Research on the manganese dissolution mechanism of ion-sieve in acid desorption by first-principles calculation & characterizations

Abstract

The manganese dissolution of lithium ion-sieves was high in the chemical acid desorption process. The mechanism was investigated by using first-principles calculations, measured X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) characterizations. In addition, the electrically switched ion exchange (ESIX) technology was selected to verify the conclusions. It was found that when H+ inserts into ion-sieve, the structure of the crystal surface changes and Mulliken bonding populations of Mn on the surface decreases, which means the strength of Mn-O covalent bond is decreased. Meanwhile, the electronic cloud density of manganese increases and the valence state of manganese decreases. The manganese with low valence exists unstably in acid solution, it can react with H to produce MnO2 as well as divalent manganese, which is easy to dissolved. It can be concluded that the insertion of H+ into crystal resulting in unstable Mn on the surface and causing manganese dissolution in chemical desorption of ion-sieve.