Conventional versus Microwave-Assisted Roasting of Sulfidic Tailings: Mineralogical Transformation and Metal Leaching Behavior


Conventional versus Microwave-Assisted Roasting of Sulfidic Tailings: Mineralogical Transformation and Metal Leaching Behavior

Kamariah, N.; Kalebic, D.; Xanthopoulos, P.; Blannin, R.; Araujo, F.; Koelewijn, S.; Dehaen, W.; Binnemans, K.; Spooren, J.

Roasting is often required to convert sulfidic minerals into their sulfate and/or oxide
forms with the aim to increase the extractability of targeted metals. In this study, sulfidic
tailings of Neves Corvo Cu-Zn-Pb-mine (Portugal) underwent conventional roasting
(CR) and microwave-assisted roasting (MR) to compare the effect of both heating
technologies on the roasting behavior. Upon roasting in air, transformations of mineral
phases in the tailings were studied by different techniques using quantitative X-ray
diffraction, mineral liberation analysis, Raman spectroscopy and
thermogravimetry−differential scanning calorimetry coupled to mass spectrometry.
Also, the leaching behavior of elements from the roasted tailings was assessed in
water. It was shown that CR and MR induce different reaction pathways for mineral
transformations during roasting. While CR leads to indirect pyrite oxidation through
intermediate sulfate formation, direct pyrite oxidation to oxides is the main
transformation pathway during MR. This change in reaction pathway can be attributed
to the mineral-selective heating induced by microwaves, which in particular accelerates
the oxidation rate of pyrite. In agreement with the proposed roasting mechanism, the
leaching behavior in water showed that the CR tailings resulted in a higher extraction
of the studied metals (Cu, Zn, Pb, As and Fe) – since sulfate phases are more
abundant – compared to the MR tailings at the same roasting temperature. Overall, the
optimal leaching efficiency of the metals was reached after one hour roasting at
500−550 °C for both CR and MR

Keywords: Conventional roasting; Microwave roasting; Sulfidic tailings; Mineralogical transformation; Water

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Publ.-Id: 33645