Lithium Extraction from an Aqueous Medium through In Situ Synthesis of Aluminum Hydroxide: A Comprehensive Study on Adsorption and Desorption Processes, Kinetics, Isotherm Models, and Thermodynamic Parameters

The increasing demand for lithium across various industries emphasizes the importance of lithium extraction methods. Aluminum hydroxide (Al(OH)3) has emerged as a promising option for extracting lithium from brines due to its selectivity, capacity, and straightforward synthesis process. This study introduces a novel Al(OH)3 synthesis method using water decomposition by activated aluminum powders. In this regard, the influences of several key parameters, including the operating temperature, reaction time, Al-to-Li molar ratio in the solution, initial lithium concentration, and presence of coexisting ions (Mg2+, Ca2+, and Na+) in the lithium solution on the efficiency of lithium removal were investigated carefully. Under appropriate conditions (using Al-based materials composed of Al, CaO, and NaCl), with a reaction time of 48 h, a temperature of 40 °C, an Al-to-Li molar ratio of 4:1, and initial lithium and sodium concentrations of 1 and 20 g/L, respectively, the adsorption efficiency reaches an impressive 99.7%. Notably, the presence of sodium enhances the lithium removal efficiency, with an increase in sodium concentration from 1 to 5 g/L resulting in an improvement from 95.2 to 98.7%. Conversely, the impact of calcium on lithium adsorption is minimal, as an increase in its concentration from 1.0 to 20 g/L only slightly decreases the efficiency from 98.95 to 96.57%. In contrast, the presence of magnesium significantly reduces adsorption efficiency to 24.6% at 4 g/L. The study also investigated the desorption rate using three different leaching solutions (HCl, H2SO4, and H3PO4) and found that chloric acid exhibits the highest desorption rate at 0.20 N (59.27%). Results were analyzed using various isotherm and kinetic models, with the most suitable models identified as the Dubinin–Radushkevich isotherm and the pseudo-second-order kinetic model. Thermodynamic analysis revealed that the reaction is exothermic, leading to increased randomness, and the adsorption process is primarily physical in nature.