Selective Lithium Uptake and Competition with Cobalt into Biobased Aerogels Loaded with Hydrogen–Manganese Oxide

Lithium ion (Li+) uptake was investigated in chitosan–pectin–lactic acid aerogel sponges containing hydrogen–manganese oxide (HMO) or lithium–manganese oxide (LMO) as fillers, for concentrations ranging from 1 to 250 ppm. The aerogels provided a spongy, biocompatible structure with fillers fully incorporated, as confirmed by PXRD, SEM, DSC, TGA, and X-ray tomography analyses. The Li+ adsorption data were well described by the Langmuir equilibrium model. Sponges loaded with 20% wt HMO achieved removal efficiencies (R%) up to 80% at 10 ppm Li+, exhibiting high selectivity over Co2+ (e.g., R%(Li)/R%(Co) = 5.6 for 30 ppm Li+ and 10 ppm of Co2+). In contrast, LMO incorporation inhibited Li+ uptake. Moreover, Li+ desorption using lactic acid at pH 2.1 enabled effective sponge regeneration, with first-cycle delithiation exceeding 90% and second-cycle uptake remaining above 75% at low concentrations. These results demonstrate that HMO-based aerogels combine efficient Li+ removal, selectivity against divalent cations, and practical reusability under mild conditions. Since the aerogels are formed by biopolymer matrices derived from renewable biomass, containing environmentally friendly fillers, and exhibiting reusability, the sponges constitute systems of high environmental relevance for their application in the separation and recuperation of Li+ from divalent metals in lithium battery recycling processes within a circular economy scheme.