Kinetics and thermodynamics of methylene blue adsorption on the Fe-oxide nanoparticles embedded in the mesoporous SiO2

摘要

Fe-oxide nanoparticles with a diameter of similar to 10 nm embedded into the porous structure of mesoporous SiO2 particles using temperature regulated chemical vapor deposition and a subsequent annealing process. The kinetics and thermodynamics of MB adsorption on bare SiO2 and Fe-oxide/SiO2 particles were investigated. MB adsorption kinetics of both SiO2 particles can be described by pseudo first order and intra particle diffusion plot. Thermodynamic parameters were calculated based on the modified Langmuir isotherm model. Equilibrium constant and spontaneity of MB adsorption was increased with the presence of Fe-oxide nanoparticles inside the SiO2 pores, which can be ascribed to the more negative values of DH of Fe-oxide/SiO2 particles compared to bare SiO2. A higher affinity of Fe-oxide nanoparticles for MB adsorption facilitated the intra particle diffusion of MB molecules at a longer time of MB adsorption and improve the maximum MB adsorption capacities of Fe-oxide/SiO2 compared to bare SiO2. The maximum MB adsorption capacities of bare SiO2 and Fe-oxide/SiO2 particles reduced as the initial pH of MB solution increased, however, Fe-oxide/SiO2 particles always exhibited the higher capacity of MB adsorption than bare SiO2. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.