Adsorption of methyl orange on nanoparticles of a synthetic zeolite NaA/CuO

CuO supported on an NaA zeolite (CuO/NaA) was prepared with an NaA zeolite through the ion-exchange (CuO/NaA) method. The morphology and the physicochemical properties of the prepared samples were investigated by XRD, MEB, and EDS. The various parameters, such as contact time, catalyst dose, initial dye concentration, initial pH, and temperature, influencing the adsorption of methyl orange (MO) were optimized. The MO adsorption equilibrium was reached after 240 min of contact time. Removal of MO is better at neutral pH than in acidic and alkaline solutions. Among the tested models, the equilibrium adsorption data are well fitted by the Langmuir isotherm. The adsorption kinetics is best described by the pseudo-second-order model. The evaluation of the thermodynamic parameters, i.e. ΔG^o, ΔH^o, and ΔS^o, revealed that MO adsorption was spontaneous, while the activation energy (20.98 kJ/mol) indicates a physical adsorption. The photodegradation of MO decreased from 100 mg/L down to 2 mg/L when the solution is exposed to visible light.     

The main and recent syntheses of the N-CF3 motif

This review provides an overview of the various synthetic pathways of the N-CF₃ group. This pattern can be generated either from fluoride ions or from electrophilic, nucleophilic, or radical trifluoromethylation. This article mainly focuses on the most recent and prominent studies.     

Physicochemical and photocatalytic properties of the ZnO particles synthesized by two different methods using three different precursors

ZnO particles with different morphological forms and various scale sizes were successfully synthesized as photocatalysts using two different methods (sol–gel and precipitation) and three precursors (zinc acetate dihydrate, zinc nitrate hexahydrate, and zinc sulfate heptahydrate). These materials were calcined at 500 °C for 3 h and characterized by various physicochemical techniques such as X-ray diffraction, Fourier transform infrared, transmission electron microscopy, S_BET, and UV–vis diffuse reflectance. The results showed that the crystalline structure, size, and morphology of the ZnO particles are strongly influenced by the preparation method and by the nature of the precursor used as reactant. The photocatalytic efficiency of the synthesized photocatalysts was evaluated by the photodegradation of methyl orange in aqueous solution under UV-A light. The results showed that the ZnO nanoparticles prepared the by sol–gel method from zinc acetate are more efficient than those prepared by the precipitation method.     

Anionic surfmers in mini-emulsion polymerisation

Mini-emulsion polymerisation of styrene or methylmethacrylate, initiated with ammonium persulphate, have been carried out, in the presence of hexadecane or of polymethylmethacrylate as hydrophobic costabilizer, and the simple hemiester of linear dodecyl alcohol and maleic anhydride, or polymerisable surfactants (surfmers) derived from the condensation of succinic anhydride and either hydroxy propylmethacrylate (MAES), or hydroxyethylmethacrylate (ABS). While the pure surfmers have not so good surface activity, from surface tension measurements, stable mini-emulsion droplets are obtained using a mixture with low amounts of SDS, which have diameters of about 100–200 nm, which remain stable upon polymerisation. Most of the surfmers remain grafted onto the particle surface, thus conferring to these particles strong stability in the various tests. However, due to the high water solubility of the surfmers, another part remains in the serum as unconverted monomer or water-soluble polymers. To cite this article: A. Guyot et al., C.R. Chimie 6 (2003).