Study On Preparation Of Light-responsive Pickering Emulsion And Performance Of Lithium Extraction

As a new type of energy and strategic resource,lithium is widely used in aerospace,manufacturing,nuclear,and optoelectronic industries,so it has always attracted attention.Our country's lithium resources are relatively rich,including ore lithium resources and salt lake lithium resources,of which salt lake lithium resources are the majority,so the extraction of lithium from salt lakes has become one of the important ways for the production of lithium and lithium products in my country.In the current process for extracting lithium from salt lake brine,the extraction method has the advantages of low cost and simple process.Although it has been applied in industry,there are still small oil-water mass transfer interfaces,difficult separation of oil and water two phases,and easy formation of the third phase.Disadvantages.Pickering emulsion is an emulsion stabilized by solid particles instead of traditional emulsifiers.The emulsion has strong stability.At the same time,Pickering emulsion has the advantages of low toxicity,recyclable emulsifier and emulsion,and low cost.Based on this,we propose that the spiropyran-crown ether compound,which is light-responsive and selectively recognizes lithium ions,is confined in the oil phase of the O/W-type Pickering emulsion,and the light-responsive Pickering emulsion is used as the medium to extract lithium.In this paper,silica nanoparticles are used as emulsifiers,and the oil phase is a mixed oil phase of n-octane-dodecanol to prepare Pickering emulsion.During the preparation process,it is investigated that the stirring speed,the volume ratio of oil and water phase,and the amount of emulsifier are stable to Pickering emulsion The optimal conditions for the preparation of Pickering emulsion are obtained.Under the optimal conditions,a spiropyran-crown ether compound with light responsiveness and selective recognition of lithium ions is added to the oil phase to prepare a stable light-responsive O/W Pickering emulsion;then use the light-responsive Pickering emulsion as a medium to extract lithium,and investigate the effect of extraction time,emulsion volume and dosage,initial lithium ion concentration,and extraction order on the extraction effect during the extraction process;Finally,KCl O₄,Fe Cl₃and Zn Cl₂ solutions were added to the extraction system to investigate the synergistic extraction effect of these three solutions in cooperation with Pickering emulsion to extract lithium ions.The specific research content and conclusions are as follows:First,use nano-silica as the emulsifier,the oil phase is a mixed oil phase of n-octane and dodecanol,and the water phase is ultrapure water to prepare Pickering emulsion.The stirring speed,the volume ratio of oil and water phase,and the amount of emulsifier for the preparation of the emulsion are investigated.On the influence of the stability of Pickering emulsion,the experimental results show that:during the preparation of Pickering emulsion,the higher the stirring speed,the greater the viscosity of the emulsion,the smaller and uniform emulsion droplets,and the more stable the emulsion,so the emulsion is most stable at 8000rpm;The oil phase increases,the emulsion viscosity increases,the droplet size decreases,and the emulsion layering phenomenon decreases.The emulsion is most stable when the volume ratio of the oil and water phase is 4:1;the emulsion viscosity is the largest when the emulsifier dosage is 0.30 g,The size of the emulsion droplets is uniform,and the emulsion is the most stable.Therefore,the spiropyran-crown ether compound was added to the oil phase under the optimal conditions(8000 rpm,0.30 g silica,and the volume ratio of the oil-water phase was 4:1)to prepare a light-responsive Pickering emulsion.The light-responsive Pickering emulsion is combined with separation technology,and the prepared light-responsive Pickering emulsion is used as a medium to separate lithium ions in salt lake brine.In this experiment,the extraction method is used,based on the selective extraction of lithium ions fromthe emulsion,the lithium ion content is measured by atomic absorption spectroscopy,and the results are analyzed.The process of separating lithium ions by light-responsive Pickering emulsion is relatively fast,reaching the maximum within 20 minutes;increasing the amount of Pickering emulsion and increasing the concentration of lithium chloride solution can improve the efficiency of emulsion separation of lithium ions,and multi-stage extraction can also improve the efficiency of lithium ions.Separation efficiency;good emulsion stability,little change in the morphology of the emulsion before and after extraction,it is feasible to use Pickering emulsion for extraction.The extraction agent was added to the extraction system to establish a new co-extraction system of co-extractant/photoresponsive Pickering emulsion to investigate the co-extraction effect of the three solutions of KClO₄,ZnCl₂ and FeCl₃ in the extraction process.The experimental results show that:KCl O₄ and Zn Cl₂ can improve the extraction efficiency;adding Fe Cl₃ emulsion loses the light responsiveness and the extraction efficiency is reduced.This research solves the problems of small mass transfer interface and serious organic phase dissolution loss in traditional extraction methods,and can provide a new idea and method for the separation and extraction of other valuable elements.