瓜环对重金属环境污染物的分子识别

【作者】 卢小军；

【导师】 薛赛凤；

【作者基本信息】 贵州大学 ， 物理化学， 2009， 硕士

【摘要】 所有的重金属超过一定浓度都对人体有害,而且重金属长期积累在生物体内通常不可降解。瓜环（Q[n],n=5-8or10）是一类与环糊精、冠醚具有类似结构的笼状大环化合物,它的两个端口“镶嵌”着一圈带负电性的羰基氧原子,可以与金属离子发生亲水性的端口作用。本文利用多种超分子物理化学方法考察了瓜环对重金属铅、镉的分子识别作用,为探索瓜环在重金属的环境监测与控制中的应用提供理论依据和有用信息。首次利用差分脉冲伏安法考察了一种新型的改性瓜环—对称四甲基六元瓜环（TMeQ[6]）对铅、镉离子的识别作用。结果表明:TMeQ[6]与铅、镉离子均形成物质的量之比为1:2的超分子配合物,配合物稳定常数分别为K_TMeQ[6]-Pb²⁺=2.12×10⁹ L²·mol^-2、K_TMeQ[6]-Cd²⁺=2.10×10⁹ L²·mol^-2。利用单晶x-射线衍射法对TMeQ[6]与铅离子作用形成的晶体进行测试,晶体结构分析结果表明TMeQ[6]与铅离子是以1:2的作用比,在瓜环的两端口发生相互作用。两种方法的测定结果相互佐证。自然界的含铅、镉的污水中往往还会含有其他的金属,如锌、铁、铬等,本文利用差分脉冲伏安法考察了铁、亚钴、锌等过渡金属离子共存的条件下,TMeQ[6]对铅、镉的识别性能,结果表明:TMeQ[6]对铅、镉有明显的选择性识别作用。利用原子吸收光谱法考察了普通六元瓜环（Q[6]）固体粉末对水溶液中铅离子的捕集性能,分别考察了体系pH的影响,捕集动力学、热力学性质。结果表明:当作用体系pH 1.0-6.0时,随着体系pH值的增大,六元瓜环对铅离子的捕集能力逐渐增强;捕集动力学可用Lagergren拟二级速率方程来描述,线性相关系数达到0.99以上;捕集热力学等温线符合Freundlich方程;活性炭对比实验表明,活性炭捕集铅离子符合Langmuir等温模型,瓜环与活性炭对铅的捕集模式不相同;以静态模拟方式考察了Q[6]粉末捕集含铅废水的能力,表明在浓度为1.00×10^-2 mol/L的含铅离子模拟水样中,加入了2.0 g/mmol Q[6]固体粉末后,Q[6]粉末对铅离子的捕集率可达到98.4%。更多还原

【Abstract】 All of the heavy metals are harmful to the human body more than a certain concentration.They are the most insidious pollutants beeause of their nonbiodegradable nature and ability to persist for long periods.Benefit Cucurbit[n]urils have two identical portals surrounded by carbonyl groups,they are able to bind metal cations as macrocyclic ligands like as crown ethers,cryptands and calixarenes and create novel supramolecular structures.Therefore,this thesis concentrates reseaches on molecular recognition of the Cucurbit[n]urils with heavy metals,In this paper,a variety of physical and chemical methods of supramolecular investigated Cucurbiturils complex with heavy metals lead and cadmium,preparation to explore Cucurbit[n]urils advantages in medical, food,clinical and enviromental monitoring fields.1.The complex information ofα,α’,δ,δ’-tetramethylcucurbit[6]uril（TMeQ[6]） with the transition metal ions has been studied by differential pulse voltammetry（DPV） and X-ray crystallography.Binding constants were determined from voltammetric data,the Pb²⁺ and Cd²⁺ dications displayed high binding affinity to TMeQ[6](K_Pb²⁺=2.12×10⁹ M^-2 and K_Cd²⁺=2.10×10⁹ M^-2) and forms 2:1(M²⁺/TMeQ[6]) complexes.The crystal structure of TMeQ[6]-Pb²⁺ showed a 2:1(pb²⁺/TMeQ[6]) complex in solid state which was consistent with the result in the solution state.2.Nature sewage often contain other metal besides lead and cadmium,such as zinc,iron, chromium,etc.The experimental results of differential pulse voltammetry（DPV） reveal that this water soluble cage-type compound shows very high selectivity for Pb²⁺ and Cd²⁺,while appears a masking compound for the other transition metal ions,particularly for the Co²⁺,Fe³⁺,Zn²⁺,Cr³⁺ due to a sharp decrease in the DPV peak current of these metal ions in the presence of TMeQ[6].3.Studied the kinetic,thermodynamic of the Lead Ion adsorpt on Cucurbit[6]uril using the AAS,the kinetics could described by the Pseudo-second order model effectively, the correlation coefficient（r） more than 0.99.The adsorption isotherms for lead ion follow the Freundlich isotherm model,the correlation coefficient（r） more than 0.97 in the rome Temperature.Studing the adsorption under the condition of pH=1～6,we find the adsorption rate is best in pH=6.0,get a excellent condition for simulation waste water containing Lead 1.00×10^-2mol/l is treated by Static method at last,The results show that the absorption rate reach in 98.4%after the addition of the Cucurbit[6]uril 2.0 g/mmol.更多还原