We investigated enhanced CO2 sequestration by wastes from steel and oil industries combined with the reuse of different wastewaters. CO2 could be captured in a two-step indirect mineral carbonation process where steel slags with reject brine (desalination plant), polluted groundwater (ferroalloy plant), and wastewater (oil refinery) were continuously provided to sequester the CO2 and treat the wastewaters simultaneously. We also tested the feasibility of wastewater reuse after the carbonation stage by returning it to the steel slags dissolution step repeatedly. The carbonation process was operated under atmospheric pressure. Acetic acid was used as a representative dissolution agent of which efficiency was tested by the content of Ca2+ extraction from the steel slag at each two-step indirect carbonation cycle. Experimental tests and geochemical simulations (PHREEQC) were conducted to provide an enhanced method of CO2 sequestration and wastewater treatment at the same time. In comparison with multi-step mineral carbonation processes, our two-stage carbonation process with the reuse of wastewaters could considerably reduce its operating costs with higher carbonation reactivity and CO2 uptake. The reject brine and wastewater showed the highest reusability potential with 10 regeneration cycles. The reusability of wastewaters was significantly influenced by their type, and they could be mostly and properly treated during the repeated carbonation cycles. The contents of the carbonation product (i.e., calcite) analyzed by XRD decreased as the repeated stage number increased. The research provided the background knowledge of the enhanced CO2 sequestration method in conjunction with repeated proper treatment of industrial wastewaters.

Enhanced CO2 sequestration by steel slag carbonation with the reuse of wastewaters

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.