Zdenek Johan

Primary and secondary phases in copper-cobalt smelting slags from the Copperbelt Province, Zambia

Abstract Pyrometallurgical slags from three Cu-Co smelters (Nkana, Mufulira, Chambishi) in the Copperbelt Province, Zambia, were studied from mineralogical and chemical points of view. The slags were enriched in metals and metalloids, mainly Cu (up to 35 wt.%), Co (up to 2.4 wt.%) and As (up to 3650 ppm). The following primary phases were observed in slags: Ca-Fe silicates (clinopyroxene, olivine) and leucite, oxides (spinel-series phases), ubiquitous silicate glass and sulphide/metallic droplets of various sizes. The presence of glass and skeletal/dendritic crystal shapes indicated rapid cooling of the slag melt. Copper and cobalt were found in low concentrations in the majority of silicates (olivine, clinopyroxene) and oxides, substituting for Fe in their structures (up to 7.15 wt.% CoO in olivine, 4.11 wt.% CuO in spinel). Similarly, up to 0.91 wt.% CoO and 6.90 wt.% CuO were observed in the interstitial glass. Nevertheless, the main carriers of these metals in the slags studied were Cu sulphides (digenite, chalcocite, bornite, chalcopyrite), Co-Fe sulphides (cobaltpentlandite), Co-bearing intermetallic phases ((Fe,Co)2As) and alloys. Weathering features corresponding to the presence of secondary metal-bearing phases, such as malachite (Cu2(CO3)(OH)2), brochantite (Cu4SO4(OH)6) and sphaerocobaltite (CoCO3), were observed on the slag surfaces. They indicate that the slags studied are reactive on contact with water/atmosphere and that their environmental stability and release of potentially harmful metals and metalloids must be evaluated further.

Zinc partitioning between glass and silicate phases in historical and modern lead–zinc metallurgical slags from the Příbram district, Czech Republic

Metallurgical slags of different ages resulting from Pb-metallurgy in the Přibram district (Czech Republic) have been studied. The chemical analysis (EPMA) of melilite, clinopyroxene, olivine and glassy matrix showed the following ZnO concentrations (in wt. %): 3.20–11.93 (melilite), 1.56 (clinopyroxene), 1.29–7.82 (olivine), 1.58–6.58 (glass). The Zn partition coefficient D = Cs / Cl between crystallized phases and coexisting glass was calculated. The values obtained are: 1.96–2.16 (melilite), 0.41 (clinopyroxene) and 0.79–1.19 (olivine). The distribution of zinc between the crystalline phases and glass depends on the phase assemblage, which reflects the blast furnace charge and temperature, as well as the cooling conditions of slags.

Composition and fate of mine- and smelter-derived particles in soils of humid subtropical and hot semi-arid areas.

We studied the heavy mineral fraction, separated from mining- and smelter-affected topsoils, from both a humid subtropical area (Mufulira, Zambian Copperbelt) and a hot semi-arid area (Tsumeb, Namibia). High concentrations of metal(loid)s were detected in the studied soils: up to 1450mgAskg(-1), 8980mgCukg(-1), 4640mgPbkg(-1), 2620mgZnkg(-1). A combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM/EDS), and electron probe microanalysis (EPMA) helped to identify the phases forming individual metal(loid)-bearing particles. Whereas spherical particles originate from the smelting and flue gas cleaning processes, angular particles have either geogenic origins or they are windblown from the mining operations and mine waste disposal sites. Sulphides from ores and mine tailings often exhibit weathering rims in contrast to smelter-derived high-temperature sulphides (chalcocite [Cu2S], digenite [Cu9S5], covellite [CuS], non-stoichiometric quenched Cu-Fe-S phases). Soils from humid subtropical areas exhibit higher available concentrations of metal(loids), and higher frequencies of weathering features (especially for copper-bearing oxides such as delafossite [Cu(1+)Fe(3+)O2]) are observed. In contrast, metal(loid)s are efficiently retained in semi-arid soils, where a high proportion of non-weathered smelter slag particles and low-solubility Ca-Cu-Pb arsenates occur. Our results indicate that compared to semi-arid areas (where inorganic contaminants were rather immobile in soils despite their high concentrations) a higher potential risk exists for agriculture in mine- and smelter-affected humid subtropical areas (where metal(loid) contaminants can be highly available for the uptake by crops).

Reliability of chemical microanalyses for solid waste materials

The investigation of solid speciation of metals and metalloids is required for accurate assessment of the hazardous properties of solid waste materials from high-temperature technologies (slag, bottom ash, fly ash, air-pollution-control residues). This paper deals with the problem of reliability of microanalyses using a combination of electron microprobe analysis (EPMA) and scanning electron microscopy (SEM) only. These methods do not permit to detect nanophases in host-crystals and lead to erroneous interpretation of analytical results, considering the elements of nanophases as belonging to the crystal structure of the main phase. More detailed analysis using transmission electron microscopy (TEM) on foils prepared by focused ion beam (FIB) can be used to solve this analytical problem. In this study, lamellar aggregates of potassium-rich clinopyroxenes were detected in copper smelting slags by a combination of SEM and EPMA. However, FIB-TEM indicated the presence of leucite inclusions (tens to hundreds nm in size) within the clinopyroxene lamellae. Based on examples from smelting slags and other solid waste materials, recommendations for standard SEM and EPMA applications and the need for methods with higher resolution for mineralogical investigation of waste materials are discussed.

Les micas de la coupole granitique de Cı́novec (Zinnwald), République tchèque : un nouvel aperçu sur la métallogenèse de l'étain et du tungstène

Abstract The zonation of Cinovec granite cupola results from a transformation protolithionite → zinnwaldite due to the interaction with a F-rich fluid. This is a major metallogenic process leading to the release of Ti, Sn, Nb, Ta and W from the protolithionite crystal structure and to the transfer of these elements into the F-rich fluid phase. By analogy with REE-oxyfluorides discovered at Cinovec, the transportation of Sn as SnF4, whose hydrolysis leads to SnO2 (cassiterite) and of W as WF6, which reacts with H2O yielding H2WO4, is suggested. Accessory mineral phases included in protolithionite (zircon, thorite, xenotime) are strongly hydrated and fluorinated. Thorite, monazite, xenotime and rutile become unstable in the zinnwaldite granite.