Mussel-inspired magnetic adsorbent MnO2/PDA@Fe3O4 for removing heavy metal ions contaminants in single and mixed systems.

Heavy metal pollution has been a magnificent concern for a long period. A novel magnetic material, MnO2/PDA@Fe3O4, was prepared in this paper. With the assistance of multiple characterization methods, it was confirmed that polydopamine coated the magnetic nucleus and acted as a dense intermediate layer for MnO2 attachment. Having superior adsorption performance, MnO2/PDA@Fe3O4 could remove heavy metal cations efficiently no matter in single or mixed systems. The maximum adsorption capacities calculated by the Langmuir model for Pb(II), Cu(II), and Cd(II) were 295.01 mg/g, 130.30 mg/g, and 115.16 mg/g, respectively. In mixed systems, the adsorbent showed obvious selectivity for Pb(II). And the variation of Cu(II) concentration was more responsible for Pb(II) adsorption than that of Cd(II). The kinetic and thermodynamic data revealed that the polluted ions immobilizations by MnO2/PDA@Fe3O4 were chemisorption and were endothermic, entropy increase, spontaneous process. The presence of humic acid and coexisting ions induced only a very limited interference. In addition, MnO2/PDA@Fe3O4 maintained excellent adsorption performance and stability after five cycles of adsorption and removed 98.33% Pb(II) and 71.24% Cu(II) from actual water, respectively. This study confirmed that the MnO2/PDA@Fe3O4 had great potential and broad prospects to remediate the heavy metal contaminants in water.