Lithium recovery in a batch adsorption study: Synthesis, characterization, optimization, regeneration, kinetics, and isotherm studies

Abstract

Lithium (Li)recovery is significant due to an increasing need for Li in diverse applications, particularly in the energy storage domain. In this study, a synthesized adsorbent was developed and utilized to efficiently recover Li. Therefore, this research aims to assess the effectiveness of using the synthesized adsorbent LiHMO to recover Li from the aqueous solution. The surface area and characteristics of the synthesized adsorbent were subjected to analysis utilizing different methods and techniques, including scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Fourier-transform infrared spectroscopy (FTIR). The findings indicated that the synthesized adsorbent demonstrated exceptional adsorption capabilities for Li recovery. Characterization analysis revealed a well-defined porous structure and functional groups on the adsorbent's surface, facilitating adsorption. The surface area of the adsorbent was determined to be 25.54 m²/g, providing a substantial active surface for adsorption processes. The Box-Behnken response surface method (RSM) was utilized to optimize the recovery process for key factors such as pH, adsorbent dose, time, and concentration. The critical operating parameters identified included a pH of 4, initial concentration of 900 mg/L, contact time of 460 min, and adsorbent dosage of 1300 mg/L. The obtained data were analyzed using a quadratic model, yielding an R² value of 0.9538, indicating that the adsorbent is effective in Li adsorption. The optimal conditions for maximizing Li recovery were found to be 95 % and 89 % for maximum and minimum recovery, respectively. The amount of adsorbate adsorbed (q_e) was determined to be 6.2 mg g^-1. Various kinetic models and isotherms were utilized to conform to these parameters. The Freundlich isotherm and the intraparticle diffusion model showed strong fits, as evidenced by their R² results of 0.9876 and 0.9862, respectively. The kinetic study suggested that the intraparticle-diffusion model best explained the adsorption process, indicating chemisorption as the rate-limiting step. The equilibrium data fitted well with the Freundlich isotherm, suggesting multilayer adsorption with heterogeneous surface energies. Furthermore, the study assessed the adsorbent's regeneration potential, finding that the first cycle of regeneration achieved 91.9 % efficiency, while the fifth cycle maintained a high efficiency of 89.7 %, indicating good reusability of the adsorbent. The study's findings showcase the efficiency of the synthesized adsorbent LiHMO in Li recovery from aqueous solutions, offering valuable information about the best conditions for the adsorption process. As a result of its superior sorption capacity and high recovery of adsorbed Li, the LiHMO adsorbent was selected as the optimal choice for Li recovery from aqueous solutions.