Study On Preparation And Properties Of Lithium Ion Adsorbent

Lithium and its compound are widely used, has a great value for a country’s develop, the demanded quantity will rise rapidly. Now more than90%of lithium products come from brine, because great majority of salt lakes of our country have a high Mg/Li mole ratio, and recovering lithium from salt lake with a high Mg/Li mole ratio is very difficult. The usual techniques of recovering lithium from brine are precipitation, calcining-leaching, extraction, but their application are restricted because of their defects. Adsorption method of recovering lithium attracts researchers’ attention, because of it can recover lithium from brine directly.Developing excellent lithium adsorbents is very important for adsorption method of recovery lithium, the adsorbents must have high saturated adsorption capacity, excellent selectivity, can recycling use, cheap and no harming to the environment. The main synthesis methods of inorganic ion sieves are solid phase method, hydrothermal method and sol-gel method. Precursor LiMn2O4was synthesized with LiOH·H2O and Mn3O4by solid phase method in this research, lithium adsorbent λ-MnO2was obtained when LiMn2O4was treated with acid. The crystrall structure of LiMn2O4and λ-MnO2were investigated by XRD, TG-DSC and SEM, discussed the effect of synthesis conditions to the crystal structure of LiMn2O4and saturated adsorption capacity of λ-MnO2, and determined distribution coefficient Kd, separation factor a and pH titration curves of λ-MnO2. The results showed that calcination temperature and calcination time had an effect on the crystal structure of LiMn2O4and the saturated adsorption capacity of λ-MnO2, but the effect isn’t significant. The crystal structure of λ-MnO2did not change, still remain spinel type, showed that the extraction of Li+carried on topotactically, the lithium extraction ratio reached95%. The saturated adsorption capacity of lithium adsorbent λ-MnO2reached30.9mg/g, this is a very high value among the same lithium adsorbent, and it also presented excellent Li+selectivity. When the pH at a range of5to13, the saturated adsorption capacity of λ-MnO2increased with pH value rised, when the pH≤11, inceased slowly, when the pH≥11, increased rapidly, which indicated that a certain concentration of OH" can promote adsorption reaction. Adsorption process correspond to pseudo-second order kinetic model, isothermal adsorption process correspond to Freundlich isothermal adsorption model.