【作者】 段迪；

【导师】 任其龙； 苏宝根；

【作者基本信息】 浙江大学 ， 制药工程， 2014， 博士

【摘要】 超临界CO2螯合萃取金属离子作为新兴的绿色工艺,具有传统工艺无法比拟的优越性。其速率快、萃取效率高、无毒无污染等优点,在环境保护、核工业、湿法冶金、材料科学、食品医药等领域有着广阔的应用前景。在超临界CO2螯合萃取工艺中,螯合剂成为决定萃取效率高低的核心因素,不仅要在超临界CO2中有足够高的溶解度,还要能够选择性的与金属离子形成稳定的、有较好溶解度的螯合物。传统的螯合剂很难同时满足萃取效率与选择性的要求,所以本文开发设计了一类有高溶解性的双磷酸酯型开链冠醚类螯合剂。通过采用实验研究与量子化学计算结合的方法,从宏观和分子水平解释双磷酸酯型开链冠醚螯合剂分子结构与其在超临界CO2中的溶解度及萃取选择性之间的相互关系,研究了螯合机理,并分别对镧系、重金属、碱土金属离子等实际体系进行萃取分离,取得了良好的分离效果。通过溶剂催化法合成了双磷酸酯型开链冠醚螯合剂初产物,经硅胶柱层析分离并以元素分析、IR. ESI-MS和1H NMR等表征手段对目标产物进行表征,确定了化合物结构。通过浊点法测定了313.15～333.15K.9-20MPa条件下螯合剂的溶解度,所测螯合剂的溶解度均能都达到10-3数量级,与文献报道含氟螯合剂的溶解度相当；采用半经验的Bartle模型、Chrastil模型拟合溶解度数据,结果良好,平均绝对相对偏差(AARD)分别为3.4%-5.2%与1.23%-2.15%。通过基团贡献法计算得到的六种螯合剂溶解度参数按EG2TP<EG2TH<EG2Oct<EG2IPE<EG3IPE<EG4IPE的顺序依次增加,与螯合剂溶解度顺序符合。计算并关联了螯合剂的分子连接性指数,其中EG2TP、EG2TH、EG2Oct的0χ与溶解度数据关联相关系数可达0.97。采用COSMO-RS量化计算方法研究螯合剂与C02相互作用,作用大小顺序为EG2Oct≈EG2IPE<EG2TH<EG2EH<EG2TP.通过分子摩尔体积的估算,研究了螯合剂与CO2分子形成的分子簇变化,其值随温度的升高而减小。以对金属螯合物表征的手段,研究了螯合剂的配位机理。同时通过Gauss量化计算,研究单磷酸酯分子、不同烷基结构的双磷酸酯分子及本文合成的多种螯合剂分子的Mulliken电荷分布规律。讨论了螯合剂支链结构对金属螯合物稳定性的贡献,并以EG2IPE为例,计算了螯合剂与镧系金属离子的相互作用能,预测了螯合剂对镧系金属离子的选择性。优化了螯合萃取工艺,并在最佳工艺条件下(P=20MPa,T=313.15K,搅拌1h,添加10μL水,15μL螯合剂)展开混合金属离子萃取实验。镧系金属离子的萃取率均能达到60%以上(除EG2Ben),最高可达90%。螯合剂萃取金属离子的效率与其溶解度相关,螯合剂溶解度大,萃取效率越高。研究了螯合剂侧链对金属离子选择性的影响规律,空间位阻小有利于重镧系金属离子的萃取。同时侧链对中心金属离子有掩蔽效应,掩蔽越好,金属螯合物的稳定性越高,相应萃取效率越高。此外,在最优条件下,重金属离子pb2+、Cd2+、Hg2+也能够被高效脱除(pb2+,萃取效率最高89%；Cd2+,萃取效率最高78%；Hg2+,萃取效率最高75%)。同样,碱土金属离子Ca2-、Sr2+、Ba2+也有较好的脱除效果(Ca2+,萃取效率有49-74%；Sr2+,萃取效率有50-73%；Ba2+,萃取效率有16-64%)。更多还原

【Abstract】 As a green technology, supercritical CO2chelating extraction (SCCE) of metal ions has obvious superiority to the traditional extraction methods. With its fast speed, high extraction efficiency and non-toxic properties, SCCE has great application prospects in the field of environmental protection, nuclear industry, hydrometallurgy, materials science, food and medicine. Chelating agents affect a lot in the SCCE process. Higher solubility in SCCO2and the ability to form more stable metal complex are the essential demands. It is difficult to satisfy the requirements of the high extraction efficiency and also the metal extraction selectivity using these traditional chelating agents, thus we designed a serious of open chain crown ether like diphosphate chelating agents which have good solubility in scCO2. The ligands’ structure effect on their solubility and their selectivity to the metals were studied through the extraction experiments and also the quantum chemical calculations. The mechanism was also considered and good separation results were obtained in the extractions of lanthanides, heavy metals and alkaline earth metals.These open chain crown ether like diphosphate chelating agent were synthesized and purified by silica column. The ligands were characterized by elemental analysis, IR, ESI-MS and1H NMR spectra to identify the structures. Also the reaction mechanism was discussed.The solubilities (cloud point pressure) of the ligands in scCO2were determined at313.15～333.15K and9-20MPa. The solubilities of these ligands were found to reach10’3orders of magnitude, which were in the same order of fluorine-containing chelating agents. These data were well correlated with Bartle model and Chrastil model and the fitting results are satisfactory with AARD of3.4%-5.2%and1.23%～2.15%respectively. Also the solubility order of the ligands was in good agreement with the solubility parameter calculated by the group contribution method. The molecular connectivity index0χ was calculated and correlated with solubility of the ligands and the correlation coefficient is0.97in the case of EG2TP, EG2TH and EG2Oct. The interaction between the chelating agent and CO2were calculated by COSMO-RS method and the order of EG2Oct≈EG2IPE<EG2TH<EG2EH<EG2TP was similar as their solubility order, indicating that the branched side chains played an important part of solubility increasement. The molecular molar volume of the ligands was estimated and the molecular cluster size reduced as the temperature of scCO2increased.The mechanism of the coordination was discussed by characterization of the metal complex. The Mulliken charge of monophosphate, diphosphate with different designed alky side chain and the ligands prepared in this article were all calculated by Gauss software. Also the interaction energy ΔE between the ligands and the metal ions were estimated and selectivity to metals was predicted in the case of EG2IPE to the lanthanide metal ions.The operation conditions of the SCCE were optimized (P=20MPa, T=313.15K, stirring for1h,10μL of water and10μL chelating agent added). In the extraction of lanthanide ions, all the chelating ligands exhibited higher metal ion extraction capability (except EG2Ben), and the extraction efficiency could reach60%～90%without any modifier. The extraction efficiency of these ligands was consistent with their solubility order in scCO2. Better solublity of the ligands resulted in higher extraction efficiency of the metals. The side chain of ligand could influence the extraction process by the steric hindrance effect. Small steric hindrance favors for extraction of small radius ions and large side chain volume gives a better masking effect of the central metal ion resulting more stable metal complex. Heavy metal ions of Pb2+, Cd2+and Hg2+could be well removed under optimal condition. The extraction efficiency could be89%of Pb2+,78%of Cd2+and75%of Hg2+. Alkaline earth metal ions Ca2+, Sr2+and Ba2+could be extracted with49%-74%,50%-73%and16%-64%, respectively.更多还原