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.本研究系统阐述了以双酚A（bisphenol A, BPA）吸附为应用目标的、经二氧化硅包覆并接枝聚(4-乙烯基吡啶)（poly(4-vinylpyridine)）的钴铁氧体核壳纳米颗粒（CoFe₂O₄@SiO₂-P4VP）的制备方法与吸附性能。该材料以钴铁氧体为核，先通过斯托伯法（Stöber）在核表面包覆纳米级二氧化硅层，随后通过细乳液表面聚合法接枝聚(4-乙烯基吡啶)。所采用的表征手段包括透射电子显微镜（Transmission Electron Microscopy, TEM）、X射线衍射（X-ray Diffraction, XRD）、振动样品磁强计（Vibrating Sample Magnetometer, VSM）、傅里叶变换红外光谱（Fourier Transform Infrared, FTIR）、热重分析（Thermogravimetry, TGA）、动态光散射（Dynamic Light Scattering, DLS）以及Zeta电位分析。所制备的核壳纳米颗粒呈球形结构，其磁核粒径约为11 nm，二氧化硅层厚度约为4 nm。通过热重分析测定了纳米颗粒表面接枝的聚(4-乙烯基吡啶)负载量。CoFe₂O₄@SiO₂-P4VP具备双酚A吸附能力。化学计量学模型表明，溶液离子强度与pH值对双酚A的吸附过程存在显著影响。在优化实验条件下，CoFe₂O₄@SiO₂-P4VP对双酚A的吸附容量可达46.6 mg·g⁻¹，吸附性能优异。CoFe₂O₄@SiO₂-P4VP对双酚A的吸附动力学行为符合准二级动力学过程。此外，吸附等温线拟合结果表明，该吸附过程为多层吸附，实验数据与弗罗因德利希（Freundlich）方程拟合度极佳。该纳米材料CoFe₂O₄@SiO₂-P4VP可循环用于双酚A吸附，循环使用寿命可达8次。