Ionic-Liquid-Tethered Cationic MOF for Adsorption of Gold from Aqueous Matrices and Electronic Waste

The rapid growth of the electronics industries intensifies the demand for precious rare-earth metals in manufacturing. Gold is one of the extensively consumed metals used in modern chipsets. Hence, the growing demand for gold necessitates the development of sustainable technology to recycle and recover gold from electronic waste (e-waste). Herein, a highly porous, ionic liquid-grafted cationic Zr(IV) metal–organic framework (MOF), named 1′@IL, was strategically synthesized to assess the aqueous-phase extraction of gold. Material 1′@IL exhibited an unprecedented gold adsorption capacity of 1208.5 mg/g within 30 s at neutral pH. Additionally, 1′@IL features extraction of the ultratrace concentration of gold ions from different environmental water matrices (river water, lake water, and seawater) and diverse pH media (pH 2–9). Besides, the long-term physicochemical robustness of 1′@IL assists in the regeneration of the adsorbate and recycling up to six cycles without losing its adsorption capacity, crystallinity, and functionality. The pronounced selectivity and broad operational scope of 1′@IL facilitate effective gold recovery, even from gold-rich electronic waste. In addition, a 1′@IL@PVDF-2 (PVDF = polyvinylidene difluoride) composite membrane was successfully synthesized through the homogeneous distribution of 1′@IL MOF powder over the PVDF matrix. The prepared 1′@IL@PVDF-2 composite membrane demonstrated successful recovery of gold from the aqueous phase with a significantly high adsorption capacity of 850.9 mg/g. Furthermore, electrostatic interaction-based adsorption of gold was precisely elucidated through experimental and theoretical studies. This study provides a clear insight into the potential applications of MOF-based adsorbents for the efficient and targeted extraction of valuable rare-earth elements.