Feasibility of using chemical co-precipitation and a high-gravity reactor with blade packings for continuous production of magnetite nanoparticles

Background: Magnetite nanoparticles (Higee-magnetite) were continuously produced using chemical co-precipitation and a high-gravity reactor with blade packings. Methods: A novel process for continuously producing Higee-magnetite involved an Fe2+ concentration of 0.15 mol/L with an Fe2+/Fe3+/OH- molar ratio of 1/2/8, an aqueous Fe2+/Fe3+ flow rate of 0.5 L/min, an aqueous OH- flow rate of 0.5 L/min, and a rotation speed of the high-gravity reactor of 1800 rpm. Significant findings: The mean crystalline size of Higee-magnetite was 11 nm. The average particle sizes of Higee-magnetite as determined using SEM and TEM were 23 nm and 9 nm, respectively. Higee-magnetite was superparamagnetic at 25 degrees C. The saturation magnetization of Higee-magnetite was 69 emu/g. The BET specific surface area, Langmuir specific surface area, and mean pore size of Higee-magnetite were 152 m(2)/g, 204 m(2)/g, and 10 nm, respectively. The rate of continuous production of Higee-magnetite was approximately 12 kg/day. Higee-magnetite had a much higher capacity for adsorbing Pb2+ than magnetite nanoparticles that had been produced in a batch reactor since it had a larger specific surface area. The Pb2+ adsorption isotherm of Higeemagnetite corresponded more closely to the Langmuir isotherm model than to the Freundlich isotherm model. Furthermore, consistent with the Langmuir isotherm model, Higee-magnetite had the maximum Pb2+ adsorption capacity of about 49 mg/g at 25 degrees C and pH 5. Therefore, Higee-magnetite is a favorable magnetic adsorbent for removing Pb2+ from water.