Synthesis Of Fe₃O₄/PEI Adsorbent And Study On Adsorption Of Heavy Metal Ions And Dyes

Fe₃O₄ was synthesized by modified coprecipitation method,and then modif ied with silane coupling agent and polyethyleneimine?PEI?respectively.Finally PEI modified Fe₃O₄ was crosslinked with glutaraldehyde to prepare Fe₃O₄/PEI absorbent.Effects of adsorption conditions on the adsorption properties of hea vy metal ions and dye on magnetic polymer adsorbents were investigated.The structure of Fe₃O₄/PEI absorbent were characterized by a variety of modern c haracterization methods.Heavy metal ions and dye adsorption kinetics and adso rption thermodynamics for Fe₃O₄/PEI absorbent were studied.Magnetic responsi veness,desorption and recycling performance of Fe₃O₄/PEI absorbent were also discussed.Possible adsorption mechanism of heavy metal ions and anionic dy e for the Fe₃O₄/PEI absorbent was preliminarily discussed.The main experimen t results were as follows:1.Both magnetic nanoparticle dispersion,silane coupling agent modified Fe₃O₄ dispersion and PEI modified Fe₃O₄ dispersion had obvious Tyndall phenomenon and rapid magnetic responsiveness.2.FTIR spectra showed that the silane coupling agent and PEI were successful grafted onto the surface of Fe₃O₄,and both silane coupling agent modified Fe₃O₄ and PEI modified Fe₃O₄ had targeted structure.TGA indicated that the silane coupling agent and PEI were successfully grafted onto the surface of Fe₃O₄,and the Fe₃O₄/PEI absorbent had high magnetic content.3.TEM showed that Fe₃O₄,silane coupling agent modified Fe₃O₄ and PEI modified Fe₃O₄ had irregular particle shape with particle size between 15-20 nm.Particle agglomeration decreased after silane coupling agent and PEI modification of Fe₃O₄.XRD indicated that Fe₃O₄,silane coupling agent modified Fe₃O₄ and PEI modified Fe₃O₄ had characteristic diffraction peaks of magnetic nanoparticle and high crystallinity.4.Fe₃O₄ had saturation magnetization of 67.74 emu/g,whereas those of silane coupling agent modified Fe₃O₄,PEI modified Fe₃O₄ and Fe₃O₄/PEI adsorbent saturation magnetization decreased,but the reduction was not large,still has a high saturation magnetization,but the decrease not largeand,and they still had high saturation magnetization.Both residual magnetism and coercive force of Fe₃O₄,silane coupling agent modified Fe₃O₄ and Fe₃O₄/PEI absorbent were almost zero,indicating their superparamagnetism.5.With the increase of p H value,the adsorption capacity of heavy metal ions of Fe₃O₄/PEI adsorbents increased first and then decreased,and the adsorption capacity of methyl orange dyes decreased continuously.With the initial concentration increase of heavy metal ions and dyes,the adsorption capacity of the heavy metal ions adsorbed by the Fe₃O₄/PEI adsorbent increases rapidly and then increases slowly.And methyl orange dye adsorption capacity has been increased,Adsorption capacity of heavy metal ions and dye for Fe₃O₄/PEI adsorbent increased with increasing temperatures.6.Fe₃O₄/PEI adsorbent had high adsorption rate for adsorption of heavy metal ions and dye during the initial adsorption stage.With the increase of adsorption time,the adsorption of heavy metal ions and dyes increased,adsorption rate of adsorption of heavy metal ions and dye decreased and approached equilibrium at 90 min.7.The adsorption process of heavy metal ions and anionic dyes in Fe₃O₄/PEI adsorbents conforms to the quasi-second order kinetic equation and the Langmuir isothermal adsorption model.The adsorption process of metal ions and anionic dyes is the spontaneous process of increasing the enthalpy of enthalpy.8.After 5 times recycling use,the adsorption capacity of Fe₃O₄/ PEI adsorbent was about 80 % of the first adsorption capacity,and the adsorption capacity of methyl orange?165 mg/g?was the first adsorption capacity?182 mg/g?of 90 %.