Scanning electron microscopy (SEM) was performed to examine the particle morphology and surface characteristics of the mining waste samples. The analyses were conducted at CUT, INOE and FEUP (Figure 5). The SEM images show that all samples exhibit similar granular morphology without distinct or characteristic structural features. The particles appear irregular in shape, with no specific morphological patterns observed among the different materials. Although SEM images may vary with the equipment used, consistent grain sizes were observed across the analyzed samples. Figure 5 – SEM images of PT1, PT2, PT3, and PT4. Energy-dispersive X-ray spectroscopy (EDS) was performed to determine the elemental composition of the samples at the microscale. The results shown in Figure 6 confirm the compositional trends identified by XRF analysis. PT1 is predominantly composed of Fe and S, consistent with the presence of pyrite. PT2 is dominated by Si and O, corresponding to quartz-rich phases. PT3 and PT4 are primarily composed of Ca, C and O, confirming the predominance of calcite. PT1 PT2
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