Synthesis of SiO2@NiO magnetic core-shell nanoparticles and their use as adsorbents for the removal of methylene blue

SiO2@NiO core-shell nanoparticles with variable NiO shell thickness have been prepared via homogeneous precipitation. The as prepared and calcined core-shell nanoparticles have been characterized using powder X-ray diffraction, thermal gravimetric analysis, FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, and surface area measurements. The shell thickness and the particle size of NiO in the core-shell nanoparticles have been controlled using different concentrations of the nickel salt. The NiO shell thickness, as observed by the TEM, varies from about 46 to 144 nm. The SiO2@NiO core-shell nanoparticles show higher remanent magnetization, saturation magnetization, and lower coercivity compared to pure NiO nanoparticles. The SiO2@NiO core-shell nanoparticles have been tested as adsorbents for the removal of methylene blue from an aqueous solution and the core-shell nanoparticles possess good adsorption efficiency for the cationic dye compared to pure NiO and SiO2.