Local Alkaline Microenvironment in Quaternized Hydrogel Enables Efficient Lithium Adsorption by H2TiO3 at pH 8
Shuhan Cui, Changxiang Yang, Jianmin Yang, Liang Shi, Shuyan Xiong, Lei Wang, Aidong TangAbstract
Lithium–ion sieve adsorption is considered one of the most promising technologies for lithium extraction from salt lake brines due to its high selectivity and environmental compatibility. However, the practical application of H2TiO3 (HTO) is limited by difficult solid–liquid separation and reliance on strongly alkaline conditions (pH ≥ 11). Herein, a quaternized hydrogel composite adsorbent (HTO/N–HEC) was fabricated by immobilizing SDS–HTO–TU particles within a hydrogel matrix. The grafted quaternary ammonium groups (−R4N+) pre–stored OH– to in situ neutralize H+ released during H+/Li+ exchange, creating a localized alkaline microenvironment. Under near–neutral conditions (pH = 8), HTO/N–HEC achieved a Li+ adsorption capacity of 34.8 mg·g–1 within 3 h, 222% higher than pristine SDS–HTO–TU powder. The composite also exhibited excellent cycling stability and Li+ selectivity, providing a feasible strategy for green lithium extraction without strong alkali dependence.