Reusable cysteine-ferrite-based magnetic nanopowders for removal of lead ions from water

Abstract

Magnetic nanopowders were developed by functionalization of bimagnetic core@shell nanoparticles with cysteine (CoFe₂O₄@ɣ-Fe₂O₃@Cys), which present a core with high saturation magnetization (CoFe₂O₄) combined with a shell with high long-term chemical stability (ɣ-Fe₂O₃) and a sorptive L-cysteine layer. Samples of two different mean sizes were elaborated and characterized by XRD, TEM, FTIR, SER, zetametry and SQUID magnetometry. The adsorption of Pb(II) by the magnetic nanopowders was investigated as a function of pH, time, and pollutant concentration. The Langmuir model fitted well the adsorption data indicating monolayer adsorption, and a maximum adsorption capacity of 1.2 mg/g was found for pH 5. The kinetic data were well correlated to the pseudo-second-order model and the best equilibrium time was 120 min. The adsorption mechanism mainly involves electrostatic interactions in pH 5-7 and hard–soft-acid–base interactions in low pH. Moreover, the nanoparticles were recovered and reused in readsorption experiments keeping a good removal efficiency.

Keywords:
nanopowders; magnetic nanocomposite; magnetic separation; pollutant removal