Enhancing adsorption capacity and structural stability of Li1.6Mn1.6O4 adsorbents by anion/cation co-doping

Abstract

Modifying the structure of Li_1.6Mn_1.6O₄ (LMO) to enhance its structural stability and adsorption capacity is an effective method to generate materials to recover Li⁺ ions from mixed solution. Herein, the co-doping of trace non-metal ion (S) and metal ion (Al) into Li_1.6Mn_1.6O₄ (LMO-SAl) is established and shows excellent Li⁺ adsorption capacity and Mn anti-dissolution properties. The adsorption capacity (when [Li⁺] is 6 mmol L⁻¹) is increased from 26.1 mg g⁻¹ to 33.7 mg g⁻¹. This is attributed to improved charge density via substitution of S at O sites, which facilitates the adsorption/desorption process. The Mn dissolution is also reduced from 5.4% to 3.0% for LMO-SAl, which may result from the stronger Al–O bonds compared to Li–O bonds that enhance the structural stability of the LMO. The ion-sieving ability of the co-doped material goes by the order of K_d (Li⁺ > Ca²⁺ > Mg²⁺ > Na⁺ > K⁺), indicating that Li⁺ can be efficiently separated from Lagoco Salt Lake brine. These results predict that lithium ions are effectively adsorbed from brine by the co-doped LMO material, which manifests the feasibility of lithium recovery and provides basic data for further industrial applications of adsorption.