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.