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

Abstract

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.

Core–Shell Chitosan Cobalt Ferrite Nanoparticles for Ultrasensitive Simultaneous Voltammetric Determination of Pb(II) and Cd(II)

“…The VSM curve for naked CoFe 2 O 4 nanoparticles presents hysteresis with a remanence of 15.1 emu g –1 and a coercivity of 426 Oe. These indicate a ferrimagnetic behavior because at room temperature CoFe 2 O 4 shows constant magnetization. , This behavior is in line with some studies already reported in the literature where CoFe 2 O 4 has high coercivity and is classified as a hard ferrite. The decrease in the M S value of CoFe 2 O 4 @CTS (Table ) can be attributed to the combination of surface effects.…”

“…The average crystallite size remains nearly unaltered after the formation of the nanocomposite when considering the diameter obtained by XRD. , The presence of solvent and counterions increases the diameter compared to TEM and XRD measurements. TEM provides a statistically small sample, and XRD provides data on the constructive interference of X-rays scattered by periodic lattice planes of a sample. , XRD and DLS also display the diameters of the particles. The values showed discrepancies with the values obtained by the TEM analysis (see Table ), so each technique reveals different aspects of the particles.…”

“…The diameter of TEM and the hydrodynamic radius in the collapsed state in which the polymer is found are d TEM / d DLS = 0.67. In the work of Clara-Rahola et al, nanosystems are characterized by a dense core and a lighter shell and portray the nature of d TEM mass distribution and d DLS dynamics, due to particle distribution in the medium. , …”

“…Finally, ultrapure water was added to form the ferrofluid. The resultant CoFe 2 O 4 was dried for 24 h at 70 °C …”

“…Furthermore, these nanocomposites have proven useful as contrast agents in magnetic resonance imaging, serving as magnetic markers for medical diagnosis . CTS core–shell nanoparticles have been explored as an excellent material for adsorption and environment removal of divalent metal cations such as Cu(II), Cd(II), and Cd(II). , Indeed, CTS can coordinate metal ions forming chelate complexes due to the interactions with −OH and −NH 2 groups . Hence, nanomaterials covered with CTS can present a high number of functional sites for analyte interaction.…”