Extraction of Lithium from Single-Crystalline Lithium Manganese Oxide Nanotubes Using Ammonium Peroxodisulfate

In this work, a spinel single-crystalline Li_1.1Mn_1.9O₄ has been successfully synthesized using β-MnO₂ nanotubes as the self-sacrifice template. The tubular morphology was retained through solid-state reactions, attributed to a minimal structural reorganization from tetragonal β-MnO₂ to spinel Li_1.1Mn_1.9O₄. The materials were investigated as sorbents for lithium recovery from LiCl solutions, recycled using H₂SO₄ and (NH₄)₂S₂O₈. Li_1.1Mn_1.9O₄ nanotubes exhibited favorable lithium extraction behavior due to tubular nanostructure, single-crystalline nature, and high crystallinity. (NH₄)₂S₂O₈ eluent ensures the structural stability of Li_1.1Mn_1.9O₄ nanotube, registering a Li⁺ adsorption capacity of 39.21 mg g^-1 (∼89.73% of the theoretical capacity) with only 0.08% manganese dissolution after eight adsorption/desorption cycles, compared to that of 1.21% for H₂SO₄. It reveals the degradation of sorbent involves with the volume change, Mn reduction, and Li/Mn ratio depletion. New strategies, based on nanotube adsorbent and (NH₄)₂S₂O₈ eluent, can extract lithium ions at satisfactorily high degrees while effectively minimizing manganese dissolution.