Insight into the synergistic mechanism of Co and N doped titanium-based adsorbents for liquid lithium extraction

The titanium-based lithium ion-sieve (H2TiO3, abbreviated as HTO) is considered one of the most promising adsorbents for liquid phase lithium extraction technology because of its environmental friendliness and low cost. However, the actual lithium adsorption capacity of HTO is far from the theoretical maximum due to the sluggish kinetics of Li+ and H+ exchange influenced by the lamellar structure. Herein, we introduce a cobalt and nitrogen co-doped H2TiO3 lithium ion-sieve (abbreviated as Co/N-HTO-LIS). It has been demonstrated that the doped Co atoms partially replace Ti sites in native lattice while allochthonous N atoms prefer occupying interstitial positions, thereby modifying the crystal structure and increasing the adsorption sites. Additionally, doping Co and N in HTO can create more oxygen vacancies to facilitate the ion diffusion process. Benefiting from the synergistic effect between heteroatoms modification and oxygen vacancies mediation, Co/N-HTO-LIS exhibits excellent performance in terms of lithium extraction with a lithium adsorption capacity of 46.17 mg g−1 in simulated brine (lithium 1100 mg/L) at 20 °C. This value is significantly higher than that of cobalt-doped HTO (41.28 mg g−1) and undoped HTO (30.58 mg g−1). Furthermore, batch experiments demonstrate that Co/N-HTO-LIS also possesses good stability and selectivity. This work provides a guidance for rational design of titanium-based adsorbents towards lithium extraction from brine.