Lithium selective adsorption on 1-D Mn02 nanostructure ion-sieve

摘要

β-MnO2, spinel-type Li4Mn5O_(12) and pure cubic phase MnO2 nanorod, with the size about 20-140 nm in diameter and 0.8-4 μm in length, were synthesized via a combination of hydrothermal synthesis and low temperature solid-phase reaction, more favorable to control the nanocrystalline structure with well-defined pore size distribution and high surface area than the traditional high temperature calcination process. Further, the MnO2 ion-sieves with lithium selective adsorption property were prepared by the acid treatment process to completely extract lithium from the spinel Li4Mn5O_(12) precursor with little change to the Mn-O lattice structure and the 1 -D nanorod morphology. 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 powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), N2 adsorption-desorption at 77 K, and Li~+ selective adsorption measurements. The lithium selective adsorption capacity was improved remarkably to 6.62 mmol g~(_1) at equilibrium and about 5 mmol g~(-1) at the initial lithium concentration of only 5.0 mmol 1~(-1), which is significant for lithium extraction from aqueous solutions with very low lithium content.