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The preparation of anodic TiO

International audience; In the present work, the photo-Fenton-like process based on the use of the Fe2.5Co0.3Zn0.2O4/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.

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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. Graphical abstract

International audience; 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 Fe2.5Co0.3Zn0.2O4 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 Fe3O4, Fe2.5Co0.3Zn0.2O4, CuCr-LDH, and Fe3O4/CuCr-LDH composite. Studying the efficiency of the photo-Fenton-like degradation process in the presence of the Fe2.5Co0.3Zn0.2O4/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.photo-Fenton-like process at natural pH, > 90% of pollutants mixture was decomposed. The experiments fulfilledin near-real conditions demonstrated I) the high stability and magnetically recoverability of the photocatalys

International audience; The crucial role of manganese(III) species in the oxidative and catalytic reactivity of manganese oxides have been widely reported. However, the direct activation of radical precursors by Mn(III) oxides is still a matter of discussion. In this work, the ability of Mn(III)-bearing oxide (Mn2O3) for activation of peroxydisulfate (PS) and peroxymonosulfate (PMS) was evaluated and compared using caffeine (CAF) as a model pollutant. Complete CAF removal was achieved with 5 mM of PS or PMS after 8 h of reaction time, whereas 48% of mineralization was obtained after 70 h of reaction when PMS was used as oxidant. Electron paramagnetic resonance spin trapping (EPR) and radical scavenging experiments showed that the sulfate radical (SO4•–) was the dominant radical in the Mn2O3/PMS system. In comparison, a non-radical mechanism such as Mn2O3 surface-activated PS promoted the removal of CAF in the system of Mn2O3/PS. Liquid chromatography coupled to mass spectrometry analyses enabled the detection of main degradation products and the proposition of the CAF degradation pathways. Investigations in the real sewage treatment plant water showed that the decrease of CAF removal observed in wastewater as compared to pure water can be alleviated by increasing the Mn2O3 dosage. These findings highlight the great ability of Mn-species in PS or PMS activation in different water matrices, which have important implications for the development of novel wastewater treatment technologies.

International audience; In this paper, the degradation of three endocrine-disrupting chemicals (EDCs): bisphenol A (BPA), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) by manganite (γ-MnOOH) activated peroxymonosulfate (PMS) was investigated. Preliminary optimisation experiments showed that complete degradation of the three EDCs was achieved after 30 min of reaction using 0.1 g L−1 of γ-MnOOH and 2 mM of PMS. The degradation rate constants were determined to be 0.20, 0.22 and 0.15 min−1 for BPA, E2 and EE2, respectively. Combining radical scavenging approaches, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses, we revealed for the first time that about 40% of EDCs degradation can be attributed to heterogeneous electron transfer reaction involving freshly generated Mn(IV), and 60% to sulfate radical degradation pathway. The influence of various inorganic ions on the γ-MnOOH/PMS system indicated that removal efficiency was slightly affected by chloride and carbonate ions, while nitrate and nitrite ions had negligible impacts. The application of γ-MnOOH/PMS system in real sewage treatment plant water (STPW) showed that degradation rate constants of EDCs decreased to 0.035–0.048 min−1 and complete degradation of the three EDCs after 45 min. This study provides new insights into the reactivity of combined γ-MnOOH and PMS, and opens new ways for the application of Mn-bearing species in wastewater treatment technologies.

International audience; 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 (FeCO3) was detected indicating that carbonate ion (CO32−) 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 FeCO3 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.

Despite the widespread presence of hydrogen peroxide (H

International audience; 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.

In the present study, comparison of activation efficiencies of hydrogen peroxide (H2O2) and persulfate (PS, Na2S2O8) 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, H2O2 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 H2O2 and Na2S2O8. 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/H2O2/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/H2O2/UV reaction, p-HPA degradation rate (Rp-HPA) increased fast from pH 2.5 to 7.5, then it began to decrease when pH increased to 9.0. While Rp-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 SO4 − 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).

In this paper, the degradation of three endocrine-disrupting chemicals (EDCs): bisphenol A (BPA), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) by manganite (γ-MnOOH) activated peroxymonosulfate (PMS) was investigated. Preliminary optimisation experiments showed that complete degradation of the three EDCs was achieved after 30 min of reaction using 0.1 g L

[EN] Enrofloxacin (ENR) belongs to the fluoroquinolone (FQ) antibiotics family, which are contaminants of emerging concern frequently found in effluents. Although many works studying photo-Fenton process for FQ degradation have been reported, there are no reports analysing in deep the effect of iron complexation, as well as other metals, towards FQs' photolysis, which, evidently, also contributes in the overall degradation of the pollutant. Therefore, in this work, we report a comparative study between the photochemical fate of ENR and its complex with Fe(III) under simulated sunlight irradiation. In addition, the effect of dissolved oxygen, self-sensitization process, and H2O2 addition on the studied photochemical systems are also investigated. Results indicate that, for free and iron-complexed ENR, singlet oxygen (O-1(2)) is generated from the interaction of its triplet state with ground state oxygen. Half-life time (t(1/2)) of ENR under sun simulated conditions is estimated to be around 22 min, while complexation with iron enhances its photostability, leading to a t(1/2) of 2.1 h. Such finding indicates that at least the presence of iron, might notably increase the residence time of these pollutants in the environment. Eventually, only with the addition of H2O2, the FQ-iron complex is efficiently degraded due to photo-Fenton process even at circumneutral pH values due to the high stability of the formed complex. Finally, after LC/FT-ICR MS analysis, 39 photoproducts are detected, of which the 14 most abundant ones are identified. Results indicate that photoproducts formation is pH and iron dependent., This paper is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 765860 (AQUAlity). The paper reflects only the authors' view and the Agency is not responsible for any use that may be made of the information it contains. M.B. and G. M. acknowledge financial support from the CAP 20-25 I-site project.

International audience; 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 Sscheme 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.

International audience; 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.

International audience; 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 (H2O2) and peroxydisulfate (PDS) oxidation processes. The impact of oxidant concentration, initial pH, and coexisting inorganic anions (Cl, HCO3 and NO3) on PHE removal was evaluated. PHE degradation efficiency under UVB irradiation followed the order of UVB/PDS > UVB/H2O2 > UVB. The increase of PHE decomposition efficiency was observed with increasing oxidant dose in the range of 2e30 mM upon the two processes. It was found Cl played different roles in the two activation systems depending on the solution pH and Clconcentration. The influence of HCO3 on PHE elimination was negligible in the UVB/PDS process, while an inhibitory effect was observed in the UVB/H2O2 system. Nitrate inhibited the PHE decay in both UVB/ H2O2 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.

International audience; Despite the widespread presence of hydrogen peroxide (H2O2) in surface water and groundwater systems, little is known about the impact of environmental levels of H2O2 on the redox activity of minerals. Here we demonstrate that environmental concentrations of H2O2 can alter the reactivity of birnessite-type manganese oxide, an earth-abundant functional material, and decrease its oxidative activity in natural systems across a wide range of pH values (4-8). The H2O2-induced reductive dissolution generates Mn(ii) that will re-bind to MnO2 surfaces, thereby affecting the surface charge of MnO2. Competition of Bisphenol A (BPA), used as a target compound here, and Mn(ii) to interact with reactive surface sites may cause suppression of the oxidative ability of MnO2. This suppressive effect becomes more effective in the presence of oxyanions such as phosphate or silicate at concentrations comparable to those encountered in natural waters. Unlike nitrate, adsorption of phosphate or silicate onto birnessite increased in the presence of Mn(ii) added or generated through H2O2-induced reduction of MnO2. This suggests that naturally occurring anions and H2O2 may have synergetic effects on the reactivity of birnessite-type manganese oxide at a range of environmentally relevant H2O2 amounts. As layered structure manganese oxides play a key role in the global carbon cycle as well as pollutant dynamics, the impact of environmental levels of hydrogen peroxide (H2O2/MnO2 molar ratio

International audience; 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 Fe2.5Co0.3Zn0.2O4 improved the activation of PS and HP; wherein, the UVA/Fe2.5Co0.3Zn0.2O4/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/Fe2.5Co0.3Zn0.2O4/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/Fe2.5Co0.3Zn0.2O4/PS process was studied using Lemna minor aquatic species.

International audience; In the present work, the degradation of three estrogens (17β-estradiol (E2), estrone (E1) and 17α-ethinylestradiol (EE2)) was investigated under photoactivation of hydrogen peroxide and persulfate. Lab-scale irradiation experiments showed that both UVA and UVB radiations are able to photoactivate the oxidant precursors, although UVB is more efficient to generate radicals and therefore to degrade the targets. The efficiency of both oxidant precursors was investigated showing higher efficiency in the system with persulfate. The pseudo-first order degradation rate constants and the second order rate constants between the hydroxyl or the sulfate radicals and estrogens were measured. In order to evaluate the process efficiency in real treatment conditions, the degradation of the estrogens spiked into sewage treatment plant effluent was studied. Measurements of second order rate constants between the radical and the effluent organic matter by laser flash photolysis allowed to understand the involved quenching mechanisms. A Yeast Estrogen Screen (YES) assay was used to follow the decrease in estrogenic activity during the estrogen degradation. This assay permitted to ensure that the studied processes are not only able to degrade the estrogens but also to remove their estrogenic activity.

Nitrogen molecules are present in the atmosphere also as inorganic ions (ammonium, nitrate…) and organic (peptides and proteins). Nowadays, there is still poor knowledge concerning the sources and fate of proteins and peptides in the atmosphere. In a larger context aiming at exploring microbial communities’ functioning in the atmosphere, the goal of this study is to examine the atmospheric proteome (peptide and protein contents, sequence, size distribution, biological functions) in the different atmospheric compartment (aerosols, cloud and rain waters).Aerosols, cloud water and rain samples were collected at remote places nearby Clermont – Ferrand city (France) and from the Mountain “Puy de Dôme” (1465 m asl). Cloud droplet impactors and high volume impingers were used for allowing immediate fixation of the samples, by collecting within a protease inhibitor solution. Samples were filtered (0.22 µm porosity) and the proteins from water were digested using trypsin. The peptides were purified by solid phase extraction (SPE) method, concentrated by lyophilisation and analysed by LC – HRMS and MS². Preliminary results indicate the recurrence of certain small peptides in particular. Some of these most frequently observed peptides were selected as models for photochemical experiments. Briefly, these small peptides were irradiated under solar simulated conditions and products were identified by IC – MS, to assess the impact of such processes on the chemical composition of the atmosphere.The next step will consist in analysing our observations along with chemical and biological parameters such as biodiversity, transcriptomic profiles, in order to better understand the interaction between microorganisms and atmosphere processes.

International audience; 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 (3 FL*) 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 3 FL* 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.

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO

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.

International audience; While the use of transition metal oxides in catalyzing advanced oxidation reactions has been widely investigated, very few reports have focused on how the preliminary contact of oxides with target compounds may affect the succession of reaction. In this study, we examined the adsorption and electron transfer reactions of two fluoroquinolones, flumequine (FLU), and norfloxacin (NOR), with goethite (α-FeOOH) or manganese (Mn) oxide, and their impact on the subsequent mineralization of target compounds using HO or SO under UVA irradiation. Intriguingly, higher total organic carbon (TOC) removal was achieved when antibiotics and metal oxides were allowed for preequilibration before starting the oxidation reaction. The rate and extent of TOC removal are strongly dependent on the molecule structure and the redox-active mineral used, and much less on the preequilibration time. This high efficiency can be ascribed to the presence of reduced metal ions, chemically or photochemically generated during the first stage, onto oxide minerals. Oxide-bound Mn plays a crucial role in catalyzing oxidant decomposition and then producing greater amounts of radical species through a photoassisted redox cycle, regardless of the underlying surface, MnO or MnOOH. This finding will be of fundamental and practical significance to Mn-based oxidation reactions and wastewater treatment processes.

International audience; In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HOradical dot, SO4radical dot− and HO2radical dot/O2radical dot−) are generated through activation of hydrogen peroxide (H2O2), sodium persulfate (Na2S2O8) 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/H2O2 and UVA/Na2S2O8 systems whatever the solution’s pH. To explain these results, second order reaction rate constant (kradical, ACTP) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO2radical dot/O2radical dot− 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 Na2S2O8 exhibits synergistic effects rather than antagonism effects with H2O2. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.

International audience; The secondary pollutant 3,4-dichloroaniline (DCA) is produced by the biological degradation of several herbicides, including propanil in paddy fields. The enzymatic hydrolysis of propanil yields DCA with almost quantitative yield. DCA undergoes rather fast photodegradation in paddy water, mostly by direct photolysis. An exception might be represented by the cases (rather rare in paddies) of quite high nitrate concentration (around 50 mg of NO3– L–1), when DCA degradation by CO3•– would play a comparable role to that by direct photolysis. The experimentally measured photoreactivity parameters were used as input data for a photochemical model, which predicted a DCA lifetime of 0.5–1 days in sunlit paddy fields in late May, when propanil is usually applied. The model predictions compare remarkably well with the DCA attenuation data reported in field studies, carried out in paddies in temperate regions. Moreover, a consecutive reaction model based on typical biological (propanil) and photochemical (DCA) lifetimes reproduced quite well the time trends of both compounds in paddies, as reported in the literature. These successful comparisons suggest that photodegradation in general, and direct photolysis in particular, may play a key role in DCA attenuation in paddy water.

International audience; 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.

International audience; Persulfate (PS) activation reaction,which forms sulfate radical (SO4•−), can be used to degrade organic pollutants in water. However, a drawback of this reaction is that the regeneration of ferrous ions requires a high concentration of hydrogen peroxide (Fenton-like reaction) or use of UV radiation. Catechin (CAT), a non-toxic antioxidant of natural origin from tea, is used in this work to improve the sulfate radical-mediated degradation of atenolol (ATL, a model pollutant) in water using relatively low concentrations of reactive chemical species (less than100 μM). To the best of the author's knowledge, the direct effect of CAT on the oxidation state of iron,which is promoted by the reduction of ferric into ferrous ions with the enhancement of SO4•− formation in the presence of PS, is demonstrated for the first time. The enhancement versus inhibition effect of CAT and the chemicalmechanismof the iron-based activation process are explained. Results show that UVA radiation, which is representative of solar light, accelerates the initial degradation of ATL bymore than 30% through ferric iron photolysis. Finally, a reaction mechanism leading to the formation of hydroxyl radicals (HO•) and SO4•− is proposed considering the implication of different activation/reaction chemical steps.

In this work, for the first time, the nonionic surfactant polyoxyethylene-(20)-sorbitan monooleate (Tween 80, C64H124O26) 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 (SO4 -, HO , Cl2 -) 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.

There is increasing evidence that aqueous-phase atmospheric chemistry is an important source of secondary organic aerosols (SOA), but this chemistry is currently not adequately represented in atmospheric models due to the missing information on most products. The main focus of this study is to provide molecular-level insight into the photosensitized reaction mechanism of pyruvic acid (PA) alone in the atmospheric aqueous phase, and of mixtures of PA with glyoxal (GL), a typical and widely occurring carbonyl compound. With two ultrahigh resolution mass spectrometers, ORBITRAP and FT-ICR-MS, a broad and complex spectrum of organic products were unambiguously identified. The detected formation of organic compounds illustrates the progression from C3 to C20 molecules through direct PA photolysis and irradiation of PA + GL. The performed ab-initio calculations indicate that cross-reactions (i.e., PA + GL) are more likely than self-reactions (i.e., PA alone) in clouds and aerosol deliquescent particles. Hence, this result implies that photosensitizers like PA can initiate the transformation of common organic cloud constituents like GL into highly oxygenated multifunctional compounds. These high-molecular- weight compounds that are formed in significant amount could potentially impact optical and cloud-forming properties of aerosols, especially if they partition to the aerosol surface.

International audience; In this work, a new combination of oxidation treatments for the degradation of bisphenol A (BPA) is investigated. This innovative wastewater (WW) treatment includes the use of ferrate (FeO42−) and its decomposition byproducts under dark and UVA irradiation. The oxidation by ferrate leads to a fast but incomplete degradation of BPA with a degradation extent of 45% after 60 min under adopted experimental conditions. However, the ferrate decomposition byproducts which are constituted by solid iron species can be used to further improve the pollutant degradation efficiency. Indeed, ferrate-mediated heterogeneous photo-Fenton process is employed for the first time to enhance the degradation of BPA. With respect to the application for wastewater treatment, UVA irradiation (which is part of solar light), non-toxic and natural origin compounds such as ascorbic acid (AA) and ethylenediamine-N,N′-disuccinic acid (EDDS), are used to design a sustainable process. Under optimized conditions, the degradation extent of BPA using this newly designed treatment reaches almost 100% with AA and 70% with EDDS. In order to assess the feasibility of this treatment, the ferrate-mediated photo-Fenton process is applied to treat municipal wastewater. The obtained results in WW are highly encouraging since a maximum BPA degradation extent of 63% and 60% is observed after 300 min by using AA and EDDS, respectively.

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.

International audience; 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 SO4− and SO5−). 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 SO5− 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 SO5− and aniline (5.8 ± 0.6 × 106 M−1 s−1 (at pH 3.0) and SO4− 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 SO5−, which has not been given much attention in conventional SR-AOPs using peroxymonosulfate.

Polyphenols are active compounds of the medicinal plants widely distributed in nature. Despite the few and common biosynthetic origins, polyphenols encompass many subclasses of structurally different entities with a variety of pharmacological properties. Many studies suggests that the mechanisms by which plant polyphenols exert their protective actions against various diseases, in part are due to their redox properties. Silibinin belongs to flavonolignan class and is a major component (approximately 30%) of the Silymarin complex extracted from milk thistle [Silybum marianum (L.) Gaertn. Carduus marianus L., Asteraceae]. Silibinin exists as a mixture of two diastereomers: Silybin A and Silybin B. Silibinin has long been studied for a large variety of pharmacological properties ranging from its antioxidant activity to neuroprotective and antiviral activities. Unfortunately, its in vivo applications are rather hampered by its very low bioavailability mainly due to low water solubility. In an attempt to improve its biological properties and facilitate the in vivo applications, we have developed an efficient strategy for the synthesis of Silibinin modified namely Phosphate-Linked Silibinin dimers (PLSd) in which the Silibinin monomer units are linked by phosphodiester bond (Figure). Exploiting the selective protection of Silibinin’s hydroxyl groups, we carried out a synthetic approach using the phosphoramidite chemistry. Water solubility of dimers, radical scavenger activity as well as their ability to react with reactive oxygen species (ROS) were determined. In particular, dimers reactivity with 1O2 and HO∙ was determined by use of Rose Bengal (RB) and hydrogen peroxide (H2O2) as respective ROS sources. For this purpose, laser flash photolysis (LFP) experiments were coupled with a kinetic competition approach. In addition to scavenging activity, the serum stability and cytoprotective (X/XO assay on HepG2 cells) behavior of dimers were evaluated.

International audience; Phototransformation is important for the fate in surface waters of the pharmaceuticals diclofenac (DIC) and naproxen (NAP) and for clofibric acid (CLO), a metabolite of the drug clofibrate. The goal of this paper is to provide an overview of the prevailing photochemical processes, which these compounds undergo in the different conditions found in freshwater environments. The modelled photochemical half-life times of NAP and DIC range from a few days to some months, depending on water conditions (chemistry and depth) and on the season. The model indicates that direct photolysis is the dominant degradation pathway of DIC and NAP in sunlit surface waters, and potentially toxic cyclic amides were detected as intermediates of DIC direct phototransformation. With modelled half-life times in the month-year range, CLO is predicted to be more photostable than DIC or NAP and to be degraded mainly by reaction with the •OH radical and with the triplet states of chromophoric dissolved organic matter (3CDOM*). The CLO intermediates arising from these processes and detected in this study (hydroquinone and 4-chlorophenol) are, respectively, a chronic toxicant to aquatic organisms and a possible carcinogen for humans. Hydroquinone is formed with only ∼5% yield upon CLO triplet-sensitised transformation, but it is highly toxic for algae and crustaceans. In contrast, the formation yield of 4-chlorophenol reaches ∼50% upon triplet sensitisation and ∼10% by ·OH reaction. The comparison of model predictions with field data from a previous study yielded a very good agreement in the case of DIC and, when using 4-carboxybenzophenone as proxy for triplet sensitisation by CDOM, a good agreement was found for CLO as well. In the case of NAP, the comparison with field data suggests that its direct photolysis quantum yield approaches or even falls below the lower range of literature values.

International audience; This work investigated the fate of nicotine (Nico) in aqueous solution upon reaction with singlet oxygen (1O2) and hydroxyl radical (HOradical dot). The second-order rate constants of Nico with 1O2 (View the MathML sourcekNico,O21 = (3.38 ± 0.14) × 106 M−1 s−1) and HOradical dot (kNico,radical dotOH = (1.08 ± 0.10) × 109 M−1 s−1) were determined using competition kinetics. Photochemical modelling showed that the reaction of Nico with HOradical dot would prevail over that with 1O2 in surface waters transformation pathway. The Nico photochemical half-life time could be accounted for by the two reactions. This value would vary in the month-year range depending on the environmental conditions: phototransformation would be favoured in shallow water poor in organic matter and rich in nitrate and nitrite. Irradiation experiments of Nico with nitrite suggested that transformation could not be accounted for by HOradical dot reaction alone. Indeed, a variable fraction of Nico transformation (30–80% depending on the conditions) would take place upon reaction with additional transients, photogenerated NOx being possible candidates. The chemical structures of the transformation intermediates were derived by means of HPLC-MS. The detection of nitroderivatives upon irradiation of Nico with nitrite suggests the involvement of nitrogen dioxide in the relevant photoprocesses.

Active fatty acid layers Saturated fatty acids are considered to be inert, but they can be surprisingly reactive when present as a coating at an air-water interface. Rossignol et al. show that nonanoic acid is photochemically active when it is present as a monolayer on a water surface (see the Perspective by Vaida). Fatty acids are ubiquitous in the environment, and their photochemical processing could have a substantial impact on local ozone and particle formation. Science , this issue p. 699 ; see also p. 650

International audience; 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.

International audience; The adsorption and photocatalytic degradation abilities of bismuth catalyst (BiOCl0.75I0.25) 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 (HO2/O2−). 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.

International audience; 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 NaClO4). 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 NaClO4). 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.

International audience; 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.