Preparation of High-Selectivity Li+ Adsorbents Based on Bauxite via Liquid-Phase Alkaline Thermal Activation

Bauxite, as the main aluminium-bearing mineral in China, is a crucial resource for the industrial production of aluminium and aluminium-related products. In this study, bauxite-based aluminium composite Li⁺ adsorbents were prepared using a liquid-phase alkaline thermal activation—acid in situ method. The effects of various factors on Li⁺ adsorption from brine were investigated through single-factor experiments. Multiple techniques, such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method, Fourier transform infrared spectroscopy (FT-IR), and x-ray photoelectron spectroscopy (XPS), were employed to characterise and analyse the microstructure, pore size distribution, chemical element distribution, and mineral structure of the adsorbents. In addition, the changes in bauxite structure and properties before and after functionalization were investigated. Results indicate that the adsorption capacity of LATA-AIS-LDH-BX adsorbent prepared by the acid in situ method reached 1.15 mg/g at pH = 7; the adsorption capacity of LATA-Al-LDH-BX adsorbent prepared by the aluminium salt conversion method reached 2.16 mg/g. The adsorption behaviour of both adsorbents followed the pseudo-second-order kinetic model and the Langmuir model. In the presence of interfering ions (Na⁺, K⁺, SO₂ ⁴⁺, Mg²⁺), the composite adsorbents showcased strong selective adsorption capacity for Li⁺. After five cycles of adsorption–desorption, the adsorption rates decreased by 12.19% and 11.48%, respectively, demonstrating good recycling stability. Furthermore, the Li⁺ adsorption capacities in salt lake brine reached 0.82 mg/g and 1.48 mg/g, indicating promising potential for industrial application.