摘 要

磁性纳米粒子经过功能化处理后成为一种磁性复合材料，赋予其独特的物理化学性质，使其在催化、生物医疗和环境治理等领域中的应用前景广阔。本论文致力于探索提高磁核稳定性以及制备复合磁性材料用于重金属离子吸附和实现吸附剂分离。首先，通过共沉淀法成功制备出了Fe₃O₄纳米粒子，进一步经由异丙醇铝水解对其包覆Al₂O₃层，制得复合磁性载体Fe₃O₄@Al₂O₃；然后，对Fe₃O₄@Al₂O₃表面进行-SH改性，制得磁性Fe₃O₄@Al₂O₃-SH复合材料。运用XRD、SEM、N₂吸附-脱附、FT-IR、磁滞回线和UV紫外分光光度计等表征和测试手段，研究了典型样品的物相结构、形貌、织构性质、磁性能及其对水体中重金属Pb(II)的静态吸附性能，所得结果如下：

(1) 经由共沉淀法制备出的Fe₃O₄纳米粒子经Al₂O₃包覆之后比表面积降低，由原磁核的61.1 m²/g 降至25.3m²/g。磁性能测试表明，Fe₃O₄纳米粒子的饱和磁化强度达到76.97 emu/g，包覆Al₂O₃后的饱和磁化强度略有下降，但仍可通过外部磁场迅速的将其从体系中分离，为改性的后续分离提供支持。采用γ-巯丙基三甲氧基硅烷作为硅烷偶联剂改性Fe₃O₄@Al₂O₃，制得Fe₃O₄@Al₂O₃-SH。研究表明，-SH成功接枝，改性后样品的比表面积较低，颗粒表现为球形形貌。磁滞回线测试数据显示，接枝-SH后Fe₃O₄@Al₂O₃-SH的饱和磁化强度为73.26emu/g，虽较改性前有所下降，但仍具有较强磁性，可从溶液中分离。

(2) 对比研究改性前后样品Fe₃O₄@Al₂O₃和Fe₃O₄@Al₂O₃-SH应用于Pb(II)的吸附，探索了吸附过程中诸如溶液初始浓度、pH值、吸附剂投加量和吸附时间之类的要素对吸附效果的影响。研究表明，pH对改性后样品Pb(II)的吸附有很大影响，其对Pb(II)的去除率随pH的升高而降低最终达到某一稳定值，最佳pH为6-7；随着Pb(II)初始浓度的增加，所有样品均在Pb(II)初始浓度为100mg/L时达到饱和吸附，但改性后样品Fe₃O₄@Al₂O₃-SH对Pb(II)的去除率分别是Fe₃O₄、Fe₃O₄@Al₂O₃的2.43和6.92倍；随着复合磁性吸附剂Fe₃O₄@Al₂O₃-SH投加量的增加，Pb(II)的去除率逐渐升高，然后趋于稳定，最佳添加量为4.75g/L；改性后样品吸附速率较前两者也有所提升，约30min即可达到吸附平衡，而Fe₃O₄、Fe₃O₄@Al₂O₃需要45min才可达到吸附平衡；三个样品的吸附动力学更好地拟合二级动力学模，吸附等温线均符合Langmuir模型，改性后样品对Pb(II)的最佳吸附量为56.0mg/g，较改性前饱和吸附量提高6.83倍。

关键词：巯基改性；吸附剂；Fe₃O₄@Al₂O₃-SH；磁性分离；Pb(II)吸附

Abstract

Functionalized magnetic nanoparticles as magnetic composite, because of unique physical and chemical properties, have wide application in biomedicine, catalyst and environment protection. This thesis focuses on improving the stability of magnetic cores and preparing composite magnetic materials for heavy metal ion adsorption and attain separation of adsorbent. Firstly, Fe₃O₄ nanoparticles were successfully prepared via the coprecipitation method, then were coated by aluminum oxide with the hydrolysis of aluminum isopropoxide to prepare the composite magnetic supporter Fe₃O₄@ Al₂O₃. Magnetic adsorbents SH-Fe₃O₄@ Al₂O₃ were prepared by group modification. The phase structure, morphology, texture and magnetic properties of the typical adsorbents and their adsorption performance towards highly toxical Pb(Π) were also characterized by X-ray diffraction, scanning electron microscopy, N₂ adsorption-desorption, FT-IR, hysteresis loop and UV/Vis spectrophotometer.The results were as follows:

(1) The Fe₃O₄ nanoparticles prepared by coprecipitation method were coated with Al₂O₃, and the specific surface area was reduced，from 61.1 m²/g to 25.25m²/g.Magnetic measurements show the saturation magnetization of Fe₃O₄ nanoparticles was 76.97 emu/g, the saturation magnetization of coated Al₂O₃ decreased slightly. But by the external magnetic field it can rapidly separate from the system, to provide support for the subsequent separation and modification. Using MPTS as silane coupling agent modified Fe₃O₄@Al₂O₃, Fe₃O₄@ Al₂O₃-SH is prepared, and characterized by IR, SEM and other analytical methods. The results show that the surface area of the sample is lower and the spherical morphology of the sample . The result of vibrating sample magnetometer (VSM) shows that the saturation magnetization of the carrier is 73.26emu/g after modification of thiol group. Although it has decreased slightly, compared to the sample before modification, it still has strong magnetism and can be separated from solution.

(2) In contrast, samples of Fe₃O₄@Al₂O₃ and Fe₃O₄@Al₂O₃-SH were applied to Pb (II) adsorption before and after modification，the influence of such factors as the initial concentration of solution, pH value, adsorbent dosage and adsorption time on the adsorption effect was investigated. Results finding: the modified samples of Pb (II) adsorption was greatly affected by pH, the removal rate decreased with rising pH to reach a stable value, the best pH is 6-7; with the increase of Pb (II) initial concentration, all the samples in the initial Pb (II)concentration of 100mg/L reach saturated adsorption, but the modified sample of Fe₃O₄@Al₂O₃-SH for the removal rate of Pb (II) were respectively 2.43 and 6.92 times, compared with Fe₃O₄, Fe₃O₄@Al₂O₃; with the composite magnetic adsorbent dosage of Fe₃O₄@Al₂O₃-SH, Pb (II) removal rate gradually increased, and then tended to be stable, the optimal adding amount is 4.75g/L; adsorption rate of modified sample are also improved, about 30min could reach equilibrium, while Fe₃O₄, Fe₃O₄@Al₂O₃ requires 45min to reach adsorption equilibrium; adsorption kinetics of three samples are better fitting two order kinetics model and adsorption isotherm are consistent with the Langmuir model, the optimum adsorption amount of Pb (II) on the modified sample was 56.0mg/g, and the amount of saturated adsorption was 6.83 times higher than that before the modification.

Keywords: thiol modification; adsorbent; Fe₃O₄@Al₂O₃-SH; magnetic separation; Pb (II) adsorption.

目 录

摘 要 I

Abstract II