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Cs1·48Sb0·78PMo11VO40 (CsSbPMoV) was prepared and characterized by many physico-chemical techniques. The spectroscopies 31P MAS-NMR, FT-IR) and X-ray diffraction showed that the salt is pure, of Keggin-type crystallizing in a cubic structure.The UV–Vis spectrum revealed the presence of molybdenum and antimony with mixed valence states, Mo(VI)/Mo(V) and Sb(V)/Sb(III). The optical properties showed two transitions: directly (1.20eV) and indirectly (1.38eV) allowed. The intensity-potential (J- E), plotted in Na2SO4 (0.1 ​M), exhibited a sluggish electrochemical system. The capacitance−2– potential (C−2 - E) curve showed n-type behavior with a flat band potential (Efb) of 0.10 ​V and a conduction band positioned at 4.65 ​eV, below vacuum (−0.1 VSCE), composed mostly of (Mo, Sb) 5s wave functions, negative of the •OH/H2O level. Therefore, CsSbPMoV was successfully tested for theoxidation of Orange II (OII), a hazardous dye, by •OH and O2•radicals under solar light. The discoloration obeys a first order kinetic model with an abatement yield of 68% and a photo catalytic half-life (t1/2) of 60 ​min.

Through careful choice of reduction conductions, a new hybrid host-guest compound [Cu12(C2N3H2)8Cl][(PW12O40)] was synthesized hydrothermally in the presence of 1, 2, 4 triazole as structure-directing agent. The material has been characterized by single-crystal X-ray diffraction, chemical analysis, FT-IR spectroscopy, thermal analysis and UV–Vis diffuse reflectance. The compound based on a two-dimensional (2D) supramolecular porous coordination polymer [Cu12 (C2N3H2)8Cl]3+ can accommodate in its cavities the Keggin polyoxotungstate anions, with host-guest interactions crystallizing in the monoclinic system (Space Group: C2/m). The metal organic species and Keggin anions are connected via hydrogen bonds and Cu…O short contacts giving rise to a three-dimensional architecture. The optical study shows a direct transition (1.60 eV) assigned to the O2−: 2p → Cu+: 4 s transition. The transport properties revealed a semiconductor comportment; the thermal variation of log (conductivity) versus 1000/T was fitted by a least square method to a straight line whose slope gave an activation energy of 54 meV. The chrono-amperometry and photo-electrochemistry, carried out in Na2SO4 (0.5 M) electrolyte, indicate n-type conduction with a flat band potential of +0.10 VSCE, making [Cu12(C2N3H2)8Cl][(PW12O40)] a promising solar material.

The \(\hbox {Co}^{2+}\) reduction on the hetero-system \(\hbox {CuFe}_{2} \hbox {O}_{4}/\hbox {SnO}_{2}\) under solar light is reported for the first time. The spinel \(\hbox {CuFe}_{2} \hbox {O}_{4}\), prepared by co-precipitation, is characterized photoelectrochemically, and the conduction band (\(-1.63 \hbox { V}_{SCE}\)) is more cathodic than the \(\hbox {Co}^{2+}\) level. \(\hbox {SnO}_{2}\), synthesized by chemical route, is used as electrons bridge to mediate the electron transfer. The photocatalysis is investigated in batch mode by varying the catalyst dose, the \(\hbox {Co}^{2+}\) concentration and pH. Reduction efficiency of 62% is obtained under sunlight (\(102\,\hbox {mW cm}^{-2}\)) and optimal conditions (\(\hbox {Co}^{2+}: 50\,\hbox {mg L}^{-1}, \hbox { pH } \sim 5.5, \hbox {CuFe}_{2} \hbox {O}_{4}/\hbox {SnO}_{2}: 1/1\)). The reduction follows a zero-order kinetic with a rate constant of \(0.29\,\hbox {mol L}^{-1} \,\hbox {mn}^{-1}\). The decrease in the conversion rate over illumination time is due to the competitive hydrogen formation on ultrafine co-clusters. \(\hbox {H}_{2}\) evolution rate of \(0.19 \, \upmu \hbox {mol}\,(\hbox {mg catalyst})^{-1}\,\hbox { mn}^{-1}\) under artificial light (\(29\,\hbox {mW cm}^{2}\)) is obtained.

The substituted pyrochlore La 1.9 Ba 0.1 Sn 2 O 7 was prepared by nitrate route and the physical and electrochemical characterizations were investigated. The optical gap is found to be 3.01 eV and the conductivity is characteristic of a semiconducting behavior with activation energy of 0.42 eV. The conduction band of La 1.9 Ba 0.1 Sn 2 O 7 (−2.64 V SCE ), predicted from electro negativities of the constituent atoms, is close to that determined experimentally (−2.99 V SCE ). The capacitance measurement (C −2 –V) exhibits a linear behavior, characteristic of p type conductivity, from which a flat band potential of −0.05 V SCE and hole density N D of 8.42 × 10 14 cm −3 were determined, in agreement with the small electrical conductivity (σ 300K ∼3 × 10 −6 Ω −1 cm −1 ). The Nyquist plot showed a semicircle which is a contribution of capacitance and resistance in parallel. A bulk resistance contribution (R b = 71 kΩ cm 2 ) and a low density of surface states are observed. The center of the arc is localized below the real axis with a depletion angle of 14° ascribed to a constant phase element (CPE). As application, chromate was successfully converted to Cr 3+ on the pyrochlore under sunlight. ∼1 h was necessary to reach the adsorption equilibrium for an initial chromate concentration of 10 −4 M. The conduction band is more cathodic than the potential of HCrO 4 − which is spontaneously reduced under solar light. The best performance is obtained at pH ∼ 3 with a catalyst dose of 1 mg/mL. 40% of chromate disappears with a quantum yield of 0.53% in less than 2 h. The process obeys to a first order kinetic with an apparent rate constant of 2.3 × 10 −3 min −1 .

The degradation of ibuprofen (IBP) in aqueous solution was investigated on α-(Cu,Fe)2O3 catalyst under visible irradiation. The material was prepared by a hydrothermal method and characterized by X-ray diffraction, Fourier transform infrared, BET analysis, electrical conductivity, diffuse reflectance and photo-electrochemistry. α-(Cu,Fe)2O3 crystallizes in the corundum structure and exhibit n-type conductivity with activation energy of 0.41 eV. It exhibits a direct optical transition at 2.02 eV; further transitions, indirectly allowed, occur at 1.93 and 1.69 eV. These bands located between those of CuO (~1.46 eV) and Fe2O3 (~2 eV) confirm the presence of the solid solution (Cu,Fe)2O3; the BET surface area of the sample averages 10 m2 g−1. The IBP photo-degradation, monitored by high performance liquid chromatography was found to have overall high conversion rates. The optimal performance was observed for a catalyst dose of 0.25 g L−1 and IBP concentration of 200 mg L−1 at pH ~11. By applying the optimal operating conditions, IBP conversion of 88% was obtained after 240 min under visible illumination.

The adsorption performance of diethyl and dibutyl phthalates on a new activated carbon prepared from an abundant biomass “Albizzia julibrissin Pods,” treated chemically by H3PO4 is investigated thr...

The preparation and characterization of the hetero-junctions x%Bi2S3/TiO2 (x = 1, 5, 10 and 15%) and their photocatalytic performances for the degradation of orange G (OG) under visible light irradiation are reported. The hetero-junctions are synthesized by precipitation method from bismuth nitrate on TiO2. The forbidden bands of Bi2S3 and TiO2 are found to be 1.54 and 3.43 eV respectively. Bi2S3 acts as sensitizer and exhibits n-type conductivity evidenced from the anodic photocurrent and capacitance measurements. The degradation of OG is confirmed by spectrophotometry and chemical oxygen demand (COD). The photocatalytic efficiency of the hetero-junction is dependent on the proportion of Bi2S3. Under visible light, a fast degradation is obtained on 10% Bi2S3/TiO2 and the OG degradation (10 mg L−1) follows a first order kinetic with a rate constant of 0.32 h−1. The performance of the prepared hetero-junction is better than that of the direct mixture of compounds due to intimate contact Bi2S3/TiO2. Under solar light, the photoactivity is strongly enhanced with a rate constant of 3.42 h−1.

A new inorganic-organic hybrid material [(H 2 pip) 3 ][α-PW 12 O 40 ] 2 ·4H 2 O, prepared by hydrothermal method, was structurally characterized by single-crystal X-ray diffraction. The compound based on a Keggin-type polyoxotungstate and piperazine (pip) displays a hybrid framework built from two (α-Keggin) 3− polyoxoanions and three (H 2 pip) 2+ hydrogen-bonded fragments, forming 3-D supramolecular architecture. The diffuse reflectance spectrum shows two optical transitions directly (3.27 eV) and indirectly (3.12 eV) allowed. The electrical conductivity follows an exponential law, indicating a semiconducting comportment with activation energy of 14 meV. The Mott-Schottky characteristic, plotted in Na 2 SO 4 (0.5 M) solution indicates n -type conduction with a flat band potential of −0.084 V SCE and electrons density of 4.24 × 10 18 cm −3 . As application, the photo-degradation of methylene blue (MB) upon UV irradiation was successfully achieved by OH • radicals. The improved activity is attributed to the potentials closeness of the valence and conduction bands with the radical levels.

It was found that the synthesized ZnFe2O4 with crystallite size of 49 ± 6 nm adsorbed Solophenyl Red 3BL (SR 3BL) dye and degraded it by photocatalysis under solar light. Analysis of the reflectance diffuse spectrum revealed that the optical gap of nanosized ZnFe2O4 was 2.04 eV. It was shown that the highest activity of the catalyst was achieved at pH 3 and a catalyst dose of 1 g/L.

International audience; The main objective of this study was to evaluate the efficiency of a new hetero-junction p-CuO/n-ZnO assisted photo-catalytic process for the degradation of amoxicillin (AMX). The catalysts is synthesized by chemical route and characterized by X-ray diffraction, scanning electron microscopy (SEM), thermal analysis, BET specific surface area and photo-electrochemistry. The initial AMX concentration, photo-catalyst nature, catalyst dose and initial pH of the solution were optimized in order to evaluate the mineralization extent. AMX (50 mg/l) was almost entirely removed after 4 h of exposure to solar irradiation at pH similar to 11, by using the hetero-junction ZnO/CuO (50:50 wt%). The final AMX concentration was determined by high performance liquid chromatography (HPLC) equipped with a photodiode array detector. The analysis of NO(3)(-)and SO42- released by the degradation reaction were quantified by ionic chromatography and the total organic carbon (TOC) indicated a high mineralization degree of AMX. Kinetic analysis suggested that the AMX degradation obeys to a pseudo-first-order with a rate constant of 9.95 x 10(-3) min(-1). Finally, the application of this method was extended to real effluents. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The adsorption behavior study of diethyl and dibutyl phthalates was investigated onto a new activated carbon prepared from an abundant biomass “Albizia julibrissin pods,” treated chemically by H3PO4. A series of experiments were conducted in a batch system to estimate the effect of operating conditions such as the adsorbent nature, the dose of adsorbent, the contact time, the initial concentration and the temperature on the adsorption efficiency. The optimum operating conditions were found to be 0.1 and 0.05 g of adsorbent for diethyl and dibutyl phthalates, respectively, at 30 min equilibrium time, 150 mg g−1 and 293 K. The adsorption isotherms for both phthalates were fit at different temperatures using the nonlinear regression of Langmuir, Freundlich, Dubinin–Radushkevich and Redlich–Peterson. The pseudo-first order, pseudo-second order by nonlinear regression and intraparticle diffusion models were used to describe the adsorption kinetic. The results show that the intraparticle diffusion model is not the limiting step governing the adsorption mechanism. The structural and textural characteristics of adsorbent surface were investigated. FTIR analysis of unloaded and phthalates-loaded adsorbent revealed that the aliphatic groups attached to phthalate esters are involved in adsorption mechanism.

The main purpose of this work is to produce low cost activated carbons from date stones wastes for the adsorption of l-phenylalanine. The activated carbons were prepared by chemical activation with KOH (ACK) and ZnCl2 (ACZ) and characterized by scanning electron microscopy, N2 adsorption–desorption isotherms and FT-IR spectroscopy. Both The activated carbons ACK and ACZ have high specific surface areas and large pore volumes, favorable for the adsorption. Batch experiments were conducted to determine the adsorption capacities. A Strong dependence of the adsorption capacity on pH was observed, the capacity decreases with increasing pH up to optimal value of 5.7. The adsorption follows a pseudo-second order kinetic model. Additionally, the equilibrium adsorption data were well fitted to the Langmuir isotherm, and the maximum adsorption capacities of l-phenylalanine onto ACK and ACZ were 188.3 and 133.3mgg−1 at pH 5.7, respectively. The thermodynamic study revealed that the adsorption of l-phenylalanine onto activated carbons was exothermic in nature. The proposed adsorption mechanisms take into account the hydrophobic and electrostatic interactions which played the critical roles in the l-phenylalanine adsorption.

We report the synthesis and characterization of a new mesoporous cobalt oxide-infiltrated NaY zeolite prepared by ion-exchange route. The scanning electronic microscopy (SEM) image shows homogenous and uniform grains size distributions smaller than 1 μm, unlike to CoOx particles, elaborated under the same conditions. The energy dispersion spectroscopy (EDS) data confirm the presence of cobalt, oxygen, silicon, and aluminum. The X-ray diffraction indicates a partial crystallization of cobalt oxide and the formation of new phases. N2 adsorption-desorption measurement shows a high-specific surface area for the modified material (579 m2 g−1), with Barrett-Joyner-Halenda (BJH) pore diameters in the range (3–8 nm). The cyclic voltammetry indicates a typical faradic process, and the electrochemical impedance spectroscopy exhibits Warburg diffusion at low frequencies. The charge-discharge curve shows a clear improvement in the charge capacity of the modified material compared to CoOx, due to the increased specific surface area. The galvanostatic charge-discharge tests of the modified electrode exhibit a typical battery behavior preceded by a pseudo-capacitive phenomenon.

Na2MnPO4F is synthesized by hydrothermal route at 453 K and the physical properties and photo-electrochemical characterizations are reported. The compound crystallizes in a monoclinic system (SG: P 21/n) with the lattice constants: a=13.7132 A, b=5.3461 A, c=13.7079 A, β=119.97°. The UV–visible spectroscopy shows an indirect optical transition at 2.68 eV; a further direct transition occurs at 3.70 eV, due to the charge transfer O2−: 2p → Mn2+: eg. The thermal variation of the electrical conductivity is characteristic of a semiconducting behavior with activation energy of 39 meV and an electron mobility (µ318 K=5.56×10−4 cm2 V−1 s−1), thermally activated. The flat band potential (+0.47 VSCE) indicates that the valence band derives mainly from O2−: 2p orbital with a small admixture of F− character while the conduction band is made up of Mn2+: t2g orbital. The electrochemical impedance spectroscopy shows the contribution of both the bulk and grains boundaries. The photocatalytic performance of Na2MnPO4F for the degradation of Rhodamine B (RhB) is demonstrated on the basis of the energy diagram. 88% of the initial concentration is degraded under UV light and the oxidation follows a first order kinetic with a rate constant of 0.516 h−1. Neither adsorption nor photolysis is observed. The photoactivity results from the electron transition from the hybridized band (O2−, F−) to the Mn2+: eg orbital, occurring in the UV region. The catalyst was subjected to three successive photocatalytic cycles, thus proving its long term stability.

In the last few decades, the presence of pharmaceutical products in the environment is known under the name of emerging contaminants. These substances can enter the aquatic environment via different sources, as parent compounds, metabolites or a combination of both. In this work, we have investigated the presence of four pharmaceutical active compounds belonging to the group of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), in wastewater, surface water and drinking water of Algiers, which have a direct impact on the Mediterranean Sea. The target analytes (ibuprofen (IBU), naproxen (NAP), ketoprofen (KET), and diclofenac (DIC)), were extracted from the water samples by using Solid Phase Extraction Oasis ® HLB Cartridges; the identification and quantification were realized by Gas Chromatography–Mass Spectrometry (GC–MS). To obtain the best resolution and precision, N -methyl- N -(trimethylsilyl) trifluoroacetamide (MSTFA) was used as the derivatization reagent and ibuprofen- d 3 was used as the internal standard. The obtained recoveries were good, ranging from 82% for ketoprofen to 120% for naproxen with relatively small standard deviations (≤20%). The target compounds were detected in wastewater, influent/effluent with concentrations ranging from 155.5 to 6554 ng/L, implicating removal efficiencies of wastewater treatment plants (WWTPs), between 30.3 and 95%. The surface water was also contaminated with pharmaceuticals from 72.9 ng/L for diclofenac to 228.3 ng/L for naproxen. In addition, the occurrence of ibuprofen and ketoprofen in drinking water, at concentrations of 142.1 and 110.9 ng/L, respectively, attracts concerns about possible impacts on human health.

In this paper, S-doped ZnO (SxZnO) was prepared using sol-gel method at different S amounts. The structural, optical and transport properties were investigated. The introduction of S atoms into the ZnO network was found to lower the crystallization level which results in reducing the crystallite size up to x=0.3. The doping process is confirmed by the observed peak at ~610 cm−1 in the ATR spectrum related to the Zn-S linking. EDX mapping shows a homogeneous distribution of S atoms on the particles surface. The best compromise between the band gap (Eg=2.96 eV), the charge carriers (NA=2.139×1022 cm−3), the conductivity (σ=5.56×10−4 Ω−1 m−1) and the mobility (µ=16.26×10−14 m2 V−1 s−1) is obtained for x=0.1. The conduction mechanism is assumed by small hopping polaron. The S-doping has impacted positively the photocatalytic activity of ZnO, with particularly high performance for S0.2ZnO.

The photo-electrochemical characterization of the hetero-system CoFe2O4/TiO2 was undertaken for the Ni2+ reduction under solar light. The spinel CoFe2O4 was prepared by nitrate route at 940 °C and the optical gap (1.66 eV) was well matched to the sun spectrum. The flat band potential (-0.21 VSCE) is more cathodic than the potential of Ni2+/Ni couple (-0.6 VSCE), thus leading to a feasible nickel photoreduction. TiO2 with a gap of 3.2 eV is used to mediate the electrons transfer. The reaction is achieved in batch configuration and is optimized with respect to Ni2+ concentration (30 ppm); a reduction percentage of 72% is obtained under sunlight, the Ni2+ reduction is strongly enhanced and follows a first order kinetic with a rate constant of 4.6×10-2 min-1 according to the Langmuir-Hinshelwood model.

Undoped zinc oxide (ZnO) and indium-doped (ZnO:In) thin films were grown at different temperatures (250–400 °C) on alkali-free borosilicate glass and n-Si (100) substrates by Ultrasonic Spray Pyrolysis method. The structural, compositional, optical and electrical properties of ZnO films were investigated by X-ray diffraction, Scanning Electron Microscopy, Rutherford Back Scattering Spectroscopy, Fourier Transform Infrared spectroscopy, photoluminescence (PL) and the four-point probe technique. The predominance of ultraviolet (UV) and blue emission intensities was found to be closely dependent on the resistivity of the film. The visible emission band (peaking at 432 nm) prevails for low film resistivity, ranging from 10− 2 to 1 Ω·cm. By contrast, for higher resistivity (> 1 Ω·cm), there is a predominance of the UV band (382 nm). The PL and photoresponsivity results of fabricated ZnO:In/n-Si(100) heterojunctions prepared at different temperatures are discussed. The maximum spectral response of the ZnO:8%In/Si heterojunction diode fabricated at 250 °C was about 80 mA/W at zero bias. The highlighted results are attractive for the optoelectronic applications.

The physical and photoelectrochemical characterizations of a new inorganic-organic hybrid single crystal material, synthesized by hydrothermal route, based on α-Keggin-type polyoxotungstate and Cu(I)-(trz) coordination complex, namely [Cu6(trz)6][α-PW12O40]2·H2O, [trz=1H-1,2,4-triazole] are investigated for the first time. The crystal structure, determined by single-crystal X-ray diffraction, reveals a 3-D supramolecular host-guest structure with Keggin anion as template. The diffuse reflectance indicates an optical transition at 2.91 eV, directly allowed, attributed to the Keggin polyoxoanions. The physical characterization shows a semiconductor behavior and the conductivity follows an exponential type law associated to a small polaron hopping between neighboring ions. The thermo-power measurement indicates n-type conduction with an electron mobility (0.54×10−6 cm2 V−1 s−1), thermally activated. The photoelectrochemical study, performed in Na2SO4 medium, confirms n-type conduction with a flat band potential of −0.65 VSCE and electrons density of 6.59×1018 cm−3. The electrochemical impedance spectroscopy reveals the predominance of the bulk contribution with a constant phase element and Warburg diffusion. As application, the photo-degradation of Rhodamine B upon sunlight and UV irradiation is achieved by the radicals O2•- and OH•. The improved activity is attributed to the wide depletion width (460 nm) and the potentials of the valence and conduction bands close to the radicals levels.

The undoped, Al-doped and In-doped ZnO thin films were deposited by ultrasonic spray pyrolysis technique, onto glass and p-Si substrates and the physical properties of the films were investigated. The X-ray diffraction, optical analysis and electrical characterisations, indicate that the films were polycrystalline with hexagonal wurtzite type structure and revealed that the aluminium doping deteriorates the crystalline and optical properties and enhances the electrical conductivity whereas indium doping improves all properties. The transport mechanism controlling the conduction through the heterojunctions was studied. For the heterostructures, the temperature dependent current–voltage characteristics showed rectifying behaviour in the dark, but current transport mechanism is not the same for all heterojunctions. Therefore, the presence of the interface states and volume defects are identified as limiting factors for obtaining a high quality heterojunction interface.

The spinel ZnFe 2 O 4 prepared from nitrate precursors is used for the reduction of chromate under visible light using TiO 2 as mediator. A gap of 1.97 eV is obtained for ZnFe 2 O 4 from the diffuse reflectance and the crystallite size (70–130 nm) is determined from TEM measurement. The current–potential characteristic indicates a good electrochemical stability. The photo electrochemical properties permit the construction of the energy diagram of the hetero-system ZnFe 2 O 4 /TiO 2 /HCrO 4 − solution. The conduction band of the spinel (−1.47 V SCE ) favors the physical separation of the electron/hole pairs and the electrons injection into TiO 2 . The best composition ZnFe 2 O 4 (75%)/TiO 2 (25%) is used to catalyze the reaction (2 HCrO 4 − + 3 C 2 H 4 O 4 + 1.5 O 2 + 8 H + → 2 Cr 3+ + 6 CO 2 + 11 H 2 O). 60% of Cr(VI) are reduced after 3 h of visible light irradiation and the activity obeys a first order kinetic with a half-life of 70 min. The photocurrent–photovoltage characteristic of the spinel gives an optical-to-electrical energy efficiency of 0.28% and a fill factor of 0.49.

The spinel CuFe2O4, prepared by nitrate route, is successfully tested for Ni2+ reduction under solar light. CuFe2O4 is a narrow band gap semiconductor with a direct optical transition at 1.66 eV. The electro-kinetic parameters indicate a good electrochemical stability with a high O2-over voltage. The energy diagram shows the feasibility of CuFe2O4 for Ni2+ deposition under illumination. At pH ~ 7, the conduction band (−1.22 V SCE ) is located below the Ni2+ level (−0.60 V SCE ), leading to a spontaneous nickel reduction under solar light. The charge transfer is mediated via TiO2. The photocatalytic performance is optimized with respect to the Ni2+ concentration and the catalyst dose. 72 % of Ni2+ (30 ppm) are reduced after ~5 h of exposure to sunlight (115 mW cm−2) on the hetero-system CuFe2O4/TiO2 (mass ratio = 1/1). The photochemical hydrogen evolution, an issue of energy concern, occurs competitively on ultra fine Ni aggregates. The improved performance {0.43 cm3 mn−1 (g catalyst)−1} is due to intimate contact of Ni/TiO2 and low over-voltage on nickel clusters.

The photoelectrochemical characterization of the hetero-system x % WS2/TiO2 (x = 0, 10 and 20) is undertaken to assess its photoactivity for iodide ion oxidation. The nanosized catalyst is prepared by sol–gel at 450 °C; the X-ray diffraction shows broad peaks with a specific surface area of 110 m2 g−1. The gap of WS2 (1.72 eV), determined from the diffuse reflectance spectrum, is well matched to the solar spectrum. The flat band potential (−0.83 V SCE ) is more anodic than the I2/I− level (~0.3 V SCE ), thus leading to iodide photooxidation. The electrochemical impedance spectroscopy reveals both the charge transfer and Warburg diffusion. The oxidation is catalyzed by dissolved oxygen through the formation of H2O2 and is optimized with respect to the I− concentration (0.25 M) and catalyst dose (1 mg L−1). A conversion rate of 81 % is reported under solar light within 3 h illumination. Hence, the heterosystem is attractive for the chemical storage through the reaction: ( $$2 {\text{ I}}^{ - } + {\text{O}}_{ 2} + 2 {\text{ H}}_{ 2} {\text{O}} \to {\text{I}}_{ 2} + {\text{H}}_{ 2} {\text{O}}_{ 2} + 2 {\text{ OH}}^{ - } ,\Delta {\text{G}}_{\text{R}}^{^\circ } = 3 5. 3 2 \;{\text{kcal}} \;{\text{mol}}^{ - 1}$$ ).

The semiconducting and photo-electrochemical properties of the system PANI-SSA (Polyaniline (PANI), 5-sulfosalicylic acid (SSA)), are studied to assess its photocatalytic performance for the H2 formation under visible irradiation. The X-ray diffraction exhibits broad lines with a mean crystallite dimension of ∼ 11 nm and an active surface area of ∼ 270 m2 g−1. A direct optical transition at 1.10 eV, is determined from the diffuse reflectance data. The conductivity (σ) obeys an exponential law with an activation energy of 0.33 eV computed from the slope dlogσ/dT. The (capacitance−2 – potential) data of PANI-SSA recorded in Na2SO4 (0.1 M) electrolyte indicates p-type behavior with a flat band potential (Efb) of 0.18 VSCE and a holes density (NA) of 4.83 × 1025 m-3. The Electrochemical Impedance Spectroscopy (EIS) studied in an extended frequency domain (1 mHz – 105 Hz), indicates the contribution of both the bulk and grain boundaries with a constant phase element (CPE). As application, PANI-SSA is successfully tested under visible irradiation because the potential of its conduction band (0.03 VSCE) is less cathodic than that of H2O/H2 (∼ -0.5 VSCE). H2 liberation rate of 13 μmol h-1 (mg catalyst)-1 and a quantum efficiency of 0.26 % under full irradiance (29 mW cm−2) are obtained, using Fe(CN)64- as reducing agent.

International audience; In this work, the Ferrioxalate complex was used to mineralize the widely used antibiotic amoxicillin (AMX). The effect of operational parameters such as Fe3+ concentration, the molar ratio (Oxalate/Fe3+), and initial pH was studied for achieving high efficiency of degradation and mineralization. The effect of inorganic ions in the degradation of AMX was also investigated. Optimization of an Artificial Neural Network (ANN) to predict the performance of the process was realized. Neural networks were applied to model AMX degradation using 75 experimental data. Analysis of the results shows that the oxalate: iron ratio is limited to 3 with a Fe3+ concentration of 0.35 mM. In order to avoid this limitation, an alternative solution was adopted to increase the molar ratio with the gradual and progressive use of oxalic acid ligand. Almost total degradation and mineralization of AMX was achieved at the free initial pH of 2.8 and final pH of 6. The study of the effect of inorganic ions showed that bicarbonate and sulfate ions play an important role in contrast to Cl− ions with no noticeable influence. Neural network application resulted in a MSE of 1.1543 × 10-5 and a correlation coefficient r of 0.99 for AMX degradation and MSE of 1.12162 × 10-5 with r of 0.99 for mineralization. The model can describe successfully the percentage of degradation and mineralization of AMX under various conditions. ANN and NSGA-II (Non-dominant Sorting Genetic Algorithm -II) hybrid method to solve a multi-objective problem was proposed to determine the optimal (Fe3+/Ox/UVA) operating and process parameters.

The nanoparticles of the spinel CaFe2O4 (CFO) with a crystalline size of 34 nm were synthetized by nitrate route. The phase was identified by X-ray diffraction (XRD) and confirmed by the Fourier transform infrared (FTIR); the lattice constants were refined by the Rietveld method. The optical properties were measured by diffuse reflectance and a direct forbidden band of 1.93 eV was determined. Also, the photo-electrochemical properties were investigated to build the potential diagram of the junction CFO/HCrO4− solution in order to predict the interfacial phenomena. Curiously, CFO is n-type semiconductor with a flat band potential of -0.24 VSCE enough cathodic to be involved in an electronic exchange with the chromate species. Indeed, the thermal variation of the conductivity follows an experimental law with an activation energy of 0.17 eV. The oxide is stable against photo-corrosion in presence of oxalic acid which captures the photoholes and enhances the photoactivity through the separation of electron/hole pairs. The photo reduction of Cr (VI) under visible-light irradiation is improved on CFO nanocomposite. Herein, the effect of pH, CFO dose and Cr(VI) initial concentration (Co) on the photo reduction of Cr(VI) was investigated. An abatement of 86 % of HCrO4− was achieved under optimal conditions (pH ∼ 3, CFO dose 0.6 g/L, Co 30 ppm) upon illumination (16 mW cm-2). The photoactivity reached 100 % under solar light (98 mW cm-2).

In this work, we have investigated a very rich source on valuable elements in mining to valorise and extract the light rare earth elements (REEs) contained in phosphatic mining waste. A detailed characterization was performed for the selected T1 fine dusting (rejection

The objective of this work is to investigate the optical and dielectric properties of the synthetized cobalt aluminate (CoAl2O4) by chemical route using nitrates as reagents. The X-ray diffraction shows a single spinel phase with a good crystallinity. The diffuse reflectance spectrum R (λ) recorded in the range (200–900 nm) enable us to calculate the refractive index n (λ), optical conductivity (σopt), extinction coefficient (k), dissipation factor (tan δ) and relaxation time (τ). The optical gap (Eg = 1.83 eV), was evaluated and confirmed by several methods. The n-type conductivity is evidenced from the capacitance-potential plots, which leads to flat band potential of -0.43 VSCE and an electron density of 1.44 × 1017 cm−3. As application, the photo-degradation of Congo Red (CR) a persistent and hazardous dye was successfully realized, yielding a depollution parentage of 94 % within 240 min for an initial concentration of 10 mg L−1.

We report the study of the physicochemical properties of the spinel CuCr2O4 and its photoactive effect with the hetero-system CuCr2O4/SnO2. The spinel CuCr2O4 presents a direct gap (Eg) of 1.39 eV, a stable behavior against photo-corrosion and a cathodic photocurrent which characteristic of type p conduction in conformity with the chrono-amperometric profile. The flat band potential (Vfb = −0.27 VSCE) was determined from the capacitance measurement. At natural pH, the degradation of CV (15 mg/L) is quasi total with CuCr2O4/SnO2 under sunlight after 90 min. CV degradation obeys pseudo-first-order kinetics with an apparent constant 0.012 min−1.

Ni2+ was reduced by photo-catalysis on the hetero-system p-CuCo2O4 /n-TiO2 under visible light. The spinel CuCo2O4, elaborated by nitrate route, was characterized photo-electrochemically. A direct forbidden band of 1.44 eV was determined from the diffuse reflectance. It exhibits p-type behavior and a conduction band (- 1.11 VSCE) made up of Co3+: eg orbital, more cathodic than the Ni2+ level (-0.68 VSCE). The rate of Ni deposition increases with increasing the spinel dose and peaks for the optimal ratio CuCO2O4/TiO2 (50/50) with 60 % conversion (30 mg L−1) in less than 3 h. This occurred because TiO2 mediates the electron transfer to adsorbed Ni2+ ions. The decrease of the conversion rate on the system CuCo2O4/TiO2 over illumination time is due to the competitive water reduction onto deposited Ni clusters. The in situ photo-deposition of Ni-clusters forms hetero-system CuCo2O4/TiO2/Ni intimately contacted and the H2 formation is highly improved because of the low Ni over-potential. H2-evolution rate of 4.69 μmol min−1 g−1 and a quantum yield of 0.68 % were obtained under a light flux of 2.09 × 1019 photons s−1.

Zn-doped CdS layers, with various percentage ratios [Formula: see text] (= [Zn[Formula: see text]]/[Cd[Formula: see text]]%) were grown on glass substrates by chemical bath deposition (CBD). The effect of Zn-doping on different properties of CdS is studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis and UV-visible diffuse reflectance. The XRD patterns indicated polycrystalline films with (111) orientation and the insertion of Zn does not change the crystallinity of CdS. The Raman spectra show one major peak centered around 300[Formula: see text]cm[Formula: see text] assigned to the first-order longitudinal optic (LO) phonon modes of CdS. The surface morphology visualized by AFM and SEM analysis showed the influence of the Zn-doping on the morphology of the films, the surface roughness is found to decrease from 16.5 to 8.9[Formula: see text]nm with augmenting the ratio [Formula: see text] from 0 to 6%. In regard to the SEM analysis, the increase of [Formula: see text] yielded a lower porosity of the film and voids, and the films become more homogeneous. The EDAX spectra confirmed the existence of Zn in the doped samples. The bandgap decreases from 2.44 to 2.37[Formula: see text]eV, while the transmittance increases from 76 to 86% with augmenting the ratio [Formula: see text].

New niobate Ca0.5Nb3O8.1.5H2O was elaborated by soft chemistry via Ca2+ → H+ exchange between calcium nitrate and niobic acid H3ONb3O8. The compound was identified by X-ray diffraction using the Rietveld refinement; it was characterized by thermal analysis (TG), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The layered compound resembles closely to the orthorhombic niobate KNb3O8. Two optical transitions indirectly (3.10 eV) and directly (3.34 eV) allowed were obtained from the diffuse reflectance. The photo-electrochemical properties are studied for the first time. The oxide exhibits n type conductivity with a flat band potential (Efb) of -0.12 VSCE and an electrons density (ND) of 6.51 × 1015 cm−3. The valence band formed from Nb5+: 4d orbital, is positioned at 7.59 eV below vacuum (2.84 VSCE). As application, Rhodamine B (Rh B, 10 ppm) a hazardous dye was successfully oxidized on Ca0.5Nb3O8.1.5H2O by •OH radicals under solar light; a conversion rate of 48% was obtained after 140 min. and the Rh B discoloration follows a first order kinetic with a half-life of 150 min.

The semiconductor Ag3PO4 was synthesized by precipitation using AgNO3 and Na2HPO4 as precursors with three different methods. Ag3PO4 prepared by addition of Na2HPO4 on AgNO3 gave the best photocatalytic degradation of Rhodamine B (Rh B) under both Light Emitting Diodes (LEDs) and solar light, due to the smaller size. The catalyst was characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance and photo-electrochemistry. The influences of the initial concentration of Rh B (5–20 mg L-1), catalyst dose (0.25 −1 g L-1), pH (4–11), intensity and source of light were investigated. Rh B was quasi totally degraded under the optimal conditions: 10 mg L-1 of dye, 0.5 g L-1 of Ag3PO4, Ph ∼ 7 and 10.5 mW cm-2. The degradation was controlled by UV–Vis spectroscopy and high-performance liquid chromatography (HPLC). The kinetic indicated that the Langmuir-Hinshelwood (L-H) model was well fitted to the experimental data. Additionally, the mineralization was investigated by the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC). Rh B was completely mineralized after 75 min of illumination and the degradation obeys to first order with a half-life 14.44 min. A photocatalytic degradation mechanism was proposed to explain the high activity under visible light. Moreover, the stability of the catalyst was checked.

The photoelectrochemistry of the hetero-junction Ag/NiFe2O4, elaborated by sol gel route, was successfully used for the nitrite oxidation under visible light illumination. The electrons of NiFe2O4 activated by visible light are transferred toward Ag particles, strongly contacted to NiFe2O4. The hetero-junction is generated by incorporating ultrafine Ag clusters, thereby precluding high over-voltages. The spinel was studied by thermal analysis, X-ray diffraction and scanning electron microscopy. The optical band gap of NiFe2O4 (1.63 eV) is assigned to the lifting of degeneracy of the Fe3+: 3d orbital by oxygen crystal field splitting in octahedral site. p-type conduction of NiFe2O4 was shown from the (capacitance−2 – potential)characteristic in KOH electrolyte (0.1 M). The valence band (+0.70 V) is more anodic than the potential of NO2− oxidation and the hetero-junction was successfully tested for the conversion of NO2− to NO3− under visible light irradiation. NO2− is a hazardous ion and the photocatalytic performance is due to the optimal band bending. The rate conversion {0.085 μmol NO2−(g catalyst)−1 mn−1} was quantified indirectly through the evolved H2 volume.

The present study focused on the physical and electrochemical properties of stannic sulfide SnS2 synthesized by a template-free chemical route using thiourea as a precursor. SnS2 powder was characterized by X-ray diffraction (XRD), diffuse reflectance and Raman. The XRD pattern confirmed the formation of the hexagonal phaseSnS2 (SG: P-3m1) with the lattice parameters a = 3.639 A, c = 5.868 A and a mean crystallite size of ~ 60 nm. The optical measurements gave a direct transition of 2.26 eV, further transition indirectly allowed was observed at 1.63 eV. The Mott-Schottky plot recorded in Na2SO4 (0.1 M) electrolyte exhibits a linear behavior, characteristic of n-type conductivity and confirmed by chronoamperometry. The flat band potential (−0.63 VSCE) is close to the photocurrent onset potential (Eon= −0.64 VSCE) and a donor density of 3.54 × 1016 cm−3 was determined. The electrochemical impedance spectroscopy measured in the range (10−2 − 5 × 104 Hz) showed two semicircles assigned to a faradic charge transfer (Rct = 2.46 kΩ cm2) and grain boundaries contribution (Rgb= 13.69 kΩ cm2). The conduction band, located at −4.02 eV below vacuum, is made up of Sn4+: 5p while the valence band (−6.28 eV) derives mainly from S2−: 3p. As an application, Rhodamine B was successfully oxidized by photocatalysis on SnS2, 93.67% of the initial concentration (10 mg L−1) disappeared after 3 h of exposure to solar light (90 mW cm−2).

NiBi2O4 was synthesized by sol gel method using citric acid as a complexing reagent. The formed gel was dried and calcined for 9 h at three temperature steps (400, 600, 800 °C) to get a single phase with the spinel structure. The as-prepared NiBi2O4 was characterized by X-ray diffraction, FT-IR spectroscopy, and UV–vis diffuse reflectance. The optical band gap (Eg =1.76 eV) was obtained from optical absorption spectroscopy. The thermal variation electrical conductivity, measured in the range (300–473 K), is characteristic of semiconductor, with a conduction mechanism by low polaron hopping and activation energy of 0.2 eV. As application, the methylene blue (MB) was successfully oxidized upon solar light. A removal conversion of 40 % was obtained after 2 h at room temperature. The total photo-oxidation of MB (30 mg/L) was obtained on the new hetero-junction NiBi2O4/ZnO at natural pH in less than 2 h. A photocatalytic degradation mechanism occurred through (electron-hole) pairs generation and the redox reactions taking place on the NiBi2O4/ZnO surface of MB are proposed to explain the high activity under solar light irradiation. The degradation kinetics followed a first order with an apparent constant rate of 0.15 h-1.

In this work, thin films of ZnO were deposited by DC reactive sputtering of zinc target under (Ar and O2) gas atmosphere, at a deposition temperature of 100 °C. A series of samples were prepared on both corning glass and p-doped crystalline silicon substrates, at different Ar flow rates (FAr) ranging from 0.5 and 2.5 sccm. The films properties were investigated by atomic force microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The results showed thin films with rough surfaces and polycrystalline structure. The electrical study (current-voltage characteristics) of ZnO/p-Si hetero-junctions revealed a rectification behavior. The highest forward current was obtained for FAr = 1.5sccm. The exposure at room temperature of ZnO/p-Si hetero-structures to ethanol vapors showed a high gas sensing response for ZnO/p-Si hetero-junctions with rough surface and high forward current, corresponding to FAr = 1.5 sccm. For a low concentration of ethanol vapor (10 ppm), the dynamic response at room temperature of ZnO/p-Si hetero-junctions revealed a sensitivity ranging from 40 to 80% with response and recovery times of 5 and 3 s respectively. Comparing these characteristics to those already obtained by other teams showed that the elaborated devices in this work are good candidates for fast sensors of low concentrations of ethanol vapors at room temperature.

Recently, the use of carbon based materials and magnetic nanoparticles for supporting or coupling with metal oxides such as ZnO is a promising axis. The use of carbon materials enhances the photocatalytic performance of ZnO for the degradation of organic pollutants because of their properties. The introduction of magnetic nanoparticles such as manganese ferrite (MnFe2O4) to non-magnetic ZnO provides the easy separation of the photocatalyst from the treated water using a magnet and to improve its photoactivity in the visible region of the solar spectrum. This work was focused on the synthesis of a new magnetically separable composite photocatalyst including ZnO, MnFe2O4 and tannic acid (TA) by hydrothermal method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and vibration sample magnetometer (VSM). The photocatalytic activities of the prepared photocatalysts were evaluated through the photocatalytic degradation of Congo Red (CR) under visible light and MnFe2O4/TA/ZnO exhibits the best photoactivity. The degradation yield of CR is 84.2% of CR over the MnFe2O4/TA/ZnO under the visible light for 90 min. At the end of five times recycling, the photocatalytic performance of CR presence the MnFe2O4/TA/ZnO can even reach nearly 77.5%. Such results demonstrate that the MnFe2O4/TA/ZnO exhibits great photocatalytic efficiency for CR compared to their constituent photocatalysts and easy separation from the dye solution by applying an external magnetic field.

Complete photocatalytic degradation of methyl orange (MO) was obtained in 60 min on the II-type hetero-system La2NiO4/ZnO, prepared by an impregnation method. The band gap of La2NiO4 and ZnO are 1.87 and 3.10 eV, respectively, with a direct optical transition. The position of the conduction and the valence band in the energy diagram confirms the formation of the II-type hetero-junction, thus facilitating the photo-degradation of MO. The kinetics of MO degradation obeys to the first order apparent reaction with a rate constant of 0.022 min−1. The reutilization of the hetero-system was studied with high removal efficiency after three photocatalysis runs.

(S,C) co-doped ZnO system was prepared by Sol-Gel method from a single source of dopant (thiourea). The X-Ray diffraction pattern was indexed in a wurtzite phase without secondary phases formation. The codoping was confirmed by the modification of the cell parameters and Zn C, Zn S, S C and C O bonds identification with XPS study. The electrical conductivity σe ~ 3 × 10−4(Ωm)−1 was improved at room temperature particularly for both compositions x = 0.05 and × = 0.1 which influenced positively the photo degradation of eosin under visible light. The proposed mechanism has led to a promising application of these materials as electrodes in the field of Dye Sensitized Solar Cells (DSSC). The optical constants were globally improved and impacted the photoactivity under UVA. The high performance of the catalyst (S,C)0.2ZnO which demonstrates electrical energy consumption per order of magnitude EE/O of 2.1 kWh m−3 was attributed to the lowest optical conductivity (σopt = 6.634 × 10+7), dissipation factor (tanδ = 2.75 × 10−7) and the highest relaxation time (τ = 1.242 × 10−15s). The prepared materials were stable under visible light and UVA irradiation even after five recycles. (S,C)0.2ZnO was found to remove eosin, Bisphenol A, Acetamiprid and 4-hydroxy benzoic Acid efficiently under sunlight.

Gadolinium cuprate Gd2CuO4 was synthesized by nitrate route and its physical and electrochemical properties were investigated for the first time. The cuprate was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The Diffuse reflectance infrared Fourier transform (DRIFT) spectrum confirms the characteristic peaks of Gd2CuO4 while the Brunauer-Emmett-Teller (BET) measurement gave a specific surface area of 20.45 m2 g−1. An optical gap of 1.41 eV was obtained from the diffuse reflectance (DR) and the transition is directly allowed. The electrical conductivity indicated semiconducting behavior with activation energy of 0.1 eV that correlates with the formal valence of copper. Indeed, the insertion of oxygen into the layered crystal lattice induces p-conductivity with mixed valences Cu3+/2+ and mechanism conduction by small polaron hopping. The carrier density (1.17 1019 cm−3) and flat potential (Efb = −0.33 VSCE) were determined from the (capacitance−2 – potential) characteristic. The conduction band (−1.64 VSCE), positioned at 3.11 eV below vacuum, is made up of Gd3+: (5d, 6s) hybridized orbital while the valence band (−0.23 VSCE/4.52 eV) derives mostly from Cu2+: 3d orbital.

Cobalt-Platinum bimetal nanoparticles (CoPtNPs) were electrodeposited on bare Pt electrode. A highly sensitive amperometric sensor-based on CoPtNPs/Pt modified electrode was constructed to determine ascorbic acid (AA). The Co-Pt nanoparticles were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Due to the synergistic effects of Co-Pt nanoparticles, the electrocatalytic activity of modified electrode showed a significant enhancement toward the oxidation of AA compared to Co/Pt and bare Pt electrodes in alkaline medium. The electrocatalytic activity of CoPtNPs/Pt was studied as a function of Co:Pt molar ratio in the deposition bath. The analytical performance of the proposed sensor has been investigated by chronoamperometry method under the optimized conditions. This sensor showed a linear response to AA concentration range from $$10\,\upmu \hbox {M}$$ to 0.5 mM with a detection limit of $$0.37\,\upmu \hbox {M}$$ (S/N = 3), a high sensitivity of $$103\,\upmu \hbox {A}$$ mM $$^{-1}$$ , and a fast response time. In addition, the reproducibility, selectivity and applicability of this sensor were assessed with satisfactory results. Cobalt-Platinum bimetal nanoparticles (CoPtNPs) was prepared as a new ascorbic acid sensor. CoPtNPs showed a sensitivity of $$103\,\upmu \hbox {A}\,\hbox {mM}^{-1 }$$ and a good selectivity against dopamine, uric acid, acetaminophene and glucose. The linear range appeared from $$10\,\upmu \hbox {M}$$ to 0.5 mM ( $$\hbox {R}^{2} = 0.996$$ ) with a low detection limit ( $$0.37\,\upmu \hbox {M}$$ ).

The aim of this work is to evaluate the degradation of of Bisphenol A (BPA), a representative endocrine disruptor chemical by ZnO under UVA irradiation in a batch reactor. Response surface methodology (RSM) has been used to develop a multi-variant regression model and to assess the influence of individual parameters as well as the interactive effects. Time (min), Catalyst (mg/l), H2O2 (mg), and pH were chosen as independent variables to optimize the degradation rate of BPA as response. The central composite design (CCD) consisting of 30 experiments determined by 24 full factorial designs with eight axial points and six center points was used to conduct experiments. The results showed tha the model predicted values are in good agreement with the experimental values, and the behavior of the model equation has supported the experimental observation with minor deviation. Separate validation experiment at predicted optimal condition ascertained the high predictive ability of the model equation. This work suggested that the ZnO assisted photocatalytic degradation is a versatile, economic, envinronmentally benign and efficient method for BPA removal in the aqueous environment

The paper describes the effect of ZnMn 2 O 4 doping with different Sn ratios. Sn x –ZnMn 2 O 4 is prepared with Sol–Gel route at 700 °C. The structural, optical and electrical properties were studied. The X-ray diffraction patterns indicate the formation of pure tetragonal phase for the ratios lower than 0.03%, while for other compositions, the secondary phases were observed. The attenuated total reflectance (ATR) analysis confirmed the localization of Sn in octahedral sites. The optical properties showed not only the increase of E g , but also the improvement of the optical characteristics such as extinction coefficient ( k ), optical conductivity ( σ opt ), dissipation factor (tan δ ) and the relaxation time ( τ ). The latter has been improved by 50%. The Hall measurements confirmed the transition of the conductivity mode, i.e, from p to n -type. The formation of Sn Mn 1+ point defects is evidenced; however, the transport properties indicate that the charge carriers are mainly localized.

The photo-electrochemical properties of the libethenite Cu 2 (PO 4 )(OH) were studied to assess the oxidation of orange G (OG) under both solar and artificial lights. The compound was synthesized by hydrothermal route and characterized by X-ray diffraction, scanning electron microscopy, thermal and chemical analyses, UV–vis diffuse reflectance and electrochemical impedance spectroscopy. The libethenite possesses an optical gap of 1.52 eV and exhibits n type semiconducting behavior with an activation energy of 20 meV. On the basis of photo-electrochemical properties, it was concluded that the conduction band of the material (=4.81 eV/+0.30 V RHE ) permits the formation of O 2 ·− radicals for the OG oxidation. A maximum elimination of 94% was obtained upon sunlight within 120 min exposure. The injection process of orange G into the conduction band of the libethenite is confirmed by the photocurrent measurements at different concentrations. The decolorization process proceeds like a photo-Fenton reaction, based on copper ions. Referring to the energetic diagram, a degradation mechanism is proposed. Cu 2 PO 4 (OH) catalyst permits to activate H 2 O 2 and initiate the decomposition of OG molecules. The OG removal follows a pseudo-first order kinetic with an apparent rate constant of 6.2×10 −3 min −1 under sunlight.

The steam reforming of methane over NiO/ZnO mixed oxides with different nickel contents was studied. Solids to x% Ni/ZnO (x = 4 and 10%) were deposited on ZnO by impregnation from nickel nitrate solution; after vaporization the solid is calcined at 500°C for 6 h. The catalysts were characterized by X-ray diffraction (XRD) and BET method, scanning electron microscopy (SEM) and temperature programmed reduction (TPR). The XRD patterns revealed the NiO phase for all calcined catalysts. The chemical analysis confirmed the theoretical values of nickel. The catalysts were pre-treated under hydrogen at 500°C in situ, overnight before testing for the steam reforming of methane reaction (CH4/H2O/Ar = 10/10/80) in the temperature range (475°C - 650°C) under atmospheric pressure. The activities of both catalysts were investigated in a fixed-bed reactor for the Methane Steam Reforming (MSR) reaction. Globally, it was shown that the catalyst 10% nickel content has an important effect on the catalytic performances of solids i.e. the better results of hydrogen production were obtained with 10% wt. Ni/ZnO (28 ′ 10-3 mol/g catalyst).

The spinel Co2SnO4 is prepared by chemical route to assess its feasibility for the oxidation of neutral red under visible illumination. The diffuse reflectance gives a band gap of 1.72 eV, properly matched to the sun spectrum. The electrons in the conduction band (0.16 VSCE), determined from the capacitance measurement, permit the formation of O2− radicals, responsible of the neutral red oxidation. The dye concentration, catalyst dose, agitation speed and light flux are optimized. A degradation of 85% is obtained under sunlight within 45 min for 10 mg/L concentration. The oxidation follows a pseudo second order kinetic with an apparent rate constant of 11.5 × 10−3 L/mg/min according to the Langmuir–Hinshelwood model.

The study deals with the effects of the Mg-doping on the structural, optical and electrical properties of ZnMn 2 O 4 . Mg x -ZnMn 2 O 4 is elaborated by Sol-Gel route at 700 °C. The X-ray diffraction profiles show the synthesis of a pure tetragonal phase over the whole 0–0.1% investigated range. No secondary clusters are detected. The attenuated total reflectance spectra position the Mg in octahedral sites. The extinction coefficient, optical conductivity, dissipation factor and the relaxation time are improved. The latter has been upgraded by 70%. The Hall Effect measurements confirm the conserved semi-conducting p -type. The Mg Mn 1− point defects are evidenced; however, an antagonist effect between the carrier concentration and the mobility is generated.

In this study, a rapid and simple method based on reversed-phase high performance liquid chromatography (RP-HPLC) using a photodiode array detector (PDA) for the simultaneous analysis of five pollutants including aniline and its degradation products, para-aminophenol, meta-aminophenol, ortho-aminophenol and phenol, was developed. The retention and selectivity of these pollutants were investigated by testing three different columns (C18, C8 and C4) and changing several experimental parameters such as the organic modifier nature and content, buffer concentration, pH value and column temperature. The best chromatographic results were obtained using the C4 column and a mobile phase composed of MeOH/acetate buffer (10 mM, pH 5) (60:40, v/v), with λ = 270 nm and a flow rate of 1 mL min−1. The influence of the temperature was also investigated in the range of 10–50 °C; the results indicated the dependence of the enthalpies of transfer of the analytes on the mobile phase and the nature of the stationary phase, and a good linear correlation of lnk vs. 1/T was observed for all the tested columns. The linearity of the method ranged from 2.0 to 60 μg mL−1 for all compounds, with correlation coefficients varying from 0.9987 to 0.9999. Recoveries of aniline and its degradation products in water ranged from 87.51% to 101.35% while the relative standard deviations varied between 0.31% and 1.62% (n = 6). The limits of quantification of the method ranged from 0.0778 to 0.2073 μg mL−1. The results show that the method we developed is fast, low cost and can meet the requirements for the determination of aniline and its degradation products in waste or natural waters.