Insights into CO2-mineralization using non-ferrous metallurgy slags: CO2(g)-induced dissolution behavior of copper and lead slags

Abstract

The possibility of utilizing non-ferrous slags for CO2-mineralization is explored in this study by investigating their dissolution behaviors in CO2-environments, since dissolution is usually considered as a major rate-limiting step during CO2-mineralization. Dissolution of two copper slags and a lead slag are studied at the liquid to solid ratio (w/w) of 1000 at combinations of two temperatures (30 and 60 °C) and two CO2-pressures (1 and 10 barg) with time (30, 60, 120, and 240 min). Among the systems in which the slags are dissolved in CO2-environments, the lead slag exhibits Fe-dissolution of up to 10%, and the copper slags up to 5–6% within four hours. The solution-pH were between 4 and 5 in almost all the observations. The dissolution rates of the slags are found to be in the range of 10−7-10−9 mol/m2/s which are comparable with the dissolution of natural fayalite in (in)organic acids. Following the dissolution during the initial 30–60 min, the systems at a higher temperature (at constant CO2-pressure) and higher CO2-pressure (at constant temperature) exhibit higher (or comparable) [Ca], [Fe], [Si], and solution-pH. Moreover, even though the systems at higher temperature and CO2-pressure exhibit higher solution-pH following the initial 30–60 min of dissolution, they continue to exhibit higher dissolution rates throughout the study. Since the residues like non-ferrous copper and lead slags are readily available compared to the analogous natural minerals (like olivines) that usually need to be pre-processed before carbonation, they are proposed as promising sources for CO2-mineralization.