Amir Nobahar

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.

The environmental contamination by plastics, microplastics, and related compounds is a major concern. While the detection and release of micro- and nanoparticles from these materials have been widely studied, the formation and release of molecules resulting from their degradation in the environment have been overlooked. This work presents a study of the products released from poly(ethylene terephthalate) (PET) irradiated as pure particles and adsorbed on silica and sand surfaces under different irradiation conditions. The role of oxygen was also evaluated. The products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The main released molecules can be accounted for by considering the cleavage of α- and β-bonds next to the ester moiety of the polymer chain. Volatile products such as benzene as well as monomer units of the polymer and related products were identified. In the presence of oxygen, acetic acid and products resulting from hydroxylation at the benzenic ring or at the ethyl moiety were detected. Adsorption on silica and sand has little effect on the photoproduct distributions. The irradiation at 360 nm leads to distributions similar to the ones observed at 257 nm, but the reaction rate is lower. The identified product ethylene terephthalate is a marker of PET plastics and particles and can therefore be used to evaluate the environmental contamination by this polymer material.

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