A comparative study of ceramic nanoparticles synthesized for antibiotic removal: catalysis characterization and photocatalytic performance modeling

International audienceThe heterogeneous photocatalysis process has been known to provide significant levels of degradation and mineralization of emerging contaminants including antibiotics. For that, nanoparticle CuCr(2)O(4) (CCO) ceramics were successfully prepared via sol-gel (SG) and co-precipitation (CP) methods to obtain spinel with desired structural features and properties and also to improve the photocatalytic performances. The CCO crystallite phase was produced at 750 °C all ceramics, disregarding the synthesis route. CCO physical and chemical properties were checked by X-ray diffraction (XRD) with Rietveld refinement, Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), and diffuse reflectance solid (DRS). The XRD patterns demonstrated that the synthesized catalysts displayed a small crystallite size between 17.45 and 26.24 nm for SG and 20.97 and 36.86 nm for the CCO(CP) samples. The observation by SEM and TEM of the nanopowders showed a typical morphology with comparable particle sizes for both synthesized routes (20-30 nm). SG agglomeration rates were higher, and particles stick together more efficiently considering the CP method, while the CCO(CP) method led to a more significant porosity. Their photocatalytic and adsorption performances were examined for cefaclor (CFC) removal chosen as a target pharmaceutical contaminant in water. The results obtained by the methods differed since nanoparticles prepared by SG led to high photocatalytic activity. In contrast, a high CFC adsorption was observed for those prepared via the CP method, and that agreed with the findings of the characterization analysis. The kinetics of the adsorption process was found to follow the pseudo-second-order rate law. In contrast, the data of the photodegradation process were further found to comply with the Lagergren kinetic law. Nevertheless, the global reaction rate is probably controlled by the intra-particular diffusion of CFC, regardless of the elimination process

Optimized removal of chloroform and DMDS using synthetic zeolite (Na-P1) and activated carbon composite

International audienceIn this study, pure synthesised zeolite (Na-P1) and synthetic activated carbon were investigated as adsorbents for volatile organic compounds (VOCs) such chloroform and dimethyl disulfide. Here, Na-P1 was synthesised from Illito-Kaolinitic clay of Tejra region (South-east of Tunisia), while a novel activated carbon was synthesised from wooden tongue depressor waste collected from hospitals during the first wave of covid-19 pandemic. The mineralogical properties of raw clay and the synthesized materials were determined using X-ray diffraction (XRD) and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Morphological characteristics were determined using scanning electron microscopy (SEM), which revealed a high degree of particle size uniformity in Na-P1 zeolite and a well-developed, clearly defined structure in activated carbon. The Na-P1 zeolite shows a high-cation exchange capacity, reaching 279 meq/100 g. BET (N2 adsorption-desorption) analysis reveal a high specific surface area (1511.842 m2/g) and a mean pore volume equal to 0.621 cc/g. A fraction of the synthesised activated carbon has been added to Na-P1 zeolite which enhanced its misopores characteristics, thus increasing its adsorption capacity. Additionally, Kinetic model data are well fitted to pseudo-second order. The Langmuir model provides the best fit for isothermal adsorption equilibrium data, and according to this model, the Na-P1-activated carbon composite demonstrated a maximum adsorption capacity of 54.13 mg/g for chloroform and 28.16 mg/g for dimethyl disulfide

New UV-LED frontal flow photocatalytic reactor for VOCs treatment: Compactness, intensification and optimization studies

International audienceThis study investigates and provides a solution for optimizing the photocatalytic treatment of toxic gases based on the use of TiO2 media deposited on luminous textiles. The target was the cyclohexane referent for the type A gas filtration tests. The photocatalytic supports were characterized by scanning electron microscopy. Then, the experiments conducted on a batch reactor showed that the TiO2-coated optical fiber media (in situ illumination configuration) performs better than conventional configuration (cellulosic TiO2 with external radiation "UV lamp". To take advantage of the new optical fiber media configuration, an intensification study was carried out by increasing the amount of TiO2 in the media and UV intensities of LED. Increasing these two parameters leads to an approximately fourfold increase in the degradation rate. The continuous treatment allowed the study to highlight the efficiency of the new configuration of the front flow reactors developed (PFR-LED) compared to the conventional configuration. This increased efficiency is demonstrated by the fourfold increase in the specific degradation rate of the optimized PFR-LED compared to the conventional reactor. The performance evaluation of the compact and optimized configurations of the frontal flow reactor (PFR-LED Optimized) aimed to highlight the influence of the inlet concentration under different flow rates. Furthermore, the effect of the number of optical fiber supports shows that the degradation rate and selectivity are enhanced. The results were obtained using four photocatalytic media (4OF/4UV-LED) for 1.19 mmol.m and#xfffd; 3 of cyclohexane input concentration at 18 L. min-1 of flow rate under optimal humidity conditions (38 %), constituting the ultimate rate of CO2 selectivity achieved (31 %) for an abatement of 59 %. This global investigation has allowed for the design of a new version of a compact reactor.This reactor provides an economical and efficient way to eliminate gaseous pollutants, which clearly meets the main aims of the UN Sustainable Development Goals (UN SDGs)

Gaseous ethylbenzene removal by photocatalytic TiO(2) nanoparticles immobilized on glass fiber tissue under real conditions: evaluation of reactive oxygen species contribution to the photocatalytic process

International audiencePhotocatalytic oxidation (PCO) using a TiO(2) catalyst is an effective technique to remove gaseous volatile organic compounds (VOCs). Herein, a lab-scale continuous reactor is used to investigate the photocatalytic performance toward ethylbenzene (EB) vapor removal over TiO(2) nanoparticles immobilized on glass fiber tissue. The role of the reactive species in the removal of EB and the degradation pathway were studied. Firstly, the effect of key operating parameters such as EB concentration (13, 26, 60 mg/m(3)), relative humidity levels (From 5 to 80%), gas carrier composition (dry air + EB, O(2) + EB and N(2) + EB) and ultraviolet (UV) radiation wavelength (UV-A (365 nm), UV-C (254 nm)) were explored. Then, using superoxide dismutase and tert-butanol as trapping agents, the real contribution of superoxide radical anion (O(2)(.-)) and hydroxyl radicals (OH(.)) to EB removal was quantified. The results show that (i) small water vapor content enhances the EB degradation; (ii) the reaction atmosphere plays an important role in the photocatalytic process; and (iii) oxygen atmosphere/UV-C radiation shows the highest EB degradation percentage. The use of radical scavengers confirms the major contribution of the hydroxyl radical to the photocatalytic mechanism with 75% versus 25% for superoxide radical anion

Smart design for CBRN protection by coupling adsorption and photocatalysis: Regeneration adsorbent efficiency-CWAs' continuous purification

International audienceThis investigation and optimization of the adsorption and photocatalysis coupling process for treating chemical warfare agents (CWAs) were performed with a compact cartridge based on activated carbon felt (AF) and TiO2 photocatalyst deposited on luminous textiles. The target pollutants were simulants of the chemical warfare agent (yperite), methyl salicylate, diethyl sulfur (a simulant of sulfur mustard gas), and cyclohexane, which is the benchmark for type A gas filtration tests. To take better advantage of this new configuration, an optimization of the photocatalytic process was highlighted with an improvement of the regeneration process by implementing the integrated compactness of desorption by the Joule effect (in situ). In the case of methyl salicylate treatment, the recovery of the adsorption capacity of the AF were about 95% and a working time of 85% compared to initial adsorbent performance. For the second cycle regeneration, the recovered adsorption capacity was about 88% compared to initial capacity. We note also that the working time decrease by 15% for each regeneration step. The evaluation of the new coupling configuration aimed at highlighting the influence of a sulfur compound was encouraging, with a regeneration rate of the adsorbent of about 80%. Compared to MS, the regeneration seems to be more difficult. This is due to by-products (SO2, MSH) formation which is highlighted by the degradation pathway proposed. The removal efficiency of the coupling system (UV-LED/AF) under continuous process, was equal to 36%. This leads an increase in filter working time of 50 min over that of a conventional adsorption process. Special attention was paid to validating the coupling system performance in real conditions. The system was placed on a humanlike seated thermal manikin used to simulate an occupant of a chamber of 30 m3 with the realistic condition of applying chemical, biological, radiological, and nuclear (CBRN) agent protection. The time protection was 60 and 30 min for respective concentrations of about 150 and 300 mg.m and#xe213; 3.This global investigation addressed how to overcome the scientific barriers to designing a compact, self-contained filtration cartridge for personal protection in CBRN emergency response and management in accor-dance with the United Nations Sustainable Development Goals (SDGs)

Continuous air purification by front flow photocatalytic reactor: Modelling of the influence of mass transfer step under simulated real conditions

International audienceIn this work, a solution for the treatment of toxic gases based on a photocatalytic process using TiO(2) coated on a cellulosic support, has been investigated. Here, cyclohexane was chosen as the reference for testing its removal efficiency via a continuous front flow reactor as type A anti-gas filters. The photocatalytic support was firstly characterized by EDX, to confirm its elemental composition. Then, the experiments were carried out, starting with a batch reactor in order to evaluate the degradation efficiency of the photocatalytic media, as well as the monitoring of the photocatalytic process which allowed the establishing of a carbon mass balance corresponding to the stoichiometric number of our target pollutant. The transition to a continuous treatment with a front flow reactor aims to highlight the influence of the input concentration (0.29-1.78 mM m(-3)) under different flow rates (12, 18 and 36 L min(-1)). The relative humidity effect was also investigated (from 5 to 90% of humidity) where an optimum rate was obtained around 35-45%. In addition, the mineralization rate was monitored. The major rates obtained were for a cyclohexane input concentration of 0.29 mM m(-3) in wet condition (38%) at an air flow rate of 18 L min(-1), where the CO(2) selectivity reached 77% for an abatement of 62%. In order to understand the limiting steps of the photocatalytic process, a model considering the reactor geometry and the hydraulic flow was developed. The obtained results showed that the mass transfer must be considered in the photocatalytic process for a continuous treatment. The Langmuir-Hinshelwood bimolecular model was also developed to represent the influence of the humidity

Advanced Photocatalytic Treatment of Wastewater Using Immobilized Titanium Dioxide as a Photocatalyst in a Pilot-Scale Reactor: Process Intensification

International audienceIn many nations, particularly those experiencing water scarcity, novel approaches are being applied to clean wastewater. Heterogeneous photocatalysis is the most widely used of these approaches because it entails the decomposition of organic molecules into water and carbon dioxide, which is a more ecologically benign process. In our study, we studied the photocatalytic degradation process on the effluent flumequine. This treatment is made through a solar pilot reactor in the presence of immobilized titanium dioxide with three light intensities and two types of water as solvents. A variety of factors that might influence the rate of deterioration, such as flow rate, light intensity, and initial concentration, have been investigated. The maximal degradation of flumequine was achieved at more than 90% after 2.5 h under optimal conditions (an initial concentration of 5 mg/L, three lamp light intensities, and a flow rate of 29 L/h). By combining the oxidized agent H2O2 with this process, the photocatalytic activity was improved further to 97% under the same conditions. The mineralization of this product has also been tested using total organic carbon (TOC) analysis. A high mineralization rate has been recorded at around 50% for a high initial concentration (20 mg/L) at a flow rate of 126 L/h. The results demonstrated the highly effective removal of flumequine and the efficacy of this photocatalytic system

Structural and electrochemical characterizations of Bi12CoO20 sillenite crystals: degradation and reduction of organic and inorganic pollutants

International audienceThe present contribution is to synthesize and characterize a new material photocatalyst. It also explores the possibility of using it to remove organic and inorganic pollutants in water. In this context, the sillenite Bi12CoO20 (BCO) in pure phase was synthesized by the combustion sol-gel method. The phase was identified by X-ray diffraction (XRD) then it was refined in the cubic symmetry in the space group (I23 N degrees 197) using the Rietveld refinement method; the lattice constant was accurately determined. A direct optical bandgap of 2.56 eV was evaluated using the UV-Visible diffuse reflectance. The electrochemical properties were investigated for the first time. A flat band potential of E-fb = 0.62 V-SCE was found with a p-type character; the hole density N-d = 54.2 x 10(17) cm(-3) extends the depletion width at 27 nm. The photocatalytic activity of BCO nanoparticles was tested to eliminate organic and inorganic pollutants namely the Basic red 46 (BR46) and hexavalent chromium Cr(VI). An acceptable rate was observed within 3 h for both contaminants

Synthesis and Characterization of TiO(2) Nanotubes (TiO(2)-NTs) with Ag Silver Nanoparticles (Ag-NPs): Photocatalytic Performance for Wastewater Treatment under Visible Light

International audienceIn this work, we present the influence of the decoration of TiO(2) nanotubes (TiO(2)-NTs) with Ag silver nanoparticles (Ag-NPs) on the photocatalysis of emerging pollutants such as the antibiotic diclofenac sodium. The Ag-NPs were loaded onto the TiO(2)-NTs by the anodization of metallic titanium foils. Diclofenac sodium is an emerging pollutant target of the pharmaceutical industry because of its negative environmental impact (high toxicity and confirmed carcinogenicity). The obtained Ag-NP/TiO(2)-NT nanocomposites were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), transmission spectroscopy (TEM), and X-ray photoelectron spectroscopy (XPS). In order to study the photocatalytic behavior of Ag-NPs/TiO(2)-NTs with visible cold LEDs, the possible photocatalytic mechanism of antibiotic degradation with reactive species (O(2)°(-) and OH°) was detailed. Moreover, the Langmuir-Hinshelwood model was used to correlate the experimental results with the optimized catalyst. Likewise, reuse tests showed the chemical stability of the catalyst

Mineralization and photodegradation of oxytetracycline by UV/H2O2/Fe2+ and UV/PS/Fe2+ process: quantification of radicals

International audienceIn this study, different oxidation processes UVA-365 nm (photolysis), UV-A/H2O2, UV-A/H2O2/Fe2+, UV-A/S2O8, and UV-A/S2O8/Fe2+ were investigated to compare removal rates efficiencies of Oxytetracycline (OTC). The role of the initial concentration of oxidants, as well as their inhibitory threshold regarding degradation and mineralization of OTC, was investigated at different pH. It was found that the initial pH solution had an important role in the photolysis of OTC, since in alkaline solutions, the degradation rate was faster than in acidic solutions, but in terms of mineralization yield, it did not exceed 3%. The addition of oxidants (H2O2, S2O8) had an impact on the mineralization, which reached 50% for the UV/S2O8 system. To improve mineralization, ferrous ions were added to UVA/oxidants, leading to 85% mineralization. Quantification of the main radicals involved in the oxidation process can help in the understanding of the free radical mechanism and their respective contributions to the degradation of OTC. The ability of Dimethylsulfoxide (DMSO) to act as a free radical scavenger was considered in UV/H2O2 and UV/H2O2/Fe2+ systems. The hydroxyl radicals can react directly with DMSO to produce a stable intermediate, methanesulfonate. Otherwise, isopropanol, tert-butanol and 1,4, benzoquinone were used as indirect methods to catch and to quantify the main radicals generated during UV/S2O8 and UV/S2O8/Fe(2+)processes. Finally, the results allowed to quantify the contributions of each radical involved in photo-oxidation for both systems, UV/H2O2 and UV/ S2O8