Adsorption Properties of Magnetic CoFe₂O₄@SiO₂ Decorated with P4VP Applied to Bisphenol A

In this study, the preparation and adsorption properties of cobalt ferrite core-shell nanoparticles coated with silica and decorated with poly(4-vinylpyridine) (CoFe₂O₄@SiO₂-P4VP) applied to bisphenol A (BPA) adsorption were described. The CoFe₂O₄-based core was coated by a nanometric layer of silica under Stöber conditions and followed by coating with poly(4-vinylpyridine) via surface polymerization in miniemulsion. The characterizations involved transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared (FTIR), thermogravimetry (TGA), dynamic light scattering (DLS) and zeta potential. The polymeric core-shell nanoparticle showed a spherical structure with a magnetic core of ca. 11 nm and a layer of silica of ca. 4 nm. The amount of poly(4 vinylpyridine) that decorated the nanoparticle surface was verified by thermogravimetric analysis. CoFe₂O₄@SiO₂-P4VP exhibited the capacity to adsorb bisphenol A. The chemometric model indicated a significant effect between the ionic strength and pH of the solution in the adsorption of bisphenol A. CoFe₂O₄@SiO₂-P4VP presented a superior adsorption capacity towards BPA (46.6 mg g^-1) in optimized conditions. The adsorption kinetics of BPA by CoFe₂O₄@SiO₂-P4VP involved a pseudo-second order process. Also, the adsorption isotherm indicated a multilayer process with data well-adjusted by Freundlich equation. The nanomaterial CoFe₂O₄@SiO₂-P4VP can be reused in adsorption of BPA for up to eight cycles.

Keywords:
adsorption; core-shell; nanoparticle; polymer