Printed Circuit Boards Leaching Followed by Synthesis of Gold Nanoparticle Clusters Using Plant Extracts

Abstract 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 PbSO 4 , 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