Preparation Of Modified Aluminum Adsorbent And Study On Lithium Extraction Performance

With the rapid development of new energy industry,the supply of lithium resources has become a key factor in the development of new energy in China.China is rich in lithium resources,but most of them exist in salt lake brine,so it is of great significance to exploit salt lake to extract lithium.Salt lakes are distributed in Qinghai,Tibet and other areas,and most of them are ecologically fragile areas.The use of aluminum salt adsorbent for lithium extraction from salt lake meets the requirements of green production,no matter from the preparation of aluminum salt adsorbent to lithium extraction process.Aluminum salt sorbents have the characteristics of simple preparation and good stability,but the adsorption capacity of aluminum salt sorbents is low.How to improve the adsorption capacity efficiently is a hot issue in current research.Therefore,in order to improve the adsorption capacity of ZSM-5 molecular sieve,aluminum salt adsorbent was prepared by coprecipitation method and hydrothermal method respectively.The main research contents of this paper are as follows:（1）Firstly,the aluminum salt adsorbent prepared by coprecipitation method was systematically studied.Using Al Cl₃·6H₂O,LiCl and Na OH as raw materials,the optimal synthesis conditions were obtained by single factor experiment:Al/Liwas 2,the co-precipitation temperature was 60°C,and the reaction endpoint p H was 7.The effective component of the adsorbent was LiCl·2Al（OH）₃·n H₂O characterized by XRD and FT-IR,and the microstructure of the adsorbent was characterized by SEM.The adsorption and desorption properties of the aluminum salt adsorbent synthesized under the optimum conditions were systematically studied.The optimum adsorption conditions were obtained:adsorption time of 4 h,adsorption temperature of 50°C,solution p H of 7,adsorption concentration of 10 g/L,and adsorption capacity of 4.97mg/g under the optimum adsorption conditions.The optimum desorption conditions were as follows:desorption time 9h,desorption temperature 60°C,solution p H 7,the optimum desorption rate was 57.4%.The kinetic analysis shows that the adsorption process fits the second-order kinetic model.（2）In order to simplify the operation process,Al（NO₃）₃·9H₂O and LiNO₃ were directly prepared as aluminum salt adsorbent by urea hydrothermal method.The optimum Al/Lifor synthesis of LiAl-LDHs is 2 by single factor experiment.SEM characterization showed that hydrothermal LiAl-LDHs had higher crystallinity and clearer laminar structure.The LiAl-LDHs prepared by hydrothermal method is LiAl2（OH）7·x H2O type.The optimal adsorption conditions for hydrothermal LiAl-LDHs were as follows:adsorption time 360 min,temperature 40°C,p H 7;The adsorbent concentration was 10 g/L,and the optimum adsorption capacity was 5.10mg/g.The desorption rate of hydrothermal LiAl-LDHs was 59.8%by desorption experiment.The adsorption process of hydrothermal LiAl-LDHs also accords with the second-order kinetic model.（3）The synthesized ZSM-5 molecular sieve was loaded into LiAl-LDHs/ZSM-5composite adsorbent.First,ZSM-5 molecular sieves were prepared by seed assisted method.XRD and FT-IR spectra proved that ZSM-5 molecular sieves were successfully prepared,and most of the molecular sieves were characterized by SEM as pupa-like.The optimal ratio of LiAl-LDHs/ZSM-5 was 1:2.By XRD,FT-IR and SEM,LiAl-LDHs was successfully loaded onto ZSM-5 molecular sieve by hydrothermal method.The optimal adsorption conditions and desorption rates of LiAl-LDHs/ZSM-5 composites were as follows:adsorption time 360 min,temperature 25°C,p H 7,adsorbent concentration 10 g/L,and adsorption capacity 6.24 mg/g under the optimal conditions.The desorption rate was 58.4%.The adsorption process of LiAl-LDHs/ZSM-5 composite also conforms to the second-order kinetic model.