Reaction Of CaCO3 Research Articles

Determination of calcium and sulfate species in aerosols associated with the conversion of its species through reaction processes in the atmosphere and its influence on cloud condensation nuclei activation

Calcium (Ca) species in aerosols collected in Higashi–Hiroshima in southwestern Japan were determined by X-ray absorption near-edge structure (XANES) analysis, and their size distributions and seasonal variation were investigated. Calcium K-edge XANES results showed that gypsum (CaSO4⋅2H2O) and calcium oxalate (CaC2O4⋅2H2O) were the major Ca species that were formed by reactions of mineral particles in the atmosphere. These species exhibit similar hygroscopicity to that of calcite (CaCO3), which is an original Ca species in mineral particles. In addition, high hygroscopic Ca species, such as calcium nitrate [Ca(NO3)2⋅4H2O] and calcium chloride (CaCl2⋅2H2O) were considered minor Ca species. Moreover, the formation of CaSO4⋅2H2O by the reaction of mineral particles suppresses the formation of hygroscopic sulfate aerosol species, such as ammonium sulfate [(NH4)2SO4], reducing the number of cloud condensation nuclei (CCN). Sulfur K-edge XANES also confirmed that CaSO4⋅2H2O was a major species of sulfate in coarse particles. By contrast, high hygroscopic sulfate, such as (NH4)2SO4, was major species in fine particle. In addition, CaSO4⋅2H2O fraction to total sulfate increased during the sampling period, which was affected by a dust event. Consequently, the amount of hygroscopic sulfate in fine particles was decreased by the reaction, forming CaSO4⋅2H2O in coarse particles in the presence of mineral dust. Although these facts have been indicated mostly by modeling and laboratory studies, the present research suggested that the reaction of CaCO3 to form CaSO4⋅2H2O will reduce the amount of hygroscopic sulfate aerosols based on natural sample measurement in terms of the speciation of Ca and sulfate in aerosols using XANES spectroscopy.

Ablative Properties of Calcium Carbonate-Filled Phenolic Matrix Composite Coatings Irradiated by High Energy Continuous-Wave Laser

Laser, especially high energy continuous-wave (CW) laser, can destroy traditional structure material of aircrafts or vehicles easily. Therefore, anti-laser damage is gradually becoming a major concern. In this case, calcium carbonate (CaCO3)-filled phenolic matrix composite coatings have been designed and prepared to prevent from high energy CW laser damage. Laser ablation behavior of the coating is deeply studied by varying the laser parameters including laser power density and irradiation time. The results show that the phenolic resin keeps decomposing into residual char caused by the high temperature during laser irradiation. The porous structure of phenolic resin of residual char provides an excellent thermal insulation property for the coating. In addition, the decomposition reaction of CaCO3 consumes a large amount of laser energy, which has a cooling effect on the residual char. CaO that is produced during the decomposition of CaCO3 has a high melting temperature and can lead to the thermal stability improvement of the residual char. Due to the introduction of CaCO3, the back-surface temperature of sample is decreased from 94 °C to 64 °C when irradiated at 500 W/cm2 for 10 s and the anti-laser property of the coating is improved. All the analysis indicate that the designed coating can perform as a shield to prevent from high energy CW laser.

Predicting Weathering Characteristics of Carbonate Rocks Under Different Geo-Environmental Conditions

Rock moisture content, temperature and physical and chemical conditions of water in the rock mass vary under different geoenvironmental conditions. These factors are critical in the mechanical and chemical disintegration of rocks with time. Changes in weathering characteristics of a rock mass correlate with major changes in shear strength and deformability of rocks. Therefore, durability is an important parameter for rocks and weathered rocks in predicting and assessing long term problems in their use for engineering purposes. Carbonate rocks are generally considered as durable strong rocks. It is important to test this claim in the UAE, where carbonate rocks are the main available rock materials in many locations e.g. in Al Ain city. The slake durability index (SDI), with tests involving several cycles of wetting and drying, is widely recognized and has been used to measure the durability of weathered rocks. Carbonate rocks in the Jabel Hafit mountain, Al Ain region, have highly fractured and cavernous surface and near surface structures. In this study, degradability of samples from three different carbonate sequences: the Rus, Dammam, and Asmari Formations, were studied petrographically, mineralogically and texturally before and after slaking. A number of slaking tests were performed on twenty-one rock samples, seven from each rock formation, in order to investigate the effects of various geoenvironmental conditions on carbonate rocks weatherability at various pH levels 2, 4, 6, 8, 10, 12 and 14. Detailed mineralogical examinations, rock thin sections, Scanning Electronic Microscope (SEM) and X-ray diffractometry (XRD) were employed to reveal the relationship between mineralogy and weathering characteristics of rocks on the representative rock samples, before and after the slake durability tests. Furthermore, the index properties of all samples such as unit weights (dry, γd and saturated, γsat), the water absorption (Wa), the porosity (n), void ratio (e) and the specific gravities (GS,(OD), GS,(SSD), GS,(A)) were measured. The study reveals that the weathering characteristics of carbonate rocks under different geoenvironmental conditions is strongly controlled by the mineralogical composition and textural features of the rocks. The impact of slaking fluid in the degradability of limestone is very limited due to chemical reaction of CaCO3 especially in lower pH level acidic fluid, which reduced the bonding strength between grains. The findings will certainly help to resolve durability problems associated with engineering applications such as tunnels, slope stability, and etc. in the region and elsewhere.

Preparation and characterization of PVDF/CaCO3 composite membranes etched by hydrochloric acid.

This study aimed to improve the pore size, porosity, and hydrophobicity of polyvinylidene fluoride (PVDF) membranes for desalination by vacuum membrane distillation (VMD). New membranes were prepared via etching PVDF/calcium carbonate (CaCO3) composite membranes using hydrochloric acid (HCl), depending on the chemical reaction of CaCO3 and HCl. Etched membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), contact angle (CA), atomic force microscope (AFM), and scanning electron microscopy (SEM). The results showed that CaCO3 of composite membranes was completely reacted by 1.5 mol/L HCl after composite membranes had been etched 90 min. The crystallinity of etched membranes was the same as that of PVDF/CaCO3 composite membranes, and no new functional groups appeared in etched membranes, which indicated that etched membranes had good chemical stability. The surface roughness increased and led to the increase of contact angle, which means the hydrophobicity of etched membranes was enhanced. As a result, the increment of permeation flux had been improved in a VMD process. It was found that the maximum flux of etched membrane was enhanced and up to 1.65 times of composite membrane when the concentration of sodium chloride (NaCl) solution was 5.0 wt%, and the maximum flux reached up to 30.9 kg m-2 h-1.

Evolution of diamond-forming systems of the mantle transition zone: ringwoodite peritectic reaction (Mg,Fe)2SiO4 (experiment AT 20 GPa)

The peritectic reaction of ringwoodite (Mg,Fe)2SiO4 and silicate-carbonate melt with formation of magnesiowustite (Fe,Mg)O, stishovite SiO2 and Mg, Na, Ca, K-carbonates is revealed by experimental study at 20 GPa of melting relations of the multicomponent MgO-FeO-SiO2-Na2CO3-CaCO3-K2CO3 system of the Earth’s mantle transition zone. A reaction of CaCO3 and SiO2 with the formation of Ca-perovskite CaSiO3 is also detected. It is shown that the peritectic reaction of ringwoodite and melt with the formation of stishovite physic-chemically controls the fractional ultrabasic-basic evolution of both magmatic and diamond-forming systems of the deep horizons of the transition zone up to its boundary with the Earth’s lower mantle.

Surface chemistry, rheology and microstructure of as-received SHCa-1 hectorite gels

AbstractThe zeta potential and yield-stress behaviour of gels prepared from as-received SHCa-1 hectorite (Ht) containing 50 wt.% impurities, mainly of calcite, dolomite and quartz, were characterized. The zeta potential is negative in the pH range 4–12. At pH <5, reaction of CaCO3 producing CO2 and Ca2+ increased the solution conductivity significantly and reduced the zeta potential. The buffering effect due to this chemical reaction was also observed in the yield stress–pH characterization below pH 8. Low yield stress was observed below pH 6 and above pH 12. The yield stress peaked at pH ~8, where Ht displayed a zeta potential of –20 mV. The relationship between maximum yield stress and Ht content (wt.%) was linear and was not affected by impurities. The ageing behaviour was characterized by an initial phase of rapid yield-stress increase and then by a phase of gradual increase. The Leong model performed better than the two-parameter glassy polymer ageing model in describing this ageing behaviour. However, the empirical power law model was more accurate. The timescale of the ageing process is long, lasting several days. An open cellular microstructure was observed to form in the gels. Impurities appeared not to interact with or bind to the Ht platelets.

Evidence of impact melting and post-impact decomposition of sedimentary target rocks from the Steen River impact structure, Alberta, Canada

Hypervelocity bolide impacts deliver vast amounts of energy to the Earth's near surface. This crustal process almost universally includes sedimentary target rocks; however, their response to impact is poorly understood, in part because of complexities due to layering, pore space and the presence of volatiles that are difficult to model. The response of carbonates to bolide impact remains contentious, yet whether they melt or decompose and liberate gases by the reaction CaCO3(s) → CaO(s) + CO2(g)↑, has significant implications for post-impact climatic effects. We report on previously unknown carbonate impact melts at the Steen River impact structure, Canada, and the first description of naturally shocked barite, BaSO4. Carbonate melts are preserved as groundmass-supported calcite-rich clasts, sampled from an up to 164 m thick, continuous sequence of crater-fill polymict breccias. Electron microscopy reveals fluidal- and ocellar-textured calcite and barite, intimately associated with silicate melt, consistent with these phases being in the liquid state at the same time. Raman spectroscopy and electron backscatter diffraction (EBSD) mapping confirm the presence of high-pressure phases – reidite and coesite – within some Steen River carbonate melt-bearing breccias. These minerals attest to the strong shock provenance of the breccia and provide constraints on their shock history. Preservation of reidite lamellae in zircon indicates a shock pressure >30 GPa <60 GPa and temperatures <1473 K. In addition to melting, we present compelling evidence for widespread (70–100%) decomposition of carbonate target rocks, mixed as lithic clasts into hot impact breccias. In this context, decomposition occurs strictly post-impact due to thermal equilibration-related heating. We demonstrate that this mechanism for CO2 outgassing is likely more widespread than previously recognized. The presence of andradite-grossular garnet serve as mineralogical markers of decomposition, analogous to limestone-replacing skarn deposits. Ca-rich garnet may therefore prove an important indicator mineral for post-shock decomposition of carbonate-bearing target rocks at other craters. These findings significantly advance our understanding of how sedimentary rocks respond to hypervelocity impact, and have wide-reaching implications for estimating the amount and timing of climatically-active volatile release due to impact events.

SYNTHESIS AND CHARACTERIZATION OF FEED GRADE MONOCALCIUM PHOSPHATE, Ca(H2PO4)2·H2O IN AQUEOUS MEDIUM

The feed grade monocalcium phosphate monohydrate, Ca(H2PO4)2·H2O was prepared by the reaction of CaCO3 and H3PO4 at elevated temperature in aqueous solution. The obtained precipitates were characterized by powder X-ray diffraction, infrared spectroscopy (FTIR), and thermal analysis (TG, DTA) techniques. The chemical composition of final products was evaluated by analysing the phosphorus and calcium content in the samples.

Polyelectrolyte microcapsules built on CaCO3 scaffolds for the integration, encapsulation, and controlled release of copigmented anthocyanins

The all-polysaccharide based polyelectrolyte microcapsules combining copigmentation for anthocyanin encapsulation and stabilization were fabricated. Copigmented complexes of chondroitin sulfate and anthocyanin were preloaded in CaCO3 scaffold, and then microcapsules were created by coating the sacrificial CaCO3 using layer-by-layer technique. It was observed that the preloading of copigmented complex affected the precipitation reaction of CaCO3 and the subsequent entrapment of anthocyanin. With addition of anthocyanin from 0.125 to 0.75 mg, copigmentation can significantly increase the encapsulation efficiency of anthocyanin in CaCO3, whereas such effect was not obvious at higher loadings. The leakage of anthocyanin during CaCO3 core dissolution and storage was also inhibited by two polysaccharide layers coupled with copigmentation, which may be related to the formation of interconnecting networks. Additionally, a higher anthocyanin antioxidant activity was provided by carbohydrate matrix. These findings may allow for the encapsulation of large amounts of water-soluble components; particularly natural colorant by copigmented complex-polyelectrolyte structures.

ChemInform Abstract: Synthesis and Photoluminescence Properties of Ca2Ga2SiO7:Eu3+ Red Phosphors with an Intense 5D0→7F4 Transition.

AbstractNew red emitting title phosphors with different Eu3+ contents are prepared by solid state reaction of CaCO3, Ga2O3, SiO2, and Eu2O3 (air, 1350 °C, 24 h).

ChemInform Abstract: Resonant Energy Transfer in (Eu3+, Bi3+)‐Codoped CaZrO3 Red‐Emitting Phosphor.

AbstractThe title phosphor is synthesized by solid state reaction of CaCO3, ZrO2, Eu2O3, and Bi2O3 (alumina crucible, 300—1200 °C, 1 h in air).

Heterogeneous reactions of NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; with CaCO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;–(NH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;)&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; mixtures at different relative humidities

Abstract. In this work, the heterogeneous reactions of NO2 with CaCO3–(NH4)2SO4 mixtures with a series of weight percentage (wt %) of (NH4)2SO4 were investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different relative humidity (RH) values. For comparison, the heterogeneous reactions of NO2 with pure CaCO3 particles and pure (NH4)2SO4 particles, as well as the reaction of CaCO3 with (NH4)2SO4 particles, were also studied. The results indicated that NO2 did not show any significant uptake on (NH4)2SO4 particles, and it reacted with CaCO3 particles to form calcium nitrate under both dry and wet conditions. The heterogeneous reactions of NO2 with CaCO3–(NH4)2SO4 mixtures were markedly dependent on RH. Calcium nitrate was formed from the heterogeneous reactions at all the RHs investigated, whereas CaSO4 ⋅ 0.5H2O (bassanite), CaSO4 ⋅ 2H2O (gypsum), and (NH4)2Ca(SO4)2 ⋅ H2O (koktaite) were produced depending on RH. Under the dry condition, the heterogeneous uptake of NO2 on the mixtures was similar to that on CaCO3 particles with neglectable effects from (NH4)2SO4; the duration of initial stages and the NO3− mass concentrations had a negative linear relation with the mass fraction of (NH4)2SO4 in the mixtures. Under wet conditions, the chemical interaction of (NH4)2SO4 with Ca(NO3)2 enhances the nitrate formation, especially at medium RHs, while the coagulation of (NH4)2SO4 with CaCO3 exhibits an increasing inhibiting effects with increasing RH at the same time. In addition, the heterogeneous uptake of NO2 on the mixtures of CaCO3 and (NH4)2SO4 was found to favor the formation of bassanite and gypsum due to the decomposition of CaCO3 and the coagulation of Ca2+ and SO42−. A possible reaction mechanism was proposed and the atmospheric implications were discussed.

Simulation of the calcination of a core-in-shell CuO/CaCO3 particle for Ca–Cu chemical looping

The internal heat balance through heat generation due to CuO reduction and its consumption by CaCO3 decomposition makes calcination a critical step in a novel Ca–Cu chemical looping process (CaL–CLC). Thus, the calcination behaviour of composite Ca/Cu particles needs to be well understood, especially taking into account that mismatching of heat generation and consumption in the particles can lead to local superheating, agglomeration and loss of activity due to enhanced sintering. In this work, a composite particle model was developed to study the calcination behaviour within a spherical core-in-shell type of particle containing grains of CuO and CaCO3. Simulation results showed that ambient temperature, shell porosity, particle size, and CaCO3 grain size significantly affected the CuO and CaCO3 reaction processes, while the impact of initial particle temperature and CuO grain size can be ignored in the range of parameters considered in the study. By comparison of different types of particles, it was concluded that the core-in-shell pattern was more advantageous if such particles are being applied in CaL–CLC cycles due to better matching in reaction kinetics resulting in more stable and uniform particle temperature distribution during the calcination stage.

Hydration of ternary cement in the presence of triisopropanolamine

The effects of triisopropanolamine (TIPA) on the strength development and hydration kinetics of a ternary cement containing slag and CaCO3 were investigated by mixture design. The strength development of the blend was considerably enhanced by the accelerated chemical reactions on each component. A very strong interaction effect of slag and CaCO3 on the strength enhancement prior to 7d was observed. The addition of TIPA promoted the hydration of laboratory cement by promoting the dissolution of ferrite, which resulted in more CH being released to participate in the reaction with slag. The dissolution of the slag itself was markedly accelerated by TIPA in a simulated highly alkaline pore solution. The use of TIPA promoted the formation of carboaluminate due to the accelerated C4AF/C3A–CaCO3 reaction, which stabilized the formation of AFt during hydration. In addition, it confirmed that Fe ions were able to enter the AFt structure during hydration with TIPA.

ChemInform Abstract: Ca6BaP4O17:Eu2+,Gd3+: A Yellow Emitting Long‐Lasting Phosphor with High Brightness and Long Afterglow Duration.

AbstractA series of phosphors, Ca6BaP4O17:0.02Eu2+,xGd 3+ (x = 0, 0.005, 0.01, 0.015, 0.02, 0.025) is synthesized by solid state reaction of CaCO3, BaCO3, NH4H2PO4, Gd2O3, and Eu2O3 (alumina crucible, 5% H2/N2 stream, 1280 °C, 10 h).

ChemInform Abstract: Tunable Color and Energy Transfer in Single‐Phase White‐Emitting Ca20Al26Mg3Si3O68 :Ce3+,Dy3+ Phosphors for UV White Light‐Emitting Diodes.

AbstractCa20Al26Mg3Si3O68 :xCe3+,yDy3+ (x = 0.02‐0.12; y = 0‐0.09) phosphors are prepared by solid state reaction of CaCO3, Al2O3, MgO, SiO2, Li2CO3 (as charge compensator for the lanthanoide dopants), CeO2, and Dy2O3 in stoichiometric amounts (corundum crucible, 5% H2/N2, 1400 °C, 2 h).

On reactive suspension plasma spraying of calcium titanate

This study shows possibility of preparation of calcium titanate powder and coatings by reactive suspension plasma spraying. Suspension of mixture of calcium carbonate (CaCO3) and titanium dioxide (TiO2) powders in ethanol was fed into hybrid plasma torch with a DC-arc stabilized by a water–argon mixture (WSP®-H 500). Various feeding distances and angles were used in order to optimize suspension feeding conditions. In the next step, the coatings were deposited on stainless steel substrates and the effect of substrate temperature on microstructure and chemical and phase composition of the coatings was studied. Captured in-flight particles and deposits were analysed by X-ray diffraction (XRD) and scanning electron microscopy SEM equipped with EDX detector. Obtained results confirm that chemical reaction of CaCO3 and TiO2 forming CaTiO3 perovskite takes place during the interaction of suspension with plasma jet. The conditions of rapid cooling during spraying process result in the presence of metastable CaTiO3 high-temperature tetragonal and cubic phases. Increase in the substrate temperature increases the content of the calcium titanate in the deposit and the coatings microstructure becomes more compact. Obtained results show that WSP®-H technology may be used for deposition of the CaTiO3 powders and coatings by reactive plasma spraying.

ChemInform Abstract: Syntheses, Structure and Magnetic Properties of Two Vanadate Garnets Ca5M4V6O24 (M: Co, Ni).

AbstractCa5M4V6O24 (M: Co, Ni) are prepared by reaction of CaCO3, CoC2O4 or Ni(OAc)2, and V2O5 (alumina crucible, 900 resp.

Sulfation and Carbonation Competition in the Treatment of Flue Gas from a Coal-Based Power Plant by Calcium Hydroxide

Abstract In this work, a gas containing CO2 and SO2 at the usual concentrations on the coal combustion flue gas reacted with calcium hydroxide to evaluate and quantify the influence of SO2 on the CO2 capture and vice versa. This influence was quantified with a continuous gas analyzer and by thermogravimetry (TG). Results show that the CO2 retained increases in general as its concentration does and decreases as the SO2 concentration increases. A similar behavior was found for the SO2 retention at different CO2 concentrations being more relevant the influence of the presence of SO2 on the CO2 capture than the opposite one. Results suggest that for a high CO2 capture, SO2 should be eliminated previously. With respect to the reaction process it was found that the desulfurization product clearly identified was CaSO3·½H2O; in the reaction between Ca(OH)2 and CO2, CaCO3 is mainly obtained, the complex CaO·CO2 being another possible product synthesized in low amount. Gas analyzer shows that SO2 and CO2 react simultaneously and that a part of the CaCO3 reacts with the SO2 and releases CO2. Sulfation values calculated by TG and from the gas analyzer are very similar but the amount of CO2 captured is not possible to know clearly by TG due to the synthesis and decomposition of CaCO3 during the process. The study of the evolution of the sorbent porosity in the process reveals that the presence of both acid gases produces a lower blockage of the pores than when only one gas is present probably due to the generation of new pores in the reaction of CaCO3 and SO2.

Understanding the Enhancement Effect of Na2CO3 Additive on the Direct Sulfation of Limestone

The enhancement effect of Na2CO3 additive on the reaction of CaCO3 with SO2 and O2 at high temperature is a widely observed phenomenon; however, its mechanism remains unclear. From the solid-state physics point of view, this study proposed that the defect formation caused by the additive may explain the enhanced sulfation. The single-crystal CaCO3 with a smooth surface was used as a sample for direct sulfation, and the morphology and Na element distribution was investigated with scanning electron microscopy and energy-dispersive spectroscopy. It is observed that the Na ion will diffuse into CaSO4 during sulfation, and it does not diffuse into the lattice of the CaCO3 crystal by itself. The relationship of the diffusion coefficient in the solid state with the additive fraction was established and integrated into a new sulfation model. This new model included a simplified rate equation model to describe the product island formation and an ionic diffusion model that describes the product-layer growth. The experimental data on the direct sulfation of limestone, with and without additive, were used to validate the newly developed models.