【作者】 刘维娜；

【导师】 董殿权；

【作者基本信息】 青岛科技大学 ， 化学工艺， 2009， 硕士

【摘要】 以乙酸锂、乙酸镍和乙酸锰为主要原料,采用溶胶-凝胶法,合成出一系列掺镍的锂锰氧化物LiNixMn2-xO4(x=0.00, 0.05, 0.10, 0.20)作锂离子筛前驱体。通过正交试验得到合成锂离子筛前驱体的最佳条件为:镍的掺杂量x为0.05、螯合剂为柠檬酸、焙烧温度700℃、焙烧时间8h。对其尖晶石结构及酸稳定性进行了测定,并选用0.5mol/L过硫酸铵做改型剂对合成的锂离子筛前驱体进行酸处理,制得锂离子筛。测定了其对锂离子的饱和交换容量、pH滴定曲线等离子交换性能。经测定:LiNi0.05Mn1.95O4为尖晶石结构、酸稳定性好,在酸改型过程中Mn2+的溶出率仅为0.31%。酸改型后制得的锂离子筛对锂具有较高的选择性,对0.1mol/L Li+溶液的饱和交换容量达36.72mgLi+/g离子筛。测定了锂离子筛的离子交换热力学。作出15℃, 25℃, 35℃, 45℃下锂离子筛的H+-Li+交换等温图,利用Pitzer电解质溶液理论,计算出该离子交换体系的活度系数,得Kielland图,并进一步得到H+-Li+交换的平衡常数及其它热力学参数( K a,ΔG0,ΔH0,ΔS0)。ΔG0LHi为负值,表明所合成的锂离子筛对Li+的选择性大于原来可交换阳离子H+的选择性,吸附锂的过程是自发过程(ΔG0<0)。该离子交换反应是放热反应。测定了锂离子筛对锂的离子交换动力学。得到25℃时锂离子筛在0.005, 0.025和0.050 mol/L的Li+溶液中吸附锂的离子交换动力学数据。用缩核模型处理所得的动力学数据,确定锂离子筛吸附Li+时的控制步骤是颗粒扩散控制(PDC),同时得到该实验条件下锂离子筛吸附Li+的动力学方程和颗粒扩散系数De。更多还原

【Abstract】 A series of Ni-doped lithium manganese oxide LiNixMn2-xO4(x=0.00, 0.05, 0.10, 0.20) were synthesized as lithium ion-sieve precursors by a sol-gel method using acetic lithium, nickel and manganese as raw materials. The optimum conditions of preparing lithium ion-sieve precursors were: citric acid as chelating agent, calcining heat 700℃, calcining time 8h, amount of x 0.05, which were obtained by orthogonal experiments. Their spinel structures and acidic stability were studied. The lithium ion-sieve noted as LiNiMn-H was obtained by acid-modifying the gained LiNi0.05Mn1.95O4 by 0.5 mol/L (NH4)2S2O8. The ion-exchange properties of LiNiMn-H such as its saturation capacity for alkali mental ions and the pH titration curves for Li+, Na+ and K+ were determined.The results showed that the dissolving ratio of Mn2+ from the obtained spinel LiNi0.05Mn1.95O4 was only 0.31% during the acid-modified process and the saturated ion-exchange capacity of the obtained lithium ion-sieve LiNiMn-H for 0.1mol/L Li+ solution was 5.29 mmol (36.72mg)Li+/g , which showed a high selectivity for Li+.The ion-exchange thermodynamics of lithium ion-sieve was determined. The exchange isothermal diagrams of H+-Li+ on lithium ion- sieve were measured at 15℃, 25℃, 35℃and 45℃respectively. The average activity coefficients of the electrolyte and the Kielland diagrams were calculated by using Pitzer electrolyte solution theory, then the other thermodynamic constants such as equilibrium constant K a,ΔG0,ΔH0andΔS0during the exchange process were computed. The ion exchange free enthalpy of lithium ion-sieve for Li+ were negative, which indicated that its selectivity for Li+ was higher than the original ion H+, the ion exchange process carried out spontaneously (ΔG0<0), and the exchange process was exothermic. The ion-exchange dynamics of lithium ion-sieve was studied at 25℃. The kinetics curves of lithium ion-sieve for Li+ during the ion-exchange process were measured in 0.005, 0.025和0.050mol/L Li+ solutions respectively. The shrinking-core model was choosen to deal with the dynamics dates of the ion exchange process, and the kinetics controlled step was determined to be particle diffusion control (PDC). Besides, the kinetics equations and diffusion coefficients (De) of the lithium ion-sieve for Li+ were obtained at the experimental conditions .更多还原