Preparation and Characterization of Fe3O4@nSiO2@mSiO2–NH2 Core–Shell Microspheres for Extracting Allura Red from Aqueous Solution

Allura red (AR) is a water-soluble synthetic colorant often used as an additive in the food industry, but excess AR can be harmful to human health. In this work, we report the development of a new removal method for AR by using amino-functionalized microspheres with Fe 3 O 4 cores and twolayer shells composed of SiO 2 particles and perpendicularly aligned mesoporous SiO 2 (designated Fe 3 O 4 @nSiO 2 @mSiO 2 –NH 2 ). The material exhibits good dispersibility in aqueous solutions and a high saturation magnetization of 45.68 emu g − 1 , and can be magnetically separated efficiently with an external magnet. Importantly, the material has great adsorption capacity of 29.6 mg g − 1 for AR and the capacity for reuse with a simple treatment. The adsorption process is very fast and the kinetics data are consistent with a pseudo-second order model. Based on these, a rapid and efficient method for extraction and analysis of AR in water and soft drinks has been established.