Physical and chemical characteristics of slag produced during Pb refining and the environmental risk associated with the storage of slag

Abstract

Metallurgical waste originating from the Zn and Pb refining process presents varying chemical composition and physical properties and contains varying quantities of pollutants. In the study, both fresh and weathered samples of production slag from the final Pb refining process were used to determine its physical parameters and chemical composition as well as to perform an environmental risk assessment (RAC, mRAC) related to its storage. This paper focuses on determining parameters such as natural humidity (1.8%) and bulk density (1267 kg/m3) of the slag. Also, its toxicity was analysed using bio-tests, its pH was measured (11.92) and the content of sulphates (3.5 wt%), chlorides (0.3 wt%) and selected heavy metals (Cd, Cu, Fe, Mn, Zn, Pb) was determined. The Individual Contamination Factor was determined, yielding the following order of the hazard level: Pb > Cu > Zn > Cd > Fe > Mn. Based on the mobility of metals determined using the Mobility Factor, it was concluded that the hazard level followed the sequence Cd > Pb > Zn > Mn > Fe > Cu. The obtained water leaching results were compared to the values found in the legal regulations in force. Based on this comparison, it was established that the slag studied constitutes toxic waste containing considerable quantities of sulphides and chlorides. The material is also a considerable source of readily leaching elements (Cd, Zn and Pb), and thus any product created using the slag may become hazardous to the environment. Also, the waste studied must not be used in the form in which it is currently stored due to the leaching of particularly toxic elements (Cd and Pb) in water solutions with increasing acidity.

Changes in soil pH and mobility of heavy metals in contaminated soils

“…The other group, on the other hand, was formed on sandstone parent material, containing considerable amounts of SiO 2 , reaching up to even 88%-92% and presenting greater capacity to release H + and Al 3+ ions in weathering processes. Low pH usually denotes less favourable proportions of the gaseous and aqueous soil phases, which in turn translates into a rather unstable soil structure (Ahern et al, 1995;Bolan et al, 2014;Elsokkary & Lag, 1978;Kici nska, 2021).…”

The leaching of mercury and other elements from asbestos-cement sheets in various environmental conditions

“…the total content and studies on leaching are the subject of the work of various authors for other waste groups generated in the area of Poland (e.g. Bożym 2017Klojzy-Karczmarczyk 2020, 2021;Kicińska 2021;Kosa-Burda and Kicińska 2016;Król 2006;Król et al 2020;Szlugaj 2020). In comparison with other waste, the leachability of the analyzed metals and metalloids from asbestos-cement waste is definitely lower.…”

Geochemical and Mineralogical Characterisation of Historic Zn–Pb Mine Waste, Plombières, East Belgium

“…Despite the contents of metals remaining in the mine wastes, the potential for exploitation is hampered by the classification of the Plombières area as a nature reserve. Such factors should also be included in mineral resource estimates as modifying factors [64], since this means that legislation would make it difficult to get the required licenses for mining. Additionally, the whole area of Plombières is known for tourism and agriculture.…”

“…The bulk density of the metallurgical waste was estimated to be 1.3 t/m 3 , this being the mean value given for polymetallic (Pb, Cu, Zn, Cr, Fe) metallurgical waste by Kicinska (2020). For both tailings layers, the bulk density was assumed to be 2.0 t/m 3 , according to the review of Kuhn and Meima (2019), who based the average density on several articles [10,64]. Accordingly, the total tonnages of Pb and Zn in the metallurgical waste and brown tailings were estimated to be 279.9 t and 373.3 t, respectively [65].…”