Selective recovery of trace Ga(III) using a regenerable gallic-acid-grafted bio-graphene

Selective recovery of trace gallium (Ga) from diverse low-concentration waste streams is vital for securing a sustainable supply of this critical raw material, which predominantly exists as a trace byproduct in complex industrial residues. Conventional separation methods often struggle with limited selectivity in multi-ion matrices-where high concentrations of Al³⁺, Fe³⁺, and Ca²⁺ hinder Ga capture-and face environmental challenges due to excessive organic solvent use. In this study, we developed a systematic approach by first upcycling corn stalks into a bio-graphene scaffold, which was subsequently functionalized with gallic acid (GA) through epoxidation and ring-opening grafting to obtain GA-EPI-OCS. The material was then rigorously evaluated for its low-level affinity, achieving ∼97% Ga adsorption at 20 mg·L^-1. Equilibrium and kinetic behaviors were systematically modeled, and the selectivity was further validated in multicomponent matrices mimicking complex wastes, where Ga distribution coefficients were 1-2 orders of magnitude higher than those of co-ions. To decode the underlying recovery mechanism, we integrated spectroscopic characterizations (FTIR/XPS) with multi-scale theoretical simulations (MD/DFT). The results resolve the mechanism into inner-sphere Ga-O chelation and coordination-induced electronic hybridization. This comprehensive study offers a practical and sustainable route for Ga recovery from acidic leachates via a low-solvent, regenerable process.