Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO₂

[Abstract] Photocatalyzed degradation of phenol in aqueous solution over surface impregnated TiO₂ (M = Cu, Cr, V) under UV-Vis (366 nm) and UV (254 nm) irradiation is described. Nanosized photocatalyts were prepared from TiO₂-P25 by wet impregnation, and characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, Raman spectroscopy, and adsorption studies. No oxide phases of the metal dopants were found, although their presence in the TiO₂-P25 lattice induces tensile strain in Cu-impregnated TiO₂-P25, whereas compressive strain in Cr- and V-impregnated TiO₂-P25. Experimental evidences support chemical and mechanical stability of the photocatalysts. Type IV N₂ adsorption–desorption isotherms, with a small H3 loop near the maximum relative pressure were observed. Metal surface impregnated photocatalysts are mesoporous with a similar surface roughness, and a narrow pore distribution around ca. 25 Å. They were chemically stable, showing no metal lixiviation. Their photocatalytic activity was followed by UV-Vis spectroscopy and HPLC–UV. A first order kinetic model appropriately fitted the experimental data. The fastest phenol degradation was obtained with M (0.1%)/TiO₂-P25, the reactivity order being Cu > V >> Cr > TiO₂-P25 under 366 nm irradiation, while TiO₂-P25 > Cu > V > Cr, when using 254 nm radiation. TOC removal under 366 nm irradiation for 300 min showed almost quantitative mineralization for all tested materials, while 254 nm irradiation for 60 min led to maximal TOC removal (ca. 30%). Photoproducts and intermediate photoproducts were identified by HPLC–MS, and appropriate reaction pathways are proposed. The energy efficiency of the process was analysed, showing UV lamps are superior to UVA lamps, and that the efficiency of the surface impregnated catalyst varies in the order Cu > V > Cr.This research was partially supported by the Group of Chemical Reactivity & Photoreactivity at University and funded by the Spanish Ministerio de Economía y Competitividad through project CTQ2015-71238-R (MINECO/FEDER), and the regional government Xunta de Galicia (Project Grupo Potencial Crecemento (GPC) ED431B 2017/59), respectivelyXunta de Galicia; ED431B 2017/5

Cobalt Impregnation on Titania Photocatalysts Enhances Vis Phenol Photodegradation

This article belongs to the Special Issue Advanced Catalysts for Energy and Environmental Applications[Abstract] One of the main challenges of photocatalysis is to find a stable and effective photocatalyst, that is active and effective under sunlight. Here, we discuss the photocatalytic degradation of phenol as a model pollutant in aqueous solution using NUV-Vis (>366 nm) and UV (254 nm) in the presence of TiO2-P25 impregnated with different concentrations of Co (0.1%, 0.3%, 0.5%, and 1%). The modification of the surface of the photocatalyst was performed by wet impregnation, and the obtained solids were characterized using X-ray diffraction, XPS, SEM, EDS, TEM, N2 physisorption, Raman and UV-Vis DRS, which revealed the structural and morphological stability of the modified material. BET isotherms are type IV, with slit-shaped pores formed by nonrigid aggregate particles and no pore networks and a small H3 loop near the maximum relative pressure. The doped samples show increased crystallite sizes and a lower band gap, extending visible light harvesting. All prepared catalysts showed band gaps in the interval 2.3–2.5 eV. The photocatalytic degradation of aqueous phenol over TiO2-P25 and Co(X%)/TiO2 was monitored using UV-Vis spectrophotometry: Co(0.1%)/TiO2 being the most effective with NUV-Vis irradiation. TOC analysis showed ca. 96% TOC removal with NUV-Vis radiation, while only 23% removal under UV radiation.This research received support through grant TED2021-132667B-I00, funded by the EU NextGenerationEU/PRTR through project MCIN/AEI/10.13039/501100011033. Financial support was also provided by the regional government Xunta de Galicia through project GPC/ED431B 2020/52. S.B. thanks the KA-107 grant received from the EU through the Erasmus+ program for a research stay at UDCXunta de Galicia; ED431B 2020/5

The Synergistic Effect of Chloride Ion and 1,5-Diaminonaphthalene on the Corrosion Inhibition of Mild Steel in 0.5 M Sulfuric Acid: Experimental and Theoretical Insights

International audienceThe inhibition efficiency of 1,5-Diaminonaphthalene (1,5DNA) compound was studied by itself as well as in a mixture that included sodium chloride (NaCl), noted [1.5DNA][Cl−], for mild steel in 0.5 M sulfuric acid. Gravimetric, electrochemical techniques and computational chemistry calculations were utilized for the assessment of corrosion inhibition efficiency and explanation of the mechanism involved during the corrosion inhibition process. The results show that inhibition efficiencies on mild steel increase with increase in concentration of the inhibitor and enhancement in inhibition efficiency was observed on addition of sodium chloride due to synergism. This inhibition has been attributed to the stabilization of adsorbed inhibitor film and, consequently, increasing its inhibitive properties. The [1.5DNA][Cl−] acts as mixed type inhibitor and the Nyquist curves show that with the increase in the concentration, the charge transfer resistance Rct increased. In addition, [1.5DNA][Cl−] obeyed Langmuir monolayer adsorption isotherm. Moreover, Molecular Dynamic Simulations and DFT calculations showed that [1.5DNA][Cl−] owned a higher adsorption ability

Enhanced Photocatalytic Degradation of the Imidazolinone Herbicide Imazapyr upon UV/Vis Irradiation in the Presence of CaxMnOy-TiO2 Hetero-Nanostructures: Degradation Pathways and Reaction Intermediates

[Abstract] The determination of reaction pathways and identification of products of pollutants degradation is central to photocatalytic environmental remediation. This work focuses on the photocatalytic degradation of the herbicide Imazapyr (2-(4-methyl-5-oxo-4-propan-2-yl-1H-imidazol-2-yl) pyridine-3-carboxylic acid) under UV-Vis and visible-only irradiation of aqueous suspensions of CaᵪMnOᵧ-TiO₂, and on the identification of the corresponding degradation pathways and reaction intermediates. CaᵪMnOᵧ-TiO₂ was formed by mixing CaᵪMnOᵧ and TiO₂ by mechanical grinding followed by annealing at 500 °C. A complete structural characterization of CaᵪMnOᵧ-TiO₂ was carried out. The photocatalytic activity of the hetero-nanostructures was determined using phenol and Imazapyr herbicide as model pollutants in a stirred tank reactor under UV-Vis and visible-only irradiation. Using equivalent loadings, CaᵪMnOᵧ-TiO₂ showed a higher rate (10.6 μM·h⁻¹) as compared to unmodified TiO₂ (7.4 μM·h⁻¹) for Imazapyr degradation under UV-Vis irradiation. The mineralization rate was 4.07 μM·h⁻¹ for CaᵪMnOᵧ-TiO₂ and 1.21 μM·h⁻¹ for TiO₂. In the CaᵪMnOᵧ-TiO₂ system, the concentration of intermediate products reached a maximum at 180 min of irradiation that then decreased to a half in 120 min. For unmodified TiO₂, the intermediates continuously increased with irradiation time with no decrease observed in their concentration. The enhanced efficiency of the CaᵪMnOᵧ-TiO₂ for the complete degradation of the Imazapyr and intermediates is attributed to an increased adsorption of polar species on the surface of CaᵪMnOᵧ. Based on LC-MS, photocatalytic degradation pathways for Imazapyr under UV-Vis irradiation have been proposed. Some photocatalytic degradation was obtained under visible-only irradiation for CaᵪMnOᵧ-TiO₂. Hydroxyl radicals were found to be main reactive oxygen species responsible for the photocatalytic degradation through radical scavenger investigations.This research received external funding from the British Council under the STREAM-MENA Institutional Links Scheme Grant number 278072873. This is a collaboration between Ulster University (UK), Technion Institute (Israel) and Rabat University (Morocco). MC acknowledges support from Ministerio de Economía y Competitividad (Spain) through project CTQ2015-71238-R (MINECO/FEDER). AS would like to acknowledge the financial support received from Ulster University (UK) through the VCRS scholarship. PS would like to acknowledge funding from Invest Northern Ireland for the BioDevices projectBritish Council; 27807287

Mixed α-Fe2O3/Bi2WO6 oxides for photoassisted hetero-Fenton degradation of Methyl Orange and Phenol

Mixed oxides, α-Fe2O3/Bi2WO6, were prepared using a mechanical mixing procedure by adding to the Bi2WO6 previously obtained by hydrothermal method the corresponding amount of a prepared α-Fe2O3, the latter obtained by thermal decomposition of Fe(NO3)∙9H2O. The physicochemical surface, structural, morphological characteristics and optical properties of the samples, single and mixed, were determined by BET, XRD, FE-SEM, XPS and UV–vis diffuse reflectance spectroscopy. UV–vis diffuse reflectance spectra showed that incorporating a 5%wt. of α-Fe2O3 to the corresponding amount of Bi2WO6 sample broadened the visible light absorption of Bi2WO6 as expected. The photocatalytic activity, of single and mixed catalysts, to degrade a selected dye such as Methyl Orange (MO) as well as the transparent substrate Phenol (Ph) was studied, in aqueous medium (pH ≈ 5.5) under UV and sun-like illumination conditions in the absence and presence of H2O2. In the present study the use of a α-Fe2O3-Bi2WO6/H2O2 system demonstrate much higher photocatalytic efficiency to degrade both MO and Ph than pristine Bi2WO6or α-Fe2O3, single or mixed. Using the system α-Fe2O3-Bi2WO6/H2O2, around 85% of MO was degraded in 60 min under sun-like illumination whereas 100% was degraded in 60 min under UV-illumination. However, just around 30% of Ph was degraded in 120 min in the α-Fe2O3-Bi2WO6/H2O2 system under sun-like illumination whereas around a 95% was degraded in 90 min under UV-illumination. Under UV-illumination, the generation of hydroxyl radicals is favorable; whereas under sun-like illumination, only the small fraction of the UV can produces the radical dotOH. Under illumination, the H2O2 could react with photoinduced electrons from the photocatalysts leading to the production of hydroxyl radicals (radical dotOH).Ministerio de Economía y Competitividad CTQ2015-64664- C2-2-

Natural resource exploitation in Western Sahara: new research directions

The authors wish to thank the Leverhulme Trust (through their Early Career scheme) and the Spanish Ministry of Economy, Industry and Competitivity, (CSO2017-86986-P, AEI/FEDER, UE) for funding this research. We would also like to thank Patricia Lalonde for her translations and editorial work, as well as all participants of the 'Analysis of the Management and Exploitation of Natural Resources in Situations of Conflict: The Case of Western Sahara' project (funded by the aforementioned ministry), for their constructive comments on earlier iterations of this paper.This review article provides an overview of research to date with an explicit focus on natural resource exploitation in Western Sahara. It integrates findings from various perspectives and disciplines, and synthesises the research done with a view to revealing gaps and, therefore, potential new research directions. As the issue of natural resource exploitation in Western Sahara has been conceptualised in very different ways and from the perspectives of a variety of disciplines, the authors have opted for a semi-systematic review of the work done encompassing academic, non-academic, and activist backgrounds.Leverhulme TrustSpanish Ministry of Economy, Industry and Competitivity (AEI/FEDER, UE) CSO2017-86986-

Factors Influencing Imazapyr Herbicide Removal from Wastewater Using Photocatalytic Ozonation

This study investigates the degradation of imazapyr herbicide from wastewater by photocatalytic ozonation using TiO2 as a semiconductor. Effects of operational parameters on imazapyr removal efficiency including TiO2 dosing, initial herbicide concentration and pH were also studied. Obtained results showed that more than 90% of removal efficiency representing the disappearance of imazapyr was maintained until 7 mu M in the presence of 200 mgL(-1) of UV100-TiO2. Otherwise, the degradation of imazapyr followed the first-order kinetics with a photocatalytic rate constant of 0.247 min(-1), and complete degradation was achieved within 20 min using photocatalytic ozonation for 5 mu M of Imazapyr at pH 7

The Study of Peri-Urban Soil Contamination in the Kenitra Region, Morocco – Characterization and Assessment Using a Statistical Approach

The peri-urban solid waste in the Kenitra region is experiencing a significant change in terms of quantity and quality. High concentrations of both inorganic and organic materials are present in these wastes, posing a significant threat of pollution. This research seeks to analyze the extent of soil contamination by heavy metals, providing valuable insights to prompt proactive interventions and propose alternative solutions for sustainable waste management. The objective of this work is to study peri-urban soil contamination in the Kenitra region-Morocco. For that several soil contamination indicators have been analyzed, namely: nitrogenous, fertilizer and heavy metals concentration, soil pH, ... Etc. The analyzed soil samples were taken of water from the different points at the levels of the studied region. The analysis shows that the studied soils are polluted with Zn, Mg, Cu, Ni, Cr, Cd, Pb, and other chemical elements. The results obtained suggest a correlation between soil pollution and the concentrations of the measured heavy metals. Furthermore, the analysis shows that heavy metals, contamination is particularly related to the presence of lead, cadmium, and zinc. The zinc contamination in the soil is about 390 mg/kg for a standard of between 0.2 and 2 mg/kg. Lead concentrations are 53 mg/kg for a standard of 0.3 mg/kg. Based on Moroccan standards the soil is contaminated by lead, cadmium, and zinc

Effect of heat treatment on the photocatalytic activity of alpha-Fe2O3 nanoparticles: towards diclofenac elimination

alpha-Fe2O3 nanoparticles were synthesized via a straightforward method. XRD, FTIR, SEM, ESR, and DRS techniques investigated the influence of various calcination temperatures on the crystal structure, optical, and photocatalytic properties of the samples. The obtained results demonstrated that the average crystallite size increased with the increase in the calcination temperature. Measured and computed optical properties were in accordance and the bandgap energy decreased with the increase in the calcination temperature. The highest photocatalytic degradation efficiency for diclofenac (DCF) was obtained with the sample calcinated at 300 degrees C (96%). The photocatalytic process occurs because of the presence of OH center dot radicals. The addition of H2O2 led to the inhibition of OH center dot radicals that H2O2 scavenged

Insecticides in the typical agricultural groundwater in the Gharb plain (Morocco): spatial distribution and health risks

International audienceThe intensification of agriculture relies on the application of large quantities of phytosanitary products, which contaminate the air, soil, water, and risk human life. This study was carried out in the Gharb plain, which belongs to the Sebou watershed in the North-West of Morocco. The goal of this study is to evaluate the contamination of the groundwater by insecticides using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS) analyses. This research paper covers the analysis of 20 samples of 20 different wells for an irrigated perimeter of 250,000 ha of the surface. Further, the analyses show the presence of intense contamination caused by insecticides, which are concentrated in the southern part of the study area, where the contamination level is 50% of the water samples. This exceeds the norm of the World Health Organization (WHO) standard, which is represented in 0.5 µg/l. Furthermore, the analyses also detect the presence of 22 active ingredients of insecticides, such as malathion, methomyl alderine, dieldrin, and fenthion. Risk assessment in our studies allowed us to determine that the different RQ calculated for five insecticides (Malathion; Mythomil; chloropyrifos-ethyl; Diazinon) recorded in underground water were up to 1, which proves the intensive use of insecticide in this region and the high risk of contamination