Evaluation of Acid Stability and Lithium Desorption Efficiency of MOF-based Lithium Adsorbent (MnO₂@Co/Zn ZIF)

The increasing global demand for lithium, predominantly driven by the rapid advancement of energy storage technologies such as lithium-ion batteries, necessitates the development of highly efficient and sustainable lithium recovery strategies from secondary resources. Metal–organic frameworks (MOFs), owing to their tunable porosity, chemical stability, and selective adsorption capabilities, represent a promising class of adsorbents for this purpose. This study systematically investigates the acid stability and lithium desorption efficiency of a novel MnO₂@Co/Zn zeolitic imidazolate framework (ZIF) under various acidic conditions. The MnO₂@Co/Zn ZIF composite was subjected to desorption experiments in equimolar solutions of nitric acid (HNO₃), hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and acetic acid (CH₃COOH) under controlled stirring for one hour. The extent of framework degradation and composite stability was quantitatively assessed by measuring the concentrations of leached Co²⁺ and Zn²⁺ ions from the MOF structure, as well as Mn ions originating from the MnO₂ component (primarily Mn⁴⁺ in MnO₂, which may be partially reduced to Mn³⁺ or Mn²⁺ in acidic conditions), using inductively coupled plasma mass spectrometry (ICP-MS). This approach enabled precise evaluation of the chemical robustness of both the MOF framework and the MnO₂ additive during the lithium desorption process. Results demonstrate that HNO₃ induces the highest degree of metal ion leaching, attributed to its potent oxidizing nature and elevated proton activity, which compromise the structural integrity of the composite. HCl also promotes significant dissolution through metal-chloride complex formation, thereby exacerbating framework degradation. In contrast, H₂SO₄ induces moderate ion release, suggesting a balanced interaction that preserves structural stability while facilitating lithium desorption. Notably, CH₃COOH exhibited minimal metal leaching, indicating superior acid stability; however, its weak acidity and limited complexation capability resulted in suboptimal lithium desorption efficiency. Sulfuric acid emerges as the most effective desorption medium, achieving a synergistic balance between efficient lithium release and preservation of composite structural integrity. The findings underscore the critical importance of acid selection in optimizing desorption protocols to enhance both the recovery efficiency and the reusability of MOF-based adsorbents. This work provides valuable insights into the design of robust, high-performance composite adsorbents for sustainable lithium recovery and resource recycling technologies.

کلیدواژه ها:

Lithium ، Adsorption ، MOFs ، ZIFs