Study On Synthesis Of Lithium Ion-Sieve Material By Sol-Gel

High purity γ-MnO2 was prepared by sol-gel precursor method using lithium nitrate, manganese nitrate, citric acid and ethylene glycol as raw materials. The structure , sieve property and reaction mechanism were characterized for both precursor LiMnaO4 and X-MnO2 by chemical analysis, XRD, TG-DTA, IR, SEM ,AAS and BET.1 The molar ratio of citric acid and ethylene glycol was 0.25. molar ratio of lithium nitrate and manganese nitrate was 0.6. After all components above were mixed, the system was esterifying at 140℃ for 4 hours and refluxing at 105℃ for 2 hours. Dried gel was calcined at 600℃ for 8 hours to obtain pure normal spinel LiMn204 . Initial particle diameters of product were about 100 nm mainly.2 The reaction mechanism of sol-gel process was investigated. Citric acid reacts with metal cations to produce citrate and chelate compound of citric acid. The structure of chelate compound is mainly as eight-ring of single molecule having four coordinations and double-molecule having four coordinations. The pruduct obtained at last has a three-dimensional gel net-work structure in which metal cations are highly distributed.3 High pure γ-MnO2 was prepared by leaching LiMn2O4 in l.Omol.L-1 HC1 for 96 hours. The adsorptive properties of γ-MnO2 were studied. The results based on the investigation showed that:(l)The lithium adsorption capacity of γ-MnO2 prepared by sol-gel increased with enhancement of pH. It achieved to 4.82 mmol.g-1 at pH 12. The lithium adsorption quantity increased with raise of concentration of lithium. The lithium adsorption quantity had no obvious change with temperature.(2)γ-MnO2 possesses specific adsorption selectivity for lithium ion. The distribution coefficient Kd of Li+ and Na+ were 429.3 and 0.57respectively at pH 8.0, and the separation coefficient aa was754.0. Hence, γ-MnOa will be expected to extract micro-lithiumfrom salt-lake brine and seawater.The study above illuminated that γ-MnO2 prepared by sol-gel precursor method possesses the merits of lower synthesis temperature, smaller size, more homogeneous fineness and larger surface area and its ion-sieve properties got more improvement.