The performance and mechanism of recovering lithium on H4Ti5O12 adsorbents influenced by (1 1 0) and (1 1 1) facets exposed

The improved adsorption capacities by increasing specific surface area methods are merely reached about 50% of H4Ti5O12’s theoretical adsorption capacity, and the adsorption behavior and mechanism of lithium on special facets of H4Ti5O12 remain unclear. In this study, a flower-shaped Li4Ti5O12 and an octahedral Li4Ti5O12 were prepared with the specific surface areas of 176.23 and 83.02 m2/g, and the corresponding adsorption behaviors of the obtained adsorbents exposed with (1 1 0) and (1 1 1) facets were investigated by using experimental and computational methods. The maximum Li+ uptake values on H4Ti5O12 (1 1 0) and H4Ti5O12 (1 1 1) are 26.85 mg/g and 33.56 mg/g at 45 °C in 24 mM LiCl solutions, respectively. The fifth reuse ability of H4Ti5O12 (1 1 1) still remains 88.9% of the original’s, which is higher than H4Ti5O12 (1 1 0) (76.3%). Although with lower specific surface area, the octahedral H4Ti5O12 have higher ions selectivity, greater adsorption capacity, and better reuse ability than flower-shaped H4Ti5O12, which may due to the special (1 1 1) facet exposed. Firstly, H4Ti5O12 (1 1 1) owned small hole sizes can inhibit other ions diffusing into H4Ti5O12 and improve the ion selectivity. Secondly, the immigration paths by the First-principles calculations revealed that the Li+ migrate onto the Li4Ti5O12 (1 1 1) is easier to than Li4Ti5O12 (1 1 0) through 8a-16c-8a-16c sites. At last, [Li(H2O)4]+ can form the stable complexes and its adsorption energies on (1 1 1) are higher than on (1 1 0) facets, which may lead to larger adsorption capacity and better reuse ability. This work will help to understand the [Li(H2O)4]+ adsorption behavior and mechanism on different crystal facets by experiments and computations.