Synthesis And Metal Ion Absorption Property Of PEI Modified Magnetic Polymer Absorbents

Fe₃O₄ Magnetic nanoparticles were synthesized by modified coprecipitation method,and then modified with silane coupling agent and polyethyleneimine?PEI?,respectively.Finally PEI-modified magnetic nanoparticles was used to graft copolymerization with functional monomers to prepare PEI-modified magnetic polymer absorbent.Effects of synthesis parameters and absorption condition on heavy metal ions absorption performance for PEI-modified magnetic polymer absorbent were investigated.The structure of PEI-modified magnetic polymer absorbent were characterized by a variety of advanced characterization methods.Heavy metal ion adsorption kinetics and adsorption thermodynamics for PEI-modified magnetic polymer absorbent were studied.Magnetic responsiveness,heavy metal ion desorption and recycling performance of PEI-modified magnetic polymer absorbent were also discussed.Possible adsorption mechanism of heavy metal ions for PEImodified magnetic polymer absorbent was preliminarily discussed.The main experimental results were as follows:1.XRD indicated high crystallinity of magnetic nanoparticles,silane coupling agent –modified magnetic nanoparticles and PEI-modified magnetic nanoparticles.Polymer matrix of PEI-modified magnetic polymer adsorbent had amorphous structure,and magnetic Fe₃O₄ was dispersed in the polymer matrix with high crystalline structure.2.SEM showed that PEI-modified magnetic polymer adsorbent had rough and uneven surface with many porous and continuous groove structure,which was benificial to rapid infiltration and diffusion of heavy metal ions into the gel network of magnetic polymer adsorbent,making PEI-modified magnetic polymer adsorbent good absorption performance for heavy metal ions.3.FTIR spectra showed that the silane coupling agent and PEI were successful grafted onto the surface of magnetic nanoparticles,and PEI-modified magnetic polymer adsorbent had targeted structure.TGA indicated that the silane coupling agent and PEI were successful grafted onto the surface of magnetic nanoparticles,and PEI-modified magnetic polymer adsorbent had high magnetism and thermostability.4.Both magnetic nanoparticle dispersion,silane coupling agent modified magnetic nanoparticle dispersion and PEI modified magnetic nanoparticle dispersion had rapid magnetic responsiveness.Magnetic nanoparticle had saturation magnetization of 67.74 emu/g,whereas those of silane coupling agent modified magnetic nanoparticles and PEI modified magnetic nanoparticles decreased slightly,and PEI-modified magnetic polymer adsorbent decreased siginificantly.However,PEI-modified magnetic polymer adsorbent still has certain magnetic responsiveness.Both magnetic nanoparticle,silane coupling agent modified magnetic nanoparticle,PEI modified magnetic nanoparticle and PEI-modified magnetic polymer adsorbent are superparamagnetic.5.PEI-modified magnetic polymer adsorbent had maximum absorption performance of heavy metal ions in the condition of AA/ AM mass ratio of 60:40,AA neutralization degree of 70%,crosslinker amount of 0.75%,initiator amount of 0.8%,and PEI modified magnetic Fe₃O₄ nanoparticles amount of 15%.6.With the increase of pH and initial concentration of heavy metal ions,adsorption capacity of heavy metal ions such as Cu²⁺ and Cd²⁺,Pb²⁺ of PEI-modified magnetic polymer absorbent increased rapidly and then slowly.PEI-modified magnetic polymer absorbent had rapid absorption rate for heavy metal ions such as Cu²⁺ and Cd²⁺,Pb²⁺ and approached absorption equilibrium after 45 min.7.Adsorption process of heavy metal ions such as Cu²⁺ and Cd²⁺,Pb²⁺ for PEImodified magnetic polymer absorbent accorded with Langmuir adsorption models and pseudo-second kinetic equation.8.After 5 times recycling use,PEI-modified magnetic polymer absorbent had more than 85% desorption ratio of heavy metal ions such as Cu²⁺ and Cd²⁺,Pb²⁺ and 71.6%,72.1%,and 72.8% compared with absorption capacity of the first time use for Cu²⁺ and Cd²⁺,Pb²⁺,respectively.