Direct lithium extraction for different brine compositions: identifying and eliminating potential barriers using aluminium oxide based sorbent materials

The increasing global demand for lithium, driven by the growth of electric mobility and renewable energy storage, has intensified interest in efficient and environmentally sustainable extraction technologies. Direct Lithium Extraction (DLE) processes using sorbent-based systems offer a promising alternative to evaporation ponds, particularly for brines with high impurity content. This thesis investigates the mechanical and structural stability of a lithium aluminum layered double hydroxide chloride (Li/Al-LDH-Cl) sorbent in contact with synthetic brines of varying composition. The work focuses on two main interference scenarios: sulfate-rich brines with different SO₄²⁻/Cl⁻ ratios and carbonate-containing brines with increasing concentrations of Li₂CO₃. The aim was to identify conditions leading to sorbent degradation and to evaluate the DLE performance under representative field-like conditions. A series of batch and continuous column tests were conducted to assess fines formation, lithium desorption and sorption behavior, and structural transformations. Sulfate-rich brines caused progressive fines generation and structural weakening, particularly at high SO₄²⁻/Cl⁻ ratios, as confirmed by PSD and XRD analysis. In carbonate-based campaigns, increasing CO₃²⁻ concentrations caused distinct mechanical degradation in high-pH conditions. A representative carbonate-type brine was further tested in a 10-cycle column campaign, showing stable DLE performance, while XRD analysis revealed partial loss of crystallinity under repeated cycling. The findings demonstrate that sorbent–brine compatibility depends strongly on ionic composition and pH. This work provides experimental evidence to support brine-specific DLE strategies and contributes to process design by identifying degradation mechanisms under realistic operational scenarios.