Synthesis of Li4Ti5O12 and its exchange kinetics with Li+

Lithium ion sieve IE-H was obtained by acid-modifying LiTi5O12 precursor, which was prepared by solgel method. Its properties of ion-exchange for Li+ and Na+, such as the saturation capacity of exchange and pH titration curves, were determined. The Li4Ti5O12 precursor and lithium ion sieve IE-H were characterized by XRD. The ion exchange mechanism was judged by broken phase contact method. The kinetics of the ion sieve with Li+ was depicted by the shrinking-core model. It was shown that both the Li4Ti5O12 and lithium ion sieve IE-H are spinel structure. After acid treatment, the extraction ratio of Li+ from Li4Ti5O12 was 19.6%- 81.5%, while the extraction ratio of Ti4+ was less than 4.2%; Further, the obtained ion sieve IE-H showed superior saturated ion exchange capacity for Li+, with a value of 5.95 mmol-g(-1). In addition, the reaction of the ion sieve with Li+ was determined to be controlled by particle diffusion. Finally, different kinetics equations and diffusion coefficients of the ion sieve IE-H for Li+ at 25 degrees C were obtained with the Li+ concentrations of 20.0 mmol . L-1 and 5.0 mmol . L-1.