| With the development of industry,the unreasonable discharge of dye wastewater has brought great pressure to the environment.In view of the severe water dye pollution,the development of remediation method and technology for dye pollution water with low energy consumption,high efficiency,green environmental protection,and wide range application,has gained more and more people’s attention.In this paper,magnetic nanoparticles were prepared by modified coprecipitation method using ferric chloride,ferrous chloride and ammonia as raw materials,and then modified with silane coupling agent（KH570）.Finally KH570-modified magnetic nanoparticles were used to graft copolymerization with functional monomers to prepare magnetic polymer absorbent used for dye absorption.Effects of synthesis parameters such as initiator amount,crosslinker amount,AA neutralization,and amount of KH570-modified magnetic nanoparticles and absorption condition such as adsorption time,adsorption temperature,initial dye concentration and pH on cationic dye absorption capacity of magnetic polymer absorbent were investigated.The structure of magnetic polymer absorbent were characterized by various advanced characterization methods such as SEM,TEM,FTIR,XRD,VSM and TGA..Dye adsorption kinetics and adsorption thermodynamics of magnetic polymer absorbent were investigated.Dye desorption and recycling performance of magnetic polymer absorbent were studied.Possible adsorption mechanism of cationic dye for the magnetic polymer absorbent was preliminarily discussed.The main experimental results were as follows:1.Magnetic nanoparticles and silane coupling agent（KH570）–modified magnetic had irregular shape and high crystallinity with particle size between15–20 nm.Compared with magnetic nanoparticles,particle agglomeration decreased after silane coupling agent modification of magnetic nanoparticles.Polymer matrix of magnetic polymer adsorbent had amorphous structure.Both magnetic nanoparticles dispersion and KH570 modified-magnetic nanoparticles dispersion have obvious Tyndall phenomenon and rapid magnetic responsiveness.2.VSM showed that the saturation magnetization of the prepared magnetic Fe3O4 nanoparticles was 67.74 emu/g,and the saturation magnetization of KH570 modified magnetic nanoparticles slightly decreased.Although the saturation magnetization of magnetic polymer adsorbent decreased significantly,magnetic polymer adsorbent still had certain magnetic response properties.VSM diagram indicated that both residual magnetism and coercive force of magnetic nanoparticle,silane coupling agent modified magnetic nanoparticle and magnetic polymer adsorbent werealmost zero,indicating their superparamagnetism.3.SEM showed that magnetic polymer adsorbent had rough and uneven surface with many micropores,which wasbenificial to the rapid infiltration and diffusion ofdyes into the network of magnetic polymer adsorbent.4.FTIR spectra showed that the silane coupling agent（KH570）were successful grafted onto the surface of magnetic nanoparticles,and the magnetic polymer adsorbent had targeted structure.TGA indicated that the silane coupling agent was successful grafted onto the surface of magnetic nanoparticles,and the magnetic polymer adsorbent had high magnetic content and thermostability.5.Magnetic polymer adsorbent had maximum cationic dye absorption performance in the condition of KH570 modified magnetic nanoparticles amount of 30%,AA/ AM mass ratio of 60:40,initiator amount of 1.6%,crosslinker amount of 0.3% and AA neutralization degree of 70%.6.With the increase of absorption time,adsorption capacity of cationic dye for magnetic polymer absorbent increased firstly and then slowly,approaching equilibrium at 150 min.With the increase of pH,adsorption capacity of cationic dye for magnetic polymer absorbent increased firstly and then decreased secondly.With the increase of dye initial concentration,adsorption capacity of cationic dye for magnetic polymer absorbent increased rapidly and then slowly.Adsorption capacity of cationic dye for magnetic polymer absorbent decreased with increasing temperatures.7.Adsorption isotherm study showed that the adsorption process of methylene blue and crystal violet for the magnetic polymer adsorbent was in accordance with Langmuir monolayer adsorption model.The kinetic results showed that the adsorption process of methylene blue and crystal violet for the magnetic polymer adsorbent accorded with the quasi-second order kinetic adsorption.8.Recycling experiments of magnetic polymer absorbent showed that after 5 times recycling use,magnetic polymer absorbent had methylene blue adsorption capacity of 524 mg/g,accounting for 90% compared with methylene blue absorption capacity（583 mg/g）of the first time use,indicating its good recycling use performance. |
