Separation And Enrichment Of Lithium From Magnesium Sulfate Subtype Salt Lake Brine By Nanofiltration Membrane

In recent years,with the rapid development of new energy vehicles,China's demand for lithium salt products has increased substantially.Therefore,in order to reduce the supply and demand gap and external dependence of lithium ore,vigorous development of lithium resources in salt lakes is the inevitable trend of the development of lithium salt industry.Because of the high ratio of magnesium to lithium,complex extraction process and low lithium yield of salt lake brine in China,the efficient separation of magnesium and lithium is still the core and key of lithium extraction from salt lake brine at present.Because nanofiltration membranes can achieve the relative separation of monovalent and divalent ions,nanofiltration membranes have a good application prospect in the separation technology of magnesium and lithium from salt lake brine.For the development of integrated lithium extraction technology with high efficiency,environmental protection and low cost.Based on the above objectives,the effects of membrane types and operating conditions on separation performance,the effects of different ions in brine on the separation performance of magnesium and lithium by nanofiltration membrane,and the separation and simulation of nanofiltration membrane in salt lake brine are studied in this paper.The main contents are as follows:?1?Screening of nanofiltration membranes for magnesium-lithium separation.The separation performance of six types of nanofiltration membranes,NT102,NT103,NT201,NF90,NF270 and XN-45,was studied using simulated brine with high Mg²⁺/Li⁺ratio as raw materials.The rejection rates of lithium and magnesium ions and separation factors by six types of membranes under different operating conditions were investigated.The results showed that the separation factors of magnesium and lithium of NT103 and NT201 nanofiltration membranes were kept below 0.178 under different operating conditions,and they had good separation performance of magnesium and lithium.?2?The effect of different ions on the separation performance of magnesium and lithium by nanofiltration membrane.Sodium ion,potassium ion,boric acid and sulfate ion were added into the solution with high Mg²⁺/Li⁺ratio to explore the effect of different ions on the separation performance of magnesium and lithium by nanofiltration membrane.The results show that with the increase of sodium ion,potassium ion and boric acid,the separation factor of magnesium and lithium decreases and the performance of nanofiltration membrane for separating magnesium and lithium increases,while the rejection rate of lithium ion increases significantly with the addition of sulfate ion,while the rejection rate of magnesium ion is basically stable,the separation factor increases,and the separation effect of magnesium and lithium decreases.?3?Separation performance and Simulation of nanofiltration membrane for salt lake brine.Through single salt and double salts permeation experiments,the permeation equation,competition coefficient and regulation factor of salts were obtained.Then the permeation of ions in brine was calculated by semi-empirical model,and compared with the experimental data of simulated brine permeation experiments.The results show that the simulated values of ion permeation are in good agreement with the actual values,which can effectively predict the performance of nanofiltration membrane in the separation of Salt Lake brine.