Carbon Mineralization-Based Valuable Metal Recovery: Development of Novel Urban Resource Recycling Pathways Integrated with Carbon Capture, Utilization and Storage

Abstract

Solid carbon mineralization technology has emerged as a promising storage option to achieve substantial CO2 reduction. Although a number of approaches for this technology have been investigated over the past few decades, it has yet to be demonstrated on a large scale. Understanding the complexities of feedstocks, enhancing reaction kinetics and carbonation, and producing high valuable materials should be carried out to address the limitations of the current technology. This dissertation proposes a new concept in the pH swing carbon mineralization process, which can be used as a practical strategy for waste-to-resource supply chains towards net-zero CO2 emissions. Iron and steelmaking wastes are promising feedstock in the carbon mineralization process, and their physicochemical properties and potential CO2 storage capacities were investigated. Among the iron and steelmaking wastes, iron and steel slags were used as feedstock and their extraction characteristics were also examined under various operating conditions. In addition, organic acids derived from biomass were examined as an extraction solvent to reduce the use of solvent and improve process efficiency, and they were found to improve the extraction performances of iron and steel slags compared with conventional solvents. To enhance process efficiency and produce high-valuable materials, pH swing carbon mineralization using iron slag and organic ligands was developed and investigated in a large-scale demonstration. However, this process still required the use of a huge amount of solvents in the carbonation step, with a low conversion yield. The carbonation was integrated with amine-based CO2 capture to make up for this limitation. CO2 was employed as the carbonate ions, which prevented pH change during carbonation, improving conversion yield and reducing the use of solvent, with energy-efficient amine regeneration. As a result, CO2-captured amines were mostly mainly recovered and the high-purity CaCO3 was produced. Based on results, the novel pH swing carbon mineralization process described in this dissertation suggests a new strategy for moving the waste-to-resource supply chain towards net-zero CO2 emissions.