Photochemical mineralization of amoxicillin medicinal product by means of UV, hydrogen peroxide, titanium dioxide and iron.

In the present study, the photochemical degradation of amoxicillin and total organic carbon (TOC) removal in pharmaceutical aqueous solutions was studied using UV irradiation, titanium dioxide, hydrogen peroxide and iron in a batch photoreactor operated for 120-150 min. The effect of the initial concentrations of the target compound, hydrogen peroxide and ferric ions and of their combination was examined. It was found that under direct UV photolysis, considerable TOC removals were obtained only when the initial concentration of amoxicillin (AM) was below 100 mg/L. For initial concentration of AM 250 mg/L, the TOC removals achieved were of no practical use (below 5%). The TOC removals achieved in the presence of TiO2 were lower than 20% in all cases. In the presence of hydrogen peroxide in the range of 12.2-146.9 mmol/L and initial AM concentration 250 mg/L, for increasing H2O2 concentrations higher TOC removals were achieved up to the concentration of 73.4 mmol/L H2O2. The presence of even very small amounts of Fe(III) in the solution resulted in significantly increased TOC removals; 2.2 times higher than without Fe(III) after 120 min. Fe(III) presence accelerated dramatically the process during the first 60 min. The origin of Fe(III) ions was not important since practically the same results were obtained whether FeCl3 or Fe(NO3)3 was used as source of ferric ions. Adjusting the initial concentrations of AM, Fe(III) and H2O2, TOC removals above 90% were achieved.

Catalytic destruction of gaseous ethanol and product formation over CuO/CeO2/Al2O3 catalysts.

In the present work, the catalytic decomposition or oxidation of ethanol over CuO/CeO(2)/γ-alumina catalysts is presented. Ethanol was oxidized in a tubular flow reactor under both oxygen excess and deficit conditions. Various amounts of ceria (0-14 % w/w) were added by wet impregnation to catalysts containing 1 % and 10 % w/w CuO on γ-Al(2)O(3). Ceria addition affected catalyst performance mostly at low CuO loading and the formation of the main reaction products, namely acetaldehyde and carbon dioxide, depended strongly on oxygen concentration. The formation of the rest reaction products (i.e., ethylene and diethylether) depended on both oxygen concentration and amount of ceria on the catalyst used.

Photocatalytic degradation of methyl tert-butyl ether in the gas-phase: a kinetic study.

Methyl tert-butyl ether (MTBE) is the basic oxygenated motor fuel additive in Europe and is included in volatile organic compounds (VOCs), which can produce photochemical oxidants. In the present study the gas-phase photocatalytic oxidation (PCO) of MTBE over illuminated titanium dioxide was carried out at ambient temperature in a plug flow reactor. The intermediates detected are mainly tert-butyl formate and acetone, while the final products are CO(2) and water. The system was sensitive to the oxygen concentration, for concentrations up to 15% (v/v). Moisture had a positive effect on the reaction, obtaining an optimum value near 45% relative humidity for 200ppmv MTBE initial concentration. A reaction scheme has been proposed for the interpretation of the experimental results and a kinetic study was conducted, using the Langmuir-Hinshelwood kinetics equation. The MTBE rate constant was 1.545 x 10(-6)Ms(-1)g(cat)(-1) for the reaction without moisture and 2.46 x 10(-6)Ms(-1)g(cat)(-1) for the reaction in the presence of moisture and the adsorption constant was 2.187 x 10(5)M(-1) independent of humidity.

Combined photo-assisted and biological treatment of industrial oily wastewater.

In the present study an oily wastewater from the lubricant unit of a petroleum company was evaluated by combining the sequence photo-assisted oxidation-Pseudomonas putida DSM 437. The wastewater contained various alcohols, acids and phenolic compounds. From the above mentioned compounds the biodegradation of ethylene glycol, phenol, o-cresol and p-cresol was examined. The direct biodegradation of the wastewater using P. putida DSM 437 resulted in 85% ethylene glycol assimilation while phenol, o-cresol and p-cresol assimilation was in the range of 27% to 40%. In order to increase the degradation of the phenolic compounds photo-assisted oxidation was applied to the wastewater using UV/ H2O2 its a pretreatment step to biological degradation. Fc(III) were used in order to accelerate the formation of the hydroxyl radicals and consequently the overall photo-oxidation process. The addition of Fe(III) ions resulted in 30% decrease of COD within the first 10 min while the respected value without iron ions was 5%. The combined photo-assisted oxidation and biodegradation of the wastewater resulted in 100% removal of ethylene glycol. The overall degradation of phenol was 78% while the 59% and 84% of the initial o-cresol and p-cresol respectively, were removed from the wastewater. The combined process resulted in 72% of COD removal.

Photocatalytic destruction of methyl tert-butyl ether in the gas phase using titanium dioxide.

The efficiency of the photocatalytic destruction of methyl tert-butyl ether (MTBE) in the gas-phase using UV light and titanium dioxide was studied. TiO2 was coated on the inner side of the photoreactor. Specifically, the effect of residence time (0.17-2.22 min), MTBE concentration (500-5000 ppm), oxygen concentration (0-20,000 ppm) and water vapor on MTBE conversion was examined. Acetone and tert-butyl formate were detected in the photoreactor effluent. The formation of by-products from MTBE decomposition was determined with gas chromatography-mass spectrometry. The residence time affected dramatically the MTBE photo-oxidation as well as by-products existence and configuration. The increase in MTBE concentration at the reactor inlet and the addition of water vapor to the reactants resulted in decreased MTBE conversions. Increasing oxygen concentration up to 10,000 ppm enhanced the photocatalytic process but a further increase to 20,000 ppm had an adverse impact on MTBE decomposition. In all cases, the by-product formation profiles were extremely dependent on photocatalysis parameters studied.

Coagulation for treatment of paint industry wastewater.

In the present study, the coagulation of paint industry wastewater was examined. Ferrous and aluminum sulphate and polyaluminum chloride (PACl) were used as coagulation agents and the influence of the coagulant dose and effective pH on the quality of treated wastewater was investigated. Optimum pH for FeSO4 addition was near 9.7, the required coagulant dose was about 2 g/L and average process efficiency varied between 30 and 80% in COD and between 70 and 99% in turbidity terms, for a wide spectrum of wastewater batches. In the case of Al2(SO4)3, no pH adjustment was needed and process efficiency varied between 70 and 95% in COD and between 90 and 99% in turbidity terms, for an effective dose of 2.5 g/L. Further improvement of process efficiency was possible by raising the pH of the supernatant liquid after alum-sludge sedimentation to 10. In the case of PACl optimum pH was around 7 and process efficiency was about 98% based on both quality parameters, for an effective dose of 4 g/L. Cationic polyelectrolytes were proved to have a higher potential vs. coagulation than anionic ones when acting as primary coagulants. Combination of Al2(SO4)3 or PACl with polyelectrolytes resulted in high process efficiencies, while maintaining liquid pH values at acceptable limits.