Nanoscale-controlled lithium ion-sieve based on MnO₂·0.5H₂O: Microfluidic synthesis and brine extraction performance

Manganese oxide lithium - ion sieves are among the most promising industrial adsorbents. This study is the first to apply membrane - dispersed microreactors for synthesizing monodisperse MnCO₃ nanoparticles, which is a problem that is coupled with novel two - stage thermal activation, which optimizes the Li_1.6Mn_1.6O₄ spinel structure with Li ⁺ diffusion channels. The results showed that the optimal adsorption conditions were identified as follows: pH = 10, initial Li⁺ concenteation = 1000 mg/L, adsorption time = 12 h, and temperature = 25 °C, with a maximum capacity of 77.66 mg/g. The microfluidically synthesized MnO₂·0.5H₂O exhibits superior Li ⁺ adsorption performance and exceptional Li ⁺ selectivity (order: Li⁺ > Na⁺ > Mg²⁺ > K⁺). Moreover, it retains an adsorption capacity of ≥ 58.67 mg/g after five cycles, highlighting the advantage of the microfluidic approach in enhancing material properties. The study offers technical assistance and theoretical guidance for the recovery of lithium from wastewater resources.