Shihao Ding, Wenqian Xing, Ling Chen, Linhui Fu, Qianqian Li, Mengting Qin, Jiang Gong, Jinping Qu, Ran Niu*

Photothermal-driven micromotor for enhanced lithium extraction from salt-lake brines

Chemical Engineering Journal (2025) Accept.

Lithium has emerged as a critical strategic resource for renewable energy applications. However, conventional adsorption-based lithium extraction technologies are often hindered by slow kinetics and limited adsorption capacity. In this study, we developed near-infrared (NIR) and solar light-driven micromotors for efficient lithium extraction from salt-lake brines. These micromotors were fabricated via inverse emulsion crosslinking, incorporating poly(vinyl alcohol) (PVA), ion sieve (HMn?O?), and Fe?O? nanoparticles. The photothermal conversion capability and thermally induced selfpropulsion of these micromotors overcome the diffusion limitations of traditional static adsorbents, significantly enhancing lithium adsorption kinetics and capacity. Under solar irradiation of 0.1 W cm?2, the micromotors achieved a lithium uptake capacity of 34.5 ± 1.1 mg g?1 in a 50 ppm Li? solution within 1.5 hours, which is 1.23 times higher than the adsorption capacity obtained in the dark after 5 hours. Additionally, the integration of superparamagnetic Fe?O? nanoparticles enables facile magnetic recovery and recyclability. When applied to a high-salinity simulated brine (20 g L?1) with an initial Mg2?/Li? ratio of 160, the micromotors effectively reduced the ratio to 0.7, demonstrating exceptional selectivity. This self-propelled micromotor system presents a promising strategy for designing intelligent materials for sustainable lithium resource recovery.