Preparation And Adsorptive Properties Of Adsorbents For Lithium

The spinel-type manganese oxide is suitable as a lithium-selective adsorbent because it has a high chemical stability against lithium insertion-extraction in the aqueous phase as well as selective lithium uptake. Current work is mainly focused on the synthesis of spinel-type manganese oxide, its adsorptive properties, and application in membrane-type lithium-ion.The spinel phase y-MnOOH was prepared by hydrothermal method at 140℃with 2.5% of ethanol and 0.5g of KMnO4. The LiMnO2 was synthesized by reacting spinel phase y-MnOOH with LiOH solution. The lithium ion-sieve precursor Li1.6Mn1.6O4 was obtained by thermal treatment of LiMnO2 at 400℃. The extractability of lithium from the Li1.6Mn1.6O4 samples was investigated using a 0.5 M HC1 solution; the Li+ extractability reached 98%. The percentage of the dissolution of manganese during the acid treatment was less than 2%.The adsorptive properties of lithium-ion were investigated. The equilibrium was reached within 48h. There was strong responsive behavior of Li+uptake to pH and had a maximum uptake when the pH was 12, but the uptake depressed with the loss of manganese when the pH was higuer than 12. The equilibrium uptake was adjacent for different initial concentration of lithium solution. The adsorption data followed Langmuir's equation. The maximun lithium uptakes were 27.02 and 32.79mg-g-1 at 25 and 40℃, respectively. The study of elution perform well and the elution rate reached to 95%. Four adsoption/desorption cycles of lithium ion were carried out. The decrease of lithium uptake was low, showing that the adsorbent has high stability. In the solution containing Li+,Na+,K+,Ca2+,Mg2+, lithium uptake was high, while the uptakes of other metal ions were low. This shows that the present adsorbent has high selectivity toward Li+ion.A Membrane-type adsorbent was prepared with adding Li1.6Mn1.6O4 to the solution of PVDF and mixed vigorously. The initial concentration of PVDF with the suitable viscosity of suspension was 16%. The ultimate adsorption capacity was 27.45×102mg/cm2 with 2% of Li1.6Mn1.6O4.