Preparation and performance evaluation of a high‐efficiency green solid‐phase extraction sorbent functionalized with quaternary ammonium groups

Abstract Solvent extraction is commonly used for lithium recovery from salt lake brines; however, organic phase loss and high acid consumption during stripping severely limit its sustainable application. In this study, nanosized SiO 2 was synthesized via the Stöber method and functionalized with vinyl groups using vinyltriethoxysilane (VTES) and γ‐(methacryloyloxy)propyltrimethoxysilane (KH570). Subsequent surface‐initiated polymerization with 2‐methacryloyloxyethyl phosphorylcholine (MPC) afforded two polymer‐grafted inorganic–organic hybrid sorbents bearing P=O moieties and quaternary ammonium groups, denoted as SiO 2 –VTES–MPC and SiO 2 –KH570–MPC. The structure–property relationship of the two sorbents was systematically investigated. SiO 2 –KH570–MPC exhibited significantly enhanced lithium adsorption and Mg/Li selectivity compared with SiO 2 –VTES–MPC, which was attributed to the higher grafting efficiency and more accessible functional groups. At an MPC‐to‐KH570–SiO 2 mass ratio of 2, the maximum lithium adsorption capacity reached 4.4163 mg·L −1 , with an Mg/Li selectivity of 92.0114. After acid elution, the sorbent retained excellent separation performance, achieving a total separation factor of 448.1323. The prepared polymer‐functionalized solid‐phase extraction sorbent combines high selectivity, low acid demand, fast stripping kinetics, and good acid‐elution stability, demonstrating promising potential for sustainable lithium recovery and advanced separation applications.