Photochemistry of the Cloud Aqueous Phase: A Review

This review paper describes briefly the cloud aqueous phase composition and deeply its reactivity in the dark and mainly under solar radiation. The role of the main oxidants (hydrogen peroxide, nitrate radical, and hydroxyl radical) is presented with a focus on the hydroxyl radical, which drives the oxidation capacity during the day. Its sources in the aqueous phase, mainly through photochemical mechanisms with H2O2, iron complexes, or nitrate/nitrite ions, are presented in detail. The formation rate of hydroxyl radical and its steady state concentration evaluated by different authors are listed and compared. Finally, a paragraph is also dedicated to the sinks and the reactivity of the HO• radical with the main compounds found in the cloud aqueous phase. This review presents an assessment of the reactivity in the cloud aqueous phase and shows the significant potential impact that this medium can have on the chemistry of the atmosphere and more generally on the climate

Photochemistry of the Cloud Aqueous Phase: A Review

This review paper describes briefly the cloud aqueous phase composition and deeply its reactivity in the dark and mainly under solar radiation. The role of the main oxidants (hydrogen peroxide, nitrate radical, and hydroxyl radical) is presented with a focus on the hydroxyl radical, which drives the oxidation capacity during the day. Its sources in the aqueous phase, mainly through photochemical mechanisms with H2O2, iron complexes, or nitrate/nitrite ions, are presented in detail. The formation rate of hydroxyl radical and its steady state concentration evaluated by different authors are listed and compared. Finally, a paragraph is also dedicated to the sinks and the reactivity of the HO• radical with the main compounds found in the cloud aqueous phase. This review presents an assessment of the reactivity in the cloud aqueous phase and shows the significant potential impact that this medium can have on the chemistry of the atmosphere and more generally on the climate

Photo-Activation of Persulfate and Hydrogen Peroxide by Humic Acid Coated Magnetic Particles for Bisphenol A Degradation

Abstract Magnetic particles (MPs) coated with humic acid (HA) prepared under anoxic atmosphere were tested as heterogeneous photo-Fenton catalyst for the activation of hydrogen peroxide (H2O2) and persulfate (S2O82-) using Bisphenol A (BPA) as a model pollutant. The role of HA coating, pH value and H2O2/S2O82- concentration were investigated. A positive contribution of HA coating on H2O2 and S2O82- activation was found. The highest BPA degradation rates were achieved at acidic conditions (pH 3) with both H2O2 and S2O82-, however persulfate showed a significant efficiency even at pH 6, interesting feature in the light of decreasing the wastewater treatment costs. By the addition of selective quenching agents, •OH and SO4•– were identified as the main reactive species involved in the BPA abatement. An important contribution of the S2O82- photolysis on the overall BPA transformation was highlighted. The reuse of the catalyst was investigated and similar efficiency using H2O2 and S2O82- activation was observed until the third catalytic cycle. Experiments carried out using real wastewater samples, showed a good, even if less efficient compared to pure water, BPA removal

Assessing the photodegradation potential of compounds derived from the photoinduced weathering of polystyrene in water

Peer reviewe

Formation of Toxic Unsaturated Multifunctional and Organosulfur Compounds From the Photosensitized Processing of Fluorene and DMSO at the Air-Water Interface

Polycyclic aromatic hydrocarbons and dimethyl sulfoxide (DMSO) are ubiquitous at the sea surface. Photochemistry at the air-sea interface is a potentially important source of volatile organic compounds, but the relevant chemical processes are currently not well known. When aqueous solutions containing a mixture of fluorene (FL) and DMSO are irradiated with actinic radiation, a large suite of unsaturated high molecular weight compounds appear in the aqueous phase; a broad variety of saturated and unsaturated oxygenated multifunctional compounds are also observed in the gas phase, most of which are more toxic than FL. A possible sequence of steps leading to some of the observed compounds in aqueous solution as well as in the gas phase is proposed. The reaction pathways initiated by excited triplet state of FL (3FL*) are supported by theoretical calculations of the reaction Gibbs energies. The formation of organosulfur compounds has been observed to occur in the gas and the aqueous phases initiated by the reaction between 3FL* and DMSO. The aforementioned photosensitized chemistry at the water surface can have an important impact on the formation of secondary organic aerosol in marine boundary layer as polycyclic aromatic hydrocarbons and DMSO enriched at the water surface are ubiquitous. ©2020. American Geophysical Union. All Rights Reserved

Anodic TiO2 nanotube layers for wastewater and air treatments: Assessment of performance using sulfamethoxazole degradation and N2O reduction

The preparation of anodic TiO2 nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO2 thin layer has been also prepared using the sol-gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N2O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO2 nanotube layers have exhibited the highest N2O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO2 nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h.Web of Science2724art. no. 895