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The disposal of solid waste containing toxic metals in the composition is a problem of environmental and human contamination. The amount of waste as printed circuit boards has been increasing year by year. New processes that aim at recycling and subsequent application implementing a circular economy of this waste have been gaining importance. This study proposes the printed circuit boards characterization for the copper recycling by acid leaching in two steps, green synthesis of copper nanoparticles using ascorbic acid (vitamin C), and later application of nanoparticles into surfactant degradation through the Fenton-like process. Acid leaching proved a possible methodology for recycling copper, obtaining over 90% recovery. The printed circuit boards show to be a copper secondary source with a weight percentage of about 26 and recovery of 97% in two leaching stages. The synthesis of CuNPs was inferred through UV–Vis with absorption peak in 585 nm and modification of the coloration over time of solutions to dark brown. The syntheses were performed at 70 °C, 80 °C, and 90 °C and in 0.17, 0.5, 0.83, 1, 2, and 3 h, and the stability of copper nanoparticles was verified in 168, 720, and 960 h after syntheses. Stable nanoparticles were produced with different diameters, and they were applied as a catalyst in the Fenton reaction to degrade an amine-based surfactant used in the mining industry. The total carbon degradation found was 57%. It was possible to observe that the recycling of printed circuit boards is strategic to obtain copper from a secondary source, and the synthesis of copper nanoparticles could be used as a product to applicate in the circular economy using the Fenton process.

The green chemical synthesis of copper nanoparticles (CuNPs) is an alternative which uses chemicals and processes that reduce or eliminate the use and generation of toxic substances, such as ascorbic acid, cyclodextrin, plant extracts, chitosan and gelatine. In this study, precursor solutions of copper sulfate pentahydrate and ascorbic acid were used. The synthesized CuNPs were characterized by UV-visible (UV-vis) absorption spectroscopy, scanning electron microscope coupled to an energy dispersive X-ray spectrometry (SEM-EDS) and X-ray diffraction (XRD). The presence of Cu oxide particles and Cu nanoparticles was inferred through UV-vis. In the images and compositions of the SEM-EDS, oxygen and Cu were found as well as particles of non-uniform size and morphology. The results showed that at pH 5, agglomerated CuNPs were found. XRD verification was performed on the particulate at pH 5 in which diffraction peaks were attributed to copper structure planes (with dimensions of 1042–3.34 nm) and other CuO and Cu2O diffraction peaks that overlapped with Cu phases.

Printed circuit boards represent a source of urban mining for the reuse of resources in a circular economy. The number of metals in these boards can vary according to the model, year of manufacture, and function, making these scraps a complex residue for the application of recovery routes. In the present study, the leaching process was evaluated as an alternative to the magnetic separation step of the current hydrometallurgical routes for the recovery of iron and copper in these waste in which recovery of the metals present was carried out. The first stage of the hydrometallurgical route was leaching in sulfuric acid, for the recovery of iron. Subsequently, the copper recovery study was carried out, through the second stage of acid leaching in an oxidizing medium. The third stage was carried out in a nitric medium for the solubilization of the remaining metals. After using the same solid/liquid ratio for the solubilization of the metals present in the two types of boards, it was found that for the board with the highest concentration of metals that this ratio should be changed for greater extraction results. The percentage of leaching for the motherboard samples increased (to about 98 wt%) together with the residue/acid ratio, and this showed that for each type of waste, according to its composition, the metal/acid ratio must be established for complete solubilization of the metals of interest. The recovery of this waste, depending on the type of scrap, can reach at least US$ 1,230,000.00 /t waste.

The amount of waste from electrical and electronic equipment has been growing every year. The printed circuit boards contained in this waste include metals that can be recovered through urban mining, adding value to this waste and minimizing environmental impacts with its incorrect disposal or treatment. In this work, memory boards obsolete with 0.053 wt.% Ag were used. The extraction of all metals studied (Ag, Al, Cu, Fe, Ni, Sn, and Zn) involved the evaluation of the Pourbaix and speciation diagrams to identify the pH and redox potential conditions, considering the possible species formed with leaching agents: sulfuric, nitric, and hydrochloric medium. After the definition of the leaching agent, the extraction routes by hydrometallurgical processing were proposed from the parameters of temperature, s/l ratio, and reaction time previously studied. Route A was composed of sequential stages (the first leaching in a sulfuric medium and the second in an oxidizing sulfuric medium) and obtained 100% of Ag recovery. Route B consisted only of leaching in an oxidizing sulfuric medium, obtained about 94% of the Ag recovery, and could not contribute to the subsequent purification steps (if necessary) of this solution, as all metals would also be in the solution. These two routes showed that Ag can only be recovered in an oxidizing sulfuric acid medium, according to the conditions studied. Ag recovered in the leach liquor of the second stage of Route A was purified by chemical precipitation with NaCl, and the AgCl was solubilized in an NH4OH solution. This solution was used to synthesize silver nanoparticles by the Turkevich method in 25 minutes. The spherical nanoparticles synthesized an average size distribution of 67 nm.

Electronic components, such as printed circuit boards (PCBs), have elements in their composition that present economic value like copper, silver, gold and nickel, besides the metals that are harmful to the environment and to health as lead, mercury and cadmium. Aiming at the recovery of metals for economic purposes and, thus, preventing their inadequate disposal in the environment, the present study presents a route of physical and chemical characterization used to determine the amount of metals present in the PCBs (motherboards) aiming the production of nanoparticles copper. For this, as PCBs were dismantled for later comminution in a knife mill with the opening phases of 9, 3 and 2 mm. Fire-fighting tests were performed for the determination of polymer weakness and digestion acid to determine the concentration of metals present. After characterization of the plates, it was possible to determine that 43% corresponds to the metallic fraction of which 21.5% were copper. After characterization of the boards, it was possible to determine that 43% corresponds to the metallic fraction of which 21.5% were copper.