A Novel Process for Magnetic NiFe2O4 Nanoparticles and Their Adsorption Characteristics of Methyl Orange

A novel sol combustion and gel calcination process for the preparation of magnetic NiFe2O4 nanoparticles was introduced, the gel precursor and resultant products were characterized by TG/DSC, XRD, SEM, TEM and BET techniques. The results show that the single ferrite phase of NiFe2O4 is formed at 400 degrees C, the volume of the solution and the calcination temperature are two key factors to the average grain size of magnetic NiFe2O4 nanoparticles. With the calcination temperature increasing from 400 degrees C to 800 degrees C, the average grain size of NiFe2O4 obtained with absolute alcohol of 15 mL increases from 12.2 nm to 37.8 nm, and the specific saturation magnetization increases from 35.0 Am-2/kg to 416.9 Am-2/kg; while, with the volume of absolute alcohol increasing from 15 mL to 30 mL, the average grain size of NiFe2O4 calcined at 400 degrees C for 2 h increases from 12.2 nm to 14.7 nm, and the specific saturation magnetization increases from 35.0 Am-2/kg to 77.1 Am-2/kg. b, the pseudo-second-order kinetic model is well fitted to describe the MO adsorption process within a range of initial concentration of 50-250 mg/L; Freundlich and Temkin models well fit the adsorption isotherm of MO onto the magnetic NiFe2O4 nanoparticles, which reveals that the adsorption of MO onto the magnetic NiFe2O4 nanoparticles was a hybrid of monolayer and multilayer absorbing mechanism.