Acta Phys. -Chim. Sin. ›› 2009, Vol. 25 ›› Issue (07): 1279-1284.doi: 10.3866/PKU.WHXB20090712

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Synthesis of LiNi0.05Mn1.95O4 and Its Ion-Exchange Thermodynamics for Li+

DONG Dian-Quan, LIU Wei-Na, LIU Yi-Fan   

  1. College of Chemical Engineering, Qingdao University of Science&Technology, Qingdao 266042, Shandong Province, P. R. China
  • Received:2009-01-13 Revised:2009-03-16 Published:2009-06-26
  • Contact: DONG Dian-Quan E-mail:dqdong@qust.edu.cn

Abstract:

A spinel lithium manganese oxide doped with nickel (LiNi0.05Mn1.95O4) was prepared by a sol-gel method using acetic lithium, nickel and manganese as rawmaterials. The lithiumion-sieve (denoted as LiNiMn-H) was obtained by acidification of the obtained LiNi0.05Mn1.95O4 with 0.5 mol·L-1 (NH4)2S2O8. After testing, we found that the dissolution ratio of Mn2+ fromLiNi0.05Mn1.95O4 during the acid-modification process was only 0.31% (w, mass fraction) and the saturation ion-exchange capacity of LiNiMn-Hfor Li+ was 5.29 mmol (36.72 mg) Li+/g ion-sieve. The exchange isothermal curves of LiNiMn-H in the H+-Li+ system were measured at 15, 25, 35 and 45 ℃ and the average activity coefficients of the electrolyte were calculated using Pitzer electrolyte solution theory. Other thermodynamic constants, such as the equilibrium constants Ka, △Gm, △Hm, and △Sm, were calculated during the exchange process. We conclude that the equilibrium constants reduce with the increase in temperature and that the selectivity of LiNiMn-H for Li+ is higher than the original ionH+. The exchange process is exothermic and the adsorption process occurs spontaneously (△Gm<0).

Key words: LiNi0.05Mn1.95O4, Lithiumion-sieve, Thermodynamics, Pitzer electrolyte solution theory

MSC2000: 

  • O642