Study On Interfacial Mocular Interaction Mechanism Of Rare Earth Extraction By P507-Span 80 System

Rare earth is a critical strategic resource,commonly referred to as the"industrial gold"and"vitamin"of contemporary functional materials.With the rapid economic development in recent years,the demand for rare earths in related industries has been increasing,and the rare earth industry has shown rapid development.After decades of development,solvent extraction has become the main process of rare earth separation and purification because of the advantages of good separation effect,low cost,easy operation and strong continuity.However,in rare earth extraction,emulsification often occurs due to factors such as the nature of the aqueous phase,the nature of the organic phase and improper control of operating conditions.Emulsification not only affects the separation efficiency of rare earths,but also brings serious ecological pollution and resource waste.In this paper,using Span 80 surfactant as regulator and P507 as extractant,the molecular interaction and dynamic aggregation behavior at the interface were characterized by LB film analyzer and surface interfacial tension meter.Atomic force microscopy and Fourier Infrared Transform Spectroscopy were used to study the interfacial stability reinforcement mechanism.The study examined interfacial aggregation and molecular interactions while adjusting P507 concentration,saponification degree,and Span 80 content in the organic phase.The formation of aggregates in the organic phase can be promoted by increasing the concentration of P507,thereby improving interfacial stability.Depolymerization of the P507 dimer occurs when the degree of saponification is less than 20%,and more P507 molecules are adsorbed at the oil/water interface,thus enhancing the molecular interaction force and improving interface stability.Mutation occurs and forms a linear polymer structure when the degree of saponification is 30%,and increasing the degree of saponification further leads to the formation of sol-gel,which is detrimental to interfacial stability.Increasing the Span 80 content by 6%depolymerizes the P507 dimer due to the strong polarity of water molecules at the interface,resulting in more P507 molecules entangled with Span 80 molecules at the interface and enhancing interface stability.However,exceeding 6%Span 80 results in the formation of a polymer structure in the organic phase,which is not conducive to interface stability.Fourier Infrared Transform Spectroscopy shows that strong interaction forces exist between Span 80 and P507 molecules,and Atomic Force Microscopy indicates that the addition of Span 80 leads to the formation of a well-arranged three-dimensional mesh structure with P507 molecules,thereby strengthening the oil-water interface.The organic phase is preloaded with different rare earth Er³⁺,impurities Mg²⁺and Al³⁺,and the influence of metal ion loading on intermolecular interaction and aggregation behavior at the interface is investigated.It was found that the higher the preloading rate of rare earth Er³⁺in the organic phase,the stronger the dehydration ability,the more uniform and compact the molecular arrangement at the interface,and the enhanced interface stability.However,when the preload rate is too high,some substances such as hyperpolymers are generated,which causes a force imbalance at the interface,resulting in deterioration of interface stability.The increase of Mg²⁺preloading rate in the organic phase can further strengthen the dehydration effect and improve the stability of the interface to a certain extent.However,when the preload rate is too high,the polymer structure such as colloid will be formed,which is not conducive to the stability of the interface.In the appropriate range,increasing the preload rate of Al³⁺in the organic phase will inhibit dehydration and is not conducive to interface stability.Fourier transform spectroscopy（FTIR）and atomic force microscopy（AFM）further confirm the correctness of the above conclusions.P507 monomolecular films with 5%saponification and 6%Span 80 content were sprayed on the surface of different aqueous solutions to investigate the influence of p H,rare earth Er³⁺and impurity Mg²⁺/Al³⁺concentrations on intermolecular interaction and aggregation behavior.The results showed that lowering p H in the aqueous phase would inhibit the dissolution of organic molecules in the aqueous phase.The arrangement of organic molecules at the interface became closer and more uniform.It is beneficial to improve the stability of the interface.With the increase of Er³⁺and Mg²⁺concentrations in the aqueous phase,interfacial stability gradually decreases.And the increase of Al³⁺concentration in the aqueous phase can improve interfacial stability.