Study On Preparation Of Magnetic Polymer Microspheres

The preparation of magnetic polymer microspheres and their application asadsorbents for heavy metal ions were studied in this thesis.Firstly, the Fe₃O₄nanoparticles were successfully prepared by coprecipitation inthe presence of oleic acid with which the surface properties of Fe₃O₄was modified.Secondly, the magnetic polymer microspheres containing Fe₃O₄nanoparticles wereproduced by miniemulsion polymerization. The structure and properties werecharacterized through FTIR, TGA, XRD, TEM, SEM and magnetic testing system.The results show that Fe₃O₄nanoparticles obtained through coprecipitation has atypical inverse spinel structure with a diameter of about10nm. The structure and thesize of the nanoparticles remain unchanged after polymerization. Oleic acid takes twoabsorption layers in the surface of Fe₃O₄nanoparticles. The modified Fe₃O₄showshigh magnetic saturation （Ms） which is42.63emu/g. The Magnetic polymermicrospheres were prepared under different polymerization conditions. It is found thatthe magnetic nanocomposite polymer microspheres from droplet nucleation are withlarger size and pure polymer microspheres from homogeneous nucleation are withsmaller size and both are inevitably produced. Meanwhile, the bared magneticnanoparticles are observed in case of high dosage of Fe₃O₄nanoparticles.The adsorption properties of the magnetic adsorbents with carboxyl groups onthe surface for Cu²⁺as adsorbate were investigated. The adsorption mechanism andkinetics as well as the effects of various factors including initial pH, Cu²⁺concentration, temperature and carboxyl contents on the adsorption capacity of themagnetic adsorbent were discussed. It is found that the properties of magneticadsorbents is highly dependent on the pH of the solution and the adsorption capacityincreases with temperature, carboxyl contents and the concentration of Cu²⁺. However,the removal efficiency of Cu²⁺decreases with increasing the concentration of Cu²⁺.The adsorption of Cu²⁺is fitted to both the Langmuir and Freundlich isothermalmodel. It can be found that the adsortion process agrees to Lagergrenpseudo-second-order kinetic model but not agrees to Lagergren pseudo-first-orderkinetic model. By monitering the pH change in the adsorption process, it indicatesthat the driving forces of the absorption are mainly electrostatic attraction, ionexchange and physical adsorption. The removal efficiency of Cu²⁺increases from82.6%to95.36%and the saturated adsorption capacity （qe） increases from16.276mg/g to18.79mg/g by adjusting the pH to reach the adsorption equilibrium.