The Li(H2O)n dehydration behavior influences the Li+ ion adsorption on H4Ti5O12 with different facets exposed

In this study, octahedrons assembled nanospheres Li4Ti5O12 (LTO-OS) with dominant (111) facet and nanosheets assembled microspheres Li4Ti5O12 (LTO-NS) with dominant (01-1) facet precursors were synthesized. Then, these corresponding H4Ti5O12 adsorbents (HTO-OS and HTO-NS) were obtained via acid treatment and used to recover lithium from aqueous solutions. The systematic adsorption tests show that HTO-NS possesses higher adsorption uptake (35.5 mg/g) and faster adsorption rate (equilibrium time: <2 h) than HTO-OS (31.2 mg/g), owing to the role of different dehydration processes and exposed facets. With the help of DFT calculation analyses, the dehydration of Li(H2O)4+ on HTO (01-1) and (111) were partially dehydrated Li(H2O)+ and Li(H2O)2+ in the adsorption process, owing to crystal channel and surface atomic arrangement. In addition, the analysis of the adsorption mechanism indicates that the Li+ exist in the form of hydrated lithium ions in the initial adsorption solution, and the dehydration processes occur during Li(H2O)4+ move to the surface of the adsorbent, then an ion exchange reaction has happened between the dehydrated Li+ and H+. These results reveal the adsorbents with different facets exposed indeed influence the surface dehydration processes and Li+ adsorption behaviors, which are favorable to better understand the interfacial interactions between adsorbents and adsorbates.