Aqueous photocatalytic oxidation of lignin and humic acids with supported TiO

The photocatalytic oxidation (PCO) of UV-irradiated aqueous solutions containing humic acids and lignin was studied. The photocatalyst TiO2 was attached to buoyant hollow glass microspheres and glass plates. A maximum oxidation efficiency as low as 1.1 and 2.54 mg W−1h−1 for humic acids and lignin, respectively, was achieved in neutral and alkaline media with 25 gm−2 of the buoyant catalyst. In acidic media, efficiency was even lower. The photocatalytic efficiency with the photocatalyst attached to glass plates was about 3 to 4 times higher than that for the buoyant catalyst. Ferrous ions added to acidic solutions did not increase the rate of PCO of humic acids. However the addition of Fe2+ ions, up to 0.05 mM, to the lignin solution leads to a dramatic increase, about 25%, in PCO efficiency. A further increase in ferrous ion concentration results in a decrease in the PCO efficiency of lignin. Proceeding most likely by a radical mechanism, the efficiency of PCO of humic acids did not benefit from an excessive presence of hydroxyl radical promoters, such as hydrogen peroxide, although the reaction rate increased. However, PCO of lignin in the acidic medium, where OH.-radical formation is suppressed, benefited from the introduction of hydrogen peroxide due to promoted radical formation

Oxidation of Aqueous Naproxen Using Gas-Phase Pulsed Corona Discharge: Impact of Operation Parameters

Naproxen is a widely used non-steroidal anti-inflammatory drug poorly metabolized in the human body, thus resulting in its presence in domestic wastewaters. It is resistant to conventional wastewater treatment, making new methods necessary. Pulsed corona discharge, an energy-efficient advanced oxidation process, was experimentally studied for the oxidation of naproxen in various operation conditions, showing high energy efficiencies in a wide span of pH levels, concentrations, and pulse repetition frequencies. Surfactants present in treated solutions appeared to enhance the degradation rate. The research results contribute to the knowledge of the method’s chemistry and technology, supporting its full-scale implementation

Gas-Phase Photocatalytic Oxidation of Dimethylamine: The Reaction Pathway and Kinetics

Gas-phase photocatalytic oxidation (PCO) and thermal catalytic oxidation (TCO) of dimethylamine (DMA) on titanium dioxide was studied in a continuous flow simple tubular reactor. Volatile PCO products of DMA included ammonia, formamide, carbon dioxide, and water. Ammonia was further oxidized in minor amounts to nitrous oxide and nitrogen dioxide. Effective at 573 K, TCO resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The PCO kinetic data fit well to the monomolecular Langmuir-Hinshelwood model, whereas TCO kinetic behaviour matched the first-order process. No deactivation of the photocatalyst during the multiple long-run experiments was observed

Oxidation of Aqueous Naproxen Using Gas-Phase Pulsed Corona Discharge: Impact of Operation Parameters

Naproxen is a widely used non-steroidal anti-inflammatory drug poorly metabolized in the human body, thus resulting in its presence in domestic wastewaters. It is resistant to conventional wastewater treatment, making new methods necessary. Pulsed corona discharge, an energy-efficient advanced oxidation process, was experimentally studied for the oxidation of naproxen in various operation conditions, showing high energy efficiencies in a wide span of pH levels, concentrations, and pulse repetition frequencies. Surfactants present in treated solutions appeared to enhance the degradation rate. The research results contribute to the knowledge of the method’s chemistry and technology, supporting its full-scale implementation

Selective Photocatalytic Oxidation of Steroid Estrogens in the Presence of Copollutants in the Sanitary Fraction of Domestic Sewage

The photocatalytic oxidation (PCO) of the steroid estrogens (SEs), β-estradiol, and 17α-ethynylestradiol, competitive with some constituent compounds of the sanitary fraction of domestic sewage, was studied. The copollutants, urea, and saccharose, present in concentrations exceeding those of the SEs by a factor of a hundred to thousands, appeared to exert a weaker influence to the photocatalytic degradation of the SEs than was expected. The removal of the SEs from diluted urine proceeded, selectively, demonstrating the potential of PCO in the treatment of the separate sanitary fraction of domestic sewage

Degradation of Antibiotic Vancomycin by UV Photolysis and Pulsed Corona Discharge Combined with Extrinsic Oxidants

Antibiotics are the most frequently detected pharmaceuticals in the environment creating conditions for the development of resistant genes in bacteria. Degradation and mineralization of glycopeptide antibiotic vancomycin (VMN) were examined by UV photolysis, pulsed corona discharge (PCD), and their combinations with extrinsic oxidants, hydrogen peroxide (HP), peroxydisulfate (PDS), and peroxymonosulfate (PMS). Both combinations were effective in VMN degradation and faster at pH 11 than in acidic or neutral media. Combined with the UV photolysis, HP showed a higher oxidation rate than other oxidants, whereas PMS and PDS proved to be more efficient in combinations with PCD. In contrast to low-to-moderate mineralization of VMN in the UV/oxidant combinations, PCD and PCD/oxidant combinations appeared to be more effective, reaching up to 90% of TOC removal in acidic/neutral solutions. Application of extrinsic oxidants resulted in an energy efficiency of VMN 90% oxidation improved from 36 to 61 g kW−1 h−1 in HP-assisted photolysis, and from 195 to 250 g kW−1 h−1 in PCD with additions of HP and PDS, thus showing the promising character of the combined treatment.peerReviewe

Oxidation of Aqueous Toluene by Gas-Phase Pulsed Corona Discharge in Air-Water Mixtures Followed by Photocatalytic Exhaust Air Cleaning

The treatment of wastewaters containing hazardous volatile organic compounds (VOCs) requires the simultaneous treatment of both water and air. Refractory toluene, extensively studied for its removal, provides a basis for the comparison of its abatement methods. The oxidation of aqueous toluene by gas-phase pulsed corona discharge (PCD) in combination with the subsequent photocatalytic treatment of exhaust air was studied. The PCD treatment showed unequalled energy efficiencies in aqueous and gaseous toluene oxidation, reaching, respectively, up to 10.5 and 29.6 g·kW−1·h−1. The PCD exhaust air contained toluene residues and ozone in concentrations not exceeding 0.1 and 0.6 mg·L−1, respectively. As a result of the subsequent photocatalytic treatment, both airborne residues were eliminated within a contact time with TiO2 as short as 12 s. The results contribute to the possible application of the studied approach in closed-loop energy-saving ventilation systems