Selective lithium extraction employing lithium manganese oxide-loaded polymeric membranes at natural brine pH and room temperature

The current technology for lithium extraction from brines is recognized both for its techno-economic disadvantages and its environmental impacts. We have synthesized, characterized, and evaluated particles based on lithium manganese oxide towards selective lithium recovery from complex media. A solid-state synthesis and a hydrothermal method produced sub-micrometre sized particles that showed diameters of 253 nm and 154 nm, respectively, both with very low polydispersity. 23.7 mgLi/gHMO and 30.7 mgLi/gHMO adsorption capacity values were obtained with solid-state synthetic and hydrothermal oxides. The hydrothermally synthesized sub-micrometre sized particles were incorporated into polymeric membranes aiming at the development of a straightforward technological application. Membranes were prepared from polyacrylonitrile and polyethylene-glycol, and the affinity to lithium was once again evaluated. Membranes showed a high adsorption capacity for lithium (32.7 mgLi/gHMO) with almost identical kinetics and cyclability as the free particles in solution. An excellent selectivity for lithium was confirmed in experiments with a natural lithium-rich brine from the Lithium Triangle. All adsorption experiments were performed at neutral pH and room temperature. An undeniable advantage of membranes vs. sub-micrometre sized particles is that the former do not require centrifugation after successful adsorption/desorption. These three characteristics are fundamental in the perspective of technology scale-up to minimize operational costs.