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

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

Diazoles y triazoles derivados del extracto de aceite de ricino: síntesis, efecto hipoglucémico, potencial antioxidante y actividad antimicrobiana

The ricinoleate triglyceride was extracted from castor-oil seeds grown in Algeria and isolated by catalytically methanolyse to methyl ricinoleate. Six diazole and triazole derivatives of ricinoleic acid were synthesized and characterized: 1,3,4-oxadiazole-5-thione (4); 1,3,4-thiadiazole-5-thione (5); 4-N-amino-1,2,4-triazole-5-thiol (7); 1,2,4-triazole-5-thione (9); 5-amino-1,3,4-oxadiazole (10) and 5-amino-1,3,4-thiadiazole (11). The antibacterial and antifungal screening data of synthesized compounds showed appreciable inhibition and among them, 5, 7 and 8 showed more inhibition on Gram positive Enterococcus faecalis than reference ampiciline; while compounds 1, 7, 8, 10 and 11 showed competitive antifungal effects compared to reference amphotericin B. In addition, all synthesized compounds (1-11) showed competitive antioxidant properties, particularly compounds 7 at 125, 250, 500 and 1000 μg/mL and compounds 4, 5 and 9 at a concentration of 1000 μg/mL. The intermediate compounds 1, 2 and 8 showed anti-α-amylase activity at various concentrations in the range of IC50 = (120.25 ± 1.17 - 130.42 ± 2.48). Oxadiazole 4 showed the best α-amylase inhibition by 78.5% at a concentration of 1000 μg/mL.Los triglicéridos de ricinoleico se extrajeron de semillas de aceite de ricino cultivadas en Argelia y se sintetizó catalíticamente con metanolisis el ricinoleato de metilo. Seis derivados de diazoles y triazoles de ácido ricinoleico se han sintetizado y caracterizado: 1,3,4-oxadiazol-5-tiona (4), 1,3,4-tiadiazol-5-tiona (5), 4-N-amino-1,2,4-triazol-5-tiol (7), 1,2,4-triazol-5-tiona (9), 5-amino-1,3,4-oxadiazol (10) y 5-amino-1,3,4-tiadiazol (11). Los datos de detección antibacteriana y antifúngica de los compuestos sintetizados mostraron una inhibición apreciable, entre ellos, los compuestos 5, 7 y 8 mostraron más inhibición en Enterococcus faecalis Gram positivo que la ampicilina de referencia. Mientras que los compuestos 1, 7, 8, 10 y 11 mostraron una influencia antifúngica competitiva en comparación con la anfotericina de referencia B. Como todos los compuestos sintetizados (1-11) mostraron propiedades antioxidantes competitivas, particularmente los compuestos 7, a 125, 250, 500 y 1000 μg/mL también compuestos 4, 5 y 9 a una concentración de 1000 μg/mL. Los compuestos intermedios 1, 2 y 8 mostraron actividad anti-α-amilasa a diversas concentraciones en el rango de IC50 = (120.25 ± 1.17 - 130.42 ± 2.48). El oxadiazol 4 mostró la mejor inhibición de la α-amilasa en un 78.5% a una concentración de 1000 μg/mL

Standard study on the impact of integration in the multilateral ‎trading system: The experience of rising power in Latin America ‎‎(Brazil), "Lessons for the Algerian Economy‎‏"‏

: تهدف هذه الورقة البحثية إلى التعرف على واقع تجربة دولة البرازيل في مجال الانفتاح التجاري عن طريق النظام التجاري المتعدد الأطراف، و هذا من خلال قياس أثر الانفتاح التجاري لهذه الدولة على معدلات النمو الاقتصادي و نسبة تدفق الاستثمار الأجنبي المباشر خلال الفترة (1980-2013). و لتحقيق هذا المبتغى استعملنا لهذا الغرض اختبار التكامل المتزامن (cointégration). لمعرفة العلاقة في المدى الطويل بين كل من الانفتاح التجاري و المتغيرات الاقتصادية السابقة الذكر. ناهيك عن ذلك يهدف هذا البحث إلى الخروج بدروس للاقتصاد الجزائري بصفته دولة على مشارف الانضمام إلى هذا النظام التجاري المتعدد الأطراف.The purpose of this article is to recognize the reality of the experience of the State of Brazil in the field of trade liberalization in the multilateral trading system,  by measuring the impact of the opening of trade of this countries on economic growth rates and FDI flows during the period report (1980 - 2013). To achieve this goal, we used for this purpose the simultaneous integration test (cointegration) To know the long-term relationship between each of the opening of Trade and the Economic variables mentioned above. Not to mention that this research aims to find lessons from the Algerian economy as a state at the periphery of membership in the multilateral trading system

Preparation and characterization of the semiconductor CuMnO2 by sol-gel route

Nano crystallites of the crednerite CuMnO2 are prepared by sol–gel method with two-step annealing process. The powder heated at 450°C under air flow shows a mixture of CuO, Mn2O3 and CuxMn3−xO4. However, when calcined at 900°C under N2 atmosphere, the crednerite CuMnO2 with a monoclinic structure (space group: C2/m) is obtained. The Raman spectrum shows a single peak at 679cm−1 assigned to A1g mode whereas the infrared analysis confirms the linearity of CuO23− units. The optical transition at 1.70eV, determined from the diffuse reflectance is attributed to the inter-band d-d transition of Cu+ ion. The oxide exhibits semiconducting properties with an activation energy of 0.21eV. The photo-electrochemical measurement shows p-type conduction due to O2− insertion in the two dimensional lattice. The flat band potential (+0.12 VSCE), indicates a cationic character of both valence and conduction bands deriving from Cu+: 3d orbital

Sol–gel synthesis and characterization of the delafossite CuAlO2

Nanocrystalline CuAlO2 is synthesized by sol–gel method using ethylene glycol as solvent. The stages of formation are followed by thermal analysis. The X-ray diffraction pattern of the powder heat-treated at 1100 °C shows a single phase, indexed in a rhombohedral symmetry (R 3¯¯¯ m). The apparent crystallite size (57 ± 8 nm) is determined from the Williamson–Hall plot. The direct optical transition (=3.69 eV), evaluated from the diffuse reflectance spectrum, is attributed to the charge transfer (O2−: 2p → Cu+: 4s). The oxide is p-type semiconductor, and the conduction occurs predominantly by small polaron hopping between mixed valences Cu2+/+, due to oxygen insertion in the layered crystal. The photoelectrochemical characterization gives a flat band of 0.20 VSCE and a hole density of 1.13 × 1018 cm−3. The semicircle centered on the real axis, in the electrochemical impedance spectroscopy (EIS), is due to the absence of constant phase element with a pure capacitive behavior. The straight line at 35° at low frequencies is attributed to the diffusion in the layered structure

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