CO2 Gas Research Articles

Carbon cycle and climate feedbacks under CO2 and non-CO2 overshoot pathways

Abstract. Reducing emissions of non-carbon dioxide (CO2) greenhouse gases (GHGs), such as methane (CH4) and nitrous oxide (N2O), complements CO2 mitigation in limiting global warming. However, estimating carbon–climate feedback for these gases remains fraught with uncertainties, especially under overshoot scenarios. This study investigates the impact of CO2 and non-CO2 gases with nearly equal levels of effective radiative forcing on the climate and carbon cycle, using the Earth system model (ESM) IPSL-CM6A-LR. We first present a method to recalibrate methane and nitrous oxide concentrations to align with published radiative forcings, ensuring accurate model performance. Next, we carry out a series of idealised ramp-up and ramp-down concentration-driven experiments and show that, while the impacts of increasing and decreasing CO2 and non-CO2 gases on the surface climate are nearly equivalent (when their radiative forcing magnitudes are set to be the same), regional differences emerge. We further explore the carbon cycle feedbacks and demonstrate that they differ under CO2 and non-CO2 forcing. CO2 forcing leads to both carbon–climate and carbon–concentration feedbacks, whereas non-CO2 gases give rise to the carbon–climate feedback only. We introduce a framework, building on previous studies that addressed CO2 forcing, to separate the carbon–climate feedback into a temperature term and a temperature–CO2 cross-term. Our findings reveal that these feedback terms are comparable in magnitude for the global ocean. This underscores the importance of considering both terms in carbon cycle feedback framework and climate change mitigation strategies.

Flow and Corrosion Analysis of CO2 Injection Wells: A Case Study of the Changqing Oilfield CCUS Project

In carbon dioxide capture, utilization and storage (CCUS) technology, CO2 flooding and storage is currently the most effective geological storage method and the flow law of the gas injection wellbore is the key to achieving safe and efficient CO2 injection. The existing wellbore flow model lacks research on the corrosion law. To this end, this paper established a gas injection wellbore flow-heat transfer-corrosion coupling model based on the actual situation of Huang 3 District of the CCUS Demonstration Base of Changqing Oilfield. The field measured data verification showed that the relative average error of the model in predicting pressure and temperature was less than 7.5% and the R2 of the predicted value and the measured value was greater than 0.99. The model was used for sensitivity analysis to evaluate the effects of different gas injection temperatures (15–55 °C), pressures (15–55 MPa), displacements (10–500 t/d) and CO2 contents (50–100%) on wellbore temperature, pressure and corrosion rate, and the wellbore flow law under different gas injection conditions was clarified. The results show that the wellbore temperature, pressure and corrosion rate are significantly affected by gas injection parameters. The wellbore temperature increases with the increase of gas injection temperature and decreases with the increase of gas injection displacement. The wellbore pressure is positively correlated with the gas injection pressure and CO2 content and the gas injection temperature and displacement have little effect on the pressure. The corrosion rate increases with the increase of gas injection temperature and displacement and decreases with the increase of gas injection pressure. In the wellbore, it shows a trend of first increasing and then decreasing with depth. The wellbore corrosion rate is affected by many factors. Reasonable adjustment of gas injection parameters (lowering temperature, increasing pressure, controlling displacement and CO2 content) can effectively slow down the wellbore corrosion loss. The research results can provide a theoretical basis for the optimization of gas injection system.

Mixed-Matrix Membrane-Based Piezoelectric CO2 Sensor with Self-Humidity Compensation.

Monitoring the CO2 concentration is crucial for assessing respiratory illnesses in humans and safeguarding the environment. The ongoing difficulty lies in achieving highly sensitive detection while also eliminating the interference caused by humidity. There is an unmet need for portable sensors with both high sensitivity and good moisture resistance to monitor CO2 in real time. In this study, a novel sensor capable of capturing the piezoelectric signals induced by CO2 gas is developed. A quartz crystal microbalance (QCM) coated with a mixed- matrix membrane of metal-organic framework (MOF)/polyether block amide (Pebax) is designed as a transducer to detect CO2 at room temperature. The change in the concentration of CO2 can be detected by the frequency shift of the QCM sensor. The sensor shows an ultrahigh sensitivity of 371.8 Hz to 1000 ppm of CO2 because of the abundant polar group and nitrogen Lewis basic groups. Furthermore, the implementation of a self-humidity compensation algorithm significantly enhances the accuracy and reliability of CO2 concentration monitoring by effectively addressing the issue of humidity interference. Our research underscores the immense potential of MOF/Pebax QCM sensors with self-humidity compensation ability in the field of CO2 gas monitoring.

Synergistic effect of ZnO-ZnFe2O4 heterostructures for enhanced surface catalytic activity in Cr(VI) reduction, green H2 generation and CO sensing: an experimental study supported by DFT.

Increasing energy demand is an indication of progress, but it necessitates careful management of environmental pollution for maintaining a healthy life and ensuring a better planet for future generations. Heterostructure material-based catalysts have emerged as a comprehensive solution to combat the diverse challenges related to energy and environment. Herein, an n-n-type ZnO-ZnFe2O4 heterostructure was synthesized via a simple reflux followed by a co-precipitation technique for the same. Detailed photocatalytic and gas sensing studies revealed that a 50% ZnO-50% ZnFe2O4-based sample (ZZF-11) showed the highest Cr(VI) degradation with a rate constant of ∼159 × 10-4 s-1, which was ∼23 times higher than that of pristine ZnO and 6.4 times higher than that of pristine ZnFe2O4. Additionally, the ZZF-11 sample produced ∼550 μmol g-1 of H2 within a 300 minute interval via a photocatalytic water-splitting reaction. The ZZF-11 sensor also showed a significantly high response to 1 ppm CO gas (S = 29.4%) compared to all other pure and composite samples. The formation of the heterostructure and transfer of charges through the interface played an important role here. The most possible mechanism for the enhanced surface catalytic performance of ZZF-11 was critically analysed by corroborating the experimental results with DFT results. This study demonstrates a unified pathway to enhance the various surface catalytic processes by tuning different parameters of the heterostructure material to simultaneously overcome environment- and energy-related issues.

Real‐Time Sensing Technology of Mixed Gas Concentrations Using Multiple Micromachined Thermal Conductivity Detectors

ABSTRACTThis paper presents a new method for fast simultaneous monitoring of individual gas concentrations in a gas mixture by using small micromachined sensors. The developed method uses output data from multiple micromachined thermal conductivity detectors of different sensitivities. We confirmed that the fabricated sensors can accurately determine the concentrations of each of three gases in a mixture. The prototype sensor module was miniaturized to less than 1/72th the size of conventional gas chromatography (GC) equipment. Demonstration tests were conducted in a CO2 electrolysis cell for CO2 capture and utilization technologies, and each gas concentration was successfully monitored 176 times faster than conventional GC could for a mixture of H2, CO2, and CO gases.

Reuse of spent lithium cobaltate as an efficient catalyst for the CO2 gasification of biochar

Reuse of spent lithium cobaltate as an efficient catalyst for the CO2 gasification of biochar

Imaging Mofette Structures in the Ohře Rift System, Czech Republic, Using Radio-Magnetotelluric Data

Abstract The pathways of fluids and mantle-originated carbon dioxide in the seismically active Ohře (Eger) Rift system appearing as mofettes at the surface are currently subject to investigation, especially by the International Continental Scientific Drilling Program “Drilling the Eger Rift”. If the aquifers show significant contrast in electrical resistivity to the host rocks, they can be investigated with geo-electromagnetic methods. However, imaging complex fluid and CO2 pathways in detail in near-surface structures is challenging, because, in contrast to the background stratigraphy, they are often oriented in near-vertical directions. Therefore, we aim to investigate how the shallow aquifer structures can be examined best with an inductive electromagnetic method. For this purpose, we collected radio-magnetotelluric data in the Hartoušov mofette field and evaluated them by two- and three-dimensional inversions. Data from a nearby magnetotelluric station, drill hole data, gas flux measurements and electrical resistivity tomography models were used to assess the reliability and robustness of our inversion results. We concluded that the near-surface fluid reservoirs are adequately depictable, while the migration paths of gaseous CO2 cannot be traced properly due to a lack of resistivity contrast. Our model analyses suggest that imaging the given geological setting with fluids and gases ascending in anastomosing pathways benefits from a fine-scale three-dimensional inversion approach because the fluids mostly appear as local conductive reservoir-like anomalies, which can be falsely projected onto the profiles during inversion in two dimensions. The resistivity models contribute with detailed images of the near-surface aquifers to the geodynamic model of the Ohře Rift.

Synthesis of EPB/TiO2 Activated Carbon Composite Using Microwaves Activation for Purification of Motor Vehicle Exhaust Emissions

The palm oil plantation industry generates waste besides palm oil products, including empty palm bunch (EPB). This research examines the emission reduction capabilities of motor vehicle exhaust gases using a composite of activated carbon from EPB-AC/TiO2. Surface morphology characterization of the composite is conducted using Brunauer-Emmett-Teller (BET) and Scanning Electron Microscope (SEM). EPB-AC exhibits an average reduction effectiveness of HC gas based on particle size (50, 100, 150, 200 mesh) sequentially at 34.49%, 37.43%, 39.98%, and 43.56%. The average effectiveness of EPB-AC in reducing CO gas sequentially is 70.29%, 71.30%, 72.86%, and 74%. For CO2 gas, EPB-AC has an average reduction sequentially at 52.6%, 54.25%, 56.52%, and 58.54%. On the other hand, the EPB-AC/TiO2 composite exhibits an average reduction effectiveness of HC gas based on particle size sequentially at 42.38%, 43.42%, 45.1%, and 46.57%. The average effectiveness of the EPB-AC/TiO2 composite in reducing CO gas sequentially is 71.24%, 73.52%, 75.54%, and 76.9%. For CO2 gas, the EPB-AC/TiO2 composite has an average reduction sequentially at 54.93%, 54.25%, 59.76%, and 63.05%. Therefore, the best reduction results occur at a particle size of 200 mesh.

Convenient preparation of inexpensive sandwich-type poly(vinylidene fluoride)/molecular sieve/ethyl cellulose mixed matrix membranes and their effective pre-exploration for the selective separation of CO2 in large-scale industrial utilization

Due to its high methane content, biogas is considered a potential replacement for natural gas as a clean and renewable energy source for future large-scale applications. In addition to CH4 (50–80%), biogas also includes CO2 (20–40%), N2 (0–5%), and other gases. Efficient capture and separation of CO2 not only enhances the calorific value of biogas but also aids in reducing greenhouse gas emissions. Utilizing membrane separation technology is an effective method for separating and capturing CO2 and N2. This technology is renowned for its controllability and efficiency. Here, a variety of ternary mixed matrix membranes consisting of poly(vinylidene fluoride)/molecular sieve/ethyl cellulose were successfully prepared using a simple layer-by-layer coating process. Among them, the porous polyvinylidene difluoride (PVDF) membrane serves as the bottom support layer, the molecular sieve (Titanate molecular sieve (TS-1) and Zeolite Socony Mobil-5 (ZSM-5)) acts as the middle selective layer, and ethyl cellulose (EC) forms the top fixed layer. These membrane materials were used in an attempt to efficiently separate CO2 from a CO2/CH4 gas mixture with a 1:1 ratio and a CO2/N2 gas mixture with a 1:1 ratio. It is encouraging to note that the PVDF/ZSM-5/EC mixed matrix membrane (with 10% ZSM-5), which is the most cost-effective among the ternary mixed matrix membranes, exhibited the best gas separation performance. For a mixture of CO2 and CH4 gases, the CO2 permeability was 891.23 Barrer, and the CO2/CH4 selectivity was 12.92. Its gas permselectivity exceeds the Robeson 2008 line. For the CO2 and N2 gas mixture, the CO2 permeability is 316.39 Barrer, and the CO2/N2 selectivity is 21.85. It exceeds the Robeson 1991 line for gas permselectivity. Although the PVDF/ZSM-5/EC mixed matrix membrane may not be highly effective in separating CO2 from a mixture of CO2 and N2 (in comparison to CO2/CH4 mixture gases), given the gas composition in biogas and natural gas, it is reasonable to conclude that our PVDF/ZSM-5/EC mixed matrix membrane is well-suited for the selective separation of CO2. This experiment is an important exploration for us to understand the transition of advanced membranes to practical applications. It lays a solid foundation for the production of PVDF/ZSM-5/EC ternary mixed matrix membranes at the lowest cost and for large-scale application in the field of biogas and natural gas purification, as well as greenhouse gas treatment from coal-fired power plants (CO2 selective separation).

Portable Solar-Integrated Open-Source Chemistry Lab for Water Treatment with Electrolysis

Harnessing solar energy offers a sustainable alternative for powering electrolysis for green hydrogen production as well as wastewater treatment. The high costs and logistical challenges of electrolysis have resulted in limited widespread investigation and implementation of electrochemical technologies on an industrial scale. To overcome these challenges, this study designs and tests a new approach to chemical experiments and wastewater treatment research using a portable standalone open-source solar photovoltaic (PV)-powered station that can be located onsite at a wastewater treatment plant with unreliable electrical power. The experimental system is equipped with an energy monitoring data acquisition system. In addition, sensors enable real-time monitoring of gases—CO, CO2, CH4, H2, H2S, and NH3—along with temperature, humidity, and volatile organic compounds, enhancing safety during electrochemical experiments on wastewater, which may release hazardous gases. SAMA software was used to evaluate energy-sharing scenarios under different grid-connected conditions, and the system can operate off the power grid for 98% of the year in Ontario, Canada. The complete system was tested utilizing a laboratory-scale electrolyzer (electrodes of SS316L, Duplex 2205, titanium grade II and graphite) with electrolyte solutions of potassium hydroxide, sulfuric acid, and secondary wastewater effluent. The electrolytic cell specifically developed for testing electrode materials and wastewater showed a Faraday efficiency up to 95% and an energy efficiency of 55% at STP, demonstrating the potential for use of this technology in future work.

Bayesian calibration of bubble size dynamics applied to CO2 gas fermenters

Bayesian calibration of bubble size dynamics applied to CO2 gas fermenters

Microalgae-based flue gas CO2 sequestration for cleaner environment and biofuel feedstock production: a review.

Anthropogenic CO2 emissions are the prime cause of global warming and climate change, promoting researchers to develop suitable technologies to reduce carbon footprints. Among various CO2 sequestration technologies, microalgal-based methods are found to be promising due to their easier operation, environmental benefits, and simpler equipment requirements. Microalgae-based carbon capture and storage (CCS) technology is essential for addressing challenges related to the use of industrial-emitted flue gases. This review focuses on the literature concerning the microalgal application for CO2 sequestration. It highlights the primary physiochemical parameters that affect microalgal-based CO2 biofixation, including light exposure, microalgal strain, temperature, inoculum size, pH levels, mass transfer, CO2 concentration, flow rate, cultivation system, and mixing mechanisms. Moreover, the inhibition effect of different flue gas components including NOx, SOx, and Hg on growth kinetics is discussed to enhance the capacity of microalgal-based CO2 biofixation, along with deliberated challenges and prospects for future development. Overall, the review indicated microalgal-based flue gas CO2 fixation rates range from 80mg L-1day-1 to over 578mg L-1day-1, primarily influenced by physiochemical parameters and flue gas composition. This article summarizes the mechanisms and stages of microalgal-based CO2 sequestration and provides a comprehensive review based on international interest in this green technology.

In-Situ Diagnostics of Multi-Thermal Fluid Injection Parameters Using Stray Radiation Suppression and Circular Cell-Enhanced Laser Absorption Spectroscopy.

Multithermal fluid (MTF) component ratios and injection parameters are critical inputs in offshore heavy oil development, such as injection adjustment and monitoring, productivity prediction, and generator combustion process optimization. We implement simultaneous in situ diagnostics of two emblematic injection parameters, the gas-water ratio (GWR) and noncondensable gases proportion (NCGP), in a pilot-scale environment. A system-level integration of a novel laser absorption spectroscopy multigas sensor system based on integrating stray radiation suppression and a circular cell-enhanced strategy is proposed. A structurally optimized extinction thread in front of a photodetector is designed to reduce the absorption signal distortion under the influence of high-temperature radiation. Meanwhile, we break the limitation of the internal dimensions of the injection tube on the long-path absorption of gas molecules and improve the absorbance signal SNR by 3.42-fold. The present work performed experimental tests using diesel as the primary fuel in a laboratory-scale MTF generation system. The results show that the measurement uncertainties for H2O/CO2 concentrations are maintained at ±6.34% and ±6.87%, respectively. The proportion of CO2 in noncondensable gas is comparable to field data, but the GWR of the simulation system at different injection temperatures is much higher than that of the field injection parameters. The measurement system demonstrates remarkable stability and rapid response, marking a significant milestone as the first reported instance of in situ diagnostics of MTF injection parameters conducted in a laboratory bench test.

Impact of gas composition, pressure, and temperature on interfacial Tension dynamics in CO₂-Enhanced oil recovery.

Climate change policies are driving the oil and gas industry to explore CO2 injection for carbon dioxide storage in reservoirs. In the United States, a substantial portion of oil production relies on CO2-enhanced-oil-recovery (CO2-EOR), demonstrating a growing interest in using CO2 to address various production challenges like condensate mitigation, pressure maintenance, and enhancing productivity in tight reservoirs. CO2 injection introduces gases like natural gas and N2, either pre-existing or as impurities in the injected CO2 gas. These gases alter the interaction of CO2 with the oil or condensate in the reservoir, with interfacial tension playing a crucial role in governing miscibility, mobilization, and phase distribution. Effectively implementing gas injection techniques requires a precise understanding of interfacial tension between injected gases and reservoir fluid under reservoir conditions. This study aims to evaluate the effects of oil composition, gas composition, pressure, and, temperature on interfacial tension and provides a comprehensive understanding of IFT dynamics for CO2-EOR implementation. The study utilizes the pendant drop analysis technique to assess the impact of pressure, temperature, and gas composition on crude oil and condensate interfacial tension. Measurements span a range of temperature (30-85 oC), pressure (0.7-7MPa), and mixture composition (CO2: N2 ratios of 90:10 and 10:90), including pure CO2 and N2 with crude oil and condensate. Accurate measurement of interfacial tension incorporates changes in oil and gas density as functions of pressure and temperature. Results show that interfacial tension is significantly influenced by pressure, temperature, and gas composition. It decreases with increasing pressure at constant temperature and gas composition for both crude oil and condensate. While temperature-induced reductions in interfacial tension occur, they are overshadowed by the more pronounced effect of pressure. Gas composition significantly affects system interfacial tension; an increase in CO2 mole fraction decreases it, while an increase in N2 mole fraction causes an upturn. Changes in CO2 mole fraction result in concave downward trends, whereas changes in N2 mole fraction lead to concave upward trends. These findings are crucial for understanding the interaction of injected gas with reservoir fluid and can be applied to model interfacial tension with hydrocarbon fluid. This study offers an in-depth understanding of interfacial tension dynamics in CO2-EOR, a process that is increasingly attracting global attention for CO2 utilization. The research stands out for its innovative experimentation and detailed analysis, which focus on evaluating the impact of individual parameters crucial for modeling. Additionally, it sheds light on the combined effects of these parameters, which are essential for practical field applications. This knowledge is instrumental in designing processes such as CO2-EOR and condensate banking, incorporating the effects of pressure, temperature, and gas composition at the reservoir scale.

Enhancing Utilization of Municipal Solid Waste Bottom Ash by the Stabilization of Heavy Metals

Waste-to-energy (WtE) is a key part of modern waste management. In the European Union, approximately 500 WtE plants process more than 100 million tons of waste yearly, while globally, more than 2700 plants handle over 500 million tons. Roughly 20% of the waste processed is bottom ash (BA). However, this ash can contain heavy metals in concentrations that may render it hazardous. This paper presents a study focusing on stabilizing municipal solid waste incineration BA using simple and industrially viable treatments. The Slovenian WtE plant operator wishes to install the stabilization process; thus, the samples obtained from the plant were treated (1) with a CO2 gas flow, (2) with water spraying, and (3) with a combination of water spraying and a CO2 gas flow under laboratory conditions. Thermodynamic calculations were applied to define potential reactions during the treatment processes in the temperature range from 0 to 100 °C and to define the equilibrium composition of the treated ash with additions of CO2 and water. The standard leaching test EN 12457-4 of treated ash shows a reduction of over 40% in barium concentration and over 30% in lead concentration in leachates.

Development of Reduce Graphene Oxide (rGO)/ Polypyrrole Composite towards Potential Application of CO2 Gas Sensor

Ppy and Ppy/rGO composites were synthesized using a one-step in-situ oxidation polymerization process. The synthesis involves incorporating reduced graphene oxide (rGO) into the Ppy matrix to improve its sensing properties. Composites were characterized using XRD and FTIR. Response time and the recovery time of sensors were estimated by the static response. The response time of pure Ppy substrate is found to be more than that of Ppy/rGO 10%. Recovery time of Ppy is more as compared to shorter recovery time of Ppy/rGO 10 % i.e 54s. As the recovery time of Ppy/rGO is very less, the active layer can be used as a potential CO2 sensor for carbon dioxide gas sensing and monitoring. Thus, study demonstrates the potential of using Ppy/rGO composites in practical gas-sensing devices, especially for detecting CO2. The enhanced performance attributed to the rGO doping makes it a valuable approach for improving sensor technologies.

Production of Highly Metalized Direct Reduced Iron (DRI) in Fluidized Bed by CO and H2: Determination of the Kinetic Triplet

Abstract In this study, calcined iron ore samples from Menteş, Türkiye were isothermally reduced in a laboratory-scale fluidized bed reactor using several blends of CO, H2, and N2 gases. The experiments were carried out at 3 temperatures (800 °C, 850 °C, and 900 °C), with 4 reductant concentrations (1:1:2, 0:1:3, 1:1:6, and 1:0:3 molar ratios for “CO:H2:N2,” respectively). Almost full metallization was achieved with the first gas composition at 800 °C and 850 °C. However, 900 °C tests exhibited the lowest reduction degrees for almost all reductant compositions due to the sintering of the particle surfaces. The results showed that the conversion of the ore was more sensitive to reductant concentration (especially to the H2 ratio in the mixture) than the temperature. The kinetic analysis revealed that the gaseous reduction of calcined Menteş iron ore in the fluidized bed can be represented by the “Two-Dimensional Diffusion, D2(α)” model and the process requires 19.73 kJ/mol activation energy (Ea). Thanks to the low Ea requirement and relatively high Fe2O3 content, calcined Menteş iron ore was evaluated as a proper raw material for DR applications.

Carboxylative cyclization of propargylamines with carbamate salts as a non–gaseous CO2 source via dual-activation by Ag salts

Abstract 2-Oxazolidinones were synthesized from propargylamines using carbamate salts as the CO2 source. Ag catalysts act as activators for both alkynes and carbamate salts. This system also functions with aliphatic amines containing two or more nitrogen atoms by preparing carbamate salts in situ even under ambient conditions.

A Comparative Study of Mineral Carbonation Using Seawater for CO2 Utilization: Magnesium‐Based System Versus Calcium‐Based System with Low Energy Input

Mineral carbonation is promising for CO2 utilization and sequestration via capturing CO2 into stable solid carbonates. However, the effectiveness and price of the solvents, as well as the energy consumption of CO2 purification and pressurization of industrial flue gas, are hindering the development of this technology. Therefore, this study integrates two important concepts of seawater utilization and direct use of CO2 gas without purification and pressurization, investigating the mineral carbonation using seawater as an alternative solvent with low energy input. Carbonation of magnesium‐ and calcium‐based systems is investigated, and the behaviors as well as mechanisms of using seawater and distilled water are compared. The kinetics, conversion progress of compounds, and carbonation behavior are determined. The CO2 uptake capacities of seawater carbonation are higher in the Mg‐based system (1.16 g‐CO2/g‐MgO) than in the Ca‐based system (0.68 g‐CO2/g‐CaO); however, most CO2 in the Mg‐based system is captured in the solution phase. Insights into reaction optimization are provided. The potential assessment of mineral carbonation using seawater is provided. This study aims to facilitate the development of CO2 utilization and provide opportunities for mineral carbonation using seawater, through applying various alkaline wastes containing Ca and Mg from diverse industries.

Limited reactivity of pyroxene and plagioclase in batch experiments with supercritical CO2 in the presence of NaCl and NaHCO3 in the context of CO2 sequestration via carbonation.

One-step high-pressure and high-temperature direct aqueous mineral carbonation of tailings derived from mining of Platinum Group Metals in South Africa requires a fundamental understanding of the reactivity of the most dominant mineral phases, i.e. pyroxene and plagioclase (66 wt. % and 12 wt. % of the bulk rock respectively) that are typically found in these tailings. The silicate minerals pyroxene and plagioclase were sampled from a pyroxenite footwall mined with the ore-bearing UG2 and from the Merensky Reefs outcropping in the eastern limb of the Bushveld Complex. These pyroxene and plagioclase grains were concentrated by gravity separation from the orthopyroxenite bulk rock and batch-reacted in a sodium chloride (NaCl) brine saturated with pure carbon dioxide (CO2) gas-only or seeded with sodium bicarbonate (NaHCO3; as an additional CO2 source) for 13days at 100°C and 10MPa. Pyroxene dissolved slightly but no weathering features were observed in plagioclase. Analyses of the filtrates obtained from the pyroxene sample in the absence of NaHCO3 showed an increased concentration of magnesium and calcium ions in the solution. However, they had also reached a cation saturation sealing. On the other hand, liquid samples from reactions where both CO2 gas and NaHCO3 were added to the solution exhibited a pronounced decrease in dissolved magnesium and calcium ions. XRD patterns of some of the post-reaction solids collected from the cation-depleted solution aliquots showed peaks of newly formed secondary magnesite and vermiculite. Moreover, the presence of magnesite was further confirmed by Raman shift analysis of the dried solid products. The formation of secondary magnesite was observed only in the experiments seeded with NaHCO3, specifically where the pre-reaction solid was pyroxene rich. Some of the resultant fluid chemistry was corroborated by the geochemical model that simulated the reaction parameters using the Geochemist Work Bench (GWB) software. Overall, the results indicate low pyroxene dissolution, which leads to limited carbonation. These findings suggest that the carbonation of PGM tailings may be constrained under the evaluated physicochemical conditions.