| Lithium reserves(counted by LiCl) in Qarhan Salt Lake reach up to8.246million tons, accounting for35.9%of China’s salt lake lithium reserves. Qarhan Salt Lake is one of the most valuable lakes for developing. However, the lake couldn’t be utilized because its Li/Mn ratio is as high as400. In the paper, ion-sieves with high Li/Mn ratio were prepared and their performances were studied to investigate its possibility in extracting lithium from brine.Solid phase method and hydrothermal-solid phase method were used to synthetize two MnO2ion-sieves, respectively. XRD, SEM, BET, IR and TG-DTA were used to characterized obtained materials. The effects of adsorption time, initial Li+concentration, initial OH-concentration and impurities on adsorption capacities were investigated, then the experiments of extracting lithium from Qarhan and desorption-adsorption cycle process were done.The synthesis studies showed that Li1.33Mn1.67O4with cubic phase could be prepared in short time by solid phase method. Li1.6Mn1.6O4with cubic phase could be prepared by hydrothermal-solid phase method, but its preparation process was complex. γ-MnOOH and o-LiMnO2must be synthetized first, then Li1.6Mn1.6O4was obtained by calcining o-LiMnO2. The adsorption performance studies showed that pseudo-second-order kinetic model showed good fitting result in adsorption process; Langmuir model showed good fitting result in adsorption mechanism, which was monolayer adsorption; The concentration of OH-had great effect on adsorption capacity and maximum adsorption capacities were5.70and6.30mmol/g, respectively; Selectivity analysis showed that both two ion-sieves had high selectivity to Li+and their adsorption capacities were3.55and3.88mmol/g in extracting lithium from brine; Desorption-adsorption cycling process showed that lithium ion-sieve could be cycle used. |
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