树枝状聚酰胺-胺接枝氧化石墨烯的制备及其对Cu(II)的吸附动力学与热力学

Preparation of graphene oxide modified by polyamide-amine and its adsorption thermodynamics and kinetics of adsorption for Cu(II)

摘要:

通过grafting-from法制备了聚酰胺-胺修饰的氧化石墨烯复合物(GO/PAMAMs)，并用红外光谱(FT-IR)、热重分析(TGA)和透射电子显微镜(TEM)进行了表征。研究了溶液pH值、吸附时间、吸附温度、Cu(II)初始浓度等因素对Cu(II)在GO/PAMAMs上吸附过程的影响，并研究了GO/PAMAMs对铜离子的吸附动力学和热力学。研究结果表明，GO/PAMAMs对Cu(II)的吸附过程符合Lagergren准二级动力学模型，主要为化学吸附。Langmuir和Freundlich等温模型均可以描述GO/PAMAMs对Cu(II)的吸附行为，说明Cu(II)在GO/PAMAMs上的吸附是单分子层吸附。自由能变(ΔG)，焓变(ΔH)和熵变(ΔS)均大于0，说明GO/PAMAMs对Cu(II)的吸附是吸热反应，非自发和熵增过程。

Abstract:

Graphene oxide (GO) was modified by polyamide-amine dendrimers (PAMAMs) via a grafting-from method, and then the GO/PAMAMs were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The effects of the solution pH, the adsorption time, temperature and the initial concentration of Cu(II) adsorption onto GO/PAMAMs were studied. The kinetics and thermodynamics of Cu(II) adsorption were investigated with the Lagergren pseudo-first-order and pseudo-second-order kinetic model, Langmuir and Freundlich isotherm models were applied to simulate the experimental data. The experimental data showed that the adsorption process of Cu(II) onto GO/PAMAMs can be described with the Lagrangian pseudo-second-order kinetics model, indicating the adsorption process is chemisorption mainly. The experimental data of isotherm followed both the Langmuir isotherm model and the Freundlich model, which indicated that the adsorption was monolayer. The thermodynamics parameters of Gibbs free energy change (ΔG), enthalpy changes (ΔH) and entropy change (ΔS) were calculated and found to be positive, indicating that the adsorption of Cu(II) onto GO/PAMAMs was endothermic, non-spontaneous and entropic-adding.