| In this paper,magnetic nanoparticles were synthesized by modified coprecipitation method,and then modified with chitosan to prepare chitosan-modified magnetic nanoparticles.Finally chitosan-modified magnetic nanoparticles were used to graft copolymerization with aniline and O-aminobensulfonic acid to synthesize magnetic chitosan/polyaniline absorbents by chemical oxidation polymerization.Effects of synthesis parameters and absorption condition on heavy metal ion absorption capacity of magnetic polymer absorbent were investigated.The structure and morphologies of magnetic nanoparticles,chitosan-modified magnetic nanoparticles and magnetic chitosan/polyaniline absorbents were characterized by Uv/vis,TEM,TGA,SEM,FTIR,XRD.Magnetic properties of magnetic nanoparticles,chitosan-modified magnetic nanoparticles and magnetic chitosan/ polyaniline absorbents were also investigated.Effects of polymerization parameters and adsorption condition on the adsorption properties of lead ion,methyl orange and methylene blue were studied.Heavy metal ion and dye adsorption kinetics and adsorption thermodynamics of magnetic chitosan/polyaniline absorbents were investigated.Heavy metal ion desorption and recycling performance of magnetic polymer absorbent were studied.Magnetic chitosan/ polyaniline adsorbents with porous structure and various adsorption groups had fast adsorption rate,large adsorption capacity,easy magnetic solid-liquid separation and easy reutilization.The main experimental results were as follows:1.TEM indicated tha magnetic nanoparticles and chitosan-modified magnetic nanoparticles had irregular shape with particle size between 15-25 nm.Particle agglomeration decreased after chitosan modification of magnetic nanoparticles.SEM showed that magnetic chitosan/polyaniline absorbents had rough surface with many unevenly sized pores.2.Magnetic nanoparticle had saturation magnetization of 67.8 emu/g,whereas those of chitosan-modified magnetic nanoparticles decreased slightly and magnetic chitosan/ polyaniline adsorbents decreased siginificantly.However,magnetic chitosan/ polyaniline adsorbents still had certain magnetic responsiveness.Both magnetic nanoparticle,chitosan-modified magnetic nanoparticles and magnetic chitosan/ polyaniline adsorbents had near zero residual magnetism and coercivity.Both magnetic nanoparticles dispersion and chitosan-modified magnetic nanoparticles dispersion had Tyndall phenomenon.3.FTIR indicated that the prepared magnetic chitosan/ polyaniline adsorbents had the target structure.XRD showed that the polyaniline matrix had amorphous structure After graft-copolymerization of chitosan-modified magnetic nanoparticles with aniline and aniline derivatives,the crystal type and structure of the magnetic nanoparticles did not change during oxidation polymerization.TGA showed that the coverage degree of chitosan onto the magnetic nanoparticles surface was 5.3%.4.Magnetic chitosan/polyaniline absorbents had maximum absorption property of methylene blue dye in the condition of chitosan-modified magnetic nanoparticles amount of 15%,monomer concentration of 10%,aniline/ O-aminobensulfonic acid mass ratio of 8:2,and ammonium persulfate amount of 1:1.Magnetic chitosan/polyaniline absorbents had maximum absorption property of methyl orange dye in the condition of chitosan-modified magnetic nanoparticles amount of 15%,monomer concentration of 10%,aniline/ O-aminobensulfonic acid mass ratio of 8:2 and ammonium persulfate amount of 1.25:1 Magnetic chitosan/polyaniline absorbents had maximum absorption property of lead ions in the condition of chitosan-modified magnetic nanoparticles amount of 15%,monomer concentration of 10%,aniline/ O-aminobensulfonic acid mass ratio of 6.5:3.5,and ammonium persulfate amount of 1.25:1.5.Adsorption process of methyl orange dye for magnetic chitosan/polyaniline absorbents accorded with mutiplelayer Freundlich adsorption model,whereas that of methylene blue dye accorded with monolayer Langmuir adsorption model.Both kinetic absorption process of methyl orange and methylene blue for magnetic chitosan/polyaniline absorbents accorded with pseudo-second kinetic equations.6.After 5 times recycling use,magnetic chitosan/polyaniline absorbents had more than 8090% desorption ratio of heavy metal ion and dyes,and more than 80% compared with absorption capacity of the first time use for heavy metal ion and dyes.This indicated that magnetic chitosan/ polyaniline adsorbents had good desorption and recycling properties. |
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