In this study, pure ZnCo2O4 and SnO2/ZnCo2O4 mix photocatalysts have been synthesized by the sol-gel process with three different SnO2 loading percentages (10, 20, and 30 wt %). Their photocatalytic activities were assessed on the degradation of organic pollutants in water under visible illumination. The structural, morphological, and optical properties were analyzed by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), nitrogen adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), and UV–Visible diffuse reflectance measurements. The results have shown that the materials are composed of a crystalline ZnCo2O4 matrix with a decrease in crystallite size with the amount of SnO2. Weakly crystalline SnO2 is also observed for loaded samples. The specific surface area is modified with the loading ratio. The evaluation of the photoactivity of the samples under visible light for the degradation of p-nitrophenol has highlighted that all materials are highly photoactive under visible light thanks to heterojunction between the two oxides. An application test has been conducted on a dye, congo red, showing the same tendencies. An optimal amount of SnO2 loading is observed for the sample containing 20 wt % of SnO2. A comparison with commercial Evonik P25 showed that the materials developed in this work have five to six times better efficiency under visible light, leading to a promising photocatalyst material.
Tamazert kaolin was modified with dimethyl sulfoxide (DMSO). The starting material and resulting from the intercalation were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). Intercalation caused considerable changes in our clay by increasing the basal spacing to 11.22 Å, an intercalation rate of 98 %. The adsorption of methylene blue was studied as a function of pH, contact time, temperature, dye concentrations and adsorbents. Kinetic data have been adequately described by the pseudo-second order and intraparticle scattering model. The adsorption isotherm is in good agreement with the Redlich-Peterson model. A change in thermodynamic values (ΔH°, ΔS° and ΔG°) was observed after intercalation. Adsorption became non-spontaneous exothermic and ordered.
a b s t r a c tThe removal of cadmium(II) and lead(II) from aqueous solution was investigated using thermally processed halloysite. The samples were previously heated in the 200-1000°C range at interval of 200°C. The resulting materials were characterized by thermal analysis, electron microscopy, X-ray diffraction, electrophoretic mobility measurement, and N2 adsorption. Metal adsorption was studied as a function of pH, contact time, temperature, metal and adsorbent concentrations, and correlated with the physicochemical properties of the materials. A particular interest has been focused on the spectroscopic study to elucidate the mechanism of the interaction of M 2+ (M = Cd or Pb) cations with the best adsorbent. The kinetic and equilibrium data were adequately described by the pseudo-second order and Redlich-Peterson models, respectively. The mechanism mainly involved an electrostatic interaction between these metallic cations and the hydroxyl groups of surface. Whatever metal, maximum adsorption occurred for the material that preserved its structure, i.e. H200 (halloysite heated at 200°C) for Pb(II) and H400 for Cd(II). The intermediate adsorption of H600 and H800 was explained by their poorly organized structures due to dehydroxylation. H1000 was found to be the worst adsorbent due to its low specific surface area. Regardless of the material, the adsorption sequence was: Pb > Cd, which was correlated with the ionic properties of each metal. As long as it preserves its structure, halloysite clay proves to be an efficient adsorbent for removing heavy metals from aqueous solutions.
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