Synthesis of Gold Nanoparticles from Gold Coatings Recovered from E-Waste Processors.

This work presents the synthesis of Au nanoparticles from gold coatings recovered from processor pins with minimal waste generation. The process consisted of four main steps: (1) physical recovery of pins, (2) recovery of gold coatings by acid digestion, (3) synthesis of HAuCl4 under mild conditions and, (4) synthesis of Au nanoparticles by the Turkevich method. The small dimensions of Au coatings allowed the synthesis of HAuCl4 with lower amounts of HClconc and HNO3conc than those used with aqua regia. This method has significant advantages, such as lower NO2(g) emission, easy post-treatment and purification, low synthesis cost and high yields. Gold nanoparticles synthesized from HAuCl4 were characterized by transmission electron microscopy (TEM) and UV-Vis spectroscopy. Size distribution analysis showed particles 14.23 nm in length and 12.05 nm in width, while absorption spectra showed a surface plasmon located at 523 nm; these characteristics were very similar to those observed with Au nanoparticles obtained with Aldrich's reagent. It is suggested that recycling procedures can be improved by taking into account the size and shape of the metals to be recovered, thus introducing a new field of research known as hydronanometallurgy.

Hydrogen Oxidation and Oxygen Reduction Reactions on an OsRu-Based Electrocatalyst Synthesized by Microwave Irradiation.

This work presents an OsRu-based electrocatalyst synthesis, by a rapid and efficient method through microwave irradiation. The outstanding electrocatalyst shows a dual catalytic activity, demonstrating both: hydrogen oxidation and oxygen reduction reactions. The material is structural and morphologically characterized by FT-IR, X-ray diffraction, EDS, and SEM, indicating nanoparticulated Os and Ru metallic phases with a crystallite size of ∼6 nm, calculated by the Scherrer equation. The metal nanoparticles are apparently deposited on a carbonaceous sponge-like morphology structure. Its electrochemical characterization is performed in 0.5 M H2SO4 by the rotating disk electrode technique, employing cyclic and linear sweep voltammetry. Two different ink treatments have been studied to improve the obtained polarization curves. The material is also tested in the presence of methanol for the oxygen reduction reaction, showing an important resistance to this contaminant, making it viable for its use in direct methanol fuel cells (DMFCs) as a cathode and in polymer electrolyte fuel cells (PEMFCs) as an anode as much as a cathode.