Erzsébet Takács

Hydroxyl radical induced degradation of ibuprofen

Pulse radiolysis experiments were used to characterize the intermediates formed from ibuprofen during electron beam irradiation in a solution of 0.1mmoldm(-3). For end product characterization (60)Co γ-irradiation was used and the samples were evaluated either by taking their UV-vis spectra or by HPLC with UV or MS detection. The reactions of OH resulted in hydroxycyclohexadienyl type radical intermediates. The intermediates produced in further reactions hydroxylated the derivatives of ibuprofen as final products. The hydrated electron attacked the carboxyl group. Ibuprofen degradation is more efficient under oxidative conditions than under reductive conditions. The ecotoxicity of the solution was monitored by Daphnia magna standard microbiotest and Vibrio fischeri luminescent bacteria test. The toxic effect of the aerated ibuprofen solution first increased upon irradiation indicating a higher toxicity of the first degradation products, then decreased with increasing absorbed dose.

Ketoprofen removal by O3 and O3/UV processes: Kinetics, transformation products and ecotoxicity

Ozonation (O3) and its combination with ultraviolet radiation (O3/UV) were used to decompose ketoprofen (KET). Depending on the initial KET concentration, fourteen to fifty times faster KET degradation was achieved using combined O3/UV method compared to simple ozonation. Using both methods, formation of four major aromatic transformation products were observed: 3-(1-hydroxyethyl)benzophenone, 3-(1-hydroperoxyethyl) benzophenone, 1-(3-benzoylphenyl) ethanone and 3-ethylbenzophenone. In the combined treatment the degradation was mainly due to the direct effect of UV light, however, towards the end of the treatment, O3 highly contributed to the mineralization of small carboxylic acids. High (~90%) mineralization degree was achieved using the O3/UV method. Toxicity tests performed using representatives of three trophic levels of the aquatic ecosystems (producers, consumers and decomposers) Pseudokirchneriella subcapitata green algae, Daphnia magna zooplanktons and Vibrio fischeri bacteria showed that under the used experimental conditions the transformation products have significantly higher toxicity towards all the test organisms, than KET itself. The bacteria and the zooplanktons showed higher tolerance to the formed products than algae. The measured toxicity correlates well with the concentration of the aromatic transformation products, therefore longer treatments than needed for complete degradation of KET are strongly suggested, in order to avoid possible impact of aromatic transformation products on the aquatic ecosystem.

Elimination of diclofenac from water using irradiation technology

The effluents of wastewater treatment plants, usually directly emitted to the environment, often contain the anti-inflammatory drug diclofenac (DCF). The paper investigates DCF elimination using irradiation technology. Hydroxyl radical and hydrated electron reactive intermediates resulting from water radiolysis effectively degrade DCF and strongly reduce the toxicity of the solutions. ()OH attaches to one of the rings of DCF, and hydroxylated molecules, 2,6-dichloroaniline and quinoid type compounds are the products. Hydrated electron adds to the chlorine atom containing ring, in the reaction quinoid type compounds and 4-chloroacridine form. At a 0.1 mM DCF concentration, a ∼1 kGy absorbed dose is needed for the degradation of DCF molecules, but for mineralization of the products (in presence of O2) an order of magnitude higher dose is required. For irradiation of wastewater after biological treatment a ∼1 kGy dose is suggested. At this dose DCF and other drugs or metabolites present at μg L(-1) level are eliminated together with microorganism deactivation.

Analytical approaches to the OH radical induced degradation of sulfonamide antibiotics in dilute aqueous solutions

By combining a large variety of analytical techniques this study aimed at elaborating methods to follow up the degradation of sulfonamides in an advanced oxidation process (AOP): irradiation with ionizing radiation in dilute aqueous solution. In this process, besides other radicals, hydroxyl radicals are produced. As pulse radiolysis experiments show the basic initial reaction is hydroxyl radical addition to the benzene ring, forming cyclohexadienyl radical intermediates. In aerated solutions these radicals transform to peroxy radicals. Among the first formed products aromatic molecules hydroxylated in the benzene rings or in some cases in the heterocyclic rings were observed by LC-MS/MS. Chemical oxygen demand (COD) measurements indicate that at the early reaction period of degradation one hydroxyl radical induces incorporation of 1.5 O atoms into the products. Comparison of the COD and TOC (total organic carbon content) results shows gradual oxidation. Simultaneously with hydroxylation ring opening also takes place. The kinetics of inorganic SO4(2-) and NH4(+) formation, analyzed by ion chromatography, is similar to the kinetics of ring degradation (UV spectroscopy), however, there is a delayed formation of NO3(-). The latter ions may be produced in oxidative degradation of smaller N containing fragments. The S atoms of the sulfonamides remain in the solution (ICP-MS measurements) after degradation, whereas some part of the N atoms leaves the solution probably in the form of N2 (total nitrogen content (TN) measurements). Degradation is accompanied by a high pH drop due to formation of SO4(2-), NO3(-) and smaller organic acids. The degradation goes through many simultaneous and consecutive reactions, and with the applied methods the different stages of degradation can be characterized.

Radiation activation of cotton-cellulose prior to alkali treatment

The effect of alkali treatment on preirradiated cotton-cellulose was investigated using diffuse reflectance Fourier transformed infrared spectroscopy (DRIFT) and X-ray diffraction (XRD). The effect of two kinds of alkali solutions (NaOH and TMAH, tetramethyl ammonium hydroxide) on the crystalline structure of irradiated cotton-cellulose was compared. The transformation of cellulose I to cellulose II was observed applying DRIFT technique by the increase of the absorbance at 896 cm-1 and XRD. The results obtained by the two methods were in good correlation. An increase in carbonyl content (as detected by FTIR by measuring the absorbance at 1740 cm-1) was found in the samples due to oxidative degradation.

Degradation of organic molecules in advanced oxidation processes: relation between chemical structure and degradability.

Hydroxyl radical induced degradation of maleic acid, fumaric acid and 20 aromatic molecules was investigated in air saturated aqueous solutions. Hydroxyl radicals were generated by an advanced oxidation process (AOP), water radiolysis. Oxidation was followed by chemical oxygen demand (COD) and total organic carbon content (TOC) measurements. Up to ∼30-50% decrease of COD the dose dependence was linear. By the ratio of the decrease of COD and the amount of reactive radiolysis intermediates introduced into the solution the oxidation efficiencies were calculated. Efficiencies around 0.5-1 (O2 molecule built in products/OH) found for most of the compounds show that the one-electron-oxidant OH induces 2-4 electron oxidations. The high oxidation rates were explained by OH addition to unsaturated bonds and subsequent reactions of dissolved O2 with organic radicals. In amino substituted molecules or in Acid Red 1 azo dye, O2 cannot compete efficiently with unimolecular transformation of organic radicals and the efficiency is lower (0.2-0.5).

THE STATE OF WATER IN THERMORESPONSIVE POLY(ACRYLOYL-L-PROLINE METHYL ESTER) HYDROGELS OBSERVED BY DSC AND 1H-NMR RELAXOMETRY

Hydrogels that reversibly swell or shrink in water with decreasing or increasing temperature, respectively, were obtained by γ ray-induced polymerization of acryloyl-l-proline methyl ester in the presence of different amounts of a crosslinking agent. The role of water in the hydrated polymers was investigated by DSC and 1H-NMR relaxometry. From the curves of fusion of water determined by the former it was possible to ascertain that the amount of both freezing and non freezing water decreased with increasing the crosslinker percentage and/or swelling temperature. Moreover, at the temperatures higher than 37°C, the water absorbed by the different hydrogels is mostly present as non freezing water. The 1H-NMR relaxometry study enabled the spin–spin and spin–lattice relaxation curves to be analyzed. It was possible to distinguish three “populations” of protons and identify two of them with protons of freezing and non freezing water determined by DCS.

Propagation and size-dependent chain termination rate parameters in the polymerization of acrylates in aqueous solution as studied by pulse radiolysis

Abstract The radiation polymerizations of ethyl acrylate (EA) and hydroxyethyl acrylate (HEA) monomers in aqueous solutions were studied. For pulse radiolytic experiments, optical detection was used to measure the concentration of intermediates. The absorption spectra taken after a 2.6−μs pulse in N2O-saturated acidic solution of EA and HEA are shown to have maxima at 300 nm. It was proved by comparative measurements that these maxima belong to α-carboxy alkyl radicals. At a low acrylate concentration (below 1 mmol˙dm−3) and a relatively high dose/pulse value (above 30 yY), the decay of the transient signal occurs close to second-order kinetics. Average values of the termination rate parameters were calculated from aftereffect measurements. A computer program based on numerical integration was applied in order to estimate the individual rate parameters.

Pulse radiolysis of methacryloyl-l-proline methyl ester in dilute aqueous solution

ABSTRACT The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with a hydrogel-forming monomer, methacryloyl-L-proline methyl ester (MA-ProOMe), were studied by pulse radiolysis in dilute aqueous solutions and compared with the reactions of the acrylic derivative (A-ProOMe). The spectral and kinetic characteristics of the first step of OH, H and eaq- reactions with the two monomers are very similar. There are considerable differences in the next steps. In neutral solutions, the electron adduct of A-ProOMe decays in slow radical-radical reactions. The adduct of MA-ProOMe, however undergoes a fast irreversible protonation resulting in α-carboxyalkyl radical. The oligomerization reactions occurring in MA-ProOMe solutions are slow, and under adopted pulse radiolytic conditions, they are observable only at high monomer concentrations. In A-ProOMe solutions the reaction is significantly faster.

The new ECR ion source of the ATOMKI: A tool to generate highly charged heavy ion plasma and beam

Abstract Between 1993 and 1996 a 14 GHz electron cyclotron resonance (ECR) ion source has been designed and built in the ATOMKI. The ion source is aimed for the production of highly charged heavy ion beams from a wide range of the elements. One of the most important planned applications in the near future is its usage for low energy ion-atom collisions. This ion source is the first ECR ion source in Hungary and in Middle-Eastern Europe as well. The first plasma was successfully generated in February 1996 and the first extracted beam is expected in the fall of the year. This paper briefly reviews the history and progress of the ECR program and shows the ECR ion source itself. The results of some indirect plasma measurements (X-ray spectra) are shown and discussed.