The preparation path, adsorption characteristics and manganese dissolution loss mechanism of manganese-based ion-sieve MnO2·0.5H2O for liquid phase lithium resource recovery

Lithium ion-sieve with selective adsorption capacity is an important research direction in the field of recovering lithium from brine. The lithium ion-sieve precursor Li 1.6 Mn 1.6 O 4 was efficiently prepared using a combination of the hydrothermal method and solid-phase calcination. Subsequently, a highly adsorbent with high adsorption capacity was obtained through a process involving pickling and Li leaching. The impact of different preparation routes and conditions on both the intermediate product LiMnO 2 and the ion-sieve precursor Li 1.6 Mn 1.6 O 4 were investigated. Under conditions of 25 °C, pH 9, and an initial Li + concentration of 100 mg/L, the initial adsorption capacity and Mn dissolution loss are relatively optimal. After 10 cycles, the adsorption capacity stabilizes at 25–30 mg/g, However, Mn dissolution loss is unavoidable, it stabilizes between 2.0 % and 2.5 %. The selective adsorption of Li + remains effective even in the presence of Ca 2+ , Mg 2+ , Na + , and K + interference. Li desorption and Mn dissolution loss were investigated using density functional theory, Fukui function, electron orbital theory, and density of states. The introduction of H + during the pickling process induced structural modifications in the ion-sieve precursor Li 1.6 Mn 1.6 O 4 , leading to a decrease in Mn-Mn bonds, Mn-O bonds, and Li-O distances. Initially, Li + at each site of Li 1.6 Mn 1.6 O 4 had an equal probability of being replaced by H + . Subsequent desorption occurred far away from the desorption point. The loss of Mn 3+ in Li 1.6 Mn 1.6 O 4 resulted in an increased electrophilic attack index at the H + substitution site, and the 3d orbital electrons of Mn 3+ migrate to the 4d and 2p orbitals to seek stability.