Iron tailings derived core-shell magnetic mesoporous silica microspheres for effective Congo red removal

Magnetic silica materials are widely applied in biomedical and environmental fields, but the current synthesis of low-cost, rapidly adsorbed magnetic silica materials remains a challenge. Utilizing typical solid waste iron tailings as precursors of iron and silicon, magnetic silica microspheres with core-shell structures have been economically and effectively prepared by stepwise modulation through solvothermal and sol-gel methods. The characterization results demonstrate that magnetic silica microspheres have a core-shell structure with magnetic iron oxide as the core, dense silica as the middle layer and mesoporous silica as the shell. Furthermore, because the shell of magnetic silica microsphere is mesoporous silica, it has the characteristics of large specific surface area (963 m 2 /g), small pore size (2.57 nm) and pore volume (0.63 cm 3 /g) that mesoporous silica usually has. Additionally, the Congo red adsorption result indicated that the magnetic silica microsphere can reach adsorption equilibrium for Congo red within 2.5 min under acidic conditions, and can be recovered by magnets after adsorption. Due to the large specific surface, small pore size and pore volume characteristics of the shell of the microsphere, the adsorption of Congo red by the microsphere only occurs on the surface through hydrogen bonding, which shows rapid adsorption. Overall, the study not only provides a theoretical basis for the high-value utilization of iron tailings, but also offers a new strategy for the development of adsorbents for the ultra-rapid removal of Congo red adsorbent removal in emergency situations.