Praseodymia gives rise to a rich phase diagram with a large number of phases between the limiting stoichiometries Pr2O3 and PrO2 that differ only slightly in oxygen content (PrnO2n−2). This chemical and crystallographic variability allows the system to release or incorporate lattice oxygen easily at sufficiently high temperatures and thus renders the material interesting as a catalyst for redox reactions according to a Mars–van Krevelen mechanism. Nanostructured praseodymia samples are investigated in this study with respect to their catalytic properties, focusing on methane oxidation and selective NO reduction by CO and CH4. To correlate catalytic activity and crystallographic changes, complementary high‐temperature X‐ray diffraction measurements have been carried out. The determined temperatures of transitions between different oxide phases agree well with peaks in the temperature‐programmed reduction measurements, confirming the direct connection between the availability of lattice oxygen and crystallographic transformations. The catalytic activity for methane oxidation and NO reduction sets in at 450–500 °C, at which temperature the starting material—mainly Pr6O11—transforms into the next oxygen‐depleted phase Pr7O12. With respect to NO reduction, the results show that it is possible to employ both methane and carbon monoxide as reducing agents in the absence of oxygen, in agreement with a Mars–van Krevelen mechanism. Nevertheless, the use of CO instead of CH4 offers considerable advantages, as no deactivation due to carbon residues takes place in this case. Whereas, in an excess of oxygen, NO reduction is inhibited independently of the reducing agent, it is shown that NO reduction can proceed if the O2 concentration remains below a critical concentration.

We investigated the decomposition of methanol over Pd-based catalysts and the influence of Co as a second metal. To obtain mechanistic information on the reaction, we prepared structurally well-defined systems for studies in the ambient pressure regime and systems suitable for UHV studies in a dual approach. For the ambient pressure regime, monometallic and bimetallic Co/Pd nanoparticles supported on MgO were prepared by a wet-chemical method. FTIR spectroscopy was used to analyze the surface species that formed on the catalysts in the interaction with methanol, and the catalytic performance was studied in continuous-flow reactors. We found that methanol is dehydrogenated to CO already at room temperature by the Pd and Pd-Co catalysts, but high steady-state conversion requires temperatures above similar to 150 degrees C. As could be shown by parallel studies of methanol decomposition on model catalysts prepared by physical vapor deposition under UHV conditions, CO desorption is the limiting factor at lower temperature. Pure Pd catalysts were found to be more active for methanol decomposition than the bimetallic Co-Pd catalysts. Although electronic effects in the bimetallic system facilitate desorption of CO at low temperature, this cannot compensate for the lower intrinsic activity of Co sites. We also investigated the influence of small amounts of oxygen on the decomposition of methanol. The activity of the Me/MgO catalysts was found to be higher in the presence of oxygen than in the absence of oxygen. Oxygen facilitates the removal of carbon species resulting from the C-O bond scission reaction channel. (C) 2008 Elsevier Inc. All rights reserved.

In the last decade, ionic liquids have shown great promise in a plethora of applications. However, little attention has been paid to the characterisation of the purity of these fluids, which has ultimately led to non-reproducible data in the literature. In order to facilitate specification of ionic liquids, a number of analytical protocols with their limits of detection (where available) have been compiled, including methods of other authors. In particular, quantitative methods have been developed and summarised for the determination of the total ionic liquid content, residual unreacted ionic liquid starting material and by-products (amines, alkylating agents, inorganic halides), solvents from extraction procedures and water, in addition to decomposition products and total volatiles.

Motivated by the prevailing need for a sustainable development and taking the principles of Green Chemistry as a starting point, the present paper describes new and updated findings regarding a sustainable product design for ionic liquids. The focus is on environmental risk. Nevertheless, cytotoxicity testing and first indicative results from a genotoxicity study extend present knowledge also with regard to possible effects on humans. The structural variability of commercially available ionic liquids as well as the abundance of theoretically accessible ionic liquids is illustrated and the consequences for an integrated risk assessment accompanying the development process are discussed. The side chain effect on toxicity for imidazolium type ionic liquids was confounded by more complex biological testing. Also, an influence of an anion on cytotoxicity is shown for the first time. Testing of presumed metabolites of the imidazolium type cations showed a significantly lower biological activity in cytotoxicity studies than their parent compounds. The importance of a purity assessment for ionic liquids is pointed out and a collection of methods that is believed to be adequate is presented. In addition to risk analysis, the use of life cycle analysis for the multi-objective problem of designing ionic liquids is sketched and an eco-design scheme for ionic liquids is proposed. In conclusion, the paper illustrates the complex nature of the development processes ionic liquids are currently undergoing and provides guidance on which aspects have to be kept in mind.

Pyrithione biocides are currently viewed as a major prospect for the replacement of tributyltin antifoulants in ship paints. The chromatographic behavior of 1-hydroxy-2-pyridinethione (pyrithione, PT), bis(2-pyridinyl)disulfide 1,1′-dioxide (PT2), and the metal complexes zinc [Zn(PT)2], iron [Fe(PT)3] and copper [Cu(PT)2] pyrithione, were investigated by means of UV–vis spectroscopy, ESI-MSn, HPLC-DAD and HPLC-ESI-MSnD. This revealed transformations of the analytes, which affect the development of adequate methods for species or environmental analysis of pyrithiones. PT transforms into copper- or iron- containing complexes and/or the oxidation product PT2, depending on the type of the stationary phase used in chromatographic analysis. Speciation complicates direct chromatography of [Zn(PT)2] and [Fe(PT)3].

The separation of selected 1-alkyl- and 1-aryl-3-methylimidazolium-based room temperature ionic liquid cations has been performed using reversed-phase high-performance liquid chromatography with electrospray ionization mass detection. The RP-HPLC method development started with the selection of a column taking into account especially the resolution of low molecular congeners of the selected group. Mobile phase composition was optimized for peak resolution, sensitivity and high reproducibility of retention values. The results of the method development were applied to the determination of exemplary ionic liquid species present in the medium used in cytotoxicity studies.

Parts of the area of the derelict World-War-II ordnance plant "Werk Tanne" (Clausthal-Zellerfeld, Harz, Germany) are heavily contaminated by chemicals resulting from TNT production and particularly by TNT itself. High soil contamination has to be treated with ex-situ methods but for the extended contamination of surface soil, in-situ phytoremediation is appropriate. The TNT-degrading potential of the rhizosphere of the planted trees and shrubs themselves is augmented by highly active mycorrhiza and white-rot fungi. A phytoremediation measure was established to scale with heavy machinery (soil grader), including the incorporation of white-rot fungi into the soil and planting of mycorrhized trees and shrubs. The effects of site preparation, mycorrhized rhizosphere and white-rot fungi on the degradation of TNT were assessed over one year using a complex monitoring scheme, including a battery of five biotests and field investigations of selected indicators (soil mesofauna, decomposition). The results of the monitoring showed the great influence of the grading procedure for site preparation, a diversified sensitivity of the biotest battery and complex reactions of the field indicators. The grading procedure effectively reduced the contamination (almost 90% within the first six months regardless of the initial levels). The phytoremediation measure as a whole reduced hazards of transport of nitro-aromatics by dust or leachate, initiated a secondary succession of the soil ecosystem that could transform the remaining TNT and metabolites over a longer period of time, and thus proved to be an effective decontamination measure applicable in large-scale technology.

In order to rise efficiency of the wastewater treatment in a refinery plant, several oxidation experiments were done, testing their applicability as an additional pretreatment method. The influence of treatment with low concentrations of H2O2 combined with stirring and UV light on degradation of organic compounds present in the refinery wastewater was studied. Oxidation of the total petroleum hydrocarbons occurs at relatively low concentrations of H2O2, additional UV irradiation slightly accelerates the process due to the increased formation of hydroxyl radicals. 1,2-dichloroethane and t-butyl methyl ether degrade in the similar manner and except for the lowest H2O2 concentration used (1.17mM), the reduction after 24h is total. The degradation rate for dichloromethane is the lowest one, depending both on hydrogen peroxide concentration and the presence of UV. Its maximum reduction of 83% was obtained using the highest applied peroxide concentration of 11.76mM.

Das in zwei vorangegangenen Veröffentlichungen dargestellte in situ-Verfahren zur Sanierung von TNT(Trinitrotoluol)-belasteten Bodens (‘Werk Tanne’) wird einer abschließenden Beurteilung unterzogen, die auf Grund des multidisziplinäre Ansatz mehrere Betrachtungsebenen integriert. Der maßstabsgerechte Einsatz der Bodenfräse bewirkt eine fast 90%ige Abreicherung der TNT-Belastung innerhalb der ersten 6 Monate, während die ADNT(Amino-dinitrotoluol)-Gehalte über den Untersuchungszeitraum von 1,5 Jahren relativ gleichmäßig abnehmen. Die Heterogenität der Verteilung der Nitroaromaten im Boden wird durch die Bearbeitung geringfügig reduziert. Ergebnisse aus Freilandmonitoring und Biotest-Batterie geben für die belasteten Varianten Hinweise auf ökotoxikologisch relevante Restroxizitäten und eine im Vergleich zur unbelasteten Fläche beeinträchtigte Erholungskapazität. Die mykorrhizierten Pflanzen sind zunächst von Bedeutung für die Standortsicherung und für eine Verbesserung der bodenökologischen Verhältnisse; ihre Rolle für die Abreicherung der Resttoxizität muss geprüft werden. Darüber hinaus wurde folgender Forschungsbedarf identifiziert: (1) Dynamik und Mechanismen des initialen starken TNT-Abbaus mit nachfolgender Stagnation; (2) Verhalten der Metabolite im Boden; (3) Langzeitwirkung des Verfahrens; (4) Möglichkeiten der Einrichtung des vielschichtigen Monitorings zur routinemäßigen Nutzung.