K2CO3 Aqueous Solutions Research Articles

Membrane-separated reactor for an integrated CO2 capture-mineralization process using carbonic anhydrase

To achieve carbon neutrality through CO2 mineralization, it is important to design the novel reaction process through a distinct understanding of the critical reaction steps, CO2 hydration, and calcium carbonation. A semi-batch system was introduced to conduct a model mineralization reaction to confirm the reaction-determining step (RDS) of CO2 mineralization. The CO2 hydration step was confirmed as RDS according to various model reactions in a semi-batch reactor. CA enzyme was introduced to promote CO2 hydration to increase the overall reaction rate. With the introduction of the CA enzyme, the hydration reaction rate was increased by about 4-fold, but the CA enzyme was lost due to coprecipitation with CaCO3 during the reaction. A membrane-separated reactor was designed to maintain high activity and decrease the loss of CA enzyme during the reaction. Furthermore, in the membrane-separated reactor, the CA enzyme facilitated the CO2 mineralization much more effectively in the K2CO3 aqueous solution than in the D.I. water because the K2CO3 aqueous solution has a higher CO2 absorption capacity and a weekly alkaline condition favorable for CA enzyme operation. Finally, by proposing a continuous reaction system for reusing enzymes and water, we suggested that the membrane-separated reactor could be applied in practical CO2 capture-mineralization.

Oxidative degradation of Piperazine (PZ) in aqueous KOH/K2CO3 solutions

KOH and K2CO3 aqueous solutions have demonstrated potential for CO2 absorption processes due to their low toxicity, non-volatility of the capture agent and resistance to degradation. However, their absorption kinetics are typically slower than those of primary and secondary amines, and therefore promotors may be needed to allow competitive absorption rates and thus absorber heights. Here, we selected piperazine (PZ) as a promoter and investigated its oxidative degradation when blended with KOH or K2CO3. The changes in PZ concentration were analyzed by gas chromatography–mass spectrometry (GC–MS), while the degradation products were analyzed by GC–MS and anion chromatography. The results showed that PZ oxidative degradation followed the order KOH/PZ > PZ > K2CO3/PZ indicating that KOH enhanced PZ oxidation while K2CO3 inhibited PZ oxidation. Therefore, KOH/PZ may still be a promising solvent with appropriate CO2 loading as the CO2 protects the PZ from hydroxyl and oxygen radical attacks. The degradation products are similar across the blends and identified as Ethylenediamine (EDA), 2-oxopiperazine (OPZ), Formylpiperazine (FPZ), formate, acetate and oxalate, with formate being the most abundant product for all blends. Furthermore, the PZ first-order rate constants for all solutions were provided, and the oxidation degradation pathway of PZ-based solutions was proposed.

Numerical simulation of CO2 / H2S simultaneous removal from natural gas using potassium carbonate aqueous solution in hollow fiber membrane contactor

Abstract The sweetening process of natural gas has an undeniable rule in mitigating the detrimental influences of the toxic / corrosive chemical contaminants as like as CO2 and H2S on industrial units and environment. In this study, a 2D numerical simulation was developed to investigate the CO2 / H2S simultaneous molecular removal from natural gas utilizing K2CO3 aqueous solution circulating through the hollow fiber membrane contactor (HFMC). Simulation results were evaluated versus those of experimentally measured data gathered from the literature and an acceptable agreement was observed, i. e. average absolute relative errors (AAREs) of around 1.2 and 1.5 % in the simulated and the experimentally measured CO2 fluxes versus the liquid and gas phases’ velocities, respectively. Also, the results illustrated that increment in the membrane porosity and module length eventuated in a substantial improvement in the molecular removal of CO2 and H2S while increase in the membrane tortuosity and gas velocity significantly reduced CO2 and H2S removal.

Raman and infrared spectroscopic quantification of the carbonate concentration in K2CO3 aqueous solutions with water as an internal standard

Carbonate-bearing fluids widely exist in different geological settings, and play important roles in transporting some elements such as the rare earth elements. They may be trapped as large or small fluid inclusions (with the size down to <1 ​μm sometimes), and record critical physical-chemical signals for the formations of their host minerals. Spectroscopic methods like Raman spectroscopy and infrared spectroscopy have been proposed as effective methods to quantify the carbonate concentrations of these fluid inclusions. Although they have some great technical advantages over the conventional microthermometry method, there are still some technical difficulties to overcome before they can be routinely used to solve relevant geological problems. The typical limitations include their interlaboratory difference and poor performance on micro fluid inclusions. This study prepared standard ion-distilled water and K2CO3 aqueous solutions at different molarities (from 0.5 to 5.5 ​mol/L), measured densities, collected Raman and infrared spectra, and explored correlations between the K2CO3 molarity and the spectroscopic features at ambient P-T conditions. The result confirms that the Raman O–H stretching mode can be used as an internal standard to determine the carbonate concentrations despite some significant differences among the correlations, established in different laboratories, between the relative Raman intensity of the C–O symmetric stretching mode and that of the O–H stretching mode. It further reveals that the interlaboratory difference can be readily removed by performing one high-quality calibration experiment, provided that later quantifying analyses are conducted using the same Raman spectrometer with the same analytical conditions. Our infrared absorption data were collected from thin fluid films (thickness less than ~2 ​μm) formed by pressing the prepared solutions in a Microcompression Cell with two diamond-II plates. The data show that both the O–H stretching mode and the O–H bending mode can be used as internal standards to determine the carbonate concentrations. Since the IR signals of the C–O antisymmetric stretching vibration of the CO32− ion, and the O–H stretching and bending vibrations from our thin films are very strong, their relative IR absorbance intensity, if well calibrated, can be used to investigate the micron-sized carbonate-bearing aqueous fluid inclusions. This study establishes the first calibration of this kind, which may have some applications. Additionally, our spectroscopic data suggest that as the K2CO3 concentration increases the aqueous solution forms more large water molecule clusters via more intense hydrogen-bonding. This process may significantly alter the physical and chemical behavior of the fluids.

Efficient synthesis of cholic acid derivates through stereoselective C–H functionalization from hyodeoxycholic acid

Five cholic acid derivatives (including allo-ω-muricholic acid and CDCA) were synthesized from hyodeoxycholic acid via selective oxidation of C3- or C6-hydroxyl groups by IBX and NBS oxidants and stereocontrolled conversion. The hydroxyl group could be introduced through hydrolyzing α-Br keto with K2CO3 aqueous solution or through oxidizing the double bond by monoperoxyphthalic acid. The reduction of C6-O6 carbonyl to methylene could undergo with PTSH, NaBH3CN and ZnCl2 only at 5β configuration. A feasible synthetic route of CDCA from HDCA has been established to avoid the epimerization with the yield of 45% (8 steps). These strategies provided good yields, stereoselectivity and reproducibility for the preparation of cholic acid derivates and CDCA.

CO2 Capture Process and Corrosion of Carbon Steel in [Bmim][Lys]-K2CO3 Aqueous Solutions

CO2 Capture Process and Corrosion of Carbon Steel in [Bmim][Lys]-K2CO3 Aqueous Solutions

Corrosion behavior of carbon steel in the CO2 absorption process using MEA activated K2CO3 aqueous solutions

Corrosion of carbon steel in the CO2 absorption process using MEA activated K2CO3 aqueous solutions was investigated. The effects of the mass concentrations of MEA, solution temperature and CO2 loading on the corrosion rate of carbon steel were demonstrated. The experimental results provided comprehensive information on the appropriate concentration range of MEA aqueous solutions under the situation which low corrosion of carbon steel can be achieved.

Crystallization of Poly(ethylene oxide) on the Surface of Aqueous Salt Solutions Studied by Grazing Incidence Wide-Angle X-ray Scattering.

We report the thin layer crystallization of high-molar mass poly(ethylene oxide) (PEO) on a liquid support using a 4 M K2CO3 aqueous solution as a subphase. Because of the Hofmeister effect, PEO does not dissolve and remains at the surface during compression on a Langmuir trough. The transition from the flat pancake conformation upon compression of the spread polymer film to an entangled monolayer results in a plateau region of the Langmuir isotherm. Using grazing incidence wide-angle X-ray scattering, the final crystallization of PEO was observed, and the crystal orientation was determined. The fold surface was (209̅), that is, the helix axis has a tilt angle of 2.9° to the normal vector of the water surface.

Surface modification to produce superhydrophobic hollow fiber membrane contactor to avoid membrane wetting for biogas purification under pressurized conditions

Abstract This article investigates CO2 removal from biogas (containing 40% CO2 and 60% CH4) using a hollow fiber membrane contactor (HFMC) with K2CO3 aqueous solutions as absorbent at elevated pressures up to 10 bar. Superhydrophobic PTFE membrane fibers (with a water contact angle of 158.4° and sliding angle of 1.3°) were fabricated by spraying silica nanoparticles on membrane surface and then used in membrane module for absorption experiments. The modified membrane outperformed the original membrane at elevated absorption pressures, and the highest CO2 removal efficiency and absorption flux reached 97.1% and 1.85 × 10−3 mol m−2 s−1, respectively. A 2D axisymmetric non-wetted mathematic model was developed to determine the membrane wetness conditions during absorption experiments. The model validation results indicated that when using aqueous K2CO3 solutions as absorbent the modified superhydrophobic membrane used in this study was able to prevent membrane wetting even at pressurized conditions up to 10 bar. This work showed that the superhydrophobic membranes modified by spray-deposition technique have great potential for application in HFMC to avoid membrane wetting for biogas purification under pressurized conditions.

Absorption capacity and viscosity for CO2 capture process using [N1111][Gly] promoted K2CO3 aqueous solution

Absorption performance of carbon dioxide (CO2)nitrogen (N2) mixture in tetramethylammonium glycinate ([N1111][Gly]) promoted potassium carbonate (K2CO3) aqueous solution was investigated. The mass fractions of [N1111][Gly] and K2CO3 respectively ranged from 0 to 0.075 and 0.15 to 0.25. The temperature ranged from 303.2K to 323.2K. The mole fraction of CO2 in CO2N2 mixture ranged from 0.3 to 1.0. Results showed that the absorption of CO2 can be accelerated remarkably when K2CO3 aqueous solution was promoted by small amount of [N1111][Gly]. The effects of temperature, solution composition and partial pressure of CO2 on the absorption capacity were illustrated. The viscosities of K2CO3-[N1111][Gly] aqueous solutions were measured and correlated, and the effects of temperature and mass fractions of K2CO3 and [N1111][Gly] on viscosities were demonstrated on the basis of experiments and calculations.

Extraction and recovery of penicillin G from solution by cascade process of hollow fiber renewal liquid membrane

The feasibility of cascade process for penicillin G recovery utilizing hollow fiber renewal liquid membrane (HFRLM) technique was investigated and the optimal conditions were determined. Cascade process of HFRLM was carried out to recover penicillin G from the aqueous solution using di-n-octylamine in iso-octanol and kerosene as the liquid membrane phase and K2CO3 aqueous solution as the stripping phase. The mass transfer performance of the process was evaluated in a hollow fiber module with 1000 microporous and hydrophobic polypropylene (PP) hollow fibers. The cascade process of HFRLM was feasible for penicillin G recovery and the enrichment factor, extraction and recovery efficiency were larger than that of single-stage process. The stripping phase of 0.5molL−1K2CO3 solution could not only keep the efficiency of re-extraction, but also ensure the stability of penicillin G. Besides, the results indicated that 0.2molL−1 potassium dihydrogen phosphate solution as the buffer solution in the feed solution could greatly reduce the loss of penicillin G due to the pH fluctuation. In the cascade mode operated at the flow rates of 45mLmin−1 in the shell side and 20 mLmin−1 in the tube side, the extraction and recovery efficiency of 97% and 82% for penicillin G were achieved after 7 stages respectively. The cascade process of HFRLM for penicillin G recovery exhibits good potential in industrial application.

Improved Electrochemical Behavior of Amorphous Carbon-Coated Copper/CNT Composites as Negative Electrode Material and Their Energy Storage Mechanism

A composite of copper grown on the surface of CNTs has been fabricated by a redox reaction between copper acetate and ethylene glycol for use as negative electrode at high currents in electrochemical energy storage. Subsequently, the as-prepared Cu/CNT composite was coated with carbon using glucose as carbon source. Structure, morphology and electrochemical performance of the composite were investigated by scanning electron microscopy, X-ray diffraction, XPS, and electrochemical measurements. The carbon coating effectively prevents the dissolution of copper carbonate complexes formed during the electrode reactions and , increases the conductivity of the copper constituent in the negative electrode and protects this component against direct contact with the electrolyte solution during cycling. The C/Cu/CNTs composite exhibits higher capacity and better rate behavior as well as excellent cycling stability in 0.5 M K2CO3 aqueous solution than unsupported copper.

Particular structural defects in Ta2O5 from crystallisation of amorphous thin films in O2–H2O atmosphere

Structural defects within Ta2O5 monoclinic structures were obtained by crystallisation at 850°C in atmosphere O2–H2O of amorphous thin films deposited by injection metal-organic chemical vapour deposition (i-MOCVD) on Si substrates. These defects, observed by high resolution transmission electron microscopy (HRTEM), contain alignments of Ta5+ vacancies along a crystallographic direction [001]. H2O gas of different partial pressures was obtained by bubbling O2 gas through deionised water or Na2CO3–K2CO3 aqueous solution maintained at different temperatures in a range of 25–45°C. The amount of structural defects increases dramatically with H2O partial pressure and annealing time from HRTEM observations and X-ray diffraction results. Such defects are thermally stable, at least up to 850°C. Using Na2CO3–K2CO3 aqueous solution, similar structural defects including mainly K+ species were formed. Na+ species contributes mostly to the formation of another phase of composition close to (Na0.8K0.2)2Ta4O11 of natrotantite type structure. Assuming that Ta5+ vacancies are occupied by H+ in a form of bridging hydroxyl groups Ta–OH–Ta in order to satisfy electrical neutrality, the presence of significant levels of hydrogen atoms within Ta2O5 concordant with H enrichment at defects was identified by time-of-flight secondary ion mass spectrometry (ToF-SIMS).

Removal of Carbon Dioxide from Indoor Air Using a Cross- Flow Rotating Packed Bed

This investigation elucidated the performance of the cross-flow rotating packed bed (RPB) in removing carbon dioxide (CO2) from indoor air by chemical absorption. MEA, NaOH, K2CO3 aqueous solutions were used as the model absorbents. The results of this investigation demonstrated that the removal efficiency of CO2 increased with rotational speed and liquid flow rate, but decreased with gas flow rate. Furthermore, the removal efficiency of CO2 could be enhanced when H2O2 with an appropriate concentration was added to the K2CO3 aqueous solution. The removal efficiency of CO2 was found with the order: 1.0mol/L MEA = 1.0mol/L NaOH > 5 wt% K2CO3/0.20mol/L H2O2 > 5 wt% K2CO3/0.1mol/L H2O2> 5 wt% K2CO3/0.05mol/L H2O2 > 5wt% K2CO3.

화학 흡수를 이용한 KOH 수용액의 이산화탄소 포집 성능에 관한 연구

The present paper investigates the performance of the KOH aqueous solution as an absorbent to capture carbon dioxide (CO2). The chemical absorption was carried out according to consecutive reactions that are generated in the order of K2CO3 and KHCO3. The overall absorption was completed with following the physical absorption. When the absorption was conducted with the KOH as the limiting reactants in batch a reactor, K2CO3 production rate was the 1st order reaction for OH. However, KHCO3 generation reaction was independent of the CO3 concentration and the rate was calculated to be 0.18 gCO2/min for all KOH absorbents, which is the same value of the reaction rate using K2CO3 aqueous solution as the absorbents. The overall CO2 capture ratio of the 5% KOH absorbent was estimated to be 19% and the individual value in section 1 and 2 was 57 and 12%, respectively. The amount of CO2 absorbed in the solution was very slightly less than the theoretical value, which was ascribed to the side reaction that produces K2CO3・KHCO3・1.5H2O during the reaction and the consequent diminish in CO2 absorption in the KOH solution.

Preparation of 1‐hydroxyethylidene‐1,1‐diphosphonic acid‐intercalated layered double hydroxide and its physicochemical properties

The intercalation of 1‐hydroxyethylidene‐1,1‐diphosphonic acid (HEDP), which is a drug for osteoporosis, in layered double hydroxide (LDH) was examined with the goal of developing a novel drug delivery system (DDS) of HEDP. To prevent side reactions, the intercalation reaction was carried out at 0°C, and at pH 4–6. The uptake of HEDP was determined as 3.5 mmol g−1 of LDH, and the interlayer distance increased from 7.8 to 13 Å. The HEDP‐release profiles into K2CO3 aqueous solution and into various buffer solutions were also examined. © 2003 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2419–2426, 2003

Facile and Selective Conversion of Ethylenediaminetetraacetate to Ethylenediamine-N,N,N′-triacetate on a Cobalt Complex

Abstract Ethylenediaminetetraacetatocobaltate(III) is converted to aqua(ethylenediamine-N,N,N′-triacetate)cobalt(III) selectively in a 1 mol dm−3 K2CO3 aqueous solution at room temperature in the presence of PbO2. This reaction could be a simple and versatile procedure to obtain ed3a-type ligands.

The viscosity of Na2CO3 and K2CO3 aqueous solutions in the range 20?60�C

Results of new relative measurements of the density and viscosity of aqueous solutions of Na2CO3 and K2CO3 at atmospheric pressure are presented. The temperature ranged from 20 to 60°C, and the composition ranged from pure water to near saturation. All the data have been correlated with the aid of double polynomials. Owing to some evidence of chemical attack of the borosilicate viscometers, the accuracy of the viscosity measurements is estimated to be ±1%, whereas that of density is estimated to be ±0.01%.