Synthesis of polyethylenimine-functionalized magnetic materials and a critical evaluation of the removal of copper in sediments

The magnetic materials M-PEI and M-G-PEI were prepared through polyethylenimine (PEI)-adhered magnetic Fe₃O₄, and covalence-crosslinked strategies, respectively. The amount (7 mg/g) of polyethylenimine adsorbed and combined on the surface of Fe₃O₄ was measured. The adsorption behavior of M-PEI and M-G-PEI to Cu²⁺ is more favorable at a neutral pH, with an optimum adsorption when pH is 6. The adsorption rate is more than 90% and was enhanced by increasing the adsorbent to Cu²⁺ ratio. Langmuir and Freundlich isotherm models were used to evaluate Cu²⁺ adsorption capacity on the material of M-PEI and M-G-PEI. The results show the excellent adsorption capacity for Cu²⁺ of M-G-PEI and it is greater than that of M-PEI. The adsorption kinetics experiment indicated that the adsorption of Cu²⁺ on sorbents adhered to first-order kinetics. Overall, the amino containing magnetic material shows a clear potential to treat Cu²⁺ contaminates, due to the high adsorption capacity (q_e = 126 and 120.9 mg/g for M-G-PEI and M-PEI, respectively) quickly (< 30 min). Additionally, the binding stoichiometry of M-G-PEI and M-PEI was 8.92 × 10⁶ and 4.15 × 10⁶, respectively, and the dissociation constant of M-G-PEI and M-PEI was 1.2983, and 0.6575 mmol/L, respectively. More than 80% of the Cu²⁺ was removed from contaminated sediment using the magnetic absorbent. The adsorbents were used to rehabilitate the sediment contaminated by Cu²⁺. These findings suggest that polyethylenimine-functionalized magnetic materials are highly efficient as alternative materials to remove heavy metals from sediments.