Synthesis Of Polyacrylic Acid-Bound Iron Oxide Magnetic Nanoparticles And Study On Its Adsorption Property

A novel magnetic nano-absorbent has been developed by using resin modifying technology and nanometer magnetite (Fe₃O₄) syntheticism. The magnetic nano-absorbent is using Fe₃O₄ as cores and polyacrylic acid(PAA) as ionic exchange groups. Firstly, the Fe₃O₄ magnetic nanoparticles were prepared by chemical co-precipitation. Ammonia was chosen as precipitating agent, and was added to the mixed aqueous solution containing ferric and ferrous ions to produce nanometer Fe₃O₄ particles. Some influence factors on the size and characteristic of the product were investigated, and preliminary characterization was also performed. Secondly, thermo-gravimetric and differential thermal analyses, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy revealed the weight ratio of PAA bound to the magnetic nanoparticles and binding mechanism. In addition, TEM and XRD are used to investigate its characteristic changing. Finally, the adsorption of methylene blue (MB) from an aqueous solution by polyacrylic acid-bound iron oxide magnetic nanoparticles was studied. With the method of chemical co-precipitation, 10-20nm Fe₃O₄ nanoparticles were prepared under the condition when 0.5mol/L ammonia, 0.5mol/L iron ion , Fe²⁺:Fe³⁺:OH^-=1:1:6, 30℃ reaction temperature, 1000r/min stirring ratio was used. PAA was covalently bound onto the magnetic nanoparticles via carbodiimide activation. TGA DTA, FTIR, XPS analyses confirmed the binding of PAA to the magnetic nanoparticles, suggested a binding mechanism for the PAA, and revealed the maximum weight ratio of PAA bound to the magnetic nanoparticles was 0.12. In addition, TEM and XRD indicated formation of pure Fe₃O₄ superparamagnetic nanoparticles and the binding process did not significantly affect the size, structure and magnetic properties. The adsorption of methylene blue (MB) from an aqueous solution by polyacrylic acid-bound iron oxide magnetic nanoparticles was studied. In the aqueous solution of MB at 25℃, the adsorption data could be fitted by the Langmuir equation with a maximum adsorption amount of 0.198 mg/mg and a Langmuir adsorption equilibrium constant of 9.92 ml/mg. The adsorption capacity increased with the increase in solution pH (2-10) and the adsorption process was endothermic in nature with an enthalpy change (ΔH ) of 31.1 kJ/mol at 10-40℃. By using the methanol solution of acetic acid, the adsorbed MB could be desorbed. In addition, it was notable that both the adsorption and desorption of MB were quite fast and could be completed within 3 min due to the absence of internal diffusion resistance. It was shown that the magnetic nano-adsorbent was quite efficient for the adsorption/ desorption of MB.