Rupert Bauer

The photo-fenton reaction and the TiO2/UV process for waste water treatment − novel developments

Abstract Solar applications of photochemical waste water oxidation methods driven by UV and/or visible light, especially TiO2/UV and the Photo-Fenton reaction (Fe2+/H2O2/UV-VIS), have been investigated. Degradation results of 4-Chlorophenol and some other model compounds at laboratory scale are discussed. A photoreactor with immobilized TiO2 has led to a higher quantum efficiency than the suspension treatment. Electron densities were calculated to predict the oxidizing properties of UV irradiated TiO2. Al doped TiO2 powders showed better performance than undoped samples in laboratory scale degradation experiments. Experiments with different waste waters (e.g. landfill leachates, plastics industry, etc.) using the Fe2+/H2O2/UV-VIS system in a photoreactor prototype are reported. Solar treatment of a model waste water in a glass basin has been investigated. Furthermore, experiments performed at the Plataforma Solar de Almeria (Spain) with different methods, reactor types and waste waters are compared. According to a comparison of costing the solar driven Fenton reaction is a cheap method for water treatment, also for highly contaminated effluents.

New Reactor Design for Photocatalytic Wastewater Treatment with TiO2 Immobilized on Fused-Silica Glass Fibers: Photomineralization of 4-Chlorophenol

A new reactor design for the use of titanium dioxide-coated fused-silica glass fibers for wastewater treatment is described. The manufacture of the coating of the fibers is explained in detail. 4-Chlorophenol was used as the test compound. The influences of temperature and irradiation wavelength and the effect of hydrogen peroxide addition were investigated. Activation energy for the initial attack of an OH radical on 4-chlorophenol was calculated to be 20.6 kJ/mol. Degradation rates and quantum yields obtained with this reactor were compared with results measured with Degussa P25 TiO[sub 2]-slurry treatment. With the present design, the degradation rate of 4-chlorophenol is 1.6 times higher and the destruction of the total organic carbon (TOC) is 2.8 times faster. 35 refs., 6 figs., 4 tabs.

The Photo-Fenton Oxidation - a Cheap and Efficient Wastewater Treatment Method

Advanced Oxidation Processes (AOPs) for wastewater treatment are gaining more importance since biological treatment plants are often not sufficient for highly contaminated or toxic wastewaters. In order to find out the most efficient and cheap AOP, investigations were concentrated on methods that can use sunlight. The systems TiO2/UV, Fe2+/H2O2/UV (Photo-Fenton reaction), Fe2+/O2/UV and Fe2+/O3/UV were compared. Since the Photo-Fenton system was the most effective, pilot plant experiments with industrial wastewaters and sunlight experiments were carried out. Finally a rough cost estimate shows that Photo-Fenton treatment with sunlight is far cheaper than other available AOPs, namely ozonization.

Photo-Fenton treatment of water containing natural phenolic pollutants

Phenolic compounds are known to be present in high concentrations in various types of agro-industrial wastes. As they are highly biorecalcitrant, the possibility of treatment by advanced oxidation processes should be investigated. In this work, six model phenolic compounds (vanillin, protocatechuic acid, syringic acid, p-coumaric acid, gallic acid and L-tyrosine) were chosen for a demonstration of degradation by photo-Fenton reaction, under artificial light in laboratory experiments in Vienna and under sunlight in pilot-plant experiments at the Plataforma Solar de Almería in Spain. All compounds were completely mineralised. No non-degradable intermediates were produced, either in experiments with single substances or in a more complex matrix of a mixture of phenolic compounds. The expected selectivity of the photo-Fenton reaction for aromatic compounds was proven by comparison of the decrease in total organic carbon with the removal of total phenolic content.

UV-O3, UV-H2O2, UV-TiO2 and the photo-fenton reaction : comparison of advanced oxidation processes for wastewater treatment

Abstract Results of the photochemical mineralization of 4-chlorophenol (4-CP) and of a wastewater from dyehouse industry by the methods UV/O3, UV/H2O2, UV/TiO2 and UV/H2O2/Fe2+ (photo-Fenton reaction) are reported and compared. Under illumination with a 150 W high pressure mercury lamp, TOC-degradation efficiency for 4-CP had the following order: V/H2O2/Fe2+ > UV/O3 > UV/H2O2 = UV/TiO2. Complete decolourization of the dye waste occurred within 20 minutes with ozone. A mineralization grade of approximately 75% was reached after 90 minutes with the photo-Fenton reaction and after 150 minutes with UV/ozone. The combinations UV/TiO2 and UV/H2O2 were found to be less efficient for bleaching and degradation of the dye waste. Furthermore, a novel combination for wastewater treatment, UV/Fe2+/O3, was investigated. Addition of Fe2+ to the UV/ozone process increased the mineralization rate of 4-CP while no significant effect on dye waste degradation could be observed.

Applicability of the Photo-Fenton method for treating water containing pesticides

Abstract The Photo-Fenton process, i.e., the system Fe2+/H2O2/UV-Vis, was successfully applied to a mixture of ten commercially available pesticides that served as a model for a proposed recycling plant for pesticide bottles. Experiments with single pesticides revealed that although all of them were degradable, there were remarkable differences concerning the reaction rate. Sunlight driven pilot scale experiments with the complete mixture were conducted. For the pesticide mixture the initial pollutant concentration and the amount of iron was varied. The addition of oxalate and different modes of oxidant addition were tested in order to improve the process. Thereby, the reaction rate was increased, while the final degree of TOC reduction was affected only slightly. All the experiments carried out were considerably faster than the previously published results of degradation tests that applied solar driven TiO2/UV and TiO2/Na2S2O8/UV photocatalysis.

Photoelectrocatalytic degradation of 4-chlorophenol and oxalic acid on titanium dioxide electrodes

Photocatalytically active thin TiO(2) films were produced by spin-coating or dip-coating an alkoxy precursor onto a transparent conducting electrode substrate and by thermal oxidation of titanium metal. The thin films were used to study the photoelectrocatalytic or photoelectrochemical degradation of oxalic acid and 4-chlorophenol (4-CP) under near UV (monochromatic, 365 nm) light irradiation. Degradation was monitored by a variety of methods. In the course of oxalic acid degradation, CO(2) formation accounted for up to 100% of the total organic carbon degradation for medium starting concentrations; for the degradation of 4-CP, less CO(2) was detected due to the higher number of oxidation steps, i.e. intermediates. Incident-photon-to-current conversion efficiency, educt degradation and product formation as well as Faradaic efficiencies were calculated for the degradation experiments. Quantum yields and Faradaic efficiencies were found to be strongly dependent on concentration, with maximum values (quantum yield) around 1 for the highest concentrations of oxalic acid.

Heterogeneous photocatalytic oxidation of organics for air purification by near UV irradiated titanium dioxide.

The photocatalytic degradation of high concentrations of various organic pollutants (acetone, 2-propanol and toluene) in dry and humid air streams was carried out using a specially designed photoreactor based on the UV-TiO2 principle. The influence of several parameters which control the destruction efficiency (flow rate, initial contaminant and water vapour concentration, temperature and light intensity) has been studied. The conversion was maximal at room temperature, low flow rates and low initial contaminant concentrations. The presence of water in the inlet stream strongly affected the performance of the catalyst. The primary oxidation product of 2-propanol was acetone.

Photocatalytic oxidation of gaseous chlorinated organics over titanium dioxide

The photocatalytic oxidation of high levels of volatile chlorinated organic compounds in gas phase has been studied using a specially designed photoreactor. The influence of light intensity, initial water vapour concentration, temperature, inlet contaminant concentration and flow rate on destruction efficiency has been investigated. The performance of the titanium catalyst was strongly affected by the presence of water in the air stream. Experiments have been most successfully conducted at room temperature, low initial contaminant concentrations, low flow rates and high light intensities. Several by-products have been detected performing photocatalytic degradation of trichloroethylene (TCE) and tetrachloroethylene (PCE). No catalyst deactivation was observed.

The photo-fenton method : Degradation of nitrogen containing organic compounds

Abstract The combination of Fenton reagent with light — the Photo-Fenton method — represents an efficient method for wastewater treatment. This work is about the degradation of nitrogen containing organic compounds. Monitoring the mineralization of model substances by measuring the total organic carbon as well as detecting the release of nitrogen is described. Under specified conditions the substances could be decomposed and, as expected, aromatic compounds showed a higher degree and rate of degradation than aliphatic ones. Due to strong oxidative conditions organic nitrogen is expected to be released as nitrate, however, in most cases nitrogen was detected mainly as ammonia.