Porous polyvinyl alcohol/polyacrylamide hydrogels loaded with HTO lithium-ion sieves for highly rapid and efficient Li+ extraction

Lithium (Li) reserves in liquid resources are significantly higher than solid lithium ores and can fully meet the growing demand for Li. Lithium-ion sieves (LIS) adsorption of Li from liquid resources is one of the most promising methods. However, conventional polymeric adsorption materials encapsulate most LIS in dense structures, leading to low adsorption capacity and slow adsorption rate. Therefore, HTO-PVA/PAAm hydrogel was synthesized from titanium-type lithium-ion sieves (HTO), acrylamide, and polyvinyl alcohol by free radical polymerization. The HTO-PVA/PAAm hydrogel is characterized by a soft three-dimensional (3D) network, continuously adjustable pore structure, high specific surface area, and excellent hydrophilicity. Accordingly, the HTO-PVA/PAAm owns an excellent Li+ adsorption capacity (22.16 and 31.31 mg·g−1 in pH 7.2 and 12 of LiCl solutions, respectively) among reported advanced adsorbents. 90 % of Li+ is desorbed within 60 min, indicating the efficient and rapid Li+ desorption response of the hydrogel. Meanwhile, this hydrogel still maintains a Li+ adsorption capacity of 90 % after eight adsorption-desorption cycles, during which Ti loss is <0.42 % in each cycle. In this work, HTO-PVA/PAAm hydrogel synthesized by an environmentally friendly and low-cost approach shows great application potential as a new strategy for Li+ adsorption from liquid resources.