表面接枝端羟基聚酰胺-胺的磁性氧化石墨烯对Hg(Ⅱ)的吸附性能

Adsorption Behavior of Hg (Ⅱ) on the Hydroxyl-Terminated-Polyamidoamine-Grafted Magnetic Graphene Oxide

利用氯乙醇对合成的一系列接枝聚酰胺-胺树状高分子的磁性氧化石墨烯(MGO-PAMAM)进行端基的羟基化修饰,制备接枝端羟基聚酰胺-胺的磁性氧化石墨烯(MGO-PAMAM-OH)。通过透射电子显微镜、X射线衍射仪、傅里叶变换红外光谱仪、热重分析仪、振动样品磁强计和X射线光电子能谱仪对样品进行表征,考察了不同因素下MGO-PAMAM-OH对水溶液中Hg(Ⅱ)的吸附性能,并研究了其吸附动力学和等温吸附过程。测试结果表明,成功制备了一系列MGO-PAMAM-OH样品,其中,接枝3. 0代端羟基聚酰胺-胺的磁性氧化石墨烯(MGO-PAMAM-OH-G3. 0)样品对Hg(Ⅱ)的吸附性能最好,最大吸附量为129. 98 mg·g^(-1)。MGO-PAMAM-OH-G3. 0对Hg (Ⅱ)的吸附为发生在均质表面的单层化学吸附。此外,在吸附过程中MGO-PAMAM-OH-G3. 0将Hg(Ⅱ)部分还原为Hg(Ⅰ)。

In recent years,heavy metal pollution of industrial wastewater has become a serious threat to human health,living resources and ecological systems even at trace concentrations due to their non-biodegradability,high toxicity and bioaccumulation.Hg(Ⅱ)has been regarded as one of the most toxic and dangerous heavy metal ions,which is seriously harmful to renal and nervous systems.In our previous work,a series of magnetic graphene oxide samples grafted with polyamidoamine dendrimers(MGO-PAMAM)were prepared,which was expected to remove Hg(Ⅱ)from aqueous solution.In this study,the terminal groups of those MGO-PAMAM were modified using chlorohydrin,and consequently the corresponding magnetic graphene oxide grafted with hydroxyl-terminated polyamidoamine dendrimers(MGO-PAMAM-OH)were fabricated.The obtained samples were characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),thermogravimetry analysis(TG),vibrating sample magnetometer(VSM)and X-ray photoelectron spectroscopy(XPS).The ad sorption performances of the samples for Hg(Ⅱ)were studied by batch experiments.The effects of hydroxyl-terminated PAMAM generations,Hg(Ⅱ)initial concentration,solution pH value,and circumstance temperature on the adsorption performances of the samples for Hg(Ⅱ)were investigated in detail.The pseudo-first-order and pseudo-second-order kinetics rate equations were used to analyze the adsorption kinetics.The Langmuir isothermal and Freundlich isothermal adsorption models were employed to study the specific adsorption equilibrium.The results confirmed the successful synthesis of the MGO-PAMAM-OH samples,among which the 3.0-generation-hydroxyl-terminated-polyamidoamine-grafted magnetic graphene oxide(MGO-PAMAM-OH-G3.0)exhibits the most satisfactory adsorption-performance for Hg(Ⅱ),with a maximum adsorption capacity of 129.98 mg·g-1.The adsorption of Hg(Ⅱ)on MGO-PAMAM-OH-G3.0 coincides well with pseudo-second-order kinetics rate equation,and the adsorption equilibrium is in accord with Langmuir isothermal adsorption model,demonstrating a monolayer chemisorption beha-vior of Hg(Ⅱ)on homogeneous surface.In addition,the partial reduction of Hg(Ⅱ)ions to Hg(Ⅰ)by MGO-PAMAM-OH-G3.0 was observed in the adsorption process.Moreover,MGO-PAMAM-OH-G3.0 is superparamagnetic and the saturation magnetization can attain the requirement of solid-liquid separation.