Mg2+掺杂对H1.6Mn1.6O4锂离子筛吸附性能的影响

对由碱金属和过渡金属组成的阳离子骨架尖晶石结构,其碱土金属离子掺杂位点及对性能的影响一直缺乏研究。本文通过水热法合成了Mg~(2+)掺杂的尖晶石型Li_(1.6)Mn_(1.6)O_4(LMMO)经脱模后,得到Mg~(2+)掺杂的尖晶石型锂离子筛H_(1.6)Mn_(1.6)O_4(HMMO)。样品表征结果表明LMMO、HMMO及吸附之后的样品(r-LMMO)均呈现尖晶石结构。相同实验条件下,HMMO对锂的吸附容量为25.6 mg/g (未掺杂为25.8 mg/g),抗溶损研究发现r-LMMO溶损率为4.4%(未掺杂为5.4%)。在保持较高吸附容量条件下,掺杂显著提高其结构稳定性。Langmuir和pseudo-second-order模型能够很好的拟合HMMO对Li~+的吸附过程,DFT计算结果表明Mg~(2+)替换了16d位置的部分Li~+,使得Mg-O键强于Li-O键从而增强了吸附剂的结构稳定性。

Effect of Mg Doping on Adsorption Property of H1.6Mn1.6O4 Lithium Ion Sieve

Spinal crystals are generally constructed by alkali and transition metal elements,and the alkaline-earth metal element doped into this structure have rarely been investigated.In this work,Mg²⁺ doped spinel Li 1.6Mn1.6O₄ (LMMO)was synthesized by hydrothermal method.Mg²⁺ doped lithium ion sieve was obtained (HMMO)by extracting of Li⁺.The results of sample characterization show that LMMO,HMMO and the sample of after adsorption Li⁺ (r-LMMO)exhibit a spinel structure.Under the same conditions,the adsorption capacity of HMMO for Li⁺ was 25.6 mg/g,while the adsorption capacity of undoped H 1.6Mn 1.6O₄ (HMO)was 25.8 mg/g (C Li:6 mmol/L,pH 12,T:25°C).The results showed that the dissolution rate of r-LMMO was 4.4% while the dissolution rate of r-LMO was 5.4% (C HCl:0.6 mol/L,t:24 h).The structure stability was enhanced by Mg²⁺ doped and maintain high adsorption capacity.The Langmuir and pseudo-second-order kinetic models can well fit the adsorption process of HMMO to Li⁺.Furthermore,DFT calculations are revealed that the improvement of the structure stability of the adsorbents relies on the substitution of Li at the 16d sites by Mg²⁺.