磁性纳米复合材料的制备及其对重金属离子的吸附性能研究

发布时间：2018-06-05 00:35

本文选题：重金属离子 + 磁性复合材料　；参考：《浙江大学》2017年博士论文

【摘要】：随着社会的发展和工业化进程的加快,水体中的重金属离子对生态的破坏以及对人类健康的危害越来越明显。纳米磁性复合材料因其独特的顺磁性、良好的生物相容性、稳定的化学性能、较高的吸附能力、容易回收利用等优势,成为目前国内外最具吸引力的吸附材料之一。根据这类材料的研究进展,还有许多问题需要我们继续深入探讨。如:磁性纳米复合材料的单分散性和稳定性、选择性吸附能力、再生和重复利用性和吸附机理研究等方面。本文以Fe3O4、CaFe2O4和CoFe2O4纳米磁性粒子作为复合材料的磁性部分进行了制备和表征。考虑到材料的化学稳定性、制备方法的简单易控性以及适宜的磁性能,我们选择CoFe2O4作为复合材料的磁性成分,SiO2为非磁性成分,设计了不同形貌的核壳结构和多孔结构等材料体系。将制得的纳米磁性复合材料有效的应用于吸附水中的重金属离子,研究了吸附动力学、吸附热力学、吸附平衡、吸附剂的再生重复利用等,为此类复合材料的实际应用奠定了基础。主要研究内容如下:(1)制备了一种功能化的链状核壳磁性纳米复合材料(CoFe2O4@SiO2-NH2)并将其成功应用于对水溶液中重金属离子(Cu(Ⅱ)、Cd(Ⅱ)和Mn(Ⅱ))的吸附。这种功能化的磁性复合材料是由无定形Si02外壳和CoFe2O4磁性核构成。具有较高的饱和磁化强度(28.09emu/g),可在磁场作用下快速分离。对水溶液中的重金属离子Cu(Ⅱ)、Cd(Ⅱ)和Mn(Ⅱ)的平衡吸附容量分别为170.83、144.95和110.80 mg/g。此外,此磁性复合材料对重金属离子的吸附过程更符合准二级动力学和Langmuir等温模型,说明吸附主要为化学吸附。由于吸附受pH影响很大,我们利用盐酸使吸附剂再生,经四次循环使用后利用率仍可达到85.41%。说明此磁性吸附剂可潜在应用于重金属废水处理方面。(2)合成了一种氨基改性的超顺磁性CoFe2O4@SiO2单分散核壳纳米球,并研究了其对水体中重金属离子的吸附性能。此纳米球由磁性核CoFe2O4(～10 nm)和二氧化硅层(～35 nm)以及氨基功能化层构成。这种单分散的纳米球由于大的比表面积,能够嫁接较多的氨基基团,提高对重金属离子(Cu(Ⅱ)、Cd(Ⅱ)和Pb(Ⅱ))的吸附能力。纳米球的吸附过程可以很好的用Langmuir模型描述,通过线性拟合得出对Cu(Ⅱ)的单分子最大吸附容量为410.72 mg/g。吸附动力学符合准二级动力学模型,说明吸附为化学吸附。吸附热力学分析表明吸附过程为自发的并且吸热的。经酸处理后得到再生吸附剂,重复使用5次后,吸附剂对Cu(Ⅱ)、Cd(Ⅱ)和Pb(Ⅱ)的去除率影响不大,并且仍可保持结构和磁性的稳定性。因此,这种单分散的超顺磁性纳米球能够高效的去除水溶液中的重金属离子。(3)制备了一种多孔磁性纳米复合材料CoFe2O4/SiO2,氨基功能化后,用于高效去除水溶液中重金属离子。这种复合材料的制备方法简单易控,且产率较大,利于产业化应用。制备的多孔CoFe2O4/SiO2的比表面积为167.51 m2/g。考虑到实际废水中共同存在多种重金属离子,我们研究了材料在单离子和混合离子溶液中对重金属离子Cu(Ⅱ)、Mn(Ⅱ)、Cd(Ⅱ)和Pb(Ⅱ)的吸附。结果表明此吸附剂对重金属离子的吸附能力不受其他竞争离子的影响,都表现出较大的吸附容量和较高的去除率(90%)。吸附机理通过Langmuir吸附等温线模型、准二级吸附动力学模型进行线性拟合以及吸附热力学分析。结果表明,这种功能化的多孔磁性复合材料的优良吸附性能归因于强的表面络合作用和其特殊的化学结构。
[Abstract]:With the development of society and the accelerated process of industrialization, the destruction of heavy metal ions in the water body and the harm to human health are becoming more and more obvious. Nano magnetic composite material has become the present because of its unique paramagnetic, good biocompatibility, stable chemical properties, high adsorption capacity and easy recovery and utilization. One of the most attractive adsorption materials at home and abroad. According to the research progress of this kind of materials, many problems need to be further discussed. For example, the monodispersity and stability, selective adsorption capacity, regeneration and reutilization and adsorption mechanism of magnetic nanocomposites are studied in this paper, Fe3O4, CaFe2O4 and CoFe2O4 nanoscale. Magnetic particles of rice are prepared and characterized as the magnetic parts of the composites. Considering the chemical stability of the materials, the simple controllability and the suitable magnetic properties of the preparation methods, we choose CoFe2O4 as the magnetic component of the composite and the non magnetic component of SiO2, and designs the materials with different morphologies, such as the shell structure and the porous structure. The nano magnetic composites are effectively applied to the heavy metal ions in the adsorbed water. The adsorption kinetics, adsorption thermodynamics, adsorption equilibrium and reutilization of adsorbents have been studied. The main research contents are as follows: (1) a functional chain core shell is prepared. Magnetic Nanocomposites (CoFe2O4@SiO2-NH2) have been successfully applied to the adsorption of heavy metal ions (Cu (II), Cd (II) and Mn (II)) in aqueous solution. This functional magnetic composite is composed of amorphous Si02 shell and CoFe2O4 magnetic core. It has high saturation magnetization (28.09emu/g) and can be separated rapidly under the action of magnetic field. The equilibrium adsorption capacity of heavy metal ions Cu (II), Cd (II) and Mn (II) in aqueous solution is 170.83144.95 and 110.80 mg/g. respectively. The adsorption process of the magnetic composite on heavy metal ions is more consistent with the quasi two order kinetics and Langmuir isothermal model, indicating that the adsorption is mainly chemisorption. Because adsorption is greatly influenced by pH, we have a great effect on adsorption. Using hydrochloric acid to regenerate the adsorbent, the utilization rate of the adsorbent can still reach 85.41%. after four cycles. It shows that the magnetic adsorbent can be applied to the treatment of heavy metal wastewater. (2) a kind of amino modified superparamagnetic CoFe2O4@SiO2 monodisperse nuclear shell nanospheres have been synthesized, and the adsorption properties of heavy metal ions in water are studied. The rice ball is made up of magnetic core CoFe2O4 (~ 10 nm) and silica layer (35 nm) and amino functional layer. This monodisperse nano ball can grafted more amino groups and improve the adsorption capacity of heavy metal ions (Cu (II), Cd (II) and Pb (II)) by large specific surface area. The adsorption process of nanospheres can be well used in Langmuir The model describes the maximum adsorption capacity of the single molecule of Cu (410.72 mg/g.) by linear fitting. The adsorption kinetics is in accordance with the quasi two class kinetic model, which indicates that the adsorption is chemical adsorption. The adsorption thermodynamics analysis shows that the adsorption process is spontaneous and endothermic. After the acid treatment, the adsorbent is reused for 5 times and the adsorbents are reused for 5 times. The removal rate of Cu (II), Cd (II) and Pb (II) has little effect, and the stability of the structure and magnetic properties can still be maintained. Therefore, the monodisperse superparamagnetic nanospheres can effectively remove heavy metal ions in the aqueous solution. (3) a porous magnetic nano composite material CoFe2O4/SiO2 is prepared. After the amino function is functionalized, it is used to efficiently remove water. The preparation of heavy metal ions in the solution is simple and easy to control, and the yield is large, which is beneficial to the industrial application. The specific surface area of the porous CoFe2O4/SiO2 is 167.51 m2/g., considering the common presence of heavy metal ions in the actual wastewater. We studied the heavy metal ions in the single and mixed ion solutions. The adsorption of Cu (II), Mn (II), Cd (II) and Pb (II) shows that the adsorbability of the adsorbent on heavy metal ions is not affected by other competitive ions, and shows a larger adsorption capacity and higher removal rate (90%). The adsorption mechanism is linear and absorbable by Langmuir adsorption isothermal model and quasi two order adsorption kinetic model. The results show that the excellent adsorption properties of this functionalized porous magnetic composite are attributed to the strong surface complexation and its special chemical structure.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1;O647.3

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