Na2CO3 Aqueous Solution Research Articles

CaCO<sub>3</sub> Nanopowder Production by Co-Precipitation of Aerosols of Precursor Solutions of Na<sub>2</sub>CO<sub>3</sub> and CaCl<sub>2</sub>

Submicron-sized calcium carbonate (CaCO3) particles were prepared using an aerosol method in which two commercial air humidifiers containing 0.05 M of Na2CO3 and CaCl2 aqueous solutions were utilized as aerosol suppliers. Two streams of aerosols evaporated from the separate humidifiers were allowed to meet in 17-meter long, spiral reaction tube where collisions between two types of droplets containing precursor reagents leaded to grow of CaCO3 particles and precipitate onto the inner walls. XRD and SEM analysis revealed that CaCO3 particles were formed in calcite phase almost entirely.

Synthesis and evaluation of a new water‐soluble fluorescent red dye, xanthene bis‐C‐glycoside

AbstractCondensation of 2 eq. of C‐β‐D‐glucosylphloroacetophenone with glyoxylic acid in an aqueous solution of Na2CO3, followed by air oxidation in MeOH in the presence of 11 eq. of pyridine to afford a 36% yield of a bright red dye, xanthene bis‐C‐glycoside. This dye is 10 times more fluorescent (Φf [EtOH]581 nm = 3.9 × 10−2) and 7.5 times more water‐soluble (57 mg/mL H2O) than the natural red pigment, carthamin. Detailed NMR analysis of its methyl analogs was used to confirm the structure of the dye as methyl 4,5‐diacetyl‐1,3,8‐trihydroxy‐3‐oxo‐3H‐2,7‐di‐C‐β‐D‐glucopyranosylxanthene‐9‐carboxylate from among three possible ring‐closure isomers. Xanthene is safe and shows high light‐resistance; therefore, xanthene bis‐C‐glycoside could be used as a food colorant or an in vivo probe.

6-acylamino nicotinic acid-based hydrogelators applicable in phase selective gelation, reproducible mat formation and toxic dye removal

Formation of nanofibers and nanovesicles in the self-assembled state of small amphiphilic molecules has applications in versatile fields such as tissue engineering, controlled delivery of drug molecules, etc. This paper demonstrated the self-aggregation behavior of three synthesized 6-acylamino nicotinic acid amphiphiles named 6-octanoylamino-nicotinic acid (OANA), 6-decanoylamino-nicotinic acid (DANA) and 6-dodecanoylamino-nicotinic acid (DDANA) in water and basic aqueous solution. The result showed that the amphiphiles successfully self-organize into vesicles and twisted ribbons in water. FT-IR study revealed existence of mixtures of handedness in the fibrous structures. CD spectroscopy and TEM study elucidated formation of chiral structures through aggregation. Results showed that DDANA forms thermoreversible hydrogel in aqueous solutions of NaOH and Na2CO3, whereas other two amphiphiles form hydrogel only in the presence of NaOH. Morphological investigation revealed that the hydrogel is formed due to self-assembly of fibrils of micron length. The elastic fibrillar networks are quite stable to external forces. Existence of bilayer columnar square packing arrangement in the self-assembled state was recognized by XRD measurement. Spectroscopy and theoretical studies established that hydrogen bonding interactions are responsible to self-assemble the amphiphilic molecules. The amphiphiles are efficient phase selective gelators of mineral oils in water–mineral oil mixtures and excellent remover of rhodamine 6G, eosin Y and rose bengal from water. The amphiphiles successfully create reproducible fiber mat applicable in tissue engineering field.

Quartz solubility in sodium carbonate solutions at high pressure and temperature

We present new experimental data on the synthetic quartz (Qtz) solubility in the Na2CO3 aqueous solutions ranging in salt concentration from 0.3–3.5 m (mole/kg H2O). The data have been collected in the temperature (T) range 500–700 °C at pressure (P) 4 kbar and 600 °C/5 kbar in an internally heated pressure vessel, with phase assemblage bracketing as a solubility monitor in quench experiments: first disappearance of crystalline Qtz in a succession of runs with constant Na2CO3 concentration but decreasing the Qtz/solution weight ratio was taken for the solubility value. It was possible to “bracket” the solubility within about 1 wt% by carefully observing the presence or absence of crystalline Qtz in the run products. Qtz solubility varies systematically with P, T, and particularly, with the Na2CO3 molality, increasing from 0.7 m for the 0.3 m Na2CO3 to 4 m for the 3.5 m Na2CO3 (at 600 °C/4 kbar). In all cases the SiO2 molality in the solutions exceeds that of Na2CO3, which suggests the presence of polymerized silica species in the solutions. Quantum chemical computations showed the dimer H5Si2O7− as the most stable species, which corresponds to the dehydrated species Si2O4OH− in the framework of the revised Helgeson–Kirkham–Flowers equation of state (HKF). A complete set of thermodynamic quantities for Si2O4OH−, consistent with the revised HKF and the DEW model (Sverjensky et al., 2014) has been retrieved from the experiments. Calculations with the obtained set of thermodynamic parameters reproduce very well the Qtz solubility experiments performed in a simpler H2O-NaOH fluid at 600 °C/4 kbar. Model calculations of silica and Ca solubility in the 15 wt% (3 m) NaCl aqueous solution interacting with a siliceous carbonate rock (Qtz + Calcite saturated) along a 13°/km geotherm, which take into account Si2O4OH−, predict much higher bulk Si and Ca contents in the fluid phase than in equilibrium with the corresponding individual minerals for P above 4–5 kbar.

Electrolytes Change the Interfacial Water Structure but Not the Vibrational Dynamics.

Heterogeneous ozone chemistry occurring on aerosols is driven by interfacial chemistry and thus affected by the surface state of aerosol particles. Therefore, the effect of electrolytes on the structure of interfacial water has been under intensive investigation. However, consequences for energy dissipation rates and mechanisms at the interface are largely unknown. Using time-resolved sum frequency generation spectroscopy, we reveal that the relaxation pathway is the same for neat water-air as for aqueous solutions of Na2SO4 and Na2CO3. We further show that similar lifetimes are extracted from all investigated systems and that these lifetimes show an excitation frequency dependent relaxation time from 0.2 ps up to 1 ps. Hence, despite static SFG on the same systems revealing that the interfacial aqueous structure changes upon adding electrolytes, the vibrational dynamics are indistinguishable for both pure water and different electrolyte solutions.

Effect of sodium content on the interaction between Ni and support and catalytic performance for syngas methanation over Ni/Zr–Yb–O catalysts

In this paper, Ni/Zr–Yb–O catalysts with different sodium contents are prepared by a co-precipitation method, using aqueous Na2CO3 solution as a precipitant, and the effect of sodium on the catalyst structure and catalytic performance for syngas methanation is extensively investigated using five Ni/Zr–Yb–O catalysts, containing 0, 0.5, 1.5, 4.5 and 13.5 wt% Na+, those are denoted as Cat-1, Cat-2, Cat-3, Cat-4 and Cat-5 respectively. It is found that the interaction between Ni and support determines the catalytic performance of Ni/Zr–Yb–O and the residual sodium content negatively affects the interaction between Ni and support. Cat-1 exhibits an excellent catalytic performance. During a long run time of 380 h, no deactivation is observed and both CO conversion and CH4 selectivity maintain a level above 90%. However, Cat-3 and Cat-5 suffer rapid deactivation under the same reaction condition. The characterization results indicate the strong interaction between Ni and support enables Cat-1 to possess well dispersed Ni species, resistance to sintering and carbon deposition and thus the excellent catalytic performance. However, the presence of sodium ions over Ni/Zr–Yb–O degrades the interaction between Ni and support and the catalytic performance, especially for the stability. The relative weak interaction between Ni and support results in severe sintering of both ZrO2 and Ni under the reaction condition, carbon deposition and the poor catalytic performance.

Photoluminescence changes of Tb-substituted layered double hydroxides caused by capturing carbonate ions in water

Tb-substituted layered double hydroxides (Tb-LDHs) with NO3− in the interlayer were synthesized by a hydrothermal method and then used to capture and sense CO32− in aqueous solution. X-ray diffractometry confirmed that single-phase Tb-LDHs with Tb contents of 1–5 mol% were successfully synthesized. The NO3− ions of 5 mol% Tb-substituted LDH (Tb5LDH) were exchanged by CO32− ions in a Na2CO3 aqueous solution at pH = 11. The ion exchange for Tb5LDH was promoted with increasing the concentration of the Na2CO3 solution. Photoluminescence spectroscopy revealed that Tb5LDH with CO32− in the interlayer displayed an excitation wavelength of 229 nm and exhibited a green emission signal originating from the 4f8 → 4f75d1 transition, 5D4 → 7FJ (J = 3, 4, 5, 6), in the range of 400–700 nm. The intensity of the emission signal of the ion-exchanged Tb5LDH excited at 229 nm increased with increasing the content of CO32− in Tb5LDH. These results indicate that Tb5LDH was capable of capturing and sensing CO32− dissolved in water by irradiation with 229-nm light.

Topotaxial replacement of celestite single crystals by strontianite aggregates: Pseudomorphisation and porosity generation

Celestite (SrSO4) single crystals immersed in highly concentrated Na2CO3 aqueous solutions (0.5 mol/l) are progressively pseudomorphised by aggregates of strontianite (SrCO3) crystals at ambient conditions. This replacement occurs by the coupling of dissolution and crystallisation reactions, eventually resulting in the formation of strontianite pseudomorphs, which reproduce the external shape of the initial celestite crystals. Experiments conducted for different reaction times indicate that the kinetics of the replacement reaction is mainly controlled by both the dissolution of the celestite substrate and the evolution of the porosity of the strontianite replacing layer. Such a porous layer allows the replacing solution to permeate towards the replacement front. During the initial stages of pseudomorph formation, the strontianite replacing layer is highly porous and the replacement front advances rapidly. As porosity decreases after a few days of reaction, the advancement of the strontianite replacement front slows down and an almost constant rate of about 0.3 µm/h is reached. Scanning electron microscope images and X-ray diffraction data have also shown that the growth of replacing strontianite aggregates occurs with a high degree of orientation with respect to the celestite substrate, i.e. the replacement is topotaxial.

Insights into the Confined Crystallization in Microfluidics of Amorphous Calcium Carbonate

As a precursor phase, amorphous calcium carbonate (ACC) plays a key role in the formation of CaCO3 biominerals, but the detailed information about the structure evolution during the crystallization process of ACC is limited. Herein, based on the confined environment in microfluidics, we have demonstrated a strategy to investigate the crystallization processes of ACC. The characteristics of a confined environment in microfluidics were analyzed through COMSOL Multiphysics simulations. By mixing equimolar CaCl2 and Na2CO3 aqueous solutions directly, the reactive crystallization of CaCO3 was monitored on chip by online microscope observation and micro Raman spectroscopy scanning. Combined with offline scanning electron microscopy characterization, we showed that branched aggregate ACC(I) precipitated first once mixing reactant solutions, then the more ordered and whiskerlike ACC(II) was an unexpected result. These whiskerlike ACC(II) either gradually transformed to spherical structure nanocrystalline, vaterit...

A novel route to prepare the metastable vaterite phase of CaCO3 from CaCl2 ethanol solution and Na2CO3 aqueous solution

Vaterite, the least stable phase among three anhydrous polymorphs of calcium carbonate (CaCO3), was prepared via the reaction between the ethanol solution of calcium chloride (CaCl2) and the aqueous solution of sodium carbonate (Na2CO3), which is named ethanol-calcium method. The effects of aging times and reaction temperatures on the formation of vaterite were investigated. The polymorphs and morphologies were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, and Fourier transform infrared spectroscopy (FT-IR) was used to verify the existence of vaterite. XRD results indicate that the amount of vaterite decreases from 90.4% to 81.4% as increasing in aging times from 0 min to 42 h and decreases from 85.8% to 70.2% as increasing in reaction temperatures from 0 °C to 60 °C. SEM results show that vaterite and calcite as-prepared are their typical morphologies of spherical and rhombohedral, respectively. This research extends the route to prepare the metastable vaterite and provides new insights into its controllable synthesis.

Preparation of Dodecyl Dimethyl Benzyl Ammonium Bromide-Doped Cubic CaCO3 with Antibacterial Properties

CaCl2 encapsulated was placed in the hydrothermal reactor of an aqueous solution of Na2CO3 and dodecyl dimethyl benzyl ammonium bromide for synthesis of two samples of calcium carbonate by an improved hydrothermal method and one-pot method. Their crystal structure, morphology, chemical composition, and thermal stability of the synthesized samples of calcium carbonate were investigated by XRD, FTIR, SEM, EDS and TGDSC. The sterilization activity of the as-prepared samples was evaluated by killing of Sarcina lutea bacteria. The results indicated that the regular cube capsule-assisted calcium carbonate prepared by hydrothermal process was doped with dodecyl dimethyl benzyl ammonium bromide. Under the same condition, the spindle-shaped calcium carbonate synthesized the one-pot method was not doped with dodecyl dimethyl benzyl ammonium bromide. Among the samples of calcium carbonate, capsule-assisted calcium carbonate had shown better antibacterial effect for Sarcina lutea: in 48 h after its inhibition a zone diameter was 12.3 mm.

Facile-fabricated iron oxide nanorods as a catalyst for hydrogenation of nitrobenzene

β-FeOOH nanorods were prepared by a poly ethylene glycol (PEG) assisted precipitation of FeCl3 ∙ 6H2O aqueous solution with urea. Na2CO3 aqueous solution was introduced to maintain their shapes under annealing. The one-dimensional porous iron oxide nanorods were synthesized successfully. The as-prepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The hydrogenation of nitrobenzene to aniline was taken as probe reaction to evaluate their catalytic performance. FeOOH (iron oxides hydroxide) nanorods, fabricated by annealing β-FeOOH nanorods at 250°C in Ar atmosphere for 4h, exhibited high catalytic activity for the transfer hydrogenation of nitrobenzene to aniline with hydrazine hydrate as hydrogen donors.

Calcium carbonate-methylene blue nanohybrids for photodynamic therapy and ultrasound imaging.

Photodynamic therapy plays an important role in cancer treatment. In this work, methylene blue (MB)-embedded calcium carbonate nanorods (CaCO3-MB NRs) have been synthesized for pH-responsive photodynamic therapy and ultrasound imaging. The morphology of CaCO3-MB NRs can be controlled by modulating the concentration of Na2CO3 aqueous solution. The generation of effective reactive oxygen species (ROS) were confirmed by 1,3-diphenylisobenzofuran (DPBF) probe. Both photodynamic therapy performance and echogenic performance of CaCO3-MB NRs were investigated to confirm the feasibility of CaCO3-MB nanohybrids for ultrasound image-guided photodynamic therapy.

Effective removal of Congo red using sunflower oil/tri-n-octylamine system in a bulk liquid membrane process and studying the transport kinetics

The present work highlights effective transport and removal of Congo red (CR) from its model solution using sunflower oil/tri-n-octylamine (TOA) system in bulk liquid membrane (BLM) transport. Aqueous solution of Na2CO3 with 1 M solution strength was found to be an effective stripping medium for the anionic dye transport. Maximum extraction and recovery percentages of 99.9 and 75.6% were achieved when optimum manifold operating conditions were: 4 vol.% TOA, 2 ± 0.1 feed phase pH, 300 rpm stirring speed, at 40 °C temperature with 8 h, equilibrium time. Kinetic estimation of data with higher rate constants for extraction vis-a-vis stripping operation throughout various experimental conditions suggested that CR transport across sunflower oil/TOA BLM system was governed by stripping process. Activation energies for extraction and stripping operations were found to be 45.92 and 74.05 kJ mol−1, respectively. This led to a conclusion that the rate determining step for extraction was intermediate controlled whereas for stripping it was chemical reaction rate controlled. Finally, spectral studies (UV–vis and FT-IR) were carried out to confirm and validate the recovery of CR.

A facile route to batch synthesis CuO hollow microspheres with excellent gas sensing properties

CuO hollow microspheres had been batch synthesized by a facile route of precipitating and annealing at 270 °C, which was derived from CuSO4·5H2O, Na2CO3 and CTAB. The morphology and structure of synthesized CuO powder were characterized by XRD, SEM, UV–Vis and BET. The formation mechanism of CuO hollow microspheres had been proposed based on the characterized structure and morphology. Firstly, the tiny Cu2(OH)2CO3 crystal strips are formed from CuSO4 and Na2CO3 aqueous solutions. Secondly, the tiny Cu2(OH)2CO3 crystal strips are assembled perpendicularly to the spherical CTA+ micelles surface due to the template of CTAB. Finally, the CuO hollow microspheres have been obtained due to the decomposition of Cu2(OH)2CO3 and burning of CTAB after annealing at 270 °C. High gas sensitivity to ethanol was achieved for the CuO hollow microspheres. The response of CuO hollow microspheres sensor is 5.6 to ethanol with the concentration of 400 ppm at 250 °C, and the responses/recover time is 17.0/11.9 s. Therefore, it indicates that the facile and batch route is a promising method to synthesize CuO hollow microspheres with excellent gas sensing properties.

CO2 capture by aqueous Na2CO3 integrated with high-quality CaCO3 formation and pure CO2 release at room conditions

The absorption of carbon dioxide from anthropogenic emissions and its utilization as a building block for the synthesis of useful chemicals is gaining increasing interest in recent years as an alternative to the conventional CO2 capture and storage (CCS) technologies. The conversion of carbon dioxide into valuable commodities has the advantage of avoiding the energy penalties of absorbent regeneration, CO2 compression and its disposal underground.In this paper we report a novel semi-continuous technique of CO2 capture from a gas mixture by dilute (0.83moldm−3) aqueous solutions of Na2CO3 with a sufficiently high absorption efficiency (about 80%) combined with the nearly quantitative production of high quality CaCO3 and CO2 minimizing the energy requirements since the entire process occurred at room conditions. The highly pure CaCO3 and CO2 recovered by the process are valuable products that have the potential of reducing the costs of the CO2 capture process. The 13C NMR spectroscopy is employed to identify and quantify the species in solution.

Basic anion-exchange resin (AER)-supported Au-Pd alloy nanoparticles for the oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid (FDCA)

Au-Pd alloy nanoparticles supported on basic anion-exchange resin (AER) have exceptional catalytic activity for the oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid (FDCA) with an equimolar amount of base. SEM-EDX and TEM analyses show that 5–20nm Au-Pd alloy nanoparticles are well dispersed both on the resin surface and inside resin spheres by a simple procedure without any assistance of additives. XPS analysis reveals that Au- and Pd metals exist in an alloy form on the AER support, which is confirmed by a comparison study with a mixture of AER-supported monometallic nanoparticles (AER-supported Au and AER-supported Pd). In the presence of a 1:1 ratio of Au-Pd alloy nanoparticles over Amberlite IRA-743 resin with O2 (10bar) at 373K in an equimolar Na2CO3 aqueous solution, HMF is oxidized to FDCA with a 93.2% yield. On the other hand, mixture of AER-supported Au and AER-supported Pd affords only a 52% FDCA yield under identical conditions. This catalyst can be used 6 times without any significant loss of activity. FDCA is also obtained from HMF with an 82.9% yield in air (40bar).

Dual Electrolytic Plasma Processing for Steel Surface Cleaning and Passivation

To remove the rust on rebars and passivate the fresh surfaces, electrodes reversing electrolytic plasma processing (EPP) was proposed and conducted in a 10 wt.% Na2CO3 aqueous solution. The morphology and the composition of the surface were investigated by SEM and XPS. Experimental results show that the rust on the surface was removed effectively by cathode EPP, and a passive film containing Cr2O3 was achieved by the succeeding anode EPP treatment, by a simple operation of reversing the bias. The corrosion resistance was evaluated in a 3.5 wt.% NaCl aqueous solution using an electrochemical workstation. In comparison, the corrosion resistance was improved by the succeeding anode EPP treatment, which is evidenced by a positive shift of the open-circuit potential, an increase in the electrochemical impedance representing the inner layer by 76.8% and the decrease in the corrosion current density by 49.6%. This is an effective and environment-friendly technique to clean and passivate rebars and similar steel materials.

A Facile Method To Prepare Novel Ag2O/Ag2CO3 Three-Dimensional Hollow Hierarchical Structures and Their Water Purification Function

A facile, green, and low-cost method to prepare novel Ag2O/Ag2CO3 three-dimensional hollow flowerlike hierarchical microspheres has been demonstrated. The microspheres were obtained by simple injection of Na2CO3 aqueous solution into AgNO3 ethanol solution. The surface morphology of the microspheres was relatively smooth, trumpet flowerlike hole, and flowerlike shallow hole when the reaction temperature was 8, 25, and 70 °C, respectively. They were assembled by nanoparticles. The microsphere prepared at 25 °C was composed of 86.3% Ag2CO3 and 13.7% Ag2O. The HTEM image indicates that the Ag2CO3 microsphere is wrapped by a thin Ag2O layer, and there is a heterojunction between Ag2CO3 and Ag2O. The study of the formation mechanism demonstrates the first example of using water-soluble Na2CO3 as templates to prepare 3D hierarchical microstructures. The Ag2O/Ag2CO3 microspheres prepared at 25 °C have excellent adsorption and photocatalysis activity for Congo red (CR). The adsorption behavior of the Ag2O/Ag2CO3 ...

Reaction pathways and textural aspects of the replacement of anhydrite by calcite at 25 °C

The replacement of sulfate minerals by calcium carbonate polymorphs (carbonation) has important implications in a variety of geological processes occurring in Earth surface environments. In this paper we report the results of an experimental study of the interaction between anhydrite (100), (010) and (001) surfaces and Na2CO3 aqueous solutions under ambient conditions. Carbonation progress was monitored by glancing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM). We show that the reaction progresses through the dissolution of anhydrite and the simultaneous growth of calcite. The growth of calcite occurs oriented on the three anhydrite cleavage surfaces and its formation is accompanied by minor vaterite. The progress of the carbonation always occurs from the outer-ward to the inner-ward surfaces and its rate depends on the anhydrite surface considered, with the (001) surface being much more reactive than the (010) and (100) surfaces. The thickness of the formed carbonate layer grows linearly with time. The original external shape of the anhydrite crystals and their surface details (e.g., cleavage steps) are preserved during the carbonation reaction. Textural characteristics of the transformed regions, such as the gradation in the size of calcite crystals, from ~2 µm in the outer region to ~17 µm at the calcite-anhydrite interface, the local preservation of calcite crystalographic orientation with respect to anhydrite and the distribution of the microporosity mainly within the carbonate layer without development of any significant gap between at the calcite-anhydrite interface. Finally, we compare these results on anhydrite carbonation with those on gypsum carbonation and can explain the differences on the basis of four parameters: (i) the molar volume change involved in the replacement process in each case, (ii) the lack/existence of epitactic growth between parent and product phases, (iii) the kinetics of dissolution of the different surfaces, and (iv) the chemical composition (amount of structural water) of the parent phases.