In Situ One-Step Hydrothermal Synthesis of Fe3o4@Mil-100 (FE) Core-Shells For Adsorption of Organic Dyes
A new route for preparing magnetic Fe3O4@MIL-100(Fe) core-shell architecture is proposed via in situ one-step hydrothermal strategy, in which Fe3O4 microspheres not only serve as magnetic cores but also provide Fe(III) for the formation of MIL-100(Fe). The MIL-100(Fe) is uniformly grown as a shell on the surface of Fe3O4, and the shell thickness can be fine-tuned from 73.4 nm to 148 nm by simply controlling the reaction heating time. Compared with that of bare Fe3O4, the surface area and pore volume of the Fe3O4@MIL-100(Fe) is significantly increased from 26 m2 g-1 and 0.0483 cm3 g-1 to 730 m2 g-1 and 0.4526 cm3 g-1 while the magnetism is barely affected with magnetization saturation (Ms) values at 46.6 emu g-1. The adsorption ability of the Fe3O4@MIL-100(Fe) was tested using several dyes as model analytes, and the results indicate it showed high extraction affinity and capacity (221 mg g-1) towards methylene blue (MB) which is primarily based on electrostatic interactions and size filter effect. The MB adsorption isotherm follows Langmuir model and obeys pseudo second-order kinetic model. Intra-particle diffusion model reveals that both film and pore diffusions are involved in the rate limiting steps for adsorption. The adsorption is controlled by enthalpy change rather than entropy effect. The adsorption process was proved to be spontaneous and exothermic based on the calculated ΔH, ΔS and ΔG values. Facile synthesis procedure, immense magnetism, high adsorption capacity and excellent reusability of Fe3O4@MIL-100(Fe) make it an attractive candidate for application of MB removal from polluted environmental samples.