Synthesis Of New Composite Based On Titanium And Study On Lithium Adsorption Property

Two ne, w spinel composites based on titanium was synthesised, they wereinorganic ion exchangers, Li4Ti₅O₁₂ and Mg₂TiO₄. After disposed with dilute HClsolution, Li-Ti-O(H) and Mg-Ti-O(H) ion-exchanger were prepared to determinecharacteristices of ion exchange, kinetics, thermodynamics, and results list here.Spinel Li₄Ti₅O₁₂ was prepared by precipitation/crystallization, grinding, SOl-gelmethod. Determined by saturation exchange capacity of Li-Ti-O(H), orthogonalexperiment ives out the best preparation method as follows: sol-gel method, synthesisat temperature 700-800℃, n_Li:n_Ti=1.04, roasted for 6h. The product was pure Li₄Ti₅O₁₂characterized by XRD mensuration. Saturation exchange capacity of Li-Ti-O(H) was29.78mgLi⁺/g exchanger. Ion exchange dynamics of Li-Ti-O(H) was studied at 25℃,reaction was finished in 2 hours with exchange ratio up to 90%. Shrinking-coremodel was used to treat with the data of ion exchange dynamics when the exchangeratio was less than 90%, linear correlative coefficient was more than 0.995.Spinel Mg₂TiO₄ was synthesised as follows: prepared by sol-gel method,synthesis at temperature 700℃, n_Mg:n_Ti=2.6:1, roasted for 4h. Determined by extractedratio of Li⁺ and Ti⁴⁺, 0.5mol/L HC1 was fit to get Mg-Ti-O(H). Saturation exchangecapacity of Mg-Ti-O(H) was 45.85mgLi⁺/g exchanger, it was two times of Li-Ti-O(H).The thermal behavior and phase transformation of gel powders were investigated bythe diferentiat thermogravimetry-scaning calorimetry (TG-DSC). The result show thatsolid-solid reaction happens at temperature of 600-7000℃. Compared with XRDdetermination, resultant of the reaction was proved to be spinel Mg₂TiO₄.Mg-Ti-O(H) ion-exchanger has a special selectivity with Li⁺ consulted fromdistribution coefficients experiment of alkali metals. Pitzer electrolyte solution theory was used to work out activity coefficients of H⁺-Li⁺ ion exchange systems attemperature of 25℃. Also equilibrium constants and thermodynamic parameter ofH⁺-Li⁺ ion exchange systems were obtained through the Kielland diagram. Thenequilibrium constants (K_aH^Li) were worked out to be 14.2379. The process of Li⁺replace H⁺ is a spontaneously process, AG°was-6583.5J/mol. Ion exchangedynamics of Mg-Ti-O(H) was studied at 25℃, reaction was finished in 2 hours withexchange ratio up to 90%. During the whole exchange process, the exchange dynamicsequation and diffusion coefficients were got from Fick first-rule of diffusion whichwas used to deal with dynamics date, linear correlative coefficient was more than 0.97.