The performance and mechanism of recovering lithium on H4Ti5O12 adsorbents influenced by (110) and (111) facets exposed

The adsorption behavior and mechanism of H4Ti5O12 (110) and H4Ti5O12 (111) were systematically investigated by experiments and theory calculations, which indicates H4Ti5O12 (111) has more potential on Li+ recovery. [Display omitted] •The H4Ti5O12 with (110) and (111) facets exposed were synthesized.•The adsorption uptake of H4Ti5O12 (111) is higher than that by H4Ti5O12 (110).•The adsorption of [Li(H2O)4]+ on H4Ti5O12 (111) is more stable than (110).•Li+ is easier diffused from (111) facet into Li4Ti5O12 crystal than (110) facet. 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 (110) and (111) facets were investigated by using experimental and computational methods. The maximum Li+ uptake values on H4Ti5O12 (110) and H4Ti5O12 (111) 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 (111) still remains 88.9% of the original’s, which is higher than H4Ti5O12 (110) (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 (111) facet exposed. Firstly, H4Ti5O12 (111) 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 (111) is easier to than Li4Ti5O12 (110) through 8a-16c-8a-16c sites. At last, [Li(H2O)4]+ can form the stable complexes and its adsorption energies on (111) are higher than on (110) 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.