Toward sustainable lithium recovery from brine: a hydrothermal carbon-coating strategy for minimizing Mn dissolution in ion-sieve adsorbents

Global lithium demand has heightened interest in direct extraction from salt-lake brine. Mn-based ion sieves (HMOs) offer high capacity, fast kinetics, and low cost but suffer from Mn dissolution. This study reports a low-dissolution HMO@Hy sieve prepared via hydrothermal carbon coating. The oxygen-rich carbon layer curbs metal leaching without performance loss seen in amorphous carbon coatings, reducing Mn dissolution from 2.01% to 1.06%. The material exists as loose powder with a uniform 2–3 nm coating and adsorbs 21.1 mg/g from real brine within one hour. First-principles calculations show the carbon-doped coating raises surface Mn valence, reducing charge density and limiting dissolution during desorption. Granulation and cycling tests confirm practical potential: one ton of adsorbent processes 114 tons brine weekly, yielding 0.49 tons Li₂CO₃ and ¥42,800 economic benefit. This non-metallic coating strategy enhances HMO stability for sustainable lithium recovery.