Li4Ti5Ol2的合成及对Li+的离子交换动力学

用溶胶-凝胶法合成出Li4Ti5Ol2, 对其进行了酸改性, 制得锂离子筛IE-H. 测定了IE-H对Li+、Na+的饱和交换容量和pH滴定曲线等离子交换性能, 并对其进行了X射线衍射分析, 同时采用中断接触法判断该离子交换反应的控制机理, 用缩核模型描述离子筛IE-H交换Li+的动力学. 结果表明, 合成出的Li4Ti5Ol2和锂离子筛IE-H均为尖晶石结构; 用不同浓度HNO3溶液处理Li4Ti5Ol2时, Li+的抽出率为19.6%-81.5%, Ti4+的抽出率在4.2%以下; 锂离子筛IE-H 对Li+的饱和交换容量较高, 达到5.95 mmol·g-1, 离子筛IE-H交换Li+的控制步骤是颗粒扩散控制(PDC), 得到了25 ℃, Li+浓度为20.0 mmol·L-1和5.0 mmol·L-1时锂离子筛交换Li+的动力学方程和颗粒扩散系数.

Synthesis of Li4Ti5O12 and Its Exchange Kinetics with Li+

Lithium ion sieve IE-H was obtained by acid-modifying Li4Ti5Ol2 precursor, which was prepared by sol-gel method. Its properties of ion-exchange for Li+ and Na+, such as the saturation capacity of exchange and pH titration curves, were determined. The Li4Ti5Ol2 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 Li4Ti5Ol2 and lithium ion sieve IE-H are spinel structure. After acid treatment, the extraction ratio of Li+ from Li4Ti5Ol2 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 ℃ were obtained with the Li+ concentrations of 20.0 mmol·L-1 and 5.0 mmol·L-1.