以MnSO4H2O和(NH4)2S2O8为原料通过控制水热反应条件合成了纯的四方相β-MnO2纳米氧化物, 进一步通过低温固相法制备了立方相Li4Mn5O12, 经酸浸脱锂后得到对Li+具有特殊选择性的MnO2离子筛. 用XRD、HRTEM、SAED、吸附等温线、吸附动力学及共存金属离子的分配系数等手段对产物的晶相结构和Li+选择性吸附性能进行了研究. HRTEM和SAED图像表明氧化物MnO2、前驱体Li4Mn5O12和离子筛MnO2均为低维纳米棒. 离子筛的最大吸附量达到6.6 mmol/g, 且当Li+初始浓度仅为5.0 mmol/L时, 离子筛的吸附量即可达到约5.0 mmol/g, 这对于在海水或锂离子浓度极低的盐湖卤水提锂具有重要的实用意义.
Pure β-MnO2 oxide was synthesized by hydrothermal synthesis of MnSO4H2O and (NH4)2S2O8. Spinel-type Li4Mn5O12 precursors were synthesized via low temperature solid-phase reaction. Furthermore, MnO2 ion-sieves with Li+ selective adsorption property were prepared by the acid treatment process to completely extract Li+ from the spinel Li4Mn5O12 precursor. The effects of hydrothermal and solid-phase reaction process on the nanostructure, chemical stability and ion-exchange property of the ion-sieve material were examined with XRD, HRTEM, SAED, and Li+ selective adsorption measurements. The results show that Li4Mn5O12 precursor and final MnO2 ion-sieve are effectively controlled within low-dimensional structure, indicating that low temperature solid-phase reaction is more favorable to control the nanocrystalline structure than traditional high-temperature calcination process. The Li+ selective adsorption capacity is improved remarkably to 6.6 mmol/g at equilibrium and about 5.0 mmol/g at the initial Li+ concentration of only 5.0 mmol/L, which is significant for lithium extraction from aqueous solutions with very low lithium content.
参考文献
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