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

Abstract

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.