Ultrasound-assisted synthesis of silica-coated magnetite material decorated with silver nanoparticles for the detoxification of 4-nitrophenol

Among phenolic pollutants, 4-nitrophenol is a common organic pollutant readily discharged in water bodies. It causes an adverse effect on the lives of human beings and aquatic species. Therefore, it is essential to remove this pollutant from water resources. Herein, we report an eco-friendly approach for the synthesis of silica-coated magnetite material decorated with ultra-fine silver nanoparticles, as a magnetically recyclable catalyst for the detoxification of 4-nitrophenol. This synthetic strategy employs only ultrasound waves throughout the preparation of catalyst material. Further, no stabilizer was added in any of the steps involved in synthesis. Initially, iron oxide nanoparticles were synthesized from ferrous sulphate heptahydrate precursor and coated with silica matrix. Subsequently, silver nanoparticles were deposited over it. Silver was chosen among the noble metal nanoparticles, as it is abundantly available and economical and exhibits good catalytic properties. This catalyst material was well characterized using HRTEM, XRD, VSM and FTIR techniques. HRTEM studies revealed that Ag nanoparticles of size between 2 and 5 nm were dispersed over the silica-coated magnetite. The significant merits of this approach are usage of ultrasound waves, stabilizer-free and reduced time consumption in the synthesis of catalyst. Furthermore, a facile magnetic separation of catalyst using bar magnet is noteworthy to this method. The catalyst was successfully recycled for eight times without any significant loss in the activity. This can be a promising catalyst for the treatment of wastewater contaminated with 4-nitrophenol.