The Chromatography analytical platform of the ICCF for water treatments: Metals and organic acids analyses by IC and MS

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Innovative depollution treatment using multi-valent iron species: from fundamental study to application in municipal wastewater

International audienceIn 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

Improving the characterization of dissolved organic carbon in cloud water: Amino acids and their impact on the oxidant capacity.

International audienceImproving our understanding of cloud chemistry depends on achieving better chemical characterization (90% of the organic carbon [OC] fraction remains uncharacterized) and, consequently, assessing the reactivity of this complex system. In this manuscript, we report for the first time the concentrations of 16 amino acids (AAs) in 25 cloud water samples. The concentrations of individual AAs ranged from a few nM up to ~2.0 μM, and the average contribution of AAs corresponded to 9.1% (4.4 to 21.6%) of the dissolved OC (DOC) concentration. Considering their occurrence and concentrations, AAs were expected to represent an important hydroxyl radical (HO•) sink in aqueous cloud samples. In this work, we estimated that approximately 17% (from 7 to 36%) of the hydroxyl radical-scavenging ability of the DOC could be attributed to the presence of AAs, whereas comparing the AAs suggested that an average of 51% (from 22 to 80%) of their reactivity with HO• could account for the presence of tryptophan. These results clearly demonstrate that the occurrence and reactivity of AAs must be considered to better estimate the chemical composition and oxidant capacity of the cloud aqueous phase

Determination of hydrophobicity and optical properties of soil humic acids isolated by different methods

International audienceHAs were extracted from the same chernozem soil sample by two commonly used methods: (i) extraction by 0.1 M NaOH followed by pre-decalcification using 0.1 M HCl -- the method, recommended by the International Humic Substances Society, and the HAs sample was named IHSS-HAs; and (ii) Kononova's method, where several treatments of soil by 0.1 M Na4P2O7 + 0.1 M NaOH were employed and the HAs were marked K1-HAs, K2-HAs and K3-HAs (corresponding to the first, second and third isolation cycle, respectively). Reversed-phase high performance liquid chromatography (RP HPLC) with stepwise and linear gradients of methanol was used to reveal hydrophobicity differences in isolated HAs. Independent on the method used, after the first extraction IHSS-HAs and K1-HAs had a similar hydrophobicity, and varied in the order K3-HAs > K2-HAs > K1-HAs in Kononova's method. The absorption spectra of extracted HAs were featureless, but the negative correlation of specific absorption at 280 nm and E4/E6 ratio with hydrophobicity was found. The data point out that the hydrophobicity of HAs may be greatly influenced by their isolation procedure. Extraction protocol may induce changes in the transport of organic pollutants and affected drawn conclusions

Photochemical behaviour of triclosan in aqueous solutions: Kinetic and analytical studies

International audienceThe mechanism of the direct photolysis of the anti-microbial triclosan in aqueous solutions was investigated by using steady state and laser flash photolysis. Quantum yields were determined for the disappearance of triclosan and formation of chloride anions in steady state irradiations in the absence and in the presence of oxygen as well as a function of pH. The photoreactivity was found to be efficient with the anionic form and in the absence of oxygen. Following laser flash photolysis (226 nm), three transients were found (triclosan triplet state, solvated electron and phenoxyl radical). Several primary and secondary stable photoproducts were elucidated by means of LC/MS/MS data. They were found to arise from four main photochemical processes: isomerisation, cyclization (leading to the formation of dioxin derivatives), dimerisation of the phenolic moiety and hydrolysis. The ionic chromatography showed that the loss of chloride anion in triclosan phototransformation represents an important degradation pathway. The formation of oligomeric products was also observed for prolonged irradiation time. A detailed mechanism for the formation of the primary products is proposed and discussed. The very important photocyclization reaction is more likely involving the triplet state pathway and the homolytic dissociation of the ether bridge occurs from the singlet excited state pathway

Effect of UVC pre-irradiation on the Suwannee river Natural Organic Matter (SRNOM) photooxidant properties

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Molecular Size Distribution of Fluorophores in Aquatic Natural Organic Matter: Application of HPSEC with Multi-Wavelength Absorption and Fluorescence Detection Following LPSEC-PAGE Fractionation

International audienceAnalytical high performance size exclusion liquid chromatography (HPSEC) with multiwavelength absorbance and fluorescence detections was used for the analysis of molecular size distribution and optical properties of dissolved natural organic matter. Experiments were conducted on Suwannee River organic matter (SRNOM) and its fractions A, B, C+D preliminary obtained by combination of preparative low pressure size exclusion chromatography and polyacrylamide gel electrophoresis (LPSEC-PAGE) and purified by dialysis on membrane with nominal cutoff 10 kDa, the fractions molecular size varied in order A > B > C + D > 10 kDa. The multistep fractionation of SRNOM enabled the size-separation of at least five types of humic-like fluorophores within NOM showing emission maxima at 465, 450, 435, 420, and 405 nm. The decrease of the humic-like emission maxima paralleled the decrease of the nominal molecular size of fluorescent SRNOM. The protein-like fluorescence was split into tyrosine-like and tryptophan-like fluorophores and only detected in fractions A and B. This work provides new data on the optical properties of size-fractionated NOM, which consistent with the formation of supramolecular NOM assemblies, likely controlled by association of low-molecular size components. It is clearly observed for the high molecular size fraction A, containing free amino acids or short peptides. The combination of several different fractionation procedures is very useful for obtaining less complex NOM compounds and understanding the NOM function in the environment

Analysis of electrophoretic soil humic acids fractions by reversed-phase high performance liquid chromatography with on-line absorbance and fluorescence detection

International audienceA combination of reversed-phase high performance liquid chromatography (RP HPLC) with on-line absorbance and fluorescence detection was used for analysis of chernozem soil humic acids (HAs) and their fractions A, B and C + D with different electrophoretic mobility (EM) and molecular size (MS). Samples were injected onto the column at the identical volume and absorbance. All chromatograms exhibit the resolution of seven peaks. The estimation of relative recovery of HAs and fractions from the reverse-phase column has been done. High MS fraction A, which possesses the low EM, is essentially more hydrophobic (73% of the fraction amount remained adsorbed on the column) and aliphatic than medium MS and EM fraction B (33% of the fraction amount remained adsorbed on the column). The most hydrophilic and aromatic properties belong to low MS fraction C + D, which possess the highest EM and practically was not adsorbed on the column. The hydrophobicity of the bulk HAs lies within the range of fractions hydrophobicity. The absorption spectra of bulk HAs, electrophoretic fractions A, B, C + D and corresponding RP HPLC peaks were featureless but had differences in the values of absorbance ratio at 300 and 400 nm (A3/A4). For fractions A and B this ratio gradually decreased from peak 1 to 7 (from 3.05 to 2.80 and 3.00 to 2.40, respectively). This trend was less pronounced in HAs and practically absent in fraction C + D, where ratio A3/A4 varied within a small range. The strong relationship between fluorescence properties, EM, MS, polarity and aliphaticity/aromaticity of HAs fractions was found. Humic and proteinlike fluorescence had different polarity nature. The protein-like fluorescence is located in humic material which irreversibly adsorbed on the reverse-phase column and not subjected to RP HPLC characterization. The humic-like fluorescence at Ex/Em 270/450 nm is mostly located in the hydrophilic peak of low MS fraction C + D. Taking into account that high MS fraction A consisted mainly of aliphatic components it is reasonable to suggest that these associations are capable of organizing into micellar structures. These data could be of great environmental importance, because the different fractions might reflect different soil physical-chemical properties

Synergistic degradation of bisphenol A in heterogeneous Fenton and photo-Fenton systems catalyzed by graphitized carbon-nano zero valent iron

Fenton-like processes have gained widespread acceptance due to their high oxidative potential and environmental compatibility. In this study, a composite of graphitized carbon and nZVI (GC-nZVI) was synthesized and applied toward the degradation of bisphenol A (BPA) in water. The morphological structure and stability of GC-nZVI were evaluated using different characterization techniques including X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Our results showed that the catalytic graphitization of carbon occurred simultaneously with the carbothermal reduction of iron oxide, and ZVI was distributed uniformly on the carbon material. Excluding the adsorption effect, there was almost no degradation of BPA using GC-nZVI only. However, in the presence of H2O2 and UVA radiation, BPA was rapidly degraded. The synergistic effect of the photo-Fenton process carried out in the presence of H2O2 showed that 90% of BPA degradation was obtained after 60 min using only 50 mg L–1 of GC-nZVI and 0.5 mM of H2O2 at pH 6. The generation of HO• has been demonstrated using chemical competition experiments and the photo-Fenton process, which could eliminate 66% of BPA within 15 min under the same conditions. Finally, recycling experiments have shown that after three cycles of BPA and H2O2 addition, a degradation efficiency of 71% was achieved over 60 min. The GC-nZVI/H2O2/UVA system demonstrated great potential for advanced oxidation processes and had good application prospects in the treatment of actual wastewater

RP-HPLC and spectroscopic characterization of Suwannee River water NOM after concentrated urea treatment and dialysis

International audienceSuwannee River natural organic matter (SRNOM) was treated by 7 M urea and then purified by dialysis on 10 kDa membrane. The untreated SRNOM and treated (USRNOM) samples were examined using UV–visible and fluorescence spectroscopies and reversed-phase high-performance liquid chromatography (RP-HPLC) with online absorbance and fluorescence detection. USRNOM was 1.5-fold more absorbing at 280 nm than SRNOM and four fold less fluorescent than SRNOM upon excitation at 270 nm. RP-HPLC analyses of the two samples revealed that USRNOM was somewhat more hydrophobic than SRNOM and both samples contained at least two groups of HS-like fluorophores with different hydrophobicity and protein-like fluorophore(s). Data indicate that protein-like fluorophores were not lost during dialysis. They showed hydrophobic properties and seemed highly fluorescent. HS-like and protein-like fluorophores from water NOM could be successfully separated by RP-HPLC. This raises the prospect of their further research and identification and could be significant for future NOM chemical structure characterization