Elements from chlorine to calcium nuclear reactions

CERN Document Server

Kunz, Wunibald

1968-01-01

Nuclear Tables: Part II Nuclear Reactions, Volume 3: The Elements from Chlorine to Calcium contains tabulations of the nuclear reaction values of elements chlorine, argon, potassium, and calcium. These tabulations provide the calculated Q-values of the elements and their isotopes. This book will be of value to general chemistry researchers.

Presence and dehydration of ikaite, calcium carbonate hexahydrate, in frozen shrimp shell.

Science.gov (United States)

Mikkelsen, A; Andersen, A B; Engelsen, S B; Hansen, H C; Larsen, O; Skibsted, L H

1999-03-01

Ikaite, calcium carbonate hexahydrate, has by means of X-ray diffraction analyses of frozen samples been identified as the mineral component of the white spots formed in the shell of frozen shrimp during storage. When the shrimp thaw and the shell material is dried and kept at room temperature, ikaite rapidly transforms into a mixture of anhydrous calcium carbonate forms. X-ray diffraction analyses and Raman spectra of synthetic ikaite as well as the dehydration product confirm the assignments, and the rate constant for dehydration is approximately 7 x 10(-)(4) s(-)(1) at ambient temperature. Differential scanning calorimetry showed that dehydration of synthetic ikaite is an entropy-driven, athermal process and confirms that a single first-order reaction is rate-determining. Ikaite is found to be stable in aqueous solution at temperatures below 5 degrees C and in the shell of frozen shrimps but decomposes on thawing to form anhydrous calcium carbonates.

Viral lysis of photosynthesizing microbes as a mechanism for calcium carbonate nucleation in seawater

Science.gov (United States)

Lisle, John T.; Robbins, Lisa L.

2016-01-01

Removal of carbon through the precipitation and burial of calcium carbonate in marine sediments constitutes over 70% of the total carbon on Earth and is partitioned between coastal and pelagic zones. The precipitation of authigenic calcium carbonate in seawater, however, has been hotly debated because despite being in a supersaturated state, there is an absence of persistent precipitation. One of the explanations for this paradox is the geochemical conditions in seawater cannot overcome the activation energy barrier for the first step in any precipitation reaction; nucleation. Here we show that virally induced rupturing of photosynthetic cyanobacterial cells releases cytoplasmic-associated bicarbonate at concentrations ~23-fold greater than in the surrounding seawater, thereby shifting the carbonate chemistry toward the homogenous nucleation of one or more of the calcium carbonate polymorphs. Using geochemical reaction energetics, we show the saturation states (Ω) in typical seawater for calcite (Ω = 4.3), aragonite (Ω = 3.1), and vaterite (Ω = 1.2) are significantly elevated following the release and diffusion of the cytoplasmic bicarbonate (Ωcalcite = 95.7; Ωaragonite = 68.5; Ωvaterite = 25.9). These increases in Ω significantly reduce the activation energy for nuclei formation thresholds for all three polymorphs, but only vaterite nucleation is energetically favored. In the post-lysis seawater, vaterite's nuclei formation activation energy is significantly reduced from 1.85 × 10−17 J to 3.85 × 10−20 J, which increases the nuclei formation rate from highly improbable (nucleation of calcium carbonate in seawater describes a mechanism through which the initial step in the production of carbonate sediments may proceed. It also presents an additional role of photosynthesizing microbes and their viruses in marine carbon cycles and reveals these microorganisms are a collective repository for concentrated and reactive dissolved inorganic carbon (DIC

Obtainment of calcium carbonate from mussels shell

International Nuclear Information System (INIS)

Hamester, M.R.R.; Becker, D.

2010-01-01

The mussels and oyster shell are discarded at environment, and this accumulation is causing negative consequences to ecosystem. Calcium carbonate is main constituent of the shell chemical composition. Aiming to reduce environmental aggression and generate income to shellfish producer, there was the possibility of using these shells as an alternative to commercial calcium carbonate. For this physics, chemicals and thermal properties were evaluated, using X-ray fluorescence, thermogravimetric analysis, size distribution, abrasiveness and scanning electronic microscopy. The results indicate that mussels shells have an initial degradation temperature higher than commercial calcium carbonate e same lost weight behavior and 95% of shell chemical composition is calcium carbonate. The sample size distribution was influenced by grinding condition and time as well as its abrasiveness. (author)

Preparation, physical-chemical characterisation and cytocompatibility of calcium carbonate cements

OpenAIRE

Combes, Christèle; Miao, Baoji; Bareille, Reine; Rey, Christian

2006-01-01

The feasibility of calcium carbonate cements involving the recrystallisation of metastable calcium carbonate varieties has been demonstrated. Calcium carbonate cement compositions presented in this paper can be prepared straightforwardly by simply mixing water (liquid phase) with two calcium carbonate phases (solid phase) which can be easily obtained by precipitation. An original cement composition was obtained by mixing amorphous calcium carbonate and vaterite with an aqueous medium. The cem...

Oral calcium carbonate affects calcium but not phosphorus balance in stage 3–4 chronic kidney disease

Science.gov (United States)

Hill, Kathleen M.; Martin, Berdine R.; Wastney, Meryl; McCabe, George P.; Moe, Sharon M.; Weaver, Connie M.; Peacock, Munro

2014-01-01

Chronic kidney disease (CKD) patients are given calcium carbonate to bind dietary phosphorus and reduce phosphorus retention, and to prevent negative calcium balance. Data are limited on calcium and phosphorus balance in CKD to support this. The aim of this study was to determine calcium and phosphorus balance and calcium kinetics with and without calcium carbonate in CKD patients. Eight stage 3/4 CKD patients, eGFR 36 mL/min, participated in two 3-week balances in a randomized placebo-controlled cross-over study of calcium carbonate (1500 mg/d calcium). Calcium and phosphorus balance were determined on a controlled diet. Oral and intravenous 45calcium with blood sampling and urine and fecal collections were used for calcium kinetics. Fasting blood and urine were collected at baseline and end of each week of each balance period for biochemical analyses. Results showed that patients were in neutral calcium and phosphorus balance while on placebo. Calcium carbonate produced positive calcium balance, did not affect phosphorus balance, and produced only a modest reduction in urine phosphorus excretion compared with placebo. Calcium kinetics demonstrated positive net bone balance but less than overall calcium balance suggesting tissue deposition. Fasting biochemistries of calcium and phosphate homeostasis were unaffected by calcium carbonate. If they can be extrapolated to effects of chronic therapy, these data caution against the use of calcium carbonate as a phosphate binder. PMID:23254903

Hydrophobic Calcium Carbonate for Cement Surface

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Shashi B. Atla

2017-12-01

Full Text Available This report describes a novel way to generate a highly effective hydrophobic cement surface via a carbonation route using sodium stearate. Carbonation reaction was carried out at different temperatures to investigate the hydrophobicity and morphology of the calcium carbonate formed with this process. With increasing temperatures, the particles changed from irregular shapes to more uniform rod-like structures and then aggregated to form a plate-like formation. The contact angle against water was found to increase with increasing temperature; after 90 °C there was no further increase. The maximum contact angle of 129° was obtained at the temperature of 60 °C. It was also found that carbonation increased the micro hardness of the cement material. The micro hardness was found to be dependent on the morphology of the CaCO3 particles. The rod like structures which caused increased mineral filler produced a material with enhanced strength. The 13C cross polarization magic-angle spinning NMR spectra gave plausible explanation of the interaction of organic-inorganic moieties.

Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

Science.gov (United States)

Blättler, Clara L.; Higgins, John A.

2017-12-01

Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

Preparation, physical-chemical characterisation and cytocompatibility of calcium carbonate cements.

Science.gov (United States)

Combes, C; Miao, Baoji; Bareille, Reine; Rey, Christian

2006-03-01

The feasibility of calcium carbonate cements involving the recrystallisation of metastable calcium carbonate varieties has been demonstrated. Calcium carbonate cement compositions presented in this paper can be prepared straightforwardly by simply mixing water (liquid phase) with two calcium carbonate phases (solid phase) which can be easily obtained by precipitation. An original cement composition was obtained by mixing amorphous calcium carbonate and vaterite with an aqueous medium. The cement set and hardened within 2h at 37 degrees C in an atmosphere saturated with water and the final composition of the cement consisted mostly of aragonite. The hardened cement was microporous and showed poor mechanical properties. Cytotoxicity tests revealed excellent cytocompatibility of calcium carbonate cement compositions. Calcium carbonates with a higher solubility than the apatite formed for most of the marketed calcium phosphate cements might be of interest to increase biomedical cement resorption rates and to favour its replacement by bone tissue.

Viral lysis of photosynthesizing microbes as a mechanism for calcium carbonate nucleation in seawater

Science.gov (United States)

Lisle, John T.; Robbins, Lisa L.

2016-01-01

Removal of carbon through the precipitation and burial of calcium carbonate in marine sediments constitutes over 70% of the total carbon on Earth and is partitioned between coastal and pelagic zones. The precipitation of authigenic calcium carbonate in seawater, however, has been hotly debated because despite being in a supersaturated state, there is an absence of persistent precipitation. One of the explanations for this paradox is the geochemical conditions in seawater cannot overcome the activation energy barrier for the first step in any precipitation reaction; nucleation. Here we show that virally induced rupturing of photosynthetic cyanobacterial cells releases cytoplasmic-associated bicarbonate at concentrations ~23-fold greater than in the surrounding seawater, thereby shifting the carbonate chemistry toward the homogenous nucleation of one or more of the calcium carbonate polymorphs. Using geochemical reaction energetics, we show the saturation states (Ω) in typical seawater for calcite (Ω = 4.3), aragonite (Ω = 3.1), and vaterite (Ω = 1.2) are significantly elevated following the release and diffusion of the cytoplasmic bicarbonate (Ωcalcite = 95.7; Ωaragonite = 68.5; Ωvaterite = 25.9). These increases in Ω significantly reduce the activation energy for nuclei formation thresholds for all three polymorphs, but only vaterite nucleation is energetically favored. In the post-lysis seawater, vaterite's nuclei formation activation energy is significantly reduced from 1.85 × 10−17 J to 3.85 × 10−20 J, which increases the nuclei formation rate from highly improbable (seawater describes a mechanism through which the initial step in the production of carbonate sediments may proceed. It also presents an additional role of photosynthesizing microbes and their viruses in marine carbon cycles and reveals these microorganisms are a collective repository for concentrated and reactive dissolved inorganic carbon (DIC) that is currently not accounted for

Mineral carbonation of gaseous carbon dioxide using a clay-hosted cation exchange reaction.

Science.gov (United States)

Kang, Il-Mo; Roh, Ki-Min

2013-01-01

The mineral carbonation method is still a challenge in practical application owing to: (1) slow reaction kinetics, (2) high reaction temperature, and (3) continuous mineral consumption. These constraints stem from the mode of supplying alkaline earth metals through mineral acidification and dissolution. Here, we attempt to mineralize gaseous carbon dioxide into calcium carbonate, using a cation exchange reaction of vermiculite (a species of expandable clay minerals). The mineralization is operated by draining NaCI solution through vermiculite powders and continuously dropping into the pool of NaOH solution with CO2 gas injected. The mineralization temperature is regulated here at 293 and 333 K for 15 min. As a result of characterization, using an X-ray powder diffractometer and a scanning electron microscopy, two types of pure CaCO3 polymorphs (vaterite and calcite) are identified as main reaction products. Their abundance and morphology are heavily dependent on the mineralization temperature. Noticeably, spindle-shaped vaterite, which is quite different from a typical vaterite morphology (polycrystalline spherulite), forms predominantly at 333 K (approximately 98 wt%).

The formation reaction of calcium hexa-aluminate

International Nuclear Information System (INIS)

Tuganova, S.Kh.; Sirajiddinov, N.A.

1990-01-01

The formation reaction of CaAl 12 O 19 at interaction of calcium oxide and aluminium in solid form has been studied. Some physical-chemical characteristics of calcium hexa-aluminate are given. (author)

Rates of calcium carbonate removal from soils.

NARCIS (Netherlands)

Breemen, van N.; Protz, R.

1988-01-01

Mean annual rates of calcium carbonate removal from soils in a subarctic climate estimated from data on two chronosequences of calcareous storm ridges, appeared to be relatively constant through time. Concentrations of dissolved calcium carbonate in the soil solution in the study sites calculated

Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation

Energy Technology Data Exchange (ETDEWEB)

Wu, Y.; Ajo-Franklin, J.B.; Spycher, N.; Hubbard, S.S.; Zhang, G.; Williams, K.H.; Taylor, J.; Fujita, Y.; Smith, R.

2011-07-15

Ureolytically-driven calcium carbonate precipitation is the basis for a promising in-situ remediation method for sequestration of divalent radionuclide and trace metal ions. It has also been proposed for use in geotechnical engineering for soil strengthening applications. Monitoring the occurrence, spatial distribution, and temporal evolution of calcium carbonate precipitation in the subsurface is critical for evaluating the performance of this technology and for developing the predictive models needed for engineering application. In this study, we conducted laboratory column experiments using natural sediment and groundwater to evaluate the utility of geophysical (complex resistivity and seismic) sensing methods, dynamic synchrotron x-ray computed tomography (micro-CT), and reactive transport modeling for tracking ureolytically-driven calcium carbonate precipitation processes under site relevant conditions. Reactive transport modeling with TOUGHREACT successfully simulated the changes of the major chemical components during urea hydrolysis. Even at the relatively low level of urea hydrolysis observed in the experiments, the simulations predicted an enhanced calcium carbonate precipitation rate that was 3-4 times greater than the baseline level. Reactive transport modeling results, geophysical monitoring data and micro-CT imaging correlated well with reaction processes validated by geochemical data. In particular, increases in ionic strength of the pore fluid during urea hydrolysis predicted by geochemical modeling were successfully captured by electrical conductivity measurements and confirmed by geochemical data. The low level of urea hydrolysis and calcium carbonate precipitation suggested by the model and geochemical data was corroborated by minor changes in seismic P-wave velocity measurements and micro-CT imaging; the latter provided direct evidence of sparsely distributed calcium carbonate precipitation. Ion exchange processes promoted through NH{sub 4}{sup

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Final technical report, 1 September, 1992--31 August, 1993

Energy Technology Data Exchange (ETDEWEB)

Rapp, D.; Lytle, J.; Hackley, K.; Dagamac, M. [Illinois State Geological Survey, Champaign, IL (United States); Berger, R. [Univ. of Illinois, Urbana, IL (United States); Schanche, G. [Army Construction Engineering Research Lab., Champaign, IL (United States)

1993-12-31

This research was an investigation of calcium hydroxide, a sulfur-capturing sorbent, as a binder for coal fines. The reaction of carbon dioxide with calcium hydroxide, referred to as carbonation, was studied as a method for improving pellet quality. Carbonation forms a cementitious matrix of calcium carbonate. Research has demonstrated that calcium hydroxide is a viable binder for coal fines and that a roller-and-die pellet mill is an effective method of pellet formation. From a minus 28 mesh preparation plant fine coal sample, a roller-and-die pellet mill produced strong pellets when 5 and 10% calcium hydroxide was used as a binder. The pellets containing 10% calcium hydroxide strengthened considerably when air cured. This increase in strength was attributed to carbonation via atmospheric carbon dioxide. Pellets containing 10 wt% calcium hydroxide were produced using an extruder but pellets formed in this manner were much weaker than pellets produced with the roller-and-die mill. In tests performed using a laboratory hydraulic press, the effect of particle size and compaction pressure on pellet strength was studied. Particle distributions with mean sizes of 200, 90 and 40 microns were tested. The results indicate that pellet strength increased with decreasing particle size and increasing compaction pressure when calcium hydroxide was used as a binder. Pellets containing 10 wt% calcium hydroxide increased in strength by approximately 40% when air dried for one day. As above, this increase in strength was attributed to carbonation of the calcium hydroxide via atmospheric carbon dioxide.

Average cross-sections for /n, p/ reactions on calcium in a fission-type reactor spectrum

International Nuclear Information System (INIS)

Bruggeman, A.; Maenhaut, W.; Hoste, J.

1974-01-01

The average cross-section in a fission-type reactor spectrum sigmasub(F) was experimentally determined for the reactions 42 Ca/n,p/ 42 K, 43 Ca/n,p/ 43 K and 44 Ca/n,p/ 44 K. Calcium carbonate samples and fast neutron flux monitors were irradiated with and without cadmium shielding in the Thetis reactor (Institute for Nuclear Sciences, Rijksuniversiteit Gent). The potassium activities induced in the calcium carbonate samples were separated and purified by tetraphenylborate precipitation, after which they were measured with a Ge/Li/-detector of calibrated detection efficiency. On the basis of sigmasub(F)=0.64 mb for the reaction 27 Al/n,α/ 24 Na, the average cross-sections were as follows: 42 Ca/n,p/ 42 K: 2.82+-0.07 mb; 43 Ca/n,p/ 43 K: 1.89+-0.05 mb; 44 Ca/n,p/ 44 K: 0.065+-0.003 mb. (T.G.)

The production of precipitated calcium carbonate from industrial gypsum wastes

CSIR Research Space (South Africa)

De Beer, Morris

2014-05-01

Full Text Available -step) process was tested. Although only a low-grade CaCO3 product (86-88 mass% as CaCO3) could be produced, experimental results on the characteristics of CaS in the presence of CO2 in the CaS-H2O-CO2 system showed that the reaction proceeded in two distinct... stages. In the first stage, CaS dissolution took place, with H2S stripping occurring in the second stage. Calcium carbonation and the resulting precipitation of CaCO3 were concurrent with the CaS dissolution and the H2S stripping reactions. Because...

Seeded Growth Route to Noble Calcium Carbonate Nanocrystal.

Directory of Open Access Journals (Sweden)

Aminul Islam

Full Text Available A solution-phase route has been considered as the most promising route to synthesize noble nanostructures. A majority of their synthesis approaches of calcium carbonate (CaCO3 are based on either using fungi or the CO2 bubbling methods. Here, we approached the preparation of nano-precipitated calcium carbonate single crystal from salmacis sphaeroides in the presence of zwitterionic or cationic biosurfactants without external source of CO2. The calcium carbonate crystals were rhombohedron structure and regularly shaped with side dimension ranging from 33-41 nm. The high degree of morphological control of CaCO3 nanocrystals suggested that surfactants are capable of strongly interacting with the CaCO3 surface and control the nucleation and growth direction of calcium carbonate nanocrystals. Finally, the mechanism of formation of nanocrystals in light of proposed routes was also discussed.

Magnetically responsive calcium carbonate microcrystals.

Science.gov (United States)

Fakhrullin, Rawil F; Bikmullin, Aidar G; Nurgaliev, Danis K

2009-09-01

Here we report the fabrication of magnetically responsive calcium carbonate microcrystals produced by coprecipitation of calcium carbonate in the presence of citrate-stabilized iron oxide nanoparticles. We demonstrate that the calcite microcrystals obtained possess superparamagnetic properties due to incorporated magnetite nanoparticles and can be manipulated by an external magnetic field. The microcrystals doped with magnetic nanoparticles were utilized as templates for the fabrication of hollow polyelectrolyte microcapsules, which retain the magnetic properties of the sacrificial cores and might be spatially manipulated using a permanent magnet, thus providing the magnetic-field-facilitated delivery and separation of materials templated on magnetically responsive calcite microcrystals.

Use of seeds to control precipitation of calcium carbonate and determination of seed nature.

Science.gov (United States)

Donnet, Marcel; Bowen, Paul; Jongen, Nathalie; Lemaître, Jacques; Hofmann, Heinrich

2005-01-04

Understanding and controlling precipitation reactions is a major challenge for industrial crystallization. Calcium carbonate is a widely studied system: more than 3000 papers have been devoted to the subject over the past 10 years. The first step of the precipitation of calcium carbonate, from relatively concentrated solutions (0.01 mol/L), involves the formation of an initial gel phase which later transforms into calcite, vaterite, or a mixture of both phases. Our work aimed at controlling this first step. Nanosized seeds (8 nm), formed in situ, were used in order to control the often chaotic nucleation step which normally leads to poor phase selection and broad particle size distributions. Seeding has often been used to avoid spontaneous nucleation in metastable solutions for growth mechanism investigations of single-crystal calcium carbonate. Here the ability of a seeding method to control the precipitation reaction evolution even in the case of high supersaturation is demonstrated. The seeds and the presence of a polymeric additive (poly(acrylic acid)) allow the control of the precipitated polymorph and the specific surface area, while maintaining a narrow particle size distribution in the submicron range. Direct characterization methods did not succeed in identifying these nanoseeds; indirect methods using solubility calculations are used to demonstrate their existence and quantify size and number density of the nanosized seeds.

Effect of Temperature on Precipitation Rate of Calcium Carbonate Produced through Microbial Metabolic Process of Bio Materials

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Prima Yane Putri

2016-09-01

Full Text Available Concrete is the most widely used construction material in civil engineering. But plain concrete is a brittle material and has little resistance to cracking. The cracking in concrete promotes deterioration such as the corrosion of reinforcing rebar, therefore, repair in filling the crack is often carried out. Recently, repair methods using bio-based materials associated with microbial metabolic processes leading to precipitation of calcium carbonate have been intensively studied. In this study, influencing factors on the precipitation rate depending on the constituents of bio-based material comprising yeast, glucose and calcium acetate mixed in tris buffer solution was examined for improving the rate of initial reactions. In addition, effect of temperature change on the amount of calcium carbonate precipitation was also investigated. The precipitates were identified by X-ray diffraction. It was shown that the increase of temperature lead to a change on calcium carbonate precipitation and caused the pH decrease under 7.0.

Chicken eggshells (Gallus gallus domesticus) as carbonate calcium source for biomaterials production

International Nuclear Information System (INIS)

Junior, E.A. de O.; Bastos, J.S.B.; Silva, R.C. de S.; Macedo, H.R.A.; Macedo, M. O.C.; Bradim, A.S.

2016-01-01

The eggshells present high levels of calcium carbonate. Calcium carbonate obtained from eggshells has been used in the production of biomaterials with applications in bone regeneration, since it is biocompatible. In this work, calcium carbonate was obtained from eggshells to prepare a composite biomaterial. The presence of calcium carbonate bands was observed through spectrometry in the infrared region. Scanning electron microscopy showed the presence of calcium carbonate particles with different sizes and shapes. Carbonate predominance in the form of calcite was also observed through the X-ray diffraction

Development of poly(aspartic acid-co-malic acid) composites for calcium carbonate and sulphate scale inhibition.

Science.gov (United States)

Mithil Kumar, N; Gupta, Sanjay Kumar; Jagadeesh, Dani; Kanny, K; Bux, F

2015-01-01

Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65-70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10 mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications.

Solubility and bioavailability of stabilized amorphous calcium carbonate.

Science.gov (United States)

Meiron, Oren E; Bar-David, Elad; Aflalo, Eliahu D; Shechter, Assaf; Stepensky, David; Berman, Amir; Sagi, Amir

2011-02-01

Since its role in the prevention of osteoporosis in humans was proven some 30 years ago, calcium bioavailability has been the subject of numerous scientific studies. Recent technology allowing the production of a stable amorphous calcium carbonate (ACC) now enables a bioavailability analysis of this unique form of calcium. This study thus compares the solubility and fractional absorption of ACC, ACC with chitosan (ACC-C), and crystalline calcium carbonate (CCC). Solubility was evaluated by dissolving these preparations in dilute phosphoric acid. The results demonstrated that both ACC and ACC-C are more soluble than CCC. Fractional absorption was evaluated by intrinsically labeling calcium carbonate preparations with (45)Ca, orally administrated to rats using gelatin capsules. Fractional absorption was determined by evaluating the percentage of the administrated radioactive dose per milliliter that was measured in the serum, calcium absorption in the femur, and whole-body retention over a 34-hour period. Calcium serum analysis revealed that calcium absorption from ACC and ACC-C preparations was up to 40% higher than from CCC, whereas retention of ACC and ACC-C was up to 26.5% higher than CCC. Absorbed calcium in the femurs of ACC-administrated rats was 30% higher than in CCC-treated animals, whereas 15% more calcium was absorbed following ACC-C treatment than following CCC treatment. This study demonstrates the enhanced solubility and bioavailability of ACC over CCC. The use of stable ACC as a highly bioavailable dietary source for calcium is proposed based on the findings of this study. Copyright © 2011 American Society for Bone and Mineral Research.

Calcium content of different compositions of gallstones and pathogenesis of calcium carbonate gallstones

Directory of Open Access Journals (Sweden)

Ji-Kuen Yu

2013-01-01

Conclusion: From our study, we found chronic and/or intermittent cystic duct obstructions and low-grade GB wall inflammation lead to GB epithelium hydrogen secretion dysfunction. Increased calcium ion efflux into the GB lumen combined with increased carbonate anion presence increases SI_CaCO3 from 1 to 22.4. Thus, in an alkaline milieu with pH 7.8, calcium carbonate begins to aggregate and precipitate.

Carbon isotope fractionation between amorphous calcium carbonate and calcite in earthworm-produced calcium carbonate

International Nuclear Information System (INIS)

Versteegh, E.A.A.; Black, S.; Hodson, M.E.

2017-01-01

In this study we investigate carbon isotope fractionation during the crystallization of biogenic calcium carbonate. Several species of earthworm including Lumbricus terrestris secrete CaCO_3. Initially a milky fluid comprising micro-spherules of amorphous CaCO_3 (ACC) is secreted into pouches of the earthworm calciferous gland. The micro-spherules coalesce and crystalize to form millimetre scale granules, largely comprising calcite. These are secreted into the earthworm intestine and from there into the soil. L. terrestris were cultured for 28 days in two different soils, moistened with three different mineral waters at 10, 16 and 20 °C. The milky fluid in the calciferous glands, granules in the pouches of the calciferous glands and granules excreted into the soil were collected and analysed by FTIR spectroscopy to determine the form of CaCO_3 present and by IRMS to determine δ"1"3C values. The milky fluid was ACC. Granules removed from the pouches and soil were largely calcite; the granules removed from the pouches contained more residual ACC than those recovered from the soil. The δ"1"3C values of milky fluid and pouch granules became significantly more negative with increasing temperature (p ≤ 0.001). For samples from each temperature treatment, δ"1"3C values became significantly (p ≤ 0.001) more negative from the milky fluid to the pouch granules to the soil granules (−13.77, −14.69 and −15.00 respectively at 10 °C; −14.37, −15.07 and −15.18 respectively at 16 °C and −14.89, −15.41 and −15.65 respectively at 20 °C). Fractionation of C isotopes occurred as the ACC recrystallized to form calcite with the fractionation factor ε_c_a_l_c_i_t_e_-_A_C_C = −1.20 ± 0.52‰. This is consistent with the crystallization involving dissolution and reprecipitation rather than a solid state rearrangement. Although C isotopic fractionation has previously been described between different species of dissolved inorganic carbon

Synthesis of calcium carbonate using extract components of croaker gill as morphology and polymorph adjust control agent

International Nuclear Information System (INIS)

Chen, Hao; Qing, Chengsong; Zheng, Jiaoling; Liu, Yuxi; Wu, Gang

2016-01-01

Biomimetic synthesis of calcium carbonate with various polymorphs, sizes and morphologies by using organic substrates has become an interesting topic for the last years. Calcium carbonate has been synthesized by the reaction of Na 2 CO 3 and CaCl 2 in the presence of extract components of croaker gill. The products were characterized by powder X-ray diffraction (PXRD) and Fourier transform infrared (FT-IR) spectrum, and particle morphologies were observed by scanning electron microscope (SEM). The results show that at lower concentration yellow croaker gill extract has no effect on calcium carbonate crystal polymorph. Calcite was obtained only. But the morphologies of calcite particle change with the increase of the concentration. The corners of the particle change from angular to curved. However, with the further increase of the concentration of yellow croaker gill extract, the calcium carbonate obtained is a mixture of calcite and vaterite. The vaterite component in the mixture rises with increasing concentration of extract solution, indicating that the proteins from the yellow croaker gill during growth play a crucial role in stabilizing and directing the crystal growth. - Graphical abstract: Calcium carbonate has been synthesized by using extract components of croaker gill as adjust control agent. The results indicate that yellow croaker gill extract has no effect on calcium carbonate crystal polymorph when its concentration is low. But the morphologies of calcite particle change with the increase of the concentration. With the further increase of the concentration of yellow croaker gill extract, the calcium carbonate obtained is a mixture of calcite and vaterite. The vaterite component in the mixture rises with increasing concentration of extract solution, indicating that the proteins from the yellow croaker gill during growth play a crucial role in stabilizing and directing the crystal growth. - Highlights: • Biomimetic synthesis of calcium carbonate �

Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

Science.gov (United States)

Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

2011-12-23

Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction of alkali metal nitrates with calcium carbonate and kyanite

International Nuclear Information System (INIS)

Protsyuk, A.P.; Malakhov, A.I.; Karabanov, V.P.; Lebedeva, L.P.

1978-01-01

Thermographic, thermodynamic and X-ray phase studies have been made into the interaction of alkali metal nitrates with calcium carbonate and kyanite. Examined among other things was the effect of water vapor and carbon dioxide on the interaction between alkali metal nitrates and kyanite. The chemical mechanism of the occurring processes has been established. The interaction with calcium carbonates results in the formation of alkali metal carbonates and calcium oxide with liberation of nitrogen oxide and oxygen. The products of the interaction with kyanite are shown to be identical with the compounds forming when alkali metal carbonates are used

Granule fraction inhomogeneity of calcium carbonate/sorbitol in roller compacted granules

DEFF Research Database (Denmark)

Bacher, Charlotte; Olsen, P.M.; Bertelsen, P.

2008-01-01

The granule fraction inhomogeneity of roller compacted granules was examined on mixtures of three different morphologic forms of calcium carbonate and three particle sizes of sorbitol. The granule fraction inhomogeneity was determined by the distribution of the calcium carbonate in each of the 10...... size fractions between 0 and 2000 µm and by calculating the demixing potential. Significant inhomogeneous occurrence of calcium carbonate in the size fractions was demonstrated, depending mostly on the particles sizes of sorbitol but also on the morphological forms of calcium carbonate......, the ability of the powder to agglomerate in the roller compactor was demonstrated to be related to the ability of the powder to be compacted into a tablet, thus the most compactable calcium carbonate and the smallest sized sorbitol improved the homogeneity by decreasing the demixing potential....

Analysis of barium hydroxide and calcium hydroxide slurry carbonation reactors

International Nuclear Information System (INIS)

Patch, K.D.; Hart, R.P.; Schumacher, W.A.

1980-05-01

The removal of CO 2 from air was investigated by using a continuous-agitated-slurry carbonation reactor containing either barium hydroxide [Ba(OH) 2 ] or calcium hydroxide [Ca(OH) 2 ]. Such a process would be applied to scrub 14 CO 2 from stack gases at nuclear-fuel reprocessing plants. Decontamination factors were characterized for reactor conditions which could alter hydrodynamic behavior. An attempt was made to characterize reactor performance with models assuming both plug flow and various degrees of backmixing in the gas phase. The Ba(OH) 2 slurry enabled increased conversion, but apparently the process was controlled under some conditions by phenomena differing from those observed for carbonation by Ca(OH) 2 . Overall reaction mechanisms are postulated

Distribution of cadmium between calcium carbonate and solution, 2

International Nuclear Information System (INIS)

Kitano, Yasushi; Kanamori, Nobuko; Fujiyoshi, Ryoko

1978-01-01

The distribution coefficient of cadmium between calcite and solution has been measured in the calcium bicarbonate solution containing cadmium and chloride ions, which forms complexes with cadmium ions. It has been confirmed experimentally that cadmium carbonate is present as a solid solution between calcitic calcium carbonate and cadmium carbonate in the carbonate precipitate formed in the solution system. However, the constant value of the thermodynamic distribution coefficient of cadmium between calcite and solution has not been obtained experimentally in the calcium bicarbonate solution containing cadmium and chloride ions. It may have been caused by the very specific behavior of cadmium ions, but the exact reason remains unsolved and must be studied. (Kobatake, H.)

Hypoparathyroidism: what is the best calcium carbonate supplementation intake form?

Science.gov (United States)

Gollino, Loraine; Biagioni, Maria Fernanda Giovanetti; Sabatini, Nathalia Regina; Tagliarini, José Vicente; Corrente, José Eduardo; Paiva, Sérgio Alberto Rupp de; Mazeto, Gláucia Maria Ferreira da Silva

2017-11-15

In hypoparathyroidism, calcium supplementation using calcium carbonate is necessary for the hypocalcemia control. The best calcium carbonate intake form is unknown, be it associated with feeding, juice or in fasting. The objective was to evaluate the calcium, phosphorus and Calcium×Phosphorus product serum levels of hypoparathyroidism women after total thyroidectomy, following calcium carbonate intake in three different forms. A crossover study was carried out with patients presenting definitive hypoparathyroidism, assessed in different situations (fasting, with water, orange juice, breakfast with a one-week washout). Through the review of clinical data records of tertiary hospital patients from 1994 to 2010, 12 adult women (18 50 years old) were identified and diagnosed with definitive post-thyroidectomy hypoparathyroidism. The laboratory results of calcium and phosphorus serum levels dosed before and every 30min were assessed, for 5h, after calcium carbonate intake (elementary calcium 500mg). The maximum peak average values for calcium, phosphorus and Calcium×Phosphorus product were 8.63mg/dL (water), 8.77mg/dL (orange juice) and 8.95mg/dL (breakfast); 4.04mg/dL (water), 4.03mg/dL (orange juice) and 4.12mg/dL (breakfast); 34.3mg 2 /dL 2 (water), 35.8mg 2 /dL 2 (orange juice) and 34.5mg 2 /dL 2 (breakfast), respectively, and the area under the curve 2433mg/dLmin (water), 2577mg/dLmin (orange juice) and 2506mg/dLmin (breakfast), 1203mg/dLmin (water), 1052mg/dLmin (orange juice) and 1128mg/dLmin (breakfast), respectively. There was no significant difference among the three different tests (p>0.05). The calcium, phosphorus and Calcium×Phosphorus product serum levels evolved in a similar fashion in the three calcium carbonate intake forms. Copyright © 2017 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Calcium oxide/carbon dioxide reactivity in a packed bed reactor of a chemical heat pump for high-temperature gas reactors

International Nuclear Information System (INIS)

Kato, Yukitaka; Yamada, Mitsuteru; Kanie, Toshihiro; Yoshizawa, Yoshio

2001-01-01

The thermal performance of a chemical heat pump that uses a calcium oxide/carbon dioxide reaction system was discussed as a heat storage system for utilizing heat output from high temperature gas reactors (HTGR). Calcium oxide/carbon dioxide reactivity for the heat pump was measured using a packed bed reactor containing 1.0 kg of reactant. The reactor was capable of storing heat at 900 deg. C by decarbonation of calcium carbonate and generating up to 997 deg. C by carbonation of calcium oxide. The amount of stored heat in the reactor was 800-900 kJ kg -1 . The output temperature of the reactor could be controlled by regulating the carbonation pressure. The thermal storage performance of the reactor was superior to that of conventional sensible heat storage systems. A heat pump using this CaO/CO 2 reactor is expected to contribute to thermal load leveling and to realize highly efficient utilization of HTGR output due to the high heat storage density and high-quality temperature output of the heat pump

Nacre-like calcium carbonate controlled by ionic liquid/graphene oxide composite template.

Science.gov (United States)

Yao, Chengli; Xie, Anjian; Shen, Yuhua; Zhu, Jinmiao; Li, Hongying

2015-06-01

Nacre-like calcium carbonate nanostructures have been mediated by an ionic liquid (IL)-graphene oxide (GO) composite template. The resultant crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffractometry (XRD). The results showed that either 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) or graphene oxide can act as a soft template for calcium carbonate formation with unusual morphologies. Based on the time-dependent morphology changes of calcium carbonate particles, it is concluded that nacre-like calcium carbonate nanostructures can be formed gradually utilizing [BMIM]BF4/GO composite template. During the process of calcium carbonate formation, [BMIM]BF4 acted not only as solvents but also as morphology templates for the fabrication of calcium carbonate materials with nacre-like morphology. Based on the observations, the possible mechanisms were also discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental kinetic study and modeling of calcium oxide carbonation

International Nuclear Information System (INIS)

Rouchon, L.

2012-01-01

Anthropogenic carbon dioxide (CO 2 ) emissions, major contributors to the greenhouse effect, are considered as the main cause of global warming. So, decrease of CO 2 emitted by large industrial combustion sources or power plants, is an important scientific goal. One of the approaches is based on CO 2 separation and capture from flue gas, followed by sequestration in a wide range of geological formations. In this aim, CO 2 is captured by sorbents like calcium oxide (CaO) in multi-cycle process of carbonation/de-carbonation. However, it was shown that the most important limitations of such process are related to the reversibility of reaction. CaO rapidly loses activity towards CO 2 , so the maximum extent of carbonation decreases as long as the number of cycles increases. In order to well understand the processes and parameters influencing the capture capacity of CaO-based sorbents, it appears important to get details on the kinetic law governing the reaction, which have not been really studied up to now. To investigate this reaction, CaO carbonation kinetics was followed by means of thermogravimetric analysis (TGA) on divided materials. Special care was given to the validation of the usual kinetic assumptions such as steady state and rate-determining step assumptions. The aim was to obtain a model describing the reaction in order to explain the influence of intensive variables such as carbonation temperature and CO 2 partial pressure. TGA curves obtained under isothermal and isobaric conditions showed an induction period linked to the nucleation process and a strong slowing down of the reaction rate once a given fractional conversion was reached. Both phenomena were observed to depend on carbonation temperature and CO 2 partial pressure. To explain these results, the evolution of texture and microstructure of the solid during the reaction was regarded as essential. Reaction at the grain scale induces a volume increase from CaO to CaCO 3 which causes a change in the

DECOMPOSITION STUDY OF CALCIUM CARBONATE IN COCKLE SHELL

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MUSTAKIMAH MOHAMED

2012-02-01

Full Text Available Calcium oxide (CaO is recognized as an efficient carbon dioxide (CO2 adsorbent and separation of CO2 from gas stream using CaO based adsorbent is widely applied in gas purification process especially at high temperature reaction. CaO is normally been produced via thermal decomposition of calcium carbonate (CaCO3 sources such as limestone which is obtained through mining and quarrying limestone hill. Yet, this study able to exploit the vast availability of waste resources in Malaysia which is cockle shell, as the potential biomass resources for CaCO3 and CaO. In addition, effect of particle size towards decomposition process is put under study using four particle sizes which are 0.125-0.25 mm, 0.25-0.5 mm, 1-2 mm, and 2-4 mm. Decomposition reactivity is conducted using Thermal Gravimetric Analyzer (TGA at heating rate of 20°C/minutes in inert (Nitrogen atmosphere. Chemical property analysis using x-ray fluorescence (XRF, shows cockle shell is made up of 97% Calcium (Ca element and CaO is produced after decomposition is conducted, as been analyzed by x-ray diffusivity (XRD analyzer. Besides, smallest particle size exhibits the highest decomposition rate and the process was observed to follow first order kinetics. Activation energy, E, of the process was found to vary from 179.38 to 232.67 kJ/mol. From Arrhenius plot, E increased when the particle size is larger. To conclude, cockle shell is a promising source for CaO and based on four different particles sizes used, sample at 0.125-0.25 mm offers the highest decomposition rate.

Preparation and Characterization of a Calcium Carbonate Aerogel

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Johann Plank

2009-01-01

Full Text Available We report on a facile method for the preparation of a calcium carbonate aerogel consisting of aggregated secondary vaterite particles with an approximate average diameter of 50 nm. It was synthesized via a sol-gel process by reacting calcium oxide with carbon dioxide in methanol and subsequent supercritical drying of the alcogel with carbon dioxide. The resulting monolith was opaque, brittle and had overall dimensions of 6×2×1 cm. It was characterized by X-ray powder diffraction, nitrogen adsorption method (BET, and scanning electron microscopy.

Nanosized amorphous calcium carbonate stabilized by poly(ethylene oxide)-b-poly(acrylic acid) block copolymers.

Science.gov (United States)

Guillemet, Baptiste; Faatz, Michael; Gröhn, Franziska; Wegner, Gerhard; Gnanou, Yves

2006-02-14

Particles of amorphous calcium carbonate (ACC), formed in situ from calcium chloride by the slow release of carbon dioxide by alkaline hydrolysis of dimethyl carbonate in water, are stabilized against coalescence in the presence of very small amounts of double hydrophilic block copolymers (DHBCs) composed of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blocks. Under optimized conditions, spherical particles of ACC with diameters less than 100 nm and narrow size distribution are obtained at a concentration of only 3 ppm of PEO-b-PAA as additive. Equivalent triblock or star DHBCs are compared to diblock copolymers. The results are interpreted assuming an interaction of the PAA blocks with the surface of the liquid droplets of the concentrated CaCO3 phase, formed by phase separation from the initially homogeneous reaction mixture. The adsorption layer of the block copolymer protects the liquid precursor of ACC from coalescence and/or coagulation.

Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature

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K. B. Kale

2012-12-01

Full Text Available The CO2 adsorption by calcium zirconate was explored at pre- and post- combustion temperature condition. The several samples of the calcium zirconate were prepared by different methods such as sol-gel, solid-solid fusion, template and micro-emulsion. The samples of the calcium zirconate were characterized by measurement of surface area, alkalinity/acidity, and recording the XRD patterns and SEM images. The CO2 adsorptions by samples of the calcium zirconate were studied in the temperature range 100 to 850 oC and the CO2 adsorptions were observed in the ranges of 6.88 to 40.6 wt % at 600 0C and 8 to 16.82 wt% at in between the temperatures 200 to 300 oC. The effect of Ca/Zr mol ratio in the samples of the calcium zirconate on the CO2 adsorption and alkalinity were discussed. The adsorbed moisture by the samples of the calcium zirconate was found to be useful for the CO2 adsorption. The promoted the samples of the calcium zirconate by K+, Na+, Rb+, Cs+, Ag+ and La3+ showed the increased CO2 adsorption. The exposure time of CO2 on the samples of the calcium zirconate showed the increased CO2 adsorption. The samples of the calcium zirconate were found to be regenerable and reusable several times for the adsorption of CO2 for at the post- and pre-combustion temperature condition. Copyright © 2012 by BCREC Undip. All rights reservedReceived: 23rd June 2012, Revised: 28th August 2012, Accepted: 30th August 2012[How to Cite: K. B. Kale, R. Y. Raskar, V. H. Rane and A. G.  Gaikwad (2012. Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (2: 124-136. doi:10.9767/bcrec.7.2.3686.124-136] [How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.3686.124-136 ] | View in 

Effects of nano calcium carbonate and nano calcium citrate on toxicity in ICR mice and on bone mineral density in an ovariectomized mice model

Energy Technology Data Exchange (ETDEWEB)

Huang, Sherry; Chen, Jin Ching; Hsu, Chin Wei; Chang, Walter H, E-mail: whchang@cycu.edu.t [Center for Nano Bioengineering, Chung Yuan Christian University, Chung Li 32023, Taiwan (China); Department of Biomedical Engineering, Chung Yuan Christian University, Chung Li 32023, Taiwan (China)

2009-09-16

Taking calcium supplements can reduce the risk of developing osteoporosis, but they are not readily absorbed in the gastrointestinal tract. Nanotechnology is expected to resolve this problem. In the present study, we examined whether the bioavailability of calcium carbonate and calcium citrate can be improved by reducing the particle size. The morphology of nano calcium carbonate and nano calcium citrate was characterized by dynamic laser-light scattering (DLS), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The measurements obtained from DLS, FE-SEM and TEM were comparable. Acute and sub-chronic toxicity tests were performed to establish the safety of these products after oral administration. The no-observed-adverse-effect levels of nano calcium carbonate and nano calcium citrate were 1.3 and 2.3 g kg{sup -1} body weight, respectively. The results of our in vivo studies indicate that administering nano calcium carbonate and nano calcium citrate can enhance the serum calcium concentration and maintain the whole-body bone mineral density in ovariectomized mice. These data suggest that nano calcium carbonate and nano calcium citrate are more bioavailable than micro calcium carbonate and micro calcium citrate, respectively.

Evaluation of Various Synthesis Methods for Calcite-Precipitated Calcium Carbonate (PCC) Formation

International Nuclear Information System (INIS)

Ramakrishna, Chilakala; Thenepalli, Thriveni; Ahn, Ji Whan

2017-01-01

This review paper evaluates different kinds of synthesis methods for calcite precipitated calcium carbonates by using different materials. The various processing routes of calcite with different compositions are reported and the possible optimum conditions required to synthesize a desired particle sizes of calcite are predicted. This paper mainly focuses on that the calcite morphology and size of the particles by carbonation process using loop reactors. In this regard, we have investigated various parameters such as CO 2 flow rate, Ca (OH) 2 concentration, temperature, pH effect, reaction time and loop reactor mechanism with orifice diameter. The research results illustrate the formation of well-defined and pure calcite crystals with controlled crystal growth and particle size, without additives or organic solvents. The crystal growth and particle size can be controlled, and smaller sizes are obtained by decreasing the Ca (OH) 2 concentration and increasing the CO 2 flow rate at lower temperatures with suitable pH. The crystal structure of obtained calcite was characterized by using X-ray diffraction method and the morphology by scanning electron microscope (SEM). The result of x-ray diffraction recognized that the calcite phase of calcium carbonate was the dominating crystalline structure.

Carbonation of calcium aluminate cement pastes

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Fernández-Carrasco, L.

2001-12-01

Full Text Available This work discusses the results from accelerated tests intended to investigate the ways the different curing methods affect the carbonation of calcium aluminate cements pastes (CAC. The research was focused on the mineralogical composition of hydrated and carbonated samples. The compressive strengths and the porosity of the samples have been determined. Results point out that vaterite and aragonite are formed as a result of carbonation of both cubic and hexagonal calcium aluminate hydrates. The polymorph of calcium carbonate formed does not depend on the curing process. Carbonation rates is higher in hexagonal than in cubic hydrates. Results obtained through this study evidence that, as a consequence of the carbonation process of CAC pastes, in test conditions, an increase of the mechanical strengths occurs.

En el presente trabajo se discuten los resultados obtenidos en los ensayos acelerados llevados a cabo para investigar los efectos de diferentes métodos de curado sobre la carbonatacion de pastas del cemento de aluminato de calcio (CAC. Se estudió la composición mineralógica de las muestras hidratadas y carbonatadas. Además, se determinaron las resistencias mecánicas a compresión y la porosidad de las probetas. Los resultados indican que la vaterita y el aragonito son las polimorfías del CaCO₃ que se forman al carbonatar los aluminatos cálcicos hidratos, tanto los de naturaleza hexagonal como cúbica. El polimorfo del carbonato cálcico formado no depende del proceso de curado. La velocidad de carbonatación de los hidratos hexagonales es mayor que la de los cúbicos. Los resultados obtenidos en el presente trabajo han evidenciado que como consecuencia del proceso de carbonatación sobre pastas de CAC, en las condiciones realizadas, se produce un incremento en las resistencias mecánicas.

Mechanical properties of polypropylene/calcium carbonate nanocomposites

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Daniel Eiras

2009-01-01

Full Text Available The aim of this work was to study the influence of calcium carbonate nanoparticles in both tensile and impact mechanical properties of a polypropylene homopolymer. Four compositions of PP/CaCO3 nanocomposites were prepared in a co-rotational twin screw extruder machine with calcium carbonate content of 3, 5, 7 and 10 wt. (% The tests included SEM analyzes together with EDS analyzer and FTIR spectroscopy for calcium carbonate, tensile and impact tests for PP and the nanocomposites. The results showed an increase in PP elastic modulus and a little increase in yield stress. Brittle-to-ductile transition temperature was reduced and the impact resistance increased with the addition of nanoparticles. From the stress-strain curves we determined the occurrence of debonding process before yielding leading to stress softening. Debonding stress was determined from stress-strain curves corresponding to stress in 1% strain. We concluded that the tensile properties depend on the surface contact area of nanoparticles and on their dispersion. Finally we believe that the toughening was due to the formation of diffuse shear because of debonding process.

Synthesis of hydroxyapatite with the use of calcium carbonate as of the biological precursor; Sintese de hidroxiapatita com o uso de carbonato de calcio de origem biologica como precurssor

Energy Technology Data Exchange (ETDEWEB)

Aguilar, M.S.; Di Lello, B.C.; Queiroz, F.; Campos, N.C., E-mail: marilzasa@oi.com.br [Universidade Estacio de Sa (UESA), Rio de Janeiro, RJ (Brazil). Departamento de Engenharia; Campos, J.B. [Universidade do Estado do Rio de Janeiro (PPGEM/UERJ), RJ (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica

2014-07-01

This work describes the synthesis of hydroxyapatite from calcium from biological materials such as shells carbonate. In the syntheses performed, the calcium carbonate of biological origin was used as the precursor and through a precipitation reaction with phosphoric acid, was converted into calcium hydroxide. Sequentially, the precipitate was aged, filtered, washed, dried and calcined, and then transformed into hydroxyapatite. The characterization of the powders was performed by X-DR (X-ray diffraction) and SEM (scanning electron microscopy). DR-X as determined hydroxyapatite calcium phosphate phase calcium. SEM revealed a morphology of finely divided particles. The method B.E.T. showed values of specific area and volume of micropores consistent with the literature. The results of the characterizations proved feasible to use for obtaining biological hydroxyapatite materials used in the reaction conditions.(author)

Regeneration of sulfated metal oxides and carbonates

Science.gov (United States)

Hubble, Bill R.; Siegel, Stanley; Cunningham, Paul T.

1978-03-28

Alkali metal or alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate found in dolomite or limestone are employed for removal of sulfur dioxide from combustion exhaust gases. The sulfated carbonates are regenerated to oxides through use of a solid-solid reaction, particularly calcium sulfide with calcium sulfate to form calcium oxide and sulfur dioxide gas. The regeneration is performed by contacting the sulfated material with a reductant gas such as hydrogen within an inert diluent to produce calcium sulfide in mixture with the sulfate under process conditions selected to permit the sulfide-sulfate, solid-state reaction to occur.

Calcium carbonate nucleation in an alkaline lake surface water, Pyramid Lake, Nevada, USA

Science.gov (United States)

Reddy, Michael M.; Hoch, Anthony

2012-01-01

Calcium concentration and calcite supersaturation (Ω) needed for calcium carbonate nucleation and crystal growth in Pyramid Lake (PL) surface water were determined during August of 1997, 2000, and 2001. PL surface water has Ω values of 10-16. Notwithstanding high Ω, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface water for several months. However, calcium solution addition to PL surface-water samples caused reproducible calcium carbonate mineral nucleation and crystal growth. Mean PL surface-water calcium concentration at nucleation was 2.33 mM (n = 10), a value about nine times higher than the ambient PL surface-water calcium concentration (0.26 mM); mean Ω at nucleation (109 with a standard deviation of 8) is about eight times the PL surface-water Ω. Calcium concentration and Ω regulated the calcium carbonate formation in PL nucleation experiments and surface water. Unfiltered samples nucleated at lower Ω than filtered samples. Calcium concentration and Ω at nucleation for experiments in the presence of added particles were within one standard deviation of the mean for all samples. Calcium carbonate formation rates followed a simple rate expression of the form, rate (mM/min) = A (Ω) + B. The best fit rate equation "Rate (Δ mM/Δ min) = -0.0026 Ω + 0.0175 (r = 0.904, n = 10)" was statistically significant at greater than the 0.01 confidence level and gives, after rearrangement, Ω at zero rate of 6.7. Nucleation in PL surface water and morphology of calcium carbonate particles formed in PL nucleation experiments and in PL surface-water samples suggest crystal growth inhibition by multiple substances present in PL surface water mediates PL calcium carbonate formation, but there is insufficient information to determine the chemical nature of all inhibitors.

Nacre-like calcium carbonate controlled by ionic liquid/graphene oxide composite template

Energy Technology Data Exchange (ETDEWEB)

Yao, Chengli [School of Chemistry and Chemical Engineering, Anhui University, Hefei, Anhui 230039 (China); School of Chemistry and Chemical Engineering, Hefei Normal University, Hefei, Anhui 230601 (China); Xie, Anjian, E-mail: anjx@163.com [School of Chemistry and Chemical Engineering, Anhui University, Hefei, Anhui 230039 (China); Shen, Yuhua [School of Chemistry and Chemical Engineering, Anhui University, Hefei, Anhui 230039 (China); Zhu, Jinmiao; Li, Hongying [School of Chemistry and Chemical Engineering, Hefei Normal University, Hefei, Anhui 230601 (China)

2015-06-01

Nacre-like calcium carbonate nanostructures have been mediated by an ionic liquid (IL)-graphene oxide (GO) composite template. The resultant crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffractometry (XRD). The results showed that either 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF{sub 4}) or graphene oxide can act as a soft template for calcium carbonate formation with unusual morphologies. Based on the time-dependent morphology changes of calcium carbonate particles, it is concluded that nacre-like calcium carbonate nanostructures can be formed gradually utilizing [BMIM]BF{sub 4}/GO composite template. During the process of calcium carbonate formation, [BMIM]BF{sub 4} acted not only as solvents but also as morphology templates for the fabrication of calcium carbonate materials with nacre-like morphology. Based on the observations, the possible mechanisms were also discussed. - Highlights: • Nacre-like CaCO{sub 3}/GO were prepared by gas diffusion. • Ionic liquid/GO served as composite templates. • The interaction of Ca{sup 2+} ions and GO played a very important role in the formation of nacre-like CaCO{sub 3}.

On the structure of amorphous calcium carbonate--a detailed study by solid-state NMR spectroscopy.

Science.gov (United States)

Nebel, Holger; Neumann, Markus; Mayer, Christian; Epple, Matthias

2008-09-01

The calcium carbonate phases calcite, aragonite, vaterite, monohydrocalcite (calcium carbonate monohydrate), and ikaite (calcium carbonate hexahydrate) were studied by solid-state NMR spectroscopy ( (1)H and (13)C). Further model compounds were sodium hydrogencarbonate, potassium hydrogencarbonate, and calcium hydroxide. With the help of these data, the structure of synthetically prepared additive-free amorphous calcium carbonate (ACC) was analyzed. ACC contains molecular water (as H 2O), a small amount of mobile hydroxide, and no hydrogencarbonate. This supports the concept of ACC as a transient precursor in the formation of calcium carbonate biominerals.

Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications.

Science.gov (United States)

Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari; Declercq, Heidi A; Schaubroeck, David; Mendes, Ana C; der Voort, Pascal Van; Dokupil, Agnieszka; Plis, Agnieszka; De Schamphelaere, Karel; Chronakis, Ioannis S; Pamuła, Elżbieta; Skirtach, Andre G

2017-12-01

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO 3 ) has been successfully applied as a bone regeneration material, but hydrogel-CaCO 3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO 3 , Mg-enriched CaCO 3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium:magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO 3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Multi-Functions of Carbonated Calcium Deficient Hydroxyapatite (CDHA)

Science.gov (United States)

Zhou, Huan

Natural bone is a complex composite mainly constituted of inorganic minerals and organic collagen molecules. Calcium phosphate (CaP) based materials have been proposed as the predominant bone substitute for bone tissue engineering applications due to their chemical similarity to bone mineral. Amorphous carbonated calcium deficient hydroxyapatite (CDHA) is an important compound among CaP materials because of the amorphous crystallite structure. The presence of extra ions in its lattice structure not only influences cell attachment and proliferation of osteoblasts, but also helps in bone metabolism. Biomimetic coating approach is the most widely used approach to produce CDHA coatings to implant. It is a process using simulated body fluid (SBF) to deposit bone-like CDHA coating to various material surfaces. The CDHA formation mechanism, SBF compositions and reacting conditions of biomimetic coating have already been sufficiently studied and compared in the past 20 years. It is an attempt in this thesis to explore new applications of SBF in biomedical research, focusing on different biomaterial applications: 1) based on the low temperature reaction condition of SBF, bisphosphonate incorporated CDHA coatings were deposited onto Ti6Al4V surface for the treatment of osteoporosis; 2) amorphous calcium phosphate nanospheres with extra elements in the lattice structure were prepared by a novel microwave assisted approach, providing a new potential of CaP materials production; 3) CDHA particles formed in SBF can be used as great fillers with biopolymers for preparing biocomposites for biomedical applications; 4) based on the high activity of CDHA amorphous structure and the stabilization ability of ethanol, yttrium and europium doped calcium phosphates were prepared using CDHA as a sacrificing template. In the end, future work based on these observations in the thesis is addressed, including areas of drug delivery, biocomposite fabrication and preparation of functionalized

Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders.

Science.gov (United States)

Csako, G; McGriff, N J; Rotman-Pikielny, P; Sarlis, N J; Pucino, F

2001-12-01

To describe a patient with primary hypothyroidism in whom ingestion of levothyroxine with calcium carbonate led to markedly elevated serum thyrotropin concentrations. A 61-year-old white woman with primary hypothyroidism, systemic lupus erythematosus, celiac disease, and history of Whipple resection for pancreatic cancer was euthyroid with levothyroxine 175-188 micrograms/d. After taking a high dose of calcium carbonate (1250 mg three times daily) with levothyroxine, she developed biochemical evidence of hypothyroidism (thyrotropin up to 41.4 mU/L) while remaining clinically euthyroid. Delaying calcium carbonate administration by four hours returned her serum thyrotropin to a borderline high concentration (5.7 mU/L) within a month. Serum concentrations of unbound and total thyroxine and triiodothyronine tended to decrease, but remained borderline low to normal while the patient concomitantly received levothyroxine and calcium carbonate. Concomitant administration of levothyroxine and calcium carbonate often results in levothyroxine malabsorption. While in most patients the clinical consequences of this interaction, even with prolonged exposure, are relatively small, overt hypothyrodism may develop in patients with preexisting malabsorption disorders. However, as the current case illustrates, the clinical manifestations of the initial levothyroxine deficit may not always be apparent and, of all usual laboratory thyroid function tests, only thyrotropin measurement will reliably uncover the exaggerated levothyroxine malabsorption. Decreased absorption of levothyroxine when given with calcium carbonate may be particularly pronounced in patients with preexisting malabsorption disorders. Once recognized, a change in drug administration schedule usually minimizes or eliminates this interaction.

Control of calcium carbonate precipitation in anaerobic reactors

NARCIS (Netherlands)

Langerak, van E.P.A.

1998-01-01

Anaerobic treatment of waste waters with a high calcium content may lead to excessive precipitation of calcium carbonate. So far, no proper methods were available to predict or reduce the extent of precipitation in an anaerobic treatment system. Moreover, it also was not clear to what

Biomediated Precipitation of Calcium Carbonate in a Slightly Acidic Hot Spring

Science.gov (United States)

Jiang, L.

2015-12-01

A slightly acidic hot spring named "Female Tower" (T=73.5 °C, pH=6.64) is located in the Jifei Geothermal Field, Yunnan Province, Southwest China. The precipitates in the hot spring are composed of large amounts of calcite, aragonite, and sulfur. Scanning electron microscopy (SEM) analyses revealed that the microbial mats were formed of various coccoid, rod-shaped, and filamentous microbes. Transmission electron microscopy (TEM) showed that the intracellular sulfur granules were commonly associated with these microbes. A culture-independent molecular phylogenetic analysis demonstrated that the majority of the bacteria in the spring were sulfur-oxidizing bacteria. In the spring water, H2S concentration was up to 60 ppm, while SO42- concentration was only about 10 ppm. We speculated that H2S might be utilized by sulfur-oxidizing bacteria in this hot spring water, leading to the intracellular formation of sulfur granules. In the meantime, this reaction increased the pH in the micron-scale microdomains, which fostered the precipitation of calcium carbonate in the microbial mats. The results of this study indicated that the sulfur-oxidizing bacteria could play an important role in calcium carbonate precipitation in slightly acidic hot spring environments.

Pilot-scale demonstration of the OSCAR process for high-temperature multipollutant control of coal combustion flue gas, using carbonated fly ash and mesoporous calcium carbonate

Energy Technology Data Exchange (ETDEWEB)

Gupta, H.; Thomas, T.J.; Park, A.H.A.; Iyer, M.V.; Gupta, P.; Agnihotri, R.; Jadhav, R.A.; Walker, H.W.; Weavers, L.K.; Butalia, T.; Fan, L.S. [Ohio State University, Columbus, OH (United States)

2007-07-15

A pilot-scale study of the Ohio State Carbonation Ash Reactivation (OSCAR) process was performed to demonstrate the reactivity of two novel calcium-based sorbents toward sulfur and trace heavy metal (arsenic, selenium, and mercury) capture in the furnace sorbent injection (FSI) mode on a 0.365 m{sup 3}/s slipstream of a bituminous coal-fired stoker boiler. The sorbents were synthesized by bubbling CO{sub 2} to precipitate calcium carbonate (a) from the unreacted calcium present in the lime spray dryer ash and (b) from calcium hydroxide slurry that contained a negatively charged dispersant. The heterogeneous reaction between these sorbents and SO{sub 2} gas occurred under entrained flow conditions by injecting fine sorbent powders into the flue gas slipstream. The reacted sorbents were captured either in a hot cyclone (about 650{sup o}C) or in the relatively cooler downstream baghouse (about 230{sup o}C). The baghouse samples indicated about 90% toward sulfation and captured arsenic, selenium and mercury to 800 ppmw, 175 ppmw and 3.6 ppmw, respectively.

Bio-inspired carbon electro-catalysis for the oxygen reduction reaction

OpenAIRE

Preuss, Kathrin; Kannuchamy, Vasanth Kumar; Marinovic, Adam; Isaacs, Mark; Wilson, Karen; Abrahams, Isaac; Titirici, Maria-Magdalena

2016-01-01

We report the synthesis, characterisation and catalytic performance of two nature-inspired biomass-derived electro-catalysts for the oxygen reduction reaction in fuel cells. The catalysts were prepared via pyrolysis of a real food waste (lobster shells) or by mimicking the composition of lobster shells using chitin and CaCO3 particles followed by acid washing. The simplified model of artificial lobster was prepared for better reproducibility. The calcium carbonate in both samples acts as a po...

Evaluation of Various Synthesis Methods for Calcite-Precipitated Calcium Carbonate (PCC) Formation

Energy Technology Data Exchange (ETDEWEB)

Ramakrishna, Chilakala [Hanil Cement Corporation, Danyang (Korea, Republic of); Thenepalli, Thriveni; Ahn, Ji Whan [Korea Institute of Geoscience and Mineral Resources, Daejeon (Korea, Republic of)

2017-06-15

This review paper evaluates different kinds of synthesis methods for calcite precipitated calcium carbonates by using different materials. The various processing routes of calcite with different compositions are reported and the possible optimum conditions required to synthesize a desired particle sizes of calcite are predicted. This paper mainly focuses on that the calcite morphology and size of the particles by carbonation process using loop reactors. In this regard, we have investigated various parameters such as CO{sub 2} flow rate, Ca (OH){sub 2} concentration, temperature, pH effect, reaction time and loop reactor mechanism with orifice diameter. The research results illustrate the formation of well-defined and pure calcite crystals with controlled crystal growth and particle size, without additives or organic solvents. The crystal growth and particle size can be controlled, and smaller sizes are obtained by decreasing the Ca (OH){sub 2} concentration and increasing the CO{sub 2} flow rate at lower temperatures with suitable pH. The crystal structure of obtained calcite was characterized by using X-ray diffraction method and the morphology by scanning electron microscope (SEM). The result of x-ray diffraction recognized that the calcite phase of calcium carbonate was the dominating crystalline structure.

Effet de l'amendement au carbonate de calcium (mikhart) de ...

African Journals Online (AJOL)

SARAH

31 janv. 2017 ... control substratum, SCa10 (S0 + 10 % powder of calcium carbonate), SCa20 (S0 + 20 % powder of calcium carbonate), SCa30 (S0 ..... puis montés sur un microscope électronique FEG Supra. 40 VP Zeiss à balayage et pression variable. Dès lors, ..... substrats amendés d'un apport en quantité et en qualité.

Crystal growth of calcium carbonate in silk fibroin/sodium alginate hydrogel

Science.gov (United States)

Ming, Jinfa; Zuo, Baoqi

2014-01-01

As known, silk fibroin-like protein plays a pivotal role during the formation of calcium carbonate (CaCO3) crystals in the nacre sheets. Here, we have prepared silk fibroin/sodium alginate nanofiber hydrogels to serve as templates for calcium carbonate mineralization. In this experiment, we report an interesting finding of calcium carbonate crystal growth in the silk fibroin/sodium alginate nanofiber hydrogels by the vapor diffusion method. The experimental results indicate calcium carbonate crystals obtained from nanofiber hydrogels with different proportions of silk fibroin/sodium alginate are mixture of calcite and vaterite with unusual morphologies. Time-dependent growth study was carried out to investigate the crystallization process. It is believed that nanofiber hydrogels play an important role in the process of crystallization. This study would help in understanding the function of organic polymers in natural mineralization, and provide a novel pathway in the design and synthesis of new materials related unique morphology and structure.

Calcium carbonate growth in the presence of water soluble cellulose ethers

International Nuclear Information System (INIS)

Zhang Fengju; Yang Xinguo; Tian Fei

2009-01-01

Calcium carbonate precipitation was performed in the presence of methyl cellulose (MC) and two kinds of hydroxyethyl cellulose (HEC FD-10000, HEC FD-30000). The results demonstrated that the final product morphology and structure of CaCO 3 crystals are highly sensitive to the concentration of the cellulose ethers aqueous solution. By precisely controlling their concentrations, all these three cellulose ethers solutions have the ability of protecting metastable vaterite from thermodynamically transforming into stable calcite. The intermediate products investigation showed to some extent the phase transformation of calcium carbonate in its growing process from metastable vaterite to calcite and indicated that the calcium carbonate crystal growth in HEC solutions occurs through dissolution and reprecipitation process. Calcium carbonate growth in both presence of HEC and ethanol or Mg 2+ was also examined. This work demonstrates the potential of water soluble cellulose ethers in controlling biominerals crystallization and growth. The results are revelatory for biomineralization and fabricating new organic-inorganic hybrids based on cellulose derivatives.

Preparation of calcium phosphate paste

International Nuclear Information System (INIS)

Mohd Reusmaazran Yusof; Norzita Yaacob; Idris Besar; Che Seman Mahmood; Rusnah Mustafa

2010-01-01

Calcium phosphate paste were prepared by mixing between calcium sodium potassium phosphate, Ca 2 NaK (PO 4 ) 2 (CSPP) and monocalcium phosphate monohydrate, Ca(H 2 PO 4 ) 2 .H 2 O (MCPM). CSPP were obtained by reaction between calcium hydrogen phosphate (CaHPO 4 ), potassium carbonate (K 2 CO 3 ) and sodium carbonate (Na 2 CO 3 ) in solid state sintering process followed by quenching in air at 1000 degree Celsius. The paste was aging in simulated body fluid (SBF) for 0.5, 1, 3, 6, 12, 24, 48 hrs, 3, 7 and 14 days. The morphological investigation indicated the formation of apatite crystal were first growth after 24 hours. The obvious growth of apatite crystal was shown at 3 days. The obvious growth of apatite crystal was shown in 7 and 14 days indicated the prediction of paste would have rapid reaction with bone after implantation. (author)

FT-Raman spectroscopic study of calcium-rich and magnesium-rich carbonate minerals.

Science.gov (United States)

Edwards, Howell G M; Villar, Susana E Jorge; Jehlicka, Jan; Munshi, Tasnim

2005-08-01

Calcium and magnesium carbonates are important minerals found in sedimentary environments. Although sandstones are the most common rock colonized by endolith organisms, the production of calcium and magnesium carbonates is important in survival strategies of organisms and as a source for the removal of oxalate ions. Extremophile organisms in some situations may convert or destroy carbonates of calcium and magnesium, which gives important information about the conditions under which these organisms can survive. The identification on the surface of Mars of 'White Rock' formations, in Juventae Chasma or Sabaea Terra, as possibly carbonate rocks makes the study of these minerals a prerequisite of remote Martian exploration. Here, we show the protocol for the identification by Raman spectroscopy of different calcium and magnesium carbonates and we present a database of relevance in the search for life, extinct or extant, on Mars; this will be useful for the assessment of data obtained from remote, miniaturized Raman spectrometers now proposed for Mars exploration.

Reactions between rocks and the hydroxides of calcium, sodium and potassium: progress report no. 1

International Nuclear Information System (INIS)

Van Aardt, J.H.P.; Visser, S.

1982-01-01

The reaction between the hydroxides of calcium, sodium and potassium, and clay minerals, feldspars, and some rocks (aggregates for use in concrete) was investigated. The reaction products were examined by means of x-ray diffraction and chemical analysis. The solid reaction products identified were hydrated calcium silicates,hydrated calcium aluminates, and hydrated calcium alumina silicates. It was found that, in the presence of water, calcium hydroxide liberated alkali into solution if the rocks and minerals contained alkali metals in their structure. Two crystalline hydrated sodium calcium silicates (12A and 16A) were prepared in the system Na 2 O-CaO-SiO 2 -H 2 O at 80 degrees Celsius. The one compound (12A) was also observed when sodium hydroxide plus calcium hydroxide and water reacted with silica- or silicate-containing rocks

Calcium carbonate precipitation in the Cueva di Watapana on Bonaire, Netherlands Antilles

NARCIS (Netherlands)

Meer Mohr, van der C.G.

1978-01-01

Calcium carbonate precipitates as low Mg-calcite and aragonite in slightly brackish water in a cave in the Pleistocene Middle Terrace of southern Bonaire. The calcium carbonate precipitates at the atmosphere-water interface forming floating calcite scales (calcite ice). Aragonite crystals frequently

Isolation and characterization of biogenic calcium carbonate ...

Indian Academy of Sciences (India)

Biogenic calcium carbonate/phosphate were isolated and characterized from oral bacteria (CPOB). The crystalline nature ... XRD analysis revealed the cubic phase of ... subjected to identify upto genus level according to Bergey's. Manual of ...

Adhesion property of epoxidized natural rubber (ENR-based adhesives containing calcium carbonate

Directory of Open Access Journals (Sweden)

2008-06-01

Full Text Available The adhesion property (i.e. viscosity, loop tack and peel strength of epoxidized natural rubber (ENR 25 and ENR 50 grade-based pressure-sensitive adhesive was studied in the presence of calcium carbonate. The range of calcium carbonate loaded was from 10 to 50 parts per hundred parts of rubber (phr. Coumarone-indene resin was used as the tackifier and its concentration was fixed at 80 phr. Toluene was chosen as the solvent throughout the investigation. The substrates (PET film/paper were coated with the adhesive using a SHEEN hand coater at a coating thickness of 60 µm. Viscosity of the adhesive was measured by a HAAKE Rotary Viscometer whereas loop tack and peel strength were determined by a Llyod Adhesion Tester operating at 30 cm/min. Results show that viscosity of ENR-based adhesives increases gradually with increase in calcium carbonate loading due to the concentration effect of the filler. However, for loop tack and peel strength, it passes through a maximum at 30 phr calcium carbonate, an observation which is attributed to the optimum wettability of adhesive on the substrate at this adhesive composition. ENR 25-based adhesive consistently exhibits higher adhesion property than ENR 50 for all calcium carbonate loadings studied.

Calcium carbonate as a possible dosimeter for high irradiation doses

International Nuclear Information System (INIS)

Negron M, A.; Ramos B, S.; Camargo R, C.; Uribe, R. M.; Gomez V, V.; Kobayashi, K.

2014-08-01

The aim of this work is to analyze the interactions of 5 MeV electron beam radiation and a 290 MeV/u Carbon beam with calcium carbonate (powder) at 298 K and at different irradiation doses, for the potential use of calcium carbonate as a high-dose dosimeter. The irradiation doses with the electron beam were from 0.015 to 9 MGy, and with Carbon beam from 1.5 kGy to 8 kGy. High-energy radiation induces the formation of free radicals in solid calcium carbonate that can be detected and measured by electron paramagnetic resonance (EPR). An increase of the EPR response for some of the free radicals produced in the sample was observed as a function of the irradiation dose. The response of one of the radicals decreased with the dose. These measurements are reproducible; the preparation of the sample is simple and inexpensive; and the signal is stable for several months. The response curves show that the dosimeter tends to saturate at 10 MGy. Based on these properties, we propose this chemical compound as a high-dose dosimeter, mainly for electron irradiation. (author)

Calcium carbonate as a possible dosimeter for high irradiation doses

Energy Technology Data Exchange (ETDEWEB)

Negron M, A.; Ramos B, S.; Camargo R, C. [UNAM, Instituto de Ciencias Nucleares, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Uribe, R. M. [Kent State University, College of Technology, Kent OH (United States); Gomez V, V. [UNAM, Instituto de Quimica, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Kobayashi, K., E-mail: negron@nucleares.unam.mx [Yokohama National University (Japan)

2014-08-15

The aim of this work is to analyze the interactions of 5 MeV electron beam radiation and a 290 MeV/u Carbon beam with calcium carbonate (powder) at 298 K and at different irradiation doses, for the potential use of calcium carbonate as a high-dose dosimeter. The irradiation doses with the electron beam were from 0.015 to 9 MGy, and with Carbon beam from 1.5 kGy to 8 kGy. High-energy radiation induces the formation of free radicals in solid calcium carbonate that can be detected and measured by electron paramagnetic resonance (EPR). An increase of the EPR response for some of the free radicals produced in the sample was observed as a function of the irradiation dose. The response of one of the radicals decreased with the dose. These measurements are reproducible; the preparation of the sample is simple and inexpensive; and the signal is stable for several months. The response curves show that the dosimeter tends to saturate at 10 MGy. Based on these properties, we propose this chemical compound as a high-dose dosimeter, mainly for electron irradiation. (author)

Effects of calcium carbonate and hydroxyapatite on zinc and iron retention in postmenopausal women

International Nuclear Information System (INIS)

Dawson-Hughes, B.; Seligson, F.H.; Hughes, V.A.

1986-01-01

We measured the effect of calcium carbonate and hydroxyapatite on whole-body retention of zinc-65 in 11 and iron-59 in 13 healthy, postmenopausal women. In a single-blind, controlled, crossover study, each subject, on three occasions, ingested a standard test meal supplemented with iron-59 or zinc-65 and capsules containing placebo or 500 mg elemental calcium as calcium carbonate or hydroxyapatite. Whole-body countings were performed prior to, 30 min after, and 2 wk after each meal. Mean (SEM) zinc retention was 18.1 +/- 1.0% with placebo (control) and did not vary significantly with calcium carbonate (110.0 +/- 8.6% of control) or hydroxyapatite (106.0 +/- 7.9% of control). Iron retention, 6.3 +/- 2.0% with placebo, was significantly reduced with both calcium carbonate (43.3 +/- 8.8% of control, p = 0.002) and hydroxyapatite (45.9 +/- 10.0% of control, p = 0.003). Iron absorption may be significantly reduced when calcium supplements are taken with meals

Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications

DEFF Research Database (Denmark)

Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari

2017-01-01

enzymatically with CaCO3 , Mg-enriched CaCO3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing...

Calcium carbonate microspheres as carriers for the anticancer drug camptothecin

Energy Technology Data Exchange (ETDEWEB)

Qiu, Neng [Division of Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow, G12 8LT (United Kingdom); State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041 (China); Department of Bio-pharmaceutical Engineering, School of Chemical Engineering, Sichuan University, Chengdu ,610065 (China); Yin, Huabing, E-mail: huabing.yin@glasgow.ac.uk [Division of Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow, G12 8LT (United Kingdom); Ji, Bozhi; Klauke, Norbert; Glidle, Andrew [Division of Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow, G12 8LT (United Kingdom); Zhang, Yongkui; Song, Hang [Department of Bio-pharmaceutical Engineering, School of Chemical Engineering, Sichuan University, Chengdu ,610065 (China); Cai, Lulu; Ma, Liang; Wang, Guangcheng [State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041 (China); Chen, Lijuan, E-mail: lijuan17@hotmail.com [State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041 (China); Wang, Wenwen [State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041 (China)

2012-12-01

Biogenic calcium carbonate has come to the attention of many researchers as a promising drug delivery system due to its safety, pH sensitivity and the large volume of information already in existence on its medical use. In this study, we employed bovine serum albumin (BSA) as an additive to synthesize a series of porous calcium carbonate microspheres (CCMS). These spheres, identified as vaterite, are stable both in aqueous solutions and organic solvents. Camptothecin, an effective anticancer agent, was loaded into the CCMS by simple diffusion and adsorption. The camptothecin loaded CCMS showed sustained cell growth inhibitory activity and a pH dependent release of camptothecin. With a few hours, the release is negligible under physiological conditions (pH = 7.4) but almost complete at pH 4 to 6 (i.e. pHs found in lysosomes and solid tumor tissue respectively). These findings suggest that porous, biogenic calcium carbonate microspheres could be promising carriers for the safe and efficient delivery of anticancer drugs of low aqueous solubility. - Highlights: Black-Right-Pointing-Pointer BSA-doped calcium carbonate microspheres with porous structure were prepared. Black-Right-Pointing-Pointer Camptothecin was encapsulated in the spherical microparticles with encapsulation efficiency up to 11%. Black-Right-Pointing-Pointer The release of encapsulated camptothecin is pH dependent Black-Right-Pointing-Pointer In vitro studies showed an effective anticancer activity of the camptothecin- microspheres.

The reductive decomposition of calcium sulphate I. Kinetics of the apparent solid-solid reaction

NARCIS (Netherlands)

Kamphuis, B.; Potma, A.W.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

1992-01-01

The reductive decomposition of calcium sulphate by hydrogen is used for the regeneration of calcium-based atmospheric fluidized bed combustion (AFBC) SO2 sorbents. The apparent solid¿solid reaction between CaS and CaSO4, one of the steps involved in the reaction mechanism of the reductive

Layer-by-Layer Assembled Nanotubes as Biomimetic Nanoreactors for Calcium Carbonate Deposition.

Science.gov (United States)

He, Qiang; Möhwald, Helmuth; Li, Junbai

2009-09-17

Enzyme-loaded magnetic polyelectrolyte multilayer nanotubes prepared by layer-by-layer assembly combined with the porous template could be used as biomimetic nanoreactors. It is demonstrated that calcium carbonate can be biomimetically synthesized inside the cavities of the polyelectrolyte nanotubes by the catalysis of urease, and the size of the calcium carbonate precipitates was controlled by the cavity dimensions. The metastable structure of the calcium carbonate precipitates inside the nanotubes was protected by the outer shell of the polyelectrolyte multilayers. These features may allow polyelectrolyte nanotubes to be applied in the fields of nanomaterials synthesis, controlled release, and drug delivery. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of calcium carbonate on hardening, physicochemical properties, and in vitro degradation of injectable calcium phosphate cements.

NARCIS (Netherlands)

Sariibrahimoglu, K.; Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Yubao, L.; Jansen, J.A.

2012-01-01

The main disadvantage of apatitic calcium phosphate cements (CPCs) is their slow degradation rate, which limits complete bone regeneration. Carbonate (CO(3)(2)(-)) is the common constituent of bone and it can be used to improve the degradability of the apatitic calcium phosphate ceramics. This study

The Effect of Cell Immobilization by Calcium Alginate on Bacterially Induced Calcium Carbonate Precipitation

Directory of Open Access Journals (Sweden)

Mostafa Seifan

2017-10-01

Full Text Available Microbially induced mineral precipitation is recognized as a widespread phenomenon in nature. A diverse range of minerals including carbonate, sulphides, silicates, and phosphates can be produced through biomineralization. Calcium carbonate (CaCO3 is one of the most common substances used in various industries and is mostly extracted by mining. In recent years, production of CaCO3 by bacteria has drawn much attention because it is an environmentally- and health-friendly pathway. Although CaCO3 can be produced by some genera of bacteria through autotrophic and heterotrophic pathways, the possibility of producing CaCO3 in different environmental conditions has remained a challenge to determine. In this study, calcium alginate was proposed as a protective carrier to increase the bacterial tolerance to extreme environmental conditions. The model showed that the highest concentration of CaCO3 is achieved when the bacterial cells are immobilized in the calcium alginate beads fabricated using 1.38% w/v Na-alginate and 0.13 M CaCl2.

Sintesa Precipitated Calcium Carbonate (PCC) dari Cangkang Kerang Darah (Anadara Granosa) dengan Variasi Ukuran Partikel dan Waktu Karbonasi

OpenAIRE

Rahmawati, Lucy; Amri, Amun; Zultiniar, Zultiniar; Yelmida, Yelmida

2015-01-01

Precipitated Calcium Carbonate (PCC) is a product of the processing of natural materials containing calcium carbonate resulting from the precipitation process with high purity. Bloodcockle shell can be used as a source of calcium for precipitated Calcium Carbonate. The purpose of this study to produce PCC of waste shells blood with carbonation method and determine the particle size of the PCC and the best carbonation time. Synthesis performed using carbonation method by adding nitric acid to ...

Biocompatibility of bio based calcium carbonate nanocrystals ...

African Journals Online (AJOL)

Background: Currently, there has been extensive research interest for inorganic nanocrystals such as calcium phosphate, iron oxide, silicone, carbon nanotube and layered double hydroxide as a drug delivery system especially in cancer therapy. However, toxicological screening of such particles is paramount importance ...

Effect of Ultrasound on Calcium Carbonate Crystallization

NARCIS (Netherlands)

Wagterveld, R.M.

2013-01-01

Scaling comprises the formation of hard mineral deposits on process or membrane equipment and calcium carbonate is the most common scaling salt. Especially in reverse osmosis (RO) membrane systems, scale formation has always been a serious limitation, causing flux decline, membrane degradation, loss

Production of precipitated calcium carbonate from industrial byproduct slags; Saostetun kalsiumkarbonaatin tuotanto karbonaattivapaista kuonatuotteista (SLAG2PCC)

Energy Technology Data Exchange (ETDEWEB)

Zevenhoven, R. [Aabo Akademi, Turku (Finland). Heat Engineering Lab.; Teir, S.; Eloneva, S.; Savolahti, J. [Helsinki Univ. of Technology, Espoo (Finland). Energy Technology and Environmental Protection

2006-12-19

Production of precipitate calcium carbonate from industrial by- product slags-project, 'SLAG2PCC', is a spin-off from ClimBus technology programme CO{sub 2} Nordic Plus-project, financed by the Finnish Technology Agency Tekes and the Finnish Recovery Boiler Committee. 'SLAG2PCC'-project is financed by Tekes, Ruukki Productions, UPM Kymmene and Waertsilae Finland. The possibility to produce precipitated calcium carbonate, PCC, from carbonate free industrial by-products (slags), combined with binding of carbon dioxide for climate change mitigation is studied in this project. The suitability of a process found from the literature, in which calcium used for carbonation is dissolved from calcium silicates using acetic acid as a solvent, is investigated for the carbonation of slags from the steel industry. During the calcium extraction experiments performed in the CO2 Nordic Plus - project it was found out that calcium is rapidly extracted from blast furnace and basic oxygen furnace slags. Atmospheric carbonation of the solution containing the dissolved slag and acetic acid directly has not succeeded yet due to low pH of the solution. Addition of NaOH, to increase of the solution pH, resulted in calcium carbonate precipitate in atmospheric pressure. The future goal of the project is to optimize process conditions so that the formed calcium carbonate is suitable for use as PCC. (orig.)

The skeletal organic matrix from Mediterranean coral Balanophyllia europaea influences calcium carbonate precipitation.

Science.gov (United States)

Goffredo, Stefano; Vergni, Patrizia; Reggi, Michela; Caroselli, Erik; Sparla, Francesca; Levy, Oren; Dubinsky, Zvy; Falini, Giuseppe

2011-01-01

Scleractinian coral skeletons are made mainly of calcium carbonate in the form of aragonite. The mineral deposition occurs in a biological confined environment, but it is still a theme of discussion to what extent the calcification occurs under biological or environmental control. Hence, the shape, size and organization of skeletal crystals from the cellular level through the colony architecture, were attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth. The skeleton contains an intra-skeletal organic matrix (OM) of which only the water soluble component was chemically and physically characterized. In this work that OM from the skeleton of the Balanophyllia europaea, a solitary scleractinian coral endemic to the Mediterranean Sea, is studied in vitro with the aim of understanding its role in the mineralization of calcium carbonate. Mineralization of calcium carbonate was conducted by overgrowth experiments on coral skeleton and in calcium chloride solutions containing different ratios of water soluble and/or insoluble OM and of magnesium ions. The precipitates were characterized by diffractometric, spectroscopic and microscopic techniques. The results showed that both soluble and insoluble OM components influence calcium carbonate precipitation and that the effect is enhanced by their co-presence. The role of magnesium ions is also affected by the presence of the OM components. Thus, in vitro, OM influences calcium carbonate crystal morphology, aggregation and polymorphism as a function of its composition and of the content of magnesium ions in the precipitation media. This research, although does not resolve the controversy between environmental or biological control on the deposition of calcium carbonate in corals, sheds a light on the role of OM, which appears mediated by the presence of magnesium ions.

The Skeletal Organic Matrix from Mediterranean Coral Balanophyllia europaea Influences Calcium Carbonate Precipitation

Science.gov (United States)

Goffredo, Stefano; Vergni, Patrizia; Reggi, Michela; Caroselli, Erik; Sparla, Francesca; Levy, Oren; Dubinsky, Zvy; Falini, Giuseppe

2011-01-01

Scleractinian coral skeletons are made mainly of calcium carbonate in the form of aragonite. The mineral deposition occurs in a biological confined environment, but it is still a theme of discussion to what extent the calcification occurs under biological or environmental control. Hence, the shape, size and organization of skeletal crystals from the cellular level through the colony architecture, were attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth. The skeleton contains an intra-skeletal organic matrix (OM) of which only the water soluble component was chemically and physically characterized. In this work that OM from the skeleton of the Balanophyllia europaea, a solitary scleractinian coral endemic to the Mediterranean Sea, is studied in vitro with the aim of understanding its role in the mineralization of calcium carbonate. Mineralization of calcium carbonate was conducted by overgrowth experiments on coral skeleton and in calcium chloride solutions containing different ratios of water soluble and/or insoluble OM and of magnesium ions. The precipitates were characterized by diffractometric, spectroscopic and microscopic techniques. The results showed that both soluble and insoluble OM components influence calcium carbonate precipitation and that the effect is enhanced by their co-presence. The role of magnesium ions is also affected by the presence of the OM components. Thus, in vitro, OM influences calcium carbonate crystal morphology, aggregation and polymorphism as a function of its composition and of the content of magnesium ions in the precipitation media. This research, although does not resolve the controversy between environmental or biological control on the deposition of calcium carbonate in corals, sheds a light on the role of OM, which appears mediated by the presence of magnesium ions. PMID:21799830

Histologic and immunohistochemical evaluation of biocompatibility of castor oil polyurethane polymer with calcium carbonate in equine bone tissue.

Science.gov (United States)

Nóbrega, Fernanda S; Selim, Mariana B; Arana-Chavez, Victor E; Correa, Luciana; Ferreira, Márcio P; Zoppa, André L V

2017-10-01

OBJECTIVE To evaluate the efficacy of castor oil polyurethane polymer with calcium carbonate for use in a unicortical ostectomy on the dorsal surface of the third metacarpal bone of horses. ANIMALS 6 adult horses. PROCEDURES A unicortical ostectomy was created on the dorsal surface of both third metacarpal bones of each horse. Castor bean (Ricinus communis) oil polyurethane polymer with calcium carbonate was implanted into the ostectomy on 1 limb, and the ostectomy of the contralateral limb was left unfilled and served as a control sample. Ostectomy sites were evaluated histologically 120 days later. Biopsy specimens were obtained from the interface of bone and polymer or the interface of bone and newly formed tissue; specimens were processed for histomorphometric evaluation by use of light microscopy, immunohistochemical analysis, histochemical analysis, and transmission electron microscopy. RESULTS Osteoconductive activity of the biomaterial was confirmed by the presence of osteoblasts in the biopsy specimens. Absence of a chronic inflammatory response or foreign body reaction indicated biocompatibility. Expression of osteoblast markers was detected in the newly formed tissue. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that castor oil polyurethane polymer with calcium carbonate could be an acceptable compound for use as a bone substitute in horses with fractures in which bone filling is necessary.

Sorption behavior of Zn(II) ions on synthetic apatitic calcium phosphates

Science.gov (United States)

Sebei, Haroun; Pham Minh, Doan; Nzihou, Ange; Sharrock, Patrick

2015-12-01

The synthesis, characterization and the reactivity of apatitic calcium phosphates (Ca-HA, chemical formula Ca10(PO4)6(OH)2) is reported. Calcium carbonate (CaCO3) and potassium dihydrogen orthophosphate (KH2PO4) were selected as economical starting materials for the synthesis of Ca-HA under atmospheric conditions. Monocalcium phosphate monohydrate (MCPM), dicalcium phosphate dihydrate (DCPD), and octacalcium phosphate pentahydrate (OCP) were identified as the main intermediates of the synthesis reaction. The product obtained after 48 h of reaction contains mainly low-crystalline Ca-HA and small amounts of other calcium phosphates such as octacalcium phosphate (OCP), B-type carbonate apatite (CAP), as well as unreacted calcium carbonate. This Ca-HA was found to be active for the removal of Zn2+ from an aqueous solution. Its sorption capacity reached up to 120 mg of Zn2+ per g of Ca-HA powder after 24 h of reaction. The monitoring of soluble Zn, Ca and P during the sorption experiment allowed characterizing the mechanism of Zn uptake. Dissolution-precipitation, ionic exchange and surface complexation are the three main mechanisms involved in the sorption processes. The contribution of these mechanisms is discussed in detail.

Determination of cholesterol, calcium carbonate and bilirubinate of gallstone

International Nuclear Information System (INIS)

Iqbal, Y.; Nazneen, B.I.

2004-01-01

Gallstones of seven patients were collected from different parts of North West Frontier and Punjab provinces. These stones were analyzed using Liebermann-Burchard method, estimation technique and Microlab-200 for cholesterol, calcium carbonate (CaCO/sub 3/) and bilirubinate respectively. The levels of cholesterol bilirubinate and CaCO/sub 3/ were found in the ranges of 50-81, 12-40 and 7-19% respectively. All of the stones were found to be mixed type stones that contain cholesterol, bilirubinate and calcium carbonate. The structures of the stones are also shown in the picture, which confirm our analysis data. Possible reasons, which cause formation of gallstones, are discussed in this paper. (author)

Molecular dynamics study of the solvation of calcium carbonate in water.

Science.gov (United States)

Bruneval, Fabien; Donadio, Davide; Parrinello, Michele

2007-10-25

We performed molecular dynamics simulations of diluted solutions of calcium carbonate in water. To this end, we combined and tested previous polarizable models. The carbonate anion forms long-living hydrogen bonds with water and shows an amphiphilic character, in which the water molecules are expelled in a region close to its C(3) symmetry axis. The calcium cation forms a strongly bound ion pair with the carbonate. The first hydration shell around the CaCO(3) pair is found to be very similar to the location of the water molecules surrounding CaCO(3) in ikaite, the hydrated mineral.

Physical and chemical protection of soil organic carbon in three agricultural soils with different contents of calcium carbonate

International Nuclear Information System (INIS)

Clough, A.; Skjemstad, J.O.

2000-01-01

The amount of organic carbon physically protected by entrapment within aggregates and through polyvalent cation organic matter bridging was determined on non-calcareous and calcareous soils. The composition of organic carbon in whole soils and 13 C NMR analysis. High energy photo-oxidation was carried out on <53 μm fractions and results from the NMR spectra showed 17-40% of organic carbon was in a condensed aromatic form, most likely charcoal (char). The concept that organic material remaining after photo-oxidation may be physically protected within aggregates was investigated by treating soils with a mild acid prior to photo-oxidation. More organic material was protected in the calcareous than the non-calcareous soils, regardless of whether the calcium occurred naturally or was an amendment. Acid treatment indicated that the presence of exchangeable calcium reduced losses of organic material upon photo-oxidation by about 7% due to calcium bridging. These results have implications for N fertiliser recommendations based upon organic carbon content. Firstly, calcium does not impact upon degradability of organic material to an extent likely to affect N fertiliser recommendations. Secondly, standard assessment techniques overestimate active organic carbon content in soils with high char content. Copyright (2000) CSIRO Publishing

Image-based Modeling of Biofilm-induced Calcium Carbonate Precipitation

Science.gov (United States)

Connolly, J. M.; Rothman, A.; Jackson, B.; Klapper, I.; Cunningham, A. B.; Gerlach, R.

2013-12-01

Pore scale biological processes in the subsurface environment are important to understand in relation to many engineering applications including environmental contaminant remediation, geologic carbon sequestration, and petroleum production. Specifically, biofilm induced calcium carbonate precipitation has been identified as an attractive option to reduce permeability in a lasting way in the subsurface. This technology may be able to replace typical cement-based grouting in some circumstances; however, pore-scale processes must be better understood for it to be applied in a controlled manor. The work presented will focus on efforts to observe biofilm growth and ureolysis-induced mineral precipitation in micro-fabricated flow cells combined with finite element modelling as a tool to predict local chemical gradients of interest (see figure). We have been able to observe this phenomenon over time using a novel model organism that is able to hydrolyse urea and express a fluorescent protein allowing for non-invasive observation over time with confocal microscopy. The results of this study show the likely existence of a wide range of local saturation indices even in a small (1 cm length scale) experimental system. Interestingly, the locations of high predicted index do not correspond to the locations of higher precipitation density, highlighting the need for further understanding. Figure 1 - A micro-fabricated flow cell containing biofilm-induced calcium carbonate precipitation. (A) Experimental results: Active biofilm is in green and dark circles are calcium carbonate crystals. Note the channeling behavior in the top of the image, leaving a large hydraulically inactive area in the biofilm mass. (B) Finite element model: The prediction of relative saturation of calcium carbonate (as calcite). Fluid enters the system at a low saturation state (blue) but areas of high supersaturation (red) are predicted within the hydraulically inactive area in the biofilm. If only effluent

Performance of Separation Processes for Precipitated Calcium Carbonate Produced with an Innovative Method from Steelmaking Slag and Carbon Dioxide

Energy Technology Data Exchange (ETDEWEB)

Teir, Sebastian, E-mail: sebastian.teir@vtt.fi [VTT Technical Research Centre of Finland Ltd., Espoo (Finland); Auvinen, Toni [Outotec Dewatering Technology Center, Lappeenranta (Finland); Said, Arshe [Department of Energy Technology, School of Engineering, Aalto University, Espoo (Finland); Kotiranta, Tuukka; Peltola, Heljä [Outotec Research Center, Pori (Finland)

2016-02-22

In this work, experiments were performed to determine the filterability of calcium carbonate produced with an alternative calcium carbonate production concept. The concept uses steelmaking slag as raw material and has potential to fix CO{sub 2} emissions and utilize steelmaking slag, simultaneously. As calcium carbonate is precipitated in a solution containing ammonium chloride, calcium chloride, and ammonia, the product needs to be washed and hence filtered. In this work, different separation processes, including washing, filtering, and drying, were tested on two calcium carbonate slurries produced from steel converter slag and CO{sub 2} by a laboratory-scale pilot facility, with the aim of obtaining a solid product with a low chloride content using a minimum amount of washing water. The order of maximum filtration rates achievable of the calcium carbonate slurries was determined by experimental work. The tests included pressure filtration and vacuum filtration and the test series contained altogether 21 different filtration cycles with varying combinations of filtering, washing, and drying steps. The filtered cakes were analyzed by their residual moisture content, chloride content, and conductivity, and the filtrates by their residual solids content, chloride content, and conductivity. Pressure filtration gave a high capacity (400–460 kg/m{sup 2}h) and a low cake residual moisture content (12–14 wt-%). Vacuum filtration gave slightly higher filtration rates (500–610 kg/m{sup 2}h at the lowest residual chloride contents of the cakes), but the cake residual moisture also stayed higher (25–26 wt-%). As the vacuum filtration tests used a filter cloth with higher permeability than that of the pressure filtration tests, a slightly higher filtration rate was expected. However, both filtration technologies seem suitable for filtering and washing calcium carbonate prepared with the studied method as a residual chloride content as low as 10 ppm of the filtered

The influence of carbon source and calcium on the production of ...

African Journals Online (AJOL)

use

2011-12-10

Dec 10, 2011 ... The influence of carbon source and calcium on the production of ... Furthermore, since the middle lamella contains high levels of calcium, it was thought that it may play an important ..... Processing of the pectate lyase PelI by ...

Citrate effects on amorphous calcium carbonate (ACC) structure, stability, and crystallization

DEFF Research Database (Denmark)

Tobler, Dominique Jeanette; Rodriguez Blanco, Juan Diego; Dideriksen, Knud

2015-01-01

Understanding the role of citrate in the crystallization kinetics of amorphous calcium carbonate (ACC) is essential to explain the formation mechanisms, stabilities, surface properties, and morphologies of CaCO3 biominerals. It also contributes to deeper insight into fluid-mineral inte......Understanding the role of citrate in the crystallization kinetics of amorphous calcium carbonate (ACC) is essential to explain the formation mechanisms, stabilities, surface properties, and morphologies of CaCO3 biominerals. It also contributes to deeper insight into fluid...

Factors affecting the precipitation of pure calcium carbonate during the direct aqueous carbonation of flue gas desulfurization gypsum

International Nuclear Information System (INIS)

Song, Kyungsun; Jang, Young-Nam; Kim, Wonbaek; Lee, Myung Gyu; Shin, Dongbok; Bang, Jun-Hwan; Jeon, Chi Wan; Chae, Soo Chun

2014-01-01

The mineral carbonation of FGD (flue gas desulfurization) gypsum was carried out through CO 2 sorption into ammonia solution containing FGD gypsum. High-purity calcium carbonate was precipitated from DCC (dissolved calcium carbonate) solution which was extracted during the induction period. The factors affecting the preparation of pure calcium carbonate were examined under the following conditions: CO 2 flow rate (1–3 L/min), ammonia content (4–12%), and S/L (solid-to-liquid) ratio (5–300 g/L). X-Ray diffraction study revealed that the PCC (precipitated calcium carbonate) was round-shaped vaterite. The induction time for PCC decreased as the CO 2 flow rate increased. The maximum formation efficiency for pure PCC was seen to increase linearly with the ammonia content. The formation efficiency for pure PCC was the highest (90%) for S/L ratio of 5 g/L but it decreased as S/L ratio increased. On the other hand, S/L ratio didn't affect the maximum solubility limit of DCC. It is believed that the pure PCC would add an economic value to the FGD gypsum carbonation for industrial CO 2 sequestration. - Highlights: • Pure and white CaCO 3 was synthesized using induction period during direct carbonation of FGD gypsum. • Its formation efficiency was increased with ammonia content but decreased with solid-to-liquid ratio. • This method is expected to extend to other industrial CO 2 sequestration for the enhanced economic value of precipitated CaCO 3

One-pot Synthesis of Bio-inspired Layered Materials of 3D Graphene Network/Calcium Carbonate

Institute of Scientific and Technical Information of China (English)

ZHANG Jing; FU Zhengyi; YAO Bin; PING Hang; YU Hongjian; ZHANG Fan; ZHANG Jinyong; WANG Yucheng; WANG Hao; WANG Weimin

2017-01-01

A bio-inspired layered material of reduced graphene oxide (RGOs) and calcium carbonate was synthesized via a one-pot strategy in DMF/H2O mixed solvent. The experimental results show that the product is a layered material of wrinkled RGOs networks and micron-sized calcium carbonate particles with uniform granular diameter and homogeneous morphology, which are distributed between the layered gallery of the graphene scaffold. The polymorph and the morphology of the in-situ produced calcium carbonate particles can be manipulated by simply changing the temperature scheme. Besides, the graphene oxide was reduced to a certain extent, and the hierarchical wrinkles were generated in the RGOs layer by the in-situ formation of the calcium carbonate particles. This work provides a facile and controllable strategy for synthesizing layered material of RGOs and carbonates, and also presents a platform for making three-dimensional porous wrinkled RGOs networks.

Study of Factors Related to Magnetic Treatment of Calcium Carbonate Saturated Water

National Research Council Canada - National Science Library

Lambert, Kevin

1998-01-01

..., calcium carbonate concentration and number of magnetic device attached. XRD of crystals gave relative proportions of calcite and aragonite present and XRF measured transition metals and elements known to substitute for calcium in scale...

Effects of Montmorillonite on the Mineralization and Cementing Properties of Microbiologically Induced Calcium Carbonate

Directory of Open Access Journals (Sweden)

Tao Chen

2017-01-01

Full Text Available Carbonate mineralization microbe is a microorganism capable of decomposing the substrate in the metabolic process to produce the carbonate, which then forms calcium carbonate with calcium ions. By taking advantage of this process, contaminative uranium tailings can transform to solid cement, where calcium carbonate plays the role of a binder. In this paper, we have studied the morphology of mineralized crystals by controlling the mineralization time and adding different concentrations of montmorillonite (MMT. At the same time, we also studied the effect of carbonate mineralized cementation uranium tailings by controlling the amount of MMT. The results showed that MMT can regulate the crystal morphology of calcium carbonate. What is more, MMT can balance the acidity and ions in the uranium tailings; it also can reduce the toxicity of uranium ions on microorganisms. In addition, MMT filling in the gap between the uranium tailings made the cement body more stable. When the amount of MMT is 6%, the maximum strength of the cement body reached 2.18 MPa, which increased by 47.66% compared with that the sample without MMT. Therefore, it is reasonable and feasible to use the MMT to regulate the biocalcium carbonate cemented uranium tailings.

Evaluation of the attachment, proliferation, and differentiation of osteoblast on a calcium carbonate coating on titanium surface

Energy Technology Data Exchange (ETDEWEB)

Liu Yi; Jiang Tao; Zhou Yi; Zhang Zhen; Wang Zhejun [Key Laboratory for Oral Biomedical Engineering, Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China); Tong Hua; Shen Xinyu [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Wang Yining, E-mail: wang.yn@whu.edu.cn [Key Laboratory for Oral Biomedical Engineering, Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China)

2011-07-20

Titanium has been reported to have some limitations in dental and orthopaedic clinical application. This study described a coating process using a simple chemical method to prepare calcium carbonate coatings on smooth titanium (STi) and sandblasted and acid-etched titanium (SATi), and evaluated the biological response of the materials in vitro. The surfaces of STi, SATi, calcium carbonate coated STi (CC-STi) and calcium carbonate coated SATi (CC-SATi) were characterized for surface roughness, contact angles, surface morphology and surface chemistry. The morphology of MG63 cells cultured on the surfaces was observed by SEM and Immuno-fluorescence staining. Cell attachment/proliferation was assessed by MTT assay, and cell differentiation was evaluated by alkaline phosphatase (ALP) activity. MG63 was found to attach favorably to calcium carbonate crystals with longer cytoplasmic extensions on CC-STi and CC-SATi, resulting in lower cell proliferation but higher ALP activity when compared to STi and SATi respectively. Moreover, CC-SATi is more favorable than CC-STi in terms of biological response. In conclusion, the calcium carbonate coatings on titanium were supposed to improve the osteointegration process and stimulate osteoblast differentiation, especially in early stage. And this method could possibly be a feasible alternative option for future clinical application. Highlights: {yields} Calcium carbonate coatings were prepared on titanium substrates. {yields} The coating process is simple and cost-effective. {yields} Calcium carbonate coating could induce differentiation toward an osteoblastic phenotype. {yields} Calcium carbonate coating could enhance the osteointegration process especially in early stage.

Neutralization of acid-mine water with calcium-carbonate

CSIR Research Space (South Africa)

Maree, JP

1994-01-01

Full Text Available Traditionally, Lime is used for the neutralization of acidic effluents. Calcium carbonate should be considered as an alternative because of considerations such as lower cost, low solubility at pH values greater than 7 and simple dosing system...

Tamarind (Tamarindus indica) fruit shell carbon: A calcium-rich promising adsorbent for fluoride removal from groundwater

International Nuclear Information System (INIS)

Sivasankar, V.; Rajkumar, S.; Murugesh, S.; Darchen, A.

2012-01-01

Highlights: ► The carbonization of Tamarind fruit shell improved its defluoridation efficiency. ► Calcium carbonate particles were involved in the defluoridation process. ► Adsorbent dose, pH, and fluoride concentration showed significant effects. ► Maximum adsorption of fluoride was achieved at pH 7–8. ► Prepared carbons were efficient in treating three natural waters. - Abstract: Tamarindus indica fruit shells (TIFSs) are naturally calcium rich compounds. They were impregnated with ammonium carbonate and then carbonized, leading to ammonium carbonate activated ACA-TIFS carbon. The resulting materials and carbon arising from virgin fruit shells V-TIFS were characterized and assayed as adsorbent for the removal of fluoride anions from groundwater. The fluoride scavenging ability of TIFS carbons was due to naturally dispersed calcium compounds. X-ray diffraction (XRD) showed that TIFS carbon contained a mixture of calcium oxalate and calcium carbonate. Batch studies on the fluoride removal efficiency of TIFS carbons with respect to contact time, pH, initial fluoride concentration, and co-ion interference were conducted. Applicability of various kinetic models (viz., pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich) and sorption isotherms were tested for batch techniques. The fluoride removal capacity of TIFS carbons was found to be 91% and 83% at a pH of 7.05 for V-TIFS and ACA-TIFS carbons, respectively. The practical applicability of TIFS carbons using groundwater samples was approved. The fluoride removal was greater in groundwater without hydrogen carbonate ions than those containing these ions. The characterizations of fluoride unloaded and loaded TIFS carbons were done by SEM and XRD studies.

Cascade enzymatic reactions for efficient carbon sequestration.

Science.gov (United States)

Xia, Shunxiang; Zhao, Xueyan; Frigo-Vaz, Benjamin; Zheng, Wenyun; Kim, Jungbae; Wang, Ping

2015-04-01

Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5 mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA. Copyright © 2015 Elsevier Ltd. All rights reserved.

Process Optimization for Ethyl Ester Production in Fixed Bed Reactor Using Calcium Oxide Impregnated Palm Shell Activated Carbon (CaO/PSAC

Directory of Open Access Journals (Sweden)

A Buasri

2012-11-01

Full Text Available : The continuous production of ethyl ester was studied by using a steady-state fixed bed reactor (FBR. Transesterification of palm stearin (PS and waste cooking palm oil (WCPO with ethanol in the presence of calcium oxide impregnated palm shell activated carbon (CaO/PSAC solid catalyst was investigated. This work was determined the optimum conditions for the production of ethyl ester from PS and WCPO in order to obtain fatty acid ethyl ester (FAEE with the highest yield. The effects of reaction variables such as residence time, ethanol/oil molar ratio, reaction temperature, catalyst bed height and reusability of catalyst in a reactor system on the yield of biodiesel were considered. The optimum conditions were the residence time 2-3 h, ethanol/oil molar ratio 16-20, reaction temperature at 800C, and catalyst bed height 300 mm which yielded 89.46% and 83.32% of the PS and WCPO conversion, respectively. CaO/PSAC could be used repeatedly for 4 times without any activation treatment and no obvious activity loss was observed. It has potential for industrial application in the transesterification of triglyceride (TG. The fuel properties of biodiesel were determined. Keywords: biodiesel, calcium oxide, ethyl ester, fixed bed reactor, palm shell activated carbon

Selection of a carbon-14 fixation form

International Nuclear Information System (INIS)

Scheele, R.D.; Burger, L.L.

1982-09-01

This report summarizes work on the selection of a disposal form for carbon-14 produced during the production of nuclear power. Carbon compounds were screened on the basis of solubility, thermal stability, resistance to oxidation, cost and availability, compatibility with the selected disposal matrix, leach resistance when incorporated in concrete, and compatibility with capture technologies. Carbonates are the products of the various technologies presently considered for carbon-14 capture. The alkaline earth carbonates exhibit the greatest thermal stabilities, lowest solubilities, lowest raw material cost, and greatest raw material availabilities. When reactions with cement and its impurities are considered, calcium and strontium carbonates are the only alkaline earth carbonates resistant to hydrolysis and reaction with sulfate. Leaching tests of barium, calcium, lead, potassium, and strontium carbonates in concrete showed calcium carbonate concrete to be slightly superior to the other alkaline earth carbonates, and greatly superior to a soluble carbonate, potassium carbonate, and lead carbonate. None of the additives to the concrete reduced the carbonate leaching. Acidic CO 2 -containing waters were found to greatly increase carbonate leaching from concrete. Sea water was found to leach less carbon from carbonate concretes than either distilled water or Columbia River water, which showed nearly equivalent leaching. Based on our work, calcium, barium, and strontium carbonates in concrete are the most suitable waste forms for carbon-14, with calcium carbonate concrete slightly superior to the others. If the waste form is to be exposed to natural waters, sea water will have the lowest leach rate. 6 figures, 7 tables

Commentary: Ex Situ Aqueous Mineral Carbonation

Energy Technology Data Exchange (ETDEWEB)

Gadikota, Greeshma, E-mail: gadikota@princeton.edu [Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ (United States)

2016-05-26

CO{sub 2} conversion to calcium and magnesium carbonates has garnered considerable attention since it is a thermodynamically downhill pathway to safely and permanently sequester large quantities of CO{sub 2}. This seminal work performed at The National Energy Technology Laboratory in Albany (NETL-Albany) reports the conversion of calcium- and magnesium-bearing silicate minerals, such as olivine [(Mg, Fe){sub 2}SiO{sub 4}], wollastonite (CaSiO{sub 3}), and serpentine [Mg{sub 3}Si{sub 2}O{sub 5}(OH){sub 4}], as they are reacted with CO{sub 2} in an aqueous environment to form magnesium or calcium carbonates. This paper discusses various pretreatment methods of the starting materials, such as grinding or heat treatment of hydroxylated Mg silicates, to enhance the reaction kinetics. The effects of various chemical additives (e.g., NaCl and NaHCO{sub 3}), and reaction parameters, such as temperature, pressure, and reaction time, on the conversion are investigated. Feasibility assessments and energy and economic analyses of the direct carbonation of calcium- and magnesium-bearing minerals are presented.

Effects of functional groups and soluble matrices in fish otolith on calcium carbonate mineralization

Energy Technology Data Exchange (ETDEWEB)

Ren Dongni; Li Zhuo; Gao Yonghua; Feng Qingling, E-mail: biomater@mail.tsinghua.edu.c [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

2010-10-01

Calcium carbonate mineralization is significantly influenced by organic matrices in vivo. The effect mainly relies on functional groups in proteins. In order to study the influence of functional groups on calcium carbonate mineralization, -OH, -NH{sub 2} and -COOH groups were grafted onto single crystal silicon chips, and such modified chips were used as substrates in in vitro mineralization experiments. An x-ray photoelectron spectroscopy (XPS) test was conducted to examine the grafting efficiency, and the three groups were successfully grafted. Calcium carbonate mineralization on a modified silicon substrate was examined by a scanning electron microscope (SEM) and x-ray diffraction (XRD), and the results showed that the effects of -OH, -NH{sub 2} and -COOH groups were quite different. Furthermore, a water-soluble protein matrix (WSM) and an acid-soluble protein matrix (ASM) extracted from fish otolith were adsorbed onto the -COOH-modified silicon substrate, and the effects of the protein matrices on calcium carbonate mineralization were studied. The results showed that both WSM and ASM of lapillus could mediate aragonite crystallization, but the size and morphology of the formed crystals were different. The WSM and ASM of asteriscus adsorbed on the silicon substrate had little effect on calcium carbonate mineralization; almost all the crystals were calcite, while both asteriscus WSM and ASM in solution could mediate vaterite crystals, and the morphologies of vaterite crystal aggregates were different.

Effects of functional groups and soluble matrices in fish otolith on calcium carbonate mineralization

International Nuclear Information System (INIS)

Ren Dongni; Li Zhuo; Gao Yonghua; Feng Qingling

2010-01-01

Calcium carbonate mineralization is significantly influenced by organic matrices in vivo. The effect mainly relies on functional groups in proteins. In order to study the influence of functional groups on calcium carbonate mineralization, -OH, -NH 2 and -COOH groups were grafted onto single crystal silicon chips, and such modified chips were used as substrates in in vitro mineralization experiments. An x-ray photoelectron spectroscopy (XPS) test was conducted to examine the grafting efficiency, and the three groups were successfully grafted. Calcium carbonate mineralization on a modified silicon substrate was examined by a scanning electron microscope (SEM) and x-ray diffraction (XRD), and the results showed that the effects of -OH, -NH 2 and -COOH groups were quite different. Furthermore, a water-soluble protein matrix (WSM) and an acid-soluble protein matrix (ASM) extracted from fish otolith were adsorbed onto the -COOH-modified silicon substrate, and the effects of the protein matrices on calcium carbonate mineralization were studied. The results showed that both WSM and ASM of lapillus could mediate aragonite crystallization, but the size and morphology of the formed crystals were different. The WSM and ASM of asteriscus adsorbed on the silicon substrate had little effect on calcium carbonate mineralization; almost all the crystals were calcite, while both asteriscus WSM and ASM in solution could mediate vaterite crystals, and the morphologies of vaterite crystal aggregates were different.

Effects of functional groups and soluble matrices in fish otolith on calcium carbonate mineralization.

Science.gov (United States)

Ren, Dongni; Li, Zhuo; Gao, Yonghua; Feng, Qingling

2010-10-01

Calcium carbonate mineralization is significantly influenced by organic matrices in vivo. The effect mainly relies on functional groups in proteins. In order to study the influence of functional groups on calcium carbonate mineralization, -OH, -NH2 and -COOH groups were grafted onto single crystal silicon chips, and such modified chips were used as substrates in in vitro mineralization experiments. An x-ray photoelectron spectroscopy (XPS) test was conducted to examine the grafting efficiency, and the three groups were successfully grafted. Calcium carbonate mineralization on a modified silicon substrate was examined by a scanning electron microscope (SEM) and x-ray diffraction (XRD), and the results showed that the effects of -OH, -NH2 and -COOH groups were quite different. Furthermore, a water-soluble protein matrix (WSM) and an acid-soluble protein matrix (ASM) extracted from fish otolith were adsorbed onto the -COOH-modified silicon substrate, and the effects of the protein matrices on calcium carbonate mineralization were studied. The results showed that both WSM and ASM of lapillus could mediate aragonite crystallization, but the size and morphology of the formed crystals were different. The WSM and ASM of asteriscus adsorbed on the silicon substrate had little effect on calcium carbonate mineralization; almost all the crystals were calcite, while both asteriscus WSM and ASM in solution could mediate vaterite crystals, and the morphologies of vaterite crystal aggregates were different.

Chemical reactions confined within carbon nanotubes.

Science.gov (United States)

Miners, Scott A; Rance, Graham A; Khlobystov, Andrei N

2016-08-22

In this critical review, we survey the wide range of chemical reactions that have been confined within carbon nanotubes, particularly emphasising how the pairwise interactions between the catalysts, reactants, transition states and products of a particular molecular transformation with the host nanotube can be used to control the yields and distributions of products of chemical reactions. We demonstrate that nanoscale confinement within carbon nanotubes enables the control of catalyst activity, morphology and stability, influences the local concentration of reactants and products thus affecting equilibria, rates and selectivity, pre-arranges the reactants for desired reactions and alters the relative stability of isomeric products. We critically evaluate the relative advantages and disadvantages of the confinement of chemical reactions inside carbon nanotubes from a chemical perspective and describe how further developments in the controlled synthesis of carbon nanotubes and the incorporation of multifunctionality are essential for the development of this ever-expanding field, ultimately leading to the effective control of the pathways of chemical reactions through the rational design of multi-functional carbon nanoreactors.

The effects of synthetic human secretin on calcium carbonate solubility in human bile.

Science.gov (United States)

Knyrim, K; Vakil, N

1990-11-01

This study sought to determine the effects of synthetic human secretin on ionized calcium and carbonate concentrations in human hepatic bile. Five patients with a nasobiliary drain in the right hepatic duct were studied. Three basal samples of bile were collected, each over a 15-minute period. Synthetic human secretin was then infused IV at 0.05 micrograms.kg-1.h-1 for 45 minutes followed by 0.5 micrograms.kg-1.h-1 for 45 minutes. Bile was sampled over 15-minute periods. To document return to baseline conditions, two further samples of bile were obtained over 15-minute periods 2 hours after the infusion was terminated. Bile acid concentration was determined by an enzymatic method; pH and PCO2 were measured with an automated analyzer. Total calcium was determined by inductively coupled plasma emission spectrometry and ionized calcium by an ion-specific electrode. Bicarbonate and carbonate concentrations were calculated using Henry's law and the Henderson-Hasselbalch equation. The fraction of bile sampled by the catheter was determined by Indocyanin Green recovery at the end of the experiment. Secretin caused an increase in bile flow and bicarbonate output. Bicarbonate concentrations increased from 26 +/- 3 mmol/L to 41 +/- 3 mmol/L (P less than 0.05), and chloride concentrations decreased. Mean bile acid concentrations declined significantly from 14.6 +/- 2 mmol/L to 4.7 +/- 1 mmol/L (P less than 0.05). Ionized calcium concentrations decreased from 0.7 +/- 0.005 mmol/L to 0.5 +/- 0.02 mmol/L (P less than 0.05) while pH increased significantly from 7.44 +/- 0.06 to 7.6 +/- 0.04 (P less than 0.05). Carbonate concentrations increased significantly from 0.15 +/- 0.02 mmol/L to 0.26 +/- 0.03 mmol/L, and the ion product for calcium carbonate increased significantly from 0.099 +/- 0.002 (mmol/L)2 to 0.135 +/- 0.015 (mmol/L)2 (P less than 0.05). Synthetic human secretin augments the ion product of calcium and carbonate in human hepatic bile, increasing the tendency for

Method for producing bio-fuel that integrates heat from carbon-carbon bond-forming reactions to drive biomass gasification reactions

Science.gov (United States)

Cortright, Randy D [Madison, WI; Dumesic, James A [Verona, WI

2011-01-18

A low-temperature catalytic process for converting biomass (preferably glycerol recovered from the fabrication of bio-diesel) to synthesis gas (i.e., H.sub.2/CO gas mixture) in an endothermic gasification reaction is described. The synthesis gas is used in exothermic carbon-carbon bond-forming reactions, such as Fischer-Tropsch, methanol, or dimethylether syntheses. The heat from the exothermic carbon-carbon bond-forming reaction is integrated with the endothermic gasification reaction, thus providing an energy-efficient route for producing fuels and chemicals from renewable biomass resources.

Single particle composition measurements of artificial Calcium Carbonate aerosols

Science.gov (United States)

Zorn, S. R.; Mentel, T. F.; Schwinger, T.; Croteau, P. L.; Jayne, J.; Worsnop, D. R.; Trimborn, A.

2012-12-01

Mineral dust, with an estimated total source from natural and anthropogenic emissions of up to 2800 Tg/yr, is one of the two largest contributors to total aerosol mass, with only Sea salt having a similar source strength (up to 2600 Tg/yr). The composition of dust particles varies strongly depending on the production process and, most importantly, the source location. Therefore, the composition of single dust particles can be used both to trace source regions of air masses as well as to identify chemical aging processes. Here we present results of laboratory studies on generating artificial calcium carbonate (CaCO3) particles, a model compound for carbonaceous mineral dust particles. Particles were generated by atomizing an aqueous hydrogen carbonate solution. Water was removed using a silica diffusion dryer., then the particles were processed in an oven at temperatures up to 900°C, converting the hydrogen carbonate to its anhydrous form. The resulting aerosol was analyzed using an on-line single particle laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF). The results confirm the conversion to calcium carbonate, and validate that the produced particles indeed can be used as a model compound for carbonaceous dust aerosols.

Chitosan Derivatives/Calcium Carbonate Composite Capsules Prepared by the Layer-by-Layer Deposition Method

Directory of Open Access Journals (Sweden)

Takashi Sasaki

2008-01-01

Full Text Available Core/shell capsules composed of calcium carbonate whisker core (rod-like shape and chitosan/chitosansulfate shell were prepared by the layer-by-layer deposition technique. Two chitosan samples of different molecular weights (Mw=9.7×104 and 1.09×106g·mol-1 were used as original materials. Hollow capsules were also obtained by dissolution of the core in hydrochloric acid. Electron microscopy revealed that the surface of the shell is rather ragged associated with some agglomerates. The shell thickness l obeys a linear relation with respect to the number of deposited layers m as l=md+a(a>0. The values of d (thickness per layer were 4.0 and 1.0 nm for the higher and lower Mw chitosan materials, respectively, both of which are greater than the thickness of the monolayer. The results suggest that the feature of the deposition does not obey an ideal homogeneous monolayer-by-monolayer deposition mechanism. Shell crosslinked capsules were also prepared via photodimerization reaction of cinnamoyl groups after a deposition of cinnamoyl chitosan to the calcium carbonate whisker core. The degree of crosslink was not enough to stabilize the shell structure, and hollow capsule was not obtained.

Buffering dissociation/formation reaction of biogenic calcium carbonate.

Science.gov (United States)

Ichikawa, Kazuhiko

2007-01-01

The oscillating stability of coral reef seawater pH has been maintained at around physiological pH values over the past 300 years (Pelejero et al., 2005). The stability mechanism of its pH has been interpreted in terms of the buffering dissolution/formation reaction of CaCO(3) as well as the proton consumption/generation reaction in CaCO(3)-saturated water. Here the pH-dependent solubility product [HCO(3)(-)][Ca(2+)] has been derived on the basis of the actual pH-dependent reactions for the atmospheric CO(2)/CO(2 (aq.))/HCO(3)(-)/CO(3)(2-)/Ca(2+)/CaCO(3) system. Overbasic pH peaks appeared between pH approximately 8 and approximately 9.5 during sodium hydroxide titration, as a result of simultaneous CaCO(3) formation and proton generation. The spontaneous and prompt water pH recovery from the acidic to the physiological range has been confirmed by the observation of acid/base time evolution, because of simultaneous CaCO(3) dissolution and proton consumption. The dissolution/formation of CaCO(3) in water at pH 7.5-9 does not take place without a proton consumption/generation reaction, or a buffering chemical reaction of HCO(3)(-)+Ca(2+)right arrow over left arrowCaCO(3)+H(+). SEM images of the CaCO(3) fragments showed that the acid water ate away at the CaCO(3) formed at physiological pH values. Natural coral reefs can thus recover the physiological pH levels of seawater from the acidic range through partial dissolution of their own skeletons.

Characterization of calcium carbonate sorbent particle in furnace environment

Energy Technology Data Exchange (ETDEWEB)

Lee, Kang Soo [Aerosol and Particle Technology Laboratory, Department of Mechanical Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Jung, Jae Hee [Environment Sensor System Research Center, KIST 39-1 Hawolgok-dong, Seongbuk-gu, Seoul, 136-791 (Korea, Republic of); Keel, Sang In; Yun, Jin Han; Min, Tai Jin [Environmental Systems Research Division, KIMM 104 Sinseongno, Yuseong-gu, Daejeon, 305-343 (Korea, Republic of); Kim, Sang Soo, E-mail: sskim@kaist.ac.kr [Aerosol and Particle Technology Laboratory, Department of Mechanical Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of)

2012-07-01

The oxy-fuel combustion system is a promising technology to control CO{sub 2} and NO{sub X} emissions. Furthermore, sulfation reaction mechanism under CO{sub 2}-rich atmospheric condition in a furnace may lead to in-furnace desulfurization. In the present study, we evaluated characteristics of calcium carbonate (CaCO{sub 3}) sorbent particles under different atmospheric conditions. To examine the physical/chemical characteristics of CaCO{sub 3}, which is used as a sorbent particle for in-furnace desulfurization in the oxy-fuel combustion system, they were injected into high temperature drop tube furnace (DTF). Experiments were conducted at varying temperatures, residence times, and atmospheric conditions in a reactor. To evaluate the aerosolizing characteristics of the CaCO{sub 3} sorbent particle, changes in the size distribution and total particle concentration between the DTF inlet and outlet were measured. Structural changes (e.g., porosity, grain size, and morphology) of the calcined sorbent particles were estimated by BET/BJH, XRD, and SEM analyses. It was shown that sorbent particles rapidly calcined and sintered in the air atmosphere, whereas calcination was delayed in the CO{sub 2} atmosphere due to the higher CO{sub 2} partial pressure. Instead, the sintering effect was dominant in the CO{sub 2} atmosphere early in the reaction. Based on the SEM images, it was shown that the reactions of sorbent particles could be explained as a grain-subgrain structure model in both the air and CO{sub 2} atmospheres.

Characterization of calcium carbonate sorbent particle in furnace environment

International Nuclear Information System (INIS)

Lee, Kang Soo; Jung, Jae Hee; Keel, Sang In; Yun, Jin Han; Min, Tai Jin; Kim, Sang Soo

2012-01-01

The oxy-fuel combustion system is a promising technology to control CO 2 and NO X emissions. Furthermore, sulfation reaction mechanism under CO 2 -rich atmospheric condition in a furnace may lead to in-furnace desulfurization. In the present study, we evaluated characteristics of calcium carbonate (CaCO 3 ) sorbent particles under different atmospheric conditions. To examine the physical/chemical characteristics of CaCO 3 , which is used as a sorbent particle for in-furnace desulfurization in the oxy-fuel combustion system, they were injected into high temperature drop tube furnace (DTF). Experiments were conducted at varying temperatures, residence times, and atmospheric conditions in a reactor. To evaluate the aerosolizing characteristics of the CaCO 3 sorbent particle, changes in the size distribution and total particle concentration between the DTF inlet and outlet were measured. Structural changes (e.g., porosity, grain size, and morphology) of the calcined sorbent particles were estimated by BET/BJH, XRD, and SEM analyses. It was shown that sorbent particles rapidly calcined and sintered in the air atmosphere, whereas calcination was delayed in the CO 2 atmosphere due to the higher CO 2 partial pressure. Instead, the sintering effect was dominant in the CO 2 atmosphere early in the reaction. Based on the SEM images, it was shown that the reactions of sorbent particles could be explained as a grain–subgrain structure model in both the air and CO 2 atmospheres.

Synthesis of porous poly(acrylamide hydrogels using calcium carbonate and its application for slow release of potassium nitrate

Directory of Open Access Journals (Sweden)

2009-05-01

Full Text Available Porous poly(acrylamide was synthesized using calcium carbonate microparticles and subsequent acid treatment to remove the calcium carbonate. Methylenebisacrylamide and ammonium persulfate/sodium metabisulfite were used as crosslinking agent and redox initiator, respectively. The porous structure of resulted hydrogels was confirmed using SEM micrographs. The effect of methylenebisacrylamide concentration and calcium carbonate amount on the swelling of the hydrogels was investigated. The results showed that the effect of methylenebisacrylamide and calcium carbonate variables on the swelling is reverse. The hydrogels were subsequently utilized for the loading of potassium nitrate. Potassium nitrate as active agent was loaded into hydrogels and subsequently the release of this active agent was investigated. In these series of investigation, the effect of content of loading, methylenebisacrylamide and calcium carbonate amount on the release of potassium nitrate from hydrogels was investigated.

The co-effect of collagen and magnesium ions on calcium carbonate biomineralization

International Nuclear Information System (INIS)

Jiao Yunfeng; Feng Qingling; Li Xiaoming

2006-01-01

The process of calcium carbonate biomineralization in the solution containing collagen and magnesium ions was studied in this paper. The results were characterized by using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect rules were obtained by the cooperation of collagen and magnesium ions in different concentration. The experiment results showed that in the presence of both collagen and magnesium ions, aragonite and vaterite were precipitated at low Mg/Ca ion concentration ratio, while only aragonite with regular spherical morphology was precipitated at high Mg/Ca ion concentration ratio. It indicated that collagen has a promotional effect on magnesium ions in controlling the polymorph of calcium carbonate crystal. A much wider range of calcium carbonate morphologies was observed in the presence of both collagen and magnesium ions. The experiments suggested that collagen acts in combination with magnesium ions to inhibit calcite crystal growth, while favoring the formation of aragonite crystals

Consumers’ Health-Related Motive Orientations and Reactions to Claims about Dietary Calcium

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Christine Hoefkens

2013-01-01

Full Text Available Health claims may contribute to better informed and healthier food choices and to improved industrial competitiveness by marketing foods that support healthier lifestyles in line with consumer preferences. With the more stringent European Union regulation of nutrition and health claims, insights into consumers’ health-related goal patterns and their reactions towards such claims are needed to influence the content of lawful claims. This study investigated how consumers’ explicit and implicit health-related motive orientations (HRMOs together with the type of calcium-claim (nutrition claim, health claim and reduction of disease risk claim influence perceived credibility and purchasing intention of calcium-enriched fruit juice. Data were collected in April 2006 through a consumer survey with 341 Belgian adults. The findings indicate that stronger implicit HRMOs (i.e., indirect benefits of calcium for personal health are associated with higher perceived credibility, which is not (yet translated into a higher purchasing intention. Consumers’ explicit HRMOs, which refer to direct benefits or physiological functions of calcium in the body — as legally permitted in current calcium-claims in the EU — do not associate with reactions to the claims. Independently of consumers’ HRMOs, the claim type significantly affects the perceived credibility and purchasing intention of the product. Implications for nutrition policy makers and food industries are discussed.

Calcium carbonate synthesis with prescribed properties based on liquid waste of soda production

OpenAIRE

E.O. Mikhailova; V.O. Panasenko; N.B. Markova

2016-01-01

A promising direction in solving of environmental problems of soda industry is the development of low-waste resource-saving technologies, which consist in recycling of valuable waste components with obtaining the commercial products. Aim: The aim is to establish the optimal conditions for obtaining calcium carbonate with prescribed properties from liquid waste of soda production. Materials and Methods: Chemically deposited calcium carbonate is used as filler and should have certain physical a...

Complexation/encapsulation of green tea polyphenols in mixed calcium carbonate and phosphate micro-particles.

Science.gov (United States)

Elabbadi, Amal; Jeckelmann, Nicolas; Haefliger, Olivier P; Ouali, Lahoussine

2011-01-01

We used a double-jet mixer to encapsulate water-soluble polyphenols, green tea extract (GTE), with calcium-based inorganic materials. The device mixed calcium chloride solutions with a solution of carbonate and phosphate in the presence of a GTE solution, and formed micro-particles which capture the GTE molecules. The micro-particles were analysed by liquid chromatography coupled to tandem mass spectroscopy to determine the encapsulation yield and loading of the different GTE components. We established correlations between (1) the efficiency of the GTE encapsulation and the composition of the mixed anion solutions and (2) the protonation degree of the ions and the molar ratio of calcium cations and carbonate/phosphate anions. An optimal and reproducible GTE loading of about 40% with an encapsulation yield of 65% was observed for a carbonate/phosphate molar composition of 4 : 1. In addition, our experimental results showed that the process is selective and favours the encapsulation of gallated species which form stronger complexes with calcium cations.

A thermodynamic solution model for calcium carbonate: Towards an understanding of multi-equilibria precipitation pathways.

Science.gov (United States)

Donnet, Marcel; Bowen, Paul; Lemaître, Jacques

2009-12-15

Thermodynamic solubility calculations are normally only related to thermodynamic equilibria in solution. In this paper, we extend the use of such solubility calculations to help elucidate possible precipitation reaction pathways during the entire reaction. We also estimate the interfacial energy of particles using only solubility data by a modification of Mersmann's approach. We have carried this out by considering precipitation reactions as a succession of small quasi-equilibrium states. Thus possible equilibrium precipitation pathways can be evaluated by calculating the evolution of surface charge, particle size and/or interfacial energy during the ongoing reaction. The approach includes the use of the Kelvin's law to express the influence of particle size on the solubility constant of precipitates, the use of Nernst's law to calculate surface potentials from solubility calculations and relate this to experimentally measured zeta potentials. Calcium carbonate precipitation and zeta potential measurements of well characterised high purity calcite have been used as a model system to validate the calculated values. The clarification of the change in zeta potential on titration illustrates the power of this approach as a tool for reaction pathway prediction and hence knowledge based tailoring of precipitation reactions.

Effect of changes in water salinity on ammonium, calcium, dissolved inorganic carbon and influence on water/sediment dynamics

Science.gov (United States)

López, P.

2003-04-01

The effect of a sudden increase in salinity from 10 to 37 in porewater concentration and the benthic fluxes of ammonium, calcium and dissolved inorganic carbon were studied in sediments of a small coastal lagoon, the Albufera d'Es Grau (Minorca Island, Spain). The temporal effects of the changes in salinity were examined over 17 days using a single diffusion-reaction model and a mass-balance approach. After the salinity change, NH 4+-flux to the water and Ca-flux toward sediments increased (NH 4+-flux: 5000-3000 μmol m -2 d -1 in seawater and 600/250 μmol m -2 d -1 in brackish water; Ca-flux: -40/-76 meq m -2 d -1 at S=37 and -13/-10 meq m -2 d -1 at S=10); however, later NH 4+-flux decreased in seawater, reaching values lower than in brackish water. In contrast, Ca-flux presented similar values in both conditions. The fluxes of dissolved inorganic carbon, which were constant at S=10 (55/45 mmol m -2 d -1), increased during the experiment at S=37 (from ˜30 mmol m -2 d -1 immediately after salinity increase to ˜60 mmol m -2 d -1 after 17 days). In brackish conditions, NH 4+ and Ca 2+ fluxes were consistent with a single diffusion-reaction model that assumes a zero-order reaction for NH 4+ production and a first-order reaction for Ca 2+ production. In seawater, this model explained the Ca-flux observed, but did not account for the high initial flux of NH 4+. The mass balance for 17 days indicated a higher retention of NH 4+ in porewater in the littoral station in seawater conditions (9.5 mmol m -2 at S=37 and 1.6 mmol m -2 at S=10) and a significant reduction in the water consumption at both sites (5 mmol m -2 at S=37; 35/23 mmol m -2 at S=10). In contrast, accumulation of dissolved inorganic carbon in porewater was lower in seawater incubations (-10/-1 meq m -2 at S=37; 50/90 meq m -2 at S=10) and was linked to a higher efflux of CO 2 to the atmosphere, because of calcium carbonate precipitation in water (675/500 meq m -2). These results indicate that increased

Effect of temperature on the reaction pathway of calcium carbonate formation via precursor phases

Science.gov (United States)

Purgstaller, Bettina; Mavromatis, Vasileios; Konrad, Florian; Dietzel, Martin

2016-04-01

It has been earlier postulated that some biogenic and sedimentary calcium carbonate (CaCO3) minerals (e.g. calcite and aragonite) are secondary in origin and have originally formed via a metastable calcium carbonate precursor phase (e.g. amorphous CaCO3, [1-2]). Such formation pathways are likely affected by various physicochemical parameters including aqueous Mg and temperature. In an effort to improve our understanding on the formation mechanism of CaCO3 minerals, precipitation experiments were carried out by the addition of a 0.6 M (Ca,Mg)Cl2 solution at distinct Mg/Ca ratios (1/4 and 1/8) into a 1 M NaHCO3 solution under constant pH conditions(8.3 ±0.1). The formation of CaCO3 was systematically examined as a function of temperature (6, 12, 18 and 25 ±0.3° C). During the experimental runs mineral precipitation was monitored by in situ Raman spectroscopy as well as by continuous sampling and analyzing of precipitates and reactive solutions. The results revealed two pathways of CaCO3 formation depending on the initial Mg/Ca ratio and temperature: (i) In experiments with a Mg/Ca ratio of 1/4 at ≤ 12° C as well as in experiments with a Mg/Ca ratio of 1/8 at ≤ 18° C, ikaite (CaCO3 6H2O) acts as a precursor phase for aragonite formation. (ii) In contrast higher temperatures induced the formation of Mg-rich amorphous CaCO3 (Mg-ACC) which was subsequently transformed to Mg-rich calcite. In situ Raman spectra showed that the transformation of Mg-ACC to Mg-calcite occurs at a higher rate (˜ 8 min) compared to that of ikaite to aragonite (> 2 h). Thus, the formation of aragonite rather than of Mg-calcite occurs due to the slower release of Ca2+and CO32- ions into the Mg-rich reactive solution during retarded ikaite dissolution. This behavior is generally consistent with the observation that calcite precipitation is inhibited at elevated aqueous Mg/Ca ratios. [1] Addadi L., Raz S. and Weiner S. (2003) Advanced Materials 15, 959-970. [2] Rodriguez-Blanco J. D

The Carbonation of Wollastonite: A Model Reaction to Test Natural and Biomimetic Catalysts for Enhanced CO2 Sequestration

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Fulvio Di Lorenzo

2018-05-01

Full Text Available One of the most promising strategies for the safe and permanent disposal of anthropogenic CO2 is its conversion into carbonate minerals via the carbonation of calcium and magnesium silicates. However, the mechanism of such a reaction is not well constrained, and its slow kinetics is a handicap for the implementation of silicate mineral carbonation as an effective method for CO2 capture and storage (CCS. Here, we studied the different steps of wollastonite (CaSiO3 carbonation (silicate dissolution → carbonate precipitation as a model CCS system for the screening of natural and biomimetic catalysts for this reaction. Tested catalysts included carbonic anhydrase (CA, a natural enzyme that catalyzes the reversible hydration of CO2(aq, and biomimetic metal-organic frameworks (MOFs. Our results show that dissolution is the rate-limiting step for wollastonite carbonation. The overall reaction progresses anisotropically along different [hkl] directions via a pseudomorphic interface-coupled dissolution–precipitation mechanism, leading to partial passivation via secondary surface precipitation of amorphous silica and calcite, which in both cases is anisotropic (i.e., (hkl-specific. CA accelerates the final carbonate precipitation step but hinders the overall carbonation of wollastonite. Remarkably, one of the tested Zr-based MOFs accelerates the dissolution of the silicate. The use of MOFs for enhanced silicate dissolution alone or in combination with other natural or biomimetic catalysts for accelerated carbonation could represent a potentially effective strategy for enhanced mineral CCS.

Laboratory study on the high-temperature capture of HCl gas by dry-injection of calcium-based sorbents.

Science.gov (United States)

Shemwell, B; Levendis, Y A; Simons, G A

2001-01-01

This is a laboratory study on the reduction of combustion-generated hydrochloric acid (HCl) emissions by in-furnace dry-injection of calcium-based sorbents. HCl is a hazardous gaseous pollutant emitted in significant quantities by municipal and hazardous waste incinerators, coal-fired power plants, and other industrial furnaces. Experiments were conducted in a laboratory furnace at gas temperatures of 600-1000 degrees C. HCl gas diluted with N2, and sorbent powders fluidized in a stream of air were introduced into the furnace concurrently. Chlorination of the sorbents occurred in the hot zone of the furnace at gas residence times approximately 1 s. The sorbents chosen for these experiments were calcium formate (CF), calcium magnesium acetate (CMA), calcium propionate (CP), calcium oxide (CX), and calcium carbonate (CC). Upon release of organic volatiles, sorbents calcine to CaO at approximately 700 degrees C, and react with the HCl according to the reaction CaO + 2HCl CaCl2 + H2O. At the lowest temperature case examined herein, 600 degrees C, direct reaction of HCl with CaCO3 may also be expected. The effectiveness of the sorbents to capture HCl was interpreted using the "pore tree" mathematical model for heterogeneous diffusion reactions. Results show that the thin-walled, highly porous cenospheres formed from the pyrolysis and calcination of CF, CMA, and CP exhibited high relative calcium utilization at the upper temperatures of this study. Relative utilizations under these conditions reached 80%. The less costly low-porosity sorbents, calcium carbonate and calcium oxide also performed well. Calcium carbonate reached a relative utilization of 54% in the mid-temperature range, while the calcium oxide reached an 80% relative utilization at the lowest temperature examined. The data matched theoretical predictions of sorbent utilization using the mathematical model, with activation energy and pre-exponential factors for the calcination reaction of 17,000 K and 300

Additional calcium carbonate into concentrate diet for sheep fed ensiled king grass as a based-diet

Directory of Open Access Journals (Sweden)

I-W Mathius

1997-10-01

Full Text Available In order to ascertain the effect of additional calcium carbonate into concentrate diet, on the performance of sheep fed ensiled king grass as a basal diet, a trial was conducted using 28 growing sheep ( average body weight 17 _+ 1 .4 kg. Based on body weight, the animals were grouped and randomized into four dietary treatments in block randomized design . Dietary treatments were (i chopped king grass + 400 g of concentrate, (ii ensiled king grass + 400 g concentrate + 0 % of calcium carbonate, (iii ensiled king grass + 400 g concentrate + 5 % calcium carbonate and (iv ensiled king grass + 400 g concentrate + 10 % calcium carbonate . Results showed that offering 5 % of calcium carbonate into concentrate diet increased (P 0 .05 for all groups . No differences in the apparent digestibility of the nutrient components were observed, but crude protein decreased significantly (P < 0 .05 . A significant relationship ( P < 0 .01 was found between nitrogen intake (NI and nitrogen retention (NR, and the equation was NR = - 0.1848 + 0.3788 NI ( r = 0.9 . Based on data found that feeding only ensiled king grass as a single diet could not meet the maintenance requirement of energy and protein, therefore, additional energy and crude protein sources is needed .

Precipitation of calcium carbonate in aqueous solutions in presence of ethylene glycol and dodecane.

Science.gov (United States)

Natsi, Panagiota D.; Rokidi, Stamatia; Koutsoukos, Petros G.

2015-04-01

The formation of calcium carbonate (CaCO3) in aqueous supersaturated solutions has been intensively studied over the past decades, because of its significance for a number of processes of industrial and environmental interest. In the oil and gas production industry the deposition of calcium carbonate affects adversely the productivity of the wells. Calcium carbonate scale deposits formation causes serious problems in water desalination, CO2 sequestration in subsoil wells, in geothermal systems and in heat exchangers because of the low thermal coefficient of the salt. Amelioration of the operational conditions is possible only when the mechanisms underlying nucleation and crystal growth of calcium carbonate in the aqueous fluids is clarified. Given the fact that in oil production processes water miscible and immiscible hydrocarbons are present the changes of the dielectric constant of the fluid phase has serious impact in the kinetics of calcium carbonate precipitation, which remains largely unknown. The problem becomes even more complicated if polymorphism exhibited by calcium carbonate is also taken into consideration. In the present work, the stability of aqueous solutions supersaturated with respect to all calcium carbonate polymorphs and the subsequent kinetics of calcium carbonate precipitation were measured. The measurements included aqueous solutions and solutions in the presence of water miscible (ethylene glycol, MEG) and water immiscible organics (n-dodecane). All measurements were done at conditions of sustained supersaturation using the glass/ Ag/AgCl combination electrode as a probe of the precipitation and pH as the master variable for the addition of titrant solutions with appropriate concentration needed to maintenance the solution supersaturation. Initially, the metastable zone width was determined from measurements of the effect of the solution supersaturation on the induction time preceding the onset of precipitation at free-drift conditions. The

Magnesium sulphate’s influence on calcium carbonate minerals

DEFF Research Database (Denmark)

Nielsen, Mia Rohde

The purpose of this PhD thesis was to explore the influence of magnesium sulphate (MgSO4 (aq)) on calcium carbonate (CaCO3) minerals and what role the MgSO40 ion pair had. CaCO3 minerals are abundant and widespread on Earth, particularly in marine environments, and have been so throughout Earth...

Reactions on carbon anodes in aluminium electrolysis

Energy Technology Data Exchange (ETDEWEB)

Eidet, Trygve

1997-12-31

The consumption of carbon anodes and energy in aluminium electrolysis is higher than what is required theoretically. This thesis studies the most important of the reactions that consume anode materials. These reactions are the electrochemical anode reaction and the airburn and carboxy reactions. The first part of the thesis deals with the kinetics and mechanism of the electrochemical anode reaction using electrochemical impedance spectroscopy. The second part deals with air and carboxy reactivity of carbon anodes and studies the effects of inorganic impurities on the reactivity of carbon anodes in the aluminium industry. Special attention is given to sulphur since its effect on the carbon gasification is not well understood. Sulphur is always present in anodes, and it is expected that the sulphur content of available anode cokes will increase in the future. It has also been suggested that sulphur poisons catalyzing impurities in the anodes. Other impurities that were investigated are iron, nickel and vanadium, which are common impurities in anodes which have been reported to catalyze carbon gasification. 88 refs., 92 figs., 24 tabs.

Obtainment of calcium carbonate from mussels shell; Obtencao de carbonato de calcio a partir de conchas de mariscos

Energy Technology Data Exchange (ETDEWEB)

Hamester, M.R.R.; Becker, D., E-mail: michele.rosa@sociesc.org.b [Sociedade Educacional de Santa Catarina (SOCIESC), Joinville, SC (Brazil). Mestrado Profissional em Engenharia Mecanica

2010-07-01

The mussels and oyster shell are discarded at environment, and this accumulation is causing negative consequences to ecosystem. Calcium carbonate is main constituent of the shell chemical composition. Aiming to reduce environmental aggression and generate income to shellfish producer, there was the possibility of using these shells as an alternative to commercial calcium carbonate. For this physics, chemicals and thermal properties were evaluated, using X-ray fluorescence, thermogravimetric analysis, size distribution, abrasiveness and scanning electronic microscopy. The results indicate that mussels shells have an initial degradation temperature higher than commercial calcium carbonate e same lost weight behavior and 95% of shell chemical composition is calcium carbonate. The sample size distribution was influenced by grinding condition and time as well as its abrasiveness. (author)

Calcium absorption and achlorhydria

International Nuclear Information System (INIS)

Recker, R.R.

1985-01-01

Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

Behaviour of calcium carbonate in sea water

Science.gov (United States)

Cloud, P.E.

1962-01-01

Anomalies in the behaviour of calcium carbonate in natural solutions diminish when considered in context. Best values found by traditional oceanographie methods for the apparent solubility product constant K'CaCO3 in sea water at atmospheric pressure are consistent mineralogically-at 36 parts per thousand salinity and T-25??C, K'aragonlte is estimated as 1.12 ?? 10-6 and K'calcite as 0.61 ?? 10-6. At 30??C the corresponding values are 0.98 ?? 10-6 for aragonite and 0.53 ?? 10-6 for calcite. Because the K' computations do not compensate for ionic activity, however, they cannot give thermodynamically satisfactory results. It is of interest, therefore, that approximate methods and information now available permit the estimation from the same basic data of an activity product constant KCaCO3 close to that found in solutions to which Debye-Hu??ckel theory applies. Such methods indicate approximate Karagonite 7.8 ?? 10-9 for surface sea water at 29??C; Kcalcite would be proportionately lower. Field data and experimental results indicate that the mineralogy of precipitated CaCO3 depends primarily on degree of supersaturation, thus also on kinetic or biologic factors that facilitate or inhibit a high degree of supersaturation. The shallow, generally hypersaline bank waters west of Andros Island yield aragonitic sediments with O18 O16 ratios that imply precipitation mainly during the warmer months, when the combination of a high rate of evaporation, increasing salinity (and ionic strength), maximal temperatures and photosynthetic removal of CO2 result in high apparent supersaturation. The usual precipitate from solutions of low ionic strength is calcite, except where the aragonite level of supersaturation is reached as a result of diffusion phenomena (e.g. dripstones), gradual and marked evaporation, or biologic intervention. Published data also suggest the possibility of distinct chemical milieus for crystallographic variations in skeletal calcium carbonate. It appears

Influence of substrate mineralogy on bacterial mineralization of calcium carbonate: implications for stone conservation.

Science.gov (United States)

Rodriguez-Navarro, Carlos; Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-06-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed.

Tuning calcium carbonate growth through physical confinement and templating with amyloid-like polypeptide aggregates

Science.gov (United States)

Colaco, Martin Francis

The creation of useful composite materials requires precise control of the interface between the components in order to tune the overall shape and material properties. Despite the current research into nanotechnology, our ability to create materials with nanoscale precision is nascent. However, nature has a paradigm for the creation of finely structured composites under mild conditions called biomineralization. Through control of protein template assembly, solution conditions, and physical confinement, organisms are able to create useful optical and structural materials, such as bones, teeth, and mollusk shells. The objective of this thesis is to elucidate the importance of these various controls in synthetic systems to further our ability to create nanostructured materials. We begin by examining the formation of self-assembled monolayers (SAMs) of organosilanes on silica oxides. The formation of functionalized surfaces can help control the mineralization of amorphous or crystalline calcium carbonate. Long-chained organosilanes organize on surfaces to form dense, solid-like films, with the terminal groups determining the hydrophobicity and stereochemistry of the film. Our work has shown that uniform hydrophobic and hydrophilic films can be formed by using cleaned silica over glass or mica and through a vapor phase reaction over a liquid one. Additionally, we showed that mixed SAMs with phase-separated domains could be created through the selection of organosilanes and reaction conditions. We have built on these functionalized surfaces through the use of microfabrication and a gas permeable polymer to create three-dimensionally confined microcrystallizers. Other researchers have shown that one-dimensional confinement with a multi-functional surface (patterned with a small nucleating ordered region in a disordered SAM) can stabilize the creation of an amorphous calcium carbonate film before a single, large, micropatterned crystal is grown. Our work has determined

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite

International Nuclear Information System (INIS)

Holopainen, Jani; Santala, Eero; Heikkilä, Mikko; Ritala, Mikko

2014-01-01

Calcium carbonate (CaCO 3 ) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO 3 ) 2 ·4H 2 O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO 3 fibers with average diameters from 140 to 290 nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO 3 layer by spin or dip coating Ca(NO 3 ) 2 /PVP precursor solution on the CaCO 3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO 3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings. - Highlights: • Calcium carbonate fibers were prepared by electrospinning. • The electrospun fibers crystallized to calcite upon calcination at 500 °C. • Spin and dip coating methods were used to improve the adhesion of the CaCO 3 fibers. • The CaCO 3 fibers were converted to hydroxyapatite by treatment in phosphate solution. • The hydroxyapatite fibers consisted of plate-like nanocrystals

Stabilization of amorphous calcium carbonate by controlling its particle size

NARCIS (Netherlands)

Nudelman, F.; Sonmezler, E.; Bomans, P.H.H.; With, de G.; Sommerdijk, N.A.J.M.

2010-01-01

Amorphous calcium carbonate (ACC) nanoparticles of different size are prepared using a flow system. Post-synthesis stabilization with a layer of poly[(a,ß)-DL-aspartic acid] leads to stabilization of the ACC, but only for particles

Calcium and organic matter removal by carbonation process with waste incineration flue gas towards improvement of leachate biotreatment performance.

Science.gov (United States)

Zhang, Cheng; Zhu, Xuedong; Wu, Liang; Li, Qingtao; Liu, Jianyong; Qian, Guangren

2017-09-01

Municipal solid wastes incineration (MSWI) flue gas was employed as the carbon source for in-situ calcium removal from MSWI leachate. Calcium removal efficiency was 95-97% with pH of 10.0-11.0 over 100min of flue gas aeration, with both bound Ca and free Ca being removed effectively. The fluorescence intensity of tryptophan, protein-like and humic acid-like compounds increased after carbonation process. The decrease of bound Ca with the increase of precipitate indicated that calcium was mainly converted to calcium carbonate precipitate. It suggested that the interaction between dissolved organic matter and Ca 2+ was weakened. Moreover, 10-16% of chemical oxygen demand removal and the decrease of ultraviolet absorption at 254nm indicated that some organics, especially aromatic compound decreased via adsorption onto the surface of calcium carbonate. The results indicate that introduce of waste incineration flue gas could be a feasible way for calcium removal from leachate. Copyright © 2017 Elsevier Ltd. All rights reserved.

Purifications of calcium carbonate and molybdenum oxide powders for neutrinoless double beta decay experiment, AMoRE

International Nuclear Information System (INIS)

Park, HyangKyu

2015-01-01

The AMoRE (Advanced Mo based Rare process Experiment) collaboration is going to use calcium molybdate crystals to search for neutrinoless double beta decay of 100 Mo isotope. In order to make the crystal, we use calcium carbonate and molybdenum oxide powders as raw materials. Therefore it is highly necessary to reduce potential sources for radioactive backgrounds such as U and Th in the powders. In this talk, we will present our studies for purification of calcium carbonate and molybdenum oxide powders

Summary of ENDF/B-V evaluations for carbon, calcium, iron, copper, and lead and ENDF/B-V Revision 2 for calcium and iron

Energy Technology Data Exchange (ETDEWEB)

Fu, C Y

1982-09-01

This report, together with documents already published, describes the ENDF/B-V evaluations of the neutron and gamma-ray-production cross sections for carbon, calcium, iron, copper, and lead and the ENDF/B-V Revision 2 evaluations for calcium and iron.

The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite.

Science.gov (United States)

Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Benning, Liane G

2011-01-01

The kinetics and mechanisms of nanoparticulate amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range of environmentally relevant temperatures (7.5-25 °C) using synchrotron-based in situ time-resolved Energy Dispersive X-ray Diffraction (ED-XRD) in conjunction with high-resolution electron microscopy, ex situ X-ray diffraction and infrared spectroscopy. The crystallization process occurs in two stages; firstly, the particles of ACC rapidly dehydrate and crystallize to form individual particles of vaterite; secondly, the vaterite transforms to calcite via a dissolution and reprecipitation mechanism with the reaction rate controlled by the surface area of calcite. The second stage of the reaction is approximately 10 times slower than the first. Activation energies of calcite nucleation and crystallization are 73±10 and 66±2 kJ mol(-1), respectively. A model to calculate the degree of calcite crystallization from ACC at environmentally relevant temperatures (7.5-40 °C) is also presented.

Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic

Energy Technology Data Exchange (ETDEWEB)

He, Fupo, E-mail: fphebm@126.com [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Ren, Weiwei [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Tian, Xiumei [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China); Liu, Wei; Wu, Shanghua [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Chen, Xiaoming, E-mail: xmchenw@126.com [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China)

2016-07-01

In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4 week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. - Highlights: • A calcium carbonate composite ceramic (CC/PG) was acquired. • The in vivo response of CC/PG and biphasic calcium phosphate (BCP) was compared. • CC/PG showed faster in vitro degradation rate compared to BCP. • CC/PG showed less in vivo degradation and bone formation than BCP at week 4. • CC/PG had larger increment of degradation and bone formation than BCP at week 8.

Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic

International Nuclear Information System (INIS)

He, Fupo; Ren, Weiwei; Tian, Xiumei; Liu, Wei; Wu, Shanghua; Chen, Xiaoming

2016-01-01

In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4 week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. - Highlights: • A calcium carbonate composite ceramic (CC/PG) was acquired. • The in vivo response of CC/PG and biphasic calcium phosphate (BCP) was compared. • CC/PG showed faster in vitro degradation rate compared to BCP. • CC/PG showed less in vivo degradation and bone formation than BCP at week 4. • CC/PG had larger increment of degradation and bone formation than BCP at week 8.

Study of calcium forms and their effect in carbon stabilization in fertile soils by FTIR and XPS

International Nuclear Information System (INIS)

Araujo, J.R.; Assis, K.L.S.; Calil, V.L.; Souza, K.R.; Beltrao, M.S.S.; Sena, L.A.; Archanjo, B.S.; Achete, C.A.

2013-01-01

Organic matter or black carbon atoms of Terra Preta de Indio (Amazonian Dark Earth) soils are composed of oxidized carbon groups as phenols, epoxide, carbonyl and carboxyl groups in their surface. At the pH of soil, carboxylate groups are deprotonated generating carboxylate anions leaving the surface of these soils with negative charges. Calcium cations can interact with oxidized carbon groups by chemisorption interactions lowering the total system energy. In this work, Terra Preta de Indio was examined by X-ray photoelectron spectroscopy and Infrared spectroscopy in order to correlate its organic fraction rich in calcium with calcium containing samples. (author)

Study of calcium forms and their effect in carbon stabilization in fertile soils by FTIR and XPS

Energy Technology Data Exchange (ETDEWEB)

Araujo, J.R.; Assis, K.L.S.; Calil, V.L.; Souza, K.R.; Beltrao, M.S.S.; Sena, L.A.; Archanjo, B.S.; Achete, C.A., E-mail: jraraujo@inmetro.gov.br [Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Duque de Caxias, RJ (Brazil). Divisao de Materiais e Metrologia

2013-07-01

Organic matter or black carbon atoms of Terra Preta de Indio (Amazonian Dark Earth) soils are composed of oxidized carbon groups as phenols, epoxide, carbonyl and carboxyl groups in their surface. At the pH of soil, carboxylate groups are deprotonated generating carboxylate anions leaving the surface of these soils with negative charges. Calcium cations can interact with oxidized carbon groups by chemisorption interactions lowering the total system energy. In this work, Terra Preta de Indio was examined by X-ray photoelectron spectroscopy and Infrared spectroscopy in order to correlate its organic fraction rich in calcium with calcium containing samples. (author)

The influence of electron discharge and magnetic field on calcium carbonate (CaCO{sub 3}) precipitation

Energy Technology Data Exchange (ETDEWEB)

Putro, Triswantoro, E-mail: tris@physics.its.ac.id; Endarko, E-mail: endarko@physics.its.ac.id [Physics Department, Faculty of Mathematics and Natural Science Institut Teknologi Sepuluh Nopember (ITS), Surabaya 60111 (Indonesia)

2016-04-19

The influences of electron discharge and magnetic field on calcium carbonate (CaCO{sub 3}) precipitation in water have been successfully investigated. The study used three pairs of magnetic field 0.1 T whilst the electron discharge was generated from television flyback transformer type BW00607 and stainless steel SUS 304 as an electrode. The water sample with an initial condition of 230 mg/L placed in the reactor with flow rate 375 mL/minutes, result showed that the electron discharge can be reduced contain of calcium carbonate the water sample around 17.39% within 2 hours. Meanwhile for the same long period of treatment and flow rate, around 56.69% from initial condition of 520 mg/L of calcium carbonate in the water sample can be achieved by three pairs of magnetic field 0.1 T. When the combination of three pairs of magnetic field 0.1 T and the electron discharge used for treatment, the result showed that the combination of electron discharge and magnetic field methods can be used to precipitate calcium carbonate in the water sample 300 mg/L around 76.66% for 2 hours of treatment. The study then investigated the influence of the polar position of the magnetic field on calcium carbonate precipitation. Two positions of magnetic field were tested namely the system with alternated polar magnetics and the system without inversion of the polar magnetics. The influence of the polar position showed that the percentage reduction in levels of calcium carbonate in the water sample (360 mg/L) is significant different. Result showed that the system without inversion of the polar magnetics is generally lower than the system with alternated polar magnetics, with reduction level at 30.55 and 57.69%, respectively.

Reaction Mechanism of Calcium Hydroxide with Gaseous Hydrogen Chloride Mécanisme de réaction de l'hydroxyde de calcium avec de l'acide chlorhydrique gazeux

Directory of Open Access Journals (Sweden)

Allal K. M.

2006-12-01

Full Text Available The reduction of acid gas content in combustion or incineration flue gases can be carried out by reaction with dry, fine alkaline sorbents such as calcium oxide or calcium hydroxide. In the present work, in addition to the thermodynamic study of the different reactions involved in the dechlorination process, an experimental study to identify the reaction products by means of X-ray diffraction, electron microscopy and thermogravimetry has been carried out. It has been shown that the reaction of hydrochloric acid with hydrated lime leads to the formation of not only calcium chloride but calcium hydroxichloride. La diminution de la teneur en gaz acides dans les effluents provenant des unités de combustion ou d'incinération peut être accomplie en faisant réagir ces gaz polluants avec des absorbants alcalins tels que l'oxyde ou l'hydroxyde de calcium. Dans cet article, à l'étude thermodynamique des différentes réactions mises en jeu durant le processus de déchloruration, s'ajoute une étude expérimentale menant à l'identification des produits finaux en utilisant la diffraction X, la microscopie électronique ainsi que la thermogravimétrie. A l'issue de cette étude, il a été montré que la réaction de Ca(OH2 avec HCl entraîne la formation non seulement de CaCI2 mais aussi CaCIOH.

Geloina coaxans shell as calcium source on synthesis hydroxyapatite

Science.gov (United States)

Yanti, P. H.; Kamiah, A.

2018-04-01

Geloina coaxans shell (GCS) is one of mullusc shell mainly composed by calcium carbonate. In this work, calcium carbonate has been converted to calcium oxide by calcination at 1000°C for 12 hours. The calcined of geloina coaxans shell were treated with HNO3 to produce Ca(NO3)2 as calcium source on synthesis hydroxyapatite. Orthophosphoric acid (H3PO4) was used as phosphate donor. Reaction of Ca/P has been done by precipitation method at molar ratio of precursors of 1.67 and pH adjusted at 10 using NH4OH. The XRD result revealed that hydoxyapatite can be prepared at 3 M of HNO3 and stirring time for 240 minutes. Specific band of hydroxyapatite such as PO4 and OH observed using FTIR instrument. Analysis of crystal size using Schererr equation proved nanosize of powder hydroxyapatite can be produced.

Calcium carbonate concretions in caves : an overview

International Nuclear Information System (INIS)

Gewelt, M.; Ek, C.

1988-01-01

The scientific work of the last twenty years on calcium carbonate cave deposits (dripstones and flowstones) is presented. Recent studies on speleothems composition, growth, age and paleoclimatic environment are examined. Main new results are related with the development of isotopic and radiometric dating methods. Increasing numbers of dates allow for statistical speleothem repartition studies which could be related with paleoclimates. Two new frequency curves of U-series ages data of speleothems are given. (M.C.B.)

Investigation of CaO-CO₂ reaction kinetics by in-situ XRD using synchrotron radiation

Energy Technology Data Exchange (ETDEWEB)

Biasin, A.; Segre, C. U.; Salviulo, G.; Zorzi, F.; Strumendo, M. [Padova; (IIT)

2015-02-05

In this work, in-situ synchrotron radiation x-ray powder diffraction (SR-XRPD), performed at the Advanced Photon Source (APS) facilities of the Argonne National Laboratory, was applied to investigate the CaO–CO₂ reaction. A set of CO₂ absorption experiments were conducted in a high temperature reaction capillary with a controlled atmosphere (CO₂ partial pressure of 1 bar), in the temperature range between 450 °C and 750 °C using CaO based sorbents obtained by calcination of commercial calcium carbonate. The evolution of the crystalline phases during CO₂ uptake by the CaO solid sorbents was monitored for a carbonation time of 20 min as a function of the carbonation temperature and of the calcination conditions. The Rietveld refinement method was applied to estimate the calcium oxide conversion during the reaction progress and the average size of the initial (at the beginning of carbonation) calcium oxide crystallites. The measured average initial carbonation rate (in terms of conversion time derivative) of 0.280 s^-1 (±13.2% standard deviation) is significantly higher than the values obtained by thermo-gravimetric analysis and reported thus far in the literature. Additionally, a dependence of the conversion versus time curves on the initial calcium oxide crystallite size was observed and a linear relationship between the initial CaO crystallite size and the calcium oxide final conversion was identified.

Homogeneous calcium carbonate coating obtained by electrodeposition: in situ atomic force microscope observations

International Nuclear Information System (INIS)

Pavez, Jorge; Silva, Juan F.; Melo, Francisco

2005-01-01

The evolution of the first stages of the crystallization of an electrochemically deposited calcium carbonate on indium tin oxide (ITO) electrode has been investigated. The electrodeposition was driven applying a constant negative potential to a NaHCO 3 and CaCl 2 solution saturated with molecular oxygen. By this way, novel data about the kinetics of the crystal growth of CaCO 3 were collected from the AFM images. The results show that at the solution supersaturation levels used, the crystal growth occurred by a uniform surface nucleation mechanism. During the growth of the initial nuclei, the surface of the electrode was covered progressively by the growth of flat multilayers having triangular faces. The height of these structures ranged from one to several molecular layers of calcium carbonate. At the end of the crystallization process, the roughness of the electrode surface is reduced in average to two monolayers. Thus, our method provides a useful way to electrodeposit a nearly uniform layer of calcium carbonate on a variety of surfaces of potential applications

Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.

Science.gov (United States)

Parakhonskiy, B V; Svenskaya, Yu I; Yashchenok, A М; Fattah, H A; Inozemtseva, O A; Tessarolo, F; Antolini, R; Gorin, D A

2014-06-01

An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1μm. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions. Copyright © 2014 Elsevier B.V. All rights reserved.

On Calcium Carbonates: from Fundamental Research to Application

OpenAIRE

Brečević, Ljerka; Kralj, Damir

2007-01-01

Appearance of a solid phase from aqueous solution, known as precipitation, is responsible for the formation of numerous natural materials and technological products. Therefore, the knowledge on mechanisms of elementary processes involved in precipitation should be considered in the areas such as geology, oceanology, biomineralization, medicine, basic chemical and pharmaceutical industries, analytical and materials chemistry in particular. Calcium carbonates are a very suitable model system fo...

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite

Energy Technology Data Exchange (ETDEWEB)

Holopainen, Jani, E-mail: jani.holopainen@helsinki.fi; Santala, Eero; Heikkilä, Mikko; Ritala, Mikko

2014-12-01

Calcium carbonate (CaCO{sub 3}) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO{sub 3}){sub 2}·4H{sub 2}O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO{sub 3} fibers with average diameters from 140 to 290 nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO{sub 3} layer by spin or dip coating Ca(NO{sub 3}){sub 2}/PVP precursor solution on the CaCO{sub 3} fibers followed by annealing of the gel formed inside the fiber layer. The CaCO{sub 3} fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings. - Highlights: • Calcium carbonate fibers were prepared by electrospinning. • The electrospun fibers crystallized to calcite upon calcination at 500 °C. • Spin and dip coating methods were used to improve the adhesion of the CaCO{sub 3} fibers. • The CaCO{sub 3} fibers were converted to hydroxyapatite by treatment in phosphate solution. • The hydroxyapatite fibers consisted of plate-like nanocrystals.

Fractionated-combustion analysis of carbonate-containing phases in composite materials of the hydroxyapatite-calcium carbonate system

Science.gov (United States)

Goldberg, M. A.; Shibaeva, T. V.; Smirnov, V. V.; Kutsev, S. V.; Barinov, S. M.; Grigorovich, K. V.

2012-12-01

Materials in the hydroxyapatite (HA)-calcium carbonate (CC) system were synthesized by a precipitation method from aqueous solutions. According to the data of X-ray phase analysis and IR spectroscopy, the powders consisted of CC and AB-type carbonate-substituted HA (CHA). In order to determine the content of carbonate-containing phases in materials, the temperature-temporal mode of fractionated-combustion analysis of carbon was developed. The quantitative phase ratios and the degree of substitution of carbonate groups in CHA were determined. It was shown that the degree of substitution of carbonate groups in CHA increased from 2.47 to 5.31 wt % as the CC content increased from 13.50 to 88.33 wt %.

Precipitation diagram of calcium carbonate polymorphs: its construction and significance

International Nuclear Information System (INIS)

Kawano, Jun; Shimobayashi, Norimasa; Miyake, Akira; Kitamura, Masao

2009-01-01

In order to interpret the formation mechanism of calcium carbonate polymorphs, we propose and construct a new 'precipitation diagram', which has two variables: the driving force for nucleation and temperature. The precipitation experiments were carried out by mixing calcium chloride and sodium carbonate aqueous solutions. As a result, a calcite-vaterite co-precipitation zone, a vaterite precipitation zone, a vaterite-aragonite co-precipitation zone and an aragonite precipitation zone can be defined. Theoretical considerations suggest that the steady state nucleation theory can explain well the appearance of these four zones, and the first-order importance of the temperature dependency of surface free energy in the nucleation of aragonite. Furthermore, the addition of an impurity will likely result in the change of these energies, and this precipitation diagram gives a new basis for interpreting the nature of the polymorphs precipitated in both inorganic and biological environments.

Effect of carbonate and phosphate ratios on the transformation of calcium orthophosphates

Energy Technology Data Exchange (ETDEWEB)

Eliassi, Mohammad Daoud, E-mail: eliassi2007@gmail.com [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China); Zhao, Wei [State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling 712100 (China); Tan, Wen Feng, E-mail: wenfeng.tan@hotmail.com [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China)

2014-07-01

Graphical abstract: Complexes among phosphate, carbonate and calcium have been prepared via a facile hydrothermal route. The synthesized product at the low (0.15) and the high (1.8) molar ratio of PO{sub 4}{sup 3−}/CO{sub 3}{sup 2−} is calcium phosphate hydrate and hydroxylapatite (HAp), respectively. Molar ratios of PO{sub 4}{sup 3−}/CO{sub 3}{sup 2−} are effective on the reduction of carbonate activity during the crystallization of HAp. - Highlights: • Formation of different complexes from CO{sub 3}{sup 2−}, PO{sub 4}{sup 3−} and Ca{sup 2+} solutions at 60 °C. • Molar ratios of PO{sub 4}{sup 3−}/CO{sub 3}{sup 2} cause changes in phase and size of synthesized products. • Addition of PO{sub 4}{sup 3} inhibited the activity of CO{sub 3}{sup 2−} during bound with Ca{sup 2+}. • The phase transformation was completed, when CO{sub 3}{sup 2−} peaks disappeared in FTIR. • PO{sub 4}{sup 3−}, CO{sub 3}{sup 2−} and Ca{sup 2+} distributed heterogeneously on the surface of precipitation. - Abstract: Complexes among phosphate, carbonate and calcium have been synthesized by a designed hydrothermal method. Effects of carbonate and phosphate ratios on the transformation of calcium-orthophosphates were investigated. With X-ray diffraction measurement the synthesized product at the low (0.15) and the high (1.8) molar ratio of PO{sub 4}{sup 3−}/CO{sub 3}{sup 2−} is calcium phosphate hydrate at pH 9.0, and hydroxylapatite (HAp) at pH 8.0, respectively. Fourier transform infrared spectroscopy of product at the high ratio (1.8) of PO{sub 4}{sup 3−}/CO{sub 3}{sup 2−} shows that the CO{sub 3}{sup 2−} peaks disappear, and the strong peaks at 1412 and 1460 cm{sup −1} are assigned to the vibrations of PO{sub 4}{sup 3−} in HAp. {sup 31}P nuclear magnetic resonance spectra of products at the low (0.15–0.6) to the high (1.2–1.8) ratios of PO{sub 4}{sup 3−}/CO{sub 3}{sup 2−} are obtained at 2.9 and 2.7 ppm, respectively. Molar ratios of PO

Dissolution and secondary mineral precipitation in basalts due to reactions with carbonic acid

Science.gov (United States)

Kanakiya, Shreya; Adam, Ludmila; Esteban, Lionel; Rowe, Michael C.; Shane, Phil

2017-06-01

One of the leading hydrothermal alteration processes in volcanic environments is when rock-forming minerals with high concentrations of iron, magnesium, and calcium react with CO2 and water to form carbonate minerals. This is used to the advantage of geologic sequestration of anthropogenic CO2. Here we experimentally investigate how mineral carbonation processes alter the rock microstructure due to CO2-water-rock interactions. In order to characterize these changes, CO2-water-rock alteration in Auckland Volcanic Field young basalts (less than 0.3 Ma) is studied before and after a 140 day reaction period. We investigate how whole core basalts with similar geochemistry but different porosity, permeability, pore geometry, and volcanic glass content alter due to CO2-water-rock reactions. Ankerite and aluminosilicate minerals precipitate as secondary phases in the pore space. However, rock dissolution mechanisms are found to dominate this secondary mineral precipitation resulting in an increase in porosity and decrease in rigidity of all samples. The basalt with the highest initial porosity and volcanic glass volume shows the most secondary mineral precipitation. At the same time, this sample exhibits the greatest increase in porosity and permeability, and a decrease in rock rigidity post reaction. For the measured samples, we observe a correlation between volcanic glass volume and rock porosity increase due to rock-fluid reactions. We believe this study can help understand the dynamic rock-fluid interactions when monitoring field scale CO2 sequestration projects in basalts.

Studies on the alkali-silica reaction rim in a simplified calcium-alkali-silicate system

NARCIS (Netherlands)

Zheng, Kunpeng; Adriaensens, Peter; De Schutter, Geert; Ye, G.; Taerwe, Luc

2016-01-01

This work is intended to provide a better understanding about the properties and roles of the reaction rim in an alkali-silica reaction. A simplified calcium-alkali-silicate system was created to simulate the multiple interactions among reactive silica, alkaline solution and portlandite near the

Studies on structure and organization of calcium carbonate deposits in algae

Digital Repository Service at National Institute of Oceanography (India)

Kerkar, V.; Untawale, A.G.

The structure and organization of calcium carbonate deposits is studied in species of Halimeda, Udotea, Neomeris (Chlorophyta) and Padina (Phaeophyta). It was found that in Halimeda aragonite deposition takes place outside the cell wall...

Low dose human calcium assay in vivo via the 40Ca(n,α) reaction

International Nuclear Information System (INIS)

Bigler, R.E.; Laughlin, J.S.; Davis, R. Jr.; Evans, J.C.

1974-01-01

A compact medical cyclotron was investigated to elucidate its merit as a neutron source for both qualitative and quantitative activation analysis human studies in vivo of calcium and other elements within the human body and at reasonable radiation dose levels. Emphasis is given to those properties necessary for carrying out quantitative whole body calcium measurements using the 40 (n,α) 37 Ar reaction, which because of the low radiation dose and relatively modest equipment requirements, give this method potential for wide application in diagnostic studies of calcium metabolism. (U.S.)

Low dose human calcium assay in vivo via the 40Ca(n,α) reaction

International Nuclear Information System (INIS)

Bigler, R.E.; Davis, R. Jr.; Evans, J.C.

1974-01-01

A compact medical cyclotron has been investigated to elucidate its merit as a neutron source for both qualitative and quantitative activation analysis human studies in vivo of calcium and other elements within the human body and at reasonable radiation dose levels. Emphasis is given to those properties necessary for carrying out quantitative whole body calcium measurements using the 40 Ca(n, α) 37 Ar reaction, which because of the low radiation dose and relatively modest equipment requirements, give this method potential for wide application in diagnostic studies of calcium metabolism

Release of Crude Oil from Silica and Calcium Carbonate Surfaces

DEFF Research Database (Denmark)

Liu, Xiaoyan; Yan, Wei; Stenby, Erling Halfdan

2016-01-01

Adsorption and desorption of a North Sea crude oil to silica and calcium carbonate surfaces were studied by a quartz crystal microbalance, while the bare surfaces and adsorbed oil layers were characterized by atomic force microscopy and contact angle measurements. Water contact angles were measured...

Tissue reaction and material biodegradation of a calcium sulfate/apatite biphasic bone substitute in rat muscle

Directory of Open Access Journals (Sweden)

Jian-Sheng Wang

2016-07-01

Conclusion: Calcium sulfate hydroxyapatite bone substitute can be used as a carrier for antibiotics or other drugs, without adverse reaction due to the fast resorption of the calcium sulfate. No bone formation was seen despite treating the bone substitute with autologous bone marrow.

Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs

Science.gov (United States)

Sekkal, W.; Zaoui, A.

2013-04-01

Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99 J/m2) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2 J/m2, i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images.

Micro and colloidal stickie pacification with precipitated calcium carbonate

Science.gov (United States)

John H. Klungness; Roland L. Gleisner; Marguerite S. Sykes

2002-01-01

Colloidal stickies that build up in mill process water during pulping are problematic and difficult to remove. We examined precipitated calcium carbonate (PCC) as a means to ameliorate process water stickies. The effectiveness of PCC added directly into a slurry of deinked pulp was compared with in situ precipitation of PCC by the fiber loading method. We found that...

Microalgal bacterial flocs treating paper mill effluent: A sunlight-based approach for removing carbon, nitrogen, phosphorus, and calcium.

Science.gov (United States)

Van Den Hende, Sofie; Rodrigues, André; Hamaekers, Helen; Sonnenholzner, Stanislaus; Vervaeren, Han; Boon, Nico

2017-10-25

Treatment of upflow anaerobic sludge blanket (UASB) effluent from a paper mill in aerated activated sludge reactors involves high aeration costs. Moreover, this calcium-rich effluent leads to problematic scale formation. Therefore, a novel strategy for the aerobic treatment of paper mill UASB effluent in microalgal bacterial floc sequencing batch reactors (MaB-floc SBRs) is proposed, in which oxygen is provided via photosynthesis, and calcium is removed via bio-mineralization. Based on the results of batch experiments in the course of this study, a MaB-floc SBR was operated at an initial neutral pH. This SBR removed 58±21% organic carbon, 27±8% inorganic carbon, 77±5% nitrogen, 73±2% phosphorus, and 27±11% calcium. MaB-flocs contained 10±3% calcium, including biologically-influenced calcite crystals. The removal of calcium and inorganic carbon by MaB-flocs significantly decreased when inhibiting extracellular carbonic anhydrase (CA), an enzyme that catalyses the hydration and dehydration of CO 2 . This study demonstrates the potential of MaB-floc SBRs for the alternative treatment of calcium-rich paper mill effluent, and highlights the importance of extracellular CA in this treatment process. Copyright © 2017 Elsevier B.V. All rights reserved.

Decomposition pathways of polytetrafluoroethylene by co-grinding with strontium/calcium oxides.

Science.gov (United States)

Qu, Jun; He, Xiaoman; Zhang, Qiwu; Liu, Xinzhong; Saito, Fumio

2017-06-01

Waste polytetrafluoroethylene (PTFE) could be easily decomposed by co-grinding with inorganic additive such as strontium oxide (SrO), strontium peroxide (SrO 2 ) and calcium oxide (CaO) by using a planetary ball mill, in which the fluorine was transformed into nontoxic inorganic fluoride salts such as strontium fluoride (SrF 2 ) or calcium fluoride (CaF 2 ). Depending on the kind of additive as well as the added molar ratio, however, the reaction mechanism of the decomposition was found to change, with different compositions of carbon compounds formed. CO gas, the mixture of strontium carbonate (SrCO 3 ) and carbon, only SrCO 3 were obtained as reaction products respectively with equimolar SrO, excess SrO and excess SrO 2 to the monomer unit CF 2 of PTFE were used. Excess amount of CaO was needed to effectively decompose PTFE because of its lower reactivity compared with strontium oxide, but it promised practical applications due to its low cost.

Calcium Isotope Fractionation during Carbonate Weathering in the Northern Guangdong, South China

Science.gov (United States)

Liu, F.; Mao, G.; Wei, G.; Zhang, Z.

2017-12-01

CO2 is consumed during the weathering of carbonates, whereas carbonates are precipitated rapidly in the oceans, which are pivotal to modulate atmospheric CO2, oceanic pH and climate. Calcium carbonate in limestone is one of the largest reservoirs of carbon at the Earth's surface, so calcium is an important element that links the lithosphere, hydrosphere, biosphere, and the atmosphere. Compared with silicate rocks, carbonate rocks have more rapid rates of physical and chemical erosions, so the carbonate weathering will respond more quickly to the climatic changes. In the southeast of China, enormous of carbonate rocks are widely distributed. Due to the influence of the subtropical monsoon climate, the rocks experienced strong chemical weathering and pedogenic process, resulting in red weathering crust of carbonate rocks. This type of weathering crust is geochemistry-sensitive and ecology-vulnerable, which can provide important insights into the recycle of supergene geochemistry in the karst areas. In this study, we report calcium isotopic compositions of saprolites from a weathering profile developed on argillaceous carbonate rocks in northern Guangdong, South China. The acid-leachable fraction, which was extracted by 1N hydrochloride acid, showed limited variation of δ44/40Ca(NIST 915a) spanning from 0.55 ± 0.06‰ (2SD) to 0.72 ± 0.05‰ (2SD) despite CaO content ranging from 0.01 wt.% to 45.7 wt.%, implying that Ca isotope didn't fractionate much which may due to the congruent dissolution of limestone minerals. In contrast, radiogenic 87Sr/86Sr ratios of the whole rocks changed with depth from 0.710086 ± 6 (2SE) at the base rock to 0.722164± 8 (2SE) at the top-soil, which are possibly attributed to the mixing effect between carbonate and silicate fractions. Sr is an analogue for Ca due to its similar ionic size and charge; however, these two systems can differ in certain respects. The coupled study of Ca and Sr will be helpful to verify sources of Ca and the

Fabrication of calcite blocks from gypsum blocks by compositional transformation based on dissolution-precipitation reactions in sodium carbonate solution.

Science.gov (United States)

Ishikawa, Kunio; Kawachi, Giichiro; Tsuru, Kanji; Yoshimoto, Ayami

2017-03-01

Calcium carbonate (CaCO 3 ) has been used as a bone substitute, and is a precursor for carbonate apatite, which is also a promising bone substitute. However, limited studies have been reported on the fabrication of artificial calcite blocks. In the present study, cylindrical calcite blocks (ϕ6×3mm) were fabricated by compositional transformation based on dissolution-precipitation reactions using different calcium sulfate blocks as a precursor. In the dissolution-precipitation reactions, both CaSO 4 ·2H 2 O and CaSO 4 transformed into calcite, a polymorph of CaCO 3 , while maintaining their macroscopic structure when immersed in 1mol/L Na 2 CO 3 solution at 80°C for 1week. The diametral tensile strengths of the calcite blocks formed using CaSO 4 ·2H 2 O and CaSO 4 were 1.0±0.3 and 2.3±0.7MPa, respectively. The fabrication of calcite blocks using CaSO 4 ·2H 2 O and CaSO 4 proposed in this investigation may be a useful method to produce calcite blocks because of the self-setting ability and high temperature stability of gypsum precursors. Copyright © 2016 Elsevier B.V. All rights reserved.

Valorization of Calcium Carbonate-Based Solid Wastes for the Treatment of Hydrogen Sulfide from the Gas Phase

OpenAIRE

Pham Xuan , Huynh; Pham Minh , Doan; Galera Martinez , Marta; Nzihou , Ange; Sharrock , Patrick

2015-01-01

International audience; This paper focuses on the valorization of calcium carbonate-based solid wastes for theremoval of hydrogen sulfide from gas phase. Two solid wastes taken from industrial sites for theproduction of sodium carbonate and sodium bicarbonate by the Solvay process® were analyzedby different physico-chemical methods. Calcium carbonate was found as the main component ofboth the solid wastes. Trace amounts of other elements such as Mg, Al, Fe, Si, Cl, Na etc. werealso present in...

Hydration Effects on the Stability of Calcium Carbonate Pre-Nucleation Species

Directory of Open Access Journals (Sweden)

Alejandro Burgos-Cara

2017-07-01

Full Text Available Recent experimental evidence and computer modeling have shown that the crystallization of a range of minerals does not necessarily follow classical models and theories. In several systems, liquid precursors, stable pre-nucleation clusters and amorphous phases precede the nucleation and growth of stable mineral phases. However, little is known on the effect of background ionic species on the formation and stability of pre-nucleation species formed in aqueous solutions. Here, we present a systematic study on the effect of a range of background ions on the crystallization of solid phases in the CaCO3-H2O system, which has been thoroughly studied due to its technical and mineralogical importance, and is known to undergo non-classical crystallization pathways. The induction time for the onset of calcium carbonate nucleation and effective critical supersaturation are systematically higher in the presence of background ions with decreasing ionic radii. We propose that the stabilization of water molecules in the pre-nucleation clusters by background ions can explain these results. The stabilization of solvation water hinders cluster dehydration, which is an essential step for precipitation. This hypothesis is corroborated by the observed correlation between parameters such as the macroscopic equilibrium constant for the formation of calcium/carbonate ion associates, the induction time, and the ionic radius of the background ions in the solution. Overall, these results provide new evidence supporting the hypothesis that pre-nucleation cluster dehydration is the rate-controlling step for calcium carbonate precipitation.

Urea Hydrolysis and Calcium Carbonate Precipitation in Gypsum-Amended Broiler Litter.

Science.gov (United States)

Burt, Christopher D; Cabrera, Miguel L; Rothrock, Michael J; Kissel, D E

2018-01-01

Broiler () litter is subject to ammonia (NH) volatilization losses. Previous work has shown that the addition of gypsum to broiler litter can increase nitrogen mineralization and decrease NH losses due to a decrease in pH, but the mechanisms responsible for these effects are not well understood. Therefore, three laboratory studies were conducted to evaluate the effect of gypsum addition to broiler litter on (i) urease activity at three water contents, (ii) calcium carbonate precipitation, and (iii) pH. The addition of gypsum to broiler litter increased ammonium concentrations ( litter pH by 0.43 to 0.49 pH units after 5 d ( litter only increased on Day 0 for broiler litter with low (0.29 g HO g) and high (0.69 g HO g) water contents, and on Day 3 for litter with medium (0.40 g HO g) water content ( litter with gypsum also caused an immediate decrease in litter pH (0.22 pH units) due to the precipitation of calcium carbonate (CaCO) from gypsum-derived calcium and litter bicarbonate. Furthermore, as urea was hydrolyzed, more urea-derived carbon precipitated as CaCO in gypsum-treated litter than in untreated litter ( litter with gypsum favors the precipitation of CaCO, which buffers against increases in litter pH that are known to facilitate NH volatilization. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Geographic distribution of soluble salts, exchangeable sodium and calcium carbonate in the Caribbean Region of Colombia

International Nuclear Information System (INIS)

Pulido, Carlos E

2000-01-01

A research was carried out to establish the distribution of soluble salts, exchangeable sodium and calcium carbonate in the soils of the Caribbean Region. The results show that 28,3% (3.506.033 ha) of the soils have problems related to salinity. The soils of the arid and semiarid zones and those belonging to the sea plain are affected severely by soluble salts, exchangeable sodium and calcium carbonate

Kinetic study of the reaction of uranium with various carbon-containing gases; Etude cinetique de la reaction sur l'uranium de differents gaz carbones

Energy Technology Data Exchange (ETDEWEB)

Feron, G [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1963-09-15

The kinetic study of the reaction U + CO{sub 2} and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C The reaction with carbon monoxide leads to a mixture of dioxide UO{sub 2}, dicarbide UC{sub 2} and free carbon. The main reaction can be written. U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO{sub 2} and UC{sub 2} can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO{sub 2} and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [French] L'etude cinetique des reactions U sol + CO{sub 2} gaz et U sol + CO gaz a ete effectuee par thermogravirnetrie sur une poudre d'uranium a grains spheriques, les domaines de temperature etudies s'etendant respectivement de 460 a 690 deg. C et de 570 a 850 deg. C. L'action du dioxyde de carbone conduit au dioxyde d'uranium UO{sub 2}; il se produit en meme temps un depot de carbone. La reaction globale resulte des deux reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C Le mono-oxyde de carbone conduit a un melange de dioxyde UO{sub 2}, de dicarbure UC{sub 2} et de carbone libre. La reaction principale s'ecrit: U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} Le carbone libre provient de la dismutation du mono-oxyde de carbone. On observe une separation remarquable des deux phases UO{sub 2} et UC{sub 2}; un mecanisme rendant compte de ce phenomene a

Interaction of indium trichloride with calcium carbonate in aqueous solutions

International Nuclear Information System (INIS)

Kochetkova, N.V.; Toptygina, G.M.; Soklakova, O.V.; Evdokimov, V.I.

1991-01-01

Interaction of indium trichloride with calcium carbonate in aqueous solutions was studied, using methods of potentiometry, isothermal solubility and physicochemical computer simulating. The Gibb's energy value for crystal indium trihydroxide formation was calculated on the basis of experimental data on In(OH) 3 solubility. The value obtained was used for estimating equilibrium composition of InCl 3 -HCl-CaCO 3 -CO 2 -H 2 O system at a temperature of 25 deg C and carbon dioxide partial pressure of 0.05 to 1 at

Why to synthesize vaterite polymorph of calcium carbonate on the cellulose matrix via sonochemistry process?

Science.gov (United States)

Fu, Lian-Hua; Dong, Yan-Yan; Ma, Ming-Guo; Yue, Wen; Sun, Shao-Long; Sun, Run-Cang

2013-09-01

Vaterite is an important biomedical material due to its features such as high specific surface area, high solubility, high dispersion, and small specific gravity. The purposes of this article were to explore the growth mechanism of vaterite on the cellulose matrix via sonochmistry process. In the work reported herein, the influences of experimental parameters on the polymorph of calcium carbonate were investigated in detail. The calcium carbonate crystals on the cellulose matrix were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Experimental results revealed that all the reactants, solvent, and synthesis method played an important role in the polymorph of calcium carbonate. The pure phase of vaterite polymorph was obtained using Na2CO3 as reactant in ethylene glycol on the cellulose matrix via sonochmistry process. Based on the experimental results, one can conclude that the synthesis of vaterite polymorph is a system process. Copyright © 2013 Elsevier B.V. All rights reserved.

Vibrationally Excited Carbon Monoxide Produced via a Chemical Reaction Between Carbon Vapor and Oxygen

Science.gov (United States)

Jans, Elijah R.; Eckert, Zakari; Frederickson, Kraig; Rich, Bill; Adamovich, Igor V.

2017-06-01

Measurements of the vibrational distribution function of carbon monoxide produced via a reaction between carbon vapor and molecular oxygen has shown a total population inversion on vibrational levels 4-7. Carbon vapor, produced using an arc discharge to sublimate graphite, is mixed with an argon oxygen flow. The excited carbon monoxide is vibrationally populated up to level v=14, at low temperatures, T=400-450 K, in a collision-dominated environment, 15-20 Torr, with total population inversions between v=4-7. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of the reaction enthalpy. Kinetic modeling of the flow reactor, including state specific vibrational processes, was performed to infer the vibrational distribution of the products of the reaction. The results show viability of developing of a new chemical CO laser from the reaction of carbon vapor and oxygen.

Preparation of poly (methyl methacrylate)/nanometer calcium carbonate composite by in-situ emulsion polymerization

Institute of Scientific and Technical Information of China (English)

史建明; 包永忠; 黄志明; 翁志学

2004-01-01

Methyl methacrylate (MMA) emulsion polymerization in the presence of nanometer calcium carbonate (nano-CaCO3) surface modified with (-methacryloxypropyltrimethoxysilane (MPTMS) was carried out to prepare poly (methyl methacrylate) (PMMA)/nano-CaCO3 composite. The reaction between nano-CaCO3 and MPTMS, and the grafting of PMMA onto nano-CaCO3 were confirmed by infrared spectrum. The grafting ratio and grafting efficiency of PMMA on nano-CaCO3 modified with MPTMS were much higher than that on nano-CaCO3 modified with stearic acid. The grafting ratio of PMMA increased as the weight ratio between MMA and nano-CaCO3 increased, while the grafting efficiency of PMMA decreased. Transmission electron micrograph showed that nano-CaCO3 covered with PMMA was formed by in-situ emulsion polymerization.

Recovery of sludge from the treatment of liquid radioactive effluents by co-precipitation with calcium carbonate: laboratory study; Recuperation des boues de traitement des effluents radioactifs liquides par coprecipitation avec le carbonate de calcium: etude de laboratoire

Energy Technology Data Exchange (ETDEWEB)

Patti, F.; Gailledreau, C.; Cohen, P.

1961-02-24

As during the treatment by co-precipitation with calcium carbonate of liquid radioactive residues, a partial decontamination can be obtained by simply agitating an already formed radioactive sludge with the effluent to be processed, the authors study whether it would be possible to first perform a co-precipitation with a lower dose of calcium carbonate and then to complete decontamination by agitating with an adequate quantity of sludge stored during preceding operations. The authors report the study of the influence of reactant quantity on the chemical treatment efficiency, of the evolution of the activity of a radioactive residual solution in contact with a precipitate, of the cleaner element, of a precipitate reuse, of the technological and economic aspects, and of another possibility of reduction of the precipitate volume [French] Dans le traitement par coprecipitation avec le carbonate de calcium des residus radioactifs liquides, une decontamination partielle peut etre obtenue en agitant simplement une boue radioactive deja formee avec l'effluent a traiter. En consequence, il pourrait etre possible d'effectuer d'abord une coprecipitation avec une dose plus faible de carbonate de calcium et de completer ensuite la decontamination en agitant le liquide avec une quantite convenable de boue stockee a partir d'operations precedentes. (auteurs)

Reaction mechanisms for enhancing carbon dioxide mineral sequestration

Science.gov (United States)

Jarvis, Karalee Ann

Increasing global temperature resulting from the increased release of carbon dioxide into the atmosphere is one of the greatest problems facing society. Nevertheless, coal plants remain the largest source of electrical energy and carbon dioxide gas. For this reason, researchers are searching for methods to reduce carbon dioxide emissions into the atmosphere from the combustion of coal. Mineral sequestration of carbon dioxide reacted in electrolyte solutions at 185°C and 2200 psi with olivine (magnesium silicate) has been shown to produce environmentally benign carbonates. However, to make this method feasible for industrial applications, the reaction rate needs to be increased. Two methods were employed to increase the rate of mineral sequestration: reactant composition and concentration were altered independently in various runs. The products were analyzed with complete combustion for total carbon content. Crystalline phases in the product were analyzed with Debye-Scherrer X-ray powder diffraction. To understand the reaction mechanism, single crystals of San Carlos Olivine were reacted in two solutions: (0.64 M NaHCO3/1 M NaCl) and (5.5 M KHCO3) and analyzed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and fluctuation electron microscopy (FEM) to study the surface morphology, atomic crystalline structure, composition and amorphous structure. From solution chemistry studies, it was found that increasing the activity of the bicarbonate ion increased the conversion rate of carbon dioxide to magnesite. The fastest conversion, 60% conversion in one hour, occurred in a solution of 5.5 M KHCO3. The reaction product particles, magnesium carbonate, significantly increased in both number density and size on the coupon when the bicarbonate ion activity was increased. During some experiments reaction vessel corrosion also altered the mineral sequestration mechanism. Nickel ions from vessel

Calcium absorbability from milk products, an imitation milk, and calcium carbonate

International Nuclear Information System (INIS)

Recker, R.R.; Bammi, A.; Barger-Lux, M.J.; Heaney, R.P.

1988-01-01

Whole milk, chocolate milk, yogurt, imitation milk (prepared from dairy and nondairy products), cheese, and calcium carbonate were labeled with 45 Ca and administered as a series of test meals to 10 healthy postmenopausal women. Carrier Ca content of the test meals was held constant at 250 mg and subjects fasted before each meal. The absorbability of Ca from the six sources was compared by measuring fractional absorption by the double isotope method. The mean absorption values for all six sources were tightly clustered between 21 and 26% and none was significantly different from the others using one-way analysis of variance. We conclude that none of the sources was significantly superior or inferior to the others

Study of the effect of magnesium concentration on the deposit of allotropic forms of calcium carbonate and related carbon steel interface behavior

International Nuclear Information System (INIS)

Ben Amor, Y.; Bousselmi, L.; Tribollet, B.; Triki, E.

2010-01-01

Different allotropic forms of calcium carbonate scales were electrochemically deposited on a carbon steel surface in artificial underground Tunisian water at -0.95 V SCE and various Mg 2+ concentrations. Because of the importance of the diffusion process, the rotating disk electrode was used. The deposition kinetics were analyzed by chronoamperometry measurements and the calcareous layers were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The physical model proposed by Gabrielli was used to analyze the EIS measurements. Independent of the deposited allotropic form of calcium carbonate, the measurements showed that the oxygen reduction occurs in the pores formed between the CaCO 3 crystals and the metallic surface.

Uptake of radiactive calcium by groundnut (Arachis hypogaea L. ) and efficiency of utilisation of applied calcium

Energy Technology Data Exchange (ETDEWEB)

Loganathan, S; Krishnamoorthy, K K [Tamil Nadu Agricultural Univ., Coimbatore (India). Dept. of Soil Science and Agricultural Chemistry

1977-04-01

A pot experiment was conducted with groundnut applying labelled calcium as its sulphate and carbonate at two levels namely 75 and 150 kg Ca per ha with varying levels of P, K and Mg. Plant samples were taken at different stages of crop growth and analysed for the content of radioactive calcium. Calcium sulphate treatment has resulted in larger uptake of calcium compared to calcium carbonate. An application of 150 kg Ca per ha has caused significantly higher uptake by groundnut plant than 75 kg Ca per ha. The percentage of utilisation of added calcium ranged from 2.2 to 5.4 Recovery of calcium by plants was more in calcium sulphate treatment rather than in calcium carbonate. The plants showed a preference for absorbing applied calcium rather than native calcium.

Uptake of radiactive calcium by groundnut (Arachis hypogaea L.) and efficiency of utilisation of applied calcium

International Nuclear Information System (INIS)

Loganathan, S.; Krishnamoorthy, K.K.

1977-01-01

A pot experiment was conducted with groundnut applying labelled calcium as its sulphate and carbonate at two levels namely 75 and 150 kg Ca per ha with varying levels of P, K and Mg. Plant samples were taken at different stages of crop growth and analysed for the content of radioactive calcium. Calcium sulphate treatment has resulted in larger uptake of calcium compared to calcium carbonate. An application of 150 kg Ca per ha has caused significantly higher uptake by groundnut plant than 75 kg Ca per ha. The percentage of utilisation of added calcium ranged from 2.2 to 5.4 Recovery of calcium by plants was more in calcium sulphate treatment rather than in calcium carbonate. The plants showed a preference for absorbing applied calcium rather than native calcium

Early Age Carbonation Heat and Products of Tricalcium Silicate Paste Subject to Carbon Dioxide Curing

Directory of Open Access Journals (Sweden)

Zhen Li

2018-05-01

Full Text Available This paper presents a study on the carbonation reaction heat and products of tricalcium silicate (C3S paste exposed to carbon dioxide (CO2 for rapid curing. Reaction heat was measured using a retrofitted micro-calorimeter. The highest heat flow of a C3S paste subject to carbonation curing was 200 times higher than that by hydration, and the cumulative heat released by carbonation was three times higher. The compressive strength of a C3S paste carbonated for 2 h and 24 h was 27.5 MPa and 62.9 MPa, respectively. The 24-h carbonation strength had exceeded the hydration strength at 28 days. The CO2 uptake of a C3S paste carbonated for 2 h and 24 h was 17% and 26%, respectively. The X-ray diffraction (XRD, transmission electron microscope coupled with energy dispersive spectrometer (TEM-EDS, and 29Si magic angle spinning–nuclear magnetic resonance (29Si MAS-NMR results showed that the products of a carbonated C3S paste were amorphous silica (SiO2 and calcite crystal. There was no trace of calcium silicate hydrate (C–S–H or other polymorphs of calcium carbonate (CaCO3 detected.

Reactions of sulphur mustard on impregnated carbons.

Science.gov (United States)

Prasad, G K; Singh, Beer

2004-12-31

Activated carbon of surface area 1100 m2/gm is impregnated with 4% sodium hydroxide plus 3% Cr(VI) as CrO3 with and without 5% ethylene diamine (EDA), 4% magnesium nitrate and 5% ruthenium chloride by using their aqueous solutions. These carbons are characterized for surface area analysis by BET conventional method and exposed to the vapours of sulphur mustard (HD) at room temperature (30 degrees C). After 24 h, the reaction products are extracted in dichloromethane and analyzed using gas chromatography and mass spectrometry (GC-MS). Hemisulphur mustard, thiodiglycol, 1,4-oxathiane are observed to be the products of reaction between sulphur mustard and NaOH/CrO3/C system, whereas on NaOH/CrO3/EDA/C system HD reacted to give 1,4-thiazane. On Mg(NO3)2/C system it gave hemisulphur mustard and thiodiglycol. On RuCl3/C system it degraded to divinyl sulphone. Residual sulphur mustard is observed along with reaction products in all systems studied. Reaction mechanisms are also proposed for these interesting surface reactions. Above-mentioned carbons can be used in filtration systems for protection against hazardous gases such as sulphur mustard.

Reactions of sulphur mustard on impregnated carbons

International Nuclear Information System (INIS)

Prasad, G.K.; Singh, Beer

2004-01-01

Activated carbon of surface area 1100 m 2 /gm is impregnated with 4% sodium hydroxide plus 3% Cr(Vi) as CrO 3 with and without 5% ethylene diamine (EDA), 4% magnesium nitrate and 5% ruthenium chloride by using their aqueous solutions. These carbons are characterized for surface area analysis by BET conventional method and exposed to the vapours of sulphur mustard (HD) at room temperature (30 deg. C). After 24 h, the reaction products are extracted in dichloromethane and analyzed using gas chromatography and mass spectrometry (GC-MS). Hemisulphur mustard, thiodiglycol, 1,4-oxathiane are observed to be the products of reaction between sulphur mustard and NaOH/CrO 3 /C system, whereas on NaOH/CrO 3 /EDA/C system HD reacted to give 1,4-thiazane. On Mg(NO 3 ) 2 /C system it gave hemisulphur mustard and thiodiglycol. On RuCl 3 /C system it degraded to divinyl sulphone. Residual sulphur mustard is observed along with reaction products in all systems studied. Reaction mechanisms are also proposed for these interesting surface reactions. Above-mentioned carbons can be used in filtration systems for protection against hazardous gases such as sulphur mustard

Calcifying Cyanobacteria - The potential of biomineralization for Carbon Capture and Storage

Energy Technology Data Exchange (ETDEWEB)

Jansson, Christer G; Northen, Trent

2010-03-26

Employment of cyanobacteria in biomineralization of carbon dioxide by calcium carbonate precipitation offers novel and self-sustaining strategies for point-source carbon capture and sequestration. Although details of this process remain to be elucidated, a carbon-concentrating mechanism, and chemical reactions in exopolysaccharide or proteinaceous surface layers are assumed to be of crucial importance. Cyanobacteria can utilize solar energy through photosynthesis to convert carbon dioxide to recalcitrant calcium carbonate. Calcium can be derived from sources such as gypsum or industrial brine. A better understanding of the biochemical and genetic mechanisms that carry out and regulate cynaobacterial biomineralization should put us in a position where we can further optimize these steps by exploiting the powerful techniques of genetic engineering, directed evolution, and biomimetics.

In vitro study of the effect of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate on acid-softened enamel.

Science.gov (United States)

Rege, Aarti; Heu, Rod; Stranick, Michael; Sullivan, Richard J

2014-01-01

To investigate the possible mode of action of a dentifrice containing 8% arginine and calcium carbonate (Pro-Argin Technology), and sodium monofluorophosphate in delivering the benefits of preventing acid erosion and rehardening acid-softened enamel. The surfaces of acid-softened bovine enamel specimens were evaluated after application of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate in vitro. Scanning Electron Microscopy (SEM), Electronic Spectrometry for Chemical Analysis (ESCA), and Secondary Ion Mass Spectrometry (SIMS) were used to characterize the enamel surfaces. Exposure of pristine enamel surfaces to citric acid resulted in clear roughening of the surface. Multiple applications of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate to the surface of the enamel resulted in the disappearance of the microscopic voids observed by SEM as a function of treatment applications. The ESCA analysis demonstrated that both the nitrogen and carbonate levels increased as the number of treatments increased, which provides evidence that arginine and calcium carbonate were bound to the surface. Observance of arginine's signature mass fragmentation pattern by SIMS analysis confirmed the identity of arginine on the enamel surface. A series of in vitro experiments has demonstrated a possible mode of action by which a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate delivers the benefits of preventing acid erosion and rehardening acid-softened enamel. The combination of arginine and calcium carbonate adheres to the enamel surface and helps to fill the microscopic gaps created by acid, which in turn helps repair the enamel and provides a protective coating against future acid attacks.

Calcification mechanism and bony bonding studies of calcium carbonate and composite aluminosilicate/calcium phosphate applied as biomaterials by using radioactivation methods

International Nuclear Information System (INIS)

Oudadesse, H.; Derrien, A.C.; Lucas-Girot, A.; Martin, S.; Cathelieau, G.

2007-01-01

Bony grafts are used as a filling biomaterial for defective bone. The introduction of new range of synthetic materials offers to surgeons additional possibilities to avoid virus transmission risks by using natural grafts in bony surgery. In this work, two materials, synthetic calcium carbonate and composite aluminosilicate/calcium phosphate were synthesized by an original method and experimented 'in vivo' as biomaterials for bony filling. Extracted biopsies were studied by several physico chemical and biological methods. The aim was to evaluate the kinetic resorption and bioconsolidation of these materials. We focused on the bioconsolidation between implant and bone by realising cartographies from the implant to the bone and on the calcification mechanism by determination of the origin of Ca and Sr responsible of the neo-formed bone. Neutron activation analysis (NAA), radiotracers 45 Ca* and 85 Sr* and proton-induced X-ray emission (PIXE) were used. Concerning the synthetic calcium carbonate, results show that twelve months after implantation, the mineral composition of implant becomes similar to that of the mature bone. The neoformed bone is composed with Ca and Sr coming from the organism when the Ca and Sr of the implant were progressively eliminated. Concerning the composite geopolymer/calcium phosphate, PIXE and histological studies reveal the intimate links between the bone and the implant starting with the first month after implantation. (author)

Bioprecipitation of Calcium Carbonate Crystals by Bacteria Isolated from Saline Environments Grown in Culture Media Amended with Seawater and Real Brine

Directory of Open Access Journals (Sweden)

G. A. Silva-Castro

2015-01-01

Full Text Available The precipitation of calcium carbonate and calcium sulphate by isolated bacteria from seawater and real brine obtained in a desalination plant growth in culture media containing seawater and brine as mineral sources has been studied. However, only bioprecipitation was detected when the bacteria were grown in media with added organic matter. Biomineralization process started rapidly, crystal formation taking place in the beginning a few days after inoculation of media; roughly 90% of total cultivated bacteria showed. Six major colonies with carbonate precipitation capacity dominated bacterial community structure cultivated in heterotrophic platable bacteria medium. Taxonomic identification of these six strains through partial 16S rRNA gene sequences showed their affiliation with Gram-positive Bacillus and Virgibacillus genera. These strains were able to form calcium carbonate minerals, which precipitated as calcite and aragonite crystals and showed bacterial fingerprints or bacteria calcification. Also, carbonic anhydrase activity was observed in three of these isolated bacteria. The results of this research suggest that microbiota isolated from sea water and brine is capable of precipitation of carbonate biominerals, which can occur in situ with mediation of organic matter concentrations. Moreover, calcium carbonate precipitation ability of this microbiota could be of importance in bioremediation of CO2 and calcium in certain environments.

A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean

OpenAIRE

Battaglia Gianna; Steinacher Marco; Joos Fortunat

2016-01-01

The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 export fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Monte Carlo sche...

Chemical looping coal gasification with calcium ferrite and barium ferrite via solid–solid reactions

International Nuclear Information System (INIS)

Siriwardane, Ranjani; Riley, Jarrett; Tian, Hanjing; Richards, George

2016-01-01

Highlights: • BaFe 2 O 4 and CaFe 2 O 4 are excellent for chemical looping coal gasification. • BaFe 2 O 4 and CaFe 2 O 4 have minimal reactivity with synthesis gas. • Steam enhances the gasification process with these oxygen carriers. • Reaction rates of steam gasification of coal with CaFe 2 O 4 was better than with gaseous oxygen. • Coal gasification appears to be via solid–solid interaction with the oxygen carrier. - Abstract: Coal gasification to produce synthesis gas by chemical looping was investigated with two oxygen carriers, barium ferrite (BaFe 2 O 4 ) and calcium ferrite (CaFe 2 O 4 ). Thermo-gravimetric analysis (TGA) and fixed-bed flow reactor data indicated that a solid–solid interaction occurred between oxygen carriers and coal to produce synthesis gas. Both thermodynamic analysis and experimental data indicated that BaFe 2 O 4 and CaFe 2 O 4 have high reactivity with coal but have a low reactivity with synthesis gas, which makes them very attractive for the coal gasification process. Adding steam increased the production of hydrogen (H 2 ) and carbon monoxide (CO), but carbon dioxide (CO 2 ) remained low because these oxygen carriers have minimal reactivity with H 2 and CO. Therefore, the combined steam–oxygen carrier produced the highest quantity of synthesis gas. It appeared that neither the water–gas shift reaction nor the water splitting reaction promoted additional H 2 formation with the oxygen carriers when steam was present. Wyodak coal, which is a sub-bituminous coal, had the best gasification yield with oxygen carrier–steam while Illinois #6 coal had the lowest. The rate of gasification and selectivity for synthesis gas production was significantly higher when these oxygen carriers were present during steam gasification of coal. The rates and synthesis gas yields during the temperature ramps of coal–steam with oxygen carriers were better than with gaseous oxygen.

Separation and determination of radiostrontium in calcium carbonate matrices of biological origin

International Nuclear Information System (INIS)

Clark, S.B.

1994-01-01

Radiostrontium is concentrated in the shells of mollusks and other animals due to the isomorphic substitution of strontium for calcium in the calcium carbonate shell matrix. Radiochemical separation of strontium from such matrices is difficult because of the chemical similarity between strontium and calcium. This paper describes a technique using a commercially-available, solid-phase extractant to separate Sr-89 and Sr-90 from high concentrations of Ca 2+ . The extractant removes Sr(NO 3 ) 2 from acidic nitrate media, and strontium activities are determined via conventional β-counting techniques. This method has been used to process mollusk shells collected from contaminated reactor cooling ponds at the Savannah River Site and Chernobyl Nuclear Power Plant. (author). 13 refs., 2 figs., 2 tabs

Precipitation of Calcium Carbonate in the Presence of Urea at 293 K and 343 K

Directory of Open Access Journals (Sweden)

Białowicz Katarzyna

2014-06-01

Full Text Available The results of the precipitation of calcium carbonate from a waste post-distillation liquid (DS and a sodium bicarbonate saturated solution – both from the Solvay method – in the presence of urea are presented. The investigation was carried out at 293 K and 343 K. Reagent dosage times of 1, 5, 10, 20 and 30 min, and urea concentrations of 5, 6 and 10 mol/dm3 were applied. The granulometric composition, the values of bulk and packing densities and the absorptiveness sorption of water and paraffin oil from the obtained calcium carbonate were investigated.

Recovery of calcium carbonate from steelmaking slag and utilization for acid mine drainage pre-treatment

CSIR Research Space (South Africa)

Mulopo, J

2012-06-01

Full Text Available The conversion of steelmaking slag (a waste product of the steelmaking process) to calcium carbonate (CaCO3) was tested using hydrochloric acid, ammonium hydroxide and carbon dioxide via a pH-swing process. Batch reactors were used to assess...

Protein mapping of calcium carbonate biominerals by immunogold.

Science.gov (United States)

Marin, Frédéric; Pokroy, Boaz; Luquet, Gilles; Layrolle, Pierre; De Groot, Klaas

2007-05-01

The construction of metazoan calcium carbonate skeletons is finely regulated by a proteinaceous extracellular matrix, which remains embedded within the exoskeleton. In spite of numerous biochemical studies, the precise localization of skeletal proteins has remained for a long time as an elusive goal. In this paper, we describe a technique for visualizing shell matrix proteins on the surface of calcium carbonate crystals or within the biominerals. The technique is as follows: freshly broken pieces of biominerals or NaOCl then EDTA-etched polished surfaces are incubated with an antibody elicited against one matrix protein, then with a secondary gold-coupled antibody. After silver enhancement, the samples are subsequently observed with scanning electron microscopy by using back-scattered electron mode. In the present case, the technique is applied to a particular example, the calcitic prisms that compose the outer shell layer of the mediterranean fan mussel Pinna nobilis. One major soluble protein, caspartin, which was identified recently, was partly de novo sequenced after enzymatic digestions. A polyclonal antibody raised against caspartin was used for its localization within and on the prisms. The immunogold localization indicated that caspartin surrounds the calcitic prisms, but is also dispersed within the biominerals. This example illustrates the deep impact of the technique on the definition of intracrystalline versus intercrystalline matrix proteins. Furthermore, it is an important tool for assigning a putative function to a matrix protein of interest.

Recovery of calcium from the effluent of direct oxide reduction process

International Nuclear Information System (INIS)

Ferro, P.; Mishra, B.; Olson, D.L.; Moore, J.J.; Averill, W.A.

1992-01-01

This paper reports that the production of plutonium by Direct Oxide Reduction [DOR] process using calcium generates significant amount of contaminated waste as calcium oxide saturated calcium chloride salt mix with calcium oxide content of up to 15 wt. pct. Fused salt electrolysis of a simulated slat mix [CaCl 2 + 15 wt. pct. CaO] is being carried out to election calcium, which can be recycled to the DOR rector along with the calcium chloride salt or may be used in-situ in an combined DOR and electrowinning process. The technology will resolve a major contaminated waste disposal problem, besides improving the cost and process efficiency in radioactive metal production. The process is being optimized in terms of the calcium solubility, cell temperature, current density and cell design to maximize the current efficiency. Scattered information is available regarding the solubility of calcium in calcium chloride salt in the present of calcium oxide. The solubility has also been found to depend on the use of graphite as the anode material. A porous ceramic sheath is being used around the anode to prevent the dissolution of electrowon calcium as oxide or carbonate and to prevent the contamination of salt by the anodic carbon. The electrode reactions are affected by the electrolyte composition and its viscosity which varies with time in this process and, therefore, electrochemical impedance is being measured to understand this time-dependent mechanisms

Calcium carbonate solubility: a reappraisal of scale formation and inhibition.

Science.gov (United States)

Gal, J Y; Bollinger, J C; Tolosa, H; Gache, N

1996-09-01

Considerable disparity exists in the published thermodynamic data for selected species in the Ca(2+) /CO(2)/H(2)O system near 25 degrees C and 1 atm pressure. Some authors doubt the significance of CaCO(3)(0)aq) complexes although there is experimental evidence of their occurrence. Evaluation of all the published experimental and estimated data for aqueous calcium carbonate species confirms that the consistent set of constants given by Plummer and Busenberg in 1982 is the best available, and suggests a formation constant log beta = 3.22 for CaCO(3)(0)(aq). This value was confirmed by additional experimental data and calculations using a specially developed computer program. The solubility s and solubility product K(s) are critically evaluated for each solid polymorph (amorphous CaCO(3), ikaite, vaterite, aragonite and calcite) using a hydrated ion pair model and we give coherent explanations for the calcium carbonate precipitation/dissolution process and the existence of supersaturated waters. The practical cases of scale formation and its inhibition by phosphonate-type compounds are discussed and explained with the same model, taking into account the CaCO(3)(0)(aq) species.

Mineral CO2 sequestration by steel slag carbonation

International Nuclear Information System (INIS)

Huijgen, W.J.J.; Comans, R.N.J.; Witkamp, G.J.

2005-12-01

Mineral CO2 sequestration, i.e., carbonation of alkaline silicate Ca/Mg minerals, analogous to natural weathering processes, is a possible technology for the reduction of carbon dioxide emissions to the atmosphere. In this paper, alkaline Ca-rich industrial residues are presented as a possible feedstock for mineral CO2 sequestration. These materials are cheap, available near large point sources of CO2, and tend to react relatively rapidly with CO2 due to their chemical instability. Ground steel slag was carbonated in aqueous suspensions to study its reaction mechanisms. Process variables, such as particle size, temperature, carbon dioxide pressure, and reaction time, were systematically varied, and their influence on the carbonation rate was investigated. The maximum carbonation degree reached was 74% of the Ca content in 30 min at 19 bar pressure, 100C, and a particle size of <38 μm. The two must important factors determining the reaction rare are particle size (<2 mm to <38 μm) and reaction temperature (25-225C). The carbonation reaction was found to occur in two steps: (1) leaching of calcium from the steel slag particles into the solution; (2) precipitation of calcite on the surface of these particles. The first step and, more in particular, the diffusion of calcium through the solid matrix toward the surface appeared to be the rate-determining reaction step, The Ca diffusion was found to be hindered by the formation of a CaCO3-coating and a Ca-depleted silicate zona during the carbonation process. Research on further enhancement of the reaction rate, which would contribute to the development of a cost-effective CO2-sequestration process, should focus particularly on this mechanism

Acute intraoperative reactions during the injection of calcium sulfate bone cement for the treatment of unicameral bone cysts: a review of four cases.

Science.gov (United States)

Nystrom, Lukas; Raw, Robert; Buckwalter, Joseph; Morcuende, Jose A

2008-01-01

Unicameral bone cysts can predispose patients to pathologic fracture and deformities of growth. Treatment options vary from continuous decompression with transcortical placement of a cannulated screw to percutaneous aspiration and injection of medical-grade calcium sulfate. From 2005 to 2007, we treated 22 patients with unicameral bone cysts using aspiration and injection of calcium sulfate. Three patients experienced acute laryngospasm and one patient developed tachyarrhythmia, temporarily, associated with injection of calcium sulfate. All reactions occurred in patients under age 18 without predisposing risk factors and resolved spontaneously with supportive care. Although the mechanism is unclear, we hypothesize that these reactions are either due to the nociceptive stimulus of the calcium sulfate injection or a systemic calcium bolus. Clinicians using this product for this indication should be aware that such reactions may occur. We suggest endotracheal intubation and communication to the anesthesiologist about the time of the injection in preparation for these idiopathic responses. Further research is necessary to determine exactly how this reaction occurs and how it can be avoided.

Comparing the applicability of some geostatistical methods to predict the spatial distribution of topsoil Calcium Carbonate in part of farmland of Zanjan Province

Science.gov (United States)

Sarmadian, Fereydoon; Keshavarzi, Ali

2010-05-01

Most of soils in iran, were located in the arid and semi-arid regions and have high pH (more than 7) and high amount of calcium carbonate and this problem cause to their calcification.In calcareous soils, plant growing and production is difficult. Most part of this problem, in relation to high pH and high concentration of calcium ion that cause to fixation and unavailability of elements which were dependent to pH, especially Phosphorous and some micro nutrients such as Fe, Zn, Mn and Cu. Prediction of soil calcium carbonate in non-sampled areas and mapping the calcium carbonate variability in order to sustainable management of soil fertility is very important.So, this research was done with the aim of evaluation and analyzing spatial variability of topsoil calcium carbonate as an aspect of soil fertility and plant nutrition, comparing geostatistical methods such as kriging and co-kriging and mapping topsoil calcium carbonate. For geostatistical analyzing, sampling was done with stratified random method and soil samples from 0 to 15 cm depth were collected with auger within 23 locations.In co-kriging method, salinity data was used as auxiliary variable. For comparing and evaluation of geostatistical methods, cross validation were used by statistical parameters of RMSE. The results showed that co-kriging method has the highest correlation coefficient and less RMSE and has the higher accuracy than kriging method to prediction of calcium carbonate content in non-sampled areas.

Constraining the cause of the end-Guadalupian extinction with coupled records of carbon and calcium isotopes

Science.gov (United States)

Jost, A. B.; Mundil, R.; He, B.; Brown, S. T.; Altiner, D.; Sun, Y.; DePaolo, D. J.; Payne, J.

2013-12-01

A negative δ13C excursion in carbonate sediments from Guadalupian (Middle Permian) and Lopingian (Late Permian) stratigraphic sections has been interpreted to result from a large carbon cycle disturbance during end-Guadalupian extinction event (ca. 260 Ma). However, the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbations to the global carbon cycle. The carbon and calcium cycles are coupled via CaCO3 burial, so changes in calcium isotopes can be used to constrain the cause of a carbon isotope excursion. In this study, we present coupled carbon and calcium isotope records from three Guadalupian-Lopingian (G/L) sections in China and Turkey. Isotope records among our studied sections are inconsistent in both their δ13C and δ44/40Ca records. Similar inconsistencies in δ13C among sections occur across previously published datasets. Sections with large (>3‰) changes in δ13C either show evidence for diagenetic alteration or do not show δ13C and δ44/40Ca changes consistent with severe volcanic degassing from Emeishan or methane clathrate destabilization. We conclude that the large isotopic changes are more likely the result of local burial conditions or diagenetic effects, rather than a large carbon cycle disturbance. Perturbations to the global carbon and calcium cycles appear to have been much smaller across the G/L transition than across the subsequent Permian-Triassic boundary. This finding is consistent with recent paleobiological data showing that the end-Guadalupian extinction was much less severe than previously believed, and was indistinguishable in magnitude from background intervals. However, selective extinction of marine animals with passive respiratory physiology indicates that the G/L extinction cannot simply be due to background extinction or sampling failure, and that it was triggered by some environmental event. Therefore, any environmental event must have been small enough to not generate large

Effects of dietary bread crust Maillard reaction products on calcium and bone metabolism in rats.

Science.gov (United States)

Roncero-Ramos, Irene; Delgado-Andrade, Cristina; Haro, Ana; Ruiz-Roca, Beatriz; Morales, Francisco J; Navarro, María Pilar

2013-06-01

Maillard reaction products (MRP) consumption has been related with the development of bone degenerative disorders, probably linked to changes in calcium metabolism. We aimed to investigate the effects of MRP intake from bread crust on calcium balance and its distribution, and bone metabolism. During 88 days, rats were fed control diet or diets containing bread crust as source of MRP, or its soluble high molecular weight, soluble low molecular weight or insoluble fractions (bread crust, HMW, LMW and insoluble diets, respectively). In the final week, a calcium balance was performed, then animals were sacrified and some organs removed to analyse calcium levels. A second balance was carried out throughout the experimental period to calculate global calcium retention. Biochemical parameters and bone metabolism markers were measured in serum or urine. Global calcium bioavailability was unmodified by consumption of bread crust or its isolate fractions, corroborating the previously described low affinity of MRP to bind calcium. Despite this, a higher calcium concentration was found in femur due to smaller bones having a lower relative density. The isolate consumption of the fractions altered some bone markers, reflecting a situation of increased bone resorption or higher turnover; this did not take place in the animals fed the bread crust diet. Thus, the bread crust intake does not affect negatively calcium bioavailability and bone metabolism.

Growth rate and calcium carbonate accumulation of Halimeda macrolobaDecaisne (Chlorophyta: Halimedaceae in Thai waters

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Jaruwan Mayakun

2014-08-01

Full Text Available Halimeda macroloba Decaisne can utilize the CO2 used for carbon fixation in photosynthesis and use bicarbonate as the main carbon source for calcification. Although Halimeda has been recognized as a carbon sink species, the calcium accumulation of Halimeda species in Thai waters remain poorly understood. In this study, the highest density of H. macroloba was 26 thalli/m2 and Halimeda quickly produced 1-2 new segments/thallus/day or 20.1 mg dry weight/thallus/day. Its calcium carbonate accumulation rate was 16.6 mg CaCO3 /thallus/day, or 82.46 % per thallus. In Thailand, however, only three scientific papers of growth rate and CaCO3 accumulation rate of H. macroloba have been found and collected. Of these records, the mean density was 26-104 thalli/m2 . The growth rate of H. macroloba was around 1-2 mg dry weight/day and the CaCO3 accumulation rate varied around 41-91%. Thus, Halimeda has a great potential to decrease the carbon dioxide concentration in the ocean.

Weight Percentage of Calcium Carbonate for 17 Equatorial Pacific Cores from Brown University

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Weight percentages of calcium carbonate in this file were compiled by J. Farrell and W. L. Prell of Brown University for 17 equatorial Pacific Ocean sediment cores....

Optical Excitation of Carbon Nanotubes Drives Localized Diazonium Reactions

Science.gov (United States)

2016-01-01

Covalent chemistries have been widely used to modify carbon nanomaterials; however, they typically lack the precision and efficiency required to directly engineer their optical and electronic properties. Here, we show, for the first time, that visible light which is tuned into resonance with carbon nanotubes can be used to drive their functionalization by aryldiazonium salts. The optical excitation accelerates the reaction rate 154-fold (±13) and makes it possible to significantly improve the efficiency of covalent bonding to the sp2 carbon lattice. Control experiments suggest that the reaction is dominated by a localized photothermal effect. This light-driven reaction paves the way for precise nanochemistry that can directly tailor carbon nanomaterials at the optical and electronic levels. PMID:27588432

A strategy of precipitated calcium carbonate (CaCO3) fillers for enhancing the mechanical properties of polypropylene polymers

International Nuclear Information System (INIS)

Thenepalli, Thriveni; Ahn, Ji Whan; Ahn, Young Jun; Han, Choon; Ramakrishna, Chilakala

2015-01-01

A wide variety of fillers are currently used in more than twenty types of polymer resins, although four of them alone (polypropylene, polyamides, thermoplastic polyesters, and polyvinyl chloride) account for 90% of the market of mineral fillers in plastics. Polypropylene (PP) and PVC dominate the market for calcium carbonate. PP is a versatile reinforcement material that can meet engineering and structural specifications and is widely used for automotive components, home appliances, and industrial applications. Talc, mica, clay, kaolin, wollastonite, calcium carbonates, feldspar, aluminum hydroxide, glass fibers, and natural fibers are commonly used in fillers. Among these, calcium carbonate (both natural and synthetic) is the mos abundant and affords the possibility of improved surface finishing, control over the manufacture of products, and increased electric resistance and impact resistance. Meeting the global challenge to reduce the weight of vehicles by using plastics is a significant issue. The current the global plastic and automobile industry cannot survive without fillers, additives, and reinforcements. Polypropylene is a major component of the modern plastic industry, and currently is used in dashboards, wheel covers, and some engine parts in automobiles. This article reports that the use of calcium carbonate fillers with polypropylene is the best choice to enhance the mechanical properties of plastic parts used in automobiles

Effect of one step KOH activation and CaO modified carbon in transesterification reaction

Science.gov (United States)

Yacob, Abd Rahim; Zaki, Muhammad Azam Muhammad

2017-11-01

In this work, one step activation was introduced using potassium hydroxide (KOH) and calcium oxide (CaO) modified palm kernel shells. Various concentration of calcium oxide was used as catalyst while maintaining the same concentration of potassium hydroxide to activate and impregnate the palm kernel shell before calcined at 500°C for 5 hours. All the prepared samples were characterized using Fourier Transform Infrared (FTIR) and Field Emission Scanning Electron Microscope (FESEM). FTIR analysis of raw palm kernel shell showed the presence of various functional groups. However, after activation, most of the functional groups were eliminated. The basic strength of the prepared samples were determined using back titration method. The samples were then used as base heterogeneous catalyst for the transesterification reaction of rice bran oil with methanol. Analysis of the products were performed using Gas Chromatography Flame Ionization Detector (GC-FID) to calculate the percentage conversion of the biodiesel products. This study shows, as the percentage of one step activation potassium and calcium oxide doped carbon increases thus, the basic strength also increases followed by the increase in biodiesel production. Optimization study shows that the optimum biodiesel production was at 8 wt% catalyst loading, 9:1 methanol: oil molar ratio at 65°C and 6 hours which gives a conversion up to 95%.

Carbon dioxide transport in molten calcium carbonate occurs through an oxo-Grotthuss mechanism via a pyrocarbonate anion.

Science.gov (United States)

Corradini, Dario; Coudert, François-Xavier; Vuilleumier, Rodolphe

2016-05-01

The reactivity, speciation and solvation structure of CO2 in carbonate melts are relevant for both the fate of carbon in deep geological formations and for its electroreduction to CO (to be used as fuel) when solvated in a molten carbonate electrolyte. In particular, the high solubility of CO2 in carbonate melts has been tentatively attributed to the formation of the pyrocarbonate anion, C2O5(2-). Here we study, by first-principles molecular dynamics simulations, the behaviour of CO2 in molten calcium carbonate. We find that pyrocarbonate forms spontaneously and the identity of the CO2 molecule is quickly lost through O(2-) exchange. The transport of CO2 in this molten carbonate thus occurs in a fashion similar to the Grotthuss mechanism in water, and is three times faster than molecular diffusion. This shows that Grotthuss-like transport is more general than previously thought.

Influence of calcium carbonate on extraction yield and quality of extra virgin oil from olive (Olea europaea L. cv. Coratina).

Science.gov (United States)

Squeo, G; Silletti, R; Summo, C; Paradiso, V M; Pasqualone, A; Caponio, F

2016-10-15

The aim of the research was to evaluate the effect of calcium carbonate (1%, 2%, and 4% of addition) at two different particle sizes (2.7μm and 5.7μm), added at the beginning of the malaxation phase, on both the extraction yield and the quality of oil obtained from Coratina olives at different ripening index. The results showed that calcium carbonate significantly increased the extraction yield of olive oil, more than affecting chemical indices. In particular, for less ripened olives, 1-2% of larger particle size calcium carbonate addiction determined a significant increase of the extraction effectiveness, ranging from 4.0 to 4.9%, while more ripened olives required higher amounts of coadjuvant (2-4% when using the larger particle size and 4% when using the smaller one), with a significant increase of the extraction yield up to 5%. Moreover, an increase of pungent perception was observed in some cases when adding calcium carbonate to more ripened olives. Copyright © 2016 Elsevier Ltd. All rights reserved.

Substitution reactions of carbon nanotube template

Science.gov (United States)

Li, Chi Pui; Chen, Ying; Gerald, John Fitz

2006-05-01

Substitution reactions between carbon nanotube (CNT) template and SiO with the formation of carbon rich silicon oxide nanowires (SiO-C-NWs) have been investigated using transmission electron microscopy and x-ray energy dispersive spectroscopy. The reaction was carried out by thermal annealing at 1200°C for 1h of a mixture of silicon monoxide (SiO) and iron (II) phthalocyanine, FeC32N8H16 (FePc) powders. Multiwalled CNTs were produced first via pyrolysis of FePc at a lower temperature (1000°C ). SiO vapors reacted with the CNTs at higher temperatures to produce amorphous SiO-C-NWs with a uniform diameter and a length in tens of micrometers. The special bamboolike structure of the CNTs allows the reaction to start from the external surface of the tubes and transform each CNT into a solid nanowire section by section.

Comparison of efficacy of an arginine-calcium carbonate-MFP toothpaste to a calcium carbonate-MFP toothpaste in controlling supragingival calculus formation and gingivitis: a 6-month clinical study.

Science.gov (United States)

Li, Yiming; Lee, Sean; Stephens, Joni; Mateo, Luis R; Zhang, Yun Po; DeVizio, William

2012-02-01

To investigate whether the long-term use (6 months) of an arginine-calcium carbonate-MFP toothpaste would affect calculus formation and/or gingivitis when compared to a calcium carbonate-MFP toothpaste. This was a double-blind clinical study. Eligible adult subjects (120) entered a 2-month pre-test phase of the study. After receiving an evaluation of oral tissue and a dental prophylaxis, the subjects were provided with a regular fluoride toothpaste, a soft-bristled adult toothbrush with instructions to brush their teeth for 1-minute twice daily (morning and evening) for 2 months. The subjects were then examined for baseline calculus using the Volpe-Manhold Calculus Index (VMI) and gingivitis using the Löe-Silness Gingival Index (GI), along with an oral tissue examination. Qualifying subjects were randomized to two treatment groups: (1) Colgate Sensitive Pro-Relief toothpaste containing 8.0% arginine, 1450 ppm MFP and calcium carbonate (Test group), or (2) Colgate Cavity Protection toothpaste containing 1450 ppm MFP and calcium carbonate (Control group). Subjects were stratified by the VMI score and gender. After a dental prophylaxis (VMI=0), the subjects entered a 6-month test phase. Each received the assigned toothpaste and a soft-bristled adult toothbrush for home use with instructions of brushing teeth for 1 minute twice daily (morning and evening). The examinations of VMI, Löe-Silness GI and oral tissues were conducted after 3 and 6 months. Prior to each study visit, subjects refrained from brushing their teeth as well as eating and drinking for 4 hours. 99 subjects complied with the study protocol and completed the 6-month test phase. No within-treatment comparison was performed for the VMI because it was brought down to zero after the prophylaxis at the baseline of the test phase. For the Löe-Silness GI, subjects of the Test group exhibited a significant difference from baseline at the 3- and 6-month examinations. The 3-month Löe-Silness GI of the Control

Preparation of poly （methyl methacrylate）／nanometer calcium carbonate composite by in-situ emulsion polymerization

Institute of Scientific and Technical Information of China (English)

史建明; 包永忠; 黄志明; 翁志学

2004-01-01

Methyl methacrylate (MMA) emulsion polymerization in the presence of nanometer calcium carbonate(nano-CaCO3) surface modified with γ-methacryloxypropyltrimethoxysilane (MPTMS) was carried out to prepare poly (methyl methacrylate) (PMMA)/nano-CaCO3 composite. The reaction between nano-CaCO3 and MPTMS, and the grafting of PMMA onto nano-CaCO3 were confirmed by infrared spectrum. The grafting ratio and grafting efficiency of PMMA on nano-CaCO3 modified with MPTMS were much higher than that on nano-CaCO3 modified with stearic acid. The grafting ratio of PMMA increased as the weight ratio between MMA and nano-CaCO3 increased, while the grafting efficiency of PMMA decreased. Transmission electron micrograph showed that nano-CaCO3 covered with PMMA was formed by in-situ emulsion polymerization.

Waste Treatment of Chrome Residue of Chromium Recovery Process Using Calcium Carbonate

International Nuclear Information System (INIS)

Endro Kismolo; Prayitno; Nurimaniwathy

2002-01-01

The aim of the research was to apply the precipitation technology for the treatment of aqueous wastes of leather tanning industries. The chrome liquid wastes taken was the effluent from the residue of the chromium recovery process using magnesium oxide. The precipitant used was calcium carbonate. The experiments was performed by adjusting the concentration of calcium carbonate from 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm to 400 ppm. The stirring speed was varied from 50 rpm, 75 rpm, 100 rpm, 125 rpm, 150 rpm, 175 rpm to 200 rpm. The time of mixing was varied from 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 175 minutes and 200 minutes. The result from the experiments lead to the best condition obtained were the concentration of precipitant was 300 ppm, flow rates of mixing was 125 rpm and time of mixing was 60 minutes. At this condition the separations efficiency of chrome obtained was 99.985%. (author)

Hierarchical porous carbon derived from Allium cepa for supercapacitors through direct carbonization method with the assist of calcium acetate

KAUST Repository

Xu, Jinhui; Zhang, Wenli; Hou, Dianxun; Huang, Weimin; Lin, Haibo

2017-01-01

In this paper, a direction carbonization method was used to prepare porous carbon from Allium cepa for supercapacitor applications. In this method, calcium acetate was used to assist carbonization process. Scanning electron microscope (SEM) and N2 adsorption/desorption method were used to characterize the morphology, Brunauer-Emmett-Teller (BET) specific surface area and pore size distribution of porous carbon derived from Allium cepa (onion derived porous carbon, OPC). OPC is of hierarchical porous structure with high specific surface area and relatively high specific capacitance. OPC possesses relatively high specific surface area of 533.5 m2/g. What’s more, OPC possesses a specific capacitance of 133.5 F/g at scan rate of 5 mV/s.

Hierarchical porous carbon derived from Allium cepa for supercapacitors through direct carbonization method with the assist of calcium acetate

KAUST Repository

Xu, Jinhui

2017-11-02

In this paper, a direction carbonization method was used to prepare porous carbon from Allium cepa for supercapacitor applications. In this method, calcium acetate was used to assist carbonization process. Scanning electron microscope (SEM) and N2 adsorption/desorption method were used to characterize the morphology, Brunauer-Emmett-Teller (BET) specific surface area and pore size distribution of porous carbon derived from Allium cepa (onion derived porous carbon, OPC). OPC is of hierarchical porous structure with high specific surface area and relatively high specific capacitance. OPC possesses relatively high specific surface area of 533.5 m2/g. What’s more, OPC possesses a specific capacitance of 133.5 F/g at scan rate of 5 mV/s.

Integration approach for developing a high-performance biointerface: Sequential formation of hydroxyapatite and calcium carbonate by an improved alternate soaking process

International Nuclear Information System (INIS)

Watanabe, Junji; Akashi, Mitsuru

2008-01-01

Biointerfaces are crucial for regulating biofunctions. An effective method of producing new biomaterials is surface modification, in particular, the hybrid organic-inorganic approach. In this paper, we propose a method for the sequential formation of hydroxyapatite and calcium carbonate on porous polyester membranes by using an improved alternate soaking process. The resulting hybrid membranes were characterized in terms of their calcium and phosphorus ion contents; further, their structure was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and infrared spectroscopy (IR). As a typical biofunction, protein adsorption by these hybrid membranes was investigated. Sequential hydroxyapatite and calcium carbonate formation on the membranes was successfully achieved, and the total amounts of hydroxyapatite and calcium carbonate formed were precisely regulated by the preparative conditions. The SEM and XRD characterizations were verified by comparing with the IR results. The amount of adsorbed protein correlated well with not only the amount of hydroxyapatite formed but also the combined amounts of hydroxyapatite and calcium carbonate formed. The results indicate that the hybrid membranes can function as high-performance biointerfaces that are capable of loading biomolecules such as proteins

Reaction of phosphorus ylides with carbonyl compounds in supercritical carbon dioxide

International Nuclear Information System (INIS)

Jeong, Kyung Il; Kim, Hak Do; Shim, Jae Jin; Ra, Choon Sup

2004-01-01

The condensation reaction of (benzylene)triphenylphosphoranes with carbonyl compounds in supercritical carbon dioxide was examined. Reactions of (benzylene)phosphoranes (ca. 1 mmol) with several benzaldehydes in a supercritical carbon dioxide (80 .deg. C, 2,000 psi) containing THF entrainer (5%) in a 24 mL reactor proceed smoothly to yield olefination products in fairly good to excellent yields but slower, compared to reactions in a conventional THF solvent. Generally, phosphoranes that are not substituted with a nitro group show more (Z)-selective reactions with aromatic aldehydes under scCO 2 condition than in THF. The reaction of (benzylene)triphenylphosphosphoranes with 4-t-butylcyclohexanone gave the corresponding olefin compounds with a low conversion under both the supercritical carbon dioxide and the organic THF solvent. Our preliminary study showed the Wittig reaction carries out smoothly in supercritical carbon dioxide medium and also a possible tunability of this reaction pathway by adding a entrainer. The results would be useful for devising a novel process for the environmentally friendly Wittig reaction

Evaluation of cellular influences caused by calcium carbonate nanoparticles.

Science.gov (United States)

Horie, Masanori; Nishio, Keiko; Kato, Haruhisa; Endoh, Shigehisa; Fujita, Katsuhide; Nakamura, Ayako; Kinugasa, Shinichi; Hagihara, Yoshihisa; Yoshida, Yasukazu; Iwahashi, Hitoshi

2014-03-05

The cellular effects of calcium carbonate (CaCO₃) nanoparticles were evaluated. Three kinds of CaCO₃ nanoparticles were employed in our examinations. One of the types of CaCO₃ nanoparticles was highly soluble. And solubility of another type of CaCO₃ nanoparticle was lower. A stable CaCO₃ nanoparticle medium dispersion was prepared and applied to human lung carcinoma A549 cells and human keratinocyte HaCaT cells. Then, mitochondrial activity, cell membrane damage, colony formation ability, DNA injury, induction of oxidative stress, and apoptosis were evaluated. Although the influences of CaCO₃ nanoparticles on mitochondrial activity and cell membrane damage were small, "soluble" CaCO₃ nanoparticles exerted some cellular influences. Soluble CaCO₃ nanoparticles also induced a cell morphological change. Colony formation was inhibited by CaCO₃ nanoparticle exposure. In particular, soluble CaCO₃ nanoparticles completely inhibited colony formation. The influence on intracellular the reactive oxygen species (ROS) level was small. Soluble CaCO₃ nanoparticles caused an increase in C/EBP-homologous protein (CHOP) expression and the activation of caspase-3. Moreover, CaCO₃ exposure increased intracellular the Ca²⁺ level and activated calpain. These results suggest that cellular the influences of CaCO₃ nanoparticles are mainly caused by intracellular calcium release and subsequently disrupt the effect of calcium signaling. In conclusion, there is possibility that soluble CaCO₃ nanoparticles induce cellular influences such as a cell morphological change. Cellular influence of CaCO₃ nanoparticles is caused by intracellular calcium release. If inhaled CaCO₃ nanoparticles have the potential to influence cellular events. However, the effect might be not severe because calcium is omnipresent element in cell. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

A review on the kinetics of microbially induced calcium carbonate precipitation by urea hydrolysis

Science.gov (United States)

van Paassen, L. A.

2017-12-01

In this study the kinetics of calcium carbonate precipitation induced by the ureolytic bacteria are reviewed based on experiments and mathematical modelling. The study shows how urea hydrolysis rate depends on the amount of bacteria and the conditions during growth, storage, hydrolysis and precipitation. The dynamics of Microbially Induced Carbonate Precipitation has been monitored in non-seeded liquid batch experiments. Results show that particulary for a fast hydrolysis of urea (>1 M-urea day-1) in a highly concentrated equimolar solution with calcium chloride (>0.25 M) the solubility product of CaCO3 is exceeded within a short period (less than 30 minutes), the supersaturation remains high for an exended period, resulting in prolonged periods of nucleation and crystal growth and extended growth of metastable precursor mineral phases. The pH, being a result of the speciation, quickly rises until critical supersaturation is reached and precipitation is initiated. Then pH drops (sometimes showing oscillating behaviour) to about neutral where it stays until all substrates are depleted. Higher hydrolysis rates lead to higher supersaturation and pH and relatively many small crystals, whereas higher concentrations of urea and calcium chloride mainly lead to lower pH values. The conversion can be reasonably monitored by electrical conductivity and reasonably predicted, using a simplified model based on a single reaction as long as the urea hydrolysis rate is known. Complex geochemical models, which include chemical speciciation through acid-base equilibria and kinetic equations to describe mineral precipitation, do not show significant difference from the simplified model regarding the bulk chemistry and the total amount of precipitates. However, experiments show that ureolytic MICP can result in a highly variable crystal morphologies with large variation in the affected hydraulic properties when applied in a porous medium. In order to calculate the number, size and

Chicken eggshells (Gallus gallus domesticus) as carbonate calcium source for biomaterials production; Casca de ovo de galinha caipira (gallus gallus domesticus), como fonte de carbonato de calcio para producao de biomateriais

Energy Technology Data Exchange (ETDEWEB)

Junior, E.A. de O.; Bastos, J.S.B.; Silva, R.C. de S.; Macedo, H.R.A.; Macedo, M. O.C.; Bradim, A.S., E-mail: angelcassiasasilva@gmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Piaui (FIPI), PI (Brazil)

2016-07-01

The eggshells present high levels of calcium carbonate. Calcium carbonate obtained from eggshells has been used in the production of biomaterials with applications in bone regeneration, since it is biocompatible. In this work, calcium carbonate was obtained from eggshells to prepare a composite biomaterial. The presence of calcium carbonate bands was observed through spectrometry in the infrared region. Scanning electron microscopy showed the presence of calcium carbonate particles with different sizes and shapes. Carbonate predominance in the form of calcite was also observed through the X-ray diffraction.

Study of calcium carbonate and sulfate co-precipitation

KAUST Repository

Zarga, Y.

2013-06-01

Co-precipitation of mineral based salts in scaling is still not well understood and/or thermodynamically well defined in the water industry. This study focuses on investigating calcium carbonate (CaCO3) and sulfate mixed precipitation in scaling which is commonly observed in industrial water treatment processes including seawater desalination either by thermal-based or membrane-based processes. Co-precipitation kinetics were studied carefully by monitoring several parameters simultaneously measured, including: pH, calcium and alkalinity concentrations as well as quartz microbalance responses. The CaCO3 germination in mixed precipitation was found to be different than that of simple precipitation. Indeed, the co-precipitation of CaCO3 germination time was not anymore related to supersaturation as in a simple homogenous precipitation, but was significantly reduced when the gypsum crystals appeared first. On the other hand, the calcium sulfate crystals appear to reduce the energetic barrier of CaCO3 nucleation and lead to its precipitation by activating heterogeneous germination. However, the presence of CaCO3 crystals does not seem to have any significant effect on gypsum precipitation. IR spectroscopy and the Scanning Electronic Microscopy (SEM) were used to identify the nature of scales structures. Gypsum was found to be the dominant precipitate while calcite and especially vaterite were found at lower proportions. These analyses showed also that gypsum crystals promote calcite crystallization to the detriment of other forms. © 2013 Elsevier Ltd.

Novel mechanism for the modification of Al2O3-based inclusions in ultra-low carbon Al-killed steel considering the effects of magnesium and calcium

Science.gov (United States)

Guo, Jing; Cheng, Shu-sen; Guo, Han-jie; Mei, Ya-guang

2018-03-01

Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al2O3-based inclusions during secondary refining. The results showed that Al2O3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO-MgO-Al2O3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3wt% and the temperature is higher than 1843 K.

Calcium carboorthovanadate - a new compound with the apa

International Nuclear Information System (INIS)

Slobodin, B.V.; Dmitrieva, O.I.; Fotiev, A.A.

1977-01-01

Data on calcium carboorthovanadate, Ca 10 (VO 4 ) 6 CO 3 , a new compound with an appatite structure based on calcium orthovanadate, are reported. The synthesis has been conducted in a stoichiometric mixture of finely ground calcium carbonate and calcium orthovanadate. It is found that calcium carboorthovanadate belongs to the hexagonal syngony and has an apatite structure. An analysis of the infrared spectra of initial compounds and calcium carboorthovanadate confirmed the presence of carbonate (CO 3 ) 2- and orthovanadate (VO 4 ) 3 groupings in the latter. On heating in air, beginning with 450 deg C calcium carboorthovanadate decomposes at a slow rate into calcium oxide, calcium orthovanadate, and carbon dioxide

Reaction studies of hot silicon, germanium and carbon atoms

International Nuclear Information System (INIS)

Gaspar, P.P.

1990-01-01

The goal of this project was to increase the authors understanding of the interplay between the kinetic and electronic energy of free atoms and their chemical reactivity by answering the following questions: (1) what is the chemistry of high-energy carbon silicon and germanium atoms recoiling from nuclear transformations; (2) how do the reactions of recoiling carbon, silicon and germanium atoms take place - what are the operative reaction mechanisms; (3) how does the reactivity of free carbon, silicon and germanium atoms vary with energy and electronic state, and what are the differences in the chemistry of these three isoelectronic atoms? This research program consisted of a coordinated set of experiments capable of achieving these goals by defining the structures, the kinetic and internal energy, and the charge states of the intermediates formed in the gas-phase reactions of recoiling silicon and germanium atoms with silane, germane, and unsaturated organic molecules, and of recoiling carbon atoms with aromatic molecules. The reactions of high energy silicon, germanium, and carbon atoms created by nuclear recoil were studied with substrates chosen so that their products illuminated the mechanism of the recoil reactions. Information about the energy and electronic state of the recoiling atoms at reaction was obtained from the variation in end product yields and the extent of decomposition and rearrangement of primary products (usually reactive intermediates) as a function of total pressure and the concentration of inert moderator molecules that remove kinetic energy from the recoiling atoms and can induce transitions between electronic spin states. 29 refs

Reactions of carbon atoms in pulsed molecular beams

Energy Technology Data Exchange (ETDEWEB)

Reisler, H. [Univ. of Southern California, Los Angeles (United States)

1993-12-01

This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

Heterogeneously Catalysed Chemical Reactions in Carbon Dioxide Medium

DEFF Research Database (Denmark)

Musko, Nikolai E.

In this PhD-study the different areas of chemical engineering, heterogeneous catalysis, supercritical fluids, and phase equilibrium thermodynamics have been brought together for selected reactions. To exploit the beneficial properties of supercritical fluids in heterogeneous catalysis, experimental...... studies of catalytic chemical reactions in dense and supercritical carbon dioxide have been complemented by the theoretical calculations of phase equilibria using advanced thermodynamic models. In the recent years, the use of compressed carbon dioxide as innovative, non-toxic and non-flammable, cheap......, and widely available reaction medium for many practical and industrial applications has drastically increased. Particularly attractive are heterogeneously catalysed chemical reactions. The beneficial use of CO2 is attributed to its unique properties at dense and supercritical states (at temperatures...

Growth and Destruction of PAH Molecules in Reactions with Carbon Atoms

Energy Technology Data Exchange (ETDEWEB)

Krasnokutski, Serge A.; Huisken, Friedrich; Jäger, Cornelia; Henning, Thomas [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Helmholtzweg 3, D-07743 Jena (Germany)

2017-02-10

A very high abundance of atomic carbon in the interstellar medium (ISM), and the high reactivity of these species toward different hydrocarbon molecules including benzene, raise questions regarding the stability of polycyclic aromatic hydrocarbon (PAH) molecules in space. To test the efficiency of destruction of PAH molecules via reactions with atomic carbon, we performed a set of laboratory and computational studies of the reactions of naphthalene, anthracene, and coronene molecules with carbon atoms in the ground state. The reactions were investigated in liquid helium droplets at T = 0.37 K and by quantum chemical computations. Our studies suggest that all small and all large catacondensed PAHs react barrierlessly with atomic carbon, and therefore should be efficiently destroyed by such reactions in a broad temperature range. At the same time, large compact pericondensed PAHs should be more inert toward such a reaction. In addition, taking into account their higher photostability, much higher abundances of pericondensed PAHs should be expected in various astrophysical environments. The barrierless reactions between carbon atoms and small PAHs also suggest that, in the ISM, these reactions could lead to the bottom-up formation of PAH molecules.

Kinetic study of the reaction of uranium with various carbon-containing gases

International Nuclear Information System (INIS)

Feron, G.

1963-09-01

The kinetic study of the reaction U + CO 2 and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO 2 → UO 2 + 2 CO U + CO 2 → UO 2 + C The reaction with carbon monoxide leads to a mixture of dioxide UO 2 , dicarbide UC 2 and free carbon. The main reaction can be written. U + CO → 1/2 UO 2 + 1/2 UC 2 The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO 2 and UC 2 can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO 2 and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [fr

Bacillus megaterium mediated mineralization of calcium carbonate as biogenic surface treatment of green building materials.

Science.gov (United States)

Dhami, Navdeep Kaur; Reddy, M Sudhakara; Mukherjee, Abhijit

2013-12-01

Microbially induced calcium carbonate precipitation is a biomineralization process that has various applications in remediation and restoration of range of building materials. In the present study, calcifying bacteria, Bacillus megaterium SS3 isolated from calcareous soil was applied as biosealant to enhance the durability of low energy, green building materials (soil-cement blocks). This bacterial isolate produced high amounts of urease, carbonic anhydrase, extra polymeric substances and biofilm. The calcium carbonate polymorphs produced by B. megaterium SS3 were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction and Fourier transmission infra red spectroscopy. These results suggested that calcite is the most predominant carbonate formed by this bacteria followed by vaterite. Application of B. megaterium SS3 as biogenic surface treatment led to 40 % decrease in water absorption, 31 % decrease in porosity and 18 % increase in compressive strength of low energy building materials. From the present investigation, it is clear that surface treatment of building materials by B. megaterium SS3 is very effective and eco friendly way of biodeposition of coherent carbonates that enhances the durability of building materials.

Reaction of phosphorus ylides with carbonyl compounds in supercritical carbon dioxide

Energy Technology Data Exchange (ETDEWEB)

Jeong, Kyung Il; Kim, Hak Do; Shim, Jae Jin; Ra, Choon Sup [Yeungnam Univ., Gyongsan (Korea, Republic of)

2004-02-15

The condensation reaction of (benzylene)triphenylphosphoranes with carbonyl compounds in supercritical carbon dioxide was examined. Reactions of (benzylene)phosphoranes (ca. 1 mmol) with several benzaldehydes in a supercritical carbon dioxide (80 .deg. C, 2,000 psi) containing THF entrainer (5%) in a 24 mL reactor proceed smoothly to yield olefination products in fairly good to excellent yields but slower, compared to reactions in a conventional THF solvent. Generally, phosphoranes that are not substituted with a nitro group show more (Z)-selective reactions with aromatic aldehydes under scCO{sub 2} condition than in THF. The reaction of (benzylene)triphenylphosphosphoranes with 4-t-butylcyclohexanone gave the corresponding olefin compounds with a low conversion under both the supercritical carbon dioxide and the organic THF solvent. Our preliminary study showed the Wittig reaction carries out smoothly in supercritical carbon dioxide medium and also a possible tunability of this reaction pathway by adding a entrainer. The results would be useful for devising a novel process for the environmentally friendly Wittig reaction.

Design of in situ dispersible and calcium cross-linked alginate pellets as intestinal-specific drug carrier by melt pelletization technique.

Science.gov (United States)

Nurulaini, Harjoh; Wong, Tin Wui

2011-06-01

Conventional alginate pellets underwent rapid drug dissolution and loss of multiparticulate characteristics such as aggregation in acidic medium, thereby promoting oral dose dumping. This study aimed to design sustained-release dispersible alginate pellets through rapid in situ matrix dispersion and cross-linking by calcium salts during dissolution. Pellets made of alginate and calcium salts were prepared using a solvent-free melt pelletization technique that prevented reaction between processing materials during agglomeration and allowed such a reaction to occur only in dissolution phase. Drug release was remarkably retarded in acidic medium when pellets were formulated with water-soluble calcium acetate instead of acid-soluble calcium carbonate. Different from calcium salt-free and calcium carbonate-loaded matrices that aggregated or underwent gradual erosion, rapid in situ solvation of calcium acetate in pellets during dissolution resulted in burst of gas bubbles, fast pellet breakup, and dispersion. The dispersed fragments, though exhibiting a larger specific surface area for drug dissolution than intact matrix, were rapidly cross-linked by Ca(2+) from calcium acetate and had drug release retarded till a change in medium pH from 1.2 to 6.8. Being dispersible and pH-dependent in drug dissolution, these pellets are useful as multiparticulate intestinal-specific drug carrier without exhibiting dose dumping tendency of a "single-unit-like" system via pellet aggregation. Copyright © 2011 Wiley-Liss, Inc.

A strategy of precipitated calcium carbonate (CaCO{sub 3}) fillers for enhancing the mechanical properties of polypropylene polymers

Energy Technology Data Exchange (ETDEWEB)

Thenepalli, Thriveni; Ahn, Ji Whan [Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon (Korea, Republic of); Ahn, Young Jun; Han, Choon [Kwangwoon University, Seoul (Korea, Republic of); Ramakrishna, Chilakala [Hanil Cement, Danyang (Korea, Republic of)

2015-06-15

A wide variety of fillers are currently used in more than twenty types of polymer resins, although four of them alone (polypropylene, polyamides, thermoplastic polyesters, and polyvinyl chloride) account for 90% of the market of mineral fillers in plastics. Polypropylene (PP) and PVC dominate the market for calcium carbonate. PP is a versatile reinforcement material that can meet engineering and structural specifications and is widely used for automotive components, home appliances, and industrial applications. Talc, mica, clay, kaolin, wollastonite, calcium carbonates, feldspar, aluminum hydroxide, glass fibers, and natural fibers are commonly used in fillers. Among these, calcium carbonate (both natural and synthetic) is the mos abundant and affords the possibility of improved surface finishing, control over the manufacture of products, and increased electric resistance and impact resistance. Meeting the global challenge to reduce the weight of vehicles by using plastics is a significant issue. The current the global plastic and automobile industry cannot survive without fillers, additives, and reinforcements. Polypropylene is a major component of the modern plastic industry, and currently is used in dashboards, wheel covers, and some engine parts in automobiles. This article reports that the use of calcium carbonate fillers with polypropylene is the best choice to enhance the mechanical properties of plastic parts used in automobiles.

The influence of pore-water advection, benthic photosynthesis, and respiration on calcium carbonate dynamics in reef sands

NARCIS (Netherlands)

Rao, A.M.F.; Polerecky, L.; Ionescu, D.; Meysman, F.J.R.; de-Beer, D.

2012-01-01

To investigate diel calcium carbonate (CaCO₃) dynamics in permeable coral reef sands, we measured pore-water profiles and fluxes of oxygen (O₂), nutrients, pH, calcium (Ca²⁺), and alkalinity (TA) across the sediment-water interface in sands of different permeability

Reactor design considerations in mineral sequestration of carbon dioxide

International Nuclear Information System (INIS)

Ityokumbul, M.T.; Chander, S.; O'Connor, William K.; Dahlin, David C.; Gerdemann, Stephen J.

2001-01-01

One of the promising approaches to lowering the anthropogenic carbon dioxide levels in the atmosphere is mineral sequestration. In this approach, the carbon dioxide reacts with alkaline earth containing silicate minerals forming magnesium and/or calcium carbonates. Mineral carbonation is a multiphase reaction process involving gas, liquid and solid phases. The effective design and scale-up of the slurry reactor for mineral carbonation will require careful delineation of the rate determining step and how it changes with the scale of the reactor. The shrinking core model was used to describe the mineral carbonation reaction. Analysis of laboratory data indicates that the transformations of olivine and serpentine are controlled by chemical reaction and diffusion through an ash layer respectively. Rate parameters for olivine and serpentine carbonation are estimated from the laboratory data

Ocean acidification and calcium carbonate saturation states in the coastal zone of the West Antarctic Peninsula

NARCIS (Netherlands)

Jones, E.M.; Fenton, M.; Meredith, M.P.; Clargo, N.M.; Ossebaar, S.; Ducklow, H.W.; Venables, H.J.; De Baar, H.J.W.

2017-01-01

The polar oceans are particularly vulnerable to ocean acidification; the lowering of seawater pH and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide (CO2). High spatial variability in surface water pH and saturation states (Ω) for two biologically-important calcium

Effects of Calcium Carbonate on Pain Symptoms in Third Trimester of Pregnancy and Nursing Period: a randomized clinical trial

Directory of Open Access Journals (Sweden)

Soosan Alimohammadzadeh Taher

2008-06-01

Full Text Available Objective: The study evaluated the efficacy of oral calcium carbonate supplement on leg pain in pregnancy and nursing period.Materials and methods: A total number of 176 women at third trimester of pregnancy or nursing period till to one year after delivery with complaint of leg pain, low back pain (LBP, and posterior pelvic pain (PPP were evaluated for distinct primary causes and were excluded, then 58 patients randomized into calcium group (n=27 treated with 500 mg calcium carbonate orally per day just for one week, and control group (n=31 received no drug. Incidence of days with leg, low back, and posterior pelvic pain per week were evaluated and compared between the two groups at 3 different weeks before, during, and after discontinuation of drug. Statistical significance was defined as P<0.05.  Results: Mean number of days with leg pain per week during calcium carbonate intake was significantly different between the study and control groups (P<0.05. Mean number of days with LBP and PPP was not significantly different between two groups.Conclusion: The use of oral calcium supplement was associated with lower episodes of leg pain but failed to reduce the incidence of LBP and PPP in pregnancy and nursery period.

Elastic modulus of the alkali-silica reaction rim in a simplified calcium-alkali-silicate system determined by nano-indentation

NARCIS (Netherlands)

Zheng, Kunpeng; Lukovic, M.; De Schutter, Geert; Ye, G.; Taerwe, Luc

2016-01-01

This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)2 in a

Calcium and chemical looping technology for power generation and carbon dioxide (CO2) capture solid oxygen- and CO2-carriers

CERN Document Server

Fennell, Paul

2015-01-01

Calcium and Chemical Looping Technology for Power Generation and Carbon Dioxide (CO2) Capture reviews the fundamental principles, systems, oxygen carriers, and carbon dioxide carriers relevant to chemical looping and combustion. Chapters review the market development, economics, and deployment of these systems, also providing detailed information on the variety of materials and processes that will help to shape the future of CO2 capture ready power plants. Reviews the fundamental principles, systems, oxygen carriers, and carbon dioxide carriers relevant to calcium and chemical loopingProvi

Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

International Nuclear Information System (INIS)

Li, Xuerun; Zhang, Yu; Shen, Xiaodong; Wang, Qianqian; Pan, Zhigang

2014-01-01

The formation kinetics of tricalcium aluminate (C 3 A) and calcium sulfate yielding calcium sulfoaluminate (C 4 A 3 $) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C 3 A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca 3 Al 2 O 6 + CaSO 4 → Ca 4 Al 6 O 12 (SO 4 ) + 6CaO was the primary reaction 4 Al 6 O 12 (SO 4 ) + 10CaO → 6Ca 3 Al 2 O 6 + 2SO 2 ↑ + O 2 ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C 4 A 3 $ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C 4 A 3 $ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca 2+ and SO 4 2− were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C 3 A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion

Influence of calcium carbonate on the decomposition of asbestos contained in end-of-life products

Energy Technology Data Exchange (ETDEWEB)

Belardi, G. [Environmental Geology and GeoEngineering Institute (CNR), Area della ricerca RM1, via Salaria km 29,300, 00016 Monterotondo (Rome) (Italy); Piga, L., E-mail: luigi.piga@uniroma1.it [Department of Chemical Engineering, Materials and Environment, Sapienza University of Rome, via Eudossiana 84, 00184 Rome (Italy)

2013-12-10

Highlights: • We characterized end-of-life asbestos-containing materials. • In the range 620–680 °C, calcite and quartz affect decomposition of asbestos. • Hypothesized decomposition reactions match with solid phases revealed by XRD analysis. • TGA of the content of chrysotile gives good results both in air and in nitrogen. - Abstract: Three bearing-asbestos wastes, friction material, vinyl-asbestos (linoleum) and cement-asbestos mainly containing chrysotile were characterized. Powder X-ray diffraction (XRDP), scanning electron microscopy (SEM) with microanalysis observations and thermal analysis (TGA/DTA) were carried out on the materials as received and after heating at 1100 °C in order to observe their structural changes and thermal behaviours. A quantitative determination of chrysotile in the friction material was also carried out. To study the influence of CaCO{sub 3} on the decomposition of asbestos, the three techniques were also applied on the linoleum and cement-asbestos at room temperature and at 1100 °C after leaching of the materials with 1:3 HCl to remove the carbonates present in the wastes. The results show that the presence of CaCO{sub 3} prevents the asbestos to decompose according to the known decomposition reactions and leads to the formation of calcium-silicate compounds. When CaCO{sub 3} is removed by washing with HCl, decomposition of asbestos proceeds according to the expected reactions.

Influence of calcium carbonate on the decomposition of asbestos contained in end-of-life products

International Nuclear Information System (INIS)

Belardi, G.; Piga, L.

2013-01-01

Highlights: • We characterized end-of-life asbestos-containing materials. • In the range 620–680 °C, calcite and quartz affect decomposition of asbestos. • Hypothesized decomposition reactions match with solid phases revealed by XRD analysis. • TGA of the content of chrysotile gives good results both in air and in nitrogen. - Abstract: Three bearing-asbestos wastes, friction material, vinyl-asbestos (linoleum) and cement-asbestos mainly containing chrysotile were characterized. Powder X-ray diffraction (XRDP), scanning electron microscopy (SEM) with microanalysis observations and thermal analysis (TGA/DTA) were carried out on the materials as received and after heating at 1100 °C in order to observe their structural changes and thermal behaviours. A quantitative determination of chrysotile in the friction material was also carried out. To study the influence of CaCO 3 on the decomposition of asbestos, the three techniques were also applied on the linoleum and cement-asbestos at room temperature and at 1100 °C after leaching of the materials with 1:3 HCl to remove the carbonates present in the wastes. The results show that the presence of CaCO 3 prevents the asbestos to decompose according to the known decomposition reactions and leads to the formation of calcium-silicate compounds. When CaCO 3 is removed by washing with HCl, decomposition of asbestos proceeds according to the expected reactions

Kinetic concepts of thermally stimulated reactions in solids

Science.gov (United States)

Vyazovkin, Sergey

Historical analysis suggests that the basic kinetic concepts of reactions in solids were inherited from homogeneous kinetics. These concepts rest upon the assumption of a single-step reaction that disagrees with the multiple-step nature of solid-state processes. The inadequate concepts inspire such unjustified anticipations of kinetic analysis as evaluating constant activation energy and/or deriving a single-step reaction mechanism for the overall process. A more adequate concept is that of the effective activation energy, which may vary with temperature and extent of conversion. The adequacy of this concept is illustrated by literature data as well as by experimental data on the thermal dehydration of calcium oxalate monohydrate and thermal decomposition of calcium carbonate, ammonium nitrate and 1,3,5,7- tetranitro-1,3,5,7-tetrazocine.

The role microbial sulfate reduction in the direct mediation of sedimentary authigenic carbonate precipitation

Science.gov (United States)

Turchyn, A. V.; Walker, K.; Sun, X.

2016-12-01

The majority of modern deep marine sediments are bathed in water that is undersaturated with respect to calcium carbonate. However, within marine sediments changing chemical conditions, driven largely by the microbial oxidation of organic carbon in the absence of oxygen, lead to supersaturated conditions and drive calcium carbonate precipitation. This sedimentary calcium carbonate is often called `authigenic carbonate', and is found in the form of cements and disseminated crystals within the marine sedimentary pile. As this precipitation of this calcium carbonate is microbially mediated, identifying authigenic carbonate within the geological record and understanding what information its geochemical and/or isotopic signature may hold is key for understanding its importance and what information it may contain past life. However, the modern controls on authigenic carbonate precipitation remain enigmatic because the myriad of microbially mediated reactions occurring within sediments both directly and indirectly impact the proton balance. In this submission we present data from 25 ocean sediment cores spanning the globe where we explore the deviation from the stoichiometrically predicted relationships among alkalinity, calcium and sulfate concentrations. In theory for every mol of organic carbon reduced by sulfate, two mol of alkalinity is produced, and to precipitate subsurface calcium carbonate one mol of calcium is used to consume two mol of alkalinity. We use this data with a model to explore changes in carbonate saturation state with depth below the seafloor. Alkalinity changes in the subsurface are poorly correlated with changes in calcium concentrations, however calcium concentrations are directly and tightly coupled to changes in sulfate concentrations in all studied sites. This suggests a direct role for sulfate reducing bacteria in the precipitation of subsurface carbonate cements.

Mineral Carbonation of Phosphogypsum Waste for Production of Useful Carbonate and Sulfate Salts

Energy Technology Data Exchange (ETDEWEB)

Mattila, Hannu-Petteri, E-mail: hmattila@abo.fi; Zevenhoven, Ron [Thermal and Flow Engineering Laboratory, Åbo Akademi University, Turku (Finland)

2015-11-16

Phosphogypsum (CaSO{sub 4}·2H{sub 2}O, PG) waste is produced in large amounts during phosphoric acid (H{sub 3}PO{sub 4}) production. Minor quantities are utilized in construction or agriculture, while most of the material is stockpiled, creating an environmental challenge to prevent pollution of natural waters. In principle, the gypsum waste could be used to capture several hundred megatonnes of carbon dioxide (CO{sub 2}). For example, when gypsum is converted to ammonium sulfate [(NH{sub 4}){sub 2}SO{sub 4}] with ammonia (NH{sub 3}) and CO{sub 2}, also solid calcium carbonate (CaCO{sub 3}) is generated. The ammonium sulfate can be utilized as a fertilizer or in other mineral carbonation processes that use magnesium silicate-based rock as feedstock, while calcium carbonate has various uses as, e.g., filler material. The reaction extent of the described process was studied by thermodynamic modeling and experimentally as a function of reactant concentrations and temperature. Other essential properties such as purity and quality of the solid products are also followed. Conversion efficiencies of >95% calcium from PG to calcium carbonate are obtained. Scalenohedral, rhombohedral, and prismatic calcite particles can be produced, although the precipitates contain certain contaminants such as rare earth metals and sulfur from the gypsum. A reverse osmosis membrane cartridge is also tested as an alternative and energy-efficient method of concentrating the ammonium sulfate salt solution instead of the traditional evaporation of the process solution.

Mineral carbonation of phosphogypsum waste for production of useful carbonate and sulfate salts

Directory of Open Access Journals (Sweden)

Hannu-Petteri eMattila

2015-11-01

Full Text Available Phosphogypsum (CaSO4·2H2O waste is produced in large amounts during phosphoric acid (H3PO4 production. Minor quantities are utilized in construction or agriculture, while most of the material is stockpiled, creating an environmental challenge to prevent pollution of natural waters. In principle, the gypsum waste could be used to capture several hundred Mt of carbon dioxide (CO2. For example, when gypsum is converted to ammonium sulfate ((NH42SO4 with ammonia (NH3 and CO2, also solid calcium carbonate (CaCO3 is generated. The ammonium sulfate can be utilized as a fertilizer or in other mineral carbonation processes that use magnesium silicate-based rock as feedstock, while calcium carbonate has various uses as e.g. filler material. The reaction extent of the described process was studied by thermodynamic modeling and experimentally as a function of reactant concentrations and temperature. Other essential properties such as purity and quality of the solid products are also followed. Conversion efficiencies of >95% calcium from phosphogypsum to calcium carbonate are obtained. Scalenohedral, rhombohedral and prismatic calcite particles can be produced, though the precipitates contain certain contaminants such as rare earth metals and sulfur from the gypsum. A reverse osmosis membrane cartridge is also tested as an alternative and energy-efficient method of concentrating the ammonium sulfate salt solution instead of the traditional evaporation of the process solution.

Onsite defluoridation system for drinking water treatment using calcium carbonate.

Science.gov (United States)

Wong, Elaine Y; Stenstrom, Michael K

2018-06-15

Fluoride in drinking water has several effects on teeth and bones. At concentrations of 1-1.5 mg/L, fluoride can strengthen enamel, improving dental health, but at concentrations above 1.5 to 4 mg/L can cause dental fluorosis. At concentrations of 4-10 mg/L, skeletal fluorosis can occur. There are many areas of the world that have excessive fluoride in drinking water, such as China, India, Sri Lanka, and the Rift Valley countries in Africa. Treatment solutions are needed, especially in poor areas where drinking water treatment plants are not available. On-site or individual treatment alternatives can be attractive if constructed from common materials and if simple enough to be constructed and maintained by users. Advanced on-site methods, such as under sink reserve osmosis units, can remove fluoride but are too expensive for developing areas. This paper investigates calcium carbonate as a cost effective sorbent for an onsite defluoridation drinking water system. Batch and column experiments were performed to characterize F - removal properties. Fluoride sorption was described by a Freundlich isotherm model, and it was found that the equilibrium time was approximately 3 h. Calcium carbonate was found to have comparable F - removal abilities as the commercial ion exchange resins and possessed higher removal effectiveness compared to calcium containing eggshells and seashells. It was also found that the anion Cl- did not compete with F - at typical drinking water concentrations, having little impact on the effectiveness of the treatment system. A fluoride removal system is proposed that can be used at home and can be maintained by users. Through this work, we can be a step closer to bringing safe drinking water to those that do not have access to it. Copyright © 2017 Elsevier Ltd. All rights reserved.

Deposition of calcium carbonate into postglacial reefs: a test on a 'coral reef hypothesis'. Kohyoki no sangosho eno tansan calcium taiseki sokudo

Energy Technology Data Exchange (ETDEWEB)

Kayanne, H [Geological Survey of Japan, Tsukuba (Japan)

1993-06-15

This paper describes the following matters on changes in rates of deposition of calcium carbonate into postglacial coral reefs: Estimation was made on change in CaCO3 deposition in four coral reefs the data of which relating to all cross sections down to reef base have been acquired by drilling; the main deposition periods in the coral reefs formed in the postglacial period were five to six thousand years ago; the maximum deposition rate is estimated to be 2.7 [times] 10[sup 14] gC per one thousand years under an assumption that the total deposition amount in postglacial coral reefs is 1.2 [times] 10[sup 18] gC (converted to carbon amount); the recent deposition rate is (1/7.5) that of the former rate; from information obtained on submerged coral reefs, deposition amounts in coral reefs before 10,000 years ago are judged to have been smaller than those thereafter; and the above knowledges do not support the 'coral reef hypothesis' by Berger et al. that deposition of calcium carbonate into postglacial coral reefs has occurred from 15,000 years ago to 10,000 years ago. 30 refs., 2 figs.

Fabrication of carbonate apatite block based on internal dissolution-precipitation reaction of dicalcium phosphate and calcium carbonate.

Science.gov (United States)

Daitou, Fumikazu; Maruta, Michito; Kawachi, Giichiro; Tsuru, Kanji; Matsuya, Shigeki; Terada, Yoshihiro; Ishikawa, Kunio

2010-05-01

In this study, we investigated a novel method for fabrication of carbonate apatite block without ionic movement between precursor and solution by using precursor that includes all constituent ions of carbonate apatite. A powder mixture prepared from dicalcium phosphate anhydrous and calcite at appropriate Ca/P ratios (1.5, 1.67, and 1.8) was used as starting material. For preparation of specimens, the slurry made from the powder mixture and distilled water was packed in a split stainless steel mold and heat - treated, ranging from 60 degrees C to 100 degrees C up to 48 hours at 100% humidity. It appeared that carbonate apatite could be obtained above 70 degrees C and monophasic carbonate apatite could be obtained from the powder mixture at Ca/P ratio of 1.67. Carbonate content of the specimen was about 5-7%. Diametral tensile strength of the carbonate apatite blocks slightly decreased with increasing treatment temperature. The decrease in diametral tensile strength is thought to be related to the crystal size of the carbonate apatite formed.

Adsorption of arsenic by activated carbon, calcium alginate and their composite beads.

Science.gov (United States)

Hassan, A F; Abdel-Mohsen, A M; Elhadidy, H

2014-07-01

The present investigation deals with preparation of three different adsorbent materials namely; potassium hydroxide activated carbon based apricot stone (C), calcium alginate beads (G) and calcium alginate/activated carbon composite beads (GC) were used for the removal of arsenic. The prepared adsorbent materials were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), N2-adsorption at -196°C and point of zero charge. From the obtained results, it was found that the porosity, surface area and total pore volume of the adsorbent material C>GC>G respectively, however, the G adsorbent has more acidic function group than the other adsorbents. The influence of pH, time, temperature and initial concentration of arsenic(V) were studied and optimized. GC exhibits the maximum As(V) adsorption (66.7mg/g at 30°C). The adsorption of arsenic ions was observed to follow pseudo-second order mechanism as well as the thermodynamic parameters confirm also the endothermic spontaneous and a physisorption process. Copyright © 2014 Elsevier B.V. All rights reserved.

Optical excitation of carbon nanotubes drives stoichiometric reaction with diazonium salts

Science.gov (United States)

Powell, Lyndsey; Piao, Yanmei; Wang, Yuhuang; YuHuang Wang Research Group Team

Covalent chemistry is known to lack the precision required to tailor the physical properties of carbon nanostructures. Here we show that, for the first time, light can be used to drive a typically inefficient reaction with single-walled carbon nanotubes in a more stoichiometric fashion. Specifically, our experimental results suggest that light can enhance the reaction rate of diazonium salt with carbon nanotubes by as much as 35-fold, making possible stoichiometric control of the covalent bonding of a functional group to the sp2 carbon lattice. This light-controlled reaction paves the way for the possibility of highly selective and precise chemistry on single-walled carbon nanotubes and other graphitic nanostructures.

模板法合成碳酸钙研究进展%Progress of preparation of calcium carbonate with template method

Institute of Scientific and Technical Information of China (English)

陈彰旭; 辛梅华; 李明春; 陈晓东

2014-01-01

碳酸钙是最丰富的生物矿物材料之一，不同形貌、不同晶型的碳酸钙可适用于印刷、陶瓷、涂料、医学等不同领域。模板法因其可以有效地控制合成碳酸钙的形貌、结构和尺寸，而成为目前制备碳酸钙的重要手段之一。本文结合近几年模板法控制合成碳酸钙的发展，综述了利用小分子、天然生物大分子、凝胶体、微乳液、聚合物等介质作为软模板合成碳酸钙的研究进展，同时简述了硬模板法合成碳酸钙的研究进展，分析比较了各种介质作为模板调控碳酸钙的优缺点，综述了模板法制备碳酸钙未来发展的主要方向及面临的问题。在此基础上，指出深入系统研究模板法调控合成碳酸钙的作用机理，结合电化学等现代技术手段，不断完善调控碳酸钙的晶型和形貌的技术，成为未来研究的重点。%Calcium carbonate is one of most abundant biological minerals. Calcium carbonate with multi-morphologies and different polymorphs can be used in different fields,including printing, ceramics,paints,and medicine. The template method is preferable to other approaches for synthesis of calcium carbonate,as its morphology and polymorph can be effectively controlled by simply altering the nature of template and preparation conditions. This paper reviews the development in preparation of calcium carbonate by using small molecule,natural macromolecule,gel,microemulsion and polymer as soft templates. The synthesis of calcium carbonate by using hard template is also described. The main development directions and problems in preparing calcium carbonate are analyzed by comparing the advantages and disadvantages of various matrixes. Finally,preparation of calcium carbonate and other biomaterials with the template method is prospected. The mechanism of synthesis of calcium carbonate with the template method,and using electrochemistry and other modern technology to improve the

Mg-doped biphasic calcium phosphate by a solid state reaction route: Characterization and evaluation of cytotoxicity

Energy Technology Data Exchange (ETDEWEB)

Webler, Geovana D. [Instituto de Física, Universidade Federal de Alagoas, Maceió-AL 57072970 (Brazil); Correia, Ana C.C.; Barreto, Emiliano [Laboratório de Biologia Celular, Universidade Federal de Alagoas, Maceió-AL 57072970 (Brazil); Fonseca, Eduardo J.S., E-mail: eduardo@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, Maceió-AL 57072970 (Brazil)

2015-07-15

Hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) are widely used in tissue engineering because of their chemical similarity to the inorganic bone phase. In this work, we prepare biphasic calcium phosphate (BCP, a mixture of HAP and β-TCP) doped with different concentrations of magnesium to investigate the influence of magnesium on the BCP crystal structure. Magnesium is known to be an important element in the composition of bones and teeth. Recent research has shown that the doping of magnesium into BCP improves its bone metabolism and mechanical properties without affecting its biocompatibility. The samples were prepared by solid-state reaction from calcium carbonate, monobasic ammonium phosphate, and magnesium nitrate hexahydrate. Varying concentrations of magnesium were used and its modifications were examined by different characterization techniques. The phase composition and morphology of the ceramic powders were characterized by X-ray diffraction and scanning electron microscopy, respectively. The functional groups were analyzed using Fourier transform infrared spectroscopy and Raman spectroscopy. Cell viability experiments, using macrophage-like cell lines J774, showed that the synthesized Mg-doped BCP did not exhibit cytotoxicity regardless of the doses assayed or the different concentrations of magnesium used, suggesting it as a good material for potential biological applications. - Highlights: • Simple and fast method for the preparation of the Mg-BCP. • Study of the influence of the incorporation of Mg in the BCP. • Cell viability showed that the synthesized Mg-BCP did not exhibit cytotoxicity.

Mg-doped biphasic calcium phosphate by a solid state reaction route: Characterization and evaluation of cytotoxicity

International Nuclear Information System (INIS)

Webler, Geovana D.; Correia, Ana C.C.; Barreto, Emiliano; Fonseca, Eduardo J.S.

2015-01-01

Hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) are widely used in tissue engineering because of their chemical similarity to the inorganic bone phase. In this work, we prepare biphasic calcium phosphate (BCP, a mixture of HAP and β-TCP) doped with different concentrations of magnesium to investigate the influence of magnesium on the BCP crystal structure. Magnesium is known to be an important element in the composition of bones and teeth. Recent research has shown that the doping of magnesium into BCP improves its bone metabolism and mechanical properties without affecting its biocompatibility. The samples were prepared by solid-state reaction from calcium carbonate, monobasic ammonium phosphate, and magnesium nitrate hexahydrate. Varying concentrations of magnesium were used and its modifications were examined by different characterization techniques. The phase composition and morphology of the ceramic powders were characterized by X-ray diffraction and scanning electron microscopy, respectively. The functional groups were analyzed using Fourier transform infrared spectroscopy and Raman spectroscopy. Cell viability experiments, using macrophage-like cell lines J774, showed that the synthesized Mg-doped BCP did not exhibit cytotoxicity regardless of the doses assayed or the different concentrations of magnesium used, suggesting it as a good material for potential biological applications. - Highlights: • Simple and fast method for the preparation of the Mg-BCP. • Study of the influence of the incorporation of Mg in the BCP. • Cell viability showed that the synthesized Mg-BCP did not exhibit cytotoxicity

Carbon nanopipettes characterize calcium release pathways in breast cancer cells

Energy Technology Data Exchange (ETDEWEB)

Schrlau, Michael G [Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104 (United States); Brailoiu, Eugen; Dun, Nae J [Department of Pharmacology, Temple University, Philadelphia, PA 19104 (United States); Patel, Sandip [Department of Physiology, University College London, London WC1E 6BT (United Kingdom); Gogotsi, Yury [Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104 (United States); Bau, Haim H [Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 229 Towne Building, 220 S. 33rd Street, Philadelphia, PA 19104 (United States)], E-mail: mschrlau@seas.upenn.edu, E-mail: ebrailou@temple.edu, E-mail: patel.s@ucl.ac.uk, E-mail: yg36@drexel.edu, E-mail: ndun@temple.edu, E-mail: bau@seas.upenn.edu

2008-08-13

Carbon-based nanoprobes are attractive for minimally invasive cell interrogation but their application in cell physiology has thus far been limited. We have developed carbon nanopipettes (CNPs) with nanoscopic tips and used them to inject calcium-mobilizing messengers into cells without compromising cell viability. We identify pathways sensitive to cyclic adenosine diphosphate ribose (cADPr) and nicotinic acid adenine dinucleotide phosphate (NAADP) in breast carcinoma cells. Our findings demonstrate the superior utility of CNPs for intracellular delivery of impermeant molecules and, more generally, for cell physiology studies. The CNPs do not appear to cause any lasting damage to cells. Their advantages over commonly used glass pipettes include smaller size, breakage and clogging resistance, and potential for multifunctionality such as in concurrent injection and electrical measurements.

Carbon nanopipettes characterize calcium release pathways in breast cancer cells

International Nuclear Information System (INIS)

Schrlau, Michael G; Brailoiu, Eugen; Dun, Nae J; Patel, Sandip; Gogotsi, Yury; Bau, Haim H

2008-01-01

Carbon-based nanoprobes are attractive for minimally invasive cell interrogation but their application in cell physiology has thus far been limited. We have developed carbon nanopipettes (CNPs) with nanoscopic tips and used them to inject calcium-mobilizing messengers into cells without compromising cell viability. We identify pathways sensitive to cyclic adenosine diphosphate ribose (cADPr) and nicotinic acid adenine dinucleotide phosphate (NAADP) in breast carcinoma cells. Our findings demonstrate the superior utility of CNPs for intracellular delivery of impermeant molecules and, more generally, for cell physiology studies. The CNPs do not appear to cause any lasting damage to cells. Their advantages over commonly used glass pipettes include smaller size, breakage and clogging resistance, and potential for multifunctionality such as in concurrent injection and electrical measurements

Reactions of carbonate radical with cobalt(II) aminopolycarboxylates

International Nuclear Information System (INIS)

Mandal, P.C.; Bardhan, D.K.; Bhattacharyya, S.N.

1992-01-01

Reactions of carbonate (CO 3 - radical) and bicarbonate (HCO 3 radical) radicals generated by photolysis of a carbonate or bicarbonate solution at pH 11.2 and 8.5, respectively, with Co(II) complexes of iminodiacetic acid (IDA) and ethylenediaminetetraacetic acid (EDTA) have been studied. The rate constants for the reactions were in the order of 10 6 -10 7 dm 3 mol -1 s -1 . From the time-resolved spectroscopy of the products formed after reaction of CO 3 - radical or HCO 3 radical, it is observed that CO 3 - radical or HCO 3 radical oxidize the metal center to its higher oxidation state. (author) 26 refs.; 2 figs.; 1 tab

Adsorption efficiencies of calcium (II ion and iron (II ion on activated carbon obtained from pericarp of rubber fruit

Directory of Open Access Journals (Sweden)

Orawan Sirichote

2008-03-01

Full Text Available Determination of adsorption efficiencies of activated carbon from pericarp of rubber fruit for calcium (II ion and iron (II ion has been performed by flowing the solutions of these ions through a column of activated carbon. The weights of activated carbon in 500 mL buret column (diameter 3.2 cm for flowing calcium (II ion and iron (II ion solutions were 15 g and 10 g, respectively. The initial concentration of calcium ion was prepared to be about eight times more diluted than the true concentration found in the groundwater from the lower part of southern Thailand. Calcium (II ion concentrations were analysed by EDTA titration and its initial concentration was found to be 23.55 ppm. With a flow rate of 26 mL/min, the adsorption efficiency was 11.4 % with passed through volume 4.75 L. Iron (II ion concentrations were analysed by spectrophotometric method; its initial concentration was found to be 1.5565 ppm. At a flow rate of 22 mL/min, the adsorption efficiency was 0.42 % with passed through volume of 34.0 L.

X-ray Absorption Spectroscopy Identifies Calcium-Uranyl-Carbonate Complexes at Environmental Concentrations

International Nuclear Information System (INIS)

Kelly, Shelly D.; Kemner, Kenneth M.; Brooks, Scott C.

2007-01-01

Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO2-CO3 complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO2-CO3 complex. Such a complex might exist even at high calcium concentrations, as some UO2-CO3 complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 lM uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO2-CO3 complex to approximately 0.6 and enables spectroscopic identification of the Na-UO2-CO3 complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations

Coprecipitation of {sup 14}C and Sr with carbonate precipitates: The importance of reaction kinetics and recrystallization pathways

Energy Technology Data Exchange (ETDEWEB)

Hodkin, David J. [School of Earth and Environment, University of Leeds, Leeds LS2 9JT (United Kingdom); Stewart, Douglas I. [School of Civil Engineering, University of Leeds (United Kingdom); Graham, James T. [National Nuclear Laboratory, Sellafield, Cumbria (United Kingdom); Burke, Ian T., E-mail: I.T.Burke@leeds.ac.uk [School of Earth and Environment, University of Leeds, Leeds LS2 9JT (United Kingdom)

2016-08-15

This study investigated the simultaneous removal of Sr{sup 2+} and {sup 14}CO{sub 3}{sup 2−} from pH > 12 Ca(OH){sub 2} solution by the precipitation of calcium carbonate. Initial Ca{sup 2+}:CO{sub 3}{sup 2−} ratios ranged from 10:1 to 10:100 (mM:mM). Maximum removal of {sup 14}C and Sr{sup 2+} both occurred in the system containing 10 mM Ca{sup 2+} and 1 mM CO{sub 3}{sup 2−} (99.7% and 98.6% removal respectively). A kinetic model is provided that describes {sup 14}C and Sr removal in terms of mineral dissolution and precipitation reactions. The removal of {sup 14}C was achieved during the depletion of the initial TIC in solution, and was subsequently significantly affected by recrystallization of the calcite precipitate from an elongate to isotropic morphology. This liberated > 46% of the {sup 14}C back to solution. Sr{sup 2+} removal occurred as Ca{sup 2+} became depleted in solution and was not significantly affected by the recrystallization process. The proposed reaction could form the basis for low cost remediation scheme for {sup 90}Sr and {sup 14}C in radioactively contaminated waters (<$0.25 reagent cost per m{sup 3} treated). - Highlights: • 99.7% of {sup 14}C and 98.6% of Sr removed from aqueous solution by CaCO{sub 3} precipitation. • Remobilization of {sup 14}C observed during calcium carbonate recrystallization. • Sr displayed variable distribution coefficient (possibly affected by Ca:Sr ratio). • Reagent cost of $0.22/m{sup 3} of treated groundwater.

The effect of crystallization pressure on macromolecular structure, phase evolution, and fracture resistance of nano-calcium carbonate-reinforced high density polyethylene

International Nuclear Information System (INIS)

Yuan, Q.; Yang, Y.; Chen, J.; Ramuni, V.; Misra, R.D.K.; Bertrand, K.J.

2010-01-01

We describe here phase evolution and structural changes that are induced when high density polyethylene (HDPE) containing dispersion of nano-calcium carbonate is isothermally crystallized in the pressure range of 0.1-100 MPa. To delineate and separate the effects of applied crystallization pressure from nanoparticle effects, a relative comparison is made between neat HDPE and HDPE containing nano-calcium carbonate under similar experimental conditions. X-ray diffraction studies point toward the evolution of monoclinic phase at high crystallization pressure together with the commonly observed orthorhombic phase of HDPE. Furthermore, the nucleation of monoclinic phase is promoted by nanoparticles even at low crystallization pressure. The equilibrium melting point is insignificantly influenced on the addition of nanoparticle, such that the crystallization pressure has no obvious effect. The strong thermodynamic interaction between nano-calcium carbonate and HDPE is supported by the shift in glass transition temperature and changes in the modification of absorption bands of HDPE in Fourier transform infrared (FTIR) spectrum. Furthermore, the reinforcement of HDPE with nano-calcium carbonate increases impact strength and alters the micromechanism from crazing-tearing in polyethylene to fibrillated fracture in polymer nanocomposite, such that the fibrillation increases with crystallization pressure.

Initial reaction between CaO and SO₂ under carbonating and non-carbonating conditions

DEFF Research Database (Denmark)

Rasmussen, Martin Hagsted; Wedel, Stig; Pedersen, Kim H.

2015-01-01

The initial kinetics of the CaO/SO2 reaction have been investigated for reaction times shorter than 1s and in the temperature interval between 450 and 600°C under both carbonating and non-carbonating conditions (0-20 vol% CO2) to clarify how recirculating CaO influences the emission of SO2 from...... showed that the CaO conversion with respect to SO2 declined when the CO2 concentration was increased. Under all conditions, larger specific surface areas of CaO gave higher reaction rates with SO2. Higher temperatures had a positive effect on the reaction between SO2 and CaO under non......-carbonating conditions, but no or even a negative effect under carbonating conditions. The results led to the conclusion that SO2 released from raw meal in the upper stages of the preheater does not to any significant extent react with CaO recirculating in the preheater tower....

Sevelamer is cost effective versus calcium carbonate for the first-line treatment of hyperphosphatemia in new patients to hemodialysis: a patient-level economic evaluation of the INDEPENDENT-HD study.

Science.gov (United States)

Ruggeri, Matteo; Bellasi, Antonio; Cipriani, Filippo; Molony, Donald; Bell, Cynthia; Russo, Domenico; Di Iorio, Biagio

2015-10-01

The recent multicenter, randomized, open-label INDEPENDENT study demonstrated that sevelamer improves survival in new to hemodialysis (HD) patients compared with calcium carbonate. The objective of this study was to determine the cost-effectiveness of sevelamer versus calcium carbonate for patients new to HD, using patient-level data from the INDEPENDENT study. Cost-effectiveness analysis. Adult patients new to HD in Italy. A patient-level cost-effectiveness analysis was conducted from the perspective of the Servizio Sanitario Nazionale, Italy's national health service. The analysis was conducted for a 3-year time horizon. The cost of dialysis was excluded from the base case analysis. Sevelamer was compared to calcium carbonate. Total life years (LYs), total costs, and the incremental cost per LY gained were calculated. Bootstrapping was used to estimate confidence intervals around LYs, costs, and cost-effectiveness and to calculate the cost-effectiveness acceptability curve. Sevelamer was associated with a gain of 0.26 in LYs compared to calcium carbonate, over the 3-year time horizon. Total drug costs were €3,282 higher for sevelamer versus calcium carbonate, while total hospitalization costs were €2,020 lower for sevelamer versus calcium carbonate. The total incremental cost of sevelamer versus calcium carbonate was €1,262, resulting in a cost per LY gained of €4,897. The bootstrap analysis demonstrated that sevelamer was cost effective compared with calcium carbonate in 99.4 % of 10,000 bootstrap replicates, assuming a willingness-to-pay threshold of €20,000 per LY gained. Data on hospitalizations was taken from a post hoc retrospective chart review of the patients included in the INDEPENDENT study. Patient quality of life or health utility was not included in the analysis. Sevelamer is a cost-effective alternative to calcium carbonate for the first-line treatment of hyperphosphatemia in new to HD patients in Italy.

Deglacial Millennial-scale Calcium Carbonate Spikes in the North Pacific Ocean

Science.gov (United States)

Chikamoto, M. O.; Timmermann, A.; Harada, N.; Okazaki, Y.

2015-12-01

Numerous paleoproxy records from the subarctic Pacific Ocean show two very pronounced deglacial peaks in calcium carbonate content for the Heinrich 1/ Bolling-Allerod (H1-BA) transition (at 14 ka) and for the Younger Dryas/Preboreal transition (at 11 ka). Focusing on the H1-BA transition, some model simulations capture the North Pacific shift from ventilated to stratified conditions and from cooling to warming conditions via oceanic and atmospheric connections between Atlantic and Pacific Oceans. To test the impact of these physical scenarios (variations in ocean stratification and temperature during the H1-BA transition) on calcite production or preservation, we conduct a series of idealized experiments using the Earth System Model Intermediate Complexity LOVECLIM. The variations in North Pacific Ocean stratification by anomalous freshwater forcing show low calcite productivity in associated with the subsurface nutrient decline. On the other hand, the rapid H1-BA warming of the North Pacific Ocean induced by anomalous heat forcing in turn increases calcite productivity due to the temperature-dependent growth rate of phytoplankton. These results suggest the possibility that the millennial-scale calcium carbonate peaks are the result of surface biogeochemical responses to the climate transition, not by the deep circulation response.

Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

Science.gov (United States)

Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

2010-08-03

A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

Effects of temperature during the irradiation of calcium carbonate

Energy Technology Data Exchange (ETDEWEB)

Negron M, A.; Camargo R, C.; Ramos B, S. [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Gomez V, V. [UNAM, Instituto de Quimica, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Uribe, R. M., E-mail: negron@nucleares.unam.mx [Kent State University, College of Technology, Kent 44240 Ohio (United States)

2015-10-15

The gamma irradiation of calcium carbonate at different doses (0 to 309 kGy) and temperature regimes (77 K to 298 K) was carried out to study the effects of irradiation temperature. The changes were followed by EPR spectroscopy. We observed the formation of a composite EPR spectrum even at low radiation doses and temperature. There is a strong effect on the evaluation of the radicals formed as a function of irradiation temperature, probably due to the diffusion in the frozen powder. Response curves show that this system tends to saturate at 10 MGy at 298 K. (Author)

Effects of temperature during the irradiation of calcium carbonate

International Nuclear Information System (INIS)

Negron M, A.; Camargo R, C.; Ramos B, S.; Gomez V, V.; Uribe, R. M.

2015-10-01

The gamma irradiation of calcium carbonate at different doses (0 to 309 kGy) and temperature regimes (77 K to 298 K) was carried out to study the effects of irradiation temperature. The changes were followed by EPR spectroscopy. We observed the formation of a composite EPR spectrum even at low radiation doses and temperature. There is a strong effect on the evaluation of the radicals formed as a function of irradiation temperature, probably due to the diffusion in the frozen powder. Response curves show that this system tends to saturate at 10 MGy at 298 K. (Author)

Calcium looping technology using improved stability nanostructured sorbent for cyclic CO{sub 2} capture

Energy Technology Data Exchange (ETDEWEB)

Luo, Cong; Zheng, Ying; Ding, Ning; Zheng, Chu-guang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

2013-07-01

One of the post-combustion CO{sub 2} capture technologies that have sufficiently been proved to be the best candidates for practical large scale post-combustion application is the calcium looping cycle. However, the CO{sub 2} capture capacity of a calcium-based sorbent derived from natural limestone decays through long-term cyclic utilization; thus, the development of novel sorbents to achieve a high CO{sub 2} capture capacity is an critical challenge for the calcium looping cycle technology. In this paper, we report the preparation and character of a new calcium-based sorbent produced via the combustion of a dry gel. The results show that the novel calcium-based sorbent has a much higher residual carbonation conversion as well as a better performance of anti-sintering when compared with the calcium-based sorbent derived from commercial micrometer grade CaCO{sub 3} and nanometer grade CaCO{sub 3}. It is reasonable to propose that the different final carbonation performances are induced by their different pore structures and BET surface areas rather than by different particle sizes. Compared with the commercial nano CaO, the morphology of the new sorbent shows a more rough porous appearance with hollow nanostructure. During carbonation, CO{sub 2} diffused more easily through the hollow structure than through a solid structure to reach the unreacted CaO. Besides, there is less chance for the hollow nanostructured particles to be merged together during the high temperature reactions.

Increasing of prediction reliability of calcium carbonate scale formation in heat exchanger of secondary coolant circuits of thermal and nuclear power plants

International Nuclear Information System (INIS)

Tret'yakov, O.V.; Kritskij, V.G.; Styazhkin, P.S.

1991-01-01

Calcium carbonate scale formation in the secondary circuit heat exchanger of thermal and nuclear power plants is investigated. A model of calcium-carbonate scale formation providing quite reliable prediction of process running and the possibility of its control affecting the parameters of hydrochemical regime (HCR) is developed. The results can be used when designing the automatic-control system of HCR

The fate of calcium carbonate nanoparticles administered by oral route: absorption and their interaction with biological matrices

Directory of Open Access Journals (Sweden)

Lee JA

2015-03-01

Full Text Available Jeong-A Lee,1,* Mi-Kyung Kim,1,* Hyoung-Mi Kim,2,* Jong Kwon Lee,3 Jayoung Jeong,4 Young-Rok Kim,5 Jae-Min Oh,2 Soo-Jin Choi1 1Department of Food Science and Technology, Seoul Women’s University, Seoul, Republic of Korea; 2Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Republic of Korea; 3Hazard Substances Analysis Division, Gwangju Regional Food and Drug Administration, Ministry of Food and Drug Safety, Gwangju, Republic of Korea; 4Toxicological Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety, Chungcheongbuk-do, Republic of Korea; 5Department of Food Science and Biotechnology, Kyung Hee University, Yongin, Republic of Korea *These authors contributed equally to this work Background: Orally administered particles rapidly interact with biological fluids containing proteins, enzymes, electrolytes, and other biomolecules to eventually form particles covered by a corona, and this corona potentially affects particle uptake, fate, absorption, distribution, and elimination in vivo. This study explored relationships between the biological interactions of calcium carbonate particles and their biokinetics.Methods: We examined the effects of food grade calcium carbonates of different particle size (nano [N-Cal] and bulk [B-Cal]: specific surface areas of 15.8 and 0.83 m2/g, respectively on biological interactions in in vitro simulated physiological fluids, ex vivo biofluids, and in vivo in gastrointestinal fluid. Moreover, absorption and tissue distribution of calcium carbonates were evaluated following a single dose oral administration to rats.Results: N-Cal interacted more with biomatrices than bulk materials in vitro and ex vivo, as evidenced by high fluorescence quenching ratios, but it did not interact more actively with biomatrices in vivo. Analysis of coronas revealed that immunoglobulin, apolipoprotein, thrombin, and fibrinogen

Class and Home Problems: Carbon Dioxide Capture from Coal-Fired Power Plants Using Calcium Looping

Science.gov (United States)

Deshpande, Niranjani; Phalak, Nihar; Fan, Liang-Shih; Sundaresan, Sankaran

2015-01-01

Calcium looping is based on the simple premise of the reversible reaction between CO[subscript 2] and CaO. This reaction can be used for separation of CO2 from a mixture of gases; most notably the technology finds applications in CO[subscript 2] removal from gas streams in fossil fuel-based energy systems. This article gives a brief overview of…

Factors effecting carbonate equilibria in natural waters

International Nuclear Information System (INIS)

Snellman, M.

1987-12-01

This study is related to preliminary stie evaluations to be carried out in 1987-1992 for spent nuclear fuel disposal in Finland. Near surface and shallow groundwaters are characterized by high concentration of calcium and bicarbonate due to dissolution of calcite. The input of carbon dioxide in the upper zone of the bedrock has a strong influence on the pH giving a pH around neutral. In deep groundwaters when the system is no longer open to the input of carbon dioxide the pH rises as the carbonate system is displaced towards the bicarbonate-carbonate site. In still deeper parts of the rock weathering of other minerals such as feldspars affects the chemistry raising the pH and resulting in saturation and precipitation of calcite. The more advanced these reactions become the higher is the pH and the lower is the carbonate content. The equilibrium concentrations of carbonate species are affected both by temperature and ionic strength of the waters, at high ionic strength especially the distribution between bicarbonate and carbonate ions is affected. The total concentration of carbonates in groundwaters is determined through complex interaction between calcite and carbonates in the water. In deep groundwaters which are closed for input of CO 2 the concentration is stated to be regulated by dissolution of calcium carbonate. In deep granitic groundwaters pH is stated to be buffered to 6.5 to 10, where a high pH would correspond to a low total carbonate concentration and often also a low calcium concentration and a low pH would correspond to high carbonae and calcium concentrations

Absorption of carbon dioxide and isotope exchange rate of carbon in a reaction system between carbon dioxide and carbamic acid

International Nuclear Information System (INIS)

Takeshita, Kenji; Kitamoto, Asashi

1985-01-01

The performance of isotope separation of carbon-13 by chemical exchange between carbon dioxide and carbamic acid was studied. The working fluid used in the study was a solution of DNBA, (C 4 H 9 ) 2 NH and n-octane mixture. Factors related to the isotope exchange rate were measured, such as the absorption rate of carbon dioxide into the solution of DNBA and n-octane, the isotope exchange rate and the separation factor in the reaction between CO 2 and carbamic acid. The absorption of CO 2 into the working fluid was the sum of chemical absorption by DNBA and physical absorption by n-octane. The absorption of carbon dioxide into the working fluid was negligible at temperatures over 90 0 C, but increased gradually at lower temperatures. Carbon dioxide was absorbed into DNBA by chemical absorption, and DNBA was converted to carbamic acid by the reaction. The reaction for synthesis and decomposition of carbamic acid was reversible. The separation factor in equilibrium reached a large value at lower temperatures. The isotope exchange rate between gas and liquid was proportional to the product of the concentration of carbamic acid and the concentration of CO 2 by physical absorption. The isotope separation of carbon by chemical exchange reaction is better operated under the conditions of lower temperature and higher pressure. (author)

Effect of polymers on the nanostructure and on the carbonation of calcium silicate hydrates: a scanning transmission X-ray microscopy study

KAUST Repository

Ha, J.

2011-09-07

This study investigated the effects of organic polymers (polyethylene glycol and hexadecyltrimethylammonium) on structures of calcium silicate hydrates (C-S-H) which is the major product of Portland cement hydration. Increased surface areas and expansion of layers were observed for all organic polymer modified C-S-H. The results from attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic measurements also suggest lowered water contents in the layered structures for the C-S-H samples that are modified by organic polymers. Scanning transmission X-ray microscopy (STXM) results further supports this observation. We also observed difference in the extent of C-S-H carbonation due to the presence of organic polymers. No calcite formed in the presence of HDTMA whereas formation of calcite was observed with C-S-H sample modified with PEG. We suggest that the difference in the carbonation reaction is possibly due to the ease of penetration and diffusion of the CO 2. This observation suggests that CO 2 reaction strongly depends on the presence of organic polymers and the types of organic polymers incorporated within the C-S-H structure. This is the first comprehensive study using STXM to quantitatively characterize the level of heterogeneity in cementitious materials at high spatial and spectral resolutions. The results from BET, XRD, ATR-FTIR, and STXM measurements are consistent and suggest that C-S-H layer structures are significantly modified due to the presence of organic polymers, and that the chemical composition and structural differences among the organic polymers determine the extent of the changes in the C-S-H nanostructures as well as the extent of carbonation reaction. © 2011 Springer Science+Business Media, LLC.

Olefination reactions of phosphorus-stabilized carbon nucleophiles.

Science.gov (United States)

Gu, Yonghong; Tian, Shi-Kai

2012-01-01

A range of phosphorus-stabilized carbon nucleophiles have been employed for alkene synthesis with high chemo-, regio-, and stereoselectivity. The Wittig, Horner-Wadsworth-Emmons, Horner-Wittig, and Evans-Akiba reactions utilize phosphonium-, phosphonate-, phosphine oxide-, and pentacoordinated phosphorane-stabilized carbanions as nucleophiles, respectively, to undergo olefination with aldehydes or ketones, and each of these transformations has its own advantages and limitations. Modifying the structures of these nucleophiles along with optimizing reaction conditions results in the formation of a wide variety of polysubstituted alkenes in a highly stereoselective manner. The olefination of imines with phosphonium ylides has recently emerged as a useful approach to tune the stereoselectivity for alkene synthesis. This review focuses on recent advances in the stereoselective olefination of phosphorus-stabilized carbon nucleophiles.

Preliminary assessment of a method utilizing carbon dioxide and steelmaking slags to produce precipitated calcium carbonate

International Nuclear Information System (INIS)

Eloneva, Sanni; Said, Arshe; Fogelholm, Carl-Johan; Zevenhoven, Ron

2012-01-01

Highlights: ► An NH 4 -salt-based method utilizes CO 2 and steelmaking slags to produce pure CaCO 3 . ► It was determined if its economic potential warrants moving forward. ► Despite small solvent losses, the method was found to have economical potential. ► The method has significant CO 2 emissions reduction potential. ► Scaling up the reactor will allow for a more detailed design for the process. -- Abstract: One of the options that can contribute to the reduction of carbon dioxide emissions for climate change mitigation is the so-called CO 2 sequestration by mineral carbonation, or CO 2 mineral sequestration. Steel manufacturing could benefit from this option by utilizing its own by-products, i.e. steelmaking slags to combine with CO 2 . We have recently studied a method, where aqueous solution of ammonium salt (e.g. ammonium acetate, ammonium nitrate and ammonium chloride) is used to extract calcium selectively from the steel converter slag, followed by precipitation of pure calcium carbonate by bubbling CO 2 through the produced solution. The ammonium salt solution is recovered and re-used. The purpose of this research was to determine if the economic potential of the method warrants moving forward to large-scale application. Despite the small solvent losses, the method was found to have economical potential. In addition, it has significant CO 2 emission reduction potential as well. Scaling up the reactor from the small laboratory scale will allow more detailed design for the process to be made followed by a full economical evaluation including all of the important operational and capital investment costs.

Characterization of materials eliciting foreign body reaction in stapled human gastrointestinal anastomoses.

Science.gov (United States)

Lim, C B B; Goldin, R D; Darzi, A; Hanna, G B

2008-08-01

Staples are made of titanium, which elicits minimal tissue reaction. The authors have encountered foreign body reaction associated with stapled human gastrointestinal anastomoses, although the literature has no reports of this. The aim of this study was to identify the refractile foreign materials causing this reaction. Histological sections were taken from 14 gastrointestinal specimens from patients with a history of a stapled anastomosis within the specimen excised. These were reviewed by light and polarization microscopy. Scanning electron microscopy and energy dispersive X-ray analysis were carried out on these sections, staples and stapler cartridges used for gastrointestinal surgery. Foreign bodies rich in fluorine were found in three patients, and those rich in carbon in 12. Other elements identified included oxygen, calcium, sodium, potassium, magnesium, aluminium and silicon. One specimen was found to contain titanium with no surrounding foreign body reaction. Stapler cartridges contained carbon, oxygen, fluorine, calcium, sodium, potassium, magnesium, aluminium, silicon and traces of titanium. Staples were composed of pure titanium with some fibrous material on the surface containing elements found in stapler cartridges. The presence of foreign body reaction was confirmed in stapled human gastrointestinal anastomoses. The source of refractile materials eliciting this reaction was the stapler cartridges. (c) 2008 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.

Adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium carbonate sand.

Science.gov (United States)

Park, Yoonjee C; Paulsen, Jeffrey; Nap, Rikkert J; Whitaker, Ragnhild D; Mathiyazhagan, Vidhya; Song, Yi-Qiao; Hürlimann, Martin; Szleifer, Igal; Wong, Joyce Y

2014-01-28

Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium carbonate because of differences in the mineral surface properties. NP adsorption increased with increasing salt concentration: this trend was qualitatively explained by molecular theory, as was the role of the PEG grafting in preventing NPs adsorption. Quantitative disagreement between the theoretical predictions and the data was due to NP aggregation, especially at high salt concentration and in the presence of calcium carbonate. Upon aggregation, NP concentrations as determined by NMR T2 were initially overestimated and subsequently corrected using the relaxation rate 1/T2, which is a function of aggregate size and fractal dimension of the aggregate. Our experimental validation of the theoretical predictions of NP adsorption to minerals in the absence of aggregation at various pH and salt conditions demonstrates that molecular theory can be used to determine interactions between NPs and relevant reservoir surfaces. Importantly, this integrated experimental and

Scaling of Calcium Carbonate at Heated Surfaces in a Continuous System

OpenAIRE

Nergaard, Margrethe

2011-01-01

Scaling is the precipitation of a mineral layer on a surface. Sparingly soluble salts with inverse solubility, which calcium carbonate exhibits, will prefer precipitation at heated surfaces, making heat exchangers a target for scale formation. A continuous setup was used to study scale formation, the nature of the scale formed and scaling rate. An internally heated U-shaped tube was inserted into a continuously stirred tank, giving the same conditions for all scaling points. The experimental ...

Kinetic Modeling of the Reaction Rate for Quartz and Carbon Pellet

Science.gov (United States)

Li, Fei; Tangstad, Merete

2018-04-01

Kinetic modeling of quartz and carbon pellet at temperatures of 1898 K, 1923 K, and 1948 K (1625 °C, 1650 °C, and 1675 °C) was investigated in this study. The carbon materials used were charcoal, coke, coal, and preheated coal. The overall SiC producing reaction can be described by the reaction SiO2 + 3C = SiC + 2CO. In the SiC-producing step, the reaction rate of quartz and carbon pellet can be expressed as {d{ pct}}/dt = ( {1 - 0.40 × X_{fix - C}^{ - 0.86} × FC × {pct}} ) × A × \\exp ( { - E/{{RT}}} ) The carbon factor F C was used to describe the influence of different carbon materials that effect the gas-solid interface reaction. For charcoal, coke, coal, and preheated coal, the F C values were 0.83, 0.80, 0.94, and 0.83, respectively. The pre-exponential factor A values for the preceding four carbon materials were 1.06 × 1016 min-1, 4.21 × 1015 min-1, 3.85 × 109 min-1, and 1.00 × 1025 min-1, respectively. The activation energies E for the SiC-producing step were 570, 563, 336, and 913 kJ/mole for charcoal, coke, coal, and preheated coal pellets, respectively.

Food-grade Pickering stabilisation of foams by in situ hydrophobisation of calcium carbonate particles

NARCIS (Netherlands)

Binks, Bernard P.; Muijlwijk, K.; Koman, Henriëtte; Poortinga, A.T.

2017-01-01

The aim of this study was to investigate the possibility of stabilising foam bubbles in water by adsorption of calcium carbonate (CaCO3) particles. Because CaCO3 is hydrophilic and not surface-active, particles were hydrophobised in situ with several emulsifiers. The used emulsifiers were food-grade

Food-grade pickering stabilisation of foams by in situ hydrophobisation of calcium carbonate particles

NARCIS (Netherlands)

Binks, B.P.; Muijlwijk, K.; Koman, H.; Poortinga, A.T.

2017-01-01

The aim of this study was to investigate the possibility of stabilising foam bubbles in water by adsorption of calcium carbonate (CaCO3) particles. Because CaCO3 is hydrophilic and not surface-active, particles were hydrophobised in situ with several emulsifiers. The used emulsifiers were food-grade

Fischer-Tropsch diesel production over calcium-promoted Co/alumina catalyst: Effect of reaction conditions

Energy Technology Data Exchange (ETDEWEB)

A.R. de la Osa; A. De Lucas; A. Romero; J.L. Valverde; P. Sanchez [University of Castilla-La Mancha, Ciudad Real (Spain). Chemical Engineering Department

2011-05-15

The effects of reaction conditions on the Fischer-Tropsch activity and product distribution of an alkali-earth metal promoted cobalt based catalyst were studied. The influence of the promoter on the reducibility and cobalt particle size was studied by different techniques, including N{sub 2} adsorption, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption and acid-base titrations. Experiments were carried out on a bench-scale fixed bed reactor and catalysts were prepared by incipient wetness impregnation. It was observed that addition of a small amount of calcium oxide as a promoter (0.6 wt.%) improved the cobalt oxide reducibility and reduced the formation of cobalt-aluminate species. A positive correlation between basicity and particle size was observed. In terms of FTS results, CO conversion and C{sub 5}{sup +} selectivity were found to be enhanced by the addition of this promoter. It was important to note that the addition of calcium shifted the distribution to mainly C{sub 16}-C{sub 18} hydrocarbons fraction, which could be greatly considered for a diesel formulation. Furthermore, the variation of the reaction conditions seemed to influence product distribution in a lesser extent than unpromoted catalyst. Also, a displacement of hydrocarbon distribution to higher molecular weight with decreasing space velocity and temperature was observed. Moreover, the addition of calcium to the cobalt based catalyst was found to greatly maintain selectivity to C{sub 5}{sup +} for a wide range of H{sub 2}/CO molar ratios. 60 refs., 10 figs., 5 tabs.

Reaction of calcium chloride with alkali metal chlorides in melts

International Nuclear Information System (INIS)

Savin, V.D.; Mikhajlova, N.P.

1984-01-01

Thermochemical characteristics of CaCl 2 reaction with sodium, potassium, rubidium and cesium chlorides in melts at 890 deg C are determined. The values of formation enthalpies of infinitely diluted by CaCl 2 solutions (ΔH) in the chloride row increase from -22 in NaCl to -47 kJ/mol of CaCl 2 in CsCl. With increasing the concentration of calcium chloride in the solution the ΔH values decrease. The regularities of separation from the solution of the CaCl 2 -CsCl system at 890 deg C of the CaCl 2 x CsCl in solid are studied. Formation enthalpies under the given conditions constitutes -70+-3 kJ/mol

Reaction of yttrium polonides with carbon dioxide

International Nuclear Information System (INIS)

Abakumov, A.S.; Khokhlov, A.D.; Reznikova, N.F.

1986-01-01

It has been proved that heating of yttrium and tantalum in carbon dioxide to 500 and 800 0 C alters the gas phase composition, causing formation of carbon monoxide and reduction of oxygen content. A study of the thermal stability of yttrium polonides in carbon dioxide showed that yttrium sesqui- and monopolonides decompose at 400-430 0 C. The temperature dependence of the vapor pressure of polonium obtained upon decomposition of the referred polonides has been determined in a carbon dioxide environment radiotensometrically. The enthalpy of the process calculated from this dependence is close to the enthalpy of vaporization of elemental polonium in vacuo. The mechanism of the reactions has been suggested

Effect of calcium supplements on osteoporosis by using nuclear analytical techniques

International Nuclear Information System (INIS)

Sumin Hu; Xueying Mao; Hong Ouyang

2004-01-01

Neutron activation analysis (NAA) and dual energy X-ray absorptiometry (DEXA) have been used to study the effects of different calcium supplements on osteoporosis, including calcium carbonate, calcium threonate, calcium gluconate, calcium lactate, calcium acetate and a traditional Chinese medicine. Animal test results showed that calcium carbonate, calcium gluconate, calcium acetate and the Chinese medicine notably increased osteoporotic rat's femoral bone mineral density (BMD). Also, calcium carbonate, calcium acetate and the Chinese medicine significantly increased osteoporotic rat's vertebral BMD. But calcium L-threonate and calcium lactate had no such effects. Calcium gluconate, calcium acetate and the Chinese medicine improved the bone mechanical intensity of osteoporotic rats. The results of NAA showed that the loss of elements in spongy bones was more seriously than that in compact bone and was difficult to be improved. (author)

In situ synthesis and modification of calcium carbonate nanoparticles via a bobbling method

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

Modified calcium carbonate (CaCO3) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers were investigated by measuring the active ratio, whiteness and the contact angle. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products. A preliminary reaction mechanism was discussed. According to the results, the active ratio of CaCO3 modified by ODP was ca. 99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%. The contact angle was 122.25° for the CaCO3 modified in the presence of sodium stearate, ODP and OA. When modified CaCO3 was filled into PVC, the mechanical properties of products were improved greatly such as rupture intensity, pull intensity and fuse temperature. The compatibility and affinity between the modified CaCO3 nanoparticles and the organic matrixes were greatly improved.

In situ synthesis and modification of calcium carbonate nanoparticles via a bobbling method

Institute of Scientific and Technical Information of China (English)

ZHAO LiNa; FENG JingDong; WANG ZiChen

2009-01-01

Modified calcium carbonate (CaCO3) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method.The modifiers,such as sodium stearate,octadecyl dihydrogen phosphate (ODP) and oleic acid (OA),were used to obtain hydrophobic nanoparticles.The different modification effects of the modifiers were investigated by measuring the active ratio,whiteness and the contact angle.Moreover,transmission electron microscopy (TEM),X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products.A preliminary reaction mechanism was discussed.According to the results,the active ratio of CaCO3 modified by ODP was ca.99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%.The contact angle was 122.25° for the CaCO3 modified in the presence of sodium stearate,ODP and OA.When modified CaCO3 was filled into PVC,the mechanical properties of products were improved greatly such as rupture intensity,pull intensity and fuse temperature.The compatibility and affinity between the modified CaCO3 nanoparticles and the organic matrixes were greatly improved.

Studies in the reaction dynamics of beam-gas chemiluminescent reactions

International Nuclear Information System (INIS)

Prisant, M.G.

1984-01-01

This thesis develops techniques for the analysis and interpretation of data obtained from beam-gas chemiluminescence experiments. These techniques are applied to experimental studies of atom transfer reactions of the type A + BC → AB + C. A procedure is developed for determining the product rotational alignment in the center-of-mass frame from polarization measurements of chemiluminescent atom-diatom exchange reactions under beam-gas conditions. Knowledge of a vector property of a reaction, such as product alignment, provides information on the disposition of angular momentum by a chemical reaction. Fluorescence polarization and hence product alignment are measured for two prototype reactions. The reaction of metastable calcium atoms with hydrogen-chloride gas yields highly aligned calcium-chloride product which exhibits little variation of alignment with vibrational state. The reaction of ground-state calcium with fluorine gas yields moderately aligned product which shows strong variation of alignment with vibration. A multi-surface direct-interaction model is developed to interpret product alignment and population data. The predictions of this model for the reaction of calcium with fluorine show reasonable agreement with experiment

[Comparison of the therapeutic effect on skeletal fluorosis and impact on urine fluoride value among fire needle therapy, electroacupuncture and calcium carbonate D3].

Science.gov (United States)

Wang, Tong; Yang, Xu-Guang; Wu, Zhong-Chao; Zhou, Jin-Cao; Chen, Zhong-Jie; Hu, Jing; Jiao, Yue; Zhao, Xiao-Guang

2014-03-01

To observe the impacts on skeletal fluorosis pain, joint motor dysfunction and urine fluoride excretion in the treatment with fire needle therapy, electroacupuncture and calcium carbonate D3. The randomized controlled trial was adopted. Ninety-five patients were randomized into a fire needle group (31 cases), an electroacupuncture group (33 cases) and a calcium carbonate D3 group (31 cases). In the fire needle group and the electroacupuncture group, Ashi points, Dazhui (GV 14), Geshu (BL 17), Quchi (LI 11), Hegu (LI 4), Xuehai (SP 10) points were selected and stimulated with fire needle and electroacupuncture separately, three times a week. In the calcium carbonate D3 group, calcium carbonate D3 tablets was prescribed for oral administration, 600 mg each time, twice a day. The duration of treatment was 2 months in the electroacupuncture group and calcium carbonate D3 group and 1 month in the fire needle group. VAS score, the range of motion (ROM) and urine fluoride value were compared before and after treatment in the patients of the three groups. After treatment, VAS value and ROM were improved significantly in the patients of the three groups (all P 0.05). After treatment, the urine fluoride value was increased significantly in the fire needle group [(7.89 +/- 3.61) mg/L vs (9.81 +/- 4.17) mg/L, P electroacupuncture group [(7.53 +/- 3.46) mg/L vs (8.97 +/- 4.21) mg/L, P 0.05). The fire needle therapy, electroacupuncture and calcium carbonate D3 all have the clinical value in the prevention and treatment of skeletal fluorosis and the difference in the therapeutic effect has not been discovered among them yet at present. But it has been found that the fire needle therapy and electroacupuncture display the active significance in the promotion of urine fluoride excretion.

Important role of calcium chloride in preventing carbon monoxide generation during desflurane degradation with alkali hydroxide-free carbon dioxide absorbents.

Science.gov (United States)

Ando, Takahiro; Mori, Atsushi; Ito, Rie; Nishiwaki, Kimitoshi

2017-12-01

We investigated whether calcium chloride (CaCl 2 ), a supplementary additive in carbon dioxide (CO 2 ) absorbents, could affect carbon monoxide (CO) production caused by desflurane degradation, using a Japanese alkali-free CO 2 absorbent Yabashi Lime ® -f (YL-f), its CaCl 2 -free and 1% CaCl 2 -added derivatives, and other commercially available alkali-free absorbents with or without CaCl 2 . The reaction between 1 L of desflurane gas (3-10%) and 20 g of desiccated specimen was performed in an artificial closed-circuit anesthesia system for 3 min at 20 or 40 °C. The CO concentration was measured using a gas chromatograph equipped with a semiconductor sensor detector. The systems were validated by detecting dose-dependent CO production with an alkali hydroxide-containing CO 2 absorbent, Sodasorb ® . Compared with YL-f, the CaCl 2 -free derivative caused the production of significantly more CO, while the 1% CaCl 2 -added derivative caused the production of a comparable amount of CO. These phenomena were confirmed using commercially available absorbents AMSORB ® PLUS, an alkali-free absorbent with CaCl 2 , and LoFloSorb™, an alkali-free absorbent without CaCl 2 . These results suggest that CaCl 2 plays an important role in preventing CO generation caused by desflurane degradation with alkali hydroxide-free CO 2 absorbents like YL-f.

On reaction of titanium polonides with carbon dioxide

International Nuclear Information System (INIS)

Abakumov, A.S.; Malyshev, M.L.; Reznikova, N.F.

1986-01-01

The reaction between titanium polonides and carbon dioxide has been studied by comparing titanium polonide thermal resistance in vacuum and in carbon dioxide. The investigation has shown that titanium mono- and semipolonides fail at temperatures below 350 deg C. Temperature dependence of polonium vapor pressure prepared at failure of the given polonides is determined by the radiotensiometry in carbon dioxide. Enthalpy calculated for this dependence is close to the enthalpy of elementary polonium evaporation in vacuum

Reactions of carbon radicals generated by 1,5-transposition of reactive centers

Directory of Open Access Journals (Sweden)

ZIVORAD CEKOVIC

2005-03-01

Full Text Available Radical intermediates can undergo specific reactions, such as intramolecular rearrangements, i.e., the transpositions of radical centers, which are not known in classical ionic organic reactions. 1,5-Transposition of a radical center to a non-activated carbon atom are of great synthetic importance. It can be successfully applied for the introduction of different functional groups (oxygen, nitrogen, sulfur, halogens onto a carbon atom remote from the present functional group. In addition to functionalization of a remote non-activated carbon atom, the formation of new C-C bonds on the d-carbon atom have also been achieved. 1,5-Transposition of the radical centers takes place from alkoxyl, aminyl and carbon radicals to a remote carbon atom. Relocation of the radical centers preferentially involves 1,5-transfer of a hydrogen atom, although migrations of some other groups are known. The reactions of the carbon radical generated by 1,5-relocation of the radical center are presented and their synthetic applications are reviewed.

Absorbability of calcium from calcium-bound phosphoryl oligosaccharides in comparison with that from various calcium compounds in the rat ligated jejunum loop.

Science.gov (United States)

To-o, Kenji; Kamasaka, Hiroshi; Nishimura, Takahisa; Kuriki, Takashi; Saeki, Shigeru; Nakabou, Yukihiro

2003-08-01

Calcium-bound phosphoryl oligosaccharides (POs-Ca) were prepared from potato starch. Their solubility and in situ absorbability as a calcium source were investigated by comparing with the soluble calcium compounds, calcium chloride and calcium lactate, or insoluble calcium compounds, calcium carbonate and dibasic calcium phosphate. The solubility of POs-Ca was as high as that of calcium chloride and about 3-fold higher than that of calcium lactate. An in situ experiment showed that the intestinal calcium absorption rate of POs-Ca was almost comparable with that of the soluble calcium compounds, and was significantly higher (pcalcium groups. Moreover, the total absorption rate of a 1:1 mixture of the calcium from POs-Ca and a whey mineral complex (WMC) was significantly higher (psoluble calcium source with relatively high absorption in the intestinal tract.

Surface Modification and Planar Defects of Calcium Carbonates by Magnetic Water Treatment

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Yeh MS

2010-01-01

Full Text Available Abstract Powdery calcium carbonates, predominantly calcite and aragonite, with planar defects and cation–anion mixed surfaces as deposited on low-carbon steel by magnetic water treatment (MWT were characterized by X-ray diffraction, electron microscopy, and vibration spectroscopy. Calcite were found to form faceted nanoparticles having 3x ( commensurate superstructure and with well-developed { } and { } surfaces to exhibit preferred orientations. Aragonite occurred as laths having 3x ( commensurate superstructure and with well-developed ( surface extending along [100] direction up to micrometers in length. The (hkil-specific coalescence of calcite and rapid lath growth of aragonite under the combined effects of Lorentz force and a precondensation event account for a beneficial larger particulate/colony size for the removal of the carbonate scale from the steel substrate. The coexisting magnetite particles have well-developed {011} surfaces regardless of MWT.

Peptoid nanosheets as soluble, two-dimensional templates for calcium carbonate mineralization.

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Jun, Joo Myung V; Altoe, M Virginia P; Aloni, Shaul; Zuckermann, Ronald N

2015-06-25

Nacre-mimetic materials are of great interest, but difficult to synthesize, because they require the ordering of organic and inorganic materials on several length scales. Here we introduce peptoid nanosheets as a versatile two-dimensional platform to develop nacre mimetic materials. Free-floating zwitterionic nanosheets were mineralized with thin films of amorphous calcium carbonate (of 2-20 nm thickness) on their surface to produce planar nacre synthons. These can serve as tunable building blocks to produce layered brick and mortar nanoarchitectures.

Application of Box-Behnken design to prepare gentamicin-loaded calcium carbonate nanoparticles.

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Maleki Dizaj, Solmaz; Lotfipour, Farzaneh; Barzegar-Jalali, Mohammad; Zarrintan, Mohammad-Hossein; Adibkia, Khosro

2016-09-01

The aim of this research was to prepare and optimize calcium carbonate (CaCO3) nanoparticles as carriers for gentamicin sulfate. A chemical precipitation method was used to prepare the gentamicin sulfate-loaded CaCO3 nanoparticles. A 3-factor, 3-level Box-Behnken design was used for the optimization procedure, with the molar ratio of CaCl2: Na2CO3 (X1), the concentration of drug (X2), and the speed of homogenization (X3) as the independent variables. The particle size and entrapment efficiency were considered as response variables. Mathematical equations and response surface plots were used, along with the counter plots, to relate the dependent and independent variables. The results indicated that the speed of homogenization was the main variable contributing to particle size and entrapment efficiency. The combined effect of all three independent variables was also evaluated. Using the response optimization design, the optimized Xl-X3 levels were predicted. An optimized formulation was then prepared according to these levels, resulting in a particle size of 80.23 nm and an entrapment efficiency of 30.80%. It was concluded that the chemical precipitation technique, together with the Box-Behnken experimental design methodology, could be successfully used to optimize the formulation of drug-incorporated calcium carbonate nanoparticles.

Enhanced interfacial properties of carbon fiber composites via aryl diazonium reaction “on water”

International Nuclear Information System (INIS)

Wang, Yuwei; Meng, Linghui; Fan, Liquan; Ma, Lichun; Qi, Meiwei; Yu, Jiali; Huang, Yudong

2014-01-01

Highlights: • Carbon fibers are grafted with phenyl amine group via aryl diazonium reaction. • Interfacial shear strength of the carbon fibers increases by 73%. • Tensile strength of the carbon fibers does not decrease distinctly. • Using water as the reaction medium can avoid pollution from organic solvents. • Grafting via aryl diazonium reaction in one step can improve modification efficiency. - Abstract: Polyacrylonitrile-based carbon fibers were functionalized with phenyl amine group via aryl diazonium reaction “on water” to improve their interfacial bonding with resin matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize ordered degree, functional groups, chemical states and morphology of carbon fiber surface, respectively. The results showed that phenyl amine groups were grafted on the fiber surface successfully. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 73%, while the tensile strength was down very slightly. Hence aryl diazonium reaction “on water” could be a facile green platform to functionalize carbon fibers for many interesting applications

Enhanced interfacial properties of carbon fiber composites via aryl diazonium reaction “on water”

Energy Technology Data Exchange (ETDEWEB)

Wang, Yuwei [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China); Meng, Linghui [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Fan, Liquan [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China); Ma, Lichun; Qi, Meiwei; Yu, Jiali [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Huang, Yudong, E-mail: ydhuang.hit1@yahoo.com.cn [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China)

2014-10-15

Highlights: • Carbon fibers are grafted with phenyl amine group via aryl diazonium reaction. • Interfacial shear strength of the carbon fibers increases by 73%. • Tensile strength of the carbon fibers does not decrease distinctly. • Using water as the reaction medium can avoid pollution from organic solvents. • Grafting via aryl diazonium reaction in one step can improve modification efficiency. - Abstract: Polyacrylonitrile-based carbon fibers were functionalized with phenyl amine group via aryl diazonium reaction “on water” to improve their interfacial bonding with resin matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize ordered degree, functional groups, chemical states and morphology of carbon fiber surface, respectively. The results showed that phenyl amine groups were grafted on the fiber surface successfully. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 73%, while the tensile strength was down very slightly. Hence aryl diazonium reaction “on water” could be a facile green platform to functionalize carbon fibers for many interesting applications.

Kerogen-mineral reactions at raised temperatures in the presence of water

Energy Technology Data Exchange (ETDEWEB)

Eglinton, T I; Rowland, S J; Curtis, C D; Douglas, A G

1986-01-01

Kerogen has been artificially matured under hydrous pyrolysis conditions in the presence of various minerals in order to investigate the influence of the latter on the organic products. In addition to three clay minerals (montmorillonite, illite, kaolinite), calcium carbonate and limonite were also employed as inorganic substrates. Kerogen (Type II) isolated from the Kimmeridge Blackstone band was heated in the presence of water and a 20-fold excess of mineral phase at two different temperatures (280 and 330/sup 0/C) for 72 hr. Control experiments were also carried out using kerogen and water only and kerogen under anhydrous conditions. This preliminary study describes the bulk composition of the pyrolysates with detailed analyses of the aliphatic hydrocarbon distributions being provided by gas chromatography and combined gas chromatography-mass spectrometry. In the 280/sup 0/C experiments, considerably more organic-soluble pyrolysate (15% by weight of original kerogen) was produced when calcium carbonate was the inorganic phase. At 330/sup 0/C, all samples generated much greater amounts of organic-soluble products with calcium carbonate again producing a large yield (approx. 40% wt/wt). Biomarker epimerization reactions have also proceeded further in the 330/sup 0/C pyrolysate formed in the presence of calcium carbonate than with other inorganic phases. Implications of these and other observations are discussed.

Carbonate-containing hydroxyapatite derived from calcium tripolyphosphate gel with urea.

Science.gov (United States)

Mizutani, Y; Hattori, M; Okuyama, M; Kasuga, T; Nogami, M

2005-08-01

Carbonate containing hydroxyapatite (CO3HAp) is one of the candidate materials as a bioresorbable bone substitute. In the present work, CO3HAp was efficiently prepared by a hydrothermal treatment of calcium tripolyphosphate gel with urea at 140 degrees C for 24 h. Chemical potential plots of the CO3HAp for estimation of its dissolution behavior suggested that the CO3HAp is more soluble than hydroxyapatite (HAp) and is as soluble as octacalcium phosphate (OCP) and/or beta -tricalcium phosphate (TCP). This material is expected to be applied to bioresorbable materials such as bone fillers.

Evidence of calcium carbonates in coastal (Talos Dome and Ross Sea area) East Antarctica snow and firn: Environmental and climatic implications

Science.gov (United States)

Sala, M.; Delmonte, B.; Frezzotti, M.; Proposito, M.; Scarchilli, C.; Maggi, V.; Artioli, G.; Dapiaggi, M.; Marino, F.; Ricci, P. C.; De Giudici, G.

2008-07-01

Micrometre-sized aeolian dust particles stored in Antarctic firn and ice layers are a useful tool for reconstructing climate and environmental changes in the past. The mineral content, particle concentration and chemical composition of modern dust in firn cores from the peripherycal dome (Talos Dome) and coastal area of East Antarctica (Ross Sea sector) were investigated. During analyses there was a considerable decrease in microparticle concentrations within a few hours of ice sample melting, accompanied by a systematic increase in the concentration of calcium ions (Ca 2+) in solution. Based on mineralogical phase analyses, which reveal the presence of anhydrous and hydrous calcium carbonates such as calcite (CaCO 3), monohydrocalcite (CaCO 3·H 2O) and ikaite (CaCO 3·6H 2O, hexahydrate calcium carbonate), the observed variations in concentrations are ascribed to the partial dissolution of the carbonate content of samples. Soluble carbonate compounds are thus primary aerosols included into the samples along with insoluble aluminosilicate minerals. We hypothesize hydrous carbonates may derive from the sea ice surface, where ikaite typically forms at the early stages of sea ice formation. Back trajectory calculations show that favourable events for air mass advection from the sea ice surface to Talos Dome are rare but likely to occur.

Electrochemical characterization of calcium cobaltite based porous electrodes

International Nuclear Information System (INIS)

Fulgencio, E.B.G.A.; Vasconcelos, K.; Silva, R.M.; Melo, P.; Caetano, A.A.; Campos, L.F.A.; Dutra, R.P.S.; Macedo, D.A.

2016-01-01

Materials based on alkali metal oxides and alkaline earth metal have shown high technological interest in recent years. Among these materials, calcium and cobalt oxide composition Ca_3Co_4O_9 (C349) has emerged as thermoelectric material and, more recently, as cathode for solid oxide fuel cell (SOFC). In this study, C349 powder was obtained by solid state reaction of a mixture containing cobalt oxide and calcium carbonate from shellfish shells (CaCO_3 ∼ 98%), previously calcined at 550° C. Symmetrical cells (cathode / substrate / cathode) were prepared by screen printing of C349 electrodes in gadolinium-doped ceria substrates. The characterization by electrochemical impedance spectroscopy revealed that the C349 obtained in this work has an area specific resistance compatible with electrodes obtained by chemical routes (from literature). (author)

Alkali Silica Reaction In The Presence Of Metakaolin - The Significant Role of Calcium Hydroxide

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Zapała-Sławeta, Justyna

2017-10-01

Reducing the internal corrosion, which is the result of reactions between alkalis and reactive aggregates is especially important in ensuring durability properties of concrete. One of the methods of inhibiting the reaction is using some mineral additives which have pozzolanic properties. This paper presents the efficacy of high-reactivity metakaolin in reducing expansion due to alkali-silica reaction. It was demonstrated that metakaolin in the amount from 5% to 20% by mass of Portland cement reduce linear expansion of mortar bars with opal aggregate. Nevertheless, the safe expansion level in the specimens, classified as non-destructive to concrete, was recorded for the mortars prepared with 20% addition of metakaolin. Depletion of free calcium hydroxide content was considered as one of the most beneficial effects of metakaolin in controlling alkali silica reaction. Based on thermogravimetric analysis (TGA) performed on mortar bars with and without metakaolin the differences in portlandite content were determined. Microstructural observation of the specimens containing metakaolin indicated the presence of a reaction products but fewer in number than those forming in the mortars without mineral additives.

Multivariate regression models for the simultaneous quantitative analysis of calcium and magnesium carbonates and magnesium oxide through drifts data

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Marder Luciano

2006-01-01

Full Text Available In the present work multivariate regression models were developed for the quantitative analysis of ternary systems using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS to determine the concentration in weight of calcium carbonate, magnesium carbonate and magnesium oxide. Nineteen spectra of standard samples previously defined in ternary diagram by mixture design were prepared and mid-infrared diffuse reflectance spectra were recorded. The partial least squares (PLS regression method was applied to the model. The spectra set was preprocessed by either mean-centered and variance-scaled (model 2 or mean-centered only (model 1. The results based on the prediction performance of the external validation set expressed by RMSEP (root mean square error of prediction demonstrated that it is possible to develop good models to simultaneously determine calcium carbonate, magnesium carbonate and magnesium oxide content in powdered samples that can be used in the study of the thermal decomposition of dolomite rocks.

Biomimetic synthesis of calcium carbonate with different morphologies and polymorphs in the presence of bovine serum albumin and soluble starch.

Science.gov (United States)

Liu, Yuxi; Chen, Yuping; Huang, Xuechen; Wu, Gang

2017-10-01

Calcium carbonate has been synthesized by the reaction of Na 2 CO 3 and CaCl 2 in the presence of bovine serum albumin (BSA) and soluble starch. Effects of various bovine serum albumin (BSA) and soluble starch on the polymorph and morphology of CaCO 3 crystals were investigated. Crystallization of vaterite is favored in the presence of BSA and soluble starch, respectively, while calcite is favored in the presence of a mixture of BSA and soluble starch. The morphologies of CaCO 3 particles in the presence of mixture of BSA and soluble starch are mainly rod-like, suggesting that the BSA, soluble and their assemblies play key roles in stabilizing and directing the CaCO 3 crystal growth. Copyright © 2017. Published by Elsevier B.V.

Effect of pH and phosphate on calcium carbonate polymorphs precipitated at near-freezing temperature

NARCIS (Netherlands)

Hu, Yu-Bin; Wolthers, Mariëtte; Wolf-Gladrow, Dieter A.; Nehrke, Gernot

2015-01-01

The effects of pH and phosphate on the precipitation of calcium carbonate polymorphs from aqueous solution were investigated. Experiments were carried out at near-freezing temperature and two different pH conditions (pH 13.4 and 9.0). At each pH condition, solutions having different concentrations

Climatically driven loss of calcium in steppe soil as a sink for atmospheric carbon

Science.gov (United States)

A.G. Lapenis; G.B. Lawrence; S.W. Bailey; B.F. Aparin; A.I. Shiklomanov; N.A. Speranskaya; M.S. Torn; M. Calef

2008-01-01

During the last several thousand years the semi-arid, cold climate of the Russian steppe formed highly fertile soils rich in organic carbon and calcium (classified as Chernozems in the Russian system). Analysis of archived soil samples collected in Kemannaya Steppe Preserve in 1920, 1947, 1970, and fresh samples collected in 1998 indicated that the native steppe...

21 CFR 184.1207 - Calcium lactate.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium lactate. 184.1207 Section 184.1207 Food and... Substances Affirmed as GRAS § 184.1207 Calcium lactate. (a) Calcium lactate (C6H10CaO6.xH2O, where x is any... calcium carbonate or calcium hydroxide. (b) The ingredient meets the specifications of the Food Chemicals...

Selective free radical reactions using supercritical carbon dioxide.

Science.gov (United States)

Cormier, Philip J; Clarke, Ryan M; McFadden, Ryan M L; Ghandi, Khashayar

2014-02-12

We report herein a means to modify the reactivity of alkenes, and particularly to modify their selectivity toward reactions with nonpolar reactants (e.g., nonpolar free radicals) in supercritical carbon dioxide near the critical point. Rate constants for free radical addition of the light hydrogen isotope muonium to ethylene, vinylidene fluoride, and vinylidene chloride in supercritical carbon dioxide are compared over a range of pressures and temperatures. Near carbon dioxide's critical point, the addition to ethylene exhibits critical speeding up, while the halogenated analogues display critical slowing. This suggests that supercritical carbon dioxide as a solvent may be used to tune alkene chemistry in near-critical conditions.

Efficacy of desensitizing products containing 8% arginine and calcium carbonate for hypersensitivity relief in MIH-affected molars: an 8-week clinical study.

Science.gov (United States)

Bekes, Katrin; Heinzelmann, Karolin; Lettner, Stefan; Schaller, Hans-Günter

2017-09-01

The objective of this study was to compare the efficacy in reducing hypersensitivity in molar incisor hypomineralization (MIH)-affected molars immediately and over 8 weeks combining a single in-office application and a homed-based program with desensitizing products containing 8% arginine and calcium carbonate. Nineteen children with at least one MIH-affected molar with hypersensitivity were included. Hypersensitivity was assessed with an evaporative (air) stimulus and a tactile stimulus. Each child received a single in-office treatment with a desensitizing paste containing 8% arginine and calcium carbonate (elmex Sensitive Professional desensitizing paste), followed by 8 weeks of brushing twice daily with a desensitizing toothpaste containing 8% arginine, calcium carbonate with 1450 ppm fluoride (elmex Sensitive Professional toothpaste), using the elmex Sensitive Professional toothbrush. Additionally, the corresponding mouthwash (elmex Sensitive Professional mouthwash) was used. Clinical assessments were made at baseline, immediately after the in-office treatment and after 1, 2, 4 and 8 weeks of brushing twice daily. Fifty-six molars with an air blast hypersensitivity score of 2 or 3 (Schiff Cold Air Sensitivity Scale) were included. Application of the desensitizing paste decreased hypersensitivity significantly immediately and throughout the 8 weeks recalls (p MIH. This is the first study evaluating the desensitizing effect of a desensitizing paste containing 8% arginine and calcium carbonate in patients with MIH.

Rapid, high-temperature, field test method for evaluation of geothermal calcium carbonate scale inhibitors

Energy Technology Data Exchange (ETDEWEB)

Asperger, R.G.

1986-09-01

A new test method is described that allows the rapid field testing of calcium carbonate scale inhibitors at 500/sup 0/F (260/sup 0/C). The method evolved from use of a full-flow test loop on a well with a mass flow rate of about 1 x 10/sup 6/ lbm/hr (126 kg/s). It is a simple, effective way to evaluate the effectiveness of inhibitors under field conditions. Five commercial formulations were chosen for field evaluation on the basis of nonflowing, laboratory screening tests at 500/sup 0/F (260/sup 0/C). Four of these formulations from different suppliers controlled calcium carbonate scale deposition as measured by the test method. Two of these could dislodge recently deposited scale that had not age-hardened. Performance-profile diagrams, which were measured for these four effective inhibitors, show the concentration interrelationship between brine calcium and inhibitor concentrations at which the formulations will and will not stop scale formation in the test apparatus. With these diagrams, one formulation was chosen for testing on the full-flow brine line. The composition was tested for 6 weeks and showed a dramatic decrease in the scaling occurring at the flow-control valve. This scaling was about to force a shutdown of a major, long-term flow test being done for reservoir economic evaluations. The inhibitor stopped the scaling, and the test was performed without interruption.

Biomimetic synthesis of hollow calcium carbonate with the existence of the agar matrix and bovine serum albumin

Energy Technology Data Exchange (ETDEWEB)

Feng, Jianhua, E-mail: fjh2008@126.com; Wu, Gang; Qing, Chengsong

2016-01-01

Proteins play important roles in the process of biomineralization. Vaterite and calcite have been synthesized by the reaction of Na{sub 2}CO{sub 3} and CaCl{sub 2} in the bovine serum albumin (BSA) and agar system. The samples have been characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The shape of CaCO{sub 3} crystal has been analyzed by scanning electronic microscopy (SEM). The results show that calcite is a single product in the absence of BSA, but the product is a mixture of calcite and vaterite in the presence of BSA. The spheral shell of CaCO{sub 3} crystal was obtained when the concentration of BSA increased to 9.0 mg/mL. - Highlights: • Biomimetic synthesis of hollow calcium carbonate • Calcification mechanisms in the presence of both protein and polysaccharides • Biomineralization under the action of protein and polysaccharides.

Energy and economic considerations for ex-situ and aqueous mineral carbonation

Energy Technology Data Exchange (ETDEWEB)

O' Connor, William K.; Dahlin, David C.; Rush, G.E.; Gerdemann, Stephen J.; Penner, L.R.

2004-01-01

Due to the scale and breadth of carbon dioxide emissions, and speculation regarding their impact on global climate, sequestration of some portion of these emissions has been under increased study. A practical approach to carbon sequestration will likely include several options, which will be driven largely by the energy demand and economics of operation. Aqueous mineral carbonation of calcium and magnesium silicate minerals has been studied as one potential method to sequester carbon dioxide. Although these carbonation reactions are all thermodynamically favored, they occur at geologic rates of reaction. Laboratory studies have demonstrated that these rates of reaction are accelerated with increasing temperature, pressure, and particle surface area. Mineral-specific activation methods were identified, however, each of these techniques incurs energy as well as economic costs. An overview of the mineral availability, pretreatment options and energy demands, and process economics is provided.

Catalytic activity of calcium-based mixed metal oxides nanocatalysts in transesterification reaction of palm oil

Science.gov (United States)

Hassan, Noraakinah; Ismail, Kamariah Noor; Hamid, Ku Halim Ku; Hadi, Abdul

2017-12-01

Nowadays, biodiesel has become the forefront development as an alternative diesel fuel derived from biological sources such as oils of plant and fats. Presently, the conventional transesterification of vegetable oil to biodiesel gives rise to some technological problem. In this sense, heterogeneous nanocatalysts of calcium-based mixed metal oxides were synthesized through sol-gel method. It was found that significant increase of biodiesel yield, 91.75 % was obtained catalyzed by CaO-NbO2 from palm oil compared to pure CaO of 53.99 % under transesterification conditions (methanol/oil ratio 10:1, reaction time 3 h, catalyst concentration 4 wt%, reaction temperature 60 °C, and mixing speed of 600 rpm). The phase structure and crystallinity as well as the texture properties of the prepared catalysts were characterized by X-ray Diffraction (XRD) and the textural properties were characterized by N2 adsorption-desorption analysis. Sol-gel method has been known as versatile method in controlling the structural and chemical properties of the catalyst. Calcium-based mixed oxide synthesized from sol-gel method was found to exist as smaller crystallite size with high surface area.

Radioisotope 45Ca labeling four calcium chemical compounds and tracing calcium bioavailability

International Nuclear Information System (INIS)

Zheng Hui; Zhen Rong; Niu Huisheng; Li Huaifen

2004-01-01

Objective: To build up a new method of the radioisotope 45 Ca labeling four calcium chemical compounds, observe and tracing bioavailability change of calcium labeled with radioisotope 45 Ca. Methods: The calcium gluconate (Ca-Glu), calcium citrate (Ca-Cit), calcium carbonate (Ca-Car) and calcium L-threonate (Ca-Thr)were labeled by radioisotope 45 Ca. Four calcium chemical compounds of 45 Ca labeling were used of calcium content 200 mg/kg in the rats and measure the absorption content and bioavailability of calcium in tissue of heart, lever spleen, stomach, kidney, brain, intestine, whole blood, urine, faeces. Results: 1) Radioisotope 45 Ca labeling calcium chemical compound has high radio intensity, more steady standard curve and recover rate. 2) The absorption of organic calcium chemical compounds is higher than the inorganic calcium chemical compound in the study of calcium bioavailability. Conclusion: The method of tracing with radioisotope 45 Ca labeling calcium chemical compounds has the characteristic of the sensitive, objective, accurate and steady in the study of calcium bioavailability

Capillary Structured Suspensions from in Situ Hydrophobized Calcium Carbonate Particles Suspended in a Polar Liquid Media

NARCIS (Netherlands)

Dunstan, Timothy S.; Das, Anupam A.K.; Starck, Pierre; Stoyanov, Simeon D.; Paunov, Vesselin N.

2018-01-01

We demonstrate that capillary suspensions can be formed from hydrophilic calcium carbonate particles suspended in a polar continuous media and connected by capillary bridges formed of minute amounts of an immiscible secondary liquid phase. This was achieved in two different polar continuous phases,

Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests

Science.gov (United States)

Lapenis, Andrei Gennady; Lawrence, Gregory B.; Heim, Alexander; Zheng, Chengyang; Shortle, Walter

2013-01-01

Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

Potential effects of ocean acidification on Alaskan corals based on calcium carbonate mineralogy composition analysis (NCEI Accession 0157223)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains potential effects of ocean acidification on Alaskan corals based on calcium carbonate mineralogy composition analysis. Effects of...

Gas-Solid Reaction Properties of Fluorine Compounds and Solid Adsorbents for Off-Gas Treatment from Semiconductor Facility

Directory of Open Access Journals (Sweden)

Shinji Yasui

2012-01-01

Full Text Available We have been developing a new dry-type off-gas treatment system for recycling fluorine from perfluoro compounds present in off-gases from the semiconductor industry. The feature of this system is to adsorb the fluorine compounds in the exhaust gases from the decomposition furnace by using two types of solid adsorbents: the calcium carbonate in the upper layer adsorbs HF and converts it to CaF2, and the sodium bicarbonate in the lower layer adsorbs HF and SiF4 and converts them to Na2SiF6. This paper describes the fluorine compound adsorption properties of both the solid adsorbents—calcium carbonate and the sodium compound—for the optimal design of the fixation furnace. An analysis of the gas-solid reaction rate was performed from the experimental results of the breakthrough curve by using a fixed-bed reaction model, and the reaction rate constants and adsorption capacity were obtained for achieving an optimal process design.

Calcium hydroxide isotope effect in calcium isotope enrichment by ion exchange

International Nuclear Information System (INIS)

Jepson, B.E.; Shockey, G.C.

1984-01-01

The enrichment of calcium isotopes has been observed in ion-exchange chromatography with an aqueous phase of calcium hydroxide and a solid phase of sulfonic acid resin. The band front was exceedingly sharp as a result of the acid-base reaction occuring at the front of the band. Single-stage separation coefficients were found to be epsilon( 44 Ca/ 40 Ca) = 11 x 10 -4 and epsilon( 48 Ca/ 40 Ca) = 18 x 10 -4 . The maximum column separation factors achieved were 1.05 for calcium-44 and 1.09 for calcium-48 with the heavy isotopes enriching in the fluid phase. The calcium isotope effect between fully hydrated aqueous calcium ions and undissociated aqueous calcium hydroxide was estimated. For the calcium-44/40 isotope pair the separation coefficient was 13 x 10 -4 . 20 references, 2 figures

In vitro degradation and cell response of calcium carbonate composite ceramic in comparison with other synthetic bone substitute materials

International Nuclear Information System (INIS)

He, Fupo; Zhang, Jing; Yang, Fanwen; Zhu, Jixiang; Tian, Xiumei; Chen, Xiaoming

2015-01-01

The robust calcium carbonate composite ceramics (CC/PG) can be acquired by fast sintering calcium carbonate at a low temperature (650 °C) using a biocompatible, degradable phosphate-based glass (PG) as sintering agent. In the present study, the in vitro degradation and cell response of CC/PG were assessed and compared with 4 synthetic bone substitute materials, calcium carbonate ceramic (CC), PG, hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) ceramics. The degradation rates in decreasing order were as follows: PG, CC, CC/PG, β-TCP, and HA. The proliferation of rat bone mesenchymal stem cells (rMSCs) cultured on the CC/PG was comparable with that on CC and PG, but inferior to HA and β-TCP. The alkaline phosphatase (ALP) activity of rMSCs on CC/PG was lower than PG, comparable with β-TCP, but higher than HA. The rMSCs on CC/PG and PG had enhanced gene expression in specific osteogenic markers, respectively. Compared to HA and β-TCP, the rMSCs on the CC/PG expressed relatively lower level of collagen I and runt-related transcription factor 2, but showed more considerable expression of osteopontin. Although CC, PG, HA, and β-TCP possessed impressive performances in some specific aspects, they faced extant intrinsic drawbacks in either degradation rate or mechanical strength. Based on considerable compressive strength, moderate degradation rate, good cell response, and being free of obvious shortcoming, the CC/PG is promising as another choice for bone substitute materials. - Highlights: • A calcium carbonate composite ceramic (CC/PG) was acquired. • The in vitro degradation and cell response of CC/PG were compared to 4 materials. • The CC/PG showed moderate degradation rate. • The CC/PG exhibited good cell response. • The CC/PG was free of obvious drawback compared to other materials

High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

KAUST Repository

Stoltz, Brian

2010-06-14

The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

KAUST Repository

Stoltz, Brian; McDougal, Nolan; Virgil, Scott

2010-01-01

The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

Electromigration and Deposition of Micro-Scale Calcium Carbonate Structures with Controlled Morphology and Polymorphism

Science.gov (United States)

2013-04-01

precipitation of calcium carbonate in structured templates including microporous polycarbonate membranes and polyethylene foams. Para- meters...polyethylene foam). Microporous polycarbonate membranes and Medium-Density PolyEthylene (MDPE) foam specimens were used as the porous organic...voids in hardened concrete. DOI:10.1520/C624-06. West Conshohocken, PA: ASTM International . www.astm.org. Bersa, L., and M. Liu. 2007. A review on

Transformation and Crystallization Energetics of Synthetic and Biogenic Amorphous Calcium Carbonate

Energy Technology Data Exchange (ETDEWEB)

Radha, A. V. [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States); Forbes, Tori Z. [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States); Killian, Christopher E. [Univ. of Wisconsin, Madison, WI (United States); Gilbert, P.U.P.A [Univ. of Wisconsin, Madison, WI (United States); Navrotsky, Alexandra [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States)

2010-01-01

Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC→anhydrous ACC ~ biogenic anhydrous ACC→vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO₂ sequestration.

Insights into the importance of oxygen functional groups in carbon reactions with oxygen containing gases

International Nuclear Information System (INIS)

John Zhu, Max Lu

2005-01-01

The role of pore structure of carbon in carbon-related adsorptions and reactions has been extensively investigated. However the studies on the role of surface chemistry of carbon are limited. In this paper, we present the importance of oxygen functional groups in carbon reactions with oxygen-containing gases. It is found that there is a good correlation between the electronic structures and reactivities of carbon edge sites. Zigzag sites are more active in oxygen adsorption because of the unpaired electrons and armchair sites are less active in oxygen adsorption due to the triple character. However, the desorption of semi-quinone oxygen from zigzag sites needs a bond energy ca. 30% higher than that of o-quinone oxygen from armchair edge sites. CO 2 and H 2 O adsorb on carbon surface much less favorably than O 2 . H 2 O is first physically adsorbed on the virgin graphite surface followed by chemisorption through oxygen atom approaching the carbon edge site and the movements of two hydrogen atoms to produce H 2 . The adsorption mechanism of H 2 O is different from that for CO 2 , but the final result is quite similar, i.e. producing only semi-quinone oxygen. Based upon the above studies, a new generalized mechanism, as shown in Fig. 1, is developed and can account for all the important kinetic phenomena of carbon-gas reactions. The key point is that in CO 2 /H 2 O-carbon reaction only semi-quinone formed; while, in O 2 -carbon reaction, semi-quinone, o-quinone (at lower pressure), and off-plane epoxy oxygen (at relatively higher pressure) can be formed. This is the main reason for the different reaction kinetics of O 2 -carbon reaction and CO 2 /H 2 O-carbon reactions as observed experimentally. The oxygen functional groups of carbon can be characterized by XPS, PZC (point of zero charge), IEP (isoelectric point) and TPD (temperature-programmed desorption), which were used in our previous studies. We treated the carbon surface with different acids, finding that HNO 3

By-product reuse in drinking water softening: influence of operating conditions on calcium carbonate pellet characteristics

DEFF Research Database (Denmark)

Tang, Camilla; Rosshaug, P. S.; Kristensen, J. B.

both socio-economic and environmental benefits. However, optimal implementation of softening requires a holistic approach including e.g. possibilities for by-product reuse. A pellet reactor is one widely used softening technology that may produce up to 350 kg calcium carbonate pellets per 1000 m3...

Pseudomonas, Pantoea and Cupriavidus isolates induce calcium carbonate precipitation for biorestoration of ornamental stone.

Science.gov (United States)

Daskalakis, M I; Magoulas, A; Kotoulas, G; Catsikis, I; Bakolas, A; Karageorgis, A P; Mavridou, A; Doulia, D; Rigas, F

2013-08-01

Bacterially induced calcium carbonate precipitation from various isolates was investigated aiming at developing an environmentally friendly technique for ornamental stone protection and restoration. Micro-organisms isolated from stone samples and identified using 16S rDNA and biochemical tests promoted calcium carbonate precipitation in solid and novel liquid growth media. Biomineral morphology was studied on marble samples with scanning electron microscopy. Most isolates demonstrated specimen weight increase, covering partially or even completely the marble surfaces mainly with vaterite. The conditions under which vaterite precipitated and its stability throughout the experimental runs are presented. A growth medium that facilitated bacterial growth of different species and promoted biomineralization was formulated. Most isolates induced biomineralization of CaCO3 . Micro-organisms may actually be a milestone in the investigation of vaterite formation facilitating our understanding of geomicrobiological interactions. Pseudomonas, Pantoea and Cupriavidus strains could be candidates for bioconsolidation of ornamental stone protection. Characterization of biomineralization capacity of different bacterial species improves understanding of the bacterially induced mineralization processes and enriches the list of candidates for biorestoration applications. Knowledge of biomineral morphology assists in differentiating mineral from biologically induced precipitates. © 2013 The Society for Applied Microbiology.

Think positive : phase separation enables a positively charged additive to induce dramatic changes in calcium carbonate morphology

NARCIS (Netherlands)

Cantaert, B.; Kim, Y.; Ludwig, H.; Nudelman, F.; Sommerdijk, N.A.J.M.; Meldrum, F.C.

2012-01-01

Soluble macromolecules are essential to Nature's control over biomineral formation. Following early studies where macromolecules rich in aspartic and glutamic acid were extracted from nacre, research has focused on the use of negatively charged additives to control calcium carbonate precipitation.

21 CFR 184.1210 - Calcium oxide.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium oxide. 184.1210 Section 184.1210 Food and... Substances Affirmed as GRAS § 184.1210 Calcium oxide. (a) Calcium oxide (CaO, CAS Reg. No. 1305-78-8) is also known as lime, quick lime, burnt lime, or calx. It is produced from calcium carbonate, limestone, or...

Variations in the patterns of soil organic carbon mineralization and microbial communities in response to exogenous application of rice straw and calcium carbonate

International Nuclear Information System (INIS)

Feng, Shuzhen; Huang, Yuan; Ge, Yunhui; Su, Yirong; Xu, Xinwen; Wang, Yongdong; He, Xunyang

2016-01-01

The addition of exogenous inorganic carbon (CaCO 3 ) and organic carbon has an important influence on soil organic carbon (SOC) mineralization in karst soil, but the microbial mechanisms underlying the SOC priming effect are poorly understood. We conducted a 100-day incubation experiment involving four treatments of the calcareous soil in southwestern China's karst region: control, 14 C-labeled rice straw addition, 14 C-labeled CaCO 3 addition, and a combination of 14 C-labeled rice straw and CaCO 3 . Changes in soil microbial communities were characterized using denaturing gradient gel electrophoresis with polymerase chain reaction (PCR-DGGE) and real-time quantitative PCR (q-PCR). Both 14 C-rice straw and Ca 14 CO 3 addition stimulated SOC mineralization, suggesting that organic and inorganic C affected SOC stability. Addition of straw alone had no significant effect on bacterial diversity; however, when the straw was added in combination with calcium carbonate, it had an inhibitory effect on bacterial and fungal diversity. At the beginning of the experimental period, exogenous additives increased bacterial abundance, although at the end of the 100-day incubation bacterial community abundance had gradually declined. Incubation time, exogenous input, and their interaction significantly affected SOC mineralization (in terms of priming and the cumulative amount of mineralization), microbial biomass carbon (MBC), and microbial community abundance and diversity. Moreover, the key factors influencing SOC mineralization were MBC, bacterial diversity, and soil pH. Overall, these findings support the view that inorganic C is involved in soil C turnover with the participation of soil microbial communities, promoting soil C cycling in the karst region. - Highlights: • Different patterns of 14 C-rice straw and Ca 14 CO 3 addition on positive priming effects of SOC mineralization. • Inorganic C is involved in soil C cycling with the participation of soil microbial

Biodiesel production using calcium manganese oxide as catalyst and different raw materials

International Nuclear Information System (INIS)

Dias, Joana Maia; Conceição Machado Alvim-Ferraz, Maria; Fonseca Almeida, Manuel; Méndez Díaz, José Diego; Sánchez Polo, Manuel; Rivera Utrilla, José

2013-01-01

Highlights: ► Biodiesel production using a calcium manganese oxide catalyst was studied. ► The active specie was Ca 0.9 Mn 0.1 O and its deactivation occurred by hydration. ► The studied catalyst presented lower activation temperature than CaO. ► Biodiesel production and quality using different raw materials is reported. ► Compared to the conventional process, biodiesel water content improved. - Abstract: The use of heterogeneous catalysts for biodiesel production aims to simplify the production process as well as to reduce purification costs and related environmental impacts. Calcium manganese oxide was recently identified by the authors as an interesting heterogeneous catalyst for biodiesel production from animal fat; however, the difference between this and other catalysts, the catalyst activation/deactivation mechanisms, its behaviour in the synthesis using different raw materials as well as the impacts of its use on product quality remained unclear. Therefore, the present work: (i) compared biodiesel production using calcium manganese oxide and other catalysts (CaO and NaOH); (ii) studied the reasons leading to activation/deactivation of the heterogeneous catalyst; (iii) analysed biodiesel heterogeneous synthesis using calcium manganese oxide and different raw materials (lard, waste frying oil and a mixture); and (iv) evaluated raw material and catalyst impact on the product quality. Considering the use of different catalysts, the results showed that, after 8 h of reaction, product purity was similar using the different catalysts, being 92.5 wt.% using both NaOH and calcium manganese oxide and 93.8 wt.% using CaO. The active species of the heterogeneous catalysts were CaO, in the case of calcinated calcium carbonate, and Ca 0.9 Mn 0.1 O, in the case of calcinated calcium manganese oxide. Because the deactivating species were different for both catalysts, the calcium manganese oxide required lower activation temperature, which should be an advantage

Calcium carbonate phosphate binding ion exchange filtration and accelerated denitrification improve public health standards and combat eutrophication in aquatic ecosystems.

Science.gov (United States)

Yanamadala, Vijay

2005-01-01

Cultural eutrophication, the process by which a lake becomes rich in dissolved nutrients as a result of point and nonpoint pollutant sources, is a major cause of the loss of natural lake ecosystems throughout the world. The process occurs naturally in all lakes, but phosphate-rich nutrient runoff from sources such as storm drains and agricultural runoff is a major cause of excess phosphate-induced eutrophication. Especially in Madrona Marsh, one of the last remaining vernal marshes in the greater Los Angeles area, California, cultural eutrophication has become a major problem. In this study, calcium carbonate was found to be an excellent phosphate binder, reducing up to 70% of the phosphates in a given sample of water, and it posed relatively negligent ecological repercussions. This study involved the testing of this principle in both the laboratory and the real ecosystem. A calcium carbonate lacing procedure was first carried out to determine its efficacy in Madrona Marsh. Through this, ammonia was found to interfere with the solubility of calcium carbonate and therefore to be a hindrance to the reduction of phosphate. Therefore, various approaches for reduction of ammonia were tested, including aeration, use of fiber growth media, and plants, mainly Caulerpa verticellata, chosen for it hardiness, primarily in an attempt to increase population of Nitrobacter and Nitrosomonas. All were successful in moderately reducing ammonia levels. In addition, soil sampling, sediment analysis, microscopic plant analysis, microorganism and macroinvertebrate identification, and rate law formulations were conducted. The effect of phosphate and ammonia reduction on the populations of enterobacteria was also an important focus of this experiment. Varying concentrations of phosphate, ammonia, and calcium carbonate in conjunction with phosphate were tested in Madrona Marsh to determine their effects on the populations of enteropathogens on nonspecific blood agar, MacConkey agar, and

Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties

Directory of Open Access Journals (Sweden)

Moisés Frías

2018-04-01

Full Text Available The worldwide pursuit of new eco-efficient pozzolans is ongoing. Kaolinite-based waste is an eco-friendly source of recycled metakaolinite, a highly pozzolanic product. In this study, a blended cement paste containing 20% activated coal waste (ACW was exposed to a 100% CO2 atmosphere at 65% RH for 7 days. The variations in its phase composition and strength were studied and compared to an OPC control. Both pastes were cured for 28 days prior to the carbonation test. Reaction kinetics were assessed using XRD, SEM/EDX, TG/DTG, FT-IR, Micro-Raman spectroscopy, pore solution pH and the cumulative carbonated fraction. The blended cement carbonated 68% faster than the control. While portlandite carbonation was the main reaction in both cements, decalcification was also observed (more intensely in the 20% ACW paste in other hydraulic calcium phases (C-S-H gel, monocarboaluminate (C4AcH12, ettringite and tetracalcium aluminate (C4AH13. The end product of this reaction was calcium carbonate, mainly in the form of calcite, although traces of aragonite and amorphous carbonate were also detected. Compressive strength values rose with accelerated carbonation time and pore size reduction in both cement pastes.

Safety assessments of subcutaneous doses of aragonite calcium carbonate nanocrystals in rats

Science.gov (United States)

Jaji, Alhaji Zubair; Zakaria, Zuki Abu Bakar; Mahmud, Rozi; Loqman, Mohamad Yusof; Hezmee, Mohamad Noor Mohamad; Abba, Yusuf; Isa, Tijani; Mahmood, Saffanah Khuder

2017-05-01

Calcium carbonate nanoparticles have shown promising potentials in the delivery of drugs and metabolites. There is however, a paucity of information on the safety of their intentional or accidental over exposures to biological systems and general health safety. To this end, this study aims at documenting information on the safety of subcutaneous doses of biogenic nanocrystals of aragonite polymorph of calcium carbonate derived from cockle shells (ANC) in Sprague-Dawley (SD) rats. ANC was synthesized using the top-down method, characterized using the transmission electron microscopy and field emission scanning electron microscope and its acute and repeated dose 28-day trial toxicities were evaluated in SD rats. The results showed that the homogenous 30 ± 5 nm-sized spherical pure aragonite nanocrystals were not associated with mortality in the rats. Severe clinical signs and gross and histopathological lesions, indicating organ toxicities, were recorded in the acute toxicity (29,500 mg/m2) group and the high dose (5900 mg/m2) group of the repeated dose 28-day trial. However, the medium- (590 mg/m2 body weight) and low (59 mg/m2)-dose groups showed moderate to mild lesions. The relatively mild lesions observed in the low toxicity dosage group marked the safety margin of ANC in SD rats. It was concluded from this study that the toxicity of CaCO3 was dependent on the particulate size (30 ± 5 nm) and concentration and the route of administration used.

Removal of phosphate from solution by adsorption and precipitation of calcium phosphate onto monohydrocalcite.

Science.gov (United States)

Yagi, Shintaro; Fukushi, Keisuke

2012-10-15

The sorption behavior and mechanism of phosphate on monohydrocalcite (CaCO(3)·H(2)O: MHC) were examined using batch sorption experiments as a function of phosphate concentrations, ionic strengths, temperatures, and reaction times. The mode of PO(4) sorption is divisible into three processes depending on the phosphate loading. At low phosphate concentrations, phosphate is removed by coprecipitation of phosphate during the transformation of MHC to calcite. The sorption mode at the low-to-moderate phosphate concentrations is most likely an adsorption process because the sorption isotherm at the conditions can be fitted reasonably with the Langmuir equation. The rapid sorption kinetics at the conditions is also consistent with the adsorption reaction. The adsorption of phosphate on MHC depends strongly on ionic strength, but slightly on temperature. The maximum adsorption capacities of MHC obtained from the regression of the experimental data to the Langmuir equation are higher than those reported for stable calcium carbonate (calcite or aragonite) in any conditions. At high phosphate concentrations, the amount of sorption deviates from the Langmuir isotherm, which can fit the low-to-moderate phosphate concentrations. Speciation-saturation analyses of the reacted solutions at the conditions indicated that the solution compositions which deviate from the Langmuir equation are supersaturated with respect to a certain calcium phosphate. The obtained calcium phosphate is most likely amorphous calcium phosphate (Ca(3)(PO(4))(2)·xH(2)O). The formation of the calcium phosphate depends strongly on ionic strength, temperature, and reaction times. The solubility of MHC is higher than calcite and aragonite because of its metastability. Therefore, the higher solubility of MHC facilitates the formation of the calcium phosphates more than with calcite and aragonite. Copyright © 2012 Elsevier Inc. All rights reserved.

Preparation And Characterization Of Modified Calcium Oxide From Natural Sources And Their Application In The Transesterification Of Palm Oil

Directory of Open Access Journals (Sweden)

Aqliliriana

2015-08-01

Full Text Available Abstract Calcium oxide catalysts were prepared from natural calcium sources such as limestone and mud creeper shell and the catalytic activities were evaluated in the transesterification of palm oil. The raw material which mainly composed of calcium carbonate can be easily converted to calcium oxide CaO after calcination above 1000 K for few hours. Abundant cheap sources benign high conversion and nontoxic become main advantages of these catalysts. The catalysts were characterized by XRF TGA XRD CO2-TPD SEM and BET methods. Thermal decomposition of CaCO3 will produced CaO which later will be converted into calcium hydroxide CaOH2 via simple hydration technique. Under optimum reaction condition methanol to oil ratio 151 catalyst loading 3 wt. reaction temperature 338 K for 5 hours the highest conversion of palm oil to methyl ester recorded were 98 and 94 when using modified limestone and mud creeper shell respectively. The results observed an increment up to 80 by using modified catalysts with characterization results showed high in basicity and surface area. Hence promising materials via simple and cheap method can be achieved.

Thermoluminescence of calcium-based phosphors

International Nuclear Information System (INIS)

Sunta, C.M.

1985-01-01

The paper reviews the thermoluminescence (TL) properties of calcium fluoride, calcium sulphate and calcium carbonate phosphors. In the case of the calcium fluoride mineral phosphor the main emitter of TL is the cerium impurity. Based on the TL emission spectra, two types of Ce 3+ centres can be easily distinguished; those associated with O 2- compensating ion and those which have either no local compensators or are associated with F - interstitial ions at the adjacent vacant body centre position. The spectra undergo remarkable changes at high doses. Such changes are associated with the probabilities of charge trapping at different types of traps and also with the probabilities of recombination at different types of luminescent centres. Some of the traps and recombination centres are spatially associated while others are distributed randomly. In calcium carbonate mineral, Mn 2+ is invariably the emitting impurity. Mn 2+ can be used as an efficient dopant for TL emission in all the three calcium based TL phosphors. A co-dopant like Ce 3+ intensifies the luminescence yield from Mn 2+ . Models of different types of electron and hole trapping centres are given. (author)

The Influence of Calcium Carbonate Composition and Activated Carbon in Pack Carburizing Low Carbon Steel Process in The Review of Hardness and Micro Structure

Science.gov (United States)

Hafni; Hadi, Syafrul; Edison

2017-12-01

Carburizing is a way of hardening the surface by heating the metal (steel) above the critical temperature in an environment containing carbon. Steel at a temperature of the critical temperature of affinity to carbon. Carbon is absorbed into the metal form a solid solution of carbon-iron and the outer layer has high carbon content. When the composition of the activator and the activated charcoal is right, it will perfect the carbon atoms to diffuse into the test material to low carbon steels. Thick layer of carbon Depending on the time and temperature are used. Pack carburizing process in this study, using 1 kg of solid carbon derived from coconut shell charcoal with a variation of 20%, 10% and 5% calcium carbonate activator, burner temperature of 950 0C, holding time 4 hours. The test material is low carbon steel has 9 pieces. Each composition has three specimens. Furnace used in this study is a pack carburizing furnace which has a designed burner box with a volume of 1000 x 600 x 400 (mm3) of coal-fired. Equipped with a circulation of oxygen from the blower 2 inches and has a wall of refractory bricks. From the variation of composition CaCO3, microstructure formed on the specimen with 20% CaCO3, better diffusion of carbon into the carbon steel, it is seen by the form marten site structure after quenching, and this indicates that there has been an increase of or adding carbon to in the specimen. This led to the formation of marten site specimen into hard surfaces, where the average value of hardness at one point side (side edge) 31.7 HRC

Mechanisms of aqueous wollastonite carbonation as a possible CO2 sequestration process

International Nuclear Information System (INIS)

Huijgen, W.J.J.; Comans, R.N.J.; Witkamp, G.J.

2006-02-01

The mechanisms of aqueous wollastonite carbonation as a possible carbon dioxide sequestration process were investigated experimentally by systematic variation of the reaction temperature, CO2 pressure, particle size, reaction time, liquid to solid ratio and agitation power. The carbonation reaction was observed to occur via the aqueous phase in two steps: (1) Ca leaching from the CaSiO3 matrix and (2) CaCO3 nucleation and growth. Leaching is hindered by a Ca-depleted silicate rim resulting from incongruent Ca-dissolution. Two temperature regimes were identified in the overall carbonation process. At temperatures below an optimum reaction temperature, the overall reaction rate is probably limited by the leaching rate of Ca. At higher temperatures, nucleation and growth of calcium carbonate is probably limiting the conversion, due to a reduced (bi)carbonate activity. The mechanisms for the aqueous carbonation of wollastonite were shown to be similar to those reported previously for an industrial residue and a Mg-silicate. The carbonation of wollastonite proceeds rapidly relative to Mg-silicates, with a maximum conversion in 15 min of 70% at 200C, 20 bar CO2 partial pressure and a particle size of <38 μm. The obtained insight in the reaction mechanisms enables the energetic and economic assessment of CO2 sequestration by wollastonite carbonation, which forms an essential next step in its further development

Calcium carbonate mediates higher lignin peroxidase activity in the culture supernatant of Streptomyces Viridosporus T7A

Directory of Open Access Journals (Sweden)

J. M. B. MACEDO

1999-06-01

Full Text Available Lignin peroxidase (LiP production has been extensively studied due to the potential use of this enzyme in environmental pollution control. Important aspects of the production of the enzyme by S. viridosporus T7A which have been studied include the improvement of yield and enzyme stabilization. In experiments performed in agitated flasks containing culture media composed of yeast extract as the source of nitrogen, mineral salts and different carbon sources, the use of glucose resulted in the highest values for LiP activity (350 U/L, specific LiP activity (450 U/g and productivity (7 U/L/h. As the profile obtained with glucose-containing medium suggested enzyme instability, the effect of calcium carbonate was evaluated. The addition of CaCO3 in two different concentrations, 0.5% and 5.0%, resulted in higher values of maximum LiP activity, 600 and 900 U/L, respectively. The presence of this salt also anticipated enzyme activity peaks and allowed the detection of higher enzyme activities in the extracellular medium for longer periods of time. These results indicate a positive effect of calcium carbonate on LiP production, which is extremely relevant for industrial processes.

Soluble organic additive effects on stress development during drying of calcium carbonate suspensions.

Science.gov (United States)

Wedin, Pär; Lewis, Jennifer A; Bergström, Lennart

2005-10-01

The effect of polymer, plasticizer, and surfactant additives on stress development during drying of calcium carbonate particulate coatings was studied using a controlled-environment apparatus that simultaneously monitors drying stress, weight loss, and relative humidity. We found that the calcium carbonate coatings display a drying stress evolution typical of granular films, which is characterized by a sharp capillary-induced stress rise followed by a rapid stress relaxation. The addition of a soluble polymer to the CaCO3 suspension resulted in a two-stage stress evolution process. The initial stress rise stems from capillary-pressure-induced stresses within the film, while the second, larger stress rise occurs due to solidification and shrinkage of the polymeric species. Measurements on the corresponding pure polymer solutions established a clear correlation between the magnitude of residual stress in both the polymer and CaCO3-polymer films to the physical properties of the polymer phase, i.e. its glass transition temperature, T(g), and Young's modulus. The addition of small organic molecules can reduce the residual stress observed in the CaCO3-polymer films; e.g., glycerol, which acts as a plasticizer, reduces the drying stress by lowering T(g), while surfactant additions reduce the surface tension of the liquid phase, and, hence, the magnitude of the capillary pressure within the film.

Fractional Absorption of Active Absorbable Algal Calcium (AAACa and Calcium Carbonate Measured by a Dual Stable-Isotope Method

Directory of Open Access Journals (Sweden)

Steven A. Abrams

2010-07-01

Full Text Available With the use of stable isotopes, this study aimed to compare the bioavailability of active absorbable algal calcium (AAACa, obtained from oyster shell powder heated to a high temperature, with an additional heated seaweed component (Heated Algal Ingredient, HAI, with that of calcium carbonate. In 10 postmenopausal women volunteers aged 59 to 77 years (mean ± S.D., 67 ± 5.3, the fractional calcium absorption of AAACa and CaCO3 was measured by a dual stable isotope method. 44Ca-enriched CaCO3 and AAACa were administered in all subjects one month apart. After a fixed-menu breakfast and pre-test urine collection (Urine 0, 42Ca-enriched CaCl2 was intravenously injected, followed by oral administration of 44Ca-enriched CaCO3 without carrier 15 minutes later, and complete urine collection for the next 24 hours (Urine 24. The fractional calcium absorption was calculated as the ratio of Augmentation of 44Ca from Urine 0 to Urine 24/ augmentation of 42Ca from Urine 0 to Urine 24. Differences and changes of 44Ca and 42Ca were corrected by comparing each with 43Ca. Fractional absorption of AAACa (mean ± S.D., 23.1 ± 6.4, was distinctly and significantly higher than that of CaCO3 (14.7 ± 6.4; p = 0.0060 by paired t-test. The mean fractional absorption was approximately 1.57-times higher for AAACa than for CaCO3. The serum 25(OH vitamin D level was low (mean ± S.D., 14.2 ± 4.95 ng/ml, as is common in this age group in Japan. Among the parameters of the bone and mineral metabolism measured, none displayed a significant correlation with the fractional absorption of CaCO3 and AAACa. Higher fractional absorption of AAACa compared with CaCO3 supports previous reports on the more beneficial effect of AAACa than CaCO3 for osteoporosis.

Spectrophotometric measurement of calcium carbonate saturation states in seawater.

Science.gov (United States)

Easley, Regina A; Patsavas, Mark C; Byrne, Robert H; Liu, Xuewu; Feely, Richard A; Mathis, Jeremy T

2013-02-05

Measurements of ocean pH and carbonate ion concentrations in the North Pacific and Arctic Oceans were used to determine calcium carbonate saturation states (Ω(CaCO(3))) from spectrophotometric methods alone. Total carbonate ion concentrations, [CO(3)(2-)](T), were for the first time at sea directly measured using Pb(II) UV absorbance spectra. The basis of the method is given by the following: [formula see text] where (CO(3))β(1) is the PbCO(3)(0) formation constant, e(i) are molar absorptivity ratios, and R = (250)A/(234)A (ratio of absorbances measured at 250 and 234 nm). On the basis of shipboard and laboratory Pb(II) data and complementary carbon-system measurements, the experimental parameters were determined to be (25 °C) the following: [formula see text]. The resulting mean difference between the shipboard spectrophotometric and conventional determinations of [CO(3)(2-)](T) was ±2.03 μmol kg(-1). The shipboard analytical precision of the Pb(II) method was ∼1.71 μmol kg(-1) (2.28%). Spectrophotometric [CO(3)(2-)](T) and pH(T) were then combined to calculate Ω(CaCO(3)). For the case of aragonite, 95% of the spectrophotometric aragonite saturation states (Ω(Aspec)) were within ±0.06 of the conventionally calculated values (Ω(Acalc)) when 0.5 ≤ Ω(A) ≤ 2.0. When Ω(A) > 2.0, 95% of the Ω(Aspec) values were within ±0.18 of Ω(Acalc). Our shipboard experience indicates that spectrophotometric determinations of [CO(3)(2-)](T) and Ω(CaCO(3)) are straightforward, fast, and precise. The method yields high-quality measurements of two important, rapidly changing aspects of ocean chemistry and offers capabilities suitable for long-term automated in situ monitoring.

kinetics of the coupled gas-iron reactions involving silicon and carbon

African Journals Online (AJOL)

user

1985-09-01

Sep 1, 1985 ... out for the system involving liquid iron containing carbon and silicon and a gas ... in content with liquid iron at. 15600C, the ... of carbon monoxide bubbles at the. Slag - metal ..... equilibrium strongly make chemical reactions.

How does the carbon fusion reaction happen in stars?

International Nuclear Information System (INIS)

Tang, X.; Bucher, B.; Fang, X.; Notani, M.; Tan, W.P.; Mooney, P.; Li, Y.; Esbensen, H.; Jiang, C.L.; Rehm, K.E.; Lin, C.J; Brown, E.

2012-01-01

The 12 C + 12 C fusion reaction is one of the most important reactions in the stellar evolution. Due to its complicated reaction mechanism, there is great uncertainty in the reaction rate which limits our understanding of various stellar objects, such as massive stellar evolution, explosions on neutron stars, and supernovae from accreting white dwarf stars. In this paper, I will review the challenges in the study of carbon burning. I will also report recent results from our studies: 1) an upper limit for the 12 C + 12 C fusion cross sections, 2) measurement of the 12 C + 12 C at deep sub-barrier energies, and 3) a new measurement of the 12 C( 12 C, n) reaction. The outlook for the studies of the astrophysical heavy-ion fusion reactions will also be presented

A Small-Scale Capsule Test for Investigating the Sodium-Carbon Dioxide Reaction

International Nuclear Information System (INIS)

Kim, B. H.; Choi, J. H.; Suk, S. D.; Kim, J. M.; Choi, B. H.; Kim, B. H.; Hahn, D. H.

2007-01-01

The utilization of modular sodium-to-supercritical CO 2 heat exchangers may yield significant improvements for an overall plant energy utilization. The consequences of a failure of the sodium CO 2 heat exchanger boundary, however, would involve the blowdown and intermixing of high-pressure CO 2 in a sodium pool, causing a pressurization which may threaten the structural integrity of the heat exchanger. Available data seems to indicate that the chemical reaction between sodium and CO 2 would likely produce sodium oxides, sodium carbonate, carbon and carbon monoxide. Information on the kinetics of the sodium-CO 2 reaction is virtually non-existent

Synthesis of three-dimensional calcium carbonate nanofibrous structure from eggshell using femtosecond laser ablation

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Venkatakrishnan Krishnan

2011-01-01

Full Text Available Abstract Background Natural biomaterials from bone-like minerals derived from avian eggshells have been considered as promising bone substitutes owing to their biodegradability, abundance, and lower price in comparison with synthetic biomaterials. However, cell adhesion to bulk biomaterials is poor and surface modifications are required to improve biomaterial-cell interaction. Three-dimensional (3D nanostructures are preferred to act as growth support platforms for bone and stem cells. Although there have been several studies on generating nanoparticles from eggshells, no research has been reported on synthesizing 3D nanofibrous structures. Results In this study, we propose a novel technique to synthesize 3D calcium carbonate interwoven nanofibrous platforms from eggshells using high repetition femtosecond laser irradiation. The eggshell waste is value engineered to calcium carbonate nanofibrous layer in a single step under ambient conditions. Our striking results demonstrate that by controlling the laser pulse repetition, nanostructures with different nanofiber density can be achieved. This approach presents an important step towards synthesizing 3D interwoven nanofibrous platforms from natural biomaterials. Conclusion The synthesized 3D nanofibrous structures can promote biomaterial interfacial properties to improve cell-platform surface interaction and develop new functional biomaterials for a variety of biomedical applications.

Effects of nanocalcium carbonate on egg production performance and plasma calcium of laying hens.

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Ganjigohari, S; Ziaei, N; Ramzani Ghara, A; Tasharrofi, S

2018-02-01

This experiment was conducted to evaluate the effects of nanocalcium carbonate (NCC) instead of calcium carbonate (CC) on egg production, egg weight, egg mass, FCR, blood calcium and egg quality characteristics in laying hens. A total of 120 laying hens were used in a 10-weeks trial, from week 23 to 33 of age. Laying hens were randomly assigned to six treatments with four replications, five hens each. The experimental treatments involved replacing 50% of the CC in the diet by decreasing amounts of NCC and were T1 Basal diet (BD) with 8.06% CC; T2 (6.045% of CC as a negative control); T3 (4.03% of CC replaced by 2.015% NCC); T4 (4.03% of CC replaced by 1.01% NCC); T5 (4.03% of CC replaced by 0.252% NCC) and T6 (4.03 of CC replaced with 0.126%NCC).Egg weight was unaffected by dietary treatments (p > .05). However, the egg production percentage and egg mass in T6 were less than that of other treatments (p hens in the control group had the best average feed conversion ratio (p hens' blood was recorded for birds fed T6 (p hens. © 2017 Blackwell Verlag GmbH.

Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template.

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Xue, Zhonghui; Hu, Binbin; Dai, Shuxi; Du, Zuliang

2015-10-01

Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10 mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6 h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12 h and 24 h, via "copying" the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants. Copyright © 2015. Published by Elsevier B.V.

A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean

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Battaglia, Gianna; Steinacher, Marco; Joos, Fortunat

2016-05-01

The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 export fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Monte Carlo scheme to construct a 1000-member ensemble with the Bern3D ocean model. Ensemble results are constrained by comparing simulated and observation-based fields of excess dissolved calcium carbonate (TA*). The minerals calcite and aragonite are modelled explicitly and ocean-sediment fluxes are considered. For local dissolution rates, either a strong or a weak dependency on CaCO3 saturation is assumed. In addition, there is the option to have saturation-independent dissolution above the saturation horizon. The median (and 68 % confidence interval) of the constrained model ensemble for global biogenic CaCO3 export is 0.90 (0.72-1.05) Gt C yr-1, that is within the lower half of previously published estimates (0.4-1.8 Gt C yr-1). The spatial pattern of CaCO3 export is broadly consistent with earlier assessments. Export is large in the Southern Ocean, the tropical Indo-Pacific, the northern Pacific and relatively small in the Atlantic. The constrained results are robust across a range of diapycnal mixing coefficients and, thus, ocean circulation strengths. Modelled ocean circulation and transport timescales for the different set-ups were further evaluated with CFC11 and radiocarbon observations. Parameters and mechanisms governing dissolution are hardly constrained by either the TA* data or the current compilation of CaCO3 flux measurements such that model realisations with and without saturation-dependent dissolution achieve skill. We suggest applying saturation-independent dissolution rates in Earth system

Evidence for Late Permian-Upper Triassic ocean acidification from calcium isotopes in carbonate of the Kamura section in Japan

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Ye, F.; Zhao, L., Sr.; Chen, Z. Q.; Wang, X.

2017-12-01

Calcium and carbon cycles are tightly related in the ocean, for example, through continental weathering and deposition of carbonate, thus, very important for exploring evolutions of marine environment during the earth history. The end-Permian mass extinction is the biggest biological disaster in the Phanerozoic and there are several studies talking about variations of calcium isotopes across the Permian-Triassic boundary (PTB). However, these studies are all from the Tethys regions (Payne et al., 2010; Hinojosa et al., 2012), while the Panthalassic Ocean is still unknown to people. Moreover, evolutions of the calcium isotopes during the Early to Late Triassic is also poorly studied (Blattler et al., 2012). Here, we studied an Uppermost Permian to Upper Triassic shallow water successions (Kamura section, Southwest Japan) in the Central Panthalassic Ocean. The Kamura section is far away from the continent without any clastic pollution, therefore, could preserved reliable δ44/40Cacarb signals. Conodont zonation and carbonate carbon isotope also provide precious time framework which is necessary for the explaining of the δ44/40Cacarb profile. In Kamura, δ44/40Cacarb and δ13Ccarb both exhibit negative excursions across the PTB, the δ44/40Cacarb value in the end-Permian is 1.0398‰ then abrupt decrease to the minimum value of 0.1524‰. CO2-driven global ocean acidification best explains the coincidence of the δ44/40Cacarb excursion with negative excursions in the δ13Ccarb of carbonates until the Early Smithian(N1a, N1b, N1c, P1, N2, P2). In the Middle and the Late Triassic, the δ44/40 Cacarb average approximately 1.1‰. During the Middle and Late Triassic, strong relationships between δ44/40Cacarb and δ13Ccarb are collapsed, indicating a normal pH values of the seawater in those time. The Siberian Trap volcanism probably played a significant role on the δ44/40Cacarb until the late Early Triassic. After that, δ44/40Cacarb was mostly controlled by carbonate

The effects of particle size and origin of calcium carbonate on performance and ossification characteristics in broiler chicks.

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Guinotte, F; Nys, Y; de Monredon, F

1991-09-01

The following physico-chemical characteristics of various calcium sources, differing in origin and particle size were determined: mineral composition, sieve and image analysis, apparent solubility (AS), surface area (SA), porous volume, specific gravity, and compressibility (C). The AS, SA, and C values were related more to the calcium particle size than to its origin and were higher in ground calcium sources. Calcium retention of seashells treated with phosphoric acid, oyster shells, and limestone using two particle sizes, ground or particulate, was assayed in 98 broiler chicks. Particulate marble was also tested in this experiment. Calcium retention expressed as a percentage of calcium ingestion was decreased when coarse particles of calcium were supplied in lieu of pulverized sources (40 versus 49%). An experiment with a 3 x 3 x 3 factorial arrangement of treatments were tested using 576 broiler chicks. Treatments included three calcium sources (phosphorus-treated shell, oyster shell, and marble), three particle sizes [ground (less than .15 mm), medium (.6 to 1.18 mm) and coarse (greater than 1.18 mm)] and three levels of calcium (.5,.7, and .9%) with ground limestone as a reference. Performance, tibial morphometry, breaking strength variables, and ash content were measured at 4 wk of age. Weight gain and feed conversion were ameliorated with ground particles of calcium. Cortical thickness, length of the tibia, stiffness, stress, and tibia ash were diminished when coarse particles of calcium were incorporated in the diets. Conversely, the origin of the calcium source hardly affected these criteria. Additionally, the incorporation of phosphorus-treated shells was assayed in 112 broiler chicks. Coarse particles decreased calcium retention. Consequently, ultimate stress, the modulus of elasticity, and stress were impaired. It is concluded that differences in utilization of calcium carbonate sources by the broiler chick is primarily a result of particle size rather

Beneficial Use of Carbon Dioxide in Precast Concrete Production

Energy Technology Data Exchange (ETDEWEB)

Shao, Yixin [McGill Univ., Montreal, QC (Canada)

2014-06-26

The feasibility of using carbon dioxide as feedstock in precast concrete production is studied. Carbon dioxide reacts with calcium compounds in concrete, producing solid calcium carbonates in binding matrix. Two typical precast products are examined for their capacity to store carbon dioxide during the production. They are concrete blocks and fiber-cement panels. The two products are currently mass produced and cured by steam. Carbon dioxide can be used to replace steam in curing process to accelerate early strength, improve the long-term durability and reduce energy and emission. For a reaction within a 24-hour process window, the theoretical maximum possible carbon uptake in concrete is found to be 29% based on cement mass in the product. To reach the maximum uptake, a special process is developed to promote the reaction efficiency to 60-80% in 4-hour carbon dioxide curing and improve the resistance to freeze-thaw cycling and sulfate ion attack. The process is also optimized to meet the project target of $10/tCO₂ in carbon utilization. By the use of self-concentrating absorption technology, high purity CO₂ can be produced at a price below $40/t. With low cost CO₂ capture and utilization technologies, it is feasible to establish a network for carbon capture and utilization at the vicinity of carbon sources. If all block produces and panel producers in United States could adopt carbon dioxide process in their production in place of steam, carbon utilization in these two markets alone could consume more than 2 Mt CO₂/year. This capture and utilization process can be extended to more precast products and will continue for years to come.

Effects of Eggshell Calcium Supplementation on Bone Mass in Postmenopausal Vietnamese Women.

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Sakai, Seigo; Hien, Vu Thi Thu; Tuyen, Le Danh; Duc, Ha Anh; Masuda, Yasunobu; Yamamoto, Shigeru

2017-01-01

Bone mass decreases along with aging, especially for women after menopause because of lower estrogen secretion together with low calcium intake. This study was conducted to study the effect of eggshell calcium supplementation on bone mass in 54 postmenopausal Vietnamese women living in a farming area about 60 km from Hanoi, Vietnam. Sets of 3 subjects matched by age, bone mass, BMI and calcium intake were divided randomly into 3 groups with 18 subjects in each group. The eggshell calcium group was administered 300 mg/d calcium from eggshell, the calcium carbonate group 300 mg/d calcium from calcium carbonate and the placebo group received no calcium supplementation. Bone mass (Speed of Sound (SOS)) was measured at the beginning (the baseline), the middle (6th month) and the end of the study (12th month) by the single blind method. SOS of the eggshell group increased significantly at 12 mo (p0.05). In conclusion, eggshell calcium was more effective in increasing bone mass than calcium carbonate in postmenopausal Vietnamese women.

Calcium metabolism in birds.

Science.gov (United States)

de Matos, Ricardo

2008-01-01

Calcium is one of the most important plasma constituents in mammals and birds. It provides structural strength and support (bones and eggshell) and plays vital roles in many of the biochemical reactions in the body. The control of calcium metabolism in birds is highly efficient and closely regulated in a number of tissues, primarily parathyroid gland, intestine, kidney, and bone. The hormones with the greatest involvement in calcium regulation in birds are parathyroid hormone, 1,25-dihydroxyvitamin D(3) (calcitriol), and estrogen, with calcitonin playing a minor and uncertain role. The special characteristics of calcium metabolism in birds, mainly associated with egg production, are discussed, along with common clinical disorders secondary to derangements in calcium homeostasis.

Growth of aragonite calcium carbonate nanorods in the biomimetic anodic aluminum oxide template

Science.gov (United States)

Lee, Inho; Han, Haksoo; Lee, Sang-Yup

2010-04-01

In this study, a biomimetic template was prepared and applied for growing calcium carbonate (CaCO 3) nanorods whose shape and polymorphism were controlled. A biomimetic template was prepared by adsorbing catalytic dipeptides into the pores of an anodic aluminum oxide (AAO) membrane. Using this peptide-adsorbed template, mineralization and aggregation of CaCO 3 was carried out to form large nanorods in the pores. The nanorods were aragonite and had a structure similar to nanoneedle assembly. This aragonite nanorod formation was driven by both the AAO template and catalytic function of dipeptides. The AAO membrane pores promoted generation of aragonite polymorph and guided nanorod formation by guiding the nanorod growth. The catalytic dipeptides promoted the aggregation and further dehydration of calcium species to form large nanorods. Functions of the AAO template and catalytic dipeptides were verified through several control experiments. This biomimetic approach makes possible the production of functional inorganic materials with controlled shapes and crystalline structures.

Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings

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Ahlborg, Nadia L.; Zhu, Dongming

2013-01-01

The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

How does the carbon fusion reaction happen in stars?

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X. Tang

2013-09-01

Full Text Available The 12C + 12C fusion reaction is one of the most important reactions in the stellar evolution. Due to its compli-cated reaction mechanism, there is great uncertainty in the reaction rate which limits our understanding of vari-ous stellar objects, such as explosions on the surface of neutron stars, white dwarf (type Ia supernovae, and massive stellar evolution. In this paper, I will review the challenges in the study of carbon burning. I will also report recent re-sults from our studies: 1 an upper limit for the 12C + 12C fusion cross sections, 2 measurement of the 12C + 12C at deep sub-barrier energies, 3 a new measurement of the 12C(12C, n reaction. The outlook for the studies of the astrophysical heavy-ion fusion reactions will also be presented.

Fabrication and characterization of reaction bonded silicon carbide/carbon nanotube composites

International Nuclear Information System (INIS)

Thostenson, Erik T; Karandikar, Prashant G; Chou, T.-W.

2005-01-01

Carbon nanotubes have generated considerable excitement in the scientific and engineering communities because of their exceptional mechanical and physical properties observed at the nanoscale. Carbon nanotubes possess exceptionally high stiffness and strength combined with high electrical and thermal conductivities. These novel material properties have stimulated considerable research in the development of nanotube-reinforced composites (Thostenson et al 2001 Compos. Sci. Technol. 61 1899, Thostenson et al 2005 Compos. Sci. Technol. 65 491). In this research, novel reaction bonded silicon carbide nanocomposites were fabricated using melt infiltration of silicon. A series of multi-walled carbon nanotube-reinforced ceramic matrix composites (NT-CMCs) were fabricated and the structure and properties were characterized. Here we show that carbon nanotubes are present in the as-fabricated NT-CMCs after reaction bonding at temperatures above 1400 deg. C. Characterization results reveal that a very small volume content of carbon nanotubes, as low as 0.3 volume %, results in a 75% reduction in electrical resistivity of the ceramic composites. A 96% decrease in electrical resistivity was observed for the ceramics with the highest nanotube volume fraction of 2.1%

Calcium carbonate production response to future ocean warming and acidification

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A. J. Pinsonneault

2012-06-01

Full Text Available Anthropogenic carbon dioxide (CO₂ emissions are acidifying the ocean, affecting calcification rates in pelagic organisms, and thereby modifying the oceanic carbon and alkalinity cycles. However, the responses of pelagic calcifying organisms to acidification vary widely between species, contributing uncertainty to predictions of atmospheric CO₂ and the resulting climate change. At the same time, ocean warming caused by rising CO₂ is expected to drive increased growth rates of all pelagic organisms, including calcifiers. It thus remains unclear whether anthropogenic CO₂ emissions will ultimately increase or decrease pelagic calcification rates. Here, we assess the importance of this uncertainty by introducing a dependence of calcium carbonate (CaCO₃ production on calcite saturation state (Ω_CaCO3 in an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of several variants of this dependence on global ocean carbon cycling between 1800 and 3500 under two different CO₂ emissions scenarios. Introducing a calcification-saturation state dependence has a significant effect on the vertical and surface horizontal alkalinity gradients, as well as on the removal of alkalinity from the ocean through CaCO₃ burial. These changes result in an additional oceanic uptake of carbon when calcification depends on Ω_CaCO3 (of up to 270 Pg C, compared to the case where calcification does not depend on acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500. Different versions of the model produced varying results, and narrowing this range of uncertainty will require better understanding of both temperature and acidification effects on pelagic calcifiers. Nevertheless, our results suggest that alkalinity observations can be used

Reaction velocity of sodium hydration in humid air and sodium carbonation in humid carbon dioxide atmosphere. Fundamental study on sodium carbonate process in FBR bulk sodium coolant disposal technology

International Nuclear Information System (INIS)

Tadokoro, Yutaka; Yoshida, Eiichi

1999-11-01

A sodium carbonate processing method, which changes sodium to sodium carbonate and/or sodium bicarbonate by humid carbon dioxide, has been examined and about to be applied to large test loops dismantling. However, that the basic data regarding the progress of the reaction is insufficient on the other hand, is a present condition. The present report therefore aims at presenting basic data regarding the reaction velocity of sodium hydration in humid air and sodium carbonation in humid carbon dioxide atmosphere, and observing the reaction progress, for the application to large test loops dismantling. The test result is summarized as follows. (1) Although the reaction velocity of sodium varied with sodium specimen sizes and velocity measurement methods, the reaction velocity of sodium hydration was in about 0.16 ∼ 0.34 mmh -1 (0.016 ∼ 0.033g cm -2 h -1 , 6.8x10 -4 ∼ 1.4x10 -3 mol cm -2 h -1 ) and that of sodium carbonation was in about 0.16 ∼ 0.27mmh -1 (0.016 ∼ 0.023g cm -2 h -1 , 6.8x10 -4 ∼ 1.1x10 -3 mol cm -2 h -1 ) (26 ∼ 31degC, RH 100%). (2) The reaction velocity of sodium in carbon dioxide atmosphere was greatly affected by vapor partial pressure (absolutely humidity). And the velocity was estimated in 0.08 ∼ 0.12mmh -1 (0.008 ∼ 0.012g cm -2 h -1 , 3.4x10 -4 ∼ 5.2x10 -4 mol cm -2 h -1 ) in the carbon dioxide atmosphere, whose temperature of 20degC and relative humidity of 80% are assumed real sodium carbonate process condition. (3) By the X-ray diffraction method, NaOH was found in humid air reaction product. Na 2 CO 3 , NaHCO 3 were found in carbon dioxide atmosphere reaction product. It was considered that Sodium changes to NaOH, and subsequently to NaHCO 3 through Na 2 CO 3 . (4) For the application to large test loops dismantling, it is considered possible to change sodium to a target amount of sodium carbonate (or sodium bicarbonate) by setting up gas supply quantity and also processing time appropriately according to the surface area