Résumé: In this study, the complexity of sodium ascorbate as a reducing reagent for copper by executing reactions with different ascorbate concentrations at 30°C and a copper concentration at 5 mM was emphasized. It was found that increasing the molar ratio of nascorbate/nCu2+ from 1:1 to 10:1 prolonged the time for the completion of the reduction from 30 to 300 min, respectively. The reactions were investigated by the cyclic voltammetry method and the products were characterized by scanning electron microscopy and X-ray diffraction analyses. The synthesized materials obtained with molar ratios of 1:1 and 10:1 were composed of 55.47% Cu + 44.53% Cu2O (labeled as As1) and 73.66% Cu + 26.34% Cu2O (labeled as As10), respectively. Both products were tested for their ability to discolor Basic Red 29 via the Fenton reaction. The discoloration of the dye was more rapid with As1, due to the higher Cu2O content

Résumé: Abstract Herein, a composite zinc formed by ZnO and different zinc sulfur species is synthesized via a simple reduction of zinc sulfate by sodium sulfite under air. The obtained product is found to be very efficient in the activation of persulfate (PS) when compared to commercial ZnO. Diluted PS at 2 mM in homogeneous system allows the degradation of 24.83% of Basic Red 29 (BR29) after 120 min at 40 °C. The addition of 5 mg of the composite zinc increases the yield to 74.89%, while commercial ZnO registers 50.21% under the same conditions. The effectiveness of the composite sample is found to be due to the presence of ZnS and SO32− species that act as dopants for PS activation. The degradation reactions follow the pseudo-first order with both catalysts. The main components involved in the degradation process are superoxide radical followed by singlet oxygen and then sulfate radical. Further application of ultrasounds at 40 kHz and addition of H2O2 at 1 mM reduces the reaction time for total degradation to 40 min with the composite zinc and 70 min with commercial ZnO

Résumé: Abstract A two-level full factorial design with interactions was effectively used to screen for parameters impacting the degradation of Direct Red 89 (DR89) by thermally activated persulfate. Four variables were identified as critical: reaction temperature, persulfate concentration, initial pH of medium, and initial DR89 concentration. The goodness of fit of the reduced model was tested by generating plots of descriptive statistic, residuals versus predicted responses, normal probability versus residuals, and observed versus predicted values, as well as examining the analysis of variance table. The observed and the predicted response values of the reduced model exhibited a good correlation, with R2, , Q2, and p of 0.990, 0.983, 0.968, and 0.000, respectively. To determine optimal operating parameters, the desirability function was utilized, and it was determined to be 0.988 with a predicted response of 99.89% for an initial DR89 concentration of 51.96 mg/L, a persulfate concentration of 12 mmol/L, a reaction temperature of 60 °C, and a pH of 3.

Résumé: Abstract Nanocrystalline (Co2Mn)100-xNix ( ) alloy powders were prepared by mechanical alloying in a high-energy planetary ball mill. Morphology, structure, and microstructure have been analysed using scanning electron microscopy and X-ray diffractometry. Magnetic properties have been investigated employing magnetization measurement in range under an applied magnetic field up to 1 T. The Ni addition to Co2Mn powders led to the formation of a highly disordered face-centred-cubic solid solution (FCC-SS) with a soft magnetic character. The lattice parameter and the crystallite size are increased with Ni addition; while the microstrains’ variation is reduced. Electronic structure calculations have been performed in the framework of the self-consistent ab initio calculations, based on Korringa-Kohn-Rostocker (KKR) method combined with the Coherent Potential Approximation (CPA). The powders were tested in the oxidation of methylene blue via a heterogeneous Fenton-like process in which H2O2/•OH were produced in situ. Up to 97.13% of oxidation was achieved after 70 min with 30 mg of powders at 50 °C.

Résumé: A two-level full factorial design with interactions was effectively used to screen for parameters impacting the degradation of Direct Red 89 (DR89) by thermally activated persulfate. Four variables were identified as critical: reaction temperature, persulfate concentration, initial pH of medium, and initial DR89 concentration. The goodness of fit of the reduced model was tested by generating plots of descriptive statistic, residuals versus predicted responses, normal probability versus residuals, and observed versus predicted values, as well as examining the analysis of variance table. The observed and the predicted response values of the reduced model exhibited a good correlation, with R2, , Q2, and p of 0.990, 0.983, 0.968, and 0.000, respectively. To determine optimal operating parameters, the desirability function was utilized, and it was determined to be 0.988 with a predicted response of 99.89% for an initial DR89 concentration of 51.96 mg/L, a persulfate concentration of 12 mmol/L, a reaction temperature of 60 °C, and a pH of 3.

Résumé: In this study, copper particles were synthesized by using sodium ascorbate as a green reducing agent under atmospheric conditions. The product was micron-sized and mainly formed by metallic copper Cu with a minor presence of Cu2O. The product was used as a catalyst in the discoloration of methylene blue in a heterogeneous Fenton-like process in which H2O2 was produced in situ. The effect of different parameters such as copper loading, dye concentration, pH of the solution, and temperature was studied. The total discoloration was achieved after 42 min with 30 mg of copper at 60 °C and pH= 3. The amount of H2O2 produced in situ during methylene blue discoloration was evidenced by the permanganate method. It was found the formation of 110 µM after 40 min. The external addition of H2O2 at 0.001 M reduced the time for total discoloration to 10 min and the application of 40 kHz ultrasounds reduced the time further to 6 min.

Résumé: Abstract In this study, two iron precursors (FeSO4 and FeCl3) were used for the synthesis of iron particles via a reduction reaction with KBH4. Detailed characterizations were carried out using X ray diffractometry, scanning electron microscopy and magnetic analysis. The results showed ferromagnetic submicron particles with different proportions of Fe° and Fe3O4. The particles were tested as catalysts for the discoloration of methyl orange (MO) in heterogeneous Fenton process. The results show that the nature of the precursor impacted the activity of the obtained product. In fact, 78.83 and 42.36 % of MO were discolored after 5 min of reaction in the presence of the catalysts synthesized with FeSO4 and FeCl3 respectively with H2O2 at 1 mM and 40 °C. Coupling ultrasounds with heterogeneous Fenton process reduced the time for total discoloration to 4 and 10 min with the same samples respectively. Regardless of the conditions used the sample synthesized with FeSO4 possessed the highest potential for MO discoloration.

Résumé: In this study, copper was prepared through a green chemical reduction process using sodium ascorbate under atmospheric conditions. The product was micron sized and mainly formed by metallic copper with a minor presence of Cu2O. The product was used as oxidant in the degradation of methylene blue in a heterogeneous Fenton-like process. The concentration of methylene blue in the solution was determined by the changes in absorbance at 665 nm with UV–VIS spectrometer. The effect of different parameters, such as copper loading, dye concentration, pH of the solution and temperature, was studied. Total oxidation was achieved after 42 min with 30 mg of copper at 60 °C and pH 3. The addition of H2O2 at 0.00116 M reduced the time for total oxidation to 10 min and the application of 40 kHz ultrasounds further reduced the time to 6 min.

Résumé: The discoloration of malachite green (MG) was investigated by heterogeneous Fenton-like process using copper as catalyst. Copper was synthesized with a simple and ecofriendly method using sodium ascorbate as green reducing agent. The synthesized product formed by Cu-Cu2O was characterized by SEM, XRD and EDX analyses and was applied in the in situ production of H2O2/radical dotOH. Different parameters were investigated in order to optimize the discoloration process of MG by copper such as catalyst loading, temperature and initial pH of dye solution. Total discoloration was achieved after 60 min with 0.03 g of copper at pH 3 and 60 °C. In order to decrease the discoloration time, ultrasounds at 40 kHz and H2O2 at 0.001 M were associated to copper. Total discoloration was attained after 6 min. The kinetic of the reaction followed first order in all cases and the activation energy of MG discoloration by copper was 90.51 kJ/mol.

Résumé: This study presents the discoloration of methylene blue by heterogenous Fenton-like process using copper. Copper was prepared with sodium ascorbate, an eco-friendly reagent under atmospheric conditions and characterized using X-ray diffraction and scanning electron microscope analysis. Sub-micron-sized particles were formed and mainly composed of metallic copper Cu with the minor presence of Cu2O. The obtained product (labeled as CuR) was compared to a commercial zero-valent copper (labeled as CuF) in the discoloration process of methylene blue. Different parameters such as copper loading, temperature and initial dye concentration were studied. Under the same conditions, CuR and CuF registered 95.04% and 20.46%, respectively, after 10 min of reaction. The discoloration process was due to the in situ production of H2O2 which was evidenced by permanganate method. It was found the formation of 0.18 mM and 75 µM of H2O2 after 2 min of reaction with CuR and CuF, respectively. The reaction rate with CuR was 5 times faster than that with CuF and both followed a pseudo-first-order reaction kinetic. The high activity observed with CuR was found to be due to the presence of Cu2O.

Résumé: Development of enhanced methods for copper particles synthesis is crucial for the improvement of material science and technology. Therefore, in this study a successful synthesis of copper metal was achieved by chemical reduction. Ascorbic acid was used as a reducing agent. In the presence of soda, copper sulphate pentahydrated (CuSO4, 5H2O) with acid ascorbic at 60 °C of temperature produced metallic copper powder with the total degradation (100%) of copper ions (Cu2+). The presence of hydroxide ions (OH-) is necessary to achieve and improve the chemical reduction reaction. Several parameters, as reducing agent volume, reaction temperature and soda quantity were investigated and checked their impact in this research study. The obtained powder was washed and dried in the fresh air then analysed by X-ray diffraction.

Résumé: Copper(II) ions (Cu2+) in copper sulfate solutions (CuSO4) can be reduced with several carbohydrates to produce copper metal powder. In this study glucose was used as a reducing agent. The big challenge in this study was to find the optimum conditions for copper ions reduction because they were entwined with positive conditions for degradation and hydrolyses of sugar (D-glucose). For that reason, the impact of several parameters on these conditions was investigated in a series of experiments in this research study. The glucose concentration (0.2-1.6M), the temperature (30-70 °C), initial sodium hydroxide concentration (0.2-0.4M), the role of adding sulfuric acid (H2SO4) at different volumes (0.6-3 mL) and the addition of ascorbic acid at different doses (4-20 mL) were the considered key parameters that were studied in this research. The synthesis of copper was restricted due to organic acid build up and reactions of the degradation products and copper. Under optimum conditions using glucose as a reducing agent, maximum of 48% of copper ions were transformed to copper metal (Cu). By adding ascorbic acid at the end of the experiment process, reduction efficiency was 100% where total and complete copper reduction was achievable. Most of solid particles were analyzed and the characterization and nature of the produced solid was achieved by X-Ray Diffraction.

Résumé: In this study the leaching of CuO particles by glycine, an environmentally friendly leachant, was investigated under different conditions. It was found that the variation of glycine and NaOH concentrations as well as CuO loading influenced slightly the dissolution of CuO while temperature, the volume of solution and the nature of stirring impacted greatly the dissolution process. Magnetic and mechanical stirring registered inverse effects. In fact, increasing the volume of solution from 105 to 405 mL decreased the dissolution of CuO from 100% to 26.2% registered after 180 min respectively under magnetic stirring, while it increased from 43.5% to 91.7% respectively under the same conditions with mechanical stirring. Thus, the nature of stirring is a crucial parameter that may radically change the dissolution results. The dissolution was found to be controlled by chemical reaction.

Résumé: A series of experiments were conducted to examine the effect of citric acid on the dissolution of zerovalent zinc. The effects of citric acid concentration, the presence of anions and temperature were studied. The results have shown that zinc dissolution registered a maximum of 34% with 0.5M citric acid after 270 min and that the nature of anions present with citric acid affected differently the dissolution rate. In fact, the presence of 2M nitrates with 0.5M citric acid dissolved totally zinc after 30min while 91.85% and 13.15% were dissolved in the presence of 2M chlorides and sulfates respectively after 270min. SEM analyses have shown that the morphology of the corroded surface depended on the composition of the solution. The kinetic study has shown that zinc dissolution was controlled by the chemical reaction in all cases and that the activation energy was 39.3 kJ mol-1.

Résumé: The catalytic reduction of NOx under different oxygen concentrations leading to different NO/NO2 compositions has been studied in the presence of V3W9Ti and V8W9Ti catalysts in a tubular flow reactor. The results have shown that increasing O2 concentration leads to increase the NOx reduction in low temperature range [150-275 °C]. Slight effect of O2 concentration on NOx conversion was observed at higher temperatures. SCR reaction also occurred in the absence of gaseous oxygen but with low NO conversion indicating the strong redox properties of both catalysts. Aged catalysts exhibited relative good activities in NOx reduction. This is probably due to the sol gel method used for the preparation of the catalysts known to improve the catalysts properties.

Résumé: A series of experiments were conducted to examine the effects of three organic acids (propionic, malic and citric acids) on the rate of Pb dissolution in order to evaluate its potential environmental pollution risk. The effects of acid concentration, agitation device, temperature and hydrodynamic conditions were investigated. The results show that propionic acid which contained the lowest number of functional groups had the greatest effect on Pb dissolution. In fact, it dissolved 100% of Pb particles after 35 min at the concentration of 5 mM at 25 °C while 92.1 and 47.6% were dissolved by malic and citric acid, respectively, under the same conditions. It was also found that the effect of the nature of the acid interfered with that of particle size and the hydrodynamic conditions making the system complicated to interpret totally.

Résumé: The processes of aluminum degradation in HCl, H2SO4, HNO3 and NaOH solutions were investigated in static and agitated media. The effects of concentration, temperature, and mixture of acids were studied. The dissolution of aluminum was faster in NaOH and HCl than in H2SO4 and HNO3. The activation energies were 86.5 and 52.4 kJ/mol for Al dissolved in HCl and NaOH respectively. An inhibiting effect on Al dissolution was observed with the mixture HCl + HNO3 regardless of the conditions used while a synergetic effect was observed with the mixture H2SO4 + HCl using acids at 4 M.

Résumé: The reactivity of ZnO during its dissolution by citric acid in different electrolytic environments was studied. It was observed that at low concentration (0.05 mol/L) citric acid was able to dissolve 90.4% of ZnO after 1 h at 50 °C. The addition of chlorides, nitrates and sulfates enhanced the dissolution to 98%, 84% and 67% respectively attained after 15 min at 40 °C. In the absence of citric acid, Cl−, NO3− and SO42 − also reacted with the solid surface leading to dissolve 4.6%, 4.9% and 13.7% of ZnO respectively at 50 °C after 60 min of reaction. The dissolution was controlled by surface chemical reaction in case of zinc dissolved by citric acid mixed with chloride and nitrate ions. When the dissolution was performed in the presence of citric acid alone and citric acid mixed with sulfates, the chemical reaction in an initial stage and transport through the boundary layer in a second stage were the rate controlling steps.

Résumé: An experimental study is presented on facilitated transport of copper (II) cations through a bulk liquid membrane containing di(2-ethylhexyl) phosphoric acid (D2EHPA) in dichloromethane. The effects of different parameters on copper transport through the membrane such as the carrier concentration, pH of the product and feed phases, stirring speed and temperature were investigated. It was found that copper transport was greatly affected by stirring speed and the pH of both aqueous phases, while temperature influenced weakly the copper transport. The extraction of copper from ammoniacal solution was very fast reaching 100% after just 1 h while only 2% of copper remained into the membrane at the end of the operation.

Résumé: In this study, the dissolution of CoO from CoO/Al2O3 catalyst with HCl, H2SO4, and HNO3 solutions was investigated in a batch reactor employing parameters that were expected to affect the dissolution rate of cobalt, such as stirring speed, temperature, and acid concentration. It was found that 99.82% of cobalt was dissolved after 4 h with HCl at 2 M, 75 °C, and a liquid-to-solid ratio (l/s) of 100 mL/g, while only 31.96% and 13.57% cobalt dissolutions were reached with H2SO4 and HNO3, respectively, under the same operation conditions. The difference in dissolution rates was due to the presence of different anions (Cl−, NO3−, and HSO4−) involved in the surface reactions. Dissolution kinetic of cobalt was examined according to a heterogeneous model. It was found that the dissolution rate was controlled by surface chemical processes in all cases.

Résumé: n this study, the dissolution of CuO in HCl, H2SO4, HNO3 and citric acid solutions was investigated in a batch reactor employing parameters expected to affect the dissolution rate of copper such as stirring speed, temperature and acid concentration. It was found that 99.95% of copper was dissolved after 14 min with inorganic acids at 0.5 M, 25 °C and l/s = 10 ml/g while more drastic operation conditions were needed to reach the same dissolution efficiency with citric acid solution. Anions seem to be involved in the surface reaction. The dissolution kinetics of CuO was examined according to heterogeneous model and it was found that the dissolution rate was controlled by surface chemical process in all cases.

Résumé: The present paper presents a simple method for the reliable preparation of nano-scaled ZrO2. In this wet synthesis, a stable Zr sol is produced by using a mixture of Zr(OC3H7)4, HNO3 and H2O. Precipitation is firstly achieved when ammoniac conditions are adjusted. Zirconia is formed by annealing the gel-like product at 200 °C resulting in agglomerated particles. De-agglomeration is simply achieved by ultrasonic exposure leading to particles of about 60 nm revealing a BET surface area of 150 m2/g. The beneficial effect of this nano-sized material as compared to bulk ZrO2 is shown in SCR using corresponding Fe2O3/ZrO2 patterns.

Résumé: The catalytic reduction of NOx in the typical operation temperatures and oxygen concentrations of diesel engines has been studied in the presence of V3W9Ti in a tubular flow reactor. The results have shown that the selective catalytic reduction is strongly affected by the oxygen concentration in low temperature range (150–275°C). At higher temperatures, the reaction becomes independent of the O2 concentration. The rate of the selective catalytic reduction of NO with ammonia may be considerably enhanced by converting part of the NO into NO2. DRIFT measurements have shown that NH3 and NO2 are adsorbed on the catalyst surface on the contrary of NO. The experiments have shown that the decrease in N2 selectivity of the SCR reaction is mainly due to the SCO of ammonia and to the formation of nitrous oxide.

Résumé: Titania-supported tungsten and vanadia oxides with different W and V loadings and calcined at different temperatures have been prepared by the sol–gel method and characterized. Large amount of tungsten (9%; w/w) provides thermal stability to WO3/TiO2 systems upon addition of vanadia. It is found that WO3 and V2O5 crystallites are formed when their concentrations are higher than those corresponding to three monolayers. DTA analyses have shown that the presence of V2O5 crystallites is not essential for the transformation of titania anatase into rutile. High reactivity in limited temperature range (225–350 °C) has been observed for the catalyst with 8% (w/w) V2O5 with a high formation of N2O amount during the SCR reaction. The catalyst with 3% (w/w) V2O5 exhibits a slight lower reactivity but with a high selectivity to N2 preserved in all working temperature. The selective catalytic reduction of NOx by ammonia over 3%V2O5–9%WO3/TiO2 and 8%V2O5–9%WO3/TiO2 catalyst prepared by the sol–gel method have been investigated. More significant changes in activity occurs on the catalyst V8 which displayed a higher NOx conversion but in a narrow temperature range while V3 exhibits a lower reactivity but with high selectivity to N2 over the whole temperature range.

Résumé: Dans ce travail, une poudre de cuivre a été synthétisée avec une méthode écocompatible basée sur la réduction d’une solution de sulfate de cuivre avec l’ascorbate de sodium (vitamine C). La poudre obtenue est composée majoritairement de cuivre métallique (Cu) avec la présence mineure de cuprite (Cu2O). Le produit obtenu a été utilisé pour générer in-situ H2O2/• OH via une réaction d’oxydo-réduction se produisant en milieu aqueux acide entre le cuivre et l’oxygène dissout dans l’eau. Le cuivre a été utilisé dans une réaction de décoloration du méthyl orange (MO). Les résultats ont montré que l’utilisation 30 mg du cuivre à 60 C a totalement décoloré le MO au bout de 90 min. L’application des ultrasons à 40 kHz et l’ajout de H2O2 à 6 mM à fortement réduit le temps pour la décoloration totale à 6 min.