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

Magnetic porous Fe 3 O 4 /MRCS polymer composite was prepared by reacting melamine-formaldehyde resin with chitosan in the present of amino modified Fe 3 O 4 nanoparticles and used as adsorbent for acid red 18 azo dye removal. The Fe 3 O 4 /MRCS was characterized by TEM , SEM, XRD, TGA and BET analysis. The Fe 3 O 4 /MRCS possessed high BET surface area (226.6 m 2 /g), characteristic pore properties and facile magnetic separation function. The average pore width is 6.5 nm and the pore volume was 0.68 cm 3 /g. The Fe 3 O 4 /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 Fe 3 O 4 /MRCS showed superior adsorption performance for acid red 18 removal.