GIST Repository
College of Engineering
Department of Environment and Energy Engineering
4. Theses(Ph.D)
Enhancing Sustainable Resource Circulation through pH Swing-Assisted Carbon Mineralization: Integrating CO₂ storage, Utilization, and valuable Metal Recovery
- Abstract
- Ex-situ carbon mineralization has emerged as a promising method for permanently sequestering carbon dioxide (CO₂) by transforming it into stable solid carbonates (CaCO₃, MgCO₃) through reactions with alkaline metals (Ca, Mg). Industrial by-products from iron and steelmaking processes have been evaluated as a suitable feedstock due to their high CO₂ storage potential and ability to reduce landfill burdens while recovering valuable resources. However, the unpredictable physicochemical properties of these by-products, low valuable metal recovery efficiency, and limited value of the final products pose commercialization challenges. Low leaching efficiency further reduces carbonation performance, making it difficult to implement. To address these issues, this dissertation proposes a pH swing-assisted carbon mineralization process to recover valuable metals and store CO₂, evaluating its feasibility and offering specific solutions for overcoming commercialization challenges.
In chapter 1, the background of ex-situ carbon mineralization technology and its potential application to iron and steelmaking by-products were introduced. Key challenges such as improving metal recovery, enhancing the value of final products, and boosting leaching efficiency for better carbonation were discussed, with proposed strategies outlined in Chapters 2, 3, and 4.
In chapter 2, pH swing-based carbon mineralization was applied to six domestic by-products from various generation processes, and their physicochemical characteristics were investigated. The results revealed significant variations in leaching, precipitation, and carbonation behaviors depending on the generation process. The simultaneous application of a reductant and organic acid to steel slag demonstrated a synergistic effect, improving both leaching efficiency and metal recovery.
In chapter 3, the formation conditions and mechanisms of CaCO₃ polymorphs, the final product, were explored to enhance its value. Spectroscopy and transmission electron microscopy (TEM) were employed to characterize the crystallographic properties of each polymorph. The findings indicated that Nuclear Magnetic Resonance (NMR) bulk analysis could offer greater efficiency for commercial applications, and two distinct crystal structures within vaterite were thoroughly confirmed.
In chapter 4, CaO/CaCO₃ composites were developed for high-value applications as thermochemical storage sorbents. Doping with transition metal additives provided excellent photo-to-thermal and thermo-to-chemical energy conversion performance, which was further enhanced by co-doping with CaCl₂ to improve reactivity. Overall, this dissertation demonstrated the feasibility of ex-situ carbon mineralization for CO₂ storage and metal recovery, providing a foundation for the conversion of by-products into high-value products. These results could significantly contribute to the commercialization of carbon mineralization and resource circularity.
- Issued Date
- 2025
- Type
- Thesis
- Alternative Author(s)
- Soyoung Noh
- Department
- 대학원 환경에너지공학부
- Advisor
- Park, Youngjune
- Table Of Contents
- Abstract i
Contents ii
List of Figures v
List of Tables viii
Chapter 1. Introduction 1
1.1. Global climate change and transition toward a carbon circular economy 2
1.2. Carbon mineralization for carbon capture, utilization, and storage (CCUS) technologies 2
1.2.1. Iron and steelmaking by-products for ex-situ carbon mineralization 6
1.2.2. Challenges for ex-situ carbon mineralization 8
1.3. References 21
Chapter 2. Integrated approach to carbon mineralization and valuable element recovery from iron and steelmaking by-products 28
2.1. Investigation of iron and steelmaking by-products via pH swing-assisted carbon process 29
2.1.1. Motivation 29
2.1.2. Materials and methods 30
2.1.2.1. Materials 30
2.1.2.2. Multi-step pH swing procedure for carbon process 30
2.1.2.3. Characterizations 31
2.1.3. Results and discussion 32
2.1.3.1. Characterization of iron and steelmaking slag 32
2.1.3.2. Leaching behavior of major elements 34
2.1.3.3. pH swing precipitation behavior of major elements 35
2.1.3.4. Carbonation capacity and high purity CaCO3 38
2.1.4. Conclusion 40
2.1.5. References 54
2.2. Enhancement of metal extraction from steelmaking slag via synergistic effect of biogenic volatile
organic acids and reductants 57
2.2.1. Motivation 57
2.2.2. Materials and methods 57
2.2.2.1. Materials 57
2.2.2.2. Leaching experiment for reductant and ligand effect 58
2.2.2.3. Multi-step pH swing procedure for carbonation process 59
2.2.2.4. Characterizations 59
2.2.3. Results and discussion 60
2.2.3.1. Characterization of electric arc furnace slag (EAF) 60
2.2.3.2. Leaching behavior in model chemical: the effect of reductants 61
2.2.3.3. Leaching behavior in EAF: synergistic effect of reductants and ligands 62
2.2.3.4. pH swing precipitation and carbonation behavior in EAF 64
2.2.4. Conclusion 67
2.2.5. References 80
Chapter 3. Polymorph-controlled synthesis and structural validation of calcium carbonate polymorphs for high value-added production 82
3.1. Polymorph-controlled synthesis of calcium carbonate: formation conditions of calcite, aragonite,
vaterite 83
3.1.1. Motivation 83
3.1.2. Mechanism and formation condition for calcium carbonate polymorphs 84
3.1.3. Physicochemical properties and applications of calcite, aragonite, vaterite 87
3.1.4. Conclusion 88
3.1.5. References 92
3.2. Crystallographic investigation of calcium carbonate polymorphs: focus on two crystal structures of
vaterite 95
3.2.1. Motivation 95
3.2.2. Materials and methods 96
3.2.2.1. Materials 96
3.2.2.2. Synthesis for calcium carbonate based on three polymorphs 96
3.2.2.3. Characterizations for synthesized calcium carbonate 97
3.2.2.4. 13C solid-state NMR spectroscopy 97
3.2.3. Results and discussion 98
3.2.3.1. Crystalline structure of polymorph-controlled calcium carbonate 98
3.2.3.2. The two crystalline structures of vaterite 99
3.2.4. Conclusion 103
3.2.5. References 119
Chapter 4. Application of high value-added calcium carbonate: thermochemical energy storage sorbent 122
4.1. Effect of Co and Mn doping on CaO/CaCO3-based sorbent for enhanced photo-to-thermal energy
conversion in concentrated solar power systems 123
4.1.1. Motivation 123
4.1.2. Materials and methods 125
4.1.2.1. Materials 125
4.1.2.2. Synthesis of CaO/CaCO3-based sorbents 125
4.1.2.3. Characterizations 126
4.1.2.4. Optical absorption analysis 126
4.1.2.5. Photo-to-thermal energy conversion efficiency measurement 127
4.1.2.6. Iterative carbonation-calcination reaction stability analysis 128
4.1.3. Results and discussion 129
4.1.3.1. Characterizations of synthesized CaO/CaCO3-based sorbents 129
4.1.3.2. Optical absorbance and photo-to-thermal energy conversion efficiency 129
4.1.3.3. Reaction stability analysis 131
4.1.4. Conclusion 132
4.1.5. References 143
4.2. Effect of CaCl2 addition to CaO/CaCO3-based sorbent on iterative reaction and absorbance for
thermochemical energy storage 148
4.2.1. Motivation 148
4.2.2. Carbonation-calcination reaction mechanism and deactivation phenomena 149
4.2.3. Materials and methods 151
4.2.3.1. Materials 151
4.2.3.2. Synthesis of CaCl2 addition to CaO/CaCO3-based sorbents 151
4.2.4. Results and discussion 152
4.2.4.1. Enhancement of reactivity and optical absorbance CaCl2 addition 152
4.2.5. Conclusion 154
4.2.6. References 161
Chapter 5. Conclusion 165
Curriculum Vitae 167
- Degree
- Doctor
- Appears in Collections:
- Department of Environment and Energy Engineering > 4. Theses(Ph.D)
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