Magnetic porous polymer composite for high performance adsorption of acid red 18 based on melamine resin and chitosan

Abstract Magnetic porous Fe3O4/MRCS polymer composite was prepared by reacting melamine-formaldehyde resinwith chitosan in the present of amino modified Fe3O4 nanoparticles and used as adsorbent for acid red 18 azo dye removal. The Fe3O4/MRCS was characterized by TEM, SEM, XRD, TGA and BET analysis. The Fe3O4/MRCS possessed high BET surface arear (226.6 m2/g), characteristic pore properties and facile magnetic separationfunction. The average pore width is 6.5 nm and the pore volume was 0.68 cm3/g. The Fe3O4/MRCS presented enhanced high adsorption performance toward acid red 18. It removed 99. 65% of acid red 18 (100 mg/L) when the adsorbent amount was over 0.8 g/L. It was found the absorption was depended on pH and the removal efficiency decreased with pH increased. The maximum adsorption capacity of acid red 18 reached as high as 301.0 mg/g. The adsorption kinetic followed the pseudo-second-order kinetics model and the activation energy of the adsorption process was 38.40 kJ/mol. The adsorption isotherms were best fitted to the Redlich–Peterson isotherm equation. Thermodynamic studies indicated the adsorption process was spontaneous and endothermic in nature. The adsorption mechanism study showed the adsorption was a heterogeneous chemisorption process with multiple interactions, involving pore filling, electrostatic attraction, affinity interaction, intra-particle diffusion, π-π interaction and polymer chain inclusion and polymer net trapping. In comparison with other reported adsorbents, the magnetic porous Fe3O4/MRCS showed superior adsorption performance for acid red 18 removal.