Synthesis and adsorption properties of spongelike porous MnFe2O4

Spongelike porous MnFe2O4 (SPM) was synthesized by a sol–gel method with egg white. The obtained SPM was characterized and applied for the removal of methylene blue (MB) from aqueous solution in the batch system. The morphologies of SPM were spongelike porous bulks and the pore size could be controlled by the dosage of egg white. SPM showed good magnetic property at room temperature. In addition, SPM was suitable for adsorption due to its porous structure and high BET surface areas. The pseudo-second-order model described the adsorption kinetics well. FT-IR analysis suggested that –N+(CH3)2 of MB cations and the Fe–O bond of SPM were responsible for good adsorption. The adsorption equilibrium data fit Langmuir isotherm equation well with a maximum MB adsorption capacity of 20.67 mg/g. Moreover, SPM could be separated conveniently under a magnetic field (recovery ratio >98%) and reused seven cycles keeping a high activity (>96%). MB removal efficiencies of the last three cycles (99.5%) were even higher than that of the first four cycles. The results suggested that the SPM was a promising reusable adsorbent to remove MB form wastewater.