Iron-impregnated zeolite catalyst for efficient removal of micropollutants at very low concentration from Meurthe river

In this paper, for the first time, faujasite Y zeolite impregnated with iron (III) was employed as a catalyst to remove a real cocktail of micropollutants inside real water samples from the Meurthe river by the means of the heterogeneous photo-Fenton process. The catalyst was prepared by the wet impregnation method using iron (III) nitrate nonahydrate as iron precursor. First, an optimization of the process parameters was conducted using phenol as model macro-pollutant. The hydrogen peroxide concentration, the light wavelength (UV and visible) and intensity, the iron loading immobilized, as well as the pH of the solution were investigated. Complete photo-Fenton degradation of the contaminant was achieved using faujasite containing 20 wt.% of iron, under UV light, and in the presence of 0.007 mol/L of H₂O₂ at pH 5.5. In a second step, the optimized process was used with real water samples from the Meurthe river. Twenty-one micropollutants (endocrine disruptors, pharmaceuticals, personal care products, and perfluorinated compounds) including 17 pharmaceutical compounds were specifically targeted, detected, and quantified. All the initial concentrations remained in the range of nanogram per liter (0.8-88 ng/L). The majority of the micropollutants had a large affinity for the surface of the iron-impregnated faujasite. Our results emphasized the very good efficiency of the photo-Fenton process with a cocktail of a minimum of 21 micropollutants. Except for sulfamethoxazole and PFOA, the concentrations of all the other microcontaminants (bisphenol A, carbamazepine, carbamazepine-10,11-epoxide, clarithromycin, diclofenac, estrone, ibuprofen, ketoprofen, lidocaine, naproxen, PFOS, triclosan, etc.) became lower than the limit of quantification of the LC-MS/MS after 30 min or 6 h of photo-Fenton treatment depending on their initial concentrations. The photo-Fenton degradation of PFOA can be neglected. The photo-Fenton degradation of sulfamethoxazole obeys first-order kinetics in the presence of the cocktail of the other micropollutants.

Fate of inorganic nitrogen species under homogeneous Fenton combined with electro-oxidation/reduction treatments in synthetic solutions and reclaimed municipal wastewater

The fate of inorganic nitrogen species has been studied for the first time in electro-Fenton (EF) conditions in acid media. A redox cycle is first obtained and validated with a kinetic model in synthetic solution and highlights the removal of nitrite that is quickly oxidized into nitrate while the reduction conditions are sufficient to reduce nitrate into ammonium cation. However, NH₄⁺ and gaseous nitrogen accumulate in such solution. The study in reclaimed municipal wastewater emphasize the removal of NH₄⁺ with formation of chloramines in the presence of initial chloride ions, a species widely present in wastewater effluent. Contrastingly, NO₃^- remain constant all along the electrolysis even after 2.1 Ah L^-1. The oxidation conditions were not sufficient to produce perchlorate while chlorate accumulated in solution. Therefore, it limits the use of EF for direct use for drinking water purpose but could be considered as complementary treatment for wastewater reuse applications.

Population mobility and urban wastewater dynamics

Dynamic influent models, which have been proposed to test control strategies using virtual wastewater treatment plants, should be as realistic as possible. The number of inhabitants in the catchment at any given time and their ways of life are among the parameters affecting the quality of these models. Census data related to work and school commutes were used to evaluate the number of people present in a given urban area. Based on the example of a large urban catchment (Grand Nancy, France), the results show that a population increase of 30% could occur during working hours resulting from the imbalance between workers leaving and coming into the catchment. Combined with information related to the local way of life, variation in the population helps to explain changes in wastewater flow rate and pollution (carbon, nitrogen, phosphorus and heavy metals), which present several maxima reflecting daily activities, such as bladder voiding, meals, the use of washrooms, etc. However, no well-defined variation patterns for pH and conductivity, which are linked to the concentrations of anions and cations in the wastewater, were observed. Slight reductions (up to 10% on Sundays) in the flow and pollution load were observed on weekends as the commuter flow decreased. Census data proved to be efficient in helping to understand the daily pattern of urban wastewater characteristics.

Characterization by fluorescence of dissolved organic matter in rural drinking water storage tanks in Morocco

Water storage tanks, fed directly from the river through opened channels, are particular systems used for water supply in rural areas in Morocco. The stored water is used as drinking water by the surrounding population without any treatment. UV-visible spectroscopy and fluorescence spectroscopy (excitation-emission matrices and synchronous fluorescence) have been tested as rapid methods to assess the quality of the water stored in the reservoirs as well as along the river feeding them. Synchronous fluorescence spectra (SFS50), collected with a difference of 50 nm between excitation and emission wavelengths, revealed a high tryptophan-like fluorescence, indicative of a pollution induced by untreated domestic and/or farm wastewater. The best correlations were obtained between the total SFS50 fluorescence and dissolved organic carbon (DOC) and biological oxygen demand, showing that the contribution of humic-like fluorescent substances cannot be neglected to rapidly assess reservoir water quality in terms of DOC by fluorescence spectroscopy.

ZnO nanoparticles sensitized by CuInZn x S2+x quantum dots as highly efficient solar light driven photocatalysts

Alloyed CuInZn _x S_2+x (ZCIS) quantum dots (QDs) were successfully associated to ZnO nanoparticles by a thermal treatment at 400 °C for 15 min. The ZnO/ZCIS composite was characterized by TEM, SEM, XRD, XPS and UV-vis absorption spectroscopy. ZCIS QDs, with an average diameter of ≈4.5 nm, were found to be homogeneously distributed at the surface of ZnO nanoparticles. ZCIS-sensitized ZnO nanoparticles exhibit a high photocatalytic activity under simulated solar light irradiation for the degradation of Orange II dye (>95% degradation after 180 min of irradiation at an intensity of 5 mW/cm²). The heterojunction built between the ZnO nanoparticle and ZCIS QDs not only extends the light adsorption range by the photocatalyst but also acts to decrease electron/hole recombination. Interestingly, the ZnO/ZCIS composite was found to produce increased amounts of H₂O₂ and singlet oxygen ¹O₂ compared to ZnO, suggesting that these reactive oxygen species play a key role in the photodegradation mechanism. The activity of the ZnO/ZCIS composite is retained at over 90% of its original value after ten successive photocatalytic runs, indicating its high stability and its potential for practical photocatalytic applications.

Assessment of organic pollution of an industrial river by synchronous fluorescence and UV-vis spectroscopy: the Fensch River (NE France)

To rapidly monitor the surface water quality in terms of organic pollution of an industrial river undergoing restoration, optical methods (UV-visible spectrometry and fluorescence) were applied in parallel to classical physical-chemical analyses. UV-visible spectra were analyzed using the maximum of the second derivative at 225 nm (related to nitrates), specific absorbance at 254 nm (SUVA₂₅₄), and the spectral slope between 275 and 295 nm (S _275-295) (related to the aromaticity and molecular weight of dissolved organic carbon). The synchronous fluorescence spectra (wavelength difference = 50 nm) exhibited a high variability in the composition of dissolved organic material between the upstream and downstream sections and also versus time. The principal components analysis of the entire set of synchronous fluorescence spectra helped to define three river sections with different pollution characteristics. Spectral decomposition was applied to the two most upstream sections: five fluorophores, classical in rivers impacted by domestic sewage and related to protein-like (λ _ex = 280 nm) and humic-like fluorescence (M-type with λ _ex ≈ 305-310 nm and C-type with λ _ex ≥ 335 nm), were identified. The irregular shape of the synchronous fluorescence spectra in the most downstream section is likely due to organic pollutants of industrial origin; however, their variability and the complexity of the spectra did not allow the further elucidation of their nature.

Treatment of highly concentrated tannery wastewater using electrocoagulation: Influence of the quality of aluminium used for the electrode

This paper deals with the ability of electrocoagulation (EC) to remove simultaneously COD and chromium from a real chrome tanning wastewater in a batch stirred electro-coagulation cell provided with two aluminium-based electrodes (aluminium/copper/magnesium alloy and pure aluminium). Effects of operating time, current density and initial concentration of Cr(III) and COD have been investigated. The concentrations of pollutants have been successfully reduced to environmentally acceptable levels even if the concentrated effluent requires a long time of treatment of around 6h with a 400A/m(2) current density. The aluminium alloy was found to be more efficient than pure aluminium for removal of COD and chromium. Dilution of the waste has been tested for treatment: high abatement levels could be obtained with shorter time of treatment and lower current densities. Energy consumption of the electrocoagulation process was also discussed. The dilution by half of the concentrated waste leads to a higher abatement performance of both COD and chromium with the best energy efficiency.

Spectrophotometric characterization of dissolved organic matter in a rural watershed: the Madon River (N-E France)

In the last 20 years, increasing dissolved organic carbon (DOC) concentrations have been observed in several rivers and lakes in Europe. This increase has reduced the quality of the aquatic environment. In this study, UV-vis spectroscopy and synchronous fluorescence spectroscopy with a difference of 50 nm between the excitation and emission (SF50) were used to characterize the DOC in a rural river (Madon River). The specific absorbance index at 254 nm (SUVA254) which is related to the aromaticity of DOC was extracted from UV-vis spectra, whose maximum of the second derivative (occurring near 225 nm) is related to nitrates. SF50 spectra which are characterized by well-defined peaks indicated large spatial and temporal variations. Two methods were used to analyze and compare these spectra. The first method was based on the decomposition of the SF50 spectra into four Gauss functions: B1 (related to tryptophan-like fluorescence), B2 and B3 (related to humic substances), and B4 (related to chlorophyll-like substances). The second method was principal components analysis (PCA), which results yielded three principal components that accounted for 95% of the variance. Although PCA enables the consideration of the spectra without making assumptions regarding the number of fluorophores, the results from the decomposition in Gauss function were easier to interpret.

Photodegradation-based detection of fluorescent whitening agents in a mountain river

Fluorescent whitening agents (FWAs) are highly soluble and poorly biodegradable ingredients used in laundry detergents and in industries (paper, textile, plastic manufacturing). They are likely to pass through biological wastewater treatment systems. The presence of FWAs in a mountain river was detected by monitoring the decay of synchronous fluorescence intensity at λ(ex)=360 nm after exposing samples to ultraviolet (UV) light (365 nm), for mimicking sunlight, for 15 min. The method was first validated on four commercial FWAs (DAS-1, FB28, DMA-X and CBS-X) in different water matrices (deionized water and pristine river water in the presence of humic acid and dyes). A 40% decay was observed after 15 min for the least photosensitive FWA (CBS-X). A field application was then performed on samples collected along a mountain river in which impacts of FWAs from domestic sources (laundry greywater) and industrial sources (paper and textile mills) were suspected. Variations of fluorescence decay at λ(ex)=360 nm could be explained by these potential sources of pollution. It is suggested that the fluorescence decay at λ(ex)=280 nm also be considered as an indicator, as some FWAs can exhibit fluorescence at that excitation wavelength.

Studies on the dissolution of glucose in ionic liquids and extraction using the antisolvent method

Biomass, the fibrous material derived from plant cell walls, is a potentially clean and renewable nonfood feedstock for liquid fuel and chemical production in future biorefineries. The capability of ionic liquids to act as selective solvents and catalysts for biomass processing has already been proven. Thus, they are considered as an alternative to conventional solvents. Nevertheless, phase equilibria with biomass derived compounds is still lacking in the literature. To overcome the lack of experimental data on phase equilibria of biomass carbohydrates in ionic liquids, the solubility of d-glucose in four ionic liquids was measured within a temperature range from 283 to 373 K. Solubility data were successfully correlated with local composition thermodynamic models such as NRTL and UNIQUAC. In this work, the possibility of extracting glucose from these ionic liquids using the antisolvent method has been also evaluated. The parameters affecting the extraction process are the ionic liquid type, ethanol/ionic liquid ratio, temperature, water content, and time. Results indicate that ethanol can be successfully used as an antisolvent to separate glucose from ionic liquids.

Spectrophotometric characterization of human impacted surface waters in the Moselle watershed

In order to characterize the pollution discharged into the Moselle River and some of its tributaries, spectroscopic techniques, namely UV-vis spectroscopy and synchronous fluorescence spectroscopy, have been combined. UV-visible spectra were analysed using the maximum of the second derivative at 225 nm (related to nitrates), the SUVA254 and E2/E3 indices (related to the nature of organic matter). Synchronous fluorescence spectra (delta lambda = 50 nm) presented different shapes depending upon the type of pollution. The pollution results from anthropogenic activities: untreated domestic sewage due to misconnections in a periurban river, effluent from urban WWTPS, agricultural runoff (nitrates) in several streams, discharge from a paper mill (humic-like substances due to wood processing) and from steel mills (PAHs).