Technical features of Pb-Zn slag that allow its valorization and application

Abstract

According to earlier physical-chemical and mineralogical analysis, slag from "Topionica"- Veles (Northern Macedonia) represents a potentially important raw resource. It is an inhomogeneous raw material with considerable nonferrous metal content, particularly Pb, Zn, Cu, and Ag (considered as a precious metal). This technogenic resource's mineralogical analysis revealed a very complex composition: amorphous phase, lead alloys, zinc alloys, wüstite (FeO), sphalerite, galena, cerussite, elemental silver, elemental copper, elemental iron, magnetite, spinel, rutile, hematite, troilite (FeS). The most abundant phase is an amorphous phase (glassy matrix) composed of spinel, silicate, and mixed (spinel-silicate). The sample has substantially less wüstite, that appears as skeletal inclusions in the glassy matrix. SEM investigation revealed the presence of Fe-Mn-Zn spinels in the Pb-Zn slag, as well as Pb and Zn alloys. These alloys are primarily composed of Cu. The grains of these phases are up to 100μm appearing as inclusions (usually as complex inclusions with a glassy matrix of elemental iron and wüstite). Grains bigger than 100μm in length are typically free or have simple inclusions. The biggest grains in the aforementioned stages have diameters of up to 300μm. The mineralogical study revealed that the Pb-Zn slag is a very complex raw material. It is required to investigate it in detail and establish the methods in which it can be done in order to value it and eventually apply it. Every stage of the preparation process has to be accompanied by numerous analyzes that will indicate the relevance of the preparation process and ways of concentrating useful components into commercial products.