Anna Moiseev

Treatment of Phenolic and Aromatic Amino Compounds in Polluted Waters by Photocatalytical Oxidation

Abstract Improper handling of rocket fuel residues at abandoned military bases has resulted in heavy pollution of the soil and groundwater with aromatic amino compounds. A similar phenomenon is observed with ash dumps in which solid waste from oil shale thermal treatment is disposed: the ash dump leachate is heavily polluted with phenolic and other compounds, resistant to biological treatment. Experimental research of photocatalytical oxidation (PCO) of both classes of substances and polluted waters was undertaken. The influence of different parameters - pH, concentration of substances to be oxidised, character of substances formed during the PCO, presence of inorganic admixtures, effect of OH•-radical generators and scavengers - on the PCO of solutions of phenolic and aromatic amino compounds was determined. The role of OH•-radicals was found to be important in determining both the PCO rate and the character of the oxidation by-products. The PCO of organic pollutants was also investigated using a catalyst immobilised onto the surface of buoyant hollow glass micro-spheres. Attached titanium dioxide showed lower photocatalytical activity than its slurry, although it allows waters to be treated in simple shallow ponds without intensive stirring. The toxicity of aqueous solutions and polluted waters decreased as PCO proceeded and the biodegradability increased. The energy consumed by PCO of phenolic compounds in phenolic wastewater under solar radiation was estimated to be smaller than the energy consumed by oxidation with ozone.

Aqueous Photocatalytic Oxidation of Doxycycline

Abstract The experimental research into the aqueous photocatalytic oxidation of doxycycline, a tetracycline family antibiotic, was undertaken. The objective of the study was to ensure the feasibility of doxycycline photocatalytic degradation by UVA irradiated titania coatings on granulated media to be used in fluidised bed photocatalytic reactor and by slurries of P25, Evonik, as well as by visible light-sensitive sol-gel synthesized carbon-containing titania. The parameters influencing doxycycline oxidation, like catalyst concentration, initial doxycycline concentration and pH with P25 TiO2 were studied. The impact of calcination temperature on the catalytic properties of carboncontaining titania and catalytic activity of titania film on expanded clay as bed material towards doxycycline degradation were also studied. Based on the examination of doxycycline photocatalytic oxidation by-products, possible doxycycline degradation pathways were proposed.

Elimination of persistent emerging micropollutants in a suspended-bed photocatalytic reactor: influence of operating conditions and combination with aerobic biological treatment.

A larger, lab-scale photocatalytic suspended-bed reactor using TiO2 sol-gel-coated expanded clay granules as a bed material was evaluated for oxidative removal of the persistent pharmaceuticals doxycycline, prednisolone, amoxicillin, and sulfamethizole, as well as their mixture, in ppm concentrations. The photocatalytic degradation potential of drug molecules increases as their adsorption affinity increases towards TiO2-containing coatings. The performance of the photocatalytic reactor in the removal of drugs was improved by optimizing the fluidization process parameters. The reactor operation at high bed loadings is determined by the abrasion resistance of the catalyst coating. The long-term stability of the coated bed was enhanced by optimal loading, achieving a higher removal rate while placing moderate mechanical stress on the coated granules. The photocatalytic pretreatment decreased the toxicity of doxycycline solutions to several bacterial strains, including the environmental bacterium Pseudomonas putida and bacterial strains freshly isolated from the activated sludge. The treatment of doxycycline-containing water with a combination of photocatalytic treatment and bio-oxidation resulted in 98% removal of the target in the bioreactor outlet, with no deterioration in the operation of the biological process.