No abstract

CdS nanoparticles were synthesized by the ultrasonic-assisted sol-gel method and characterized by X-ray diffraction (XRD). The Ag-doped CdS (Ag/CdS) nanoparticles were also synthesized by the ultrasonic-assisted sol-gel method and characterized by XRD, X-ray fluorescence spectrometry, scanning electron microscopy, and energy-dispersive X-ray analysis. The calculated sizes and experimental results are in good agreement. The calculated band-gaps of CdS and Ag/CdS were found to be 2.62 and 2.46 eV, respectively. Photocatalytic degradation of Direct Red 264 azo dye was investigated with CdS and Ag/CdS under UV-C and visible light irradiation. Experimental results indicate that the degradation rate of DR 264 follows pseudo second-order kinetics. Also, the intraparticle diffusion coefficients of CdS and Ag/CdS were determined.

In this work, a series of eight new spiro[3,4′]1,3‐dihydro‐2H‐indol‐2‐one‐2′‐amino‐4′,6′,7′,8′‐tetrahydro‐2′,5’(1’H,3’H)‐quinazoline‐diones were successfully synthesized through a three‐component reaction of 1H‐indole‐2,3‐diones (isatins), guanidine nitrate, and 1,3‐cyclohexanediones, by use of Kit‐6 mesoporous silica coated Fe3O4 nanoparticles (Fe3O4@SiO2@KIT‐6) as a highly efficient magnetically separable nanocatalyst in aqueous media at 60°C. Several notable features of thiseco‐friendly protocol are high yields of products, short reaction times, operational simplicity, and the use of easily available and recyclable catalyst.

Azo dyes are one of the synthetic dyes that have been used in many textile industries. Azo dye and their intermediate products are toxic, carcinogenic, and mutagenic to aquatic life. Removal of azo dyes is one of the main challenges before releasing the wastes discharged by textile industries. Photocatalytic degradation of azo dyes by nanoparticles is one of the environment‐friendly methods used for the removal of dyes from textile effluents. Therefore, this study focused on degradation of azo dye, Direct Red 264. Photocatalytic degradation of DR 264 azo dye was investigated using CdS and Ag/CdS nanoparticles immobilized on a cement bed in a continuous‐flow photoreactor under UV‐C exposure. The effect of the parameters of type and mass of catalyst, temperature, flow rate, dye concentration, and light intensity were evaluated for azo dye removal. Under optimal conditions, photocatalytic degradation of DR 264 azo dye using Ag/CdS nanoparticles immobilized on a cement bed in a continuous‐flow photoreactor obtained an efficiency of 99.99%. A developed kinetic model was proposed based on the intrinsic elementary reactions. The proposed model is in a good agreement with the Langmuir–Hinshelwood (L–H) equation. The pseudo–steady‐state approximation has considered for the concentration of hydroxyl radicals associated with the L–H model under certain conditions and explains consistently the dependence of the apparent kinetic parameter, kobs (the reaction rate constant), and KR (the adsorption equilibrium constant) with the light intensity. Based on the model, kobs for Ag/CdS was greater than the CdS nanoparticles.