Facile synthesis of high performance porous magnetic chitosan - polyethylenimine polymer composite for Congo red removal

Abstract A new porous magnetic chitosan-polyethylenimine (Fe 3 O 4 /CS-PEI) polymer composite was synthesized by crosslinking chitosan (CS) with polyethylenimine (PEI) in the present of FeCl 3 ·6H 2 O and FeCl 2 ·4H 2 O in alkaline condition and applied to remove congo red (CoR) from aqueous solutions. The Fe 3 O 4 /CS-PEI composite was characterized by SEM, XRD, TGA and FT-IR analysis. The polymer composite owned high positive charge, large surface area, multi-level pore distribution and magnetic responsiveness. The porous magnetic Fe 3 O 4 /CS-PEI composite showed ultrahigh capacity (1876 mg/g) for CoR removal. It removed over 99.3% of CoR (100 mg/L) when the dosage was over 1.4 g/L. A higher temperature was benefit to CoR removal. The Fe 3 O 4 /CS-PEI composite was effective for CoR removal in a wide pH range (3–13). Kinetics studies suggested that the adsorption mechanism of CoR followed the pseudo-second model and it was also affected by the boundary layer diffusion. The adsorption process followed the Redlich-Peterson isotherm equation. Thermodynamic studies also demonstrated that this adsorption process was spontaneous, favorable and endothermic. The activation energy (E a ) of the adsorption process was 34.08 kJ/mol, indicating that chemisorption existed in the process. The results demonstrated that the porous magnetic Fe 3 O 4 /CS-PEI polymer composite is a promising adsorbent for the efficient removal of dye pollutants from aqueous solution.