First insights into mineralogy and weathering of the slags produced by smelting lateritic Ni ore at Vozarci, North Macedonia

Autor(en)

Tamara Đorđević, Peter Nagl, Christian Leopold Lengauer, Uwe Kolitsch, Goran Tasev, Todor Serafimovski, Ivan Boev, Blažo Boev

Abstrakt

The laterite Ni ore smelting operations at Vozarci, North Macedonia,

which produces ferronickel since 1982, have produced large amounts of

smelting wastes dumped at the smelter. In May 2022 we have sampled three

different types of slags occurring in these slag dumps. Slag 1 was

produced using predominantly ore imported from Indonesia, slag 2 was

formed using the ore from the nearby Ržanovo mine and slag 3 was

produced using predominantly ore imported from the Ivory Coast. X-ray

fluorescence (XRF) spectroscopy analyses showed that slags 1 and 3

contain between 43–47 wt.% SiO₂ and slag 2 35 wt.% SiO₂. Relative to slags 1 and 3, slag 2 is enriched in iron (40 wt.% Fe₂O₃). Furthermore, slag 2 is characterized by a large Cr content (ca. 17400 ppm of Cr₂O₃).

A combination of powder X-ray diffraction, Raman spectroscopy and

SEM-EDS analyses (of polished aliquots) showed that the slags consist of

silicate glass, synthetic equivalents of orthopyroxenes (enstatite),

clinopyroxenes (clinopyroxene, diopside, pigeonite, augite), olivines

(forsterite, fayalite) and subordinate spinel-group phases (chromite,

magnesiochromite, magnetite, trevorite), sulphides (pyrrhotite and

FeS-NiS phases) and intermetallic compounds (metallic Fe with up to 10

at.% Ni and remnants of ferronickel). All three slags contain

significant amounts of the following potentially toxic elements: Co

(20-87 ppm), Cr (9600-17400 ppm), Ni (500-730 ppm) and Zn (150-380 ppm).

The phase assemblages and textures in the Vozarci slags are similar to

those in other pyrometallurgical slags produced during reworking of

silicate and sulphide ores. Although the slags 1 and 2 have been exposed

to atmospheric conditions for about 40 years, those occurring in the

dumps are not much affected by weathering. At present, we have

identified the following alteration products: (i) abundant iron

oxy-hydroxides (including lepidocrocite) (slag 1), (ii) minor

nesquehonite, MgCO₃·3H₂O (slag 2) and (iii) syngenite, K₂Ca(SO₄)₂·H₂O (slag 1). Since slag 3 is newly deposited slag, it is not weathered at all.

Organisation(en)

Institut für Mineralogie und Kristallographie, Department für Lithosphärenforschung

Externe Organisation(en)

Goce Delčev University of Štip

DOI

https://doi.org/10.5194/egusphere-egu23-15985

Publikationsdatum

2023

ÖFOS 2012

105116 Mineralogie, 105105 Geochemie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/183742e8-8d54-487b-a57a-0cee0a883259