CO2 Mineralization Research Articles

Mineralized carbon sequestration evaluation of coal-based solid waste consolidated backfill: A novel data-driven approach

The coal mining industry and its byproduct utilization are confronted with challenges such as the accumulation of coal-based solid waste and the emission of CO2, which seriously jeopardize environmental protection. A lucrative way of mitigating these problems is CO2 mineralization storage technology of coal-based solid waste consolidated backfill. Its successful realization stringy depends on the CO2 mineralization sealing stock and requires accurate account of the carbon sequestration rate of cemented backfill. Therefore, this study proposes a novel hybrid intelligent model combining the adaptive enhanced whale optimization algorithm and the support vector regression (A-E-WOA-SVR) to forecast the carbon sequestration performance of cemented backfill. The respective data set of cemented backfill was obtained through laboratory tests under different values of seven factors influencing the carbon sequestration rate, including water–solid ratio, cement ratio, fly ash ratio, slag ratio, curing pressure, curing temperature, and curing time. The results exhibit that the adaptive enhanced whale optimization algorithm can effectively optimize the hyperparameters of the support vector regression. The A-E-WOA-SVR hybrid intelligent model proposed in this paper accurately predicted the carbon sequestration rate of cemented backfill. Coefficient of determination, mean absolute error, root mean square error, and other indices were used to evaluate the performance of the intelligent prediction model. The obtained values of these indices implied small errors. The mean impact value sensitivity analysis revealed that water–solid ratio, cement content, curing pressure, and curing time were the key sensitive factors controlling the carbon sequestration performance of cemented backfill, which should mainly considered in the control of cemented backfill mineralization carbon sequestration performance. The research results provide a theoretical reference which enhance the CO2 mineralization storage performance of coal-based solid waste consolidated backfill.

Experimental study on the effect of hydrothermal activation on the physicochemical properties and mineralization efficiency of fly ash-supercritical CO2

To address the challenge of low mineralization efficiency of fly ash-supercritical carbon dioxide (CO2), a hydrothermal activation method was proposed to enhance fly ash-supercritical CO2 mineralization. The study systematically investigated the mechanism through which hydrothermal activation parameters influenced the efficiency of fly ash-supercritical CO2 mineralization through a series of experimental reactions. The effects of hydrothermal activation temperature and time on mineralization efficiency were investigated macroscopically. The results indicated that the mineralization efficiency increased by 202.93 % when hydrothermally activated at 220 °C for 30 min. Furthermore, when the activation time was ≤10 min, 220 °C exhibited a significant effect on the mineralization efficiency. For activation time ≥20 min, mineralization efficiency exhibited high stability with increasing temperature. Subsequently, under 220 °C conditions, mineralization efficiency reached 18.79 % for 5 min and 21.69 % for 30 min, representing only a 15.43 % increase despite a six-fold increase in time. Microscopic analysis of the pore structure of hydrothermally activated fly ash indicated that pore parameters (volume, specific surface area, and volume change rate) exceeded those of original fly ash for pore diameters ≥9 nm, and the opposite was observed for pore diameters <9 nm. Additionally, compared with the pristine fly ash, the pore size and volume fraction of the mineralized fly ash macropores increased, while mesopores decreased, and small pores exhibited a slight decrease in volume fraction and size. This indicated that pores ≥9 nm were primarily affected by hydration expansion, while pores <9 nm were primarily affected by mineralization precipitation. The hydrothermal activation mineralization reaction predominantly affected medium and large pores ≥9 nm, exhibiting less effect on smaller pores.

Bipolar membrane electrodialysis for amine regeneration from amine chloride stream: Closing the amine utilization loop

The amine-based CO2 capture & mineral carbonation (CCMC) using alkaline slag emerges as a decarbonation means. However, being the most costly component in the process, amine is consumed in large quantity yet its regeneration is overlooked. Thus, to close the material utilization loop, this work proposed the bipolar membrane electrodialysis (BMED) technology for amine regeneration from its chloride streams. With customized BMED configurations, the recovery of two different amines(monoethanolamine (MEA) & 2-(Diethylamino)ethanol (DEAE)) was investigated respectively to reveal the separation mechanisms. This novel concept was firstly proved with a three-compartment configuration, where the cations (MEA+ or DEAE+) can pass through the cation exchange membrane and react with OH− generated by the bipolar membrane thus producing pure amine. The respective MEA and DEAE regeneration reached up to 95.1 % and 92.4 % within 10 h; while the yield of a useful byproduct 1.8 wt% HCl reached ∼ 71 %, which can be reused in CCMC. The results showed that the membrane played a key role: with standard anion exchange membrane (AEM), the Cl− transfer rate decreased with increasing feed concentration. Although the proton blocking AEM avoided H+ cross-over, the Cl− transfer was stable but exhibited up to 2.5-times lower transfer rate. Via a comprehensive parametric study, a modest current density (150 A/m2) was chosen to avoid significant energy penalty, corresponding to a power consumption of 10.3 kWh/(kg amine). Compared to the acid model, the base model of two-compartment configuration, had 2x higher amine yield and higher energy efficiency. This study revealed the performance-limiting factors in BMED, inspiring future design of efficient amine regeneration system for closed-loop CCMC process and contributing to sustainable processing towards carbon neutrality.

Simultaneous CO2 mineral sequestration and nickel separation from laterite leachate: Thermodynamic and experimental study

Global warming resulting from escalating CO2 emissions and rising nickel demand present dual challenges to the sustainable development. In this study, a process for simultaneous nickel separation and CO2 mineral sequestration was proposed by using the leachate derived from the process of roasting laterite with copperas followed by water leaching. From the thermodynamic study, it was found that nickel can dissolve in the leachate in the form of nickel-ammonium complexes, while magnesium precipitated as carbonates. Furthermore, Eh-pH (potential vs. pH) results demonstrated that the conditions for the formation of nickel-ammonium complexes closely resemble those for magnesium carbonates. Under optimized conditions with the initial solution pH of 10.8, CO32–/Mg molar ratio of 2, reaction temperature of 30 °C, and reaction time of 1 h; over 95 % of Mg and 100 % of Fe can be converted into carbonates or hydroxides, with no more than 1 % Ni loss. Higher pH and CO32–/Mg molar ratios, along with lower temperatures, facilitated the separation of nickel from the magnesium and iron. The phase and microstructure of the precipitates were significantly influenced by the reaction temperature. At 30 °C, the precipitation product was MgCO3·3H2O, exhibiting a microstructure resembling porous spherical flowers; whereas at 80 °C, the precipitated phase was Mg5(OH)2(CO3)4·4H2O, also displaying a microstructure akin to porous spherical flowers. Efficient separation of nickel and magnesium in NH3–(NH4)2CO3-H2O was achieved by leveraging their distinct reaction properties, simultaneously sequestering CO2. This process achieved the maximum selective Ni recovery and CO2emission reduction in one step.

Multi-field and multi-scale dynamic numerical modeling of supercritical CO2 and fly ash mineralization

Fly ash-CO2 mineralization technology can effectively control gas–solid waste emissions and improve the climate environment. However, rationally describing the evolution mechanism of the fly ash-supercritical CO2 mineralization reaction and accurately predicting the efficiency of the mineralization reaction are of great significance for improving and evaluating the supercritical CO2 mineralization sequestration capacity. Fly ash micro- and nanopore multi-scale effects are the key to influencing the supercritical CO2 seepage-mineralization reaction mechanism. None of the current theoretical models consider the pore multi-scale effects, thus the validity and accuracy of predicting and describing the evolutionary mechanism of supercritical CO2 mineralization rates and efficiencies are questionable. To address this scientific issue, a multi-scale continuous pore structure theoretical model was established based on the structural characteristics of fly ash micro- and nanopores. Additionally, a new model of supercritical CO2 multi-field and multi-scale dynamic mineralization theory was developed by considering parameters such as temperature, pressure, and humidity. The accuracy of the model was verified through the mineralization experiments. The new model effectively describes the dynamic evolution mechanism of supercritical CO2 mineralized fly ash. The effects of parameters such as temperature, pressure, water vapor diffusion coefficient, supercritical CO2 permeability, and pore multi-scale effect on the efficiency and mineralization rate were investigated through numerical simulation. The results showed the following: The mineralization efficiency exhibited a parabolic increase with temperature, with 72℃ being the turning point for the growth rate of mineralization efficiency, and 82℃ being the optimal effective temperature to promote the mineralization efficiency of supercritical CO2. A 3.5-fold increase in supercritical CO2 pressure changes the mineralization efficiency by a maximum of only 0.0493 %. Increasing the water vapor diffusion coefficient by 5 orders of magnitude changes the mineralization efficiency by only 8.3 %. The pore attenuation coefficient increases by 3 orders of magnitude, and the supercritical CO2 mineralization efficiency changes by a factor of 2.27. A model that does not account for pore multi-scale effects overestimates the fly ash- supercritical CO2 mineralization efficiency by a factor of 2.47 at a permeability of 3 × 10-10 m2. Therefore, neglecting the pore continuum multi-scale effect can lead to a serious overestimation of the mineralization efficiency of supercritical CO2.

Insight into solvent effects on growth morphology of MgCO3·3H2O in CO2 mineralization: Molecular dynamics simulations and DFT studies

Experimental evidence shows that the solvent effect greatly affects the MgCO3·3H2O morphology, but the atomic-level mechanism still remains elusive. In this study, the influence mechanisms of H2O and EtOH on MgCO3·3H2O morphology were systematically investigated by a combination of crystal growth experiments, molecular dynamics (MD) simulations, and DFT calculations. In contrast to the traditional DFT calculations, the interface microenvironments were introduced to the crystal growth model first. The modified attachment energy (MAE) model proved that (1 0 1), (-1 0 1), and (0 1 1) surfaces dominate MgCO3·3H2O morphology in vacuum, H2O, and EtOH/H2O environments. The solvent molecules created an extensive H-bond network at solid-liquid interfaces, which greatly changed diffusion and combination during the crystal growth process. Compared to the H2O molecule, EtOH only forms H-bonds through the hydroxyl group. The CH3- end created some hydrophobic cavities, which led to weaker H-bond connectivity. The weaker H-bond network facilitated the removal of water from the crystal surface and strengthened the connection between the growth unit and surface, while reducing the solvent effect on the growth unit, thereby accelerating crystal growth and changing morphology. This study reveals the significant role of solvent in the crystallization process of MgCO3·3H2O, providing valuable insights for controlling the MgCO3·3H2O morphology at the atomic level.

The origin and mineralization processes of the Dulenggou copper-cobalt deposit in the East Kunlun orogenic belt, western China

The East Kunlun region in western China stands out as an important polymetallic metallogenic belt hosting economically significant Au, Cu, Fe, Pb, Zn, Sn, Co, Ni and Cr resources. Within this belt lies the Dulenggou deposit, a notable Cu-Co deposit. Three cobalt minerals (cobaltine, siegenite, and glaucodot) and four nickel minerals (ullmannite, gerdorffite, violarite, and millerite) coexisting with chalcopyrite and pyrite were identified in the Dulenggou deposit. The mineralization of Co and Ni primarily occurs in the form of sulfarsenides (cobaltine and gersdorffite) rather than sulfides (siegenite and ullmannite). Sulfides are commonly associated with chalcopyrite, whereas sulfarsenides coexist with chalcopyrite occasionally within the host rocks. The presence of organic-rich surrounding sedimentary rocks reduces oxygen fugacity, and the increase in arsenic content may influence the paragenetic association of minerals. The sequence of mineral formation is Py0 (host rocks) → PyI + Ccp + Co-Ni minerals (the major mineralization stage) → PyII. The mineralization age of the Dulenggou deposit has been determined by in situ U–Pb dating of hydrothermal monazite in closely association with chalcopyrite and Co–Ni minerals, yielding an age of 467 ± 17 Ma. The δ34S values of sulfides (pyrite and chalcopyrite) from ores and host rocks range widely from 1.9 ‰ to 22.1 ‰. From Py0 to PyI to PyII to chalcopyrite, the δ34S values change from 17.6 ‰ to 22.1 ‰, from 9.1 ‰ to 14.6 ‰, from 1.9 ‰ to 7.7 ‰, and from 9.6 ‰ to 13.4 ‰, respectively. The positive δ34S values suggest that the primary sulfur source possibly originated from seawater and/or the host rocks. Based on the geological and geochemical characteristics, the Dulenggou copper-cobalt deposit is identified as a syngenetic sea floor sedimentary exhalative deposit.

Experimental Investigation of Amine Regeneration for Carbon Capture through CO2 Mineralization

Summary The most common method for point-source carbon capture involves the absorption of CO2 from flue gas by amine solutions. The CO2 is then stripped from the amine solution by desorption with steam or heat. While amine solvents exhibit high CO2 absorption efficiency, their desorption process consumes a substantial amount of energy. A more energy-efficient alternative for the regeneration of the amine can be done through a mineralization process. Past studies have shown the feasibility of mineralizing captured CO2 from amine solution using calcium oxide (CaO) or other CaO-containing industrial waste. This study aims to show experimentally the extent of mineralization over time in near-ambient conditions and develop a mechanistic model. Lab-scale experiments are conducted to determine the absorption characteristics of CO2 in monoethanolamine (MEA) solutions and the extent of mineralization. We observe that pH serves as an indicator for CO2 loading in amine solutions. At high concentrations of MEA, CO2 absorption efficiency is about 0.5 mol CO2/mol MEA. Under ambient pressure and a temperature of 40°C, CaO effectively mineralizes CO2 and regenerates MEA. The CaO initially reacts with water to produce calcium hydroxide (Ca(OH)2) and subsequently reacts with dissolved CO2, forming calcium carbonate (CaCO3). Both 13C nuclear magnetic resonance (NMR) and FTIR indicate that MEA can be regenerated with an efficiency close to 69 to 98%, by comparing the carbamate and bicarbonate peaks in the 13C NMR response. A model to describe the absorption and mineralization reaction is proposed using the PHREEQC software; the pH is matched within less than 3% error. This study demonstrates that CO2 desorption from MEA solutions can occur through mineralization, converting CO2 into carbonates at low pressure and temperature with CaO. This method has lower energy consumption and results in the most stable form of CO2, making it a safer sequestration strategy than supercritical CO2 storage in reservoirs.

Functional regulation of organic-inorganic mesh structures for complex CaCO3-based materials

Combining biological strategies with CO2 mineralization allows for the efficient synthesis of functional CaCO3-based material with remarkable performance and efficient carbon utilization. This study found an intriguing phenomenon of increased activation energy (Ea = 52.25 kJ/mol) in the carbonation reaction caused by the complexation between calcium and carboxyl. Complexation triggered by proton transfer was the mechanism for the formation of the highly polymerized structure of polyacrylic acid (PAA)-Ca. The calcium serves as a "bridge" that connects PAA molecules, creating a spatial net structure. The abundant specific surface area of PAA-Ca leads to a shift in the kinetics to a surface coverage model. Consequently, the use of PAA resulted in an efficient synthesis of the organic-inorganic hybrid material with a high purity of CaCO3 (> 97 %). These findings have significant implications for establishing the functional regulation and efficient co-production of CaCO3 in the CO2 mineralization process under mild environmental conditions.

Enhanced reactivity and CO2 mineralization of low-lime calcium silicate cement by incorporating nitric acid as an initial calcium leaching agent

This study proposed mixing HNO3 solution with low-lime calcium silicate cement (CSC) to enhance the CO2 capture and mechanical properties after CO2-curing by increasing Ca2+ leaching at the initial stage. To clarify the influences of HNO3 and the reaction mechanisms, various molar concentrations of HNO3 (0, 0.01, 0.05, 0.1, 0.2, 0.5, and 1.0 M) were homogenized with CSC using a liquid-to-solid ratio (L/S) of 0.4 and CO2-cured in a pressurized chamber for 24 h. The impact of HNO3 on the initial reaction kinetics, Ca2+ leaching, phase composition after curing, CO2 fixation capability, and mechanical performance were investigated. The findings revealed that the incorporation of HNO3 had a pronounced influence on the degree of reaction, CO2 fixation, and mechanical performance of CSC pastes. Nevertheless, the excessive incorporation of HNO3 had a notable adverse impact on the reaction.

CO2-brine interactions in anhydrite-rich rock: Implications for carbon mineralization and geo-storage

The utilization of subsurface geologic media for carbon capture and storage through mineralization has been recognized as a reliable approach. However, less attention has been given to anhydrite rock type for CO2 mineralization and storage. Anhydrite-rich rock formations, commonly found in various geological settings, have the potential to serve as natural carbon sinks through the mineralization of CO2. Therefore, this study aims to investigate the mechanisms and potential of anhydrite-CO2-brine interactions for carbon storage. The experimental approach involved exposing anhydrite-rich rock to supercritical CO2-brine environments under varying conditions of fluid composition. Mineral transformation of an outcrop anhydrite-rich rock sample in static reactor under subsurface conditions of elevated temperature (60 °C) and pressure (104 bar), in the absence and the presence of SrCl2 was conduct for a one-month period. Mineralogical and geochemical analyses, including, solution analyses, X-ray fluorescence, X-ray diffraction, micro-computed tomography, and mechanical properties were conducted to examine the changes in the composition and rock structure resulting from the interactions. The experimental reactions revealed that anhydrite undergoes mineral transformation upon exposure to supercritical CO2-saturated brine to form stable minerals including calcite, dolomite, magnesite, and strontianite, which contributes to the potential for long-term storage of CO2 in the subsurface geologic media. The efficiency and extent of carbon mineralization were found to be influenced by brine composition. These findings contribute to the understanding of the potential of these formations for carbon storage, opening avenues for further research and the development of effective carbon capture and storage strategies.

Transformation of sedimentary dissolved organic matter in electrokinetic remediation catalogued by FT-ICR mass spectrometry

In electrokinetic remediation (EKR), the sedimentary dissolved organic matter (DOM) could impede remediation by scavenging reactive species and generating unintended byproducts. Yet its transformation and mechanisms remained largely unknown. This study conducted molecular-level characterization of the water-extractable DOM (WEOM) in EKR using negative-ion electrospray ionization coupled to 21 tesla Fourier transform ion cyclotron resonance mass spectrometry (21 T FT-ICR MS). The results suggested that ∼55 % of the ∼7,000 WEOM compounds identified were reactive, and EKR lowered their diversity, molecular weight distribution, and double-bond equivalent (DBE) through a combination of electrochemical and microbial redox reactions. Heteroatom-containing WEOM (CHON and CHOS) were abundant (∼ 35% of the total WEOM), with CHOS generally being more reactive than CHON. Low electric potential (1 V/cm) promoted the growth of dealkylation and desulfurization bacteria, and led to anodic CO2 mineralization, anodic cleavage of -SO and -SO3, and cathodic cleavage of -SH2; high electric potential (2 V/cm) only enriched desulfurization bacteria, and differently, led to anodic oxygenation and cathodic hydrogenation of unsaturated and phenolic compounds, in addition to cathodic cleavage of -SH2. The long-term impact of these changes on soil quality and nitrogen-sulfur-carbon flux may be need to studied to identify unknown risks and new applications of EKR.

Zinc-based organophyllosilicate nanosheets as novel carbonic anhydrase-like nanozyme for efficient CO2 fixation

The unparalleled catalytic activity of carbonic anhydrases (CAs) towards CO2 hydrolysis can potentially contribute to carbon capture, utilization, and storage technology aimed at global decarbonization; however, the high cost and low stability of CAs significantly limit their practical applications. Recently, the development of robust and effective nanozymes with CA-mimicking activity has been proposed as a promising solution to this challenge. Herein, a novel zinc-based organophyllosilicate (ZnAC) nanozyme with CA-like catalytic activity was synthesized by a facile one-pot sol–gel method for the first time, leading to a Zn-O coordination structure that mimicked the catalytic center fragments of natural CAs, with surface amino groups acting as the affinity sites and proton shuttles. The synergistic effect of the two components on the open surface of the layered structure resulted in excellent CA-like activity with a Michaelis–Menten constant (Km) of 4.071 mM, maximum velocity (Vmax) of 0.220 mM/s, and turnover number (kcat) of 11.213 /s at 25 °C and pH=7.5, which were superior to those of most previously reported CA-like nanozymes. The catalytic performance of ZnAC significantly improved with increasing pH and temperature; furthermore, ZnAC exhibited excellent stability, maintaining high catalytic activity after the exposure to extreme temperatures or pH values, eight reaction cycles, and 30 d of storage. Additionally, ZnAC significantly increased the rate of CO2 hydration and the extent of CO2 mineralization and precipitation. This work proposes a new strategy for designing and constructing efficient CA-like nanozymes, providing valuable insights into the structure–activity relationship and new perspectives for the implementation of CO2 fixation.

Enhanced photocatalytic degradation of toluene on surface C- and CN-modified TiO2 microspheres

Surface modified TiO2 materials are widely used in photocatalytic environmental purification processes. The employment of solution might exert a discernible influence on the catalyst. In this study, we incorporated tetrahydrofuran (THF) and pyrrolidine (PY) during the hydrolysis of titanium butoxide (TBOT) to modify the surface of TiO2, successfully synthesizing surface C-modified TiO2 (THF-TiO2) and surface CN-modified TiO2 (PY-TiO2) catalysts. The assistance of THF and PY not only reduced agglomeration, but also increased the specific surface area of both catalysts, leading to the exposure of more active sites in TiO2 during the photocatalytic degradation of toluene. When compared to the unsatisfactory degradation of toluene (80%) and CO2 mineralization efficiencies (40–45 %) observed using unmodified TiO2, the synthesized THF-50-TiO2 and PY-1-TiO2 microspheres demonstrated enhanced toluene degradation efficiency to 100 % and 99.8 %, respectively, and improved mineralization efficiencies to 76 % and 80 % after 120 min of ultraviolet irradiation. The experimental data and characterization results indicate that the surface-modified carbon species in THF-50-TiO2 facilitate the acceleration of electron-hole pair separation and suppress recombination. In contrast, partial nitrogen species introduced into the surface lattice of PY-1-TiO2 narrow its band gap and induce a visible light response. Overall, this study provides two methods to modify the surface of TiO2, which can be applied to prepare outstanding photocatalysts for possible application in the degradation of volatile organic compounds (VOCs) present in the air. Furthermore, it has been confirmed that solution have a significant impact on the catalyst.

Acceleration of Iron-Rich Olivine CO2 Mineral Carbonation and Utilization for Simultaneous Critical Nickel and Cobalt Recovery

CO2 mineral carbonation is an important method to sequester carbon dioxide (CO2) in the form of stable mineral carbonates for permanent storage. The slow kinetics of carbonation, especially for iron-rich olivine, is the major challenge for potential application. This work proposes methods to accelerate the mineral carbonation process of different materials in the general mineral grouping of divalent metals–olivine for simultaneous nickel and cobalt recovery. It is found that nickel-olivine is facile for mineral carbonation compared to ferrous and magnesium olivine. Ferrous olivine is the most difficult form of olivine to carbonate as illustrated in both thermodynamics and experimental test results. The increase in iron content in olivine inhibits the CO2 mineral carbonation process by forming an iron-silica-rich passivation interlayer. The use of a reducing gas or reagent can enhance the mineral carbonation of olivine probably through hindering oxidation of Fe(Ⅱ). The addition of sodium nitrilotriacetate (NTA) as a metal complexing agent is much more efficient for the acceleration than usage of a reducing atmosphere. The combination of sodium bicarbonate/CO2 gas supply and NTA can enhance the diffusion of all divalent metal ions from the reacting olivine surface, thereby limiting the formation of the passivation interlayer. Meanwhile, highly selective nickel and cobalt leaching can be simultaneously achieved along with the CO2 mineral carbonation, 94% nickel, and 92% cobalt leaching as well as 47% mineral carbonation versus only 10% iron and 1% magnesium leached in 2 h. This work provides a novel direction to achieve critical metals recovery with accelerated mineral carbonation process.

High-efficiency metal-free CO2 mineralization battery using organic redox catalysts

CO2 batteries offer a promising avenue for mitigating CO2 emissions and conversion, but encounter challenges such as high costs, dendrite, corrosion, flooding and slow kinetics stemming from the use of metal electrodes. CO2 mineralization is thermodynamically favorable (ΔGCO2), presenting an opportunity for processing solid waste and reducing CO2 emissions while potentially producing energy. However, the lack of direct electron transfer in the CO2 mineralization reaction hinders the direct generation of electrical energy. Here, we propose an organic CO2 mineralization battery (OCMB) without using metal, which efficiently harnesses CO2 to mineralize solid waste carbide slag, maximizing the recovery of mineralization reaction energy to generate electricity and produce carbonate products, without requiring renewable electricity charging. We employ a high-solubility, stable under strong alkaline conditions, and fast kinetics organic phenazine derivative—DSPZ as the electron and proton carrier, which facilitates the conversion of ΔpH between electrodes by interacting with alkaline wastes and CO2 into electricity. Simultaneously, the OCMB undergoes regeneration cycles through mineralization reactions. The theoretical model predicted the open circuit voltage (OCV) and discharge behavior of OCMB, offering insights for improved battery engineering. We demonstrate an impressive peak power density exceeding 227.5 W/m2 for the OCMB, with an estimated electricity production of ∼ 178.03 kWh per ton of CO2 mineralization. This research underscores the potential integration of OCMBs into CO2 energy systems, waste treatment processes, and chemical production, offering both economic and environmental benefits.

Enhancing coal gangue aggregates with fly ash-cement slurry: Synergistic effects of CO2 mineralization on physical and mechanical properties

The application of coal gangue in construction materials faces challenges due to its inherent structural looseness, elevated porosity, and high carbon content. This study encapsulated coal gangue aggregates (CGAs) with a fly ash-cement slurry, varying the content of fly ash (0 %, 10 %, 20 %, and 30 %) and maintaining a water-to-cement ratio of 0.35. These aggregates were subjected to a curing process within an environment containing a CO2 concentration of 20 %, 0.1 MPa pressure, 70 % humidity, and a temperature of 20°C. The study delved into examining how the combination of fly ash-cement slurry encapsulation and CO2 mineralization impacts the physical properties and microstructure of CGAs, focusing on understanding the influence and mechanism behind the synergistic effects. Findings reveal that following the encapsulation process using a fly ash-cement slurry, CGAs exhibit a higher apparent density, a reduced crushing value, but a notable increase in water absorption rate. Notably, treatment with 10 % fly ash-cement slurry and CO2 mineralization increased the apparent density by 3.85 %, reduced the crushing value by 39.57 %, and limited the increase in water absorption rate to 9.9 %. Additionally, the elastic modulus of the enhanced aggregates rose by 12.73 %. This can be attributed to the formation of a significant quantity of C-S-H gel and CaCO3 products as a result of the interplay between the encapsulated fly ash-cement slurry and CO2 mineralization. This process effectively occupied the voids within the coal gangue. Consequently, CO2 mineralization enhanced the interfacial transition zone between the slurry and coal gangue, ultimately leading to improved coal gangue's mechanical performance.

Global decarbonization potential of CO2 mineralization in concrete materials

CO2 mineralization products are often heralded as having outstanding potentials to reduce CO2-eq. emissions. However, these claims are generally undermined by incomplete consideration of the life cycle climate change impacts, material properties, supply and demand constraints, and economic viability of CO2 mineralization products. We investigate these factors in detail for ten concrete-related CO2 mineralization products to quantify their individual and global CO2-eq. emissions reduction potentials. Our results show that in 2020, 3.9 Gt of carbonatable solid materials were generated globally, with the dominant material being end-of-life cement paste in concrete and mortar (1.4 Gt y-1). All ten of the CO2 mineralization technologies investigated here reduce life cycle CO2-eq. emissions when used to substitute comparable conventional products. In 2020, the global CO2-eq. emissions reduction potential of economically competitive CO2 mineralization technologies was 0.39 Gt CO2-eq., i.e., 15% of that from cement production. This level of CO2-eq. emissions reduction is limited by the supply of end-of-life cement paste. The results also show that it is 2 to 5 times cheaper to reduce CO2-eq. emissions by producing cement from carbonated end-of-life cement paste than carbon capture and storage (CCS), demonstrating its superior decarbonization potential. On the other hand, it is currently much more expensive to reduce CO2-eq. emissions using some CO2 mineralization technologies, like carbonated normal weight aggregate production, than CCS. Technologies and policies that increase recovery of end-of-life cement paste from aged infrastructure are key to unlocking the potential of CO2 mineralization in reducing the CO2-eq. footprint of concrete materials.

Enforced CO2 mineralization in anhydrite-rich rocks

Carbon dioxide (CO2) emission is a major contributor to global warming and climate change. Consequently, there is an urgent need to decrease the concentration of CO2 in the atmosphere and develop reliable methods for its storage. Subsurface carbon mineralization is an effective solution to mitigate atmospheric CO2 emissions. This study is focused on investigating anhydrite–CO2–brine interactions as a means of carbon storage in anhydrite-rich reservoirs. To achieve this, we conducted experiments involving anhydrite-rich rock exposed to supercritical CO2-brine environments. Notably, we conducted a novel mineral transformation of an outcrop anhydrite-rich rock within a static reactor, replicating subsurface conditions of high temperature (333 K) and pressure (104 bar). These experiments were conducted over fifteen days, both in the absence and presence of BaCl2. A comprehensive suite of mineralogical, elemental, and geochemical analyses was employed, including X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, ion chromatographic (IC) analysis, and micro-computed tomography (micro-CT) assessments. These analyses allowed capturing the changes occurring in the rock's structure and composition due to the CO2-brine interactions. The outcomes revealed that anhydrite, when exposed to supercritical CO2-saturated brine, undergoes a significant mineral transformation. This mineral modification leads to the formation of stable minerals, including calcite, siderite, feldspar, and barite. Consequently, there was an observed increase in total carbon (TC) content of up to 177 % for the CO2-brine treatment and 266 % for the CO2-brine + BaCl2 treatment. These findings provide valuable insights into the potential of anhydrite-based CO2 storage mechanisms.

Investigation of an Indian Site with Mafic Rock for Carbon Sequestration.

The increasing extent of greenhouse gas emissions has necessitated the development of techniques for atmospheric carbon dioxide removal and storage. Various techniques are being explored for carbon storage including geological sequestration. The geological sequestration has various avenues such as depleted oil and gas reservoirs, coal-bed methane reservoirs, and mafic and ultramafic rocks. Different trapping mechanisms are in play in these subsurface storage systems. In these sequestration sites, the mafic and ultramafic rocks are best suited for long-term and effective sequestration as they comprise minerals, conducive for chemical alteration, forming stable carbonates. However, these sites often suffer from distinct disadvantages of injectivity issues due to their low permeability and porosity. This study investigates the potential of sequestration in the rock samples obtained from one such site located in India. The rock samples are first characterized using various techniques including X-ray fluorescence, X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopy (FESEM). The mineralogical characterization shows that the rock sample contains approximately 10% of diopside. The samples were put in the reactor chamber comprising CO2, which were then investigated using FESEM analysis. Additionally, a reservoir block simulation using commercial software was conducted with the representative minerals in the sample to evaluate the CO2 sequestration potential. The simulation result suggests the formation of magnesite which corresponds to a major part of CO2 mineral trapping. The reduced injectivity due to low porosity and permeability in this rock can be addressed using hydraulic fracturing. The geomechanical behavior of the rock sample for hydraulic fracturing is studied using the Brazilian disc test. The Monte Carlo-based uncertainty analysis was conducted using the tensile strength data of the sample. Results suggest that the most likely fracturing pressure is 2100 psi for this rock sample.