Synthesis Of Spiropyran-Crown Ether And Study On The Performance Of Lithium Extraction By Light Response

With the rapid update and iteration of mobile smart devices and the vigorous development of the new energy automobile industry,people’s demand for lithium salt products as battery materials is increasing.At present,the main sources of lithium salt products are lithium ore in nature and lithium-bearing salt lake brine.Compared with the extraction of lithium from ore with higher energy consumption and cost,the extraction of lithium salt from lithium-bearing salt lake brine is not only economical and green,but also rich in reserves,so it has become an important source of lithium salt products.my country’s salt lakes are rich in lithium resources,but most of my country’s lithium-containing salt lakes have complex ion composition and high content of magnesium ions as the main impurity ions.Magnesium and lithium are diagonal on the periodic table,and their physical and chemical properties are similar.The content of magnesium ions will increase the difficulty of separating lithium ions.The high molar ratio of magnesium to lithium in salt lakes in my country has severely restricted the development of my country’s lithium salt development industry.Aiming at the problem that high magnesium lithium is more difficult to extract lithium than salt lake brine,researchers have developed a variety of compounds and materials with high selectivity to lithium ions.Crown ether is a macrocyclic compound with a unique cavity structure.The metal ion can coordinate with the oxygen atom on the ring at the center of the macrocyclic ring to form a complex.Therefore,the macrocyclic size of the crown ether compound,the radius of the metal ion,and the coordination distance between the oxygen atom and the metal ion determine the selectivity of the crown ether structure to metal ions.Among them,12-crown 4-ether has a high degree of lithium ion.Selective.In addition,the crown ether derivatives with side chains prepared by introducing some chemical groups with special properties into the crown ether structure not only have better complexing ability for lithium ions,but also often have some other properties.In this study,the 5-nitrospiran-12-crown 4-ether compound with photoisomerization properties was synthesized.The compound molecule combines the high selectivity of the crown ether structure to lithium ions and the photoisomerization characteristics of the spiropyran structure.Under ultraviolet light irradiation,the spiropyran structure of the molecule is isomerized into a ring-opening cyanine structure.The phenoxy anion contained in the cyanine structure can enhance the complexing ability of the crown ether structure to lithium ions,thereby achieving selective complexation of lithium Ion;changing the light conditions to visible light irradiation,the ability to complex lithium ions under the closed-loop structure is weakened,and the reverse reaction can take place at this time to remove lithium ions.So as to realize the light-controlled extraction and enrichment of lithium ions.Subsequently,the compound was used as an extractant for the light-controlled extraction separation and enrichment of lithium ions,and the effects of factors such as the concentration of lithium ions,extraction time,molar ratio of magnesium to lithium,and impurity ions on the performance of lithium extraction were investigated.Finally,the compound and organic polymer materials were combined to prepare a lithium ion adsorbent,and the effects of time,temperature,ion concentration and other factors on the adsorption performance of lithium ions in the adsorption process were studied.The main research structure is as follows:（1）Using 2,3,3-trimethylindole,3-bromopropionic acid,5-nitrosalicylic aldehyde,1-aza-12-crown 4-ether as raw materials to synthesize 5-Nitrospiran-12-crown 4-ether compound.The molecular structure of the compound was analyzed by characterization methods such as ¹³C NMR,¹H NMR,HRMS.UV-Vis and fluorescence spectroscopy analysis proves that the compound has sensitive photoisomerization properties,can be isomerized into an open-ring form with a conjugated structure under UV light irradiation to make the solution appear purple-red,and can be restored to the original under visible light irradiation The colorless closed-ring form of,and this isomerization reaction is reversible,it remains stable after six cycles.（2）The ability of 12-crown 4-ether,5-nitrospiran and the synthesized 5-nitrospiran-12-crown 4-ether to complex with lithium ions were studied separately.The high-resolution mass spectrometry results proved that only spiropyrans were used.Only when pyran and crown ether exist at the same time can they form a stable complex with lithium ions and cannot complex with magnesium ions.Subsequently,the compound was used as the extractant,1,2-dichloroethane was used as the diluent,and the simulated brine was configured for extraction experiments.The results show that the extractant can selectively extract lithium ions,and is suitable for salt lake brines with high magnesium-to-lithium ratios,as well as for complex brine systems.（3）Dissolve 5-nitrospiran-12-crown 4 ether,(PVDF powder and PVP powder in DMF together,and pass A simple phase inversion method is used to prepare porous microspheres with photochromic properties.The microspheres were used as adsorbents for adsorption experiments.By measuring the whiteness of the microspheres irradiated by ultraviolet light and visible light,it is proved that the spiropyran-crown ether in the microspheres still retains the original photoisomerization properties.Scanning electron microscopy（SEM）characterizes the microspheres with macropores（6.0μm）and micropores（0.8μm）nested in a hierarchical pore structure.The porosity of the microspheres is calculated to be 78%.The adsorption experiment proves that the microspheres can selectively adsorb lithium ions,and the adsorption equilibrium is reached within 30 minutes.The kinetic fitting results are consistent with the pseudo-second-order kinetic equation,and the adsorption isotherm fitting results are consistent with the Langmuir isotherm adsorption equation,indicating that the microspheres The adsorption of lithium ions is a single-layer chemical adsorption.