Investigations On The Synthesis Of Porous Oxide Magnetic Nanoparticles, Surface Regulation And Surface Adsorption Properties

Magnetic nanoparticles are promising candidates in the removal of contaminants in the water and the area of nano-drug-loaded carrier due to their great adsorption capacity, magnetic separation properties as well as their propertities of directional movement in the applied magnetic field. As a result, a series of magnetic iron oxide nanoparticles with good adsorption capacities have been successfully synthesized. The adsorption capacities of the porous magnetic iron oxide nanoparticles for the removal of azo dyes and heavy metal ions were investigated. The effects of contact time, solution p H, ionic strength, and temperature on the adsorption behaviors were systematically investigated. Moreover, based on the kinetic and thermodynamic data, the adsorption mechanisms have been proposed. The main achievements and highlights are concluded as follow:(1) Porous magnetic Ni0.6Fe2.4O4 and Co0.6Fe2.4O4 nanoparticles were obtained through a two step method incorporating micro-emulsion process and following calcination of the precursor. The adsorption behaviors of Congo red(CR) and on Ni0.6Fe2.4O4 and Pb2+ on Co0.6Fe2.4O4 nanoparticles, were investigated as a function of contact time, p H, ionic strength and temperature. The results indicate that the adsorption kinetics of CR on Ni0.6Fe2.4O4 and Pb2+ on Co0.6Fe2.4O4 nanoparticles could be described by pesudo-second-order rate equation. The adsorption capacity of CR onto Ni0.6Fe2.4O4 decreases with the increasing temperature while the adsorption capacity of Pb2+ onto Co0.6Fe2.4O4 increased with the increasing temperature. The negative value of enthalpy(ΔH0) and the negative Gibbs free energy change(ΔG0) calculated from temperature dependent isotherms indicate that the adsorption of CR onto Ni0.6Fe2.4O4 is exothermic and spontaneous process under the experimental conditions applied. The positive value of enthalpy(ΔH0) and the negative Gibbs free energy change(ΔG0) calculated from temperature dependent isotherms indicates that the adsorption of Pb2+ onto Co0.6Fe2.4O4 is endothermic and spontaneous process under the experimental conditions applied. The adsorption of CR onto the Ni0.6Fe2.4O4 nanoparticles is implemented via electrostatic adsorption while the adsorption of Pb2+ onto the Co0.6Fe2.4O4 nanoparticles is implemented via the chemical ion-exchange mechanism.(2) The C@Fe3O4 composites were successfully prepared through a carbon-thermal process using the α-Fe2O3 as the starting material. Compared with magnetic iron oxide, α-Fe2O3 can be more facilely obtained. Two α-Fe2O3 samples with different morphologies(rod-like and disk-like) were employed as the starting material for the preparation of C/Fe3O4 composites absorbents. To validate the generality of this synthetic method, the commercially available α-Fe2O3 was also employed as the starting material for the preparation of the as the C/Fe3O4 composite absorbent. The adsorption behaviors of MB onto these absorbents were investigated as a function of contact time and temperature. The results indicates that the adsorption kinetic of MB onto these C/Fe3O4 composite absorbent could be described by the pesudo-second-order rate equation. Moreover, film diffusion mainly governs the rate-limiting process of adsorption of MB onto these C@Fe3O4 composite absorbants.