Study On Solvent Extraction Of Lithium Ions From Salt Lake Of High Ratio Of Magnesium To Lithium With Salt Containing Complex Anions With Symmetric Syereo Structrue As Co-extiaction Agent

The lithium resources are very rich in China,and mainly distribute in the western regions,like Tibet and Qinghai.The salt lakes also contain some other metal ions,such as potassium,sodium and magnesium ions.Compared with foreign salt lakes,the salt lakes in China influenced by geographical location and environmental conditions have the characteristics of high ratio of magnesium to lithium.Therefore,the effective separation of lithium ions from other metal ions has become the key point in the extraction of resources from salt lakes in China.In this paper,Chaerhan Salt Lake was selected as subject.The simulated brine was prepared in the laboratory with the Mg/Li ratio as 80.Na3PMo12O40+TBP+MIBK and NaBPh4+TBP+CH2ClBr were screened in previous experiments,and the parameters of the whole extraction process were optimized.In addition,the mechanism of the extraction process was studied by combining simulation calculation and nuclear magnetic characterization.For the Na3PMo12O40+TBP+MIBK extraction system,when the Na3PMo12O40/Li molar ratio,phase ratio and the TBP volume fraction were 1.2,1.0 and 40%,the extraction efficiency of lithium ion and separation factor of Li/Mg in single stage could reach up to 58.74%and 207.95,respectively.When 1.8mol/L NaCl and 0.2mol/L LiCl were used as washing agent and the phase ratio was 3.0,the washing efficiency of magnesium ions could reach up to 99.95%,and the potassium ions could be completely eluted.The stripping experiment was carried out twice with 0.26mol/L HCl as stripping agent and phase ratio as 3.0.The results showed that the stripping efficiency of lithium ions was 98.03%.In addition,a new stripping process with sodium carbonate as stripping agent was proposed.The stripping,organic phase regeneration and product preparation processes could be realized in one step,which greatly simplied the operation process.By using this stripping process,97.05%of the lithium ions in the organic phase were stripped back to the aqueous phase in the form of lithium carbonate with 2.5mol/L Na2CO3 solution as the stripping agent and phase ratio as 1.0.The analyses results of simulation calculation and characterizations showed that the binding energy between the ions and TBP follows the sequence:Li+>Na+>K+>Mg2+.For the NaBPh4+TBP+CH2ClBr extraction system,when the Na+/Li+molar ratio,the volume fraction of TBP and the phase ratio were 2.0,50%and 1.0,the extraction efficiency of lithium ions and the separation factor of Li/Mg in single stage could reach up to 87.65%and 2260.71,respectively.The washing efficiencies of magnesium and potassium ions were 97.52%and 99.72%respectively with 2.0mol/L NaCl and 0.2mol/L LiCl as washing agent and phase ratio as 5.0.After twice stripping of the organic phase,the stripping effeciency of lithium ions could reach 96.43%with 0.1mol/L HCl as stripping agent and phase ratio as 5.0.In addition,in order to avoid the influence of acids and bases used in stripping and regeneration processes on the stability of the organic phase,the new stripping process with sodium carbonate as stripping agent was proposed.The stripping,organic phase regeneration and product preparation processes could be realized in one step.The stripping rate of lithium ions could reach 98.84%with 2.5mol/L Na2C03 as stripping agent and phase ratio as 1.0,and lithium ions were directly stripped to the aqueous phase in the form of Li2CO3.The mechanism of the extraction process was studied by combining simulation calculations and experimental characterization,the results of which showed that the binding ability of metal ions follows the sequence:Li+>Na+>K+>Mg2+.