pH Swing Research Articles

Understanding the acid dissolution of Serpentinites (Tailings and waste rock) for use in indirect mineral carbonation

Solid carbonates can be formed by indirect mineral carbonation using the pH swing method for CO2 storage. It occurs at low temperatures and pressures in four stages: acid dissolution, purification, carbonation, and recovery. Although acid dissolution requires short reaction time that favors the extraction of reactive metals, lack of knowledge about the effects of temperature, acid concentration and particle size on metal extraction reveals that it is a critical stage of indirect mineral carbonation. In order to employ mining waste for indirect mineral carbonation, acid dissolution of serpentinites, tailings (SERP-GO) and waste rock (SERP-MG) were investigated, and their performances were compared. A Taguchi experiment design was used to assess the parameters that influence the acid dissolution process. Hydrochloric acid was used in acid dissolution for Mg and Fe extraction from both, SERP-GO and SERP-MG, and the process parameters (temperature, acid concentration, particle size and excess acid) were evaluated for 2 h of reaction. According to signal-to-noise ratio analysis of the Taguchi method, the optimized condition for Mg extraction of both samples was at 70 °C, 4 M HCl, 69 μm and twice the excess acid. The results indicated that of Mg and Fe extraction from de samples was more efficient for SERP-GO (71% and 85%) than SERP-MG (33% and 31%). Based on these findings, it was possible to have a better understanding of the factors affecting the dissolution of serpentinite tailings, to develop a more effective process for the use of mining waste in the indirect mineral carbonation process.

Electrochemically Mediated Direct CO2 Capture by a Stackable Bipolar Cell.

The unprecedented increase in atmospheric CO2 concentration calls for effective carbon capture technologies. With distributed sources contributing to about half of the overall emission, CO2 capture from the atmosphere [direct air capture, (DAC)] is more relevant than ever. Herein, an electrochemically mediated DAC system is reported which utilizes affinity of redox‐active quinone moieties towards CO2 molecules, and unlike incumbent chemisorption technologies which require temperature or pH swing, relies solely on the electrochemical voltage for CO2 capture and release. The design and operation of a DAC system is demonstrated with stackable bipolar cells using quinone chemistry. Specifically, poly(vinylanthraquinone) (PVAQ) negative electrode undergoes a two‐electron reduction reaction and reversibly complexes with CO2, leading to CO2 sequestration from the feed stream. The subsequent PVAQ oxidation, conversely, results in release of CO2. The performance of both small‐ and meso‐scale cells for DAC are evaluated with feed CO2 concentrations as low as 400 ppm (0.04 %), and energy consumption is demonstrated as low as 113 kJ per mole of CO2 captured. Notably, the bipolar cell construct is modular and expandable, equally suitable for small and large plants. Moving forward, this work presents a viable and highly customizable electrochemical method for DAC.

Simultaneous CO2 utilization and rare earth elements recovery by novel aqueous carbon mineralization of blast furnace slag

Carbon mineralization is recognized as a promising strategy for large-scale CO2 storage and utilization. To practically employ the carbon mineralization technology on a large scale, producing value-added solid carbonates is the key to reduce the overall costs. In this paper, we propose a novel concept not only for CO2 fixation but also recovery of rare earth elements (REEs) via the pH swing-assisted carbonation process. The blast furnace slag was selected as a feedstock, and NaOH and oxalic acid were adopted as the precipitation agent. The results revealed that the maximum REEs can be obtained in NaOH and oxalic acid-assisted pH swing carbonation and were 1986.1 and 9349.2 ppm, respectively. The CO2 storage capacities for NaOH and oxalic acid-assisted pH swing carbonation were also calculated to 107.38 and 117.89 kg CO2/ton-blast furnace slag, respectively, and both cases produced calcite of high purity. Conclusively, oxalic acid-assisted pH swing carbonation was advantageous over the case of NaOH for both simultaneous CO2 storage and REE recovery. These findings confirm that the pH swing carbonation process can contribute to building the waste-to resource supply chain as well as to improving CO2 storage and utilization.

Conceptual Evaluation of an Integrated Ccu Technology Based on Na-Salts Ph Swing Mineral Carbonation

Conceptual Evaluation of an Integrated Ccu Technology Based on Na-Salts Ph Swing Mineral Carbonation

Sustainable process for enhanced CO2 mineralization of calcium silicates using a recyclable chelating agent under alkaline conditions

This study explored a key challenge of aqueous indirect CO2 mineralization: the consumption of chemicals for a large pH swing between acidic and alkaline conditions and the production of waste fluid. Herein, we proposed and experimentally examined the technical feasibility of a sustainable process for enhanced CO2 mineralization using a new potentially recyclable alkaline solution of chelating agent [N,N-dicarboxymethyl glutamic acid (GLDA)] at near-room temperatures. This process comprising the following: enhanced Ca extraction from silicates with suppressed formation of silica-rich passivation layer via the combined actions of proton and chelating agent attacks at weakly alkaline conditions; Ca carbonation using sodium carbonate at high pH and temperature; and regeneration of the extraction solution (i.e., a decrease in pH and silicon removal) via CO2 gas dissolution. Ca extraction experiments using representative calcium silicate (CaSiO3) at various GLDA concentrations and initial pHs under 50 °C demonstrated the possibility of enhanced Ca extraction with almost all GLDA molecules combining with Ca (Ca/GLDA≈1) at an optimum condition (0.1 M GLDA and pH 8 in this study). This type of extraction is desirable as it contributes to an efficient Ca carbonation in addition to a decreased stability of the Ca-GLDA complex; indeed, most of the extracted Ca were carbonated to aragonite at 80 °C. Moreover, such extraction with the relatively low pH of 8 was found to be desirable for solution regeneration that involves pH adjustment (reduction) because of low silica solubility at lower pH. It was demonstrated that room-temperature CO2 bubbling removed almost all Si as amorphous SiO2, during which CO2 captured as NaHCO3 was also occurring. The recyclability of extraction solution was also demonstrated in this paper. This study encourages further extensive studies to optimize reaction conditions, particularly for using alkaline solid wastes, to make the process both technically and economically feasible.

Sustainable Coproduction of Two Disinfectants via Hydroxide-Balanced Modular Electrochemical Synthesis Using a Redox Reservoir.

Challenges posed by the sacrificial auxiliary reactions and expensive ion-exchange membranes in conventional electrosynthesis necessitate developing new electrochemical processes to enable efficient and sustainable distributed electrochemical manufacturing. Modular electrochemical synthesis (ModES) using a redox reservoir (RR) offers a promising membrane-free approach to improve energy efficiency and reduce waste through the pairing of multiple independent oxidative and reductive half-reactions; however, undesired ion-imbalance and induced pH changes in the existing ModES process limit sustained production. Here we present Ni(OH)2 as a heterogeneous RR that can selectively store and transport the hydroxide ions involved in the target half-reactions by reversible conversion with NiOOH to enable an ion-balanced ModES of two common disinfectants, hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO). This hydroxide-balanced ModES realizes stable operation without appreciable pH swing to accumulate practically useful concentrations of H2O2 and NaClO up to 251 and 481 ppm, respectively. These results illustrate additional design principles for electrosynthesis without sacrificial auxiliary reactions and the need for ion-selective RRs for modular electrochemical manufacturing.

(Invited) Toward Understanding Work Inputs for pH Swing-Based Electrochemical CO2 Separation

Large-scale CO2 separation and concentration from point sources, seawater and the atmosphere can play key roles in mitigating climate change and promoting the conversion of CO2 into chemical fuels and high-value products. Electrochemical CO2 separation processes have the potential to be more cost-effective than incumbent thermal (e.g. amine-based) analogues if they use inexpensive active materials and are sufficiently energy-efficient. Understanding the various thermodynamic and kinetic factors that contribute to the net electrical work consumed per unit of concentrated CO2 is therefore a critical step in developing practical systems.We discuss a method for electrochemical CO2 separation based on a pH swing cycle driven by redox reactions involving species capable of proton-coupled electron transfer (PCET). Electrochemical reduction of these species results in the formation of alkaline solution, into which may be CO2 is absorbed; subsequent electrochemical oxidation of the reduced molecules results in acidification of the solution, triggering the release of pure CO2 gas. This method is attractive for its operational simplicity, and because it can be driven by a wide range of aqueous-soluble or electrode-conjugated PCET-active reactants. Thermodynamic analysis and an experimental implementation of this idea in an electrochemical flow cell demonstrate that the net electrical work input per unit of separated CO2 can be low (< 100 kJ/molCO2). However, this work input comprises coupled kinetic and exergy losses that are highly sensitive to the cell’s electrochemical properties and its manner of operation. We describe how zero-dimensional modeling can play a role in rationalizing the various contributions to the work input, and thus promoting the development of energy-efficient systems which are capable of high throughput CO2 separation.

Purification of landfill gas by extracted calcium ions from municipal solid waste incineration fly ash

This study proposes the utilization of CO2 based on the purification of landfill gas (LFG). The process included absorption of CO2 from LFG using monoethanolamine (MEA) absorbent, extraction of calcium ions from municipal solid waste incineration (MSWI) fly ash using various acids, and formation of calcium carbonate using the extracted calcium ions. During LFG purification, the concentration of CH4 in the gas after absorption was time dependent. The pH swing method was used for the extraction of calcium ions and comprised three phases: calcium ion leaching from MSWI fly ash phase, removal of cations from the supernatant, and calcium ion recovery. Hydrochloric and nitric acids, known as strong acids, and citric, acetic, and formic acids, which are weak acids, were used as extraction agents. Hydrochloric acid, nitric acid, acetic acid, and formic acid showed significant calcium ion recovery rates of 99.32%, 99.18%, 98.35%, and 97.99%, respectively, whereas citric acid showed a relatively low recovery rate of 82.82%. The extracted calcium ions were converted into calcium carbonate by reacting with ionic CO2 in the saturated MEA. The calcium carbonate formed showed different crystal structures based on the extraction agent used: aragonite for hydrochloric acid and nitric acid, amorphous CaCO3 for citric acid, vaterite for acetic acid, and calcite for formic acid. The results of this study can be applied to various CO2 utilization processes based on LFG and MSWI fly ash.

CO2 Absorption Using Hollow Fiber Membrane Contactors: Introducing pH Swing Absorption (pHSA) to Overcome Purity Limitation.

Recently, membrane contactors have gained more popularity in the field of CO2 removal; however, achieving high purity and competitive recovery for poor soluble gas (H2, N2, or CH4) remains elusive. Hence, a novel process for CO2 removal from a mixture of gases using hollow fiber membrane contactors is investigated theoretically and experimentally. A theoretical model is constructed to show that the dissolved residual CO2 hinders the capacity of the absorbent when it is regenerated. This model, backed up by experimental investigation, proves that achieving a purity > 99% without consuming excessive chemicals or energy remains challenging in a closed-loop system. As a solution, a novel strategy is proposed: the pH Swing Absorption which consists of manipulating the acido–basic equilibrium of CO2 in the absorption and desorption stages by injecting moderate acid and base amount. It aims at decreasing CO2 residual content in the regenerated absorbent, by converting CO2 into its ionic counterparts ( or ) before absorption and improving CO2 degassing before desorption. Therefore, this strategy unlocks the theoretical limitation due to equilibrium with CO2 residual content in the absorbent and increases considerably the maximum achievable purity. Results also show the dependency of the performance on operating conditions such as total gas pressure and liquid flowrate. For N2/CO2 mixture, this process achieved a nitrogen purity of 99.97% with a N2 recovery rate of 94.13%. Similarly, for H2/CO2 mixture, a maximum H2 purity of 99.96% and recovery rate of 93.96% was obtained using this process. Moreover, the proposed patented process could potentially reduce energy or chemicals consumption.

Graphene Oxide as a Pb(II) Separation Medium: Has Part of the Story Been Overlooked?

A key problem associated with the design of graphene oxide (GO) materials and their tuning for nanoscale separations is how specific functional groups influence the competitive adsorption of solvated ions and water at liquid/graphene interfaces. Computation accompanied by experiment shows that OH and COOH exert an influence on water adsorption properties stronger than that of O and H functional groups. The COO– anions, following COOH deprotonation, stabilize Pb(II) through strong electrostatic interactions. This suggests that, among the functional groups under study, COOH offers the best Pb(II) adsorption capacity and the ability to regenerate the sorbent through a pH swing. In line with computation, striking experimental observations revealed that a substantial increase in Pb(II) adsorption occurs with increasing pH. Our findings provide a systematic framework for controlled design and implementation of regenerable C-based sorbents used in separations and desalination.

Advanced pseudopolymorph control of magnesium carbonates using structural properties of amines for CO2 utilization based on post-treatment of desalinated brine

Herein, we proposed a novel method for controlling magnesium carbonate pseudopolymorphs as part of the development of post-treatment technology for desalinated brine and CO2 from industrial plants. Mg(OH)2 was separated from reject brine using the pH swing method, and CO2 delivery into Mg(OH)2 was conducted by amine type CO2 carriers, including alkanolamine, alkylamine, and multi-amines with numerous amino groups, by utilizing the effects of their structural properties on pseudopolymorph control. The products formed by reaction between Mg(OH)2 and CO2-saturated amine carriers were analyzed by X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy for verification of crystal properties and thermogravimetry for purity analysis. The results demonstrated that through use of appropriate amine type CO2 carriers, particular magnesium carbonates can be formed. In conclusion, we proposed a novel process for pseudopolymorph control of magnesium carbonates without the need for excessive changes in reaction conditions and additional transformation inhibitors. With further optimization for scale-up and the process design of a carbon capture and utilization (CCU) plant, the proposed method can contribute to the commercialization of CCU processes where particular types of magnesium carbonates are targeted. Further, post-treatment of desalinated brine, efficient mitigation and utilization of CO2 will be achieved simultaneously.

CO2 utilization in built environment via the PCO2 swing carbonation of alkaline solid wastes with different mineralogy.

Carbon mineralization to solid carbonates is one of the reaction pathways that can not only utilize captured CO2 but also potentially store it in the long term. In this study, the dissolution and carbonation behaviors of alkaline solid wastes (i.e., waste concrete) was investigated. Concrete is one of the main contributors to a large carbon emission in the built environment. Thus, the upcycling of waste concrete via CO2 utilization has multifaceted environmental benefits including CO2 emission reduction, waste management and reduced mining. Unlike natural silicate minerals such as olivine and serpentine, alkaline solid wastes including waste concrete are highly reactive, and thus, their dissolution and carbonation behaviors vary significantly. Here, both conventional acid (e.g., hydrochloric acid) and less studied carbonic acid (i.e., CO2 saturated water) solvent systems were explored to extract Ca from concrete. Non-stoichiometric dissolution behaviors between Ca and Si were confirmed under far-from-equilibrium conditions (0.1 wt% slurry density), and the re-precipitation of the extracted Si was observed at near-equilibrium conditions (5 wt% slurry density), when the Ca extraction was performed at a controlled pH of 3. These experiments, with a wide range of slurry densities, provided valuable insight into Si re-precipitation phenomena and its effect on the mass transfer limitation during concrete dissolution. Next, the use of the partial pressure of CO2 for the pH swing carbon mineralization process was investigated for concrete, and the results were compared to those of Mg-bearing silicate minerals. In the PCO2 swing process, the extraction of Ca was significantly limited by the precipitation of the carbonate phase (i.e., calcite), since CO2 bubbling could not provide a low enough pH condition for concrete-water-CO2 systems. Thus, this study showed that the two-step carbon mineralization via PCO2 swing, that has been developed for Mg-bearing silicate minerals, may not be viable for highly reactive Ca-bearing silicate materials (e.g., concrete). The precipitated calcium carbonate (PCC) derived from waste concrete via a pH swing process showed very promising results with a high CO2 utilization potential as an upcycled construction material.

PH swing adsorption process for ambient carbon dioxide capture using activated carbon black adsorbents and immobilized carbonic anhydrase biocatalysts

Adsorbent-based carbon capture is only feasible if adsorption-desorption cycles are both fully regenerating and efficient. This work proposes a regenerative pH swing process and a pH swing regenerative adsorbent that are inspired by natural CO2 conversion by carbonic anhydrase biocatalysts found in mammalian red blood cells. The main objective is to develop, test and analyze a synthetic pH Swing Adsorption (pHSA) system as well as a pHSA compatible solid adsorbent to capture CO2 from a simulated ambient air gas stream. The lead developed adsorbent is a carbon black co-activated with potassium carbonate and nitrogenous copolymer that is impregnated with immobilized bovine carbonic anhydrase and thereby deemed “BCA/KN-CB”. BCA/KN-CB has preliminarily demonstrated both competitive CO2 adsorption capacity and limited regenerative ability under experimental pHSA conditions. In addition, BCA-based adsorbents achieved higher adsorption capacities than non-BCA adsorbent counterparts. The BCA/KN-CB adsorbent displayed both large point of zero charge (PZC) swings and regenerative stability. The proposed pHSA system requires essentially zero energy expenditure to achieve intended environments for capture and regeneration. With 1 kg of adsorbent, pHSA has the ability to capture 1 kg CO2 in less than 4 h of cycling. The tested pHSA adsorbent can also capture more than 96% of total CO2 in a given raw gas stream flowing through the capture chamber. This proof-of-concept study of a pH swing adsorption/biocatalytic adsorbent system suggests the potential to effectively operate under ambient conditions and exhibit advantageous operational efficiencies to other high-profile CO2 capture systems.

Freezing Time Prediction of Biologic Formulated Drug Substance Using the Plank Model.

The freezing of biologics has been widely studied from the physical chemistry point of view, for instance in terms of cryo-concentration, excipient crystallization, pH swing, potential protein denaturation, etc. In contrast, considerations on the processing aspects are very limited. For instance, the impact of freezer temperature, container size, freezer load, and freeze chilling capacity on the freezing rate in the most frequent case of freezing in a bottle have not been reported. In this study, the freezing time of either water or buffer solution was measured in various processing conditions. Experimental trials were conducted using containers ranging from 1 to 20 L in two types of freezers: a normal freezer (-30°C set point) and an ultra freezer (-70°C set point). These trials showed that both the container size and the freezer load influenced the freezing times. The current study demonstrated that the use of the well-established Plank model for freezing, coupled with freezer performance characterization, allows the description of the actual freezing kinetics in a very simple and accurate manner. The kinetics can then be modeled to accurately predict both the actual freezer temperature (possibly above the set point) and the freezing time based on freezer load.

Polarization-Induced Local pH Swing Promotes Pd-Catalyzed CO2 Hydrogenation.

Electrochemical polarization can dramatically promote the rate of concurrent nonfaradaic catalytic reactions, but the mechanistic basis for these promotion effects at solid-liquid interfaces remains poorly understood. Herein, we establish a mechanistic framework for nonfaradaic promotion in aqueous media that operates via a local pH swing induced by a concurrent faradaic reaction. As a model system, we examined the kinetics of nonfaradaic Pd-catalyzed CO2 hydrogenation to formate and find that the reaction can be promoted by a combination of high alkalinity and high CO2 concentration. In bulk electrolyte, alkalinity and CO2 concentration are inversely correlated to each other as set by the CO2/bicarbonate equilibrium. We show that this impasse can be overcome by using electrical polarization to generate a nonequilibrium local environment that has both high alkalinity and high CO2 concentration. We find that this local pH swing promotes the rate of nonfaradaic CO2 hydrogenation to formate by nearly 3 orders of magnitude at modest potential bias. The work establishes a rigorous mechanistic model of nonfaradaic promotion in aqueous media and provides a basis for enhancing hydrogenation catalysis under mild conditions via electrical polarization.

Low-Energy Electrochemical Carbon Dioxide Capture Based on a Biological Redox Proton Carrier

Summary Carbon capture and storage, in which CO2 is selectively removed and sequestrated from flue gas, is a promising strategy to mitigate CO2 emissions and global warming. Conventionally, CO2 capture involves an energy-consuming absorbent regeneration step by thermal decomposition (2.0–4.0 GJ ton−1 CO2), which accounts for the majority (60%–70%) of the total cost. Here, we propose an alternative electrochemical cycle to capture CO2 in an aqueous alkaline solution, facilitated by the pH swing effect from a proton-coupled electron transfer redox reaction of a biological proton carrier, riboflavin 5′-monophosphate sodium salt hydrate (FMN/FMNH2). Under lab conditions, an electrolysis cell implementing the FMN proton carrier demonstrates a high energy efficiency, with only 9.8 kJ mol−1 CO2 captured, which is much lower than traditional approaches using a monoethanolamine absorbent (2.0–4.0 GJ ton−1 CO2, 88–176 kJ mol−1 CO2). Thus, this system may contribute toward lowering the cost of CO2 capture.

Synergistic H+/Zn2+ dual ion insertion mechanism in high-capacity and ultra-stable hydrated VO2 cathode for aqueous Zn-ion batteries

Rechargeable aqueous zinc ion batteries (ZIB) with near-neutral electrolytes are a promising candidate for stationary energy storage owing to their high-energy-density, high-safety, low-cost and environmental-friendliness. However, the development of ZIBs is currently hindered by the lack of high-performance cathode materials and a good understanding of the true ionic storage mechanism in cathodes. Herein, using a promising ZIB cathode, hydrated VO2 (denoted as H-VO2), as a model material, we carried out a systematic experimental and theoretical work to elucidate the ionic storage mechanisms. We show strong evidence that H+ and Zn2+ are synergistically involved in the ionic storage in H-VO2. The H+-insertion/extraction, which leads to a pH swing of the electrolyte, can be viewed as an indirect Zn2+-storage through a reversible precipitation/dissolution of Zn(OH)2 on the surface of H-VO2 cathode. The first-principles DFT calculations further reveal that H+ and Zn2+ have their own favorable insertion sites and migration pathways, but H+-insertion predominates in the initial discharge stage whereas Zn2+-insertion controls in the late discharge stage. Because of the synergetic H+/Zn2+ co-insertion, H-VO2-based ZIB exhibits a high capacity and stability at both low and high rates, e.g. 410 and 200 ​mAh g-1, 88% and 70% retention rate for 200 (~1500 ​h) and 3000 cycles (~215 ​h) at 0.1 and 5.0 ​A ​g-1, respectively. The new fundamental insights gained from this study deepen the understanding of aqueous Zn-ion battery chemistry for future development of advanced ZIB cathodes.

A Review of CO2 Storage in View of Safety and Cost-Effectiveness

The emissions of greenhouse gases, especially CO2, have been identified as the main contributor for global warming and climate change. Carbon capture and storage (CCS) is considered to be the most promising strategy to mitigate the anthropogenic CO2 emissions. This review aims to provide the latest developments of CO2 storage from the perspective of improving safety and economics. The mechanisms and strategies of CO2 storage, focusing on their characteristics and current status, are discussed firstly. In the second section, the strategies for assessing and ensuring the security of CO2 storage operations, including the risks assessment approach and monitoring technology associated with CO2 storage, are outlined. In addition, the engineering methods to accelerate CO2 dissolution and mineral carbonation for fixing the mobile CO2 are also compared within the second section. The third part focuses on the strategies for improving economics of CO2 storage operations, namely enhanced industrial production with CO2 storage to generate additional profit, and co-injection of CO2 with impurities to reduce the cost. Moreover, the role of multiple CCS technologies and their distribution on the mitigation of CO2 emissions in the future are summarized. This review demonstrates that CO2 storage in depleted oil and gas reservoirs could play an important role in reducing CO2 emission in the near future and CO2 storage in saline aquifers may make the biggest contribution due to its huge storage capacity. Comparing the various available strategies, CO2-enhanced oil recovery (CO2-EOR) operations are supposed to play the most important role for CO2 mitigation in the next few years, followed by CO2-enhanced gas recovery (CO2-EGR). The direct mineralization of flue gas by coal fly ash and the pH swing mineralization would be the most promising technology for the mineral sequestration of CO2. Furthermore, by accelerating the deployment of CCS projects on large scale, the government can also play its role in reducing the CO2 emissions.

Carbon utilization based on post-treatment of desalinated reject brine and effect of structural properties of amines for CaCO3 polymorphs control

This study proposed simultaneous disposal and utilization process of desalinated reject brine and CO2, or brine-based carbon capture and utilization (CCU). Using metal cations in desalinated reject brine, the feasibility of amines with different structural properties as crystallization inhibitors, morphology controller of calcium carbonate formation was investigated in this study. Ca2+ ions were separated from desalinated reject brine in a salt refining plant by using a pH swing method and used for CaCO3 formation. Through this process, disposal of the large amount of metal cations in the desalinated reject brine was achieved. CO2 was selectively captured by alkanolamine, alkylamine, and multi-amine CO2 carriers with numerous amino groups and carried into the separated Ca(OH)2 to generate CaCO3. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR) were used to investigate crystal shape and polymorph of the product. Additionally, thermogravimetric/derivative thermogravimetric analysis (TG/DTG) was used for purity analysis. The results demonstrated that crystallization inhibition depending on structural properties of amines was possible, leading to successful CaCO3 polymorph control. The results of this research can be applied to process where the industrial production of metal carbonates based on inorganic CCU and disposal of the desalinated reject brine were involved.

PH swing cycle for CO2capture electrochemically driven through proton-coupled electron transfer

This study analyzes the energetic cost of CO2 separation using a pH swing created by electrochemical redox reactions of organic molecules involving PCET in aqueous electrolyte, and compares the experimental energetic cost to other methods.