Hydrothermal Synthesis and Characterization of K7V5W8O40·12H2O: Application to Rhodamine B Removal by Adsorption/Photocatalysis

Abstract

The vanadotungstate K 7 V 5 W 8 O 40 •12H 2 O synthesized by hydrothermal route at 453 K was reported for the first time. The compound crystallizing in a Keggin type structure was characterized by powder X-ray diffraction, FTIR spectroscopy and UV-Vis diffuse reflectance; it was successfully tested for the removal of Rhodamine B (Rh B). The effects of contact time, initial concentration and pH were investigated. The adsorption capacity reached ~ 40% in aqueous solution within 16 h. Pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were applied to fit the experimental data. The pseudo-second-order was the best to describe the adsorption. The equilibrium isotherms were also analyzed by different models. Negative free enthalpy (ΔG) suggested that adsorption Rh B is spontaneous. The positive enthalpy (ΔH) entropy (ΔS) indicated endothermic process with an increase in the randomness of the solid/liquid interface. The compound showed 42% degradation of the remaining concentration after 4 h exposure to solar radiation.

Synthesis and characterization of the semiconductor CuBi2O4 for optical and dielectric studies. Application to methyl violet degradation under visible light

“…The treatments of discharges are often made obligatory in order to remain under the World Health Organization's approved threshold (WHO), including the incineration [1], adsorption [2], biodegradation [3] and photocatalysis [4,5]. The ideal treatment would be one that consumes the fewest possible products, less energy and at low cost.…”