【作者】 李海波；

【导师】 毕韶丹；

【作者基本信息】 沈阳理工大学 ， 环境工程， 2011， 硕士

【摘要】 磁性壳聚糖具有良好的吸附性能,适于大规模吸附,且易于改性和再用。本课题考察了磁性壳聚糖及胺化羧甲基磁性壳聚糖对不同重金属离子的吸附分离性能。从磁性再生、吸附实验条件、热力学和动力学数据拟合、多元离子分离等多个方面,研究了磁性壳聚糖及其改性产品对重金属离子的吸附特性。利用化学共沉淀法制备了Fe₃O₄。考察了Fe³⁺与Fe²⁺摩尔比、溶液碱度和表面活性剂用量对Fe₃O₄成核过程的影响。制备的Fe₃O₄具有超顺磁性,容易单分散。利用戊二醛交联Fe₃O₄与壳聚糖制备了磁性壳聚糖微球。通过单因素和正交实验优化,制备的磁性壳聚糖粒径在220μm左右、表面均布10nm～22nm孔隙。通过优化溶液温度、pH、离子浓度等吸附条件,磁性壳聚糖对100mg/L铜离子的吸附容量能够达到68.9mg/g。利用快速简单的微波加热方法,先用氯乙酸羧甲基化磁性壳聚糖,再用二乙烯三胺胺化羧甲基产品,合成了胺化羧甲基磁性壳聚糖。产品的粒径和孔径与磁性壳聚糖大小相当,磁性能稳定。胺化后产品的C₂-NH₂含量大幅增加,化学吸附能力提高,其对100mg/L的Pt4+、Cr⁶⁺和Cu²⁺的吸附容量均超过110mg/g。解吸再生6次,吸附容量仍保持在80%以上。磁性壳聚糖、胺化羧甲基磁性壳聚糖对金属离子的吸附研究表明:在60mg/L～1600mg/L离子浓度条件下,吸附6小时达到平衡。使用四个热力学和三个动力学模型拟合分析实验数据。其中,Freundlich和Generalized热力学模型、Pseudo二级动力学模型相关性最高。吸附过程为:短时间内为极不稳定的单层吸附;之后发生多层吸附和柱填充;继续延长吸附时间,吸附剂官能团与金属离子的化学结合力逐渐稳固,吸附容量稳步增加,最终达到吸附平衡。灵活调节pH,磁性壳聚糖再用7次,可将430mg/L的铜铅二元离子选择性分离;胺化羧甲基磁性壳聚糖可将200mg/L的铜锌铬三元离子溶液选择性分离。更多还原

【Abstract】 Magnetic chitosan beads were prepared by cross-linking Fe₃O₄ and chitosan with glutaraldehyde. Then magnetic amination chitosan beads were synthesized with diethylenetriamine. The products were used to study the adsorption capacity for various of heavy metal ions, such as Cu²⁺, Pb²⁺, Zn²⁺ and Cr⁶⁺. The effects of contact time, initial ion concentration, PH and temperature of the ion solution were discussed. And the selective adsorption of multicomponent ions solution was investigated by the products.The magnetic chitosan beads had sufficient magnetism to separate and collect themselves from water solution. By SEM and BET, the magnetic chitosan beads were spherical, and there was plenty of mesoporous on the surface. The structure of the product was characterized by FT-IR. The C₂-NH₂ and C₆-OH were the functional groups in the magnetic chitosan for the adsorption of heavy metal ions. The 430 mg/L Cu²⁺ and Pb²⁺ mixed solution was selectively separated by using the magnetic chtitosan beads. The adsorption capacity of the magnetic chitosan for the metal ions kept 80.6% after 7 times reuse.Compared with the magnetic chitosan, the magnetic amination chitosan had more C₂-OH positions, the better column filling and chemical adsorption capacity for heavy metal ions. After 7 times reuse, the adsorption capacity for metal ions kept 85.3%. In the way of regulating pH, the magnetic amination chitosan beads were used to selectively separate the 200mg/L Cu²⁺, Zn²⁺ and Cr⁶⁺ mixed solution.The products were used to analyze and describe the adsorption behavior and process of metal ions. In the adsorption experiment, the adsorption was performed at the concentration range of 30mg/L and 1600mg/L, and three temperatures. The equilibrium was reached at 6 h. Four thermodynamics and three kinetics models were used to analyze the adsorption date and describe the adsorption process.The Freundlich and Generalized models yielded the best fit than other models. The adsorption occurred in heterogeneous surfaces with a uniform energy distribution, and it is reversible. With the increase of adsorption time and initial concentration, more heavy metal ions were adsorbed by multilayer absorption and chemical adsorption.The Dubinin-Radushkevich model was chosen to estimate the characteristic porosity and the apparent free energy of adsorption. When the concentration reached a threshold value, adsorption by layering on the surface turned into volume filling. In this experiment, the volume filling rate was approximate 14.37%.The pseudo second-order equation indicated that the rate limiting step was chemical adsorption. At the beginning, the adsorption process was a physical adsorption, which occurred very rapidly, but very unstable. After that, the chemical adsorption capacity raised steadily through the sharing or exchange of electrons, coordination and chelation, until the adsorption capacity reached equilibrium.更多还原