Catecholamine coated maghemite nanoparticles for the environmental remediation: Hexavalent chromium ions removal

• Polydopamine coated maghemite nanoparticles were used to remove Cr(VI) ions.
• The effect of pH, Cr(VI) ion concentration and mixing time were investigated.
• The MNP@PDA can be used effectively in industrial wastewater treatment.
• The MNP@PDA could be easily harvested and repeatedly used.

In the present work polydopamine (PDA, i.e. catecholamine) coated maghemite nanoparticles (MNP) with strong magnetic attraction were successfully synthesized for easy separation and removal of Cr(VI) ions from aqueous solution. Factors influencing the uptake of Cr(VI) ions by the polydopamine/MNP core/shell (MNP@PDA) such as solution pH, initial Cr(VI) ion concentration, and mixing time were investigated systematically in batch mode experiments. The error analyses were performed using coefficient of determination (R2) and hybrid fractional error function (HYBRID), to determine the best-fitting kinetic model. Results showed that the kinetic data of adsorption of Cr(VI) ions on the synthesized nano-adsorbents is best described by a non-linear pseudo-second-order equation, indicating that the controlling step is the chemical adsorption. Desorption experiment showed that the regenerated adsorbent can be reused successfully in successive adsorption–desorption process cycles without significant loss of its original removal efficiency. The experiments revealed that nano-adsorbents can be considered as an effective, fast and dosage-saving materials in wastewater treatment and as well as in the industrial separation process of Cr(VI) ions by the adsorbing and bridging effect of PDA.

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