Preparation Of LATP Ceramic Membrane And Its Performance In Lithium Extraction From Salt Lakes

In recent years,with the rapid development of new energy vehicles and portable electronic devices,there has been a significant expansion of the lithium market,and the demand for lithium resources in the market has increased dramatically,resulting in a shortage of lithium resources supply.Lithium resources in salt lakes are more abundant than in lithium mines,and the process of lithium extraction from the salt lake is simpler and less expensive to operate.China’s salt lake lithium resources are mainly concentrated in Qinghai and Tibet,with Qinghai salt lake lithium resources accounting for more than 60%of the global lithium reserves,but the high magnesium-to-lithium ratio of the endowment characteristics make the lithium extraction process faces a huge challenge.Therefore,the development of efficient and environmentally friendly salt lake lithium extraction technology is an urgent problem to be solved.Given the above research background,this project is a systematic study of lithium titanium aluminum phosphate Li_1+xAlx Ti_2-x（PO₄）₃（LATP）,an inorganic ceramic material with high lithium selectivity.Using porous alumina as the membrane carrier,LATP-Al₂O₃composite ceramic membranes were prepared by stretching impregnation coating method and ceramic sintering and forming technology,and the membrane separation and electrodialysis technology were coupled for lithium extraction study in an aqueous salt system through the modification of molecular structure and the control of the membrane formation process,which simplified the membrane separation process.This method can realize the extraction of lithium resources from brine with low energy consumption and a green environment,which is important to promote the development of lithium industry chain innovation.The main contents of the research in this paper are as follows:The first part is the preparation of LATP powder for the superionic conductor.The LATP material with uniform particles and good performance is a key step in the preparation of composite ceramic membranes,therefore,the NASICON type LATP superionic conductor was selected for the preparation of this topic by sol-gel method,and the effects of aluminum doping,heat treatment temperature,time and other conditions on its crystalline structure,morphological characteristics,and elemental composition were investigated in depth.It is found that LATP is a rhombic crystal space structure of R3c,consisting of PO₄ tetrahedra and Ti O₆ octahedra arrangement,with regular space defects to provide channels for lithium ion transport.The higher the calcination temperature,the larger the characteristic peak value and the larger the particle size.The LATP particles with uniform particle size were prepared and the obtained nanoparticles were studied for aqueous dispersion to provide a uniformly dispersed and active LATP suspension for later coating.In the second part,the LATP-Al₂O₃ composite film formation process is studied.Firstly,porous alumina ceramics with high mechanical strength and uniform pore size distribution were prepared as the support body for the high lithium conductivity LATP film layer.The pore size and mechanical strength of the support body were the key factors,and it was found that the alumina support body with uniform pore size distribution and no defects was obtained by calcination at 30 MPa 1200℃for 2 h.The pore size was 158 nm and the flexural strength was 34.2 MPa.It was found that the film prepared with a PVA concentration of 10 mg·m L^-1,PVP K12 addition of 2%,pulling speed of 500μm·s,impregnation time of 30 s,and three times impregnation had the best denseness after heat treatment at 1100°C for 2 h.The LATP ceramic films with different thicknesses of 5,10,15,20,30,and 35μm were prepared by changing the solid content of LATP in the coating solution.The third part is the performance study of LATP membrane electrodialysis in the separation of magnesium and lithium.Through the study of separation efficiency,a multi-stage electrodialysis coupling device was designed,and important indexes such as Mg-Li separation efficiency,lithium recovery,and energy consumption were systematically studied on the multi-stage electrodialysis system.The experimental results showed that the 20μm thick LATP membrane showed the best separation effect,the Li⁺recovery reached 77.15%after 12 h of three-stage continuous electrodialysis,and the magnesium-lithium ratio was reduced from 40:1 to 2.1:1.Based on the design of the LATP membrane electrodialysis device,the extraction of lithium from the salt lake was successfully achieved,and the calculated energy consumption per The calculated power consumption for lithium extraction was 47.6 k W h per 1 kg of lithium.