Study On Separation Properties Of Lithium Ion-Sieve Material And Its Mechanism

Spine structure λ-MnO2 showed excellent "ion-sieve" properties for Li+ ,which possessed high uptake and selectivity for Li+, and could be used as micro-lithium extraction from seawater brine.Spine structure LiMn2O4 was synthesized by a solid-state reaction. The concentrations of lithium ion manganese ion in the acid delithiated supernatant, and the contents of lithium manganese in the solid acid delithiated products ,were determined by atomic absorption spectrometry and chemical analyses. The influences of LiMn2O4 sizes solution acidities on the batch acid digestion were studied. The size of LiMn2O4 didn't affect results. When HC1 concentration was smaller than Imol-L-1, the extractability of lithium ion and manganese ion increased with acidity, but Li/Mn in the solution was 2 or so approaching the theoretical value. When the acidity was higher, more lithium ions were extracted from LiMn2O4, and fewer lithium ions were remained in theλ-MnO2. The best conditions for batch acid-delithiated were that LiMn2O4 was treated by Imol-L-1 acid for 120h.The best conditions for column method were: the size of LiMn2O4 between 80-120 sieves, HC1 concentration 0.5mol L-1. In the column method, the acid was made full use. The loss of samples was smaller. Extraction/insertion could be performed continuously. The column method was a better method for Li+ extraction/insertion.The adsorptive properties of λ-MnO2 with high purity were investigated. pH values of solution significantly affected the ability of Li+ insertion. When pH=12, uptake was 3.80mmol/g. Distribution Coefficients Values of alkali metal ions were determined by batch method. Kd value of Li+ was 34063.7 in pH=6.5 . The selectivity sequence for alkali metal ions was Li+>Rb+>Cs+>K+>Na+. The results showed that λ-MnO2 was applied to extract Li+ from brine, which possessing an alluring prospect.XRD SEM IR chemical analyses showed λ-MnO2 maintained spine structure in the Li+ extraction/insertion process. Lattice parameters slightly changed. Li+ extraction/insertion were topotactic reactions, which could be represented as:LiMn2O4 (spine structure) λ-MnO2 ( spine structure)In this paper, the color of solutions underwent different changes in the Li+ extraction/insertion process. So it can be thought #-MnO2 underwent a more complicated reaction mechanism than redox mechanism.