Enhanced lithium extraction from aqueous solutions using multi-scale modified titanium adsorbent

It is highly appealing to use titanium-based adsorbents (like H2TiO3 (HTO)) that have a high capacity and selectivity to directly extract Li+ from an aqueous solution. However, HTO still faces the problems of low actual adsorption capacity and dissolution of Ti4+, and the application of powder adsorbents is limited by poor fluidity and poor recyclability. In this work, a multi-scale modification strategy was adopted. At the atomic-scale, we prepared Ni-doped HTO-Ni-2 % powder which exhibited higher adsorption capacity (33.27 mg/g) and lower dissolution rate of Ti4+ (2.2 %) compared to undoped HTO (29.73 mg/g and 2.63 %). Computational studies showed that Ni doping replaced Li in the (Li) layer, resulting in more stable NiO bonds and enhanced electronic transition ability. At the micro-scale, we have achieved successful granulation of HTO-Ni-2 % using ethylene vinyl alcohol (EVOH) as a binder for the first time. Owing to the increased hydrophilicity by EVOH, the spherical adsorbents exhibited impressive performance, achieving adsorption equilibrium in a short time while maintaining a considerable adsorption capacity (24 h, 10.2 mg/g), and having lower Ti4+ dissolution. These results have significant implications for developing efficient adsorbents for lithium extraction.