Search

A promising photolysis based technology to dechlorinate polychlorinated biphenyls (PCBs), extracted from soils, in alkaline isopropanol (IPA) as reaction medium has been proposed. To be marketable the impact of co-contaminants extracted along with the PCBs, on the photodechiorination process needs investigation. In this paper the effectiveness of the photodeclorination process on PCBs extracted from samples of a representative soil containing co-contaminants is reported. The pholodechl ori nation or PCBs extracted from weathered soils showed promising results of more than 76% dechlorination within the first hour of UV irradiation. Nearly complete dechlorination (96%) was achieved after 2 h of UV irradiation. To provide quantitative controlled appraisal of the effect of co-contaminants and explanation of the effects, dechlorination of neat Aroclor 1254 in the presence of the common co-contaminant, transformer oil, was evaluated. Further, the effect of transformer oil on some of the individual PCB congeners in the Aroclor mixture was also studied. The difference in the maximum percentage dechlorination of PCBs with and without transformer oil is 15%. Key words: PCBs, extraction, dechlorination, 2-propanol, transformer oil, co-contaminants. Une technologie prometteuse basee sur la photolyse est proposee pour dechlorer les BPC extraits des sols dans un milieu de reaction compose d'alcool isopropylique alcalin. Afin d'etre commercialisable, il faut examiner l'impact des co-contaminants extraits avec les BPC lors du processus de photo-dechloration. Dans eel article, l'efficacite du processus de photo-dechloralion sur les BPC extraits d'echantillons d'un sol representatif contenant des co-contaminants est presentee. La photo-chloration des BPC extrails de sols alleres a monlre des resultals de dechloraiion prometteurs de plus de 76% dans la premiere heure de rayonnement UV. Une dechloration presque complete (96 %) a ete realisee apres 2 heures de rayonnement UV. Pour fournir une evaluation quantitative controlee de l'effet des co-contaminants et I'explication des effets. la dechloration d'Aroclor 1254 pur en presence du co-contaminant commun, de l'huile de transformateur, a ete evaluee. De plus, l'effet de l'huile de transformateur sur certains des congeneres individuels des BPC dans le melange d'Aroclor a egalement ete etudie. La difference dans le pourcentage maximum de dechloration des BPC avec et sans huile de transformateur est de 15%. Mots-cles: BPC. extraction, dechloration. alcool isopropylique. huile de transformateur, co-contaminants. [Traduit par la Redaction], Introduction Recent successes on the dechlorination of polychlorinated biphenyls (PCBs) using UV, has opened possibilities of applying this technique to remediate PCB contaminated soils and sediments. The dechlorination of PCBs [...]

Conventional gas chromatography (GC) analysis of hydrocarbons displaying one broad peak provides limited information. Two GC analytical protocols using two-peak and three-peak approaches were developed to investigate transformer oil components and their degradation in soil by hydrogen peroxide. The two-peak method revealed transformer oil to be composed of 27 wt.% F2 fraction and 73 wt.% F3 fraction hydrocarbons. The three-peak method segregated the transformer oil into 40 wt.% light, 40 wt.% medium, and 20 wt.% heavy hydrocarbon fractions. In contrast to reports of success with several classes of lighter hydrocarbons, only limited degradations of transformer oil in soils by 15% and 30% hydrogen peroxide treatment was indicated by conventional one-peak analysis; two-peak analysis showed varying F2 and F3 fraction degradations with F2 fraction degradation being higher; three-peak analysis offered a richer understanding of the relative degradations of light, medium, and heavy fractions. The effect of a low pH environment on the degradation of transformer oil by hydrogen peroxide was evaluated using the three-peak method. It emerged that the degradation of the medium and heavier fractions of transformer oil was higher at pH 2.0. Key words: transformer oil, soil remediation, hydrogen peroxide, gas chromatography. L'analyse conventionnelle par chromatographie gazeuse (CG) des hydrocarbures montrant un large pic chromatographique ne donne que de l'information limitee. Deux protocoles d'analyse par CG utilisant des methodes a deux et a trois pics chromatographiques ont ete mis sur pied afin d'examiner les composantes de l'huile des transformateurs et leur degradation dans le sol en utilisant le peroxyde d'hydrogene. La methode a deux pics chromatographiques a indique que l'huile de transformateur etait composee de 27 % en poids de fraction d'hydrocarbures F2 et de 73 % en poids de fraction F3. La methode a trois pics chromatographiques a divise l'huile de transformateur en 40 % en poids de fraction legere d'hydrocarbures, 40 % en poids de fraction moyenne et 20 % de fraction lourde. Par rapport aux rapports relatant la reussite de l'utilisation de plusieurs classes d'hydrocarbures plus legers, des degradations limitees de l'huile des transformateurs dans les sols par traitement avec 15 et 30 % d'hydroxyde d'hydrogene ont ete determinees par l'analyse a un pic chromatographique. L'analyse a deux pics chromatographiques montrait des degradations variables des fractions F2 et F3, la fraction F2 se degradant mieux. L'analyse a trois pics chromatographiques permettait de mieux comprendre les degradations relatives des fractions legeres, moyennes et lourdes. L'effet d'un environnement a faible pH sur la degradation de l'huile de transformateur par le peroxyde d'hydrogene a ete evalue en utilisant la methode a trois pics chromatographiques. Il a ete decouvert que la degradation des fractions moyennes et lourdes de l'huile de transformateur etait meilleure a un pH de 2.0. Mots-cles : huile de transformateur, restauration des sols, peroxyde d'hydrogene, chromatographie gazeuse. [Traduit par la Redaction], Introduction The effectiveness of a particular remediation technology can be evaluated by the extent of mineralization and the compositional changes that occur during the treatment. With increasing popularity of chemical [...]

A novel pilot-scale flow through photoreactor has been designed with the intent to apply it in the field. The photoreactor uses a new plastic coil, instead of the conventional quartz tube. The photoreactor consists of six ultraviolet (UV) lamps with five around the coil and one at the center. Laboratory investigations were conducted using the photoreactor to treat neat Aroclor 1254 in alkaline isopropanol (IPA). The photoreaction is fast and efficient, even though the UV transmittances of the three plastic tubes investigated were lower than that of quartz. The reaction kinetics of the practical mixtures are explored. An analysis of five different constituent congeners of Aroclor 1254 indicated that higher congeners dechlorinate producing some of the lower ones, which are subsequently dechlorinated. The dechlorination of Aroclor 1254 was faster when water was added to the alkaline IPA-Aroclor solution. DOI: 10.1061/(ASCE)0733-9372(2007)133:6(646) CE Database subject headings: PCB; Ultraviolet radiation; Degradation; Reactors.

The following experiment examined quartz sandy soils from North Carolina and Simcoe, Ontario, Canada, and found that the chlorothalonil sorption properties were almost the same.

A study is done on composite TiO2 photocatalysts using solid state (super 29)Si nuclear magnetic resonance (NMR) and energy filtered transmission electron microscopy (EFTEM) is presented. Energy filtered transmission electron microscopy shows that titanium dioxide is found to be chemically bound to the surface of ZSM-5 via elimination of -OH between the surface of TiO2 and the zeolite.

Researchers from the University of Calgary, Canada investigated the kinetics of the uptake of pesticides in a wet organic soil sample from Mossy Point using proton magnetic resonance imaging

Research has been conducted on the photosubstitution wavelength dependence. Photoinduced electron transfer and the time-resolved Cr(CNPh) (sub)6 spectra have been investigated.

Research has been conducted on the electrochemical behavior of W(CO) (sub)4 (phen) to investigate the role of electron transfer in the photochemical reactivity of the compound. Results show that the photoreactivity of this complex can involve an electron-transfer pathway.

A new cross polarization magic angle spinning (CP-MAS) nuclear magnetic resonance technique allowed the accurate structural characterization of a fulvic acid and a humic acid. Results revealed that carbohydrate moieties play a significant role in the fulvic acid and contain the major chemical functionality. The spectra and relaxation parameters obtained allowed the development of two models for the fulvic acid and the humic acid.

A new approach to the use of high-field instruments for cross-polarization (CP) magic angle spinning (MAS) 13C NMR for analysis of humic materials is described. This technique consists of using a high sample spinning rate and a ramp CP pulse sequence, which, among other advantages, addresses chemical shift anisotropy effects. The theoretical aspects of high spinning rates on line broadening for nonrigid solids are reviewed. Also, the ramp CP pulse sequence and its implications for humic materials are discussed. It is shown that the highest resolution and most informative spectra can be obtained via a high-field instrument if the sample is spun at a rate higher than 0.25 of the anisotropy of the chemical shift of the aromatic moieties and a ramp CP pulse sequence is used. This study raises concerns that previous methods may have underestimated the amount of aromatic carbons in humic materials. Because of the similarities between humic materials and coals, this work may also have implications in the CP-MAS 13C NMR approach to coals.

The quenching of fluorescence of a fulvic acid by metal ions has been revisited in this study. Fluorescence quenching has been used in the past to establish the extent of metal ion binding to fulvic acids. Both emission and synchronous fluorescence show that the relationship between the extent of quenching and fraction of cation sites occupied is not linear. It was also found that synchronous fluorescence is a more revealing measurement than emission. Similar patterns of components can be assigned from both time-resolved fluorescent measurements and synchronous fluorescence. Correlation of these two distinct types of measurements suggests that a three-component treatment of fulvic acid luminescence may be physically meaningful. For this fulvic acid the three components may be assigned lifetimes and wavelength maxima as follows; [approximately] 50 ps (392 nm), [approximately] 430 ps (465 nm), and 4.2 ns (512 nm). The three-component model accommodates pH dependence and metal ion quenching. Stern-Volmer plots also support a (minimum) three-component model.

Time-resolved UV-vis absorption spectroscopy and nano-second flash photolysis analyze the photoreactions of three (CO)(5)ReMn(CO)(3) (alpha-diimine) complexes at different temperatures and pressures. Primary photoprocess in the metal-to-ligand charge-transfer excitation of these complexes is a fast CO dissociation from Mn center. High reactivities of these complexes are due to an available Mn coordination site and a weak Re-M bond.

Post excitation photochemical analysis of fast photooxidation of transition metal maleonitriledithiolate complexes reveal that the solvent dependence is independent of wavelength dependence. The purely electronic charge transfer to solvent state mixing controls wavelength dependence. Picosecond spectroscopy reveals the absence of reversible electron transfer.

The excitation into the ligand-field at 355 nanometers is used to calculate the picosecond (PS) time-resolved absorption spectra of W(CO)5(4-cyanopyridine). The excitation into the metal to ligand charge-transfer, MLCT at 532 nanometer absorption bands is used to calculate the spectra of W(CO)5(4-formylpyridine). The long-lived 3MLCT excited state is seen when the temporary absorption spectrum is being formed, which increases after biphasic unities. A sub-PS method is exhibited by the more rapid constituents, while the gradual constituents exhibit varying values for the two compounds, when subjected to 355nm of excitation in toluene solution.

A study has investigated the kinetic speciation of copper(II) (CuII) binding to hydrous ferric oxides. Kinetic studies suggests greater heterogeneity than previous equilibrium methods of Cu(II) speciation. Equilibrium methods failed to distinguish different binding sites for Cu(II).

The photochemical reaction of W(CO)4phen was studied using both ligand field (LF) and metal-to-ligand charge transfer (MLCT) excitation. A concentration dependence was observed under LF irradiation in CH2Cl2 where quantum yield increased from 0.011 to 0.017 when concentrations of (n-Bu)3P were increased from 0.015 to 0.36 M. This was similar to the observations for the MLCT band in the same system. Results with other reagents showed that quantum yield values increase significantly under conditions of increasing excitation wavelength for chlorinated solvents.

The energies and quantum yields for the formation of triplet states in aqueous solutions of Laurentian and Armadale fulvic acids were investigated using time-resolved photoacoustic spectroscopy together with magnetic circular dichroism spectroscopy. The results showed that the Laurentian sample featured yields which ranged from 0.79 to 0.28 for the pH range 2.0 to 9.5. The Armadale sample had a yield ranging from 0.82 to 0.35 for the same pH range.