(171g) Magnetic Graphene Oxide Grafted with Temperature-Responsive Crown Ether Polymer Brushes As an Adsorbent for Lithium Recovery from Seawater

Lithium is used as a component for energy storage due to its high energy density. There is an anticipated supply shortage for lithium due to its soaring demand in mobile electronics and electric vehicles industries. Furthermore, the uneven global distribution of lithium reserves necessitates its recovery from alternative lithium secondary sources. Seawater is identified as a potential alternative lithium resource as it contains 2×10⁶ Mt Li⁺. However, the complex composition of seawater makes it difficult to recover Li⁺ due to its significantly lower concentration than Na⁺, K⁺, Mg²⁺, and Ca²⁺.

Herein, a multi-functional, thermo-responsive, Li⁺-selective, magnetic composite adsorbent was successfully synthesized. The magnetic support material (Fe₃O₄-rGO) was synthesized using the modified Hummers’ method, followed by the solvothermal process. SI-ATRP attachment sites were introduced by grafting the hydroxyl moieties via the diazonium surface modification method (OH@Fe₃O₄-rGO), followed by the esterification process to immobilize the SI-ATRP initiator 2-Bromo-2-methylpropionyl bromide (Br@Fe₃O₄-rGO). On the other hand, the Li⁺-selective CE (2-hydroxymethyl-12-Crown-4 Ether) was functionalized with an allyl-functional group (Allyl-12CE4) and was reacted with N-Isopropylacrylamide (NIPAM) via the SI-ATRP method and grafted on the Br@Fe₃O₄-rGO to produce the thermo-responsive adsorbent (12CE4-co-NIPAM)@Fe₃O₄-rGO.

The synthesized adsorbent was characterized and tested to determine its Li⁺ adsorption capacity and kinetics. The selectivity of (12CE4-co-NIPAM)@Fe₃O₄-rGO was tested using seawater as the feed solution. The recyclability experiment was done by temperature-swing adsorption-desorption cycles for the capture and release of Li⁺ without the utilization of acid. Thus, the integration of both magnetite and the polymer brush on the GO support material resulted in the Li⁺-selective, magnetic, and thermal-responsive (12CE4-co-NIPAM)@Fe₃O₄-rGO which is suitable for long-term Li⁺ adsorption-desorption application.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT (2020R1A2C1003560, 2021R1A2C2093746, and 2021R1H1A2008284), Basic Science Research Program through the Ministry of Education (2020R1A6A1A03038817).