Bicarbonate Production Research Articles

Preservation of 34S-enriched sulfides in fossil sulfate-methane transition zones: new evidence from Miocene outcrops of the northern Apennines (Italy)

We provide new evidence of the preservation of 34S-enriched signals in methane seep-impacted sediments from two onshore Miocene outcrops located in the northern Apennines (Italy). Selected outcrops include methane-derived authigenic carbonates (MDAC) with δ13C composition between − 42.3 and − 18.2‰. MDACs contain chemosynthetic clams and abundant pyrite indicative of formation close to or within a shallow sulfate-methane transition zone (SMTZ). This study aims to evaluate the relative contributions of background organic matter mineralization and anaerobic oxidation of methane (AOM) to sulfate consumption and to gain insight into the transport process (i.e., diffusion, advection) controlling the depth of the SMTZ. Host sediments were investigated by CHN elemental analysis coupled with total sulfur (TS) and sulfur isotopic measurements on bulk samples. Total organic carbon (TOC) measurements reveal a consistent and low amount of organic carbon (TOC 0‰ and up to + 17.1‰), which is characteristic of sulfides precipitated in association with AOM. We propose that advection of methane-rich fluids was responsible for maintaining the shallow depth of the studied paleo-SMTZs. AOM at paleo-SMTZ positions in the investigated seep-impacted sediments resulted in excess bicarbonate and sulfide production, favoring solid-phase MDAC and iron sulfide precipitation.

Valorization of calcium carbonate-based solid wastes for the treatment of hydrogen sulfide in a semi-continuous reactor: Part II – Slurry bubble column pilot

This work is devoted to the removal of H2S from the gas phase using a suspension of calcium carbonate-based residues, recovered from the production of sodium bicarbonate. A 145 L (1.6 m height and 0.34 m internal diameter) slurry bubble column (SBC) reactor was used. The gaseous effluent was bed from the bottom and get out from the top of the column. The suspension (2–20 wt%) was recirculated from the bottom to the top by a pump. This created a counter-current regime between the gas phase (from the bottom to the top) and the liquid phase (from the top to the bottom) which favor the gas/liquid exchange inside the reactor. The influence of different parameters including solid concentration in the suspension (ws), recirculating rate of the suspension (QR), inlet gas flow rate (QG), and volume of the suspension, was investigated. The results obtained with this confirmed those at the lab scale, for both synthetic gaseous effluent (H2S diluted in compressed air) and real gaseous effluent emitted by the buffer tank of a wastewater treatment plant. This allows validating the technology before its deployment at the large industrial scale for H2S removal from the gas phase.

Recovery and concentration of ammonia from return liquor to promote enhanced CO2 absorption and simultaneous ammonium bicarbonate crystallisation during biogas upgrading in a hollow fibre membrane contactor

In this study, thermal desorption was developed to separate and concentrate ammonia from return liquor, for use as a chemical absorbent in biogas upgrading, providing process intensification and the production of crystalline ammonium bicarbonate as the final reaction product. Applying modest temperature (50 °C) in thermal desorption suppressed water vapour pressure and increased selective transport for ammonia from return liquor (0.11MNH3) yielding a concentrated condensate (up to 1.7MNH3). Rectification was modelled through second-stage thermal processing, where higher initial ammonia concentration from the first stage increased mass transfer and delivered a saturated ammonia solution (6.4MNH3), which was sufficient to provide chemically enhanced CO2 separation and the simultaneous initiation of ammonium bicarbonate crystallisation, in a hollow fibre membrane contactor. Condensate recovered from return liquor exhibited a reduction in surface tension. We propose this is due to the stratification of surface active agents at the air-liquid interface during primary-stage thermal desorption which carried over into the condensate, ‘salting’ out CO2 and lowering the kinetic trajectory of absorption. However, crystal induction (the onset of nucleation) was comparable in both synthetic and thermally recovered condensates, indicating the thermodynamics of crystallisation to be unaffected by the recovered condensate. The membrane was evidenced to promote heterogeneous primary nucleation, and the reduction in the recovered condensate surface tension was shown to exacerbate nucleation rate, due to the reduction in activation energy. X-ray diffraction of the crystals formed, showed the product to be ammonium bicarbonate, demonstrating that thermal desorption eliminates cation competition (e.g. Ca2+) to guarantee the formation of the preferred crystalline reaction product. This study identifies an important synergy between thermal desorption and membrane contactor technology that delivers biogas upgrading, ammonia removal from wastewater and resource recovery in a complimentary process.

Bacterial ι-carbonic anhydrase: a new active class of carbonic anhydrase identified in the genome of the Gram-negative bacterium Burkholderia territorii

The carbonic anhydrases (CAs, EC 4.2.1.1) catalyse a simple but physiologically crucial reversible reaction, the carbon dioxide hydration with the production of bicarbonate and protons. In the last years, and especially, to the rapid emergence of the bacterial antibiotic resistance that is occurring worldwide, the understanding of the function of bacterial CAs has increased significantly. Recently, a new CA-class (ι-CA) was discovered in the marine diatom T. pseudonana. It has been reported that bacterial genomes may contain genes with relevant homology to the diatom ι-class CA. Still, the catalytic activity of the enzyme encoded by the gene was not investigated. Thus, herein, for the first time, we cloned, expressed, and purified the recombinant bacterial ι-CA (acronym BteCAι) identified in the genome of Burkholderia territorii. The recombinant BteCAι resulted in a good catalyst for the hydration of CO2 to bicarbonate and protons, with a kcat of 3.0 × 105 s −1 and kcat/KM of 3.9 × 107 M −1 s −1, and is also sensitive to inhibition by the sulphonamide acetazolamide. Furthermore, with the aid of the protonography, it has been demonstrated that BteCAι can be present as a dimer. This result is corroborated by the construction of a molecular model of BteCAι, which showed that the enzyme is formed by two equivalent monomers having a structure similar to a butterfly.

Spatiotemporal Variability and Sources of DIC in Permafrost Catchments of the Yangtze River Source Region: Insights From Stable Carbon Isotope and Water Chemistry

AbstractRiverine dissolved inorganic carbon (DIC) exports play a central role in the regional and global carbon cycles. Here, we investigated the spatiotemporal variability and sources of DIC in eight catchments in the Yangtze River source region (YRSR) with variable permafrost coverage and seasonally thawed active layers. The YRSR catchments are DIC‐rich (averagely 25 mg C L−1) and export 3.51 g m−2 yr−1 of DIC. The seasonal changes of temperature, active layer, flow path, and discharge can alter DIC and stable carbon isotope of DIC (δ13C‐DIC). The most depleted δ13C‐DIC values were found in the thawed period, suggesting the soil‐respired CO2 during the active layer thaw period can promote bicarbonate production via H2CO3 weathering. Spatially, δ13C‐DIC values increased downstream, likely due to CO2 outgassing and changed permafrost coverage and runoff. We found that evaporite dissolution and silicate weathering in the seasonally thawed active layer contributed 44.2% and 30.9% of stream HCO3‐, respectively, while groundwater and rainwater contributed 16.7% and 7.3% of HCO3‐, respectively. Pure carbonate rock weathering played a negligible role in DIC production. These results were compatible with δ13C‐DIC source approximation results. Silicate weathering increased from initial thaw to thawed period, reflecting the active layer thaw and subsequent hydrology change impacts. Silicate weathering consumed 1.25 × 1010 mol of CO2 annually, while evaporite dissolution may produce CO2 and neutralize this CO2 sink. This study provides new understanding of the riverine DIC export processes of the YRSR. As permafrost degrades, the quantity, sources, and sinks of riverine DIC may also change spatiotemporally.

Effectiveness of Opuntia ficus indica L. inermis Seed Oil in the Protection and the Healing of Experimentally Induced Gastric Mucosa Ulcer.

Gastric ulcer is a painful lesion of the gastric mucosa which can be disabling, or even more very serious in the case of a perforation of the stomach and internal hemorrhage. Traditional pharmacopeias have shown the efficacy of various plant extracts in the treatment of this pathology. Some extracts from Opuntia ficus indica (OFI) have been proven to have medicinal therapeutic benefits. The aim of this study was to investigate the preventive and curative effects of OFI seed oil extracted by cold pressing on an ethanol-induced gastric ulcer model in rats. Gastroprotective activities of the oil were assessed as pretreatments prior to ethanol gavage of Wistar rats compared to reference drugs. Two oil dose effects were tested. Ulcer and gastric parameters were measured (ulcerated areas (mm2), % of ulcer inhibition, gastric juice volume and pH, and mucus weight). Macroscopical and microscopical assessments of the stomachs as well as gastric biopsy histological studies were carried out. OFI oil exhibited a high efficiency in the protection of the cytoarchitecture and function of the gastric mucosa against the severe damages provoked by ethanol intake. Ulcerated areas were very significantly reduced and the % of ulcer inhibition was the highest under OFI oil pretreatment. Mucus production was stimulated, gastric juice volume was reduced, and its pH was increased. Histopathological examination of H&E-stained biopsies collected from gastric mucosae from the different experimental groups confirmed the gastroprotective efficacy of OFI oil against ethanol-induced symptoms such as inflammation and damages like bleeding, erosions, lesions, necrosis, and ulcers. Furthermore, OFI oil treatment speeded-up the reduction of the surface of ethanol-induced ulcerated areas in a dose-dependent manner, leading to a time gain in the healing process. The healing rate reached 91% on day 2 and 99% on day 3, and a complete heal was attained at the fourth day under OFI oil treatment, while ulcer areas were still partially unhealed in all the other groups. The therapeutic effects of OFI oil against gastric ulcer could be mediated by its varied bioactive compounds that we have demonstrated in the analytical study. They could act synergistically or in a delayed manner to optimize the healing process through protective antioxidant properties, as well as an antagonism against histamine H2-receptors, a stimulation of the signaling pathways necessary for mucus and bicarbonate production, and reduction of inflammatory processes in the gastric mucosa. Additionally, OFI oil fatty acids (especially unsaturated) and triacylglycerols contribute to the reconstruction and the repair of the cell membrane lipid bilayer during the gastric ulcer healing process.

Production of Sodium Bicarbonate from CO2 Reuse Processes: A Brief Review

Abstract Research activities discuss about the global environmental impacts of carbon dioxide (CO2) emissions. Government authorities and international conferences aim to reduce greenhouse gas emissions and encourage the development of sustainable processes using renewable sources. In order to reduce emissions from the industrial sector, CO2 capture and reuse as a raw material in the production of marketable products have encouraged the development of technologies. Among many possible chemical products manufactured from CO2, sodium bicarbonate appears in this context as an important compound in the chemical, food, textile and pharmaceutical industries. Then, the main objective of this work was to carry out a bibliographical review of the main production processes available in the literature for synthesis of sodium bicarbonate and the main chemical reactions involved in the crystallization reactor. Regarding to the processes, soda ash carbonation from trona, the Solvay process and the sodium sulfate route were assessed and compared. Among the main raw materials used in the production process of sodium bicarbonate, sodium chloride is presented as most economically feasible while sodium carbonate and sodium sulfate are indicated as the most environmentally viable alternatives. Beyond, the global processes were presented for each route discussing advantages and disadvantages for the separation and purification steps required after the reaction. It is notable that the main raw material is sodium chloride due to its easy possibility of obtaining, from seawater, and large availability for applications at the food industry. Indeed, the production of sodium bicarbonate by means of the Solvay process was the route that presented the best results regarding to the technology development and economic cost. Use of sodium sulfate as raw material has proved to be a possible route, besides presenting numerous advantages such as production of valuable byproducts. However, this route may be not totally viable compared to conventional routes due to the complexity of products separation and purification. The review showed that there is a lack in the scientific literature regarding to the development of studies evaluating sodium bicarbonate crystallization and purification in a cost effective and technical detailed approach.

Technoeconomic and Environmental Evaluation of Sodium Bicarbonate Production Using CO2 from Flue Gas of a Coal-Fired Power Plant

This study analyzes the technical, economic, and environmental feasibility of a CO2 mineralization process, which has great potential in terms of CO2 utilization capacity. The chosen process is the...

Abstract 565: Response of the Ischemic Myocardium to Adrenergic Stimulation as Detected by Hyperpolarized [1- 13 C]pyruvate

Metabolic imaging by nuclear methods is widely used to access ischemic myocardium but provide limited information about individual enzyme-catalyzed reactions. 13 C hyperpolarization methods are sensitive to flux in specific key enzymes such as lactate dehydrogenase and pyruvate dehydrogenase. We tested the hypothesis that LDH flux is increased while PDH flux is abolished in low-flow ischemia. Metabolism of HP [1- 13 C]pyruvate was studied in four groups: (1) normal perfusion pressure (NPP), 100 cm H 2 O; (2) NPP with epinephrine; (3) low-perfusion pressure (LPP), 25 cm H 2 O; (4) LPP with epinephrine. Hearts excised from male Sprague-Dawley rats were perfused (37°C) at an initial pressure of 100 cm H 2 O using standard Langendorff method with Krebs-Henseleit buffer containing 0.75% bovine serum albumin, 0.4 mM non-labeled free fatty acid, 5.5 mM [U- 13 C]glucose, 1 mM [3- 13 C]pyruvate, 0.1 mM [3- 13 C]lactate. Perfusion pressure was reduced to 25 cm H 2 O after 30 min of perfusion for ischemia group and epinephrine added at 50 th min of perfusion. HP [1- 13 C]pyruvate was injected to heart and subsequently, 13 C NMR spectra were acquired. The freeze clamped heart tissues were extracted with perchloric acid and analyzed by high-resolution 1 H and 13 C NMR (14.1 T). The 31 P NMR spectroscopy confirmed significant myocardial ischemia under LPP conditions, demonstrated by a marked increase in the [Pi]/[ATP] ratio. Surprisingly, increased LDH flux was observed in the ischemic hearts (+18.4%) while the metabolism of HP [1- 13 C]pyruvate by PDH remained unchanged as indicated by bicarbonate production. To investigate the oxidative capacity of mitochondria, epinephrine was used to stimulate hearts. As anticipated, epinephrine increased heart rate (+23%) and coronary flow (+11%) under NPP. Epinephrine increased heart rate (-60%) but did not alter coronary flow under LPP. We found that epinephrine had no effect on the rate of bicarbonate production under LPP. The study demonstrated that the conversion of pyruvate to lactate increased in ischemic hearts but the degree of pyruvate oxidation was not affected by the low-flow ischemia. Adrenergic stimulation did not increase PDH flux in these ischemic hearts. Translation to human is likely to provide new data from low-flow myocardium.

On the Conversion Efficiency of CO2 Electroreduction on Gold

Benjamin A. Zhang is a PhD student at Harvard University. His research focus is on the control of mass transport and concentration gradients in electrochemical reactions, in particular CO2 reduction, through nano- and mesostructuring of electrodes. Cyrille Costentin is Professor at Universite Paris Diderot. He received his undergraduate education at Ecole Normale Superieure de Cachan and his PhD at Universite Paris Diderot. He is currently a Visiting Scientist in the group of D.G. Nocera at Harvard University. His interests include mechanisms and reactivity in electron transfer chemistry with particular emphasis on proton-coupled electron transfer and catalysis of electrochemical reactions. Daniel G. Nocera is the Patterson Rockwood Professor of Energy at Harvard University. His group studies mechanisms of biological and chemical energy conversion.

Utilization of CO2 in Flue Gas for Sodium Bicarbonate Production in a Bubble Column

Utilization of CO2 in flue gases for the production of sodium bicarbonate is an environmentally friendly process. A mathematical model was constructed for the design and simulation of utilizing a low concentration CO2 (2-18%) in flue gas to produce sodium bicarbonate in a bubble column reactor. The model is based on the mass balance equations for three phases (gas, liquid, and solid). Danckwerts theory for mass transfer from the gas phase to the liquid phase coupling with chemical reaction, and crystallization mechanism was used. The effect of process variables; gas molar velocity or flux (G=2.5-10 mole/m2.s), liquid mass flow rate (mL=2800-3400 kg/h), sodium bicarbonate concentration (x1=0.04-0.1), CO2 gas mole fraction (y=0.02-0.18), column height (h=11-33 m), and column diameter (dR=1-3 m) on the objective variables; solid molar velocity (S), CO2 conversion, precipitation zone height (Zi), and crystal size distribution (CSD) were studied. The conversion of CO2 varied from 34% to 71% whereas the particle size range varied from 0 to 400 μm. The particle size range and the CO2 absorption efficiency of about 50% for 20 m column height are in agreement with the literature.

Modes of Accessing Bicarbonate for the Regulation of Membrane Guanylate Cyclase (ROS-GC) in Retinal Rods and Cones.

The membrane guanylate cyclase, ROS-GC, that synthesizes cyclic GMP for use as a second messenger for visual transduction in retinal rods and cones, is stimulated by bicarbonate. Bicarbonate acts directly on ROS-GC1, because it enhanced the enzymatic activity of a purified, recombinant fragment of bovine ROS-GC1 consisting solely of the core catalytic domain. Moreover, recombinant ROS-GC1 proved to be a true sensor of bicarbonate, rather than a sensor for CO2. Access to bicarbonate differed in rods and cones of larval salamander, Ambystoma tigrinum, of unknown sex. In rods, bicarbonate entered at the synapse and diffused to the outer segment, where it was removed by Cl--dependent exchange. In contrast, cones generated bicarbonate internally from endogenous CO2 or from exogenous CO2 that was present in extracellular solutions of bicarbonate. Bicarbonate production from both sources of CO2 was blocked by the carbonic anhydrase inhibitor, acetazolamide. Carbonic anhydrase II expression was verified immunohistochemically in cones but not in rods. In addition, cones acquired bicarbonate at their outer segments as well as at their inner segments. The multiple pathways for access in cones may support greater uptake of bicarbonate than in rods and buffer changes in its intracellular concentration.

Lipid biomarker patterns reflect different formation environments of mussel- and tubeworm-dominated seep carbonates from the Gulf of Mexico (Atwater Valley and Green Canyon)

Mussels and tubeworms thriving at many methane seeps typically live in symbiosis with chemosynthetic, chiefly methanotrophic or thiotrophic bacteria. It has been shown that the activities of chemosymbiotic animals can result in large differences in the sedimentary environments of their habitats. Here, we put forward the concept that such environmental variability can be archived in the lipid biomarker inventories of authigenic carbonates forming in different, locally confined environments at seeps, mussel beds and tubeworm bushes in this case. To test this hypothesis, lipid biomarker patterns of carbonates from mussel and tubeworm environments from two seep sites (Atwater Valley 340 and Green Canyon 852) of the Gulf of Mexico were analyzed. Previous work revealed stronger carbon isotope fractionation between the methane source and biomarkers of anaerobic methane oxidizing archaea-2 (ANME-2)/sulfate-reducing Desulfosarcina/Desulfococcus (DSS) consortia than for ANME-1/DSS consortia, both performing anaerobic oxidation of methane (AOM). Similar δ13Cmethane values were found at the mussel and tubeworm sites from the same seeps and the local microbial consortia also appear to be largely similar based on the observed AOM biomarker inventories. Yet, a large average offset of 32‰ between the δ13C values of molecular fossils of sulfate-reducing bacteria (SRB) involved in AOM was observed, with lower values typifying tubeworm carbonates than mussel carbonates. This pattern is interpreted to reflect local effects on isotope fractionation caused by the chemosymbiotic metazoans at mussel- and tubeworm-dominated sites. At tubeworm-dominated sites, the excess sulfate produced by thiotrophic symbionts of tubeworms and pumped down into the sediment results in persistent production of AOM-derived bicarbonate and the enrichment of 12C in sub-surface sediments. Interestingly, tubeworm carbonates also contain high amounts of non-isoprenoidal dialkyl glycerol diethers (DAGEs) with extreme 13C depletions, representing compounds that derived from non-DSS cluster SRB. Most likely, 13C-depleted AOM-derived organic intermediates were used as carbon sources by the DAGE-producing non-DSS cluster SRB, possibly performing organoclastic sulfate reduction. Our study identifies significant variation in biomarker patterns between mussel and tubeworm carbonates at two seep sites in the Gulf of Mexico. Such variation allows to characterize different habitats at seeps, which are shaped by the interaction of chemosymbiotic seep metazoans and their symbionts with the local environment. Metazoan community composition apparently controls geobiological interaction in seep ecosystems to a large degree, which may allow tracing of the effects of chemosymbiosis into the rock record.

Translation of Carbon-13 EPI for hyperpolarized MR molecular imaging of prostate and brain cancer patients.

To develop and translate a metabolite-specific imaging sequence using a symmetric echo planar readout for clinical hyperpolarized (HP) Carbon-13 (13 C) applications. Initial data were acquired from patients with prostate cancer (N = 3) and high-grade brain tumors (N = 3) on a 3T scanner. Samples of [1-13 C]pyruvate were polarized for at least 2 h using a 5T SPINlab system operating at 0.8 K. Following injection of the HP substrate, pyruvate, lactate, and bicarbonate (for brain studies) were sequentially excited with a singleband spectral-spatial RF pulse and signal was rapidly encoded with a single-shot echo planar readout on a slice-by-slice basis. Data were acquired dynamically with a temporal resolution of 2 s for prostate studies and 3 s for brain studies. High pyruvate signal was seen throughout the prostate and brain, with conversion to lactate being shown across studies, whereas bicarbonate production was also detected in the brain. No Nyquist ghost artifacts or obvious geometric distortion from the echo planar readout were observed. The average error in center frequency was 1.2 ± 17.0 and 4.5 ± 1.4 Hz for prostate and brain studies, respectively, below the threshold for spatial shift because of bulk off-resonance. This study demonstrated the feasibility of symmetric EPI to acquire HP 13 C metabolite maps in a clinical setting. As an advance over prior single-slice dynamic or single time point volumetric spectroscopic imaging approaches, this metabolite-specific EPI acquisition provided robust whole-organ coverage for brain and prostate studies while retaining high SNR, spatial resolution, and dynamic temporal resolution.

Optimization of Sodium Bicarbonate Production Using Response Surface Methodology (RSM)

The main objective of this study was to evaluate the use of batch bubble column to produce high particle size (>300 micron) of sodium bicarbonate product to improve filtration and drying operations in the production process. Lab scale batch bubble column of 80 mm diameter and 0.5 m height was used to study the process for sodium bicarbonate production using 20% sodium carbonate solution as a starting solution. Three operating variables were considered, CO2 gas content (20-100 %), temperature (30-70 oC) and time (0.5-2.5 h). The bicarbonate yield and crystals size were considered to be the objective variables of the process. Response surface methodology (RSM) was used with central composite design (CCD) of experiments. Empirical polynomial multivariable equations were obtained. The reaction time was found to be the most effective operating condition on the yield of sodium bicarbonate, and temperature was found to be the most effective operating condition on crystal size of sodium bicarbonate. The optimum conditions achieved 400 microns particle size at temperature 70 oC and time 2.5 h. Kinetics study of the process showed that zero order reaction with both sodium carbonate and CO2 concentrations was approximately fitted the experimental data, useful for shortcut process design purposes.

The "Missing" Bicarbonate in CO2 Chemisorption Reactions on Solid Amine Sorbents.

We have identified a hydrated bicarbonate formed by chemisorption of 13CO2 on both dimethylaminopropylsilane (DMAPS) and aminopropylsilane (APS) pendant molecules grafted on SBA-15 mesoporous silica. The most commonly used sequence in solid-state NMR, 13C CPMAS, failed to detect bicarbonate in these solid amine sorbent samples; here, we have employed a Bloch decay ("pulse-acquire") sequence (with 1H decoupling) to detect such species. The water that is present contributes to the dynamic motion of the bicarbonate product, thwarting CPMAS but enabling direct 13C detection by shortening the spin-lattice relaxation time. Since solid-state NMR plays a major role in characterizing chemisorption reactions, these new insights that allow for the routine detection of previously elusive bicarbonate species (which are also challenging to observe in IR spectroscopy) represent an important advance. We note that employing this straightforward NMR technique can reveal the presence of bicarbonate that has often otherwise been overlooked, as demonstrated in APS, that has been thought to only contain adsorbed CO2 as carbamate and carbamic acid species. As in other systems (e.g., proteins), dynamic species that sample multiple environments tend to broaden as their motion is frozen out. Here, we show two distinct bicarbonate species upon freezing, and coupling to different protons is shown through preliminary 13C-1H HETCOR measurements. This work demonstrates that bicarbonates have likely been formed in the presence of water but have gone unobserved by NMR due to the nature of the experiments most routinely employed, a perspective that will transform the way the sorption community will view CO2 capture by amines.

Techno-economic and environmental evaluation of CO2 mineralization technology based on bench-scale experiments

This work presents a techno-economic & environmental analysis of a CO2 mineralization process, intended to examine its potential for CO2 reduction and economic feasibility. The CO2 mineralization technology of this study is composed of the CO2 carbonation process and the brine electrolysis process, producing various chemical compounds such as sodium bicarbonate, hydrogen, and chlorine. Notably, the CO2 mineralization process is able to utilize flue gas with a low concentration of CO2 that has not been subjected to CO2 capture processes. For the technical feasibility analysis of the CO2 mineralization process examined in the study, performance evaluation is conducted for a bench-scale CO2 mineralization test unit (2 kg/day CO2 utilization capacity), yielding sodium bicarbonate of over 97% purity. It is also estimated that the CO2 utilization process of this study produces 0.65 tons of CO2 emissions per ton of sodium bicarbonate produced, which indicates a 2.09 ton CO2 reduction compared to the conventional processes which produce 2.74 tons of CO2 emissions for the same amount of sodium bicarbonate production. With these results as a basis, an economic evaluation is conducted for a commercial-scale CO2 utilization plant (sodium bicarbonate production capacity: approximately 5000 tons/year) which utilizes CO2 in flue gas produced from thermal power plants. The evaluation supports the economic feasibility of the process with a benefit/cost ratio (B/C ratio) of 1.12 and internal rate of return (IRR) of 10.4%.

Recent progress in CO<sub>2</sub> catalytic reduction to high value-added chemicals

CO2 is a kind of greenhouse gas, which has an important influence on the atmospheric environment, and it is also a kind of cheap carbon resource. The production of urea and ammonium bicarbonate by the reaction of NH3 and CO2 in the synthetic ammonia industry is a model for the large-scale utilization of CO2. Recent studies show that with the effect of high efficiency catalyst, CO2 can be used as a raw material to participate in the synthesis of fine chemicals. For example, CO2, H2 (or organosilane) and amines can generate N- formamide and N , N- dimethylamine. H2 (or organosilane) can reduce CO2 to form formic (acetic) acid. CO2 can also be used as a raw material to participate in the synthesis of basic chemicals. CO2 and H2 can produce high value-added chemicals such as light olefins and methanol under different reaction conditions, which opens up some new ways for the conversion and utilization of CO2. In this article, we summarize, review and forecast the high efficiency catalyst system, process conditions of catalytic system and mechanism of catalytic reaction about the catalytic reduction of CO2 with H2 in recent years. Specifically, we focus on three types of chemical reactions: CO2, H2 (or organosilane) and amines generate N- formamide and N , N- dimethylamine; H2 (or organosilane) reduce CO2 to form formic (acetic) acid; CO2 and H2 produce high value-added chemicals such as light olefins and methanol. We expect to provide a reference for the development of new technology about the catalytic reduction of CO2 to produce high value-added chemicals.

Electrochemical reduction of bicarbonate on carbon nanotube-supported silver oxide: An electrochemical impedance spectroscopy study

Bicarbonate reduction on a silver-oxide (Ag2O)-based electrode was studied via cyclic voltammetry and electrochemical impedance spectroscopy techniques. The effects of electrode composition, electrolyte concentration and the scan rate (10–250 mV/s) were investigated at a temperature of 27 °C. An optimum mass ratio of 70/30 (Ag2O/CNT) led to a maximum current density of 83 mA cm−2 at −0.43 V (VS Ag/AgCl). At scan rates between 10 and 250 mV/s, a negative shift with a displacement of around 1.032 V was observed – indicating the presence of irreversible reduction reactions. The observed irreversibility suggested that the reaction mechanism can be described by both diffusion and adsorption phenomena. The standard heterogeneous rate constant (ko) and the formal redox potential (Eo) were found to be 1.51 × 10−4 cm/s and 1.218 V, respectively. The EIS results confirmed the formation of the inductive loops at reduction potentials – a consequence of the adsorption of the generated species. A reduction in charge transfer resistance and a continual drop in the potential from −0.1 down to −1.4 V was also observed. This was accompanied by H2 evolution and bicarbonate production. The calculated pKa value of 10.20 upon the completion of the bicarbonate reduction reactions, confirmed the conversion of bicarbonate to carbonate ions.

The effect of metabolic alkalosis on the ventilatory response in healthy subjects

BackgroundPatients with acute respiratory failure may develop respiratory acidosis. Metabolic compensation by bicarbonate production or retention results in posthypercapnic alkalosis with an increased arterial bicarbonate concentration. The hypothesis of this study was that elevated plasma bicarbonate levels decrease respiratory drive and minute ventilation. MethodsIn an intervention study in 10 healthy subjects the ventilatory response using a hypercapnic ventilatory response (HCVR) test was assessed, before and after administration of high dose sodium bicarbonate. Total dose of sodiumbicarbonate was 1000 ml 8.4% in 3 days. ResultsPlasma bicarbonate increased from 25.2 ± 2.2 to 29.2 ± 1.9 mmol/L. With increasing inspiratory CO2 pressure during the HCVR test, RR, Vt, Pdi, EAdi and VE increased. The clinical ratio ΔVE/ΔPetCO2 remained unchanged, but Pdi, EAdi and VE were significantly lower after bicarbonate administration for similar levels of inspired CO2. ConclusionThis study demonstrates that in healthy subjects metabolic alkalosis decreases the neural respiratory drive and minute ventilation, as a response to inspiratory CO2.