Composition and element mobilization in pyrometallurgical slags from the Orzeł Biały smelting plant in the Bytom–Piekary Śląskie area, Poland

Abstract

Wastes accumulated at Piekary Śląskie, Poland, are the result of 150 years of continuous working of the Orzeł Biały smelting plant. Slags are composed of: oxides (spinel, hematite, zincite); silicates and aluminosilicates (olivine, monticellite–kirschteinite, titanite, merwinite, pyroxene, melilite, feldspars: plagioclases and plumbean K-feldspar, nepheline, kalsilite, leucite); sulfides (pyrrhotite, rudashevskyite, galena), metallic phases (pure iron and iron–arsenic mixture) and secondary phases (gypsum, rapidcreekite, apatite). Interstices between the crystalline phases are filled by glass, concentrating toxic and potentially harmful elements, e.g. up to 53.22 wt.% PbO. The sequence of crystallization of primary phases depended on the local variability of oxygen fugacity and degree of calcination, while the texture type resulted from the cooling time and partial pressure of volatiles. Suggested crystallization temperatures are in the range of 1200–1500°C. Bulk chemical analyses show that the slags are composed mainly of SiO2, Al2O3,Fe2O3, MgO and CaO. Among the potentially harmful elements, Zn is the most common, reaching up to 5.93 wt.%, Pb is present in concentrations up to 3.9 wt.% and As in weathered samples exceeds 1 wt.%. Leaching tests of these elements confirms As mobility as Zn and Pb are preferably leached from fresh slags, while As is present in greater amounts in leachate from weathered slag samples. The documented amounts of As, Zn, Pb and their mobility in slags produce an environmental risk, as this material is currently used widely for commercial purposes.

Mineralogy and origin of coarse-grained segregations in the pyrometallurgical Zn-Pb slags from Katowice-Wełnowiec (Poland)

“…Similar sequence of crystallization commonly occurs in pyrometallurgical slags regardless of Zn smelting technology (e.g. Ettler et al 2001;Puziewicz et al 2007;Warchulski et al 2015).…”

“…Chemical zoning observed in major phases of pyrometallurgical slags (spinels, olivine, pyroxene) is indicative of the fractional crystallization (e.g. Ettler et al 2001;Puziewicz et al 2007;Kucha et al 1996;Warchulski et al 2015). The sector zoning in pyroxene crystals common in the miarolitic segregations is indicative of the disequilibrium growth, with different crystal faces attracting different cations as a result of different proportion of bonds at the crystal -melt interface (Dowty 1976) or can be an effect of different diffusion rates for the specific components in relation to crystal growth rate (Watson and Liang 1995).…”

Understanding Heterogeneity of a Slag-Derived Weathered Material: The Role of Automated SEM-EDS Analyses

“…Slag heaps are potential sites of extensive weathering and metal release [1,5,10,19] and they are usually comprised of numerous phases with various grain sizes, compositions, weathering potentials and composed of high abundances of potentially toxic elements [5]. Even in a single heap, phase composition of slags [21,27] and proportions of primary and secondary phases [19,20] may vary strongly. Additionally, the relationship between primary and secondary phases may be disturbed by hydrothermal crystallization from hot fluids remaining in the slag heap shortly after the slag deposition [22,28].…”

Mineralogical and Chemical Characteristics of Slags from the Pyrometallurgical Extraction of Zinc and Lead

“…The slags contain, in chemical terms, mainly FeO, CuO and SO 3 , PbO, in smaller contents SiO O 5 . The mineralogical and chemical composition indicate that slags may be a potential source of metals recovery and pyrometallurgical processing of these wastes seems to be highly rational.These slags were also found to contain carbonates (cerussite PbCO 3 , smithsonite ZnCO 3 , hydrozincite Zn 5 (CO 3 ) 2 (OH) 6 ), metal alloys (Pb, Zn, Cu, Fe) and secondary minerals (e.g., gypsum CaSO 4 ·2H 2 O, rapidcreekite Ca 2 (SO 4 )(CO 3 )·4H 2 O, apatite Ca 5 (PO 4 ) 3 (F,Cl,OH), ktenasite ZnCu 4 (SO 4 ) 2 (OH) 6 ·6H 2 O and posnjakite Cu 4 [(OH) 6 |SO 4 ]·H 2 O), which crystallize after the slag is deposited in a landfill [4][5][6][7][8][9][10][11].Due to the high concentrations of elements, including toxic metals, the refining slags deposited in a landfill may pose a potential threat to the natural environment on the one hand and a source for their extraction on the other [11][12][13][14][15][16].The basis for determining the potential negative environmental impact of the slags and for indicating the optimal technology for their processing is a detailed analysis of their chemical and phase composition. And such analysis was the aim of the study the results of which are presented in this paper.…”

“…Due to the high concentrations of elements, including toxic metals, the refining slags deposited in a landfill may pose a potential threat to the natural environment on the one hand and a source for their extraction on the other [11][12][13][14][15][16].…”