循环型双位配体萃取剂对阳、阴离子的协同萃取特性与机理研究

Metal recovery via solvent extraction in hydrometallurgical process is essentially an ion-exchange process in which the desired metal cation exchanges with protons from an extractant. However, the anions of the metal salt are not extracted and they may cause hazard to environment; large volume of organic solvents used during the solvent extraction process also causes environmental issues. Similarly, cationic ion-exchange resins used for the treatment of waste water containing heavy metal salts only absorb metal ions whereas the anionic ions still cause environmental pollution. To explore solutions to these problems, we plan to design and synthesize a range of novel ditopic ligands which can bind cation and its attendant anion(s) of heavy metal salt simultaneously. The bifunctional ligand will be then grafted onto silica gel via covalent bond. Upon complexation of the ligand with metal ions, the phenolic hydroxyl protons transfer onto the ortho-pendant tertiary amine group,thus creating positively charged environment wherein the anions of the metal salt are bound via a combination of favourable hydrogen bonding and electrostatic interactions. The coordinating extraction efficiency and selectivity for heavy metal salt ions and the regeration and recycling property of the extractants will be investigated by changing steric and electronic structure of the coordinating ligands and pH conditions of the extracting system; the effect of coexisting ions on the coordinating absorption processes will be analysized; the thermodynamics and kinetics model for the co-operative extraction of the cation and anion will be established; the factors and mechanism which control the simultaneous binding、co-operativity、 recongnition and transport of cation and anions will be explored; the structure-function relationship will be revealed; and the theory for optimal ligand design will be further clarified. New methodology will be established from the research results for developing solid extractants which simultaneously and efficiently bind and transport cation and anions of heavy metal salts. The results will provide theoretical foundation and technical support for solving the environmental problems arised from the hydrometallurgical processes and the treatment of waste water containing heavy metal salts; and the research may also find application in the resource utilization of heavy metal salt pollutants.

针对湿法冶金溶剂萃取过程中须使用大量有机溶剂，并为解决湿法冶金金属溶剂萃取过程和离子交换树脂处理含重金属盐废水过程所产生的阴离子污染等问题，本研究拟设计、合成一系列能同时结合重金属盐阳、阴离子的新型两性离子双位配体，将其负载在硅胶上制备可循环再生的固体配位萃取剂。研究配位基团的空间和电子构型、体系的pH 值等条件对金属盐阳离子和阴离子的配位萃取效果、萃取选择性、以及对萃取剂的再生和循环功效的影响；分析共存离子效应与配位吸附过程之间的内在联系；建立重金属盐阳离子和阴离子协同萃取的热力学和动力学模型；探索影响阳、阴离子协同萃取及识别传递的因素和机理；揭示结构-性能关系，阐明优化配体设计的理论依据。本研究将建立固体萃取剂同时有效配位萃取重金属盐阳、阴离子的新方法，并为探索解决上述环境污染问题及重金属盐污染物的资源化利用等提供理论基础和技术支持。

湿法冶金中溶剂萃取以及离子交换树脂处理含重金属废水的过程中未被萃取的阴离子仍会污染环境。另外，在湿法冶金和含重金属盐废水处理的溶剂萃取过程中要使用大量易燃有毒的有机溶剂来萃取水相中由配体和金属离子形成的配合物。因此，探索不用或少用有机溶剂的“绿色”过程和方法有效地对金属盐阳离子和阴离子同时萃取具有重要的意义。. 本项目设计、制备了一系列能同时结合重金属盐阳、阴离子的循环型固体双位配体萃取剂SG-L1到SG-L10。我们首先合成了一系列游离的席夫碱双位配体-金属盐配合物， 利用X-射线衍射、DFT计算和波谱表征等分析配合物的结构，为探讨配合物水解稳定性，阳、阴离子结合模式和固体配位萃取剂的设计及应用提供了基础，其中部分新型配体的合成也有益于丰富席夫碱配位化学及其相关应用。研究了各种固体双位配体萃取剂对于金属盐阳、阴离子的协同吸附、选择性吸附以及循环再生性能，包括吸附热力学和动力学。分析了萃取吸附的影响因素，探讨了构-效关系，包括研究配体的电子构型、空间结构和共存离子效应等对固体双位配体萃取剂吸附性能的影响。萃取剂对金属离子和阴离子的吸附均符合Langmuir等温模型和准二级动力学方程。其中SG-L10上的配体具有较高柔性和较小位阻，因此SG-L10对CuSO4的饱和吸附容量高达0.84mmol/g，并且具有较好的可调节阳、阴离子吸附选择性。该项目的研究结果为进一步优化配体设计以及潜在的应用建立了理论基础，初步建立了循环型固体萃取剂同时配位萃取重金属盐阳、阴离子的概论和原理，为在“绿色”冶金及水环境中重金属盐污染治理的应用提供了新的思路和研究基础。. 此外，作为本项目的拓展研究，我们合成了一系列席夫碱-Cu(II)配合物，研究分析了这些配合物对脲酶的抑制功能及机理，为水环境及土壤等生物圈中的有机或无机氨的调节和污染控制提供有益的科学依据。我们还制备了几种新型的磁性纳米吸附和催化复合材料用于有效处理水溶液中的酚或染料等有机污染物，为开发“绿色”、经济的有机废水处理技术提供借鉴。