This work investigates the potential of 70% ethanolic leaf extracts of Rubus idaeus L., Cistus ladanifer L. and Erica andevalensis in the metal separation from synthetic unimetallic solutions of different metals and a leachate obtained from the leaching of PCBs. Results from the experiments with unimetallic solutions revealed R. idaeus and E. andevalensis extracts induced separation of more than 95% of the initial Au(III), while C. ladanifer separated ~78% of this metal. Thereafter, application of three plant extracts to real Au bearing leachate obtained from PCBs leaching, revealed about 96, 95 and 90% Au recovery with R. idaeus, C. ladanifer and E. andevalensis extracts, respectively with 15–60% co-removal of Pb and less than 15% of other metals. The reduction of Au(III) ions into Au(0) nanoparticles by R. idaeus extract was confirmed by molecular UV–Visible, and FT-IR analysis showed the involvement of plant secondary metabolites in Au bio-reduction and bio-stabilization. Particles obtained from the application of R. idaeus extract to the leachate were initially analyzed with XRD and results confirmed the presence of Au(0) with contamination of PbSO₄, which was completely removed by washing with 1 M HCl. Thereafter, results from STEM-EDS analysis showed the presence of Au particles conjugated with organic material and other metals. Consequently, particles were subjected to another washing step with acetone. Afterwards, STEM-EDS showed pure Au microparticle clusters (~0.8 μm) with flower-shaped or apparently cubic morphologies, and HRSTEM showed the tiny nanoparticles (~20 nm), which form the clusters. Graphical Abstract

The separation and recovery of metal ions from industrial and municipal wastewaters and leachates is essential for environmental sustainability and resource conservation. Bio‐based polysaccharides, such as cellulose and chitin; proteins, such as keratin; and other biomacromolecules, such as lignin, offer a promising, sustainable alternative to conventional adsorbents due to their abundance, renewability, and inherent presence of metal‐binding functional groups. This review explores strategies to engineer these materials and enhance their metal interaction capabilities. These include chemical modifications (e.g., introduction of charged groups and metal‐specific ligands), physical treatments (e.g., particle size reduction and porosity control), and the development of composite materials and advanced architectures, such as activated carbons, membranes, fibers, and 3D‐printed structures. Despite their potential, challenges such as natural variability, lower durability compared to synthetic materials, and economic considerations remain. Through targeted research and development, biopolymers could become viable, eco‐friendly solutions for hydrometallurgical metal recovery processes, aligning with circular economy principles. This review provides a comprehensive, mechanism‐oriented synthesis that integrates material classes, functionalization strategies, and adsorption selectivity trends relevant to metal recovery under hydrometallurgical conditions and outlines future directions to overcome existing barriers.