transfer from the surface complex of O2•- formed by primary electron transfer to the amino group of phenylalanine. (iv) The formation of mono- and dihydroxy-phenylalanines guessed by absorption and luminescence spectra of the aqueous phase of the samples obtained by photocatalytic experiments have been identified by HPLC-MS method. It has been demonstrated that these compounds accumulate in anaerobic conditions, while form faster in the initial stage of photocatalysis under aerobic condition than under anaerobic condition, but after achieving concentration maximum they decomposes very rapidly under aerobic condition. (v) Step-wise hydroxylation of aromatic ring of the phenylalanine occurs upon exposure to UV-A radiation of the aqueous suspension of L-phenylalanine and TiO2 nanoparticles in anaerobic conditions, and only the aliphatic part of the molecule is degraded. No ring opening of the dihydroxylated isomers has been observed in these reaction mixtures even under prolonged irradiations. Ring opening occurs only aerobic system or in the presence of
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additives (e.g. H2O2) that produce oxygen containing radicals of high reactivity (e.g. O2•-, HO2•, O2(1∆g)) in photocatalytic reactions. (vi) It has been proved that in anaerobic photocatalytic systems containing Ag+ and phenylalanine ammonia is not produced until the complete deposition of silver and the reaction rate of formation of mono- and dihydroxy-phenylalanine is significantly faster than in the systems that have not silver ions. The rate of NH3 formation measured after the complete deposition of silver is identical (within the experimental error) with the initial rate of NH3 evolution determined by using bare TiO2 photocatalyst in anaerobic and aerobic conditions. X. It was found by consideration of the results obtained by detailed study of photocatalytic decomposition of the amino acids X–CH2–CH(NH2)COOH (X= –OH, –SH, –COOH, –C6H5) over TiO2 and Ag–TiO2 semiconductor nanoparticles, that: (i) The reaction steps initiating the photocatalytic decomposition of amino acids in suspensions possessing slightly acidic aqueous phase are primary electron transfer steps from the conduction band of the excited semiconductor to the protonated amino group of the substrate and the electron transfer from the deprotonated carboxyl group of the amino acid adsorbed to the surface of nanoparticle to the valence band of the excited TiO2 or Ag–TiO2, respectively. (ii) The X groups of the studied amino acids have various effects on photocatalytic decomposition: a.) The second carboxylic group of the aspartic acid accelerates the decomposition initiated by primary electron transfer steps with the electron transfer from this group to the valence band of the amino acid. b.) The –SH group of cysteine may be electron acceptor or electron donor, respectively against excited semiconductor hence the initial rate of the photocatalytic decomposition is determined by the rate of four electron transfer steps. c.) The aromatic ring of phenylalanine reacts with hydroxyl radicals formed by primary electron transfer from H2O to the valence band of the excited semiconductor particle. d.) The participation of the hydroxyl group of serine in the primary electron transfer processes could not be demonstrated.
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4. SCIENTIFIC PUBLICATIONS AND PRESENTATIONS Publications closely related to the dissertation 1. Erzsébet Szabó-Bárdos, Hajnalka Czili, Attila Horváth: „Photocatalytic oxidation of oxalic acid enhanced by silver deposition on a TiO2 surface” J. Photochem. & Photobiol. A: Chem., 154 (2003) 195-201 References: 86, External references: 78, Impf: 1.693 2. Erzsébet Szabó-Bárdos, Hajnalka Czili, Katalin Megyeri-Balog, Attila Horváth: „Photocatalytic oxidation of oxalic acid enhanced by silver and copper deposition on TiO2 surface” Prog. Colloid Polym. Sci., 125 (2004) 42-48 References: 5, External references: 2, Impf: 1.110 3. Erzsébet Szabó-Bárdos, Erika Pétervári, Viktória El-Zein, Attila Horváth: „Photocatalytic decomposition of aspartic acid over bare and silver deposited TiO2” J. Photochem. & Photobiol. A:Chem., 184, No 1-2 (2006) 221-227 References: 17, External references: 12, Impf: 2.098 4. Erzsébet Szabó-Bárdos, Bernadett Baja, Erzsébet Horváth, Attila Horváth: „Photocatalytic decomposition of L-serine and L-aspartic acid over bare and silver deposited TiO2” J. Photochem. & Photobiol. A: Chem., 213 (2010) 37-45 References: 3, External references: 2, Impf: 2.243 5. Erzsébet Szabó-Bárdos, Katalin Somogyi, Norbert Törő, Gyula Kiss, Attila Horváth: „Photocatalytic decomposition of L-phenylalanine over TiO2: Identification of intermediates and the mechanism of photodegradation” Applied Catalysis B: Environmental, 101 (2011) 471–478 References: 2, External references: 2, Impf: 5.625 Cumulative impactf.: 12.769
Publications related to the dissertation 1. Zoltán Zsilák, Erzsébet Szabó-Bárdos, Attila Horváth, Ottó Horváth: „Photocatalytic reduction of metals and oxidation of organic compounds in titanium dioxide suspension” A. Sánchez and S. J. Gutierrez (Eds.) Photochemistry Research Progress, Nova Science, Hauppauge, (2008) 479-505 2. Erzsébet Szabó-Bárdos, Zoltán Zsilák, Ottó Horváth: „Photocatalytic degradation of anionic surfactant in titanium dioxide suspension” Prog. Colloid. Polym. Sci., 135 (2008) 21-28 References: 2, External references: 2, Impf: 1.736
3. Erzsébet Szabó-Bárdos, Zoltán Zsilák, György Lendvay, Ottó Horváth, Otília Markovics, András Hoffer, Norbert Törő: „Photocatalytic degradation of 1,5-naphthalenedisulfonate on colloidal titanium dioxide” J. Phys. Chem., B.: 112 (46) (2008) 14500-14508 References: 5, External references: 2, Impf: 4.189 4. Erzsébet Szabó-Bárdos, Otília Markovics, Ottó Horváth, Norbert Törő, Gyula Kiss: „Photocatalytic degradation of benzenesulfonate on colloidal titanium dioxide” Water Res., 45 (2011) 1617-1628 References: 3, External references: 0, Impf: 4.865
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5. Aurél Ujhidy, Erzsébet Szabó-Bárdos, Ottó Horváth, Attila Horváth, Kristóf Schmidt: „Degradation of organic pollutants in photocatalytic reactors” Hung. J. Ind. Chem., 39 (3) (2011) 381-386 6. Ottó Horváth, Erzsébet Szabó-Bárdos, Attila Horváth, Katalin Somogyi, Otília Markovics: „Photocatalytic wastewater treatment” In Michael Palocz-Andresen, Róbert Németh, Dóra Szalay (eds.): Támop-Humboldt Colleg for Environment and Climate Protection 2009. December 3rd & 2010. October 21st in Sopron University of West Hungary, Univ. West. Hung. Press, Sopron, (2011) 176-181 7. Ottó Horváth, Erzsébet Szabó-Bárdos, Zoltán Zsilák, Gyula Bajnóczi: „Application of photocatalytic procedure combined with ozonation for treatment of industrial wastewater – a case study” Period. Polytech.-Chem., (accepted) References: 0, External references: 0, Impf: 0.269 Cumulative impactf.: 11.059
Publications not related to the dissertation 1. Erzsébet Szabó-Bárdos, Attila Horváth, Sándor Papp, Katalin Megyeri-Balog: "Hexaciano-ferrát(II) fotokémiai reakciói víz-alkohol oldószerelegyekben" Magyar Kémiai Folyóirat, 95 (1989) 373-381 References: 1, External references: 1, Impf: 0.158
2. Erzsébet Szabó-Bárdos, László Wojnárovits, Attila Horváth: "Pulse Radiolysis Studies on [Fe(CN)6]4- - Br- - CN- system in Ethylene Glycol - Water Solutions” J. Radioanal. Nucl. Chem., 147 (1991) 215-224 References: 6, External references: 6, Impf: 0.442 Cumulative impactf.: 0.600
Presentations in English 1. Attila Horváth, Erzsébet Szabó-Bárdos, Sándor Papp: „Photoredox reactions of complex cyanides of iron(II) in water-alcohol solutions” VIth SOPTROCC, Bratislava-Smolenice, April 19-22, 1988 2. Ottó Horváth, Zoltán Zsilák, Erzsébet Szabó-Bárdos: „Photocatalytic degradation of naphthalenesulfonic acids in wastewaters” 9th Conference on Colloid Chemistry, „Colloids for Nano- and Biotechnology”,Siófok, September, 2007 3. Ottó Horváth, Attila Horváth, Erzsébet Szabó-Bárdos, Zoltán Zsilák: „Photocatalytic mineralization of organic pollutants at laboratory and pilot scale” Pharmaceuticals and their degaradation products in the environment, REHPAD (Reduction of environmental risks posed by pharmaceuticals and their degradation products in process wastewaters through RO/NF membrane treatment) workshop, Varaždin, Croatia, October 23, 2009 4. Horváth Ottó, Erzsébet Szabó-Bárdos, Horváth Attila, Somogyi Katalin, Markovics Otília: „Photocatalytic wastewater treatment” Környezet és Klímavédelmi konferencia, Humbold-Kolleg, Sopron, 2010. október 21. 5. Ottó Horváth, Erzsébet Szabó-Bárdos, Attila Horváth, Orsolya Fónagy, Zoltán Zsilák: „Photocatalytic degradation of organic pollutants on colloidal TiO2” Workshop, Szeged, 2011. december 1-2.
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6. Ottó Horváth, Erzsébet Szabó-Bárdos, Zoltán Zsilák, Gyula Bajnóczi: „Application of photocatalytic procedure combined with ozonation for treatment of industrial wastewater – a case study” Műszaki Kémiai Napok 2012 (Conference of Chemical Engineering 2012) Veszprém, 2012. április 24-26. 7. Erzsébet Szabó-Bárdos, Orsolya Fónagy, Ottó Horváth, Zoltán Zsilák: „Application of heterogeneous photocatalysis combined with ozonation for wastewater treatment” 10th Conference on Colloid Chemistry, Budapest, August 29-31, 2012
Presentations in Hungarian 1. Szabóné Bárdos Erzsébet, Horváth Attila, Papp Sándor: „Vas(II)cianokomplexek fotoredoxi reakciói víz-alkohol oldószer elegyekben” MKE XXIII. Komplexkémiai Kollokvium, Szeged, 1988. május 26-28. 2. Szabóné Bárdos Erzsébet, Wojnárovits László, Horváth Attila: „Hexaciano-ferrát(II) impulzus radiolízis vizsgálata BrO3- elektronbefogó jelenlétében víz-alkohol elegyekben” MKE XXIV. Komplexkémiai Kollokviuma, Esztergom, 1989. június 21-23. 3. Szabóné Bárdos Erzsébet, Horváth Attila: „Külső mágneses tér hatása ruténium(II)komplexek fotoindukált redoxireakciójára” MKE XXVII. Komplexkémiai Kollokvium, Balatonfüred, 1992. május 25-27. 4. Szabóné Bárdos Erzsébet, Horváth Attila, Szabó Lajos, Szőke József, Bérces Tibor: „Cianidok lebontása fotokatalitikus reakciókkal” MTA spektrokémiai Mb. és MTA VEAB Környezettudományi Mb. és VE ankét Veszprém, 1996. április 18. 5. Szabóné Bárdos Erzsébet, Czili Hajnalka, Forrai Éva, Pétervári Erika, Horváth Attila: „Néhány szerves vegyület fotokémiai oxidációja TiO2 félvezető katalizátor felületén” MKE XXXVI. Komplexkémiai Kollokvium, Pécs, 2001. május 23-25. 6. Czili Hajnalka, Szabóné Bárdos Erzsébet, Horváth Attila: „Oxálsav fotooxidációja TiO2 félvezető katalizátor felületén átmeneti fémionok jelenlétében” MTA Reakciókinetikai és Fotokémiai Munkabizottsági ülés, Balatonalmádi, 2002. április 25-26. 7. Szabóné Bárdos Erzsébet, Czili Hajnalka, Horváth Attila: „Oxálsav fotooxidációja TiO2 félvezető katalizátor felületén átmeneti fémionok jelenlétében” MKE XXXVII. Komplexkémiai Kollokvium, Mátraháza, 2002. május 29-31. 8. Szabóné Bárdos Erzsébet, El-Zein Viktória, Pétervári Erika, Czili Hajnalka, Horváth Attila: „Dikarbonsavak fotooxidációja réz- és ezüstionok jelenlétében TiO2 félvezetőn” MTA Reakciókinetikai és Fotokémiai Munkabizottsági ülés, Gyöngyöstarján, 2003. október 30-31. 9. Szabóné Bárdos Erzsébet, Horváth Ottó, Zsilák Zoltán, Reich Lajos, Imre Károly: „Felületaktív anyagok fotokatalitikus lebontása szennyvizekben” XXIV. Országos Vándorgyűlés, Magyar Hidrológiai Társaság, Pécs, 2006. július 5-6. 10. Ujhidy Aurél, Bucsky György, Bárdos Erzsébet, Horváth Attila: „Kezeléstechnológia kiürült növényvédőszer-göngyöleg ártalmatlanítására” Műszaki Kémiai Napok, Veszprém, 2007. április 25-27.
11. Szabóné Bárdos Erzsébet, Zsilák Zoltán, Horváth Ottó, Kovács Margit: „Vegyipari szennyvizek fotoindukált mineralizációja” Országos Környezetvédelmi Konferencia, Siófok, 2007. szeptember 11-13.
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12. Zsilák Zoltán, Szabóné Bárdos Erzsébet, Horváth Ottó, Markovics Otília: „A Rába szerves szennyezőinek fotokatalitikus bontása” VIII. Környezetvédelmi analitikai és technológiai konferencia, Eger, 2007. október 10-12. 13. Szabóné Bárdos Erzsébet, Zsilák Zoltán, Horváth Ottó, Horváth Attila, Czili Hajnalka: „Szerves anyagok fotokatalitikus lebontása TiO2 felhasználásával” MTA, Környezeti Kémia Bizottság rendkívüli ülése, Veszprém, 2007. november 30. 14. Markovics Otília, Szabóné Bárdos Erzsébet, Horváth Ottó, Zsilák Zoltán, Lendvay György, Hoffer András, Törő Norbert: „Naftalin-szulfonátok fotokatalitikus bontása” Országos Környezetvédelmi Konferencia és Szakkiállítás, Siófok, 2008. szeptember 16-18. 15. Szabóné Bárdos Erzsébet, Somogyi Katalin, Horváth Attila, Markovics Otília, Törő Norbert, Zsilák Zoltán, Horváth Ottó: „Aromás vegyületek fotokatalitikus bontása titán-dioxid félvezető alkalmazásával” MTA Reakciókinetikai és Fotokémiai Munkabizottság ülés, Budatava, 2009. április 23-24. 16. Ujhidy Aurél, Szabóné Bárdos Erzsébet, Horváth Ottó, Horváth Attila, Schmidt Kristóf: „Szerves szennyezők lebontása fotokatalitikus reaktorokban” Műszaki Kémiai Napok 2011, Veszprém, 2011. április 27-29. 17. Szabóné Bárdos Erzsébet, Horváth Attila, Somogyi Katalin, Schmidt Kristóf, Horváth Ottó, Markovics Otília, Zsilák Zoltán: „Heterogén fotokatalízis a laboratóriumban és a környezetvédelemben” MKE I. Nemzeti Konferencia, Sopron, 2011. május 22-25. 18. Szabóné Bárdos Erzsébet, Fónagy Orsolya, Horváth Ottó, Zsilák Zoltán, Bajnóczi Gyula: „Ózonizálással kombinált fotokatalitikus eljárás alkalmazása szennyezőanyagok lebontására” X. Környezetvédelmi Analitikai és Technológiai Konferencia Sümeg, 2011. október 5-7. 19. Fónagy Orsolya, Szabóné Bárdos Erzsébet, Horváth Ottó, Zsilák Zoltán: „Szennyező anyagok lebontása kombinált fotokatalízissel” Műszaki Kémiai Napok 2012, Veszprém, 2012. április 24-26.
Posters 1. Attila Horváth, Erzsébet Bárdos, Sándor Papp: „Photoredox reactions of complex cyanides in different solvents and external magnetic fields” XIIth. International Conference on Photochemistry, Budapest, August 9-14, 1987 2. Erzsébet Szabó-Bárdos, László Wojnárovits, Attila Horváth: „Photochemical and pulse radiolysis study of hexacyanoferrate(II) in water-alcohol solvent in the presence of BrO3- electron scavenger” VIth. International Conference on Energy and Electron Transfer, Prague, August 14-18, 1989 3. Erzsébet Szabó-Bárdos, László Wojnárovits, Attila Horváth: „Photochemical and pulse radiolysis studies in [Fe(CN)6]4--BrO3--CN- system in ethyleneglycol-water solutions” Vth. Working Meeting on Radiation Interaction, Leipzig, September 24-27, 1990 4. Attila Horváth, Erzsébet Szabó-Bárdos, Zoltán Bakó, Ulrich Steiner: „The role of electron acceptors in magnetic field influenced electron transfer reaction of photoinduced [ Ru(bpy)3]2+” International Symposium on Magnetic Field and Spin Chemistry and Related Phenoma Konstanz, July 26-31, 1992
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5. József Szőke, Erzsébet Szabó-Bárdos, Attila Horváth: „Photocatalytic oxidation of cyanide TiO2 surfaces” Central European Photochemistry Conference, Krems, October 3-6, 1993 6. Erzsébet Szabó-Bárdos, Hajnalka Czili, Attila Horváth: „Photocatalytic oxidation of oxalic acid on TiO2 surface in the presence of transition metal ions” 14.th ISPPCC, Veszprém, July 7-12, 2001 7. Erzsébet Szabó-Bárdos, Hajnalka Czili, Attila Horváth: „Photocatalytic oxidation of oxalic acid enhanced by silver and copper deposition on TiO2 surface” 8.th Conference on colloid chemistry, Keszthely, September 18-20, 2002 8. Erzsébet Szabó-Bárdos, Attila Horváth: „Photooxidation of dicarboxylic acids over TiO2 surface in the presence of metal ions” Perspectives of photochemistry in the new millenium, Bad Gastein, March 7-11, 2004 9. Szabóné Bárdos Erzsébet, Baja Bernadett, Mézes József, Horváth Attila: „Nagyhatékonyságú fotooxidációs eljárás alkalmazása szerves szennyezők lebontására” XIX. Országos Környezetvédelmi Konferencia és Szakkiállítás Siófok, 2005. október 24-26. 10. Zsilák Zoltán, Szabóné Bárdos Erzsébet, Horváth Ottó: „Felületaktív anyagok bontása különböző fotokatalitikus módszerekkel” XIX. Országos Környezetvédelmi Konferencia és Szakkiállítás Siófok, 2005. október 24-26. 11. Szabóné Bárdos Erzsébet, Zsilák Zoltán, Horváth Ottó: „Szennyvizek oldószertartalmának fotoindukált mineralizációja” XIX. Országos Környezetvédelmi Konferencia és Szakkiállítás, Siófok, 2005. október 24-26. 12. Ottó Horváth, Zoltán Zsilák, Erzsébet Szabó-Bárdos, Lajos Reich, Károly Imre, István Tóth: „Photocatalytic degradation of anionic detergents in wastewaters” Central Europea Conference on Photochemistry, Bad Hofgastein, March 5-9, 2006 13. Erzsébet Szabó-Bárdos, Bernadett Baja, Gabriella Szentes, Attila Horváth: „Photocatalytic decomposition of some amino acids over bare and silver deposited TiO2” Central Europea Conference on Photochemistry, Bad Hofgastein, March 5-9, 2006 14. Szabóné Bárdos Erzsébet, Horváth Ottó, Zsilák Zoltán, Kovács Margit, Reich Lajos, Imre Károly: „Veszélyes ipari szennyvizek környezetbarát tisztítása” XX. Országos Környezetvédelmi Konferencia és Szakkiállítás, Balatonfüred, 2006. október 24-26. 15. Ottó Horváth, Zoltán Zsilák, Erzsébet Szabó-Bárdos: „Photocatalytic degradation of surfactants in reactors for wastewater treatment” XXIIIth International Conference on Photochemistry, Cologne (Germany) July 29 – August 3, 2007 16. Szabóné Bárdos Erzsébet. Zsilák Zoltán, Horváth Ottó, Kovács Margit: „Szerves szennyezők lebontása modellelegyekben és ipari szennyvizekben” Országos Környezetvédelmi Konferencia és Szakkiállítás, Balatonfüred, 2007. október15-17. 17. Szabóné Bárdos Erzsébet, Zsilák Zoltán, Kovács Margit, Horváth Attila, Horváth Ottó: „Nanoméretű félvezető részecskéken lejátszódó fotoindukált reakciók környezetvédelmi alkalmazása” Nanotechnológia, mint az innováció egyik hajtóereje (országos konferencia) Budapest, 2007. november 14. 18. Zoltán Zsilák, Erzsébet Szabó-Bárdos, Otília Markovics, Ottó Horváth, András Hoffer, Gyula Kiss, Norbert Törő: „Photocatalytic degradation of surfactants in wastewaters” Central Europea Conference on Photochemistry, Bad Hofgastein, February 10-14, 2008
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19. Zoltán Zsilák, Erzsébet Szabó-Bárdos, Otília Markovics, Ottó Horváth, György Lendvay, András Hoffer, Gyula Kiss, Norbert Törő: „Oxidative degradation of naphthalenesulfonates on colloidal titanium dioxide photocatalyst” Goteborg, July, 2008 20. Szabóné Bárdos Erzsébet, Zsilák Zoltán, Kovács Margit, Markovics Otília, Horváth Attila, Horváth Ottó, Lendvay György, Ujhidy Aurél, Hoffer András, Törő Norbert: „Szerves szennyezőanyagok fotoindukált lebontása” Országos Környezetvédelmi Konferencia és szakkiállítás, Balatonfüred, 2008. október 28-29. 21. Erzsébet Szabó-Bárdos, Attila Horváth, Ottó Horváth, Katalin Somogyi, Otília Markovics, Zoltán Zsilák: „Photocatalytic decomposition of phenylalanine and benzene sulfonic acid on TiO2” Central Europea Conference on Photochemistry, Bad Hofgastein, February 2010 22. Erzsébet Szabó-Bárdos, Katalin Somogyi, Attila Horváth, Norbert Törő, Gyula Kiss: „Photocatalytic decomposition of L-phenylalanine over TiO2: identification of intermediates and the mechanism of photodegradation” International Symposia on Advencing the Chemical Sciences, Challenges in Physical Chemistry an Nanoscience (ISACS2), Budapest, July 13-16, 2010 23. Erzsébet Szabó-Bárdos, Otília Markovics, Ottó Horváth, György Lendvay, Norbert Törő, Gyula Kiss: „Titanium dioxide mediated photocatalytic degradation of benzenesulfonate: intermediates and mechanism” International Symposia on Advencing the Chemical Sciences, Challenges in Physical Chemistry an Nanoscience (ISACS2), Budapest, July 13-16, 2010 24. Erzsébet Szabó-Bárdos, Otília Markovics, Ottó Horváth, György Lendvay, Norbert Törő, Gyula Kiss: „Photocatalytic degradation of benzenesulfonic acid on colloidal titanium dioxide” XIII. IUPAC Symposium on Photochemistry, Ferrara, July 11-16, 2010 25. Erzsébet Szabó-Bárdos, Ottó Horváth, Norbert Törő, Gyula Kiss, Krisztián Horváth, Péter Hajós: „Ion- and Liquid Chromatographic rofiling of Photocatalytic Degradation Pathways Environmental Pollutants” 36th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC2011 Budapest Symposium), Budapest, June 19-23, 2011 26. Erzsébet Szabó Bárdos, Ottó Horváth, Attila Horváth, Orsolya Fónagy, Zoltán Zsilák: „Combination of heterogeneous photocatalysis with ozonation for degradation of organic pollutants” Central European Conference on Photochemistry 2012 Bad Hofgastein, February 5-9, 2012 27. Fónagy Orsolya, Szabóné Bárdos Erzsébet, Horváth Ottó, Zsilák Zoltán: „Környezetbarát eljárás felületaktív anyagok mineralizációjára” VIII. Kárpát-medencei Környezettudományi Konferencia, Veszprém, 2012. április 18-21. 28. Erzsébet Szabó-Bárdos, Orsolya Fónagy, Ottó Horváth, Krisztián Horváth, Péter Hajós, Zoltán Zsilák: „Mineralization of benzenesulfonate by heterogeneous photocatalysis combined with ozonation” 10th Conference on Colloid Chemistry, Budapest, August 29-31, 2012
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