ABSTRACT

In order to solve the water solubility and difficult re-use of plant polyphenol (PP) in Cd(II) adsorption, PP was immobilized on the surface of magnetic material in this study. A core-shell nanocomposite Fe₃O₄/SiO₂/PP (∼18 nm) was synthesized with 3–8 nm SiO₂ and 2–5 nm PP. TGA analysis revealed the PP coating amount was 2.39%. VSM detection suggested that saturation magnetization of Fe₃O₄/SiO₂/PP was 45.94 emu/g. The adsorption equilibrium was reached in 2 h and the adsorption kinetics followed a pseudo-second-order model. The adsorption data fitted well to a Langmuir isotherm, achieving a 98.6% of Cd(II) removal at 0.6 g, pH 7.0, 298 K and 160 rpm. The adsorption capacity of Cd(II) on Fe₃O₄/SiO₂/PP highly depended on the pH. The adsorption capacity increased as the initial solution pH was increased in the range of 3.0–8.0. The adsorbed Cd(II) on Fe₃O₄/SiO₂/PP could be effectively desorbed by 0.1 mol/L of HNO₃ and the Fe₃O₄/SiO₂/PP still maintained a stable adsorption capacity after five cycles. The adsorption mechanism of Cd(II) on Fe₃O₄/SiO₂/PP is mainly dependent on complexation and electrostatic adsorption from the FTIR and XPS analyses. This study provided a new way for PP to remove Cd(II) from aqueous solution.

摘要

为了解决植物多酚(PP)在吸附Cd(II)中的水溶性和难以再利用的问题，本研究将PP固定在磁性材料的表面。_{用 3-8 nm SiO 2}和 2-5 nm PP合成核壳纳米复合材料 Fe ₃ O ₄ /SiO ₂ /PP（~18 nm） 。TGA分析显示PP涂层量为2.39%。VSM检测表明Fe ₃ O ₄ /SiO _{2的饱和磁化强度}/PP 为 45.94 emu/g。在 2 h 内达到吸附平衡，吸附动力学遵循准二级模型。吸附数据很好地符合 Langmuir 等温线，在 0.6 g、pH 7.0、298 K 和 160 rpm 下实现了 98.6% 的 Cd(II) 去除。Cd(II)对Fe ₃ O ₄ /SiO ₂ /PP的吸附能力很大程度上取决于pH值。随着初始溶液 pH 值在 3.0-8.0 范围内增加，吸附容量增加。_{Fe 3} O ₄ /SiO ₂ /PP上吸附的 Cd(II)可被 0.1 mol/L HNO ₃和 Fe ₃ O ₄ /SiO _{2有效解吸}/PP 在五次循环后仍保持稳定的吸附能力。Cd(II) 在 Fe ₃ O ₄ /SiO ₂ /PP 上的吸附机理主要取决于 FTIR 和 XPS 分析的络合和静电吸附。该研究为PP从水溶液中去除Cd(II)提供了一种新途径。