Development of Easy and Reproducible Immobilization Techniques Using TiO2 for Photocatalytic Degradation of Aquatic Pollutants

Two main routes of methods for the preparation of photocatalytic active titanium dioxide films on glass substrates were investigated: (1) the use of titanium dioxide powder and (2) the in situ generation of the catalyst via hydrolysis of titanium tetraisopropoxide (TTIP) or TiCl₄. The activities of the catalyst films were evaluated by measuring the degradation of dichloroacetic acid (DCA), clofibric acid, and terbuthylazine used as model organic compounds. The concentration decrease of DCA and the concentration increase of chloride ions as the decomposition product allowed to distinguish between photocatalytic degradation of DCA and adsorption onto the TiO₂ films. Furthermore, TiO₂ films of the commercially available materials P25 (Degussa) and Hombikat UV100 (Sachtleben Chemie) were used to investigate whether there was a difference in the degradation pathways of terbuthylazine as a model compound. For the experiments mini flow‐through reactors were constructed. The investigated immobilization techniques were easy to handle without need of any expensive equipment. All TiO₂ coatings showed good photocatalytic activities and mechanical stabilities with efficient long‐term stabilities. The best immobilization reproducibility was achieved by the spray coating technique and by the in situ method with the dipping sol‐gel process starting by TTIP. During the continuous use of the TiO₂ films no TiO₂ particles were found in the irradiated solutions.     

Rn-generated206Pb in hydrothermal sulphide minerals and bitumen from the Ventersdorp Contact Reef, South Africa

Summary The auriferous conglomerate horizons (reefs) in the Witwatersrand Basin of South Africa are in many places cut by hydrothermal quartz veins that frequently contain sulphide, bitumen, and, less commonly, free gold. New Pb isotopic results for the Ventersdorp Contact Reef which has experienced particularly intense hydrothermal alteration, reaffirm the radiogenically enriched nature of the Pb in this reef and provide additional insight into its origin. This study focuses on analyses of galena, chalcopyrite, pyrrhotite, and bitumen from quartz veins, which presumably formed during the 2.020 Ga Vredefort meteorite impact event. The radiogenic, mainly uranogenic, component of the Pb appears to have been derived almost entirely from uraninite in the surrounding reef rock. Assigning a 2.02 Ga age of mineralization and constructing secondary isochrons for paragenetically early galena and chalcopyrite, ages of the source uraninite are calculated as 2.6–2.4 Ga. No special significance is ascribed to these source ages, which likely reflect extensive radiogenic Pb loss from originally somewhat older detrital uraninite during transport, sedimentation, and post-burial alteration. Analyses of detrital(?), syngenetic, and epigenetic pyrite from a reef conglomerate define a subsidiary linear array with a considerably shallower slope. Interpreted as a secondary isochron, the array gives an implausibly young mineralization and/or source age indicative of a superimposed isotopic disturbance.Five analyses of paragenetically late chalcopyrite and pyrrhotite plot on a²⁰⁷Pb/²⁰⁴pb versus²⁰⁶Pb/²⁰⁴Pb diagram with nearly constant²⁰⁷Pb/²⁰⁴Pb of 24.1–24.6 despite a huge range in²⁰⁶Pb/²⁰⁴Pb from 60–230. This trend is further revealed by Pb with similar²⁰⁷Pb/²⁰⁴Pb but still higher²⁰⁶Pb/²⁰⁴Pb ratios (up to 949) in bitumen globules deposited on quartz crystals lining cavities in the veins. This nearly horizontal array cannot be interpreted as a secondary isochron, and requires the addition of virtually pure²⁰⁶pb to a more normal, radiogenically-enriched Pb. The most plausible explanation for this decoupling of the²³⁸U and²³⁵U decay schemes is that an intermediate daughter isotope, most likely²²²Rn, diffused from uraninite and was selectively captured by the bitumen where it subsequently decayed to²⁰⁶Pb. Whether the 206 Pb was acquired mainly at the time of hydrothermal activity by fluids at elevated temperatures, or more or less continuously until the present remains unresolved.

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Durch Rn erzeugtes²⁰⁶Pb in hydrothermalen Sulfid-Mineralen und Bittunen vom Ventersdorp Contact Reef, Südafrika

Zusammenfassung Die goldhältigen Konglomeratehorizonte (Reefs) im Witwatersrand Becken von Südafrika werden vielerorts von hydrothermalen Quarzadern durchkreuzt, die verschiedene Sulfide, Bitumen, und Spuren von Gold führen. Neue Pb-Isotopendaten vom Ventersdorp Contact Reef (VCR), welches besonders intensive hydrothermale Veränderung erfahren hat, bestätigen die abnormal radiogene Natur des Pb in diesem speziellen Reef. Darüber hinaus führen sie zu einem neuen Verständnis der Herkunft dieses Pb. Schwerpunkt dieser Studie war die Analyse von Bleiglanz, Kupferkies und Bitumen in Quarzadern, deren Bildung dem 2.020 Ga Vredefort Impaktereignis zugeschrieben wird. Die radiogene, hauptsächlich uranogene Pb-Komponente kann beinahe ausschließlich von Uraninit im umgebenden Reef abgeleitet werden. Von sekundären Isochronen, deren Berechnung auf der Annahme eines Mineralisationsalters von 2.02 Ga beruht, lassen sich Alter von 2.6–2.4 Ga für den Uraninit ableiten. Diesen Altern wird jedoch keine weitere Bedeutung beigemessen, da sie wohl eher erheblichen radiogenen Pb-Verlust eines ursprünglich etwas älteren Uraninit während Transport, Sedimentation und spät- bis post-diagentischer Alteration widerspiegeln. Analysen von detritischem (?), syngenetischem und epigenetischem Pyrit von einem Reef-Horizont folgen einem abweichenden Trend mit erheblich geringerer Neigung in einem²⁰⁶Pb/²⁰⁴Pb versus²⁰⁷Pb/²⁰⁴Pb Diagramm. Als sekundäre Isochrone betrachtet, entspricht dieser Trend entweder einem unwahrscheinlich jungen Alter oder er drückt eine spätere Störung des Isotopensystems aus.Fünf Analysen von paragentisch spätem Kupferkies und Magnetkies haben ein nahezu konstantes²⁰⁷Pb/²⁰⁴Pb Verhältnis von 24.1–24.6 trotz einer enormen Spanne in deren²⁰⁶Pb/²⁰⁴Pb Verhältnissen (60–230). Dieser Trend wird weiters duch Pb mit ähnlichen²⁰⁷Pb/²⁰⁴Pb aber noch höheren²⁰⁶Pb/²⁰⁴Pb Verhältnissen (bis zu 949) in Bitumen-Aggregaten innerhalb von Quarz-Drusen unterstrichen. Diese extrem flache Datenverteilung in einem²⁰⁷Pb/²⁰⁴Pb versus²⁰⁶Pb/²⁰⁴Pb Diagramm kann nicht als sekundäre Isochrone interpretiert werden, sondern verlangt die Zufuhr von praktisch reinem²⁰⁶Pb zu eher normalem, radiogen angereichertem Pb. Diffusion eines intermediären Tochterisotops, höchst wahrscheinlich²²²Rn, und selektiver Einbau desselben in das Bitumen mit anschließendem Zerfall zu²⁰⁶Pb halten wir für die naheliegendste Erklärung dieser Entkoppelung der²³⁸U- und²³⁹U-Zerfallsreihen. Offen bleibt die Frage, ob der Einbau des²⁰⁶Pb hauptsächlich zum Zeitpunkt der hydrothermalen Überprägung oder mehr oder weniger kontinuierlich bis heute stattgefunden hat.

     

Influence of Oxidative Treatment on the AOX‐formation Potential of Aromatic Sulfonates

Aromatic sulfonates can be found in drinking water. Thus, they must have passed water treatment and survived ozonation. Degradation of aromatic sulfonates can be achieved by the UV/H2O2‐process. Since drinking water is often treated with chlorine as a disinfectant, the formation of disinfection by‐products has to be considered. Therefore, the production of AOX (on activated carbon adsorbable organic halogens) after chlorination of the sulfonates with and without preoxidation was investigated. Instead of the analysis of the individual degradation products, the determination of the sum parameter AOX was used as a fast screening method. The investigated sulfonates were: anthraquinone‐2‐sulfonate, naphthalene‐2‐sulfonate, 2‐aminonaphthalene‐1‐sulfonate, and 4,4′‐diaminostilbene‐2,2′‐disulfonate. All sulfonates containing amino groups showed high potentials of AOX formation. The preoxidation with ozone increased the potentials of AOX formation in general. Treating the sulfonates by using the UV/H2O2‐process, the formation potentials run to zero after going through a maximum value.     

Metal Distribution in Different Size Fractions of Natural Organic Matter

In this paper, size‐exclusion chromatography (SEC) was used to determine the metal concentration in different size fractions of a bog lake water. Two methods were applied: (a) preparative SEC with off‐line metal concentration analysis and (b) direct coupling of an analytical SEC system on‐line with an inductively‐coupled plasma mass spectrometer (ICP‐MS). In the preparative SEC measurements, maximum concentrations were found for different metal ions in different size fractions of the natural organic matter (NOM). Normalization of metal concentrations to dissolved organic carbon concentration (DOC) yielded two maxima in the high and in the very low molecular‐weight fractions. Whereas good recoveries were found for Al, Fe, and Ni, only 40% were obtained for Pb. This indicates that Pb formed labile complexes with NOM, and hence could strongly interact with the column material. In the experiments with the analytical SEC‐ICP‐MS system, the same trends were observed, but with even lower recoveries than in the preparative system. Sample preconcentration and storage were also investigated with respect to decrease in metal concentration. During the ultrafiltration preconcentration step Al and Fe were removed only to a small extent, whereas about half of the initial Pb was lost. This indicates that Al and Fe were mainly bound to high molecular‐weight fractions of NOM. In contrast to that, Al and in particular Fe were removed from solution more than proportionally with respect to DOC because of aggregation of the NOM during storage, whereas Pb and Ni were concentrated relative to the DOC.     

Spectroscopic Characterization of Fulvic Acid Fractions of a Contaminated Groundwater

Two fulvic acid (FA) samples taken from a former gas production facility in the Southwest of Germany were characterized using advanced fluorescence techniques. Steady-state fluorescence (fluorescence excitation, synchronous fluorescence) as well as time-resolved fluorescence were applied. Distinct differences between the sample B22 FA taken within the contamination plume and the sample B53 FA taken downstream were found. Comparison with a model compound for metabolites and humic substances revealed that due to the downstream passage the characteristics of the dissolved organic matter became more humic-like. The assignment of single classes of compounds in the sample B22 FA is discussed in terms of their synchronous fluorescence spectra and fluorescence decay time distribution.     

Problems and Solutions in Pesticide Analysis Using Solid‐phase Extraction (SPE) and Gas Chromatography Ion‐trap Mass Spectrometry Detection (GC‐MS)

In the present study an analytical method was tested for the determination of selected pesticides and metabolites using solid‐phase extraction (SPE) and gas chromatography ion‐trap mass spectrometry (GC‐MS). The extraction efficiency of C18, Isolut ENV+, and Lichrolut EN for SPE was compared for trifluralin, fenitrothion, endosulfan, propargite, 2,4‐D, 3‐methyl‐4‐nitrophenol, 2‐(4‐tert‐butylphenoxy)cyclohexanol, endosulfan sulfate, and 2,4‐dichlorophenol. Isolut ENV+ and C18 showed good results as sorbents and acetone as an elution solvent for SPE for the selected pesticides. Recoveries varied between 36% and 176% with a relative standard deviation of 2...18%. Because of coextracts from the SPE materials, recovery values higher than 100% were obtained for fenitrothion, endosulfan sulfate, and 2,4‐D with C18 as well as for endosulfan sulfate and 3‐methyl‐4‐nitrophenol with Isolut ENV+. A standard addition method was used to verify the occurrence of coextracts in the sample after SPE.