Green synthesis of f-CdWO4 for photocatalytic degradation and adsorptive removal of Bismarck Brown R dye from water

Abstract

Cadmium tungstate, CdWO4, is well-known semiconducting material which exhibit good photocatalytic properties but its preparation is usually carried out at very high temperature. Hardly any report is available for its preparation through green route, and its application for water treatment. Therefore, the functionalized cadmium tungstate, f-CdWO4, nanoparticles synthesis through green, environmentally benign route using Brassica rapa leave extract and sodium tungstate and cadmium iodide was objective of the present work. The formation of f-CdWO4 was confirmed from FT-IR, XRD, and TEM, SEM and UV/Visible spectroscopic techniques. The average size of the particles was 54 nm as calculated from the XRD analysis, 37.23 nm radius was determined from UV–Visible spectrum, whereas average 27 nm breadth and 120 nm length was found from TEM imaging showing rod shaped f-CdWO4 nanoparticles. The f-CdWO4 was used for removal of toxic Bismarck brown R dye from aqueous solution through adsorption and photocatalytic degradation under sun light irradiation. The coloured water containing 10 mgL−1 concentration of dye could be cleaned with 1.5 gL-1 dose of f-CdWO4 at optimum condition. The adsorption capacity of f-CdWO4 for Bismarck brown R was found to be 46.5, 49.50, and 51.54 mgg−1 at 30, 40 and 50°C, respectively. The endothermic adsorption of Bismarck brown R followed pseudo-second order kinetics. The interaction between f-CdWO4 and Bismarck brown R, on molecular level, was investigated from FT-IR studies clubbed with isotherm, kinetics, and thermodynamics. The f-CdWO4 also showed good photocatalytic degradation activity and degraded 82.70% of Bismarck brown R in 50 mL solution having 20 mgL−1 dye concentration, with 1.5 gL-1 dosage of f-CdWO4. Therefore, f-CdWO4, prepared through green route, would be efficient for water treatment through both photocatalytic and adsorption activities. Keywords: Water treatment, Bismarck Brown, F-CdWO4, Green synthesis, Adsorption