Combined of ozone/H2O2 with a falling film photoreactor.
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•Effect of several operating parameter on photocatalytic process were investigated.•A plausible removal pathway of flumequine ...in TiO2/UV system was proposed.•Photocatalytic removal of a mixture of antibiotics in wastewater was studied.•Removal efficiency is improved when adding CCl4.•Intensification of photocatalytic activity was investigated with adding O3 and H2O2.
This study focused on the removal of antibiotic by coupling of heterogeneous photocatalysis with ozonation and hydrogen peroxide. The main objective was to intensify the efficiency of photocatalytic activity for better and faster antibiotic elimination/mineralization in wastewater. To fulfill this purpose a photocatalytic process based on falling film reactor was designed and optimized. The effects of operating parameters such as wastewater flow rate in the falling film reactor, the presence of an oxidizing agent (H2O2 and O3), inlet concentrations, including catalyst dosage and light intensity were investigated and discussed. Experiments were mainly conducted with Flumequine and Clarithromycin. The first molecule (Flumequine) will serve as an example of fluoroquinolone antibiotics and the second (Clarithromycin) as an example of macrolide antibiotics. Experimentally, the results have shown interesting degradation and mineralization efficiency (on the order of 94% for degradation and 76% for mineralization). Evidence for redox catalysis was shown using X-ray photoelectron spectroscopy (XPS) before and after pollutant degradation. Moreover, special attention was also paid to identify the reaction products and the plausible degradation pathway during Flumequine degradation.
Activated carbon fiber cloths (ACFC) have shown promising results when applied to water treatment, especially for removing organic micropollutants such as pharmaceutical compounds. Nevertheless, ...further investigations are required, especially considering trace concentrations, which are found in current water treatment. Until now, most studies have been carried out at relatively high concentrations (mg L−1), since the experimental and analytical methodologies are more difficult and more expensive when dealing with lower concentrations (ng L−1). Therefore, the objective of this study was to validate an extrapolation procedure from high to low concentrations, for four compounds (Carbamazepine, Diclofenac, Caffeine and Acetaminophen). For this purpose, the reliability of the usual adsorption isotherm models, when extrapolated from high (mg L−1) to low concentrations (ng L−1), was assessed as well as the influence of numerous error functions. Some isotherm models (Freundlich, Toth) and error functions (RSS, ARE) show weaknesses to be used as an adsorption isotherms at low concentrations. However, from these results, the pairing of the Langmuir-Freundlich isotherm model with Marquardt's percent standard of deviation was evidenced as the best combination model, enabling the extrapolation of adsorption capacities by orders of magnitude.
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•Adsorption of pharmaceuticals onto ACFC was studied at trace concentration.•Both adsorption models and error functions were studied.•Adsorption capacities were extrapolated at trace concentrations using models.•The Langmuir-Freundlich model adjusted with a MPSD error was is the best choice.•The external mass transfer occurred outside the yarn of the ACFC.
► L–H approach to model the mass-transfer step on photocatalytic continuous reactor. ► Adsorption and kinetic constants depends only on the catalyst and the pollutant. ► Bimolecular L–H model to ...approach the effect of the relative humidity.
This study presents an experimental investigation of the photodegradation of two volatiles organic compounds (VOCs): Trimethylamine (TMA) and isovaleraldehyde (ISOV).
Experiments were performed by using an annular plug-flow reactor. The influence of the inlet concentration, flowrate and relative humidity (RH) on the conversion rate has been studied for the two VOCs. The increase of inlet concentration leads to a lower conversion rate due to the availability of the active sites. The flowrate increase also induces a lower degradation rate due to the shorter residence time. A kinetic model based on the Langmuir–Hinshelwood (L–H) approach and taking into account the mass transfer step was developed. This allows us to determine the adsorption and kinetic degradation constants with no influence of mass transfer.
This latter could be estimated by a semi-empirical correlation.
In small amounts, the presence of water vapor has a promoting effect on the degradation due to the formation of OH radicals. When the RH increases, the competition between water molecules and VOCs toward the active sites becomes predominant and the degradation rate decreases. A bimolecular L–H model, including mass transfer step, was developed. A good agreement with the experimental results was observed. Moreover by derivating the equation model, the optimum RH values could be estimated for the two pollutants. These RH values are equal to 40% for isovaleraldehyde and 25% for trimethylamine.
The present work involves the photocatalytic degradation of indole on a recirculating reactor. The effects of various factors as initial concentration of indole, catalyst-loading, pH, agitation and ...flow rate of the solution on the photodegradation were examined. The experimental results indicate that the optimal pH for indole elimination is about 6-7; the effect of catalyst loading shows an optimal value (1g/L) which is necessary to degrade indole; the increase of recirculating rate leads to a decrease of degradation rate due to the reduction of the residence time; the agitation speed has a slight influence on the indole degradation by improving the mass transfer step. Finally, L-H model was used to fit experimental results concerning the influence of experimental data. L-H model constants' were determined also.
Photocatalysis is a process that can mineralize organic pollutants such as pesticides released from agricultural activities. In this work we study the modelling of photocatalytic degradation of ...metolachlor and chlortoluron in a falling film closed loop step photoreactor. TiO
2 was coated on fiber which was deposited on the steps. The modelling was done by introducing an equivalent intermediate (EI) formed by the photo-oxidation of the initial compound to reproduce, partially, the competitive effect of the unknown by-products. The results obtained are satisfactory for describing the degradation kinetics but need improvement for the description of the mineralization. The model was used to simulate the degradation and the mineralization of a commercial pesticide solution (chlortoluron). The fitting gives interesting results but the description of the chemical pathway has to be refined.
Recently, environmental scientists have been focused their attention on the occurrence of emerging contaminants in water, such as disinfection by products (DBPs), including chlorophenols. These ...pollutants can be a public health problem due to their carcinogenic properties. In this work, ultra-high pressure liquid chromatography (UHPLC) coupled to a photodiode array detector (PDA) was used for the development of an analytical method capable of simultaneous identification and quantification of two chlorophenols namely, 2-chlorophenol and 2,4-dichlorophenol in water samples. In addition, a solid phase extraction (SPE) procedure for the extraction of these compounds was optimized. The chlorophenols were separated by an Acquity BEH C18 (100×2.1mm, 1.7μm) column with a mobile phase of acetonitrile/ultrapure water/formic acid (55/45/0.1, v/v/v). The flow rate of the mobile phase was 0.4mLmin−1. The optimized SPE–UHPLC/PDA technique was evaluated in terms of robustness, considering the enrichment factor for all of the studied chlorophenols. Linear calibration was obtained with correlation coefficients r2⩾0.998. Intra-day and inter-day precision was less than 5% and accuracy ranged from 99.95% to 103.32%, respectively. The obtained extraction recoveries were higher than 98%. The pre-concentration factor was 2.500 for the both analytes. Under optimized conditions, the detection limits of the overall SPE–UHPLC/PDA method were in the ngL−1 level. The excellent performance of the developed method, as well as the short analysis time makes it a promising analytical tool for the screening of chlorophenols in environmental water samples.
This study assessed the environmental footprint of emerging micropollutants in Cambodia and France. The aim was to develop and apply an analytical method to detect micropollutants in diverse water ...sources and climatic regions. Consequently, an analytical method, using online solid-phase extraction coupled with an ultra-performance liquid chromatography-tandem mass spectrometer (online-SPE-UPLC-MS/MS), was successfully developed and validated. This method permits the accurate and rapid multi-residual determination of 15 emerging micropollutants in water at low detection and quantification limits, around 10 ng.L−1 and 30 ng.L−1, respectively, within a total analytical run of seven minutes, including the equilibrium step. The findings revealed that no water body was free of micropollutants in any case of its sources (effluent wastewater, surface water, and even tap water). In surface water, 13 and 11 of the 15 target micropollutants were detected at least once in the Couesnon River (France) and Upper Mekong River (Cambodia), respectively. The concentration of micropollutant detected in Couesnon River ranged from 6–975.5 ng.L−1, with tramadol having the highest concentration. In the Upper Mekong River, the concentration detected ranged from 5–240 ng.L−1, with ketoprofen having the highest concentration. Caffeine was found in the highest concentration in the treated effluent of a Cambodian wastewater treatment plant (WWTP).
N-nitrosamines are a new class of emerging nitrogenous drinking water disinfection by-products. These compounds are probably carcinogenic which could seriously affect the safety of drinking water ...consumers. The aim of this study is to develop a simple, fast, and specific analytical method for the routine determination of low part per trillion levels of N-nitrosamines in waters. An ultra high pressure liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS) method was developed for the qualitative and quantitative analysis of N-nitrosamines in waters. N-nitrosamines were extracted, purified and concentrated from water samples in one step using a solid-phase extraction (SPE). The compounds were detected in multiple reaction monitoring via electrospray ionisation source with positive ionisation mode. To achieve symmetrical peak shapes and a short chromatographic analysis time, the mobile phase consisting of acetonitrile, water and formic acid (60:40:0.1, v/v/v) was used in the experiment. Chromatographic separation of N-nitrosamines was done in less than two minutes. All calibration curves had good linearity (r
2
≥ 0.9989). The intra- and inter-day precision of the assay ranged from 0.59% to 3.11% and accuracy ranged from 99.66% to 104.1%. The mean recoveries of N-nitrosamines in spiked water were 98%-101%. The reproducability was acceptable with relative standard deviations of less than 3.53%. The proposed method yielded detection limits very low which ranges from 0.04 to 0.16 ng L
−1
. Finally, the developed analytical method was successfully applied to the analysis of N-nitrosamines in natural water sample
Sequential and continuous configurations at pilot scale.
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•Butyraldehyde removal by plasma and photocatalysis is studied at pilot scale.•Effects of some operating parameters on ...performance of each process are tested.•A synergetic effect is confirmed by plasma DBD and photocatalysis combined.•Sequential and continuous configurations have been investigated.•Possible reasons of synergetic effect have been discussed.
This work investigated the performance of butyraldehyde decomposition with the help of dielectric barrier discharge (DBD) plasma coupled with photocatalysis (TiO2+UV) at room temperature. Effects of flow rate and initial butyraldehyde concentration on the decomposition and the distribution of byproducts were examined and discussed. The combination of these two technologies led to an enhancement of butyraldehyde abatement compared to the separate systems at pilot scale from 5 to 10m3h−1 of flowrate. The synergy factor due to combination processes ranged from 1.13 to 1.27. In the same way, CO2 selectivity was significantly improved when compared to the DBD plasma alone. In this research, DBD plasma system and an immobilized TiO2 photocatalysis system is sequentially combined to oxidize the target pollutant. Indeed, different ways to combine sequentially DBD plasma with photocatalytic materials are listed. Results at pilot scale showed that when photocatalyst is placed in the post discharge, the performance of sequential coupling plasma–photocatalyst process is improved in term of decomposition, by-products formation and energy yield.
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