Microstructural analysis of slag properties associated with calcite precipitation due to passive CO2 mineralization

Khudhur, F. W.K. , MacDonald, J. M. , Daly, L. , Macente, A. , Spruženiece, L. , Griffin, S. and Wilson, C. (2023) Microstructural analysis of slag properties associated with calcite precipitation due to passive CO2 mineralization. Micron, 174, 103532. (doi: 10.1016/j.micron.2023.103532) (PMID:37683551)

Abstract

CO2 mineralization in slag has gained significant attention since it occurs with minimal human intervention and energy input. While the amount of theoretical CO2 that can be captured within slag has been quantified based on slag composition in several studies, the microstructural and mineralogical effects of slag on its ability to capture CO2 have not been fully addressed. In this work, the CO2 uptake within legacy slag samples is analyzed through microstructural characterization. Slag samples were collected from the former Ravenscraig steelmaking site in Lanarkshire, Scotland. The collected samples were studied using X-ray Computed Tomography (XCT) to understand the distribution and geometry of pore space, as well as with scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) to visualize the distribution of elements within the studied samples. Electron backscatter diffraction (EBSD) was used to study the minerals distribution. The samples were also characterized through X-ray diffraction (XRD) and X-ray fluorescence (XRF), and the amount of captured CO2 was quantified using thermogravimetric analysis (TGA). Our results demonstrate that CO2 uptake occurs to the extent of ∼9–30 g CO2/ kg slag. The studied samples are porous in nature, with pore space occupying up to ∼30% of their volumes, and they are dominated by åkermanite-gehlenite minerals which interact with the atmospheric CO2 slowly at ambient conditions. EDS and EBSD results illustrate that the precipitated carbonate in slag is calcite, and that the precipitation of calcite is accompanied by the formation of a Si-O-rich layer. The provided analysis concludes that the porous microstructure as well as the minerals distribution in slag should be considered in forecasting and designing large-scale solutions for passive CO2 mineralization in slag.

• Item Type: Articles
• Additional Information: FWKK acknowledges the generous support of a University of Glasgow Lord Kelvin/Adam Smith scholarship. AM was supported by the Oil and Gas Innovation Centre.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wilson, Dr Claire and Spruzeniece, Dr Liene and Macente, Dr Alice and Daly, Dr Luke and MacDonald, Dr John and Khudhur, Faisal and Griffin, Dr Sammy
• Authors: Khudhur, F. W.K., MacDonald, J. M., Daly, L., Macente, A., Spruženiece, L., Griffin, S., and Wilson, C.
• College/School: College of Science and Engineering > School of Chemistry; College of Science and Engineering > School of Geographical and Earth Sciences; College of Science and Engineering
• Journal Name: Micron
• Publisher: Elsevier
• ISSN: 0968-4328
• ISSN (Online): 1878-4291
• Published Online: 30 August 2023
• Copyright Holders: Copyright: © 2023 The Author(s)
• First Published: First published in Micron 174: 103532
• Publisher Policy: Reproduced under a Creative Commons licence