Sergei Preis

Oxidation of aqueous pharmaceuticals by pulsed corona discharge

Oxidation of aromatic compounds of phenolic (paracetamol, β-oestradiol and salicylic acid) and carboxylic (indomethacin and ibuprofen) structure used in pharmaceutics was studied. Aqueous solutions were treated with pulsed corona discharge (PCD) as a means for advanced oxidation. Pulse repetition frequency, delivered energy dose and oxidation media were the main parameters studied for their influence on the process energy efficiency. The PCD treatment appeared to be effective in oxidation of the target compounds: complete degradation of pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media. Low-molecular carboxylic acids were identified as ultimate oxidation by-products formed in the reaction.

Advanced Oxidation Processes Against Phenolic Compounds In Wastewater Treatment

Abstract Experimental research into the oxidative treatment of aqueous solutions and wastewaters containing phenolic compounds was undertaken. Ozone, supported by short wavelength UV-irradiation, hydrogen peroxide and titanium dioxide catalyst, was selected as an oxidant in the following combinations: O3, O3/H2O2, O3/UV, O3/TiO2, O3/UV/H2O2 and O3/UV/TiO2. 5-Methylresorcinol was chosen as a model compound for the experiments with synthetic phenolic solutions. The results obtained from these experiments were compared with the results of oxidative purification of wastewaters produced from the thermal treatment of oil shale in Estonia.

Photocatalytic oxidation of phenolic compounds in wastewater from oil shale treatment

Experimental research into the photooxidation of aqueous solutions and wastewaters containing phenolic compounds was undertaken. Titanium dioxide under near-UV irradiation was selected as a photocatalyst. Phenol, p-cresol, resorcinol and 5-methylresorcinol (5-MR) were chosen as model compounds for the experiments with synthetic phenolic solutions. The photooxidative treatment of phenolic solutions was found to be more effective in acidic and strongly alkaline media. No difference was found between shortwave and near-UV irradiation photooxidation abilities. Methylated phenolic substitutes (p-cresol, 5-MR) yield better to photooxidation than non-methylated compounds. The higher the irradiation intensity the lower the photooxidation efficiency. The results obtained from the experiments with model compounds were compared with the results of photooxidative purification of wastewaters produced from the thermal treatment of oil shale in Estonia. Being heavily polluted, the wastewater yields better to photooxidation when slightly diluted with potable water in a 3:1 ratio. Anatase, immobilised onto the surface of buoyant hollow glass microspheres, was less effective than when suspended in a slurry. The photooxidatively pre-treated wastewater showed better biodegradability and lower toxicity to bacteria than untreated wastewater.

Methodology Of Ozone Introduction Into Water And Wastewater Treatment

Theoretical basis and methodology for calculation and modeling of ozonation processes and contact equipment have been elaborated. Methodology of determination of reaction rate constant, stoichiometric coefficient, optimum values of pH, intermediate and final products, regimes of chemisorption, etc., for certain typical fast and slow reacting organic compounds (aniline, toluidine, humic acids, nitrobenzene, glyoxalic, oxalic and acetic acid) and wastewaters have been proposed. For calculation of the wastewater ozonation process, the value of chemical oxygen demand (COD) was suggested to be as a kinetic parameter from the solution side. On the basis of kinetic information, recommendations for the choice of the construction of contact equipment for the different chemisorption regimes of ozonation have been presented. Some new contact apparatuses have been proposed.

Kinetic Description of Industrial Wastewater Ozonation Processes

Abstract Literary and experimental data on the ozonation kinetics of aqueous solutions and wastewater were analyzed. COD was suggested to be used as a kinetic parameter from the solution side. On the basis of the results obtained from the ozonation of model solutions and wastewater, the rate coefficient by COD of the reaction was shown to be constant during separate stages of the process. Due to the consumption of fast-reacting components and entering into the reaction of more slowly reacting intermediate products, the rate coefficient changed spasmodically with transition from one stage to another. The reaction order with respect to the COD of the solution was shown to be equal to the reaction order with respect to the pure component.

The Cost Evaluation of Advanced Oxidation Processes in Laboratory and Pilot-Scale Experiments

The present level of the development of water/wastewater treatment methods, including advanced oxidation processes, allows removal of pollutants of wide spectrum under no question. However, the overall process cost and, especially, associated energy consumption are of increased importance. The present review presents the energy cost calculations made for the pollutants removal reported in more than forty publications for over the last four decades. Phenol, glycols, methyl-tert-butyl ether (MTBE), aliphatic unsaturated compounds, humic acids and lignin were considered as water pollutants for economic evaluation of their removal. Two oxidation processes, ozonation and Fenton reaction, were chosen as water treatment methods.

Photocatalytic oxidation of aromatic aminocompounds in aqueous solutions and groundwater from abandoned military bases

Experimental research into the photooxidation of aqueous solutions and polluted groundwater containing aromatic aminocompounds was undertaken. For the experiments with synthetic solutions, titanium dioxide under near-UV irradiation was selected as a photocatalyst, and aniline, p-toluidine and 2,4-xylidine were selected as model compounds. The photooxidative treatment of synthetic solutions was found to be more effective in acidic and strongly alkaline media. Methylated aminocompounds (p-toluidine, 2,4-xylidine) yield slightly better to photooxidation than aniline. The results obtained from experiments using model compounds were compared with the results of photooxidative purification of polluted groundwater from an abandoned military base in Estonia. Being heavily polluted, the groundwater yields better to photooxidation when diluted with potable water at a 7:3 ratio. Anatase, immobilised onto the surface of buoyant hollow glass microspheres, was less effective than when suspended in slurry. However, the immobilised photocatalyst enables water to be treated without the expense of constant stirring. This also avoids complications concerned with catalyst separation following treatment. Degussa P25 was more effective than Aldrich anatase both in stirred slurry type reactors and when attached to hollow glass microspheres.

The role of pH in aqueous photocatalytic oxidation of β-estradiol

Experimental studies of aqueous photocatalytic oxidation (PCO) of β-estradiol in TiO2 suspensions were undertaken. The dependence of PCO efficiency and adsorption of β-estradiol on pH was studied. It was found that both the adsorption of β-estradiol and the PCO efficiency increased practically linearly with increasing concentration of OH-ions. The predominant role of direct β-estradiol oxidation with positively charged holes was thus indirectly confirmed.

Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation

Ozone and hydroxyl radical are the most active oxidizing species in water treated with gas-phase pulsed corona discharge (PCD). The ratio of the species dependent on the gas phase composition and treated water contact surface was the objective for the experimental research undertaken for aqueous phenol (fast reaction) and oxalic acid (slow reaction) solutions. The experiments were carried out in the reactor, where aqueous solutions showered between electrodes were treated with 100-ns pulses of 20 kV voltage and 400 A current amplitude. The role of ozone increased with increasing oxygen concentration and the oxidation reaction rate. The PCD treatment showed energy efficiency surpassing that of conventional ozonation.

Oxidation of Aqueous Paracetamol by Pulsed Corona Discharge

Oxidation of paracetamol in aqueous solution was studied by using pulsed corona discharge as a means for advanced oxidation. Pulse repetition frequency, the delivered energy dose, and oxidation media were the main parameters evaluated. The pulsed corona discharge treatment appeared to be effective in oxidation of paracetamol: complete degradation of target pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media, the fastest oxidation rate was observed in oxygen-enriched air. Low-molecular carboxylic acids were identified as the products formed in the reaction.