Amino-rich polymer-coated Fe–Fe2O3 nanoparticles with high adsorption capacity and rapid magnetic separation for anionic dye removal

The development of excellent dye adsorbent with high adsorption capacity and good separation function is imperative to clean the wastewater. Herein, an innovative magnetic Fe–Fe 2 O 3 @poly(cyclotriphosphazene- co -polyethyleneimine) (named as Fe–Fe 2 O 3 @PCP) composite was fabricated through a facile copolymerization between hexachlorocyclotriphosphazene and polyethyleneimine in the presence of Fe–Fe 2 O 3 nanoparticles. With the help of scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscope and vibrating sample magnetometer, the microstructure of the resulting magnetic Fe–Fe 2 O 3 @PCP composite was characterized. Then, the adsorption performance of magnetic Fe–Fe 2 O 3 @PCP composite was evaluated by removing anionic dye acid chrome blue K (ACBK) from aqueous solution. The effects of contact time, initial solution pH and temperature on the adsorption of ACBK onto magnetic Fe–Fe 2 O 3 @PCP composite were systematically studied. The kinetics, isotherms and mechanism of the adsorption process were analyzed. Results show that the maximum adsorption capacity of the magnetic Fe–Fe 2 O 3 @PCP toward ACBK dye could be up to 260 mg g −1 at 25 °C in neutral solution. The adsorption kinetics follows both the pseudo-second-order kinetic model and the Weber’s intraparticle diffusion model well. And the Freundlich isotherm model can nicely fit the adsorption equilibrium data. The electrostatic attraction between Fe–Fe 2 O 3 @PCP and ACBK plays a dominant role in the adsorption process. Moreover, the magnetic Fe–Fe 2 O 3 @PCP composite owns a high saturation magnetization of 30.1 emu g −1 , rendering it rapid magnetic separability and good reusability. After five adsorption–desorption cycles, the magnetic composite still kept 75% of removal efficiency with the adsorption capacity of 195 mg g −1 . The excellent adsorption capacity and good magnetic separability make the magnetic Fe–Fe 2 O 3 @PCP composite a promising adsorbent for efficient removal of anionic dyes including ACBK from contaminated wastewater.