An Eco-Friendly Approach for Gallium Recovery from Aqueous Solutions Using Immobilized Siderophores

Critical metals like gallium play essential roles in various high-tech applications, from electronics to renewable energy systems. However, limited natural availability and complex extraction processes create significant challenges. Conventional recycling methods for gallium often suffer from low selectivity, high costs, and environmental drawbacks, underscoring the need for more sustainable recovery techniques. This study presents a novel method for gallium recovery from waste streams and leaching solutions using the microbial metabolite siderophore Desferrioxamine B (DFOB), immobilized in sodium alginate through a Ca²⁺ cross-linking method. By leveraging the unique metal-binding affinity of siderophores combined with the stability and ease of handling provided by alginate hydrogels, this approach aims to enhance metal recovery efficiency while minimizing environmental impacts. The immobilization conditions of DFOB in alginate were optimized by adjusting parameters such as alginate, siderophore, and Ca²⁺ concentrations, as well as immobilization time, which increased the loading efficiency from below 20% to over 80%. Under optimal conditions, the immobilized DFOB-alginate beads achieved over 98% recovery of gallium from 100 ppm Ga solutions within 24 h. Additionally, selectivity tests using synthetic solutions containing nickel, cobalt, and aluminum showed that the siderophore-alginate beads exhibited a high selectivity for gallium, particularly over the divalent ions of nickel and cobalt. This enhanced selectivity is attributed to the specific chelation structure of DFOB, where hydroxamate functional groups play a crucial role in gallium binding. Compared to alternative adsorbents, the immobilized siderophores in alginate hydrogels demonstrated superior selectivity and higher adsorption capacity for gallium, offering a sustainable and low-impact solution for its recovery. The findings of this study pave the way for utilizing siderophores in eco-friendly technologies for recovering various critical metals from leaching solutions and waste streams.