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The effect of different organic and inorganic aqueous matrices on the photocatalytical degradation of dissolved atrazine and dichloroacetic acid (DCA) with immobilized TiO 2 was investigated. Two series of experiments were carried out at pH values around 7.1 for the degradation of atrazine and around 5.3 for the degradation of DCA. It is shown that the effects of the water constituents are completely different for the various substances and pH ranges. In pure deionized water 95% of the initial amount p = 1 mg/L of atrazine were degraded within 24 hours. Tap water as matrix led to a distinct lower degradation rate (factor 3). The single additives chloride, sulfate, phosphate, carbonate and DOC showed no decrease in the degradation rate. Especially in the case of phosphate and carbonate there was even a significant promoting effect. DEDIA, the doubly desalkylated and not dechlorinated product, occurred in higher concentrations than in the experiment without additives. In pure deionized water ρ 0 (DCA) = 1 mg/L was completely degraded within 330 min. By addition of any tested substance, organic or inorganic, the degradation rate of DCA, which is strongly dependent on the adsorption on the TiO 2 surface, decreased clearly. In the case of tap water the degradation rate decreased by a factor of 7.5. From the checked inorganic ions phosphate showed the strongest effect followed by sulfate, chloride and carbonate. Added DOC also had a significant influence on the degradation rate.

Environmentally relevant polar persistent organic pollutants (pharmaceuticals and diagnostic agents) were chosen according to human consumption and occurrence in the aquatic environment (sewage plant effluents, rivers and groundwater) to investigate their behavior during photocatalytic oxidation. From data compilation in the literature, the active metabolite clofibric acid of some lipid lowering agents, the anti-epileptic drug carbamazepine and the X-ray contrast media iomeprol were selected. The degradation of the persistent pollutant was monitored by HPLC/DAD/FLD. The study also focuses on the identification and quantification of possible degradation products by HPLC/DAD/FLD and HPLC/MS/MS. The degradation process was also monitored by determination of sum parameters and inorganic ions. Various aromatic and aliphatic degradation products have been identified and quantified. From analytical data, a possible degradation scheme for carbamazepine was proposed. Kinetic studies showed that the TiO2 photocatalyst P25 was more active in clofibric acid degradation than Hombikat UV100. For photocatalytic degradation of iomeprol Hombikat UV100 was more suitable than P25. In general the presence of NOM and carbamazepine retarded the photocatalysis of clofibric acid. Radiation attenuation, competition for active sites and surface deactivation of the catalyst by adsorption are the reason for that. The results of this work proof that photocatalysis is a promising technology to reduce persistent substances even if they are present in low concentrations or in a complex matrix.

The combination of semiconductor photocatalysis with cross-flow microfiltration accompanied by periodical back-washing was investigated in a pilot plant. The investigation included the testing of membrane materials because the membrane must resist the abrasion and the periodical back-washing. Another objective of this investigation was to assess the potential of two different TiO(2) materials (Hombikat UV100 and P25) for continuous photocatalytic degradation of persistent organic pollutants. The study focused on the long-term stability of the photocatalytic activity of TiO(2) during its continuous application. The combination of photocatalysis and cross-flow microfiltration allowed the separation and reuse of TiO(2) after the photocatalytic degradation of clofibric acid, carbamazepine and iomeprol. The investigations showed that the photocatalytic activity of P25 and Hombikat UV100 was constant during continuous usage over several days. This study indicates the high potential of the combination of heterogeneous photocatalytic oxidation processes with cross-flow microfiltration accompanied by periodical back-washing of the membrane. Thus environmentally relevant pharmaceuticals and X-ray contrast media can be transformed and mineralized in a continuous water treatment process.

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. Entwicklung einfacher und reproduzierbarer Immobilisierungstechniken fur TiO2 zur Photokatalyse beim Abbau von Schadstoffen in aquatischen Systemen Zur einfachen Herstellung reproduzierbarer photokatalytisch aktiver TiO2-Schichten auf Glastragern wurden zwei Immobilisierungstechniken getestet. Zum einen wurden kommerzielle TiO2-Materialien verwendet und zum anderen wurde TiO2 in situ auf dem Trager aus Tetraisopropylorthotitanat (TTIP) oder aus TiCl4 erzeugt. Dichloressigsaure (DCA), Clofibrinsaure und das Herbizid Terbuthylazin wurden als Modellschadstoffe zur photoka talytischen Aktivitatsuberprufung der TiO2-Schichten ausgewahlt. Anhand der Abnahme der DCA und der Zunahme ihres Abbauproduktes Chlorid wurde zwischen dem photokatalytischen Abbau und der Adsorption an den TiO2-Schichten unterschieden. Anhand des Terbuthylazinabbaus wurde untersucht, inwiefern sich die unterschiedlichen Eigenschaften der kommerziellen TiO2-Materialien P25 (Degussa) und Hombikat UV100 (Sachtleben Chemie) auf die Abbauwege auswirken. Einfach zu handhabende Verfahren zur Erzeugung von TiO2-Schichten auf Glastragern wurden entwickelt. Die beste photokatalytische Reproduzierbarkeit der TiO2-Schichten wurde mit Hilfe der Spraybeschichtungstechnik mittels kommerzieller TiO2-Materialien und mit Hilfe der Eintauch-Sol-Gel-Methode mittels TTIP erhalten. Die erzeugten TiO2-Schichten waren photokatalytisch sehr aktiv sowie mechanisch stabil. Sie zeigten eine konstante photokatalytische Langzeitaktivitat. In den bestrahlten Losungen wurde kein TiO2 nachgewiesen, das durch Abtragungen aus den TiO2-Schichten mobilisiert wurde.

The light-induced degradation of clofibric acid, carbamazepine, iomeprol and iopromide under simulated solar irradiation has been investigated in aqueous solutions suspended with different TiO 2 materials (P25 and Hombikat UV100). Kinetic studies showed that P25 had a better photocatalytic activity for clofibric acid and carbamazepine than Hombikat UV100. For photocatalytic degradation of iomeprol Hombikat UV100 was more suitable than P25. The results can be explained by the higher adsorption capacity of Hombikat UV100 for iomeprol. The study also focuses on the identification and quantification of possible degradation products. The degradation process was monitored by determination of sum parameters and inorganic ions. In case of clofibric acid various aromatic and aliphatic degradation products have been identified and quantified. A possible multi-step degradation scheme for clofibric acid is proposed. This study proves the high potential of the photocatalytic oxidation process to transform and mineralize environmentally relevant pharmaceuticals and contrast media in water.

The fate of pharmaceuticals in surface waters under solar irradiation was investigated. Photodegradation of pharmaceuticals caused by sun irradiation may be of major significance in the natural elimination process. Based on a data compilation from the literature, the lipid lowering agent metabolite clofibric acid, the iodinated X-ray contrast media iomeprol, which contribute to the adsorbable organic halogen compounds, and the antiepileptic drug carbamazepine were selected. The irradiation experiments were carried out in batch experiments with simulated UV-sunlight. The photodegradation of the pharmaceuticals showed a pseudo-first-order kinetics. The objective of this investigation was to demonstrate that the extent of photoinduced degradation of pharmaceuticals can vary significantly for the different pharmaceuticals and it strongly depends on the water constituents present in solution. The influences of different initial pharmaceutical concentrations, the presence of other pharmaceuticals like carbamazepine or clofibric acid and the presence of natural organic matter on the photochemical degradation rate of pharmaceuticals in aqueous solutions were investigated. Analyses of the pharmaceuticals and their photodegradation products were carried out by high performance liquid chromatography with diode-array and fluorescence detection.

The interaction of phenanthrene and 9-aminophenanthrene with natural organic matter (NOM) of different origin was investigated using the fluorescence quenching approach and the solid phase micro extraction method. The results of both methods are compared in terms of the influence of the concentration of the polycyclic aromatic compounds (PAC) as well as the concentration of the NOM on the observed binding constant. Due to the combination of steady-state and time-resolved fluorescence techniques it could be concluded that the observed fluorescence quenching was caused by a static interaction like a complex formation. While for phenanthrene both analytical methods showed no long term effects and the reaction equilibrium between NOM and phenanthrene was established within the first hour, for 9-aminophenanthrene a slow reaction kinetics (within days) was found indicating specific interactions between NOM and the amino group.

Photochemical and Photocatalytic Degradation of Carbamazepine, Clofibric Acid, Iomeprol and Iopromide