Spectral Studies On Intermolecular Interactions In The Liquid- Liquid Extraction Separation System

On microcosmic view, the intermolecular interactions in the separation system determine the results and efficiency of the separation. The understanding of the intermolecular interactions in the separation system is beneficial for controlling and selecting the optimal separation process. Thus it is of importance to carry out research on the intermolecular interactions in the separation system. By using the spectral tools, this thesis has made researches on the interfacial interaction between metal ions and organphosphorus extractants, the interaction between polymer and metal ions in the binary-water phase system. Besides, based on the asynchronous correlation spectroscopy, new methods for probing the weak intermolecular interactions in the separation system were proposed. The methods were adopted to detect the dipole-dipole interactions between different extractants, the ion-dipole interactions between ions and extractant and the interactions between polymer and protein in the binary-water phase system. The main contents and results are given as follows.The interfacial interactions between coexisting ions in the feeding liquid and TOPO were studied by infrared reflection spectroscopy, SFG and 31P NMR. The results show that Mg2+, whose radius is relatively small and charge is relatively high, can promote the dehydration of TOPO molecules at the interface between the TOPO layer and the aqueous solution. Thus, the contact region of TOPO with bottom phase is reduced and the ability of TOPO to extract the metal ions in the bottom phase is weakened. Contrary to Mg2+, SCN-, which has high polarizability and large size, is in favor of the hydration of TOPO molecules at the interface. The further hydration of TOPO molecules makes the contact region of TOPO with bottom phase increased, thus the ability of TOPO to extract the metal ions in the bottom phase is strengthened. This research gives the molecular level explanations about the effect of coexisting ions on the extraction efficiency of organphosphorus extractants, which is helpful to understand and optimize the extraction process.The interactions of sodium and potassium ions with PEO-PPO copolymer were investigated by using FTIR, Raman and 23Na NMR spectroscopy. Experimental results reveal that direct interactions between salt cations and PEO-PPO macromolecular chains indeed occur in appropriate conditions. This work provides molecule-level experimental evidences for the interactions between cations and water-soluble polymer and helps us gain insight into the phase separation and the mechanism of binary-water phase extraction.In order to probe the weak intermolecular interactions in the separation systems, the ASMR approach, which is an improved method based on the AOSD approach, was proposed. Although the AOSD approach proves to be a reliable tool to detect weak intermolecular interactions, the interpretation of AOSD spectrum is difficult sometimes. The most common issue relating to the interpretation of AOSD spectrum is the presence of excessive cross peaks caused by the noise or the cross peaks related with the intermolecular interactions buried by the noise. This could lead to over interpretation of the correlation plots and erroneous band assignments. The ASMR spectrum has higher signal to noise ratio, thus it is a more reliable tool in reflecting the intermolecular interactions in the separation systems.Mathematical analysis and experimental results suggest that variations on absorptivity cannot be reflected by the ASMR spectrum when only one substance involving intermolecular interactions possesses a characteristic peak. The fact that the patterns of cross peaks fail to reflect variation of absorptivity brings about the following two problems:(1) This failure prevents us from obtaining comprehensive information on the spectroscopic behavior under intermolecular interactions. (2) The inability to reflect variation of absorptivity makes the approach under the risk of making incorrect conclusion concerning whether intermolecular interactions occur or not in some special cases. If intermolecular interactions only bring about changes on the absorptivity, no cross peaks can be observed in the asynchronous correlation spectrum. That is to say, the ASMR spectrum cannot always reflect the intermolecular interactions between P and Q. In order to solve this question, the ASAP approach was proposed. By using the ASAP approach, variations on absorptivity can be retrieved when only one substance involving intermolecular interactions possesses a characteristic peak.MWASMR approach, by which the molar ratio of the two substance involving intermolecular interactions can be acquired, was proposed. MWASMR approach is free from the constraints with which methods of Job’s continuous variations and mole-ratio are frustrated, thus it is a more practical method for acquiring the molar ratio of the two substance involving intermolecular interactions in the separation systems.