Synthesis and Characterization of Orthophosphate Silver Powders

AbstractOrthophosphate silver with superior quality and quantum size effect is elaborated by precipitation from phosphate precursors. The powders were investigated by X-ray diffraction, SEM-EDS, FTIR, thermal analysis, and diffuse reflectance. Spherical like Ag3PO4 particles with size between 0.8 to 10μm were obtained. The powders crystallize in a cubic symmetry and the smaller crystallites are obtained with Na2HPO4 The optical gap, determined from the diffuse reflectance spectra through the Kubelka-Munk function, lies between 2.05 and 2.30eV

Kinetic study of spiramycin removal from aqueous solution using heterogeneous photocatalysis

International audienceSpiramycin macrolide antibiotic (SPM) can be photocatalytically degraded on TiO2 (anatase variety). The experiments are done in a batch reactor and the effect of some key parameters is investigated under low energy of artificial UV light. The reaction rate is affected by varying TiO2 dose, pH and SPM concentration. Under optimized conditions, a photodegradation efficiency of 98% is achieved and the SPM photodegradation follows pseudo-first order kinetics. The Langmuir–Hinshelwood (L–H) model is successfully used to fit the experimental data, indicating the dependence of the reaction rate on the chemical reaction step. The L–H model led to the determination of both reaction kinetic and adsorption/desorption equilibrium constants. In order to give an overall estimate of the by-products, chemical oxygen demand, total organic carbon, and calculated average oxidation state monitor the photodegradation proces

Facile preparation of CuBi2O4/TiO2 hetero-systems employed for simulated solar-light selective oxidation of 4-methoxybenzyl alcohol model compound

The selective photocatalytic oxidation of organic substances is today considered one of the green techniques to synthesize important starting materials in different technological applications. This work reports an efficient, simple and cheap strategy for the synthesis of a new photocatalytic CuBi2O4-TiO2 (CBO/TiO2) heterosystem at room temperature. The prepared powders were characterized by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectra (DRS), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The photocatalytic activity was evaluated by performing a probe reaction, namely the partial oxidation of 4-methoxybenzyl alcohol (4-MBA) to 4-methoxybenzaldehyde (4-MBAld) in aqueous solution under irradiation of simulated sunlight. The CBO/TiO2 coupled systems showed a higher photoactivity than the single photocatalysts reaching a selectivity of 45% towards 4‑methoxy-benzaldehyde with an alcohol conversion of 77% after 4 h of irradiation. Furthermore, although a high alcohol conversion was achieved, the selectivity towards 4-MBAld was significant, unlike what has been reported in the literature for many heterogeneous photocatalytic reactions whose selectivity generally decreases significantly with the increasing conversion of the starting alcohol molecule. The improved photocatalytic activity could be attributed to the partial coverage of the TiO2 surface by CBO which reduces the subsequent oxidation of the formed aldehyde

Etude de Quelques Parametres d`une Cellule Photoelectrochimique.

C

Kinetic and equilibrium studies of cobalt adsorption on apricot stone activated carbon

The activated carbon from apricot stone with H3PO4 and its ability to remove Co2+ are reported. The FTIR spectroscopy brings insights on interactions between the functional groups of the carbon and Co2+. Adsorption studies are carried in batch mode by varying the initial Co2+ concentration and pH. A comparison of two kinetic models on the overall adsorption rate shows that the system is described by the pseudo-second-order kinetic model. The Freundlich model fits the data with a monolayer adsorption capacity of 111.11 mg/g at pH 9. The enthalpy and free energy indicate an endothermic and not spontaneous proces

The adsorption of HCrO4 − on activated carbon of date pits and its photoreduction on the hetero-system ZnCo2O4/TiO2

Abstract The adsorption properties of activated carbon were successfully tested toward the elimination of hazardous HCrO4 − (30, 50, 70 and 100 mg L−1). The material was prepared from Algerian date pits by physical and chemical activations of ZnCl2/CO2 in the goal to develop the microporous volume. The characterization by N2 adsorption at 77 K, the mercury intrusion porosimetry and scanning electron microscopy showed important textural properties. CO2 increases the specific surface area (1192 m2 g−1) and pore volume (0.96 cm3 g). The HCrO4 − adsorption is described by a pseudo-first-order kinetic model, and the equilibrium data are fitted by the Langmuir model with a maximal adsorption capacity of 46.72 mg/g within 30 min and a constant K L (0.12 L g−1). The remaining HCrO4 − concentrations (8, 23, 32.5 and 43.5 mg L−1) were photocatalytically reduced on the hetero-system ZnCo2O4/TiO2 down to 5 mg L−1. The spinel ZnCo2O4, prepared by co-precipitation from the nitrates precursors and characterized by photoelectrochemistry, gives a conduction band of − 1.49 V SCE, more cathodic than the HCrO4 − level (0.53 V). Therefore, the photoelectrons transfer toward HCrO4 − species is achieved through TiO2 located midway between the spinel and chromate levels. The photocatalysis is investigated by varying the catalyst dose and HCrO4 − concentration. ZnCo2O4 has a gap of 1.82 eV and the best reduction efficiency (82%) was obtained under visible light (50 mW cm−2) and optimal conditions (HCrO4 − 23 mg L−1, pH ~ 7, ZnCo2O4/TiO2 50/50%) and follows a first-order kinetic with a rate constant of 3.86 × 10−3 min−1

Photocatalytic degradation of Ambroxol in aqueous Mn-TiO2 suspension: Kinetics, identification of intermediates and mineralization.

International audienc

Photocatalysis of rhodamine B and methyl orange degradation under solar light on ZnO and Cu2O thin films

We report the photocatalytic properties of ZnO and Cu2O thin films deposited on glass substrates at room temperature by DC sputtering and pulsed laser deposition. The photoactivity of the films was investigated through the degradation of rhodamine B (RhB) and methyl orange (MO) under solar light. In order to select the most suitable film of ZnO for the of RhB and MO degradation, the relationship between the characteristics (e.g. energy levels and defects concentration) of ZnO films and their effectiveness in the photocatalytic yield of RhB and MO been studied, where several films were deposited by using different oxygen partial pressures (PO2: 0.05–1.3 mbar), while Cu2O films were grown under a pressure of 0.01 mbar. The XRD patterns show that all ZnO films have (002) preferential orientation, and crystallite size increases from 73 to 122 nm raising PO2. The gap Eg of ZnO (3.26 and 4.15 eV) depends on PO2, and the films present photoluminescence emission in the UV–Vis-near IR region. On the basis of structural, optical and electrical characterizations of both films, a comparative study was carried out on the dyes degradation. Cu2O films exhibit a high photoactivity with MO (81.69%) under solar light (6 h), whilst for RhB the best elimination rate (60.85%) was achieved with ZnO films deposited at 0.1 mbar, which were also the ones exhibiting the highest PL peak intensity at the characteristic absorption wavelength of RhB (553 nm)

Physical and photoelectrochemical properties of spherical nanoparticles of α-AgBiS 2

International audienceWe have investigated the physical and photo electrochemical properties of α-AgBiS2 (schapbachite), synthesized from Bi2S3 and Ag2S in evacuated Pyrex ampoule at 550 °C. The precursors are prepared by precipitation from nitrates in ethylene glycol using thiourea as complexing agent and sulfide source. AgBiS2 crystallizes in a rock salt structure (Fm-3m). The transmission electron micrograph shows spherical nanoparticles with an average size of ~ 30 nm, a value very close to that obtained from the Williamson-Hall plot of the XRD powder pattern (33.06±1.28 nm). HRTEM gives inter reticular distance of 0.33 nm, a value in excellent agreement with that of the SAED analysis (d111=0.3276 nm). The diffuse reflectance spectrum indicates a direct optical transition of 0.89 eV. The thermal variation of the electrical conductivity is characteristic of semiconducting behavior with activation energy of 0.20 eV, electron mobility (µ300K) of 2.43 × 10−4 cm2 V−1 s−1 and an effective mass of 2.88 mo. The intensity-potential J(V) curve in alkaline medium (pH 10.2) shows a good electrochemical stability. The dark capacitance (C−2-V) exhibits a linear behavior, characteristic of n-type conduction (dC−2/dE>0), from which a flat band potential of 0.33 VSCE and an electrons density of 2.57 × 1021 cm−3 are determined. The valence band derives from S2−: 3p states while the conduction band is made up mainly of Ag+: 5 s orbital. The electrochemical impedance spectroscopy (EIS), measured in the dark and under illumination over the frequency range (10−3−105 Hz), indicates the contribution of both the bulk and grain boundaries.Graphical abstrac