Highly Efficient, Stable, and Recyclable Hydrogen Manganese Oxide/Cellulose Film for the Extraction of Lithium from Seawater

The extraction of lithium from seawater has attracted much interest as a means to meet increasing demand for lithium with the rapid expansion of the electric vehicle and electronics markets. Herein, a renewable and recyclable hydrogen manganese oxide (HMO)-modified cellulose film was developed and investigated toward the extraction of lithium from lithium-containing aqueous solutions. The porous film was characterized, and its extraction efficacy and selectivity toward lithium from an aqueous solution (ppm level) and seawater (ppb level) were investigated. The HMO/cellulose film exhibited a higher Li⁺ adsorption capacity (21.6 mg g^-1 HMO) than HMO/polymer (e.g., poly(vinyl chloride) or poly(vinylidene fluoride)) films, which have been examined in the literature for lithium extraction, because of its multidimensional porosity and hydrophilicity. The kinetics analysis based on a pseudo-second-order model indicated that the Li⁺ extraction rate of the HMO/cellulose film was 3 times higher than that achieved by the HMO particle alone (i.e., 0.075; cf. 0.023 g mg^-1 h^-1). Furthermore, the HMO/cellulose film displayed high selectivity for Li⁺ when exposed to seawater-the extraction of Li⁺ reached 99%, whereas that of the other ions present in seawater (i.e., Sr²⁺, K⁺, and Ca²⁺) was <4%. In addition, the adsorption capacity and mechanical strength of the HMO/cellulose film remained stable even after eight adsorption-desorption cycles. The present findings demonstrate the potential of the present HMO/cellulose film for the recovery of Li⁺ from seawater or wastewater.