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Abstract In the present study we investigate the photochemical properties and impact on cloud water of ferric-aspartate complex (Fe(III)−Asp) under irradiation. Fe(III)−Asp complex was investigated as proxy of ferric-amino acids complexes that could be expected to be present in cloud water. First, the fate of complex under monochromatic (313 and 365 nm) and polychromatic (λ ≥ 290 nm) irradiation is investigated and formation quantum yields of Fe2+ are determined. Moreover, hydroxyl radical quantification in the presence of hydrogen peroxide is investigated at cloud water relevant concentrations and under irradiation. Obtained results suggest that hydroxyl radical formation rates are expected to be lower than those obtained considering all iron as aquacomplex or complexed with oxalate. Finally, a phototransformation mechanism for inorganic and organic products formation such as ammonia, malonic, oxalic and formic acids is proposed. Highlights • Fe(III)-amino acid complexes can be generated in cloud waters. • A photochemical pathway in the presence of hydrogen peroxide can lead to the formation of hydroxyl radical. • Fe(III)-amino acids complexes photochemistry is a source of ammonia and short-chain carboxylic acids. [ABSTRACT FROM AUTHOR]

The adsorption and photocatalytic degradation abilities of bismuth catalyst (BiOCl 0.75 I 0.25 ) in water are tested under simulated solar light by using p -hydroxyphenylacetic acid ( p -HPA) as chemical pollutant. On the basis of the strong adsorption of p -HPA on the catalyst surface, this work aims to investigate the interfacial mechanism in the heterogeneous system through adsorption/desorption experiments by using competitive-anion desorption with phosphate anions. The key factors affecting the degradation kinetics of p -HPA such as pH and dissolved oxygen concentration are investigated. We find that solution pH significantly affects the adsorption and degradation rates depending on the zeta potential of catalyst and molecular form of p -HPA. p -HPA shows maximum adsorption at pH 4.5 and faster degradation rate at pH 3.0. Dissolved oxygen concentration is a key factor affecting pollutant removal because of the formation of hydroperoxide/superoxide radical anion couple (HO 2 /O 2 − ). These radicals, which are the main reactive species involved in the reaction after irradiation of catalyst, are detected using competition-kinetics approach and selective radical probes. [ABSTRACT FROM AUTHOR]

The processes of Fe(III) activated persulfate (PS) and H 2 O 2 modified by catechin (CAT) had been shown to be effective in degrading contaminants. In this study, the performance, mechanism, degradation pathways and products toxicity of PS (Fe(III)/PS/CAT) and H 2 O 2 (Fe(III)/H 2 O 2 /CAT) systems were compared using atenolol (ATL) as a model contaminant. 91.0% of ATL degradation was reached after 60 min in H 2 O 2 system which was much higher than that in PS system (52.4%) under the same experimental condition. CAT could react directly with H 2 O 2 to produce small amounts of HO• and the degradation efficiency of ATL was proportional to CAT concentration in H 2 O 2 system. However, the optimal CAT concentration was 5 μM in PS system. The performance of H 2 O 2 system was more susceptible to pH than that of PS system. Quenching experiments were conducted indicating that SO 4 •- and HO• were produced in PS system while HO• and O 2 •- accounted for ATL degradation in H 2 O 2 system. Seven pathways with nine byproducts and eight pathways with twelve byproducts were put forward in PS and H 2 O 2 systems respectively. Toxicity experiments showed that the inhibition rates of luminescent bacteria were both decreased about 25% after 60 min reaction in two systems. Although the software simulation result showed few intermediate products of both systems were More toxic than ATL, but the amounts of them were 1–2 orders of magnitude lower than ATL. Moreover, the mineralization rates were 16.4% and 19.0% in PS and H 2 O 2 systems respectively. [Display omitted] • Comparative studies were done in Fe(III)/H 2 O 2 /CAT and Fe(III)/PS/CAT system. • The performance of ATL degradation was efficient in Fe(III)/H 2 O 2 /CAT system. • The ATL degradation rates were slightly affected by pH in Fe(III)/PS/CAT system. • Degradation pathways of ATL in two systems were proposed and compared. • Several byproducts showed less toxicity in two systems. [ABSTRACT FROM AUTHOR]

There is increasing evidence that aqueous-phase atmospheric chemistry is an important source of secondary organic aerosols (SOA), but the related processes are currently not adequately represented in atmospheric chemistry models. Here we show that the absorption spectrum of pyruvic acid (PA) exhibits both an increase of the absorption intensity and a red shift of 13 nm while going from a dilute aqueous phase to a solution containing the inert salt sodium perchlorate (5M NaClO 4 ). If this phenomenon turns out to be more general, many compounds that do not absorb actinic light in clouds and fog could become light absorbers at elevated salt concentrations in aerosol deliquescent particles. Compared to the direct photolysis of PA in dilute aqueous solution, the photolysis rate is increased by three times at high ionic strength (5M NaClO 4 ). Such a considerable enhancement can be rationalized in the framework of the Debye-McAulay approach for reactions of ionic + neutral (or neutral + neutral) species, considering that the PA direct photolysis likely involves interaction between the photogenerated triplet state and water. This is, to our knowledge, the first report of a significant effect of the ionic strength on the rate of an atmospheric photochemical reaction. The phenomenon has important implications for the fate of PA and, potentially, of other organic compounds in atmospheric aerosol deliquescent particles. [ABSTRACT FROM AUTHOR]

The singlet and triplet excited states of 4-hydroxybenzophenone (4BPOH) undergo deprotonation in the presence of water to produce the anionic ground-state, causing fluorescence quenching and photoactivity inhibition. The same process does not take place in an aprotic solvent such as acetonitrile. In acetonitrile, 4BPOH is fluorescent (interestingly, one of its fluorescence peaks overlaps with peak C of humic substances), it yields singlet oxygen upon irradiation and induces the triplet-sensitised transformation of phenol (with a rate constant of (6.6 ± 0.3) × 107 M−1 s−1 (μ±σ) between phenol itself and a triplet 4BPOH). The 4BPOH shows an intermediate behaviour in a partially protic solvent such as 2-propanol, where some deprotonation of the excited states is observed. In acetonitrile/2-propanol mixtures (at least up to 50% of 2-propanol) there is also some evidence of alcohol oxidation by the 4BPOH triplet state, while the experimental data are silent concerning such a possibility in pure 2-propanol. Considering that benzophenones are important components of chromophoric dissolved organic matter (CDOM) in surface waters, the present findings could have significance for the photoactivity of the hydrophilic surface layers vs. the hydrophobic cores of CDOM. [ABSTRACT FROM AUTHOR]

This paper outlines the synthesis and application of a sustainable composite for the photo-Fenton-like degradation of caffeine, bisphenol A, and simazine. The phase, morphology, optical and magnetic properties of the samples were evaluated by different characterization techniques. The composite of Fe 2.5 Co 0.3 Zn 0.2 O 4 and copper-chromium layered double hydroxide (CuCr-LDH) was determined to be the most favorable photocatalyst in the photo-Fenton-like process when compared with Fe 3 O 4 , Fe 2.5 Co 0.3 Zn 0.2 O 4 , CuCr-LDH, and Fe 3 O 4 /CuCr-LDH composite. Studying the efficiency of the photo-Fenton-like degradation process in the presence of the Fe 2.5 Co 0.3 Zn 0.2 O 4 /CuCr-LDH composite revealed a degradation rate constant of caffeine twice more than the sum of those obtained for the individual processes. This ascribes to the synergistic effect by which the photo-generated electron-hole from the catalyst and the efficient reduction of Fe3+, Cu2+, etc. during the photo-Fenton-like reaction is accelerated. Moreover, under the optimal condition and after 120 min of heterogenous photo-Fenton-like process at natural pH, > 90% of pollutants mixture was decomposed. The experiments fulfilled in near-real conditions demonstrated I) the high stability and magnetically recoverability of the photocatalyst and II) the proper degradation performance of the applied heterogenous photo-Fenton-process in the removal of pollutant mixture in different water bodies and in the presence of chloride and bicarbonate ions. [Display omitted] • Co 0.3 Zn 0.2 Fe 2.5 O 4 /CuCr-LDH composite as sustainable photocatalyst was synthesized. • Photo-Fenton-like process showed a synergetic effect in degradation of pollutants. • Under the optimal condition almost 90% of pollutants mixture was degraded. • 68% of TOC removal was observed for the pollutants mixture after 4 h of process. • Different water types and available inorganic ions showed a low inhibiting effect. [ABSTRACT FROM AUTHOR]

In this work, the photo reactivity of ferric oxalate (Fe(III)-Ox) complex in atmospheric particles was investigated. Raman spectroscopy was used to explore the mechanism and kinetics of Fe(III)-Ox photolysis occurring at the aqueous/gas interface, inside the droplet and in bulk solution. Ferrous carbonate (FeCO 3) was detected indicating that carbonate ion (CO 3 2−) formed inside the droplets would compete with oxalate ligands for iron complexation. A higher concentration of photoproduct Fe(II)-Ox was observed at the surface and inside of the droplets than in bulk solution. In particular, Fe(III)-Ox on the droplet surface was quickly reduced with light and Fe(II)-Ox concentration gradually decreased with irradiation time. The evolution of Fe(II)-Ox concentration was similar inside the droplet and in bulk solution with a trend of first increasing and then gradually decreasing during irradiation time. Although FeCO 3 would hinder Fenton intermediate reaction, the photolysis rate of Fe(III)-Ox in droplets was almost two orders of magnitude times faster than that observed during bulk experiment. In general, the photolysis mechanism and kinetics of Fe(III)-Ox in aqueous/air interface, inside of droplet and bulk solution were distinct, and the production of oxide species from the atmospheric Fe(III)-Ox droplets was underestimated. The reaction mechanism diagram in the Fe(III)-Ox droplet. [Display omitted] • The photolysis rate of ferric oxalate for a droplet was approximately 100 times that in bulk solution. • Fast and intense photoreduction of ferric oxalate occurs at the aqueous/air interface of droplet. • For the first time, the formation of FeCO 3 in atmospheric droplets was reported. [ABSTRACT FROM AUTHOR]

Highlights: [•] The loss of NO2 on solid Polycyclic Aromatic Hydrocarbon (PAH) films was studied. [•] No dependence was observed either with temperature, or with relative humidity. [•] In the dark, the reaction was slow but was greatly enhanced by light. [•] Products (HONO) were identified. [ABSTRACT FROM AUTHOR]

Thepresent work describes in detail the chemical structure ofthe complex Fe(III)–EDDS and the predominance of differentspecies with respect to pH. These results were obtained with ab initiocalculations. From the photoredox process, the formation of hydroxylradical was confirmed, and HO•is the main speciesresponsible for the degradation of the organic compound present inaqueous solution. The degradation of 4-tert-butylphenol(4-t-BP), used as a model pollutant, was investigatedin different conditions. For the first time, the second-order rateconstant of the reaction between HO•and 4-t-BP and the formation rate of HO•(RHO•f) from the photochemical process were evaluated. Through thedegradation of 4-t-BP, the effect of Fe(III)–EDDSconcentration, oxygen, and pH was also investigated. The pH, whichplays a role in the iron cycle and in the Fe(III)–EDDS speciation,was noticed as an important parameter for the efficiency of 4-t-BP degradation. Such a result could be explained by takinginto account the complex speciation and presence of a predominantform (FeL–) up to pH 8. These results are very usefulfor the use and optimization of such iron complexes in water treatmentprocesses. [ABSTRACT FROM AUTHOR]

Highlights: [•] The transient is formed upon Cl− oxidation by 3CDOM* and scavenged by DOM. [•] Typical steady-state [ ] would be around 10−12–10−13 M in sunlit waters. [•] The above results are compatible with phenol photochlorination data in seawater. [•] The species would be a major oxidant of nitrite to the nitrating agent NO2. [•] This could explain elevated nitrophenol photogeneration in brackish and seawater. [ABSTRACT FROM AUTHOR]

The present work describes, for the first time, the use of a new and strong complexing agent, ethylenediamine-N,N'-disuccinic acid (EDDS) in the homogeneous Fenton process. The effect of H2O2 concentration, Fe(III)-EDDS concentration, pH value, and oxygen concentration on the homogeneous Fenton degradation of bisphenol A (BPA) used as a model pollutant, was investigated. Surprisingly, the performance of BPA oxidation in an EDDS-driven Fenton reaction was found to be much higher at near neutral or basic pH than at acidic pH. Inhibition and probe studies were conducted to ascertain the role of several radicals (e.g., •OH, HO2•/O2•-) on BPA degradation. This unexpected effect of pH on Fenton reaction efficiency could be due to the formation of HO2• or O2•- radicals and to the presence of different forms of the complex Fe(III)-EDDS as a function of pH. Indeed, the reduction of Fe(III)-EDDS to Fe(II)-EDDS is a crucial step that governs the formation of hydroxyl radical, mainly responsible for BPA degradation. In addition to its ability to maintain iron in soluble form, EDDS acts as a superoxide radical-promoting agent, enhancing the generation of Fe(II) (the rate limiting step) and therefore the production of •OH radicals. These results are very promising because they offer an important new treatment option at higher range of pH values and more particularly at pHs encountered in natural conditions. [ABSTRACT FROM AUTHOR]

Abstract: We report for the first time the use of Fe(III)-EDDS (EDDS: ethylenediamine-N,N′-disuccinic acid) complex as an iron source in a homogeneous photo-Fenton system. The performance of this system was followed through the formation of the e degradation of 2,2-bis-(4-hydroxyphenyl)propane (BPA). It was observed that Fe(III)-EDDS can enhance the efficiency of both ion and BPA degradation especially near neutral pH. The effect of H2O2 concentration, Fe(III)-EDDS concentration, pH value and oxygen concentration on the BPA degradation during this photo-Fenton system was investigated. It was observed that O2 is an important parameter affecting the efficiency of this process not only due to its reactivity with BPA but also because of its effect on the iron species present in solution. Comparison with iron complexes of oxalate, citrate and EDTA have demonstrated that Fe(III)-EDDS is a very efficient iron source for this photo-Fenton process. This work also demonstrates that Fe(III)-EDDS plays a positive role in the photo-Fenton system, especially at higher pHs, and makes this system an encouraging method for the treatment of organic pollutants in the natural environment. [Copyright &y& Elsevier]

In the present study, we investigated the correlation between the hydroxyl radical formation rate (R˙OH) and the degradation of a pesticide (mesotrione) in synthetic cloud water solutions and in two real atmospheric cloud waters collected at the top of puy de Dôme station (France). Using terephthalic acid as the hydroxyl radical chemical probe, we established the linear correlation between the photogenerated hydroxyl radical under polychromatic wavelengths and the pesticide degradation rate: ( m s−1) = (1.61 ± 0.15) × 10−1 R˙OH( m s−1). Moreover, the formation rate of hydroxyl radical in two natural cloud waters was estimated considering H2O2 and NO3− and the difference between the predicted values and those experimentally obtained could be attributed to the presence of other photochemical sources: iron-complexes and total organic matter. The organic constituents could play a dual role of sources and scavengers of photoformed hydroxyl radicals in the aqueous phase. [ABSTRACT FROM AUTHOR]

In the present study, we investigated the performance and selectivity of terephthalic acid (TA) as a trapping molecule for the laboratory quantification of photogenerated ·OH in synthetic water (where the organic and inorganic concentration is perfectly controlled), adopted as a proxy of natural atmospheric water (i.e. cloud droplets). TA reacts with OH to yield 2-hydroxyterephthalic acid (TAOH). First, we focused our investigation on the reactivity of TA as a function of pH and temperature of laboratory-made solutions, by using nitrate and hydrogen peroxide as photochemical ·OH sources. For the pH dependence of the TAOH formation yield (YTAOH), by fitting data using linear regression we obtained the relationship YTAOH=(0.0248±0.0059)pH+(0.046±0.035) at T=288K, in the pH range 3.9–7.5. For the temperature dependence we got YTAOH=(0.0059±0.0011)T−(1.50±0.31), between 278 and 303K at pH 5.4. Furthermore, the performance and selectivity of TA were assessed in the presence of different photochemical ·OH sources (nitrate and H2O2) and scavengers (alcohols and carboxylic acids) at variable concentrations. These species are naturally present in the atmospheric aqueous phase. From these experiments we obtained the second-order reaction rate constant between TA and ·OH, kTA,·OH=(4.0±0.1)×109M−1s−1 in aerated solution, at pH 6.0 and 293±2K. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory studies on the heterogeneous conversion of nitrogen dioxide into nitrous acid on irradiated ice films containing humic acid are described. It was found that the presence of light in the visible range of the solar spectrum significantly enhances the rate of nitrous acid release from a humic acid doped ice film. This process might contribute to observed HONO production in snow, where the NO2 is thought to originate from nitrate photolysis. Analysis of the experimental data based on the Langmuir Hinshelwood model framework allowed quantification of the observed dependencies of the nitrous acid production rate on nitrogen dioxide concentration. The observed dependencies on the humic acid concentration as well as on the irradiation intensity were used to estimate light-driven HONO fluxes for environmental snow covers. [ABSTRACT FROM AUTHOR]

By means of a wetted-wall flow tube, we studied the multiphase chemistry of ozone on aqueous solutions containing fulvic acids (FA), taken as proxies for atmospheric "humic like substances", so-called HULIS. In these experiments, the loss of gaseous O3 was monitored by UV-visible absorption spectroscopy at the reactor outlet (i.e., after contact between the gaseous and liquid phases). Measurements are reported in terms of dimensionless uptake coefficients (γ) in the range from 1.6 × 1011 to 1.3 × 1011 depending on ozone gas phase concentration (in the range from 6.6 to 34.4 × 1011 molecules cm-3) and fulvic acid aqueous concentration (in the range from 0.25 to 2.5 mg L-1) and pH (in the range from 2.5 to 9.2). The measured kinetics were observed to follow a Langmuir-Hinshelwood type mechanism, in which O3 first adsorbs on the liquid surface and then reacts with the Fulvic Acid molecules. The reported uptake coefficients are greatly increased over those measured on pure water, demonstrating that the presence in solution of fulvic acids does greatly. enhance the uptake kinetics. Accordingly, the chemical interactions of fulvic acids (or HULIS) may be a driving force for the uptake of ozone on liquid organic aerosols and can also represent an important mechanism for the O3 deposition to the rivers and lakes. [ABSTRACT FROM AUTHOR]

[Display omitted] • S-scheme magnetite@copper-chromium- layered double hydroxide was synthesized. • SO 4 − and OH were produced by the highly active photocatalyst and PMS. • The catalyst preserved its stability after 5 cycles of the degradation process. • 70% of phthalate was degraded by the Vis-light/Composite/PMS process. • The S-scheme mechanism was proposed for the enhanced activity of photocatalyst. Herein, a stable and S-scheme Fe 3 O 4 @CuCr-LDH nanocomposite was synthesized and used for the photocatalytic degradation of diethyl phthalate (DEP) through the activation of peroxymonosulfate (PMS). In comparison with pure Fe 3 O 4, and LDH, the Fe 3 O 4 @CuCr-LDH nanocomposite demonstrated significantly enhanced photocatalytic activity due to its S-scheme charge-carrier migration mechanism. The prepared composite was also magnetically recoverable from the treated water which is favorable to avoid the production of secondary pollution. The integration of the composite and visible light showed the presence of a synergy factor of 14 for the degradation of diethyl phthalate. However, the photocatalytic performance of Fe 3 O 4 @CuCr-LDH was dependent on the different physicochemical parameters; wherein, the higher degradation efficiency was achieved using the solution pH of 8, the catalyst, DEP, and PMS concentrations of 1 g L−1, 20 mg L−1, and 8 mM, respectively. The high photocatalytic activity of the catalyst was maintained after 5 consecutive reaction runs and the stability of the material was proved by the XPS. Moreover, the ICP-AES analysis proved that the leaching of Fe, Cr, and Cu is lower than the standard concentration in the drinking water. Finally, the mineralization ability and the decreased toxicity of the treated solution of DEP were assessed. [ABSTRACT FROM AUTHOR]

Abstract: The effect of positional isomerism on chemical and photochemical degradations of the Imazamethabenz-methyl (IMBM), a pesticide of the imidazolinone family, has been studied. IMBM is proposed in the form of a mixture of the two positional isomers: meta and para. The development of an effective HPLC method (resolution factor R =1.3) allows us to follow either the abiotic disappearance of the meta and para IMBM and the formation of their breakdown products. The abiotic degradation studies include the chemical hydrolysis, as well as the direct and the indirect photodecomposition. We used TiO2, a well-known initiator of hydroxyl radicals, to highlight the role of OH in the indirect photodegradation. This work confirms the different behaviours of positional isomers in the environment. Indeed the chemical or direct photochemical degradation is faster for the meta isomer than for the para. Whereas, concerning IMBM, there is not any prevalent influence of this type of isomerism on the indirect photochemical degradation. The degradation products were tentatively identified by LC-MS, NMR and IR and a degradation pathway was proposed. [Copyright &y& Elsevier]

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO , SO 4 − and HO 2 /O 2 −) are generated through activation of hydrogen peroxide (H 2 O 2), sodium persulfate (Na 2 S 2 O 8) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H 2 O 2 and UVA/Na 2 S 2 O 8 systems whatever the solution's pH. To explain these results, second order reaction rate constant (k radical, ACTP) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO 2 /O 2 − radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na 2 S 2 O 8 exhibits synergistic effects rather than antagonism effects with H 2 O 2. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants. Image 1 • HO , SO 4 − and HO 2 /O 2 − are generated by UVA activation of H 2 O 2 , Na 2 S 2 O 8 and BiOCl. • Heterogeneous photocatalysis with BiOCl shows higher performance than other systems. • Combination of BiOCl and Na 2 S 2 O 8 exhibits synergistic effects on contrary of H 2 O 2. • Steady state concentration of HO 2 /O 2 − is much greater than that of HO and SO 4 −. [ABSTRACT FROM AUTHOR]

The Fe(III)-S(IV) system used for advanced oxidation processes (AOPs) at acidic pH has just been proposed and demonstrated valid for very few contaminants in the last several years. In this work, we investigated the effect of ultraviolet A (UVA) radiation on the degradation efficiency of the Fe(III)/S(IV) system at near-neutral pH. Paracetamol (PARA) was selected as a model contaminant. The influencing factors, such as initial pH and Fe(III)/S(IV) molar ratio on chemical kinetics, and the mechanism of PARA degradation are investigated, with an emphasis on the determination of dominant oxidant species. Our results show that irradiation enhances the PARA degradation by accelerating the decrease of pH to acidic levels, and the optimal pH for the degradation of PARA in the Fe(III)/S(IV)/O2 system was around 4.0. At near-neutral pH, more than 60% of PARA was decomposed within 40 min under irradiation, whereas no significant degradation of PARA was observed using Fe(III)/S(IV) at pH 7.0 without irradiation. Mechanism investigation revealed that sulfate radical (SO4•‒) is the main oxidant species generated and responsible for the PARA degradation under these conditions. This finding may have promising implications in developing a new degradation process for dealing with wastewater at near-neutral pH by the Fe(III)/S(IV)/O2 system under UVA irradiation. [ABSTRACT FROM AUTHOR]

In this work, for the first time, the nonionic surfactant polyoxyethylene-(20)-sorbitan monooleate (Tween 80, C 64 H 124 O 26) aided soil washing effluent was treated by enhanced activation of persulfate (PS) using Fe(III)-EDDS (EDDS: ethylenediamine-N, N-disuccinic acid) complexes under simulated solar light irradiation. The performance of this system was followed via the production and reactivity of radical species (SO 4 -, HO , Cl 2 -) and degradation of phenanthrene (PHE) used as a model pollutant in soils. Different physico-chemical parameters such as the concentration of reactive species and pH were investigated through the PHE degradation efficiency. The second-order rate constants of the reactions for generated radicals with PHE and Tween 80 in solution were identified through competitive reaction experiments under steady-state conditions and application of nanosecond laser flash photolysis (LFP) as well. A kinetic approach was applied to assess the selectivity and reactivity of photo-generated radicals in aqueous medium in order to explain the observed degradation trends. This work proposes an innovative technology of management of soil washing solutions using Fe(III)-EDDS complexes and solar light for the activation of persulfate. • Soil washing effluent is treated by a novel application involving Fe(III) complexes and persulfate. • Primary photo-redox process of Fe(III)-EDDS governs the efficiency of PHE degradation. • The presence of TW80 is the crucial factor governing the degradation of PHE. • The reactivity of radical species on PHE is modified in the presence of TW80. • The presence of chloride ions can significantly improve the PHE removal in this system. [ABSTRACT FROM AUTHOR]

• Photochemical reaction of Fe(III)-EDDS is used to start the AOPs. • Degradation efficiencies using different radical precursors are investigated. • Comparison between hydroxyl and sulfate radical degradation is reported. • A pH effect on the degradation efficiency has been reported. • Photo-Fenton process is much more efficient than the activation of persulfate in natural waters. In the present study, comparison of activation efficiencies of hydrogen peroxide (H 2 O 2) and persulfate (PS, Na 2 S 2 O 8) induced by Fe(III)-Ethylenediamine- N , N' -disuccinic acid (EDDS) under polychromatic irradiation UVA and visible region at same conditions was studied for the first time. The effects of pH, Fe(III)-EDDS concentration, H 2 O 2 and PS concentrations were investigated. p -hydroxyphenylacetic acid (p -HPA) was taken as a model pharmaceutical intermediate pollutant to estimate the oxidative process efficiency. In these two systems, the degradation rate of p -HPA increased (not linearly) using higher concentrated solution of H 2 O 2 and Na 2 S 2 O 8. However, when Fe(III)-EDDS concentration exceeding 250 μM, the degradation efficiency of p -HPA began to decrease. Surprisingly, results of pH effects showed that Fe(III)-EDDS/H 2 O 2 /UV system presents much higher degradation efficiency than Fe(III)-EDDS/PS/UV whatever the solution pH's, especially in neutral and alkaline solutions. In the Fe(III)-EDDS/H 2 O 2 /UV reaction, p -HPA degradation rate (R p -HPA) increased fast from pH 2.5 to 7.5, then it began to decrease when pH increased to 9.0. While R p -HPA started to decrease with pH increase to 3.9 in Fe(III)-EDDS/PS/UV system. To explain this phenomenon, the second order constant of p -HPA (for both molecular and mono-anionic forms) with HO and SO 4 − radicals were determined by laser flash photolysis (LFP) experiments for the first time. Results showed that k p − H P A , H O • was higher than k p − H P A , S O 4 • − for both anionic and molecular forms of pollutant. These results demonstrated that iron-complex induced photo-Fenton process is more efficient than activation of persulfate process, particularly at environmentally closed pH values and sun-simulated wavelengths (λ > 300 nm). [ABSTRACT FROM AUTHOR]

In the present work we investigate the activation efficiency of H 2 O 2 and S 2 O 8 2− using UVA and UVB radiation. Bisphenol-A (BPA) is used as model pollutants to estimate the oxidative process efficiency in simulated and real sewage treatment plant waters. Particular attention is paid to the BPA removal efficiency and to the radical mechanism involvement considering the effect of typical inorganic water constituents (carbonates and chloride ions) and organic matter. Despite a detrimental effect observed when carbonate ions are in solution using both hydrogen peroxide and persulafate, the presence of high chloride ions concentration was found to improve BPA removal using S 2 O 8 2− as radical precursor. This enhancement, investigated combining chemical kinetic model approach and laser flash photolysis experiments, is attributed to the formation of hydroxyl radical and chlorine radical species from sulfate radical. Different transformation products are identified by means of GC–MS and HPLC-MS analyses. Moreover, experiments using sewage treatment plant water (STPW) spiked with BPA are performed in order to assess the efficiency of oxidative processes in a simulated treatment systems activated using UVA + UVB radiations. [ABSTRACT FROM AUTHOR]

Photo-Fenton processes activated by biodegradable Fe(III)–EDDS complexes have attracted huge attention from the scientific community, but the operative mechanism of the photo-activation of H2O2 in the presence of Fe(III)–EDDS has not been fully clarified yet. The application of the Fe(III)–EDDS complex in Fenton and photo-Fenton (mainly under UV-B light) processes, using 4-chlorophenol (4-CP) as a model pollutant was explored to give insights into the operative mechanism. Furthermore, the potential synergistic contribution of soybean peroxidase (SBP) was investigated, since it has been reported that upon irradiation of Fe(III)–EDDS the production of H2O2 can occur. SBP did not boost the 4-CP degradation, suggesting that the possibly produced H2O2 reacts immediately with the Fe(II) ion with a quick kinetics that does not allow the diffusion of H2O2 into the bulk of the solution (i.e., outside the solvent cage of the complex). So, a concerted mechanism in which the photochemically produced H2O2 and Fe(II) react inside the hydration sphere of the Fe(III)–EDDS complex is proposed. [ABSTRACT FROM AUTHOR]

In this study, the activation of persulfate induced by Fe(III) species, including 5 kinds of iron oxhydroxides (IOs) and dissolved Fe 3+ under dark condition were investigated. Ferrihydrite (FH) and akaganeite (AK) showed the highest activity in 4- tert -butylphenol (4tBP) removal. The 4tBP degradation rate constant decreased as the solution pH increased from pH 3.2 to 7.8 in FH/S 2 O 8 2− system. However, the pH value had no significant effect on the 4tBP degradation in AK/S 2 O 8 2− system. The degradation of 4tBP in Fe 3+ /S 2 O 8 2− system was also performed to investigate the role of ferric species in persulfate activation. The pH dependency of 4tBP degradation rate was closely related to the speciation of Fe III , whereas the Fe(H 2 O) 6 3+ was found to be the most active soluble iron complex form in the activation of S 2 O 8 2− . 4tBP degradation was mainly due to the SO 4 − in IOs/S 2 O 8 2− system, while SO 4 − and HO 2 both had great contribution on 4tBP degradation in Fe 3+ /S 2 O 8 2− system. Further investigations showed clearly that 4tBP degradation efficiency was decreased significantly due to the trapping of SO 4 − by chloride. This finding may have promising implications in developing a new technology for the treatment of contaminated waters and soils, especially where Fe 3+ species are naturally occurring. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the present work, the photo-Fenton-like process based on the use of the Fe 2.5 Co 0.3 Zn 0.2 O 4 /CuCr-LDH composite was applied for the removal of green algal cells. First, the biological activity of the composite was proved with the antibacterial tests against the S. aureus ; thereafter, it was used for the removal of Scenedesmus quadricauda algal cells under the photo-Fenton-like process. Interestingly, compared with the individual processes, the photo-Fenton-like process displayed a synergistic effect in the deactivation of green algal cells. The effect of various parameters such as the initial concentration of the algal cells, concentration of the hydrogen peroxide (HP), and the solution pH on the total algal. The maximuml was assessed. Maximum algal removal efficiency was obtained in the presence of the algal cell concentration of 3.5 × 109 cells mL−1, 0.1 g L−1 composite, and HP concentration of 10 mM. Furthermore, the microscopic and SEM images of the algal cells before and after the photo-Fenton-like process proved their appropriate destruction. The reduction of the chlorophyll content after 60 and 120 min of the process was observed revealing the destruction of the algal cell walls. Finally, the disintegration of the macromolecules in the algal cell walls was proved by the GC-MS technique. [Display omitted] • Effective removal of Scenedesmus quadricauda algal cells from contaminated water. • Antibacterial activity of the composite of Fe 2.5 Co 0.3 Zn 0.2 O 4 and CuCr-LDH. • Photo-Fenton-like degradation process showed maximum algal removal efficiency. • Microscopic and SEM images showed effective algal cell destructions. • GC-MS analysis revealed the destruction of algal cell walls to small molecules. [ABSTRACT FROM AUTHOR]

In this study, the activation of persulfate induced by Fe(III)-ethylenediamine-N,N'-disuccinic acid (EDDS) under dark and irradiation conditions and the reactivity of the generated sulfate radical (SO4-) under a wide range of experimental conditions were investigated by means of experimental kinetic analyses and modeling. The Fe(III)-EDDS induced activation of persulfate was found to be efficient across a wide range of pH value (3-7), whereas the second order rate constant of SO4- with 4-tert-butylphenol (4tBP) kSO4-,4tBP = (4.21 ± 0.22) 109 M-1 s-1 was found to be unchanged between pH 2.5 and 8.5. Experimental and theoretical investigations showed clearly that the 4tBP degradation was enhanced in the presence of chloride (10 mM), whereas an almost complete inhibition was observed in the presence of carbonates (10 mM). For the first time, second order rate constants evaluated by laser flash photolysis experiments revealed that SO4- has a similar reactivity with EDDS (6.21 109 M-1 s-1) and 4tBP (4.21 109 M-1 s-1). However, the secondary generated radicals (mainly Cl2-) but also greater amounts of hydroxyl radicals formed in the presence of chloride can likely explain the enhancement of the 4tBP degradation rate. These results may have strong implications for the removal of organic pollutants via sulfate radical generation from contaminated waters, especially if the wastewater possesses carbonate and chloride concentrations consistent with those present in aquatic environments. [ABSTRACT FROM AUTHOR]

Chemical processes in clouds have been suggested to contribute significantly to the mass of organic aerosol particles in the atmosphere. Experimental and theoretical evidence suggest that organic mass production in clouds can be substantial and depends on the concentration of organic precursor compounds available in the gas phase. The present study aims at studying the aqueous phase reactivity of one of these overlooked precursors, i.e. 2,4-hexadienedial, an important and toxic intermediate in the atmospheric oxidation of aromatic species. Cautious synthesis and purification of 2,4-hexadienedial was performed. Its effective Henry's law constant was measured using a new simple and fast method based on online flow-injection analysis. The reactivity of 2,4-hexadienedial in the aqueous phase relevant to atmospheric conditions was studied, including hydrate formation, photolysis, ∙OH- and SO 4 ∙--oxidation as well as reaction with NH 3. The results revealed a low hydration constant compared to other dicarbonyls (K hyd1 = 7 × 10−2) and no dihydrate formation, indicating in an intermediate solubility (K H = 1.0 × 104 M atm−1) and high absorption cross sections (σ 278nm > 10−16 cm2 molecule−1). Compared to its gas phase photolysis, its aqueous phase photolysis showed low quantum yields (Φ 290–380nm = 0.9 %), and a significant red shift of the absorbance maximum, leading to a fast aqueous photolysis kinetics (J aq,atm = 8.7 × 10−5 s−1) under atmospheric solar radiation, but no triplet state formation was detected. Radical oxidation experiments revealed extremely rapid oxidation kinetics (k ∙OH = 1.10 × 1010 M−1 s−1 and k SO4 ∙ - = 1.4 × 109 M−1 s−1) driven by fast addition of the radicals to the unsaturated bonds. In contrast, the reaction with aqueous NH 3 (k NH3 = 2.6 × 10−3 M−1 s−1) was found slower than glyoxal and 2-butenedial, likely due to the hyperconjugation of 2,4-hexadienedial. Using these new data complemented with assumed aqueous phase kinetics (for NO 3 , 3C* and 1O 2 reactions) and previous gas-phase kinetic ones, the multiphase atmospheric fate of 2,4-hexadienedial was established under atmospheric conditions reported from previous field measurements and models. The results revealed a short day lifetime (∼1 h) and a long night lifetime (>12 h). It was shown that daytime atmospheric chemistry of 2,4-hexadienedial can be influenced by aqueous-phase reactivity during cloud events, up to ∼50 % under thick cloud conditions (Liquid Water Content >2000 g/m3), indicating that even a compound of intermediate solubility can be strongly affected by condensed-phase reactivity. Besides its fast aqueous phase reactivity towards ∙OH and photolysis, its daytime condensed-phase reactivity may be driven by reactions with dissolved triplet states (3C*), up to 35 %, highlighting the need to study further the kinetics, the nature and concentrations of dissolved 3C* under various atmospheric conditions. In addition, the molecular properties and atmospheric behavior of 2,4-hexadienedial were found different from those of glyoxal and 2-butenedial, highlighting the need for detailed atmospheric reactivity studies of polyfunctional compounds, in particular unsaturated compounds. [Display omitted] • Unsaturated dicarbonyls can partition to the cloud aqueous phase. • Red shifts enhance the aqueous-phase photolysis kinetics of unsaturated dicarbonyls. • Unsaturated dicarbonyls exhibit fast oxidation kinetics. • Dissolved 3C* may significantly contribute to condensed phase reactivity. • Unsaturated dicarbonyls exhibit short daylight atmospheric lifetimes. [ABSTRACT FROM AUTHOR]

Abstract: Currently, cloud chemistry models are including more detailed and explicit multiphase mechanisms based on laboratory experiments that determine such values as kinetic constants, stability constants of complexes and hydration constants. However, these models are still subject to many uncertainties related to the aqueous chemical mechanism they used. Particularly, the role of oxidants such as iron and hydrogen peroxide in the oxidative capacity of the cloud aqueous phase has typically never been validated against laboratory experimental data. To fill this gap, we adapted the M2C2 model (Model of Multiphase Cloud Chemistry) to simulate irradiation experiments on synthetic aqueous solutions under controlled conditions (e.g., pH, temperature, light intensity) and for actual cloud water samples. Various chemical compounds that purportedly contribute to the oxidative budget in cloud water (i.e., iron, oxidants, such as hydrogen peroxide: H2O2) were considered. Organic compounds (oxalic, formic and acetic acids) were taken into account as target species because they have the potential to form iron complexes and are good indicators of the oxidative capacity of the cloud aqueous phase via their oxidation in this medium. The range of concentrations for all of the chemical compounds evaluated was representative of in situ measurements. Numerical outputs were compared with experimental data that consisted of a time evolution of the concentrations of the target species. The chemical mechanism in the model describing the “oxidative engine” of the H x O y /iron (H x O y = H2O2, HO2 /O2 − and HO ) chemical system was consistent with laboratory measurements. Thus, the degradation of the carboxylic acids evaluated was closely reproduced by the model. However, photolysis of the Fe(C2O4)+ complex needs to be considered in cloud chemistry models for polluted conditions (i.e., acidic pH) to correctly reproduce oxalic acid degradation. We also show that iron and formic acid lead to a stable complex whose photoreactivity has currently not been investigated. The updated aqueous chemical mechanism was compared with data from irradiation experiments using natural cloud water. The new reactions considered in the model (i.e., iron complex formation with oxalic and formic acids) correctly reproduced the experimental observations. [Copyright &y& Elsevier]

[Display omitted] • Promising degradation efficiency of pollutants in sewage treatment plant water. • Predominant non-radical pathway in PDS-containing systems. • Predominant sulfate radical pathway in PMS-containing systems. • SO 4 •−, •OH and 1O 2 were generated in both CuFe 2 O 4 -PDS/PMS systems. • Correlation between XPS and radical quenching investigations. Copper ferrites (CuFe 2 O 4) nanopowder was prepared via hydrothermal method followed by annealing at 500 °C, and XRD, SEM, XPS and UPS were employed for its characterization. CuFe 2 O 4 was tested for the catalytic degradation of bisphenol A (BPA) in the dark and under UVA light, both in the presence of peroxymonosulfate (PMS) or peroxydisulfate (PDS) as radical precursor under natural pH of 6.2. While the individual photo-induced processes i.e. , photocatalysis (using CuFe 2 O 4 alone) and photolysis of either PMS or PDS, exhibited limited efficiencies in BPA degradation, a significant increase of performance was observed by combining CuFe 2 O 4 and UVA light with either PMS or PDS with a synergy effect of 3.8 and 34.1, respectively. Under the optimal conditions, employing 0.5 g/L of nanopowder, the degradation constant of 25 µM BPA was 0.211 min−1 with 2 mM of PMS and 0.018 min−1 with 2 mM of PDS, and resulted in the complete degradation of BPA within less than 20 min. The activation mechanism of PMS and PDS using CuFe 2 O 4 was elucidated, revealing sulfate radicals as the primary reactive species in PMS-containing systems, whereas a predominantly non-radical pathway was observed in the presence of PDS. Indeed, advanced spectroscopic techniques indicated that surface copper played an important role in the non-radical pathway. Furthermore, the CuFe 2 O 4 /PMS/UVA system exhibited high performance in the degradation of different phenolic compounds including BPA, phenol and p-nitrophenol in real water matrices. These achievements were observed across different real water matrices with a particular emphasis on sewage treatment plant water. [ABSTRACT FROM AUTHOR]

Abstract: The photochemical behaviour of H2O2 in cloud aqueous phase was investigated from a large amount of in situ cloud droplet sampling data. Then we performed laboratory irradiation experiments of real cloud samples, free from gaseous chemistry, in order to factorise between gas phase and liquid phase photochemical reactions. H2O2 was revealed to be sensitive to solar radiation, with higher concentrations during the day. H2O2 was dependent on the degree of air mass pollution with anthropogenic influences leading to lower values of aqueous H2O2. We observed higher differences between day and night of H2O2 concentrations for air masses influenced by anthropogenic activities (mainly Northern direction) compared to those form remote areas (oceanic). Contrary to this field diurnal trend, during laboratory irradiation experiments of the cloud aqueous phase, the concentration showed a regular linear decrease leading to the conclusion that photolysis is more important than photoproduction in cloud aqueous phase. So the diurnal cycle observed during field measurements is due to the high mass transfer from gas phase to liquid phase favoured by the high dispersion of liquid phase and the high solubility of hydrogen peroxide. As a consequence, H2O2 can act as a photochemical source of ls in cloud aqueous phase. [Copyright &y& Elsevier]

We report the results of two complementary studies of the heterogeneous reaction between gas-phase ozone and aqueous chlorophyll. In the first experiment, the chlorophyll is present at the air-water interface and its concentration is measured as a function of time, using laser-induced fluorescence, to obtain the surface kinetics. Under most experimental conditions, these are well described using a Langmuir-Hinshelwood formalism. The second experiment was carried out in a wetted-wall flowtube apparatus and measured the uptake coefficient of ozone by the chlorophyll solution. The uptake coefficient decreases with increasing ozone concentration, consistent with the surface mechanism found in the fluorescence experiment The two experiments agree that the uptake coefficient for ozone by such chlorophyll samples is ~2-5 × 10-6 with unpolluted boundary layer ozone concentrations. At low wind speed, the reaction between ozone and chlorophyll at the sea surface may represent the driving force for ozone deposition at the ocean surface, significantly increasing its deposition velocity there. [ABSTRACT FROM AUTHOR]

• The effect of HA coating on MPs was studied in photo-Fenton-like process. • Humic acid coating enhances the H 2 O 2 and S 2 O 8 2− activation for BPA degradation. • Reactive species were identified (OH and SO 4 –) through scavenging experiments. • The recycling and reuse of MP/HA show no loss of activity. • The efficiency of MP/HA was tested in real wastewater sample. 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 (H 2 O 2) and persulfate (S 2 O 8 2−) using Bisphenol A (BPA) as a model pollutant. The role of HA coating, pH value and H 2 O 2 /S 2 O 8 2− concentration were investigated. A positive contribution of HA coating on H 2 O 2 and S 2 O 8 2− activation was found. The highest BPA degradation rates were achieved at acidic conditions (pH 3) with both H 2 O 2 and S 2 O 8 2−, 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 SO 4 – were identified as the main reactive species involved in the BPA abatement. An important contribution of the S 2 O 8 2− photolysis on the overall BPA transformation was highlighted. The reuse of the catalyst was investigated and similar efficiency using H 2 O 2 and S 2 O 8 2− 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. [ABSTRACT FROM AUTHOR]

• Novel activation of oxidants with the new cubic co-doped magnetite nanoparticles. • High stability of the synthesized photocatalyst after 5 cycles of the processes. • 67% of Sulfalene degradation in real wastewater and under the optimum condition. • 85% of Sulfalene mineralization during the UVA/ Fe 2.5 Co 0.3 Zn 0.2 O 4 /PS process. • Production of nontoxic products during the UVA/Fe 2.5 Co 0.3 Zn 0.2 O 4 /PS process. In this work, the cubic cobalt and zinc doped and co-doped magnetite nanocatalysts were synthesized and characterized using different analysis. The so-synthesized photocatalysts were used for the activation of hydrogen peroxide (HP) and persulfate (PS) under UVA irradiation. The integration of Fe 2.5 Co 0.3 Zn 0.2 O 4 improved the activation of PS and HP; wherein, the UVA/Fe 2.5 Co 0.3 Zn 0.2 O 4 /PS process demonstrated higher degradation performance for Sulfalene (SFL) as a veterinary pharmaceutical contaminant in water. Afterward, the effect of different physicochemical parameters was studied and the radicals generated through the process were identified using chemical scavengers. UVA/Fe 2.5 Co 0.3 Zn 0.2 O 4 /PS process brought about 67% of SFL degradation in real wastewater. Moreover, 85% of TOC removal was achieved within 15 h of the above-mentioned process. Eventually, the phototoxicity of the untreated and treated SFL solution after 120 min of the UVA/Fe 2.5 Co 0.3 Zn 0.2 O 4 /PS process was studied using Lemna minor aquatic species. [ABSTRACT FROM AUTHOR]

In this work, the decomposition of phenanthrene (PHE) in mimic and real soil washing (SW) effluents was investigated using UVB light assisted activation of hydrogen peroxide (H 2 O 2) and peroxydisulfate (PDS) oxidation processes. The impact of oxidant concentration, initial pH, and coexisting inorganic anions (Cl−, HCO 3 − and NO 3 −) on PHE removal was evaluated. PHE degradation efficiency under UVB irradiation followed the order of UVB/PDS > UVB/H 2 O 2 > UVB. The increase of PHE decomposition efficiency was observed with increasing oxidant dose in the range of 2–30 mM upon the two processes. It was found Cl− played different roles in the two activation systems depending on the solution pH and Cl− concentration. The influence of HCO 3 − on PHE elimination was negligible in the UVB/PDS process, while an inhibitory effect was observed in the UVB/H 2 O 2 system. Nitrate inhibited the PHE decay in both UVB/H 2 O 2 and UVB/PDS processes at the investigated pH 3.3, 7.1 and 8.6. Finally, the application of the two activation processes to the treatment of real SW effluents indicated that up to 85.0% of PHE degradation could be reached under 6 h UVB irradiation with PDS, indicating UVB/PDS process is a promising alternative for SW effluent treatment. • PDS is more efficient than H 2 O 2 for UVB decay of PHE in soil washing (SW) effluent. • UVB/PDS process is less impacted by the inorganic ions (Cl−, HCO 3 − and NO 3 −). • UVB/PDS is a promising and sustainable process for real SW effluent treatment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

For the last 25 years, CO-PDD (Cézeaux-Aulnat-Opme-puy de Dôme) has evolved to become a full instrumented platform for atmospheric research. It has received credentials as a national observing platform in France and is internationally recognized as a global station in the GAW (Global Atmosphere Watch) network. It is a reference site of European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS (Integrated Carbon Observing System). The site located on top of the puy de Dôme mountain (1465 m a.s.l.) is completed by additional sites located at lower altitudes and adding the vertical dimension to the atmospheric observations: Opme (660 m a.s.l.), Cézeaux (410 m), and Aulnat (330 m). The integration of different sites offers a unique combination of in situ and remote sensing measurements capturing and documenting the variability of particulate and gaseous atmospheric composition, but also the optical, biochemical, and physical properties of aerosol particles, clouds, and precipitations. Given its location far away from any major emission sources, its altitude, and the mountain orography, the puy de Dôme station is ideally located to sample different air masses in the boundary layer or in the free troposphere depending on time of day and seasons. It is also an ideal place to study cloud properties with frequent presence of clouds at the top in fall and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment, scientific studies at the puy de Dôme strongly contribute to improving knowledge in atmospheric sciences, including the characterization of trends and variability, the understanding of complex and interconnected processes (microphysical, chemical, biological, chemical and dynamical), and the provision of reference information for climate/chemistry models. In this context, CO-PDD is a pilot site to conduct instrumental development inside its wind tunnel for testing liquid and ice cloud probes in natural conditions, or in situ systems to collect aerosol and cloud. This paper reviews 25 years (1995–2020) of atmospheric observation at the station and related scientific research contributing to atmospheric and climate science. [ABSTRACT FROM AUTHOR]

For the last twenty-five years, CO-PDD (Cézeaux-Aulnat-Opme-puy de Dôme) has evolved to become a full instrumented platform for atmospheric research. It is nationally accredited by CNRS, the French national center for scientific research, and recognized as a global station in the GAW network (Global Atmospheric Watch). It is a reference site of the European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS (Integrated Carbon Observing System). The site located on-top of the puy de Dôme mountain (1465 m a.s.l.) is completed by additional sites located at lower altitudes and adding the vertical dimension to the atmospheric observations: Opme (660 m a.s.l.), Cézeaux (410 m) and Aulnat (330 m). On the sites has been developed a unique combination of in-situ and remote sensing measurements capturing and documenting the variability of particulate and gaseous atmospheric composition, but also the optical, biochemical and physical properties of aerosol particles, clouds and precipitations. Given its location far away from any major emission sources, its altitude and the mountain orography, the puy de Dôme station is ideally situated to sample different air masses in the boundary layer or in the free troposphere depending on time of day and seasons. It is also an ideal place to study cloud properties with frequent presence of clouds at the top in autumn and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment, scientific studies at puy de Dôme strongly contribute to improving the knowledge in atmospheric sciences including the characterization of trends and variability, the understanding of complex and interconnected processes (microphysical, chemical, biological, chemical and dynamical) and providing a reference point for climate models. In this context, CO-PDD is a pilot site to conduct instrumental development inside its wind tunnel for testing liquid/ice cloud probes in natural conditions, or in-situ systems to collect aerosol and cloud. This paper reviews 25 years (1995-2020) of atmospheric observation at the station, and related scientific research contributing to atmospheric and climate science. [ABSTRACT FROM AUTHOR]

In this study, we employed nano zero-valent iron catalysts supported on graphitized carbon (GC-nZVI) catalyst to efficiently degrade BPA under circumneutral pH conditions in both dark and UVA radiation. The GC-nZVI catalyst was characterized using specific techniques (XPS, FTIR, BET, etc.), and was used to activate both PS and PMS in solution. Although no significant BPA degradation constant (k BPA) was determined using PS/PMS or GC-nZVI alone, a significant synergistic effect was observed in the system. Under dark conditions, k BPA increased from 0.01 min−1 to 0.17 when PS was used, both in the dark and under UVA. Notably, when PMS was present in the system, the improvement was even higher with k BPA reaching 0.18 and 0.26 min−1 under dark and UVA conditions, respectively. To further support the synergistic effect, it was found that 80% of mineralization was achieved within 2 h of UVA exposure. Chemical quenching experiments were conducted using selective probes and kinetic modelling showed that the activation of PS/PMS produced sulfate radicals (SO 4 •−), hydroxyl radicals (•OH) and ferryl ions (FeIVO2+) in both systems. Additionally, GC-nZVI/PMS system demonstrated good stability in recycling experiments, with up to 70% of BPA still being degraded after 3 cycled in 1 h under UVA. In conclusion, the degradation efficiencies of GC-nZVI/PMS and GC-nZVI/PS systems under dark and UVA radiation were assessed for three different EDCs (BPA, E2, and EE2) in both tap and sewage treatment plant waters. This study has demonstrated that the highly efficient GC-nZVI/PS/UVA or GC-nZVI/PMS/UVA system has significant potential for application in different water matrix, and our findings provide insights into the design of heterogeneous Fenton-like and photo-Fenton-like catalysts. [Display omitted] • GC-nZVI with PS and PMS systems is able to degrade and mineralize BPA in water. • The steady-state concentration of reactive species such as HO.•, SO 4 •- and FeVIO2+ is determined • The main degradation products of BPA are characterized. • Efficient BPA, E2 and EE2 degradation was obtained using GC-nZVI + PMS under UVA. • 60% of EDCs degradation in Tap and STP waters was reached after 90 min. [ABSTRACT FROM AUTHOR]

Abstract The irradiation under simulated sunlight of some phenolic compounds typically emitted in ambient air by biomass burning, namely vanillin and acetosyringone, yielded intermediates with humic-like fluorescence properties that can be assimilated to humic-like substances (HULIS). Evidence was obtained by ultra-high-resolution mass spectrometry of the occurrence of oligomerization processes up to the formation of trimeric species. In contrast, the irradiation of other biomass-burning compounds such as vanillic acid, m-cresol and guaiacol did not yield either HULIS-type fluorescence or oligomers. We suggest that the photolysis of biomass-burning compounds is a potential HULIS source in the atmosphere, if the relevant substrates undergo photoinduced oligomerization reactions. Graphical abstract Image 1 Highlights • Humic-like fluorescence is produced by irradiation of biomass-burning phenols. • Vanillin and acetosyringone are involved in the process. • Evidence of oligomerization, up to formation of trimeric species. • Norrish-type and phenoxyl reactions are reasonable oligomerization pathways. • This is a potential route to atmospheric humic-like substances (HULIS). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SO 5 − plays a significant role in aniline oxidation in the Fe(III)-S(IV) system. • SO 5 − oxidizes aniline through direct and indirect pathways. • Aniline oxidation can be effectively enhanced via sequential S(IV) replenishing. • S(IV) replenishing accelerates both the oxysulfur radicals cycle and Fe(III)/Fe(II) cycle. Abstract In this paper, the efficiency of Fe(III)-S(IV) system used for advanced oxidation processes (AOPs) has been investigated using aniline as a pollutant model compound in water. The chemical kinetics, influencing factors, and mechanism of aniline oxidation are examined with an emphasis on the contribution of the different oxysulfur radicals (mainly SO 4 − and SO 5 −). Our results show a significant enhancement in the efficiency of aniline oxidation observed at pH 4.0 with 1.0 mM S(IV) and 0.1 mM Fe(III) concentrations. Moreover, the degradation efficiency drastically decreases to 10% in the absence of oxygen indicating the significant role of oxygen in this type of process. Through competition kinetic experiments and radical scavenger experiments, it is shown that SO 5 − is responsible for about 60% of the aniline oxidation in the Fe(III)-S(IV) system under the typical conditions investigated in this work. For the first time we have determined the second order rate constant between SO 5 − and aniline (5.8 ± 0.6 × 106 M−1 s−1 (at pH 3.0) and SO 4 − and aniline 7.7 ± 0.5 × 109 M−1 s−1 (at pH 3.0)). Sequential experiments with successive additions of sulfite drastically improve the oxidation efficiency. These findings may provide a precise understanding of the overall mechanism and may have promising implications in developing a new cost-effective technology for the treatment of organic compounds-containing water. Furthermore, the results of this work help to understand the relevance and mechanism of organic contaminants oxidation by SO 5 −, which has not been given much attention in conventional SR-AOPs using peroxymonosulfate. [ABSTRACT FROM AUTHOR]

In this study we have investigated the efficiency Cobalt (II) (Co(II)) for the activation of sulfite ions following the oxidation of paracetamol used as model contaminants. Physico-chemical parameters that can impact the paracetamol degradation (pH, initial paracetamol concentration, Co(II)/S(IV) molar ratio, oxygen concentration) and contribution of various radicals were investigated in order to elucidate the chemical mechanism. Main results show that the pH is a key factor controlling the efficiency in the system Co(II)/Sulfite. Higher efficiency is observed for pH between 9.0 and 10.0. Increasing S(IV) concentrations, until 1 mM, slightly promoted the degradation of paracetamol. In fact, an excess of sulfite ions inhibits the reaction through the scavenging of SO 4 − and SO 5 − . Moreover, degradation efficiency drastically decreases from ∼ 85% to less than 5% in absence of oxygen. SO 4 − was confirmed to be the main oxidant responsible for the paracetamol degradation. For the first time we determined the second order rate constant between SO 4 − and paracetamol (1.33 ± 0.79 × 10 9  M −1  s −1 (at pH 5) and 6.14 ± 0.99 × 10 8  M −1  s −1 (at pH 11.0)). Moreover, radical-scavenging experiments also suggest the possible implication of SO 5 − . Hence, this work provides a precise understanding of the overall mechanism and a new promising strategy by using sulfite and transition metal such as Co(II) to promote organic compounds degradation in water under neutral and alkaline pH conditions. [ABSTRACT FROM AUTHOR]

• The recovered magnetite served as the iron source for photo-Fenton reactions. • Iron of the recovered magnetite was stabilized using citrate as a chelating agent. • Decomposition of the Ferric-citrate complex did not provide harmful by-products. • 77% of carbamazepine was degraded during the adopted photo-Fenton process. • The performance of the recycled magnetite was stable in five successive cycles. Herein, the recycled magnetite obtained from industrial ferrous scrap was used as an eco-friendly, sustainable iron source in the photo-Fenton degradation of carbamazepine (CBZ), an emerging contaminant in the aqueous environment. Citrate was used as a robust chelating agent to trap and stabilize the iron required for the Fenton reaction. The results proved the formation of the Fe(III)-citrate complex, followed by the reduction of iron to Fe(II) and the formation of harmless molecules such as malonate under UV radiation. The adopted photo-Fenton process in the presence of magnetite (0.3 g/L), H 2 O 2 (0.5 mM), and citrate (0.1 mM) led to about 77 % degradation of CBZ. Then, degradation efficiency was improved to 99 % by increasing the prior contact time between citrate and magnetite. In addition, 1 mM of citrate and 2 mM of H 2 O 2 were found to be the optimal values for the degradation of CBZ under the adopted photo-Fenton process. Eventually, the experiments illustrated that the recycled magnetite could be used in the photo-Fenton process in five successive cycles without losing its efficiency. [ABSTRACT FROM AUTHOR]

The exploitation of organic waste as a source of bio-based substances to be used in environmental applications is gaining increasing interest. In the present research, compost-derived bio-based substances (BBS-Cs) were used to prepare hybrid magnetic nanoparticles (HMNPs) to be tested as an auxiliary in advanced oxidation processes. Hybrid magnetic nanoparticles can be indeed recovered at the end of the treatment and re-used in further water purification cycles. The research aimed to give new insights on the photodegradation of caffeine, chosen as marker of anthropogenic pollution in natural waters, and representative of the contaminants of emerging concern (CECs). Hybrid magnetic nanoparticles were synthetized starting from Fe(II) and Fe(III) salts and BBS-C aqueous solution, in alkali medium, via co-precipitation. Hybrid magnetic nanoparticles were characterized via X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The effect of pH, added hydrogen peroxide, and dissolved oxygen on caffeine photodegradation in the presence of HMNPs was assessed. The results allow for the hypothesis that caffeine abatement can be obtained in the presence of HMNPs and hydrogen peroxide through a heterogeneous photo-Fenton mechanism. The role of hydroxyl radicals in the process was assessed examining the effect of a selective hydroxyl radical scavenger on the caffeine degradation kinetic. [ABSTRACT FROM AUTHOR]

By exploiting the regioselective protection of the hydroxyl groups of silibinin along with the well-known phosphoramidite chemistry, we have developed an efficient strategy for the synthesis of new silibinin-modified species, which we have named Phosphate-Linked Silibinin Dimers (PLSd), in which the monomer units are linked by phosphodiester bonds. The antioxidant abilities of the new PLSd were estimated on HepG2 cells using DPPH free radical scavenging and xanthine/xanthine oxidase assays. The new phosphate-metabolites showed a higher anti-oxidant activity than the silibinin, as well as very low toxicity. The ability to scavenge reactive oxygen species (ROS) such as singlet oxygen (1O2) and hydroxyl radical (HO•) reveals that the two dimers are able to scavenge HO• about two times more effectively than silibinin. Finally, solubility studies have shown that the PLSd present good water solubility (more than 20 mg·L−1) under circumneutral pH values, whereas the silibinin was found to be very poorly soluble (less than 0.4 mg·L−1) and not stable under alkaline conditions. Together, the above promising results warrant further investigation of the future potential of the PLSd as anti-oxidant metabolites within the large synthetic polyphenols field. [ABSTRACT FROM AUTHOR]

TiO 2 nanotube (TNT) layers are prepared via electrochemical anodization of Ti foil in ethylene glycol-based electrolyte containing fluoride ions. Using spin-coating of Fe(III) precursor solutions of different concentrations (10 µM to 10 mM), iron surface-modified TNT (Fe-TNT) layers are formed after annealing at 450 °C for 2 h in air. The Fe-TNT layers are comprehensively characterized by XRD, SEM, DRS and XPS. To identify and assess the contribution of photocatalysis and Fenton-based processes that are simultaneously triggered by Fe-TNT layers, degradation of caffeine is investigated in the dark and under UVA with and without the presence of 500 µM H 2 O 2. It has been found that in the presence of H 2 O 2 under UVA, 100 µM Fe-TNT can degrade 67 % of caffeine after 3 h, of which 4 % is from photolysis, 23.5 % from photocatalysis and 39.5 % from Fenton-based processes. It is important to note that Fenton-based reactions are due to the iron leaching, while the main reactive oxygen species are identified as hydroxyl radicals. In addition, the main degradation by-products are identified by LC-MS and IC-MS techniques, thus leading to the proposal of different degradation pathways of caffeine. To sum up, the research's findings provide novel insights into the concept of photochemical versatility, which is only obliquely explored in the corpus of previous research. [Display omitted] • Fe modified TiO 2 nanotube layers trigger simultaneous processes. • Contribution of photocatalysis, Fenton and photolysis is assessed for the first time. • Fenton process is dependent to iron leaching from Fe-TiO 2. • Efficient degradation of caffeine under UVA in the presence of H 2 O 2. • Degradation pathway of caffeine is proposed using LC-MS and IC-MS data. [ABSTRACT FROM AUTHOR]

Irradiated nitrophenols can produce nitrite and nitrous acid (HONO) in bulk aqueous solutions and in viscous aqueous films, simulating the conditions of a high-solute-strength aqueous aerosol, with comparable quantum yields in solution and viscous films (10-5-10-4 in the case of 4-nitrophenol) and overall reaction yields up to 0.3 in solution. The process is particularly important for the para-nitrophenols, possibly because their less sterically hindered nitro groups can be released more easily as nitrite and HONO. The nitrophenols giving the highest photoproduction rates of nitrite and HONO (most notably, 4-nitrophenol and 2-methyl-4-nitrophenol) could significantly contribute to the occurrence of nitrite in aqueous phases in contact with the atmosphere. Interestingly, dew-water evaporation has shown potential to contribute to the gas-phase HONO levels during the morning, which accounts for the possible importance of the studied process. [ABSTRACT FROM AUTHOR]

When irradiated in paddy-field water, propanil (PRP) undergoes photodegradation by direct photolysis, by reactions with •OH and CO3•-, and possibly also with the triplet states of chromophoric dissolved organic matter. Irradiation also inhibits the nonphotochemical (probably biological. degradation of PRP. The dark- and light-induced pathways can be easily distinguished because 3,4-dichloroaniline (34DCA, a transformation intermediate of considerable environmental concern) is produced with almost 100% yield in the dark but not at all through photochemical pathways. This issue allows an easy assessment of the dark process(es. under irradiation. In the natural environment, we expect PRP photodegradation to be important only in the presence of elevated nitrate and/or nitrite levels, e.g., [NO3-] approaching 1 mmol L-1 (corresponding to approximately 60 mg L-1). Under these circumstances, •OH and CO3•- would play a major role in PRP phototransformation. Because flooded paddy fields are efficient denitrification bioreactors that can achieve decontamination of nitrate-rich water used for irrigation, irrigation with such water would both enhance PRP photodegradation and divert PRP dissipation processes away from the production of 34DCA, at least in the daylight hours. [ABSTRACT FROM AUTHOR]