Study On The Law Of Evaporation And Salt Separation Of Taihe Underground Brine And Extraction Of Lithium Carbonate By Adsorption

Lithium and its compounds are widely used.With the rise of electronics and new energy,the global demand for lithium resources has increased dramatically.Most of the lithium resources are stored in lithium-containing brine,and the process of extracting lithium from brine is simple and low in cost.With the improvement of lithium extraction technology,lithium extraction from brine has become the main mining method for lithium resources at present.There are many methods for extracting lithium from brine.The adsorption method has attracted attention because of its good selectivity to lithium ions,simple process and high recovery rate,and the key of it is the choice of adsorbent.The subject uses Taihe underground brine as raw material,combined with the characteristics of high magnesium-lithium ratio and near-saturation of sodium chloride in the underground brine of this area,the extraction of lithium carbonate by adsorption method was carried out.The optimal conditions for the preparation of aluminum-based lithium sorbents was explored.The adsorption mechanism was studied by the adsorption kinetics model and the isotherm adsorption model,which provides a basis for the industrial application of aluminum-based lithium sorbent.Lithium carbonate crude products were prepared through the processes of raw brine refining,evaporation concentration,adsorption-desorption,concentration of desorption liquid and precipitation,and then optimized each process,which provides a reference for the comprehensive utilization of underground brine resources in the region.(1)The optimum technological conditions for the refining of Taihe underground brine by "two alkali method" were studied.When the amount of soda ash and caustic soda added is 1.127 times and 1.2 times of the theoretical molar amount,respectively,the removal rates of calcium and magnesium can reach more than 99%;the concentration of calcium and magnesium in the solution is lower than 5 mg/L and the recovery of lithium is 89.33%at this time.(2)The recovery of lithium ions in evaporation process was studied.When the 56%water is evaporated,the refined brine is concentrated by evaporation.At this time,the concentration of Li+was concentrated from 0.07 g/L to 0.21 g/L,and the recovery of lithium was 60%.This process can obtain an industrial salt with a purity of 98%or more,and the salt production rate is 19.62%.(3)The preparation process of aluminum-based lithium sorbent was studied by "onestep method",and the adsorption and desorption processes were optimized.Through investigation of a series of factors,the results show that the optimal preparation conditions of aluminum-based lithium adsorbent are to add sodium hydroxide to the mixture of AlCl3 and LiCl,the Al/Li molar ratio is 1.25:1,and the end point pH is 6?7,the feed rate was 3 mL/min,the stirring rate was 100 r/min,and the reaction temperature was 75?.Through the investigation of its adsorption and desorption properties,the best conditions for adsorption were adsorption at room temperature for one hour,the adsorption capacity of it in 5 g/L lithium chloride solution reaches 15 mg/g.And the optimum conditions for desorption are 8 hours of desorption at 80?.The adsorption kinetics model and the isothermal adsorption model show that the adsorption of aluminum-based lithium sorbent conforms to the quasisecondary kinetic model and the Langmuir isotherm adsorption model,which indicates that the adsorption process is a typical chemical adsorption.(4)In the laboratory,a self-made aluminum-based lithium sorbent was applied to the underground brine of Taihe to prepare lithium carbonate.The adsorption capacity of the aluminum-based lithium adsorbent in the lithium-rich brine can reach 15.06 mg/g,and the desorption capacity was 14.11 mg/g,and the desorption efficiency reached 93.69%.When the 99.82%water of the desorbed liquor is evaporated,a high lithium liquor having a lithium ion concentration of 15.47 g/L can be obtained.According to the CO32-/Li+ molar ratio of 1.1:2,soda ash is added to the brine to obtain a crude lithium carbonate having a purity of 79.74%.The recovery of lithium is 73.67%at this time.The recovery rate of lithium ion in the overall process is 37%.The process is simple and feasible,and it has guiding significance for the comprehensive utilization of underground and brine water resources in Taihe,Jiangxi province.