Abstract The total number of electronic voting machines produced in Brazil was 1,489,115 units between the years of 1996 and 2023 (14,598.99985 tons). The objective of this study was to conduct a detailed characterization of the physicochemical composition of obsolete electronic voting machines (EVM), focusing on determining the Gold (Au) and Silver (Ag) content in Printed Circuit Boards (PCB). The methodology involved both physical and chemical treatments. The physical treatment included a comminution stage using knife mills, followed by particle size classification through manual agitation using sieves with openings of 16, 32, and 60 mesh. In the chemical treatment, metal detection was carried out using a variety of analytical techniques, including Sensor-Based Sorting (SBS), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Fluorescence (EDXRF), X-ray Fluorescence (XRF), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Four electronic voting machine (EVM) printed circuit boards (PCBs) were used in this study, with Au contents ranging from 0.02646 to 0.0768 g and Ag contents ranging from 0.087 to 0.54 g. It was observed that, in the fraction without granulometric classification, both higher and lower detections were obtained compared to the fractions subjected to the classification stage. The PCBs were similar when compared to other circuit boards, making them suitable for commercialization and logistics with other electronic equipment. Between 1996 and 2023, the economic potential derived from the characterization data for Au and Ag in the four granulometric fractions was USD 29,352,755.25 and USD 2,126,456.22, respectively, for PCBs without granulometric classification.
Piovezan et al. (Thu,) studied this question.