The water resistance of building gypsum products was poor, which led to certain limitations in their application. In this paper, calcium oxide and slag were added to building gypsum to study the effect of calcium oxide alkali activation of slag on the water resistance of building gypsum. Low-field nuclear magnetic resonance technology, X-ray diffraction technology, and other modern testing techniques were employed to investigate the hydration process and water resistance mechanism of building gypsum. It was found that the use of calcium oxide to activate slag could effectively enhance the water resistance of building gypsum. It was discovered that when the dosage of slag was 50 % and the dosage of calcium oxide was 2 % of the slag, the softening coefficient of building gypsum after 28 days was increased from 0.26 to 0.93. When calcium oxide was used to activate slag, not only was C-(A)-S-H gel formed, but also more ettringite was produced. The formation of ettringite and C-(A)-S-H gel was greatly influenced by the presence of water. These substances were found to have stronger water resistance compared to gypsum crystals. The structural system built by the interlocking of these substances significantly enhanced the water resistance of the samples, thereby improving the water resistance of building gypsum blocks. Simultaneously, at a lower addition rate (2 % relative to the amount of slag), as the replacement amount of slag increased, the cost of the samples and the carbon emissions were also relatively reduced.
{"title":"Improving the water resistance of gypsum-based building materials with slag activated by calcium oxide","authors":"Chunhua Feng, Yisen Wang, Luwei Wang, Xiaomeng Zhao, Wenyan Zhang, Jianping Zhu, Mingxing Du","doi":"10.1016/j.jcou.2024.102996","DOIUrl":"10.1016/j.jcou.2024.102996","url":null,"abstract":"<div><div>The water resistance of building gypsum products was poor, which led to certain limitations in their application. In this paper, calcium oxide and slag were added to building gypsum to study the effect of calcium oxide alkali activation of slag on the water resistance of building gypsum. Low-field nuclear magnetic resonance technology, X-ray diffraction technology, and other modern testing techniques were employed to investigate the hydration process and water resistance mechanism of building gypsum. It was found that the use of calcium oxide to activate slag could effectively enhance the water resistance of building gypsum. It was discovered that when the dosage of slag was 50 % and the dosage of calcium oxide was 2 % of the slag, the softening coefficient of building gypsum after 28 days was increased from 0.26 to 0.93. When calcium oxide was used to activate slag, not only was C-(A)-S-H gel formed, but also more ettringite was produced. The formation of ettringite and C-(A)-S-H gel was greatly influenced by the presence of water. These substances were found to have stronger water resistance compared to gypsum crystals. The structural system built by the interlocking of these substances significantly enhanced the water resistance of the samples, thereby improving the water resistance of building gypsum blocks. Simultaneously, at a lower addition rate (2 % relative to the amount of slag), as the replacement amount of slag increased, the cost of the samples and the carbon emissions were also relatively reduced.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102996"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102988
Moshood O. Bolarinwa , Aasif A. Dabbawala , Shamraiz Hussain Talib , Georgian Melinte , Thomas Delclos , Abdulmuizz Adamson , Abbas Khaleel , Kyriaki Polychronopoulou , Dalaver H. Anjum
Single-atom catalysts (SACs) offer high efficiency and selectivity in chemical reactions but face challenges in converting CO2 to CO via the reverse water gas shift (RWGS) reactions. This study addresses these challenges by anchoring three noble metals (Ir, Pd, and Ru) onto titania (TiO2) and analyzing their performance. Comprehensive characterization techniques, including electron microscopy, confirmed the uniform dispersion of metal atoms on TiO2. Among the catalysts, Ir/TiO2 exhibited the best results, achieving an 84 % CO2 conversion rate and ∼98 % CO selectivity, surpassing Pd/TiO2 and Ru/TiO2, which gained 56 % and 52 % conversion, respectively. In-situ gas transmission electron microscopy revealed the catalytic behavior of Ir/TiO2, showing Ir atom mobility and the formation of ∼1 nm nanoclusters. Density functional theory (DFT) and in-situ diffuse reflectance infrared spectroscopy (DRIFTs) further explained that the atomically dispersed Ir sites in Ir/TiO2 follow a hydrogen-assisted mechanism, with the COOH* intermediate desorbing and dissociating into CO. These findings suggest SACs' potential to facilitate greener chemical processes and reduce greenhouse gas emissions.
{"title":"High-performance single-atom M/TiO2 catalysts in the reverse water-gas shift reaction: A comprehensive experimental and theoretical investigation","authors":"Moshood O. Bolarinwa , Aasif A. Dabbawala , Shamraiz Hussain Talib , Georgian Melinte , Thomas Delclos , Abdulmuizz Adamson , Abbas Khaleel , Kyriaki Polychronopoulou , Dalaver H. Anjum","doi":"10.1016/j.jcou.2024.102988","DOIUrl":"10.1016/j.jcou.2024.102988","url":null,"abstract":"<div><div>Single-atom catalysts (SACs) offer high efficiency and selectivity in chemical reactions but face challenges in converting CO<sub>2</sub> to CO via the reverse water gas shift (RWGS) reactions. This study addresses these challenges by anchoring three noble metals (Ir, Pd, and Ru) onto titania (TiO<sub>2</sub>) and analyzing their performance. Comprehensive characterization techniques, including electron microscopy, confirmed the uniform dispersion of metal atoms on TiO<sub>2</sub>. Among the catalysts, Ir/TiO<sub>2</sub> exhibited the best results, achieving an 84 % CO<sub>2</sub> conversion rate and ∼98 % CO selectivity, surpassing Pd/TiO<sub>2</sub> and Ru/TiO<sub>2</sub>, which gained 56 % and 52 % conversion, respectively. In-situ gas transmission electron microscopy revealed the catalytic behavior of Ir/TiO<sub>2</sub>, showing Ir atom mobility and the formation of ∼1 nm nanoclusters. Density functional theory (DFT) and in-situ diffuse reflectance infrared spectroscopy (DRIFTs) further explained that the atomically dispersed Ir sites in Ir/TiO<sub>2</sub> follow a hydrogen-assisted mechanism, with the COOH* intermediate desorbing and dissociating into CO. These findings suggest SACs' potential to facilitate greener chemical processes and reduce greenhouse gas emissions.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102988"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102990
Zhijiang Li , Suikang Zhang , Cai Wu , Daopei Zhu
In the realm of metal mine tailings management, enhancing the performance of Cemented Lithium Feldspar Tailings Backfill Composites (CTBC) is highly crucial. This study delved into the influence of fiber on the flexural strength of CTBC. Employing orthogonal three-point bending tests and numerical simulations, it examined how fiber type, content, solid content, and the cement-to-tailings ratio (c/t) affected CTBC flexural strength and post-peak toughness. Findings demonstrated that fiber content and c/t notably influenced flexural strength, with c/t being more significant (weights of 1.78 and 7.04 respectively via range). The flexural strength of CTBC changed with fiber content and c/t, and 70 % was the optimal solid content. PVA fibers exhibited the best enhancement. The yield deflection of fiber-reinforced CTBC exceeded that at the peak, and post-peak toughness was mainly affected by fiber content and type (relative values 2.25 and 3.625). CTBC beams cracked prior to peak load, and fiber addition postponed crack extension. The fitting model boasted high prediction reliability (correlation coefficients for flexural strength, deflection, and peak load regression models were 1, 0.988, and 0.999 respectively; correction coefficients were 1, 0.987, and 0.999 respectively)
{"title":"Influence of fiber type and content on the flexural strength of cemented lithium feldspar tailings backfill composites","authors":"Zhijiang Li , Suikang Zhang , Cai Wu , Daopei Zhu","doi":"10.1016/j.jcou.2024.102990","DOIUrl":"10.1016/j.jcou.2024.102990","url":null,"abstract":"<div><div>In the realm of metal mine tailings management, enhancing the performance of Cemented Lithium Feldspar Tailings Backfill Composites (CTBC) is highly crucial. This study delved into the influence of fiber on the flexural strength of CTBC. Employing orthogonal three-point bending tests and numerical simulations, it examined how fiber type, content, solid content, and the cement-to-tailings ratio (c/t) affected CTBC flexural strength and post-peak toughness. Findings demonstrated that fiber content and c/t notably influenced flexural strength, with c/t being more significant (weights of 1.78 and 7.04 respectively via range). The flexural strength of CTBC changed with fiber content and c/t, and 70 % was the optimal solid content. PVA fibers exhibited the best enhancement. The yield deflection of fiber-reinforced CTBC exceeded that at the peak, and post-peak toughness was mainly affected by fiber content and type (relative values 2.25 and 3.625). CTBC beams cracked prior to peak load, and fiber addition postponed crack extension. The fitting model boasted high prediction reliability (correlation coefficients for flexural strength, deflection, and peak load regression models were 1, 0.988, and 0.999 respectively; correction coefficients were 1, 0.987, and 0.999 respectively)</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102990"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The integration of accelerated carbonation with the utilization of steelmaking slags presents a vital strategy for CO2 mineralization towards net-zero scheme. This study simultaneously evaluates basic oxygen furnace slag (BOFS), refining slag (RFS), and electric arc furnace reducing (EAFRS) and oxidizing slags (EAFOS) as potential partial replacements for ordinary Portland cement, at substitution levels ranging from 5 % to 15 % as supplementary cementitious materials (SCMs). These slags were pretreated through aqueous accelerated carbonation in a high-gravity rotating packed bed. We assessed several parameters, including carbonation conversion, CO2 capture capacity, workability, strength, and durability. The results demonstrated that EAFRS achieved the highest CO2 capture capacity, reaching 0.193 kg-CO2/kg-slag with a maximum carbonation conversion of 46 % under 197 times high-gravity conditions and a liquid-to-solid ratio of 20. While the incorporation of carbonated slags had minimal impact on the setting properties of cement pastes, higher substitution ratios necessitated increased water demand. The strength of blended cement containing 5 %, 10 %, and 15 % of carbonated BOFS, RFS, and EAFRS met standard requirements at 28th day. Additionally, a mathematical model was developed to predict the mechanical strength of cement mortars. The introduction of carbonated BOFS, RFS, and EAFRS facilitated hydration due to the formation of calcium carbonates, although it resulted in slower strength development kinetics. Notably, the replacement of cement with carbonated EAFOS exhibited a higher expansion rate, likely due to its elevated silicon dioxide and alkaline species content, which may lead to alkali-aggregate reactions, resulting in expansion and cracking.
{"title":"Simultaneously comparing various CO2-mineralized steelmaking slags as supplementary cementitious materials via high gravity carbonation","authors":"Tse-Lun Chen , Bo-Kai Shu , Yi-Hung Chen , Pen-Chi Chiang","doi":"10.1016/j.jcou.2024.102985","DOIUrl":"10.1016/j.jcou.2024.102985","url":null,"abstract":"<div><div>The integration of accelerated carbonation with the utilization of steelmaking slags presents a vital strategy for CO<sub>2</sub> mineralization towards net-zero scheme. This study simultaneously evaluates basic oxygen furnace slag (BOFS), refining slag (RFS), and electric arc furnace reducing (EAFRS) and oxidizing slags (EAFOS) as potential partial replacements for ordinary Portland cement, at substitution levels ranging from 5 % to 15 % as supplementary cementitious materials (SCMs). These slags were pretreated through aqueous accelerated carbonation in a high-gravity rotating packed bed. We assessed several parameters, including carbonation conversion, CO<sub>2</sub> capture capacity, workability, strength, and durability. The results demonstrated that EAFRS achieved the highest CO<sub>2</sub> capture capacity, reaching 0.193 kg-CO<sub>2</sub>/kg-slag with a maximum carbonation conversion of 46 % under 197 times high-gravity conditions and a liquid-to-solid ratio of 20. While the incorporation of carbonated slags had minimal impact on the setting properties of cement pastes, higher substitution ratios necessitated increased water demand. The strength of blended cement containing 5 %, 10 %, and 15 % of carbonated BOFS, RFS, and EAFRS met standard requirements at 28th day. Additionally, a mathematical model was developed to predict the mechanical strength of cement mortars. The introduction of carbonated BOFS, RFS, and EAFRS facilitated hydration due to the formation of calcium carbonates, although it resulted in slower strength development kinetics. Notably, the replacement of cement with carbonated EAFOS exhibited a higher expansion rate, likely due to its elevated silicon dioxide and alkaline species content, which may lead to alkali-aggregate reactions, resulting in expansion and cracking.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102985"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102998
Ying Su , Yelin Qian , Ming Sun , Changchun Li , Chunmei Liu , Dan Zhang , Xiaodong Zhang , Jun Yang , Yan Zhao , Rui Tao , Fengxia Xu
Magnesium phosphate cement (MPC) is a new type of repair material that is fast-setting, resistant to acids and alkalis, and environmentally friendly. Compared to commonly used repair materials and protective coatings, such as sulphoaluminate cement, epoxy resin, and zinc phosphate, MPC significantly reduces carbon dioxide emissions throughout its entire lifecycle (from raw material extraction to application, service, and waste disposal). Additionally, its advantages of fast curing, early strength, and excellent adhesion make it suitable for rapid repair of damaged roads and bridges. Furthermore, incorporating industrial by-products such as fly ash (FA) into MPC results in a cement that combines the advantageous properties of FA, offering excellent workability and durability. The substitution of FA for raw materials in MPC reduces the reliance on dead-burned MgO, contributing to a further reduction in CO2 emissions and lessening the impact on the natural environment. Studies have shown that MPC exhibits a decrease in strength under high humidity and water-curing conditions, and the addition of FA can help improve this phenomenon. However, the research lacks investigations on the effect of FA on the performance of MPC under different curing methods, with the same mix ratios and experimental conditions. This paper investigates the effects of FA content on MPC under standard curing conditions by measuring setting time, fluidity, and mechanical properties, as well as conducting microstructural characterization using XRD, FT-IR, and SEM. The results indicate that the addition of FA prolongs the setting time and decreases fluidity. Under standard curing conditions, the flexural strength after curing is higher than that under air curing, due to the formation of more gel-like products, which contribute to a denser microstructure favorable for the development of flexural strength. Moreover, standard curing conditions also promote the improvement of bonding strength. The bonding strength with the old substrate is higher than the flexural strength of FA-MPC itself, indicating that this material meets the requirements for the repair of highways and bridges. However, SEM analysis reveals that the moisture-rich curing environment may lead to cracking and damage in the hydration products of MPC, resulting in a reduction in compressive strength. The incorporation of FA enhances the mechanical properties of MPC through both the filling effect and pozzolanic activity, partially replacing MgO. Moreover, the addition of FA lowers the global warming potential (GWP) of MPC, reduces carbon emissions, and promotes more sustainable development.
{"title":"The effects of curing conditions on the performance and carbon dioxide emissions of fly ash-magnesium phosphate cement repair materials for pavement maintenance","authors":"Ying Su , Yelin Qian , Ming Sun , Changchun Li , Chunmei Liu , Dan Zhang , Xiaodong Zhang , Jun Yang , Yan Zhao , Rui Tao , Fengxia Xu","doi":"10.1016/j.jcou.2024.102998","DOIUrl":"10.1016/j.jcou.2024.102998","url":null,"abstract":"<div><div>Magnesium phosphate cement (MPC) is a new type of repair material that is fast-setting, resistant to acids and alkalis, and environmentally friendly. Compared to commonly used repair materials and protective coatings, such as sulphoaluminate cement, epoxy resin, and zinc phosphate, MPC significantly reduces carbon dioxide emissions throughout its entire lifecycle (from raw material extraction to application, service, and waste disposal). Additionally, its advantages of fast curing, early strength, and excellent adhesion make it suitable for rapid repair of damaged roads and bridges. Furthermore, incorporating industrial by-products such as fly ash (FA) into MPC results in a cement that combines the advantageous properties of FA, offering excellent workability and durability. The substitution of FA for raw materials in MPC reduces the reliance on dead-burned MgO, contributing to a further reduction in CO<sub>2</sub> emissions and lessening the impact on the natural environment. Studies have shown that MPC exhibits a decrease in strength under high humidity and water-curing conditions, and the addition of FA can help improve this phenomenon. However, the research lacks investigations on the effect of FA on the performance of MPC under different curing methods, with the same mix ratios and experimental conditions. This paper investigates the effects of FA content on MPC under standard curing conditions by measuring setting time, fluidity, and mechanical properties, as well as conducting microstructural characterization using XRD, FT-IR, and SEM. The results indicate that the addition of FA prolongs the setting time and decreases fluidity. Under standard curing conditions, the flexural strength after curing is higher than that under air curing, due to the formation of more gel-like products, which contribute to a denser microstructure favorable for the development of flexural strength. Moreover, standard curing conditions also promote the improvement of bonding strength. The bonding strength with the old substrate is higher than the flexural strength of FA-MPC itself, indicating that this material meets the requirements for the repair of highways and bridges. However, SEM analysis reveals that the moisture-rich curing environment may lead to cracking and damage in the hydration products of MPC, resulting in a reduction in compressive strength. The incorporation of FA enhances the mechanical properties of MPC through both the filling effect and pozzolanic activity, partially replacing MgO. Moreover, the addition of FA lowers the global warming potential (GWP) of MPC, reduces carbon emissions, and promotes more sustainable development.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102998"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102997
Hamideh Khodabandeh, Ali Nakhaei Pour , Ali Mohammadi
Density functional theory (DFT) computations were applied to study the adsorption of intermediates, the thermodynamic and kinetic mechanism of the conversion of CO2 to methanol upon the W-doped Cu surface, and the effect of W-doping on the decomposition and selectivity of methanol. For this reason, the adsorption structures and energies for the most stable structures were calculated. The outcomes displayed that the adsorption of intermediates over the surface of Cu-W is more powerful than the surface of Cu due to strain and ligand effect. Two reaction pathways of methanol synthesis (formate and carboxyl routs) were studied. The transition situation configurations and the potential energy profiles associated with each primary stage upon the surfaces of Cu (111) and Cu-W (111) were explored. The relevant activation barrier, rate constant, reaction energy, and Gibbs free energy for each primary stage were computed and the rate-limiting stages were determined. The Brønsted-Evans-Polanyi (BEP) relationships were used to study which pathway of conversion of CO2 to methanol is better. The outcomes indicated that W weakens the performance of the catalyst and the carboxyl route is more suitable than the formate route due to the low activation barrier for most of its primary stages. Also, the outcomes indicated that W-doping increased the methanol decomposition and reduced the selectivity of methanol.
{"title":"Mechanistic investigation of CO2 hydrogenation to methanol on W-doped Cu surfaces","authors":"Hamideh Khodabandeh, Ali Nakhaei Pour , Ali Mohammadi","doi":"10.1016/j.jcou.2024.102997","DOIUrl":"10.1016/j.jcou.2024.102997","url":null,"abstract":"<div><div>Density functional theory (DFT) computations were applied to study the adsorption of intermediates, the thermodynamic and kinetic mechanism of the conversion of CO<sub>2</sub> to methanol upon the W-doped Cu surface, and the effect of W-doping on the decomposition and selectivity of methanol. For this reason, the adsorption structures and energies for the most stable structures were calculated. The outcomes displayed that the adsorption of intermediates over the surface of Cu-W is more powerful than the surface of Cu due to strain and ligand effect. Two reaction pathways of methanol synthesis (formate and carboxyl routs) were studied. The transition situation configurations and the potential energy profiles associated with each primary stage upon the surfaces of Cu (111) and Cu-W (111) were explored. The relevant activation barrier, rate constant, reaction energy, and Gibbs free energy for each primary stage were computed and the rate-limiting stages were determined. The Brønsted-Evans-Polanyi (BEP) relationships were used to study which pathway of conversion of CO<sub>2</sub> to methanol is better. The outcomes indicated that W weakens the performance of the catalyst and the carboxyl route is more suitable than the formate route due to the low activation barrier for most of its primary stages. Also, the outcomes indicated that W-doping increased the methanol decomposition and reduced the selectivity of methanol.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102997"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102993
Sudharsan Rathnakumar, Nishant Garg
Cementitious carbonation is an important phenomenon considering its dual implications on durability (carbonation-induced steel corrosion) and sustainability (CO2 mineralization in carbonatable binders). Currently, there is strong interest in understanding the nature of the carbonation front and resolving microstructural changes that happen upon carbonation. In this study, we shed light on these issues by adopting a multi-modal imaging approach wherein we deploy three complementary methods on the same specimen that has undergone carbonation: laser profilometry, contact angle goniometry, and Raman imaging. Firstly, we find that irrespective of the technique deployed, the carbonation front is non-planar, and its width can be on the order of a few millimeters. Secondly, the intersection region of calcite and portlandite mineral maps roughly correlates with the front as mapped from imaging methods. Thirdly, and finally, the carbonated region of hydrated cement samples seems to have undergone measurable pore refinement. Thus, we demonstrate the efficacy of multi-modal imaging in improving our understanding of cementitious carbonation front.
{"title":"Multi-modal imaging of the cementitious carbonation front: Evidence for pore refinement","authors":"Sudharsan Rathnakumar, Nishant Garg","doi":"10.1016/j.jcou.2024.102993","DOIUrl":"10.1016/j.jcou.2024.102993","url":null,"abstract":"<div><div>Cementitious carbonation is an important phenomenon considering its dual implications on durability (carbonation-induced steel corrosion) and sustainability (CO<sub>2</sub> mineralization in carbonatable binders). Currently, there is strong interest in understanding the nature of the carbonation front and resolving microstructural changes that happen upon carbonation. In this study, we shed light on these issues by adopting a multi-modal imaging approach wherein we deploy three complementary methods on the same specimen that has undergone carbonation: laser profilometry, contact angle goniometry, and Raman imaging. Firstly, we find that irrespective of the technique deployed, the carbonation front is non-planar, and its width can be on the order of a few millimeters. Secondly, the intersection region of calcite and portlandite mineral maps roughly correlates with the front as mapped from imaging methods. Thirdly, and finally, the carbonated region of hydrated cement samples seems to have undergone measurable pore refinement. Thus, we demonstrate the efficacy of multi-modal imaging in improving our understanding of cementitious carbonation front.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102993"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102992
Feyza Kazanç, Peng Zhang, Partha Saha, Yongqi Lu
An advanced CO2 mineralization technology using Flue Gas Desulfurization (FGD) byproduct gypsum, which coproduces value-added precipitated calcium carbonate (precipitated CaCO3, PCC) and ammonium sulfate [(NH4)2SO4, AS] fertilizer, is being developed to address the technical challenges of achieving simultaneous CO2 capture and utilization, high CO2 and calcium conversion, and enhanced energy efficiency. This study aimed to conduct a techno-economic analysis (TEA) and a life cycle assessment (LCA) for this technology. In the TEA, mass and energy balances for CO2 mineralization integrated with a power plant to utilize all FGD gypsum and approximately 51,000 tonne/year of CO2 in flue gas were developed through modeling. Major equipment was selected and sized, followed by capital and operating cost analyses. Energy efficiency was improved through the integrated use of both low-grade steam and vacuum from the power plant steam cycle. TEA results revealed that this process was profitable, with a levelized net profit of $328.4 per tonne of CO2 utilized. The LCA was performed as a cradle-to-gate study for comparative assessments of global warming potential (GWP) and other environmental impacts between the CO2 mineralization system (i.e., Proposed Production System or PPS) and the conventional processes (i.e., Comparison Production System or CPS). The PPS resulted in a GWP impact of 0.85 kg CO2-Eq per 1 kg of primary PCC production and 1.32 kg of byproduct AS production, approximately 64 % lower than that of the CPS. The LCA results for other environmental impacts also consistently showed impacts 35–88 % lower for the PPS compared to the CPS.
{"title":"Techno-economic and life cycle environmental assessments of CO2 utilization for value-added precipitated calcium carbonate and ammonium sulfate fertilizer co-production","authors":"Feyza Kazanç, Peng Zhang, Partha Saha, Yongqi Lu","doi":"10.1016/j.jcou.2024.102992","DOIUrl":"10.1016/j.jcou.2024.102992","url":null,"abstract":"<div><div>An advanced CO<sub>2</sub> mineralization technology using Flue Gas Desulfurization (FGD) byproduct gypsum, which coproduces value-added precipitated calcium carbonate (precipitated CaCO<sub>3</sub>, PCC) and ammonium sulfate [(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>, AS] fertilizer, is being developed to address the technical challenges of achieving simultaneous CO<sub>2</sub> capture and utilization, high CO<sub>2</sub> and calcium conversion, and enhanced energy efficiency. This study aimed to conduct a techno-economic analysis (TEA) and a life cycle assessment (LCA) for this technology. In the TEA, mass and energy balances for CO<sub>2</sub> mineralization integrated with a power plant to utilize all FGD gypsum and approximately 51,000 tonne/year of CO<sub>2</sub> in flue gas were developed through modeling. Major equipment was selected and sized, followed by capital and operating cost analyses. Energy efficiency was improved through the integrated use of both low-grade steam and vacuum from the power plant steam cycle. TEA results revealed that this process was profitable, with a levelized net profit of $328.4 per tonne of CO<sub>2</sub> utilized. The LCA was performed as a cradle-to-gate study for comparative assessments of global warming potential (GWP) and other environmental impacts between the CO<sub>2</sub> mineralization system (i.e., Proposed Production System or PPS) and the conventional processes (i.e., Comparison Production System or CPS). The PPS resulted in a GWP impact of 0.85 kg CO<sub>2</sub>-Eq per 1 kg of primary PCC production and 1.32 kg of byproduct AS production, approximately 64 % lower than that of the CPS. The LCA results for other environmental impacts also consistently showed impacts 35–88 % lower for the PPS compared to the CPS.</div></div>","PeriodicalId":350,"journal":{"name":"Journal of CO2 Utilization","volume":"90 ","pages":"Article 102992"},"PeriodicalIF":7.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jcou.2024.102991
Zheng Zhang , Junkang Sang , Mingzhong Shen , Anqi Wu , Kailiang Wang , Junhua Su , Fei Wang , Yingying Han , Wanbing Guan
Methane synthesis from CO2 is an important process for transforming and storing renewable electrical energy, and one of the main issues facing methanation catalysts is stability. Herein, a plate-and-tube structured porous metal-ceramic Ni-YSZ reactor with high-temperature sintering was designed to produce CH4 from CO2 at atmospheric pressure and 325°C. The reactor was steadily operated for 1000 hours. The results showed that both the CO2 conversion and the CH4 selectivity continuously stayed over 90 % and 99.9 %, respectively. The results of in situ infrared and in situ programmed warming characterizations demonstrated that the hydrogenation of oxygen vacancies on the surface of Ni-O-Zr was the main pathway by which CO2 was converted to CH4 in this reactor. Moreover, the strongly basic adsorbed HCOO* and CO* intermediates facilitated further hydrogenation. This reactor structure decreases the reduction in reaction activity associated with catalyst sintering, coalescence, and carbon accumulation. Moreover, it provides a novel approach to reactor design for the stable operation of CO2-derived methane at high temperatures.
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