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Sample records for supersaturated calcium carbonate

  1. Impact of sodium polyacrylate on the amorphous calcium carbonate formation from supersaturated solution.

    Science.gov (United States)

    Liu, J; Pancera, S; Boyko, V; Gummel, J; Nayuk, R; Huber, K

    2012-02-21

    A detailed in situ scattering study has been carried out on the formation of amorphous calcium carbonate (ACC) particles modulated by the presence of small amounts of sodium polyacrylate chains. The work is aiming at an insight into the modulation of ACC formation by means of two polyacrylate samples differing in their molecular weight by a factor of 50. The ACC formation process was initiated by an in situ generation of CO(3)(2-) ions via hydrolysis of 10 mM dimethylcarbonate in the presence of 10 mM CaCl(2). Analysis of the formation process by means of time-resolved small-angle X-ray and light scattering in the absence of any additives provided evidence for a monomer addition mechanism for the growth of ACC particles. ACC formation under these conditions sets in after a lag-period of some 350 s. In the presence of sodium polyacrylate chains, calcium polyacrylate aggregates are formed during the lag-period, succeeded by a modulated ACC growth in a second step. The presence of anionic polyacrylate chains changed the shape of the growing particles toward loose and less homogeneous entities. In the case of low amounts (1.5-7.5 mg/L) of the long chain additive with 97 kDa, the size of the aggregates is comparable to the size of the successively formed hybrid particles. No variation of the lag-period has been observed in this case. Use of the short chain additive with 2 kDa enabled increase of the additive concentration up to 100 mg/L and resulted in a significant increase of the lag-period. This fact, together with the finding that the resulting hybrid particles remained stable in the latter case, identified short chain sodium polyacrylates as more efficient modulators than long chain polyacrylates.

  2. A kinetic study of precipitation from supersaturated calcium phosphate solutions

    NARCIS (Netherlands)

    Kemenade, M.J.J.M. van; Bruyn, P.L. de

    The formation of three different crystalline calcium phosphates (DCPD, OCP, HAP) and an amorphous calcium phosphate was studied as a function of pH and supersaturation. Under the experimental conditions the formation of HAP is always found to be preceded by one or more precursors in a sequence that

  3. Pore-scale simulation of calcium carbonate precipitation and dissolution under highly supersaturated conditions in a microfludic pore network

    Science.gov (United States)

    Yoon, H.; Dewers, T. A.; Valocchi, A. J.; Werth, C. J.

    2011-12-01

    Dissolved CO2 during geological CO2 storage may react with minerals in fractured rocks or confined aquifers and cause mineral precipitation. The overall rate of reaction can be affected by coupled processes among hydrodynamics, transport, and reactions at pore-scale. Pore-scale models of coupled fluid flow, reactive transport, and CaCO3 precipitation and dissolution are applied to account for transient experimental results of CaCO3 precipitation and dissolution under highly supersaturated conditions in a microfluidic pore network (i.e., micromodel). Pore-scale experiments in the micromodel are used as a basis for understanding coupled physics of systems perturbed by geological CO2 injection. In the micromodel, precipitation is induced by transverse mixing along the centerline in pore bodies. Overall, the pore-scale model qualitatively captured the governing physics of reactions such as precipitate morphology, precipitation rate, and maximum precipitation area in first few pore spaces. In particular, we found that proper estimation of the effective diffusion coefficient and the reactive surface area is necessary to adequately simulate precipitation and dissolution rates. As the model domain increases, the effect of flow patterns affected by precipitation on the overall reaction rate also increases. The model is also applied to account for the effect of different reaction rate laws on mineral precipitation and dissolution at pore-scale. Reaction rate laws tested include the linear rate law, nonlinear power law, and newly-developed rate law based on in-situ measurements at nano scale in the literature. Progress on novel methods for upscaling pore-scale models for reactive transport are discussed, and are being applied to mineral precipitation patterns observed in natural analogues. H.Y. and T. D. were supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of

  4. Urinary supersaturation with respect to brushite in patients suffering calcium oxalate lithiasis.

    Science.gov (United States)

    Berland, Y; Boistelle, R; Olmer, M

    1990-01-01

    The urines of 23 stone-formers presenting repeated calcium oxalate lithiasis and 12 control subjects were collected at six different time periods daily. Supersaturations for calcium oxalate and brushite (DCPD) were calculated using ionic and solubility products. Urines of both groups were supersaturated for calcium oxalate but only urines of the stone-formers were supersaturated for brushite, the most simple calcium phosphate which nucleates very easily at the urinary pH. This fact suggests that the core of the calcium oxalate stone could be made of either a calcium oxalate crystallite or a brushite seed onto which hetergeneous nucleation of calcium oxalate can take place.

  5. Codissolution of calcium hydrogenphosphate and sodium hydrogencitrate in water. Spontaneous supersaturation of calcium citrate increasing calcium bioavailability

    DEFF Research Database (Denmark)

    Hedegaard, Martina Vavrusova; Danielsen, Bente Pia; Garcia, André Castilho

    2017-01-01

    The sparingly soluble calcium hydrogenphosphate dihydrate, co-dissolving in water during dissolution of freely soluble sodium hydrogencitrate sesquihydrate as caused by proton transfer from hydrogencitrate to hydrogenphosphate, was found to form homogenous solutions supersaturated by a factor up......, as identified from FT-IR spectra, from these spontaneously formed supersaturated solutions was several hours, and the time to reach solubility equilibrium was several days. Initial calcium ion activity was found to be almost independent of the degree of supersaturation as determined electrochemically....... The supersaturated solutions had a pH around 4.7, and calcium binding to hydrogencitrate as the dominant citrate species during precipitation was found to be exothermic with a determined association constant of 357 L mol-1 at 25 °C for unit ionic strength, and δH° = -22 ± 2 kJ mol-1, δS° = -26 ± 8 J K-1 mol-1...

  6. Calcium Carbonate

    Science.gov (United States)

    ... doctor if you have or have ever had kidney disease or stomach conditions.tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking calcium carbonate, call your doctor.

  7. THE STUDY OF THE KINETIC PROCESSES OF SPONTANEOUS PRECIPITATION FOR CALCIUM CARBONATE SUPERSATURATED AQUEOUS SOLUTION%碳酸钙自发沉淀析出的动力学研究

    Institute of Scientific and Technical Information of China (English)

    李广兵; 方健; 李杰

    2001-01-01

    通过记录析晶过程中溶液各组份随时间的变化关系,研究了不同过饱和度的碳酸钙水溶液的沉淀动力学过程.实验结果显示,异相成核是主导的成核机制.通过实验数据计算出了表面二维晶核的棱自由能为2.53×10-8mJ*m-1.实验数据表明,碳酸钙晶体生长的过程是扩散控制过程.%By recording the time variation of the concentration of the species in the solution during preci-pitation,we studied the kinetic precipitation processes of calcium carbonate supersaturation solution.Our experimental results implied that the hetero-nucleation is the main nucleation mechanism.The free edge energy of the surface two-dimentional nucleus could also be determined from the experimental data,and yielded a value of 2.53×10-8mJ*m-1.The experimental data also indicated that the growth of crystal is controlled by diffusion mechanism.

  8. [Urinary calcium oxalate supersaturation beyond nephrolithiasis. Relationship with tubulointerstitial damage].

    Science.gov (United States)

    Toblli, Jorge E; Angerosa, Margarita; Stella, Inés; Ferder, León; Inserra, Felipe

    2003-01-01

    A number of studies have demonstrated that the urinary ion activity product (IAP) of calcium oxalate (CaOx), as an index of urinary CaOx supersaturation (SS), is higher in renal stone formers than in normal subjects. Besides, the relation between CaOx SS and lithogenesis, crystal CaOx exposition can produce tubular cell as well as renal interstitial lesions. The aim of our study was to evaluate the possible relationship between CaOx SS and tubulointerstitial (TI) damage in an animal model of hyperoxaluria. During four weeks, male Sprague-Dawley rats received: G1 (n = 8) control regular water, and G2 (n = 8) 1% ethylene glycol (ETG) (precursor for oxalates) in drinking water. In order to evaluate urinary CaOx SS, IAP assessed by Tisselius formula was performed. At the end of the study, renal lesions were evaluated by light microscopy and immunohistochemistry. Animals from G2 (ETG) presented higher (p intersticial fibrosis; e) interstitial alpha-smooth muscle actin; f) collagen type III; g) TI TGF beta 1 compared with G1 (control). Rats from G2 (ETG) presented a high correlation between urinary CaOx SS and most of the TI damage parameters evaluated, in especial with interstitial fibrosis. Both, inflammatory infiltrates and urinary CaOx SS were the most significant variables related to interstitial fibrosis. Finally, since hyperoxaluric animals showed higher urinary CaOx SS associated with higher renal TI damage, the results from this study suggest the presence of a tight link between urinary CaOx SS and renal TI damage. Considering these findings we think that urinary CaOx SS control rises in importance beyond nephrolithiasis.

  9. Sensitivity and specificity of 24-hour urine chemistry levels for detecting elevated calcium oxalate and calcium phosphate supersaturation

    Science.gov (United States)

    Rossi, M. Adrian; Singer, Eric A; Golijanin, Dragan J; Monk, Rebeca D; Erturk, Erdal; Bushinsky, David A

    2008-01-01

    Objectives The gold standard for determining likelihood of calcium oxalate (CaOx) and calcium phosphate (CaPhos) stone formation in urine is supersaturation of CaOx and CaPhos. Our objective was to investigate whether traditional measurement of total calcium, oxalate and phosphate in a 24-hour urine collection is sufficiently sensitive and specific for detecting elevated supersaturation to preclude the more expensive supersaturation test. Methods We performed a retrospective review of 150 consecutive patients with nephrolithiasis who underwent measurement of CaOx supersaturation (CaOxSS) and CaPhos supersaturation (CaPhosSS), as well as total calcium, oxalate and phosphate in a 24-hour urine collection. We used various cut-off values to determine sensitivity and specificity of 24-hour urine measurements for detecting elevated CaOxSS and CaPhosSS. Results In men and women, the sensitivity of 24-hour calcium for detecting elevated CaOxSS was 71% and 79%, respectively; for oxalate, sensitivity was 59% and 36%, respectively. In men and women, the sensitivity of 24-hour calcium for detecting elevated CaPhosSS was 74% and 88%, respectively; for phosphate, sensitivity was 57% and 8%, respectively. In men and women, the specificity of 24-hour calcium for detecting elevated CaOxSS was 55% and 48%, respectively; it was 60% for detecting elevated CaPhosSS in both men and women. Conclusion Traditional 24-hour urine analysis is sensitive, but not specific, for detecting elevated CaOxSS and CaPhosSS. Most patients with abnormal 24-hour urine analysis have normal supersaturation, and treatment decisions based on traditional urine analysis would lead to overtreatment in these patients. PMID:18542745

  10. Growth kinetics of calcium fluoride at high supersaturation in a fluidized bed reactor.

    Science.gov (United States)

    Jiang, K; Zhou, K G; Yang, Y C; Du, H

    2014-01-01

    Crystallization process in a fluidized bed reactor (FBR) has been regarded as an environmentally friendly technology for the removal and recovery of fluoride from industrial wastewater. The growth kinetics of calcium fluoride at high supersaturation was studied for design, control, and operation of an FBR. The main variables, including supersaturation, superficial velocity, pH value, and particle size of seed that influenced the crystal growth were investigated. Then, a growth model was used to predict the linear growth rate of calcium fluoride at a high influent concentration of fluoride. The pressure difference in the FBR was used as a feature to characterize the growth rate of calcium fluoride. The aggregation and adsorption between seeds and fine particles were proven to be a possible mechanism for growth of calcium fluoride.

  11. A CONTROLLED METABOLIC DIET REDUCES CALCIUM OXALATE SUPERSATURATION BUT NOT OXALATE EXCRETION AFTER BARIATRIC SURGERY

    Science.gov (United States)

    Pang, Ran; Linnes, Michael; O’Connor, Helen M.; Li, Xujian; Bergstralh, Eric; Lieske, John C.

    2012-01-01

    Objective To identify the effect of controlled metabolic diet on reducing urinary calcium oxalate supersaturation in subjects with hyperoxaluric nephrolithiasis after potentially malabsorptive forms of bariatric surgery. Materials and Methods Subjects with a history of CaOx kidney stones and mild hyperoxaluria after bariatric surgery (n=9) collected baseline 24-hour urine samples while on a free choice diet. They were then placed on a controlled diet low in oxalate (70 – 80 mg/day), normal in calcium (1000 mg/day), and moderate in protein prior to 2 final 24-hour urine collections. Results Overall urinary CaOx supersaturation fell from 1.97 ± 0.49 delta Gibbs (DG) on the free choice diet to 1.13 ± 0.75 DG on the controlled diet (P0.05), contributing to the significant CaOx supersaturation change. Conclusions A controlled metabolic diet normal in calcium, moderate in protein and reduced in oxalate can positively impact urinary CaOx supersaturation after bariatric surgery. However, this diet did not appear to decrease urinary oxalate excretion. Therefore, restriction of dietary oxalate alone may not be enough to reduce urinary oxalate excretion to normal levels in this group of known enteric hyperoxaluric patients. Additional strategies may be necessary, such as use of oral calcium supplements as oxalate binders and a lower fat diet. PMID:22554593

  12. Controlled metabolic diet reduces calcium oxalate supersaturation but not oxalate excretion after bariatric surgery.

    Science.gov (United States)

    Pang, Ran; Linnes, Michael P; O'Connor, Helen M; Li, Xujian; Bergstralh, Eric; Lieske, John C

    2012-08-01

    To identify the effect of a controlled metabolic diet on reducing urinary calcium oxalate (CaOx) supersaturation in subjects with hyperoxaluric nephrolithiasis after potentially malabsorptive forms of bariatric surgery. Subjects with a history of CaOx kidney stones and mild hyperoxaluria after bariatric surgery (n = 9) collected baseline 24-hour urine samples while consuming a free choice diet. They were then instructed to consume a controlled diet low in oxalate (70-80 mg/d), normal in calcium (1000 mg/d), and moderate in protein before 2 final 24-hour urine collections. Overall, the urinary CaOx supersaturation decreased from 1.97 ± 0.49 delta Gibbs (DG) with the free choice diet to 1.13 ± 0.75 DG with the controlled diet (P .05), contributing to the significant CaOx supersaturation change. A controlled metabolic diet normal in calcium, moderate in protein, and reduced in oxalate can positively affect urinary CaOx supersaturation after bariatric surgery. However, this diet did not appear to decrease urinary oxalate excretion. Therefore, restriction of dietary oxalate alone might not be enough to reduce urinary oxalate excretion to normal levels in this group of patients with known enteric hyperoxaluria. Additional strategies could be necessary, such as the use of oral calcium supplements as oxalate binders and a lower fat diet. Copyright © 2012 Elsevier Inc. All rights reserved.

  13. Detonation wave driven by condensation of supersaturated carbon vapor.

    Science.gov (United States)

    Emelianov, A; Eremin, A; Fortov, V; Jander, H; Makeich, A; Wagner, H Gg

    2009-03-01

    An experimental observation of a detonation wave driven by the energy of condensation of supersaturated carbon vapor is reported. The carbon vapor was formed by the thermal decay of unstable carbon suboxide C3O2 behind shock waves in mixtures containing 10-30% C3O2 in Ar. In the mixture 10% C3O2+Ar the insufficient heat release resulted in a regime of overdriven detonation. In the mixture 20% C3O2+Ar measured values of the pressure and wave velocity coincident with calculated Chapman-Jouguet parameters were attained. In the richest mixture 30% C3O2+Ar an excess heat release caused the slowing down of the condensation rate and the regime of underdriven detonation was observed.

  14. Morphological Investigation of Calcium Carbonate during Ammonification-Carbonization Process of Low Concentration Calcium Solution

    Directory of Open Access Journals (Sweden)

    Huaigang Cheng

    2014-01-01

    Full Text Available Ultrafine calcium carbonate is a widely used cheap additive. The research is conducted in low degree supersaturation solution in order to study the polymorphic phases’ change and its factors of the calcium carbonate precipitate in the ammonification-carbonization process of the solution with calcium. Fine particles of calcium carbonate are made in the solution containing 0.015 mol/L of Ca2+. Over 98% of the calcium carbonate precipitate without ammonification resembles the morphology of calcite, while the introduction of ammonia can benefit the formation of vaterite. It was inferred that the main cause should be serious partial oversaturation or steric effects. Ammonia also helps to form the twin spherical calcium carbonate. However, particles formed in the process of ammonification-carbonization in solution with low concentration degree of calcium are not even with a scale of the particle diameter from 5 to 12 μm. Inorganic salts, alcohol, or organic acid salts have significant controlling effect on the particle diameter of calcium carbonate and can help to decrease the particle diameter to about 3 μm. Anionic surfactants can prevent the conglobation of calcium carbonate particles and shrink its diameter to 500 nm–1 μm.

  15. Supersaturation of poorly soluble drugs induced by mesoporous magnesium carbonate.

    Science.gov (United States)

    Zhang, Peng; Zardán Gómez de la Torre, Teresa; Welch, Ken; Bergström, Christel; Strømme, Maria

    2016-10-10

    This work investigates whether the solubility of poorly soluble compounds can be improved by using mesoporous magnesium carbonate (MMC) as the drug delivery system. A solvent evaporation method was used to load structurally diverse model drugs (celecoxib, cinnarizine and griseofulvin) into the pores of MMC. The drug-loaded carrier system was then characterized in terms of porosity, crystallinity, and release profiles by a variety of experimental techniques, including X-ray diffraction, nitrogen adsorption analysis, differential scanning calorimetry, infrared spectroscopy, UV absorption spectroscopy, and thermogravimetric analysis. All three drugs were in a non-crystalline state after loading into the pores of MMC. The concentrations of the drugs in solution over time (a measure of the release rates from loaded MMC) were higher than the corresponding concentrations (dissolution rates) of equal amounts of the crystalline drugs. The release rates were five (celecoxib), three (cinnarizine) and two times (griseofulvin) higher than the dissolution rates of their crystalline counterparts. Supersaturation release profiles were also observed; the areas under the concentration-time curves (0-240min) were 25- (celecoxib), 5- (cinnarizine) and 2-fold (griseofulvin) greater than those of the crystalline drugs. Hence, MMC shows promise as a general drug delivery vehicle for increasing the bioavailability of compounds with dissolution rate- or solubility-limited absorption. Copyright © 2016. Published by Elsevier B.V.

  16. 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

  17. Calcium carbonate overdose

    Science.gov (United States)

    Calcium carbonate is not very poisonous. Recovery is quite likely. But, long-term overuse is more serious than a single overdose, because it can cause kidney damage. Few people die from an antacid overdose. Keep all medicines in child-proof bottles and out ...

  18. Calcium carbonate crystallisation at the microscopic level

    CERN Document Server

    Dobson, P S

    2001-01-01

    The primary concern of this thesis is the investigation of crystal nucleation and growth processes, and the effect of foreign substrates on the rate, extent and mechanism of crystallisation, with particular emphasis on the calcium carbonate system. A methodology, based on the in-line mixing of two stable solutions, which permits the continuous delivery of a solution with a constant, known supersaturation, has been developed and characterised. This has been used to induce CaCO sub 3 crystallisation in experimental systems involving the channel flow and wall jet techniques. The channel flow method has been adapted to facilitate the study of crystal growth at a single calcite crystal. Ca sup 2 sup + ion selective electrodes have been employed as a means of monitoring depletion of the supersaturated solution, downstream of the crystal substrate. The data obtained suggested a growth rate constant of 3x10 sup - sup 1 sup 2 mol cm sup - sup 2 s sup - sup 1 (and a reaction order of 1.52 on supersaturation). The ex-si...

  19. Crystallization kinetics of calcium carbonate at a stoichiometric ratio of components

    Science.gov (United States)

    Pochitalkina, I. A.; Kekin, P. A.; Morozov, A. N.; Petropavlovskii, I. A.; Kondakov, D. F.

    2016-12-01

    The formal kinetics of calcium carbonate crystallization in aqueous solutions is studied at a stoichiometric ratio of Ca2+ and CO3 2- ions. The kinetics of the process was monitored by convenient and reliable methods (complexometric analysis for calcium in an aqueous solution and energy dispersive and microscopic measurement of solid particle sizes). The effect the temperature and degree of supersaturation have on the periods of induction and mass crystallization and the equilibrium concentration of calcium ions in solution is estimated at continuously controlled pH and solution ionic strength. The kinetic parameters ( n, k, τ1/2, E a) of calcium carbonate crystallization are calculated. It is shown that calcium carbonate with a calcite structure formed at a stoichiometric ratio of reagents, and changes in the temperature (25-45°C) and the solution's degree of supersaturation (2-6) within the considered range had no effect on the characteristics of the solid phase.

  20. 21 CFR 184.1191 - Calcium carbonate.

    Science.gov (United States)

    2010-04-01

    ... HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of... soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the...

  1. The nacre protein perlucin nucleates growth of calcium carbonate crystals.

    Science.gov (United States)

    Blank, S; Arnoldi, M; Khoshnavaz, S; Treccani, L; Kuntz, M; Mann, K; Grathwohl, G; Fritz, M

    2003-12-01

    Atomic force microscopy (AFM) in aqueous solution was used to investigate native nacre of the marine snail Haliotis laevigata on the microscopic scale and the interaction of purified nacre proteins with calcium carbonate crystals on the nanoscopic scale. These investigations were controlled by scanning electron microscopy (SEM), light microscopy (LM) and biochemical methods. For investigations with AFM and SEM, nacre was cleaved parallel to the aragonite tablets in this biogenic polymer/mineral composite. Multilamellar organic sheets consisting of a core of chitin with layers of proteins attached on both sides lay between the aragonite layers consisting of confluent aragonite tablets. Cleavage appeared to occur between the aragonite tablet layer and the protein layer. AFM images revealed a honeycomb-like structure to the organic material with a diameter of the 'honeycombs' equalling that of the aragonite tablets. The walls of the structures consisted of filaments, which were suggested to be collagen. The flat regions of the honeycomb-like structures exhibited a hole with a diameter of more than 100 nm. When incubated in saturated calcium carbonate solution, aragonite needles with perfect vertical orientation grew on the proteinacous surface. After treatment with proteinase K, no growth of orientated aragonite needles was detected. Direct AFM measurements on dissolving and growing calcite crystals revealed a surface structure with straight steps the number of which decreased with crystal growth. When the purified nacre protein perlucin was added to the growth solution (a super-saturated calcium carbonate solution) new layers were nucleated and the number of steps increased. Anion exchange chromatography of the water-soluble proteins revealed a mixture of about 10 different proteins. When this mixture was dialysed against saturated calcium carbonate solution and sodium chloride, calcium carbonate crystals precipitated together with perlucin leaving the other proteins

  2. Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.

    Science.gov (United States)

    Henrickson, Charles H.; Robinson, Paul R.

    1979-01-01

    The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)

  3. Variable efficacy of calcium carbonate tablets.

    Science.gov (United States)

    Kobrin, S M; Goldstein, S J; Shangraw, R F; Raja, R M

    1989-12-01

    Orally administered calcium carbonate tablets are commonly prescribed as a calcium supplement and for their phosphate-binding effects in renal failure patients. Two cases are reported in which a commercially available brand of calcium carbonate tablets appeared to be ineffective. Formal investigation of the bioavailability of this product revealed it to have impaired disintegration and dissolution and a lack of clinical efficacy. Recommendations that will enable physicians to avoid prescribing and pharmacists to avoid dispensing ineffective calcium carbonate tablets are proposed.

  4. Sulfate but not thiosulfate reduces calculated and measured urinary ionized calcium and supersaturation: implications for the treatment of calcium renal stones.

    Directory of Open Access Journals (Sweden)

    Allen Rodgers

    Full Text Available Urinary sulfate (SO4(2- and thiosulfate (S2O3(2- can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa and on supersaturation (SS of calcium oxalate (CaOx and calcium phosphate (CaP, and measured their in vitro effects on iCa and the upper limit of stability (ULM of these salts.Urine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1. A second data set was obtained from healthy controls and hypercalciuric stone formers in the literature who had been treated with sodium thiosulfate (STS (Model 2. The Joint Expert Speciation System (JESS was used to calculate iCa and SS. In Model 1, these parameters were calculated as a function of sulfate and thiosulfate concentrations. In Model 2, data from pre- and post STS urines were analyzed. ULM and iCa were determined in human urine as a function of sulfate and thiosulfate concentrations.Calculated iCa and SS values for all calcium salts decreased with increasing sulfate concentration. Thiosulfate had no effect on these parameters. In Model 2, calculated iCa and CaOx SS increased after STS treatment, but CaP SS decreased, perhaps due to a decrease in pH after STS treatment. In confirmatory in vitro experiments supplemental sulfate, but not thiosulfate, significantly increased the calcium needed to achieve the ULM of CaP and tended to increase the oxalate needed to reach the ULM of CaOx. Sulfate also significantly decreased iCa in human urine, while thiosulfate had no effect.Increasing urinary sulfate could theoretically reduce CaOx and CaP stone risk. Although STS may reduce CaP stone risk by decreasing urinary pH, it might also paradoxically increase iCa and CaOx SS. As such, STS may not be a viable treatment option for stone disease.

  5. Sulfate but Not Thiosulfate Reduces Calculated and Measured Urinary Ionized Calcium and Supersaturation: Implications for the Treatment of Calcium Renal Stones

    Science.gov (United States)

    Rodgers, Allen; Gauvin, Daniel; Edeh, Samuel; Allie-Hamdulay, Shameez; Jackson, Graham; Lieske, John C.

    2014-01-01

    Background Urinary sulfate (SO42−) and thiosulfate (S2O32−) can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa) and on supersaturation (SS) of calcium oxalate (CaOx) and calcium phosphate (CaP), and measured their in vitro effects on iCa and the upper limit of stability (ULM) of these salts. Methods Urine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1). A second data set was obtained from healthy controls and hypercalciuric stone formers in the literature who had been treated with sodium thiosulfate (STS) (Model 2). The Joint Expert Speciation System (JESS) was used to calculate iCa and SS. In Model 1, these parameters were calculated as a function of sulfate and thiosulfate concentrations. In Model 2, data from pre- and post STS urines were analyzed. ULM and iCa were determined in human urine as a function of sulfate and thiosulfate concentrations. Results Calculated iCa and SS values for all calcium salts decreased with increasing sulfate concentration. Thiosulfate had no effect on these parameters. In Model 2, calculated iCa and CaOx SS increased after STS treatment, but CaP SS decreased, perhaps due to a decrease in pH after STS treatment. In confirmatory in vitro experiments supplemental sulfate, but not thiosulfate, significantly increased the calcium needed to achieve the ULM of CaP and tended to increase the oxalate needed to reach the ULM of CaOx. Sulfate also significantly decreased iCa in human urine, while thiosulfate had no effect. Conclusion Increasing urinary sulfate could theoretically reduce CaOx and CaP stone risk. Although STS may reduce CaP stone risk by decreasing urinary pH, it might also paradoxically increase iCa and CaOx SS. As such, STS may not be a viable treatment option for stone disease. PMID:25061988

  6. Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

    OpenAIRE

    Wilson, Rosamund J; Copley, J Brian

    2017-01-01

    Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent...

  7. 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.

  8. Induced calcium carbonate precipitation using Bacillus species.

    Science.gov (United States)

    Seifan, Mostafa; Samani, Ali Khajeh; Berenjian, Aydin

    2016-12-01

    Microbially induced calcium carbonate precipitation is an emerging process for the production of self-healing concrete. This study was aimed to investigate the effects and optimum conditions on calcium carbonate biosynthesis. Bacillus licheniformis, Bacillus sphaericus, yeast extract, urea, calcium chloride and aeration were found to be the most significant factors affecting the biomineralization of calcium carbonate. It was noticed that the morphology of microbial calcium carbonate was mainly affected by the genera of bacteria (cell surface properties), the viscosity of the media and the type of electron acceptors (Ca(2+)). The maximum calcium carbonate concentration of 33.78 g/L was achieved at the optimum conditions This value is the highest concentration reported in the literature.

  9. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.

    2012-01-01

    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate ab

  10. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.

    2012-01-01

    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate ab

  11. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.

    2012-01-01

    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate

  12. 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

  13. Highly CO2-supersaturated melts in the Pannonian lithospheric mantle - A transient carbon reservoir?

    Science.gov (United States)

    Créon, Laura; Rouchon, Virgile; Youssef, Souhail; Rosenberg, Elisabeth; Delpech, Guillaume; Szabó, Csaba; Remusat, Laurent; Mostefaoui, Smail; Asimow, Paul D.; Antoshechkina, Paula M.; Ghiorso, Mark S.; Boller, Elodie; Guyot, François

    2017-08-01

    determined by Raman spectroscopy and microthermometry (0.1-1.1 GPa). The CO2/silicate melt mass ratios in the metasomatic agent that percolated through the lithospheric mantle below the Pannonian Basin are estimated to be between 9.0 and 25.4 wt.%, values consistent with metasomatism either by (1) silicate melts already supersaturated in CO2 before reaching lithospheric depths or (2) carbonatite melts that interacted with mantle peridotite to generate carbonated silicic melts. Taking the geodynamical context of the Pannonian Basin and our calculations of the CO2/silicate melt mass ratios in the metasomatic agent into account, we suggest that slab-derived melts initially containing up to 25 wt.% of CO2 migrated into the lithospheric mantle and exsolved CO2-rich fluid that became trapped in secondary fluid inclusions upon fracturing of the peridotite mineral matrix. We propose a first-order estimate of 2000 ppm as the minimal bulk CO2 concentration in the lithospheric mantle below the Pannonian Basin. This transient carbon reservoir is believed to be degassed through the Pannonian Basin due to volcanism and tectonic events, mostly focused along the lithospheric-scale regional Mid-Hungarian shear Zone.

  14. Investigation of the chemistry of calcium carbonate scale nucleation and growth from seawater on OTEC heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Morse, J.W.; Brass, G.W.; Walter, L.M.; Van Valin, R.

    1979-08-01

    The potential for calcium carbonate scale formation, from supersaturated seawater on candidate Ocean Thermal Energy Conversion heat exchanger tubes, has been tested under flowing and stagnant seawater, and leaking liquid ammonia conditions. It was not possible to confirm the existence of calcium carbonate in any of the deposits formed. However, the presence of calcium in the deposits, generally as a minor component, indicates that microcrystalline calcium carbonate may be formed. Tests performed on growth rates of calcite and aragonite powders in seawater indicate that the maximum thickening rate of a calcium carbonate scale, under conditions which are likely to be encountered in heat exchanger tubes, is less than 20 ..mu..m per month.

  15. 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.

  16. Influence of acidifying or alkalinizing diets on bone mineral density and urine relative supersaturation with calcium oxalate and struvite in healthy cats.

    Science.gov (United States)

    Bartges, Joseph W; Kirk, Claudia A; Cox, Sherry K; Moyers, Tamberlyn D

    2013-10-01

    To evaluate the influence of acidifying or alkalinizing diets on bone mineral density and urine relative supersaturation (URSS) with calcium oxalate and struvite in healthy cats. 6 castrated male and 6 spayed female cats. 3 groups of 4 cats each were fed diets for 12 months that differed only in acidifying or alkalinizing properties (alkalinizing, neutral, and acidifying). Body composition was estimated by use of dual energy x-ray absorptiometry, and 48-hour urine samples were collected for URSS determination. Urine pH differed significantly among diet groups, with the lowest urine pH values in the acidifying diet group and the highest values in the alkalinizing diet group. Differences were not observed in other variables except urinary ammonia excretion, which was significantly higher in the neutral diet group. Calcium oxalate URSS was highest in the acidifying diet group and lowest in the alkalinizing diet group; struvite URSS was not different among groups. Diet was not significantly associated with bone mineral content or density. Urinary undersaturation with calcium oxalate was achieved by inducing alkaluria. Feeding an alkalinizing diet was not associated with URSS with struvite. Bone mineral density and calcium content were not adversely affected by diet; therefore, release of calcium from bone caused by feeding an acidifying diet may not occur in healthy cats.

  17. Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

    Science.gov (United States)

    Wilson, Rosamund J; Copley, J Brian

    2017-01-01

    Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed. Findings Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Conclusion Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance. PMID:28182142

  18. Homogeneous nucleation in supersaturated vapors of methane, ethane, and carbon dioxide predicted by brute force molecular dynamics

    CERN Document Server

    Horsch, Martin; Bernreuther, Martin; Grottel, Sebastian; Reina, Guido; Wix, Andrea; Schaber, Karlheinz; Hasse, Hans

    2009-01-01

    Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapors of methane, ethane, and carbon dioxide. Simulations of systems with up to a million particles were conducted with a massively parallel MD program. This leads to reliable statistics and makes nucleation rates down to the order of 10^30/(m^3 s) accessible to the direct simulation approach. Simulation results are compared to the classical nucleation theory (CNT) as well as the theory of Laaksonen, Ford, and Kulmala (LFK) which introduces a size dependence of the specific surface energy. CNT describes the nucleation of ethane and carbon dioxide excellently over the entire studied temperature range, whereas LFK provides a better approach to methane at low temperatures.

  19. Differentiating calcium oxalate and hydroxyapatite stones in vivo using dual-energy CT and urine supersaturation and pH values.

    Science.gov (United States)

    Liu, Yu; Qu, Mingliang; Carter, Rickey E; Leng, Shuai; Ramirez-Giraldo, Juan Carlos; Jaramillo, Giselle; Krambeck, Amy E; Lieske, John C; Vrtiska, Terri J; McCollough, Cynthia H

    2013-12-01

    Knowledge of urinary stone composition can guide therapeutic intervention for patients with calcium oxalate (CaOx) or hydroxyapatite (HA) stones. In this study, we determined the accuracy of noninvasive differentiation of these two stone types using dual-energy CT (DECT) and urine supersaturation (SS) and pH values. Patients who underwent clinically indicated DECT scanning for stone disease and subsequent surgical intervention were enrolled. Stone composition was determined using infrared spectroscopy. DECT images were processed using custom-developed software that evaluated the ratio of CT numbers between low- and high-energy images. Clinical information, including patient age, gender, and urine pH and supersaturation profile, was obtained from electronic medical records. Simple and multiple logistic regressions were used to determine if the ratio of CT numbers could discriminate CaOx from HA stones alone or in conjunction with urine supersaturation and pH. Urinary stones (CaOx n = 43, HA n = 18) from 61 patients were included in this study. In a univariate model, DECT data, urine SS-HA, and urine pH had an area under the receiver operating characteristic curve of 0.78 (95% confidence interval [CI] 0.66-0.91, P = .016), 0.76 (95% CI 0.61-0.91, P = .003), and 0.60 (95% CI 0.44-0.75, P = .20), respectively, for predicting stone composition. The combination of CT data and the urinary SS-HA had an area under the receiver operating characteristic curve of 0.79 (95% CI 0.66-0.92, P = .007) for correctly differentiating these two stone types. DECT differentiated between CaOx and HA stones similarly to SS-HA, whereas pH was a poor discriminator. The combination of DECT and urine SS or pH data did not improve this performance. Copyright © 2013 AUR. Published by Elsevier Inc. All rights reserved.

  20. Inhibition of calcium carbonate crystal growth by organic additives using the constant composition method in conditions of recirculating cooling circuits

    Science.gov (United States)

    Chhim, Norinda; Kharbachi, Chams; Neveux, Thibaut; Bouteleux, Céline; Teychené, Sébastien; Biscans, Béatrice

    2017-08-01

    The cooling circuits used in power plants are subject to mineral crystallization which can cause scaling on the surfaces of equipment and construction materials reducing their heat exchange efficiency. Precipitated calcium carbonate is the predominant mineral scale commonly observed in cooling systems. Supersaturation is the key parameter controlling the nucleation and growth of calcite in these systems. The present work focuses on the precipitation of calcite using the constant composition method at constant supersaturation, through controlled addition of reactants to a semi-batch crystallizer, in order to maintain constant solution pH. The determination of the thermodynamic driving force (supersaturation) was based on the relevant chemical equilibria, total alkalinity and calculation of the activity coefficients. Calcite crystallization rates were derived from the experiments performed at supersaturation levels similar to those found in industrial station cooling circuits. Several types of seeds particles were added into the aqueous solution to mimic natural river water conditions in terms of suspended particulate matters content, typically: calcite, silica or illite particles. The effect of citric and copolycarboxylic additive inhibitors added to the aqueous solution was studied. The calcium carbonate growth rate was reduced by 38.6% in the presence of the citric additive and a reduction of 92.7% was observed when the copolycarboxylic additive was used under identical experimental conditions. These results are explained by the location of the adsorbed inhibitor at the crystal surface and by the degree of chemical bonding to the surface.

  1. CO2 supersaturation and net heterotrophy in a tropical estuary (Cochin, India): Influence of anthropogenic effect - Carbon dynamics in tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, G.V.M.; Thottathil, S.D.; Balachandran, K.K.; Madhu, N.V.; Madeswaran, P.; Nair, S.

    : Role of dissolved organic drawdown, resuspended sediments and terrigenous inputs in carbon balance of Lake Michigan. Ecosystems 5: 431-445. Biswas H, Mukhopadhyay SK, De TK, Sen S, Jana TK. 2004. Biogenic controls on the air-water carbon dioxide...-1319. Chen CTA, Liu KK, Macdonald R. 2003. Continental margin exchanges. Fasham MJR, editor. Ocean biogeochemistry. New York: Springer-Verlag New York. p53–97. Cole JJ, Caraco NF, Kling GW, Kratz TK. 1994. Carbon dioxide supersaturation in the surface...

  2. Evaluation of quick disintegrating calcium carbonate tablets

    OpenAIRE

    Fausett, Hector; Gayser, Charles; Dash, Alekha K.

    2000-01-01

    The purpose of this investigation was to develop a rapidly disintegrating calcium carbonate (CC) tablet by direct compression and compare it with commercially available calcium tablets. CC tablets were formulated on a Carver press using 3 different forms of CC direct compressed granules (Cal-Carb 4450®, Cal-Carb 4457®, and Cal-Carb 4462®). The breaking strength was measured using a Stokes-Monsanto hardness tester. The disintegration and dissolution properties of the tablets were studied using...

  3. Risk of nephrolithiasis, hyperoxaluria, and calcium oxalate supersaturation increased after Roux-en-Y gastric bypass surgery: a systematic review and meta-analysis.

    Science.gov (United States)

    Upala, Sikarin; Jaruvongvanich, Veeravich; Sanguankeo, Anawin

    Earlier publications have shown renal stone complications after bariatric surgery. Multiple reports have also linked metabolic changes that alter the urinary chemistry profiles, especially hyperoxaluria, after bariatric surgery. However, evidence on change of other urine chemistry studies and type of bariatric surgery and risk of stone has been inconclusive so far. To explore the association between bariatric surgery and postoperative urinary chemistry change and risk of stone formation SETTING: A systematic review and meta-analysis. We comprehensively searched the databases of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) from their dates of inception to January 2016. The inclusion criteria were published studies of association between bariatric surgery and postoperative renal stone formation or urine chemistry profiles. We used random-effects model meta-analysis and calculated the pooled risk of renal stone and difference in 24-hour urine chemistry profiles. Twelve observational studies were included in the meta-analysis. There was significantly higher risk of stone formation after Roux-en-Y gastric bypass surgery with pooled relative risk = 1.79 (95% CI: 1.54-2.10). In the analysis of urine chemistry profiles, there was significantly higher calcium oxalate supersaturation, lower citrate, and lower volume postoperatively compared with preoperatively. There was also higher urine oxalate in patients who had bariatric surgery compared with nonsurgery controls. Roux-en-Y gastric bypass surgery is associated with higher risk of renal stone and increased urine oxalate and calcium oxalate supersaturation. Copyright © 2016 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved.

  4. Carbonated beverages and urinary calcium excretion.

    Science.gov (United States)

    Heaney, R P; Rafferty, K

    2001-09-01

    Intake of carbonated beverages has been associated with increased fracture risk in observational studies. The usual explanation given is that one or more of the beverage constituents increase urinary calcium. We assessed the short-term effects on urinary calcium excretion of carbonated beverages of various compositions. An incomplete random block design was used to study 20-40-y-old women who customarily consumed > or =680 mL carbonated beverages daily. Four carbonated beverages were tested: 2 with caffeine and 2 without. Two contained phosphoric acid as the acidulant and 2 contained citric acid. The study included one neutral control (water) and one positive control (skim or chocolate milk). Serving size was 567 mL for the carbonated beverages and water and 340 mL for the milks. Beverages were consumed with a light breakfast after an overnight fast; no other foods were ingested until urine collection was complete. pH, titratable and total acidity, sodium, creatinine, and calcium were measured in 2-h (morning) fasting and 5-h postbeverage urine specimens. Relative to water, urinary calcium rose significantly only with the milks and the 2 caffeine-containing beverages. The excess calciuria was approximately 0.25 mmol, about the same as previously reported for caffeine alone. Phosphoric acid without caffeine produced no excess calciuria; nor did it augment the calciuria of caffeine. The excess calciuria associated with consumption of carbonated beverages is confined to caffeinated beverages. Acidulant type has no acute effect. Because the caffeine effect is known to be compensated for by reduced calciuria later in the day, we conclude that the net effect of carbonated beverage constituents on calcium economy is negligible. The skeletal effects of carbonated beverage consumption are likely due primarily to milk displacement.

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

    Directory of Open Access Journals (Sweden)

    Stefano Goffredo

    Full Text Available 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.

  6. Absence of rebound effect with calcium carbonate.

    Science.gov (United States)

    Simoneau, G

    1996-01-01

    This was an open, randomised balance cross-over study in 12 healthy male volunteers. The antacid activity of calcium carbonate plus magnesium carbonate (Rennie and hydrotalcite (Talcid), given in the recommended dose of 2 tablets 4 times daily, were compared using 24 h intragastric measurement of pH. The volunteers received 2 tablets of calcium carbonate plus magnesium carbonate or hydrotalcite according to a randomised order 1 h after each meal and at bedtime. Results showed that both treatments have similar antacid efficacy and a similar duration of action of about one hour. There was no evidence of acid 'rebound' following either treatment during the second and third hours following the administration of antacid.

  7. The Thermal Decomposition of Calcium Carbonate

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The thermogravimetry(TG) and derivative thermogravimetry(DTG) curves of the thermal decomposition reaction of calcium carbonate have been measured at five different heating rates. The kinetic parameters and the reaction mechanism of the reaction were evaluated from analysis of the TG and DTG curves by using the Ozawa method, the combined integral and differential methods and the reduced equations derived by us.

  8. 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

  9. Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    Han Wang; Wenlai Huang; Yongsheng Han

    2013-01-01

    Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering.If we look at crystallization at the atomic level,crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice.Diffusion can be a rate determining step for the growth of crystals.In this paper,we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced.The diffusion effect is studied in a specially designed three-cell reactor.Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concentration gradient in the reaction cell,thus promoting the formation of cubic calcite particles.The reaction rate is regulated by temperature.Increase of reaction rate favors the formation of needle-like aragonite particles.When diffusion and reaction play joint roles in the reaction system,their compromise dominates the formation of products,leading to a mixture of cubic and needle-like particles with a controllable ratio.Since diffusion and reaction are universal factors in the preparation of materials,the finding of this paper could be helpful in the controlled synthesis of other materials.

  10. Preparation and Characterization of Calcium Carbonate Nanoparticles

    Science.gov (United States)

    Hassim, Aqilah; Rachmawati, Heni

    2010-10-01

    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 this study, we prepared and characterized calcium carbonate nanoparticle to improve the solubility by using bottom-up method. The experiment was done by titrating calcium chloride with sodium carbonate with the addition of polyvinylpyrrolidone (PVP) as stabilizer, using ultra-turrax. Various concentrations of calcium chloride and sodium carbonate as well as various speed of stirring were used to prepare the calcium carbonate nanoparticles. Evaluations studied were including particle size, polydispersity index (PI) and zeta potential with particle analyzer, surface morphology with scanning electron microscope, and saturated solubility. In addition, to test the ability of PVP to prevent particles growth, short stability study was performed by storing nano CaCO3 suspension at room temperature for 2 weeks. Results show that using 8000 rpm speed of stirring, the particle size tends to be bigger with the range of 500-600 nm (PI between 0.2-0.4) whereas with stirring speed of 4000 rpm, the particle size tends to be smaller with 300-400 nm (PI between 0.2-0.4). Stirring speed of 6000 rpm produced particle size within the range of 400-500 nm (PI between 0.2-0.4). SEM photograph shows that particles are monodisperse confirming that particles were physically stable without any agglomeration within 2 weeks storage. Taken together, nano CaCO3 is successfully prepared by bottom-up method and PVP is a good stabilizer to prevent the particle growth.

  11. Elucidating the Effect of Biomolecule Structure on Calcium Carbonate Crystal Formation

    Science.gov (United States)

    Kulbok, K. E.; Duckworth, O.

    2011-12-01

    Anthropogenic emissions of carbon dioxide have lead to a steady increase in atmospheric concentration. This greenhouse gas has been identified as a key driver of climate change and also has lead to increased acidification of marine and terrestrial waters. Calcium carbonate precipitation at the Earth's surface is an integral linkage in the global carbon cycle, especially in regards to regulating atmospheric carbon dioxide. As concern for the effect of increasing atmospheric CO2 levels grows, the need to understand calcium carbonate systems escalates concurrently. Calcium carbonate phases are the most abundant group of biominerals; therefore, elucidating the mechanism of biomineralization is critical to understanding CaCO3 precipitation and may aid in the development of novel carbon sequestration strategies. The ubiquity of microorganisms leads to an extensive number of biomolecules present in the Earth's systems, and thus an extensive range of possible effects on CaCO3 formation. Carboxylic acids are very common biomolecules and have a relatively simple structure, thus making them an ideal family of model compounds. This study examines the kinetics, thermodynamics, phase, and morphology of calcium carbonate crystals precipitated in the presence of carboxylate-containing biomolecules, including citric acid, succinic acid, and aspartic acid. The experiments utilize a unique (NH4)2CO3 gas-diffusion reactor, which allows in-situ measurements of chemical conditions during the precipitation and growth of crystals. Continuous monitoring of the in-situ conditions of pCO2, pH, [Ca2+], and optical absorbance provides data on the supersaturation at which nucleation occurs and the kinetics of mineral growth. The use of scanning electron microscopy and X-ray diffraction provides information on the morphology and mineralogy of precipitates. The combination of these data sets will provide an in-depth view of the ideal concentration of calcium ions required for solution saturation

  12. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  13. Local solid phase growth of few-layer graphene on silicon carbide from nickel silicide supersaturated with carbon

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo-Cousin, Enrique; Vassilevski, Konstantin; Hopf, Toby; Wright, Nick; O' Neill, Anthony; Horsfall, Alton; Goss, Jonathan [School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom); Cumpson, Peter [School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2013-03-21

    Patterned few-layer graphene (FLG) films were obtained by local solid phase growth from nickel silicide supersaturated with carbon, following a fabrication scheme, which allows the formation of self-aligned ohmic contacts on FLG and is compatible with conventional SiC device processing methods. The process was realised by the deposition and patterning of thin Ni films on semi-insulating 6H-SiC wafers followed by annealing and the selective removal of the resulting nickel silicide by wet chemistry. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to confirm both the formation and subsequent removal of nickel silicide. The impact of process parameters such as the thickness of the initial Ni layer, annealing temperature, and cooling rates on the FLG films was assessed by Raman spectroscopy, XPS, and atomic force microscopy. The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 4 monolayers for initial Ni layers between 3 and 20 nm thick. Self-aligned contacts were formed on these patterned films by contact photolithography and wet etching of nickel silicide, which enabled the fabrication of test structures to measure the carrier concentration and mobility in the FLG films. A simple model of diffusion-driven solid phase chemical reaction was used to explain formation of the FLG film at the interface between nickel silicide and silicon carbide.

  14. Evaluation of quick disintegrating calcium carbonate tablets.

    Science.gov (United States)

    Fausett, H; Gayser, C; Dash, A K

    2000-07-02

    The purpose of this investigation was to develop a rapidly disintegrating calcium carbonate (CC) tablet by direct compression and compare it with commercially available calcium tablets. CC tablets were formulated on a Carver press using 3 different forms of CC direct compressed granules (Cal-Carb 4450, Cal-Carb 4457, and Cal-Carb 4462). The breaking strength was measured using a Stokes-Monsanto hardness tester. The disintegration and dissolution properties of the tablets were studied using USP methodology. The calcium concentration was determined by an atomic absorption spectrophotometer. Scanning electron microscopy was used to evaluate the surface topography of the granules and tablets. Breaking strength of Cal-Carb 4450, Cal-Carb 4457, and Cal-Carb 4462 tablets was in the range of 7.2 to 7.7 kg, as compared with a hardness of 6.2 kg and 10 kg for the commercially available calcium tablets Citracal and Tums, respectively. The disintegration time for the tablets presented in the order earlier was 4.1, 2.1, 1.9, 2.9, and 9.7 minutes, respectively. The dissolution studies showed that all formulations released 100% of the elemental calcium in simulated gastric fluid in less than 20 minutes. In summary, this study clearly demonstrated that quick disintegrating CC tablets can be formulated without expensive effervescence technology.

  15. Carbonation of calcium aluminate cement pastes

    Directory of Open Access Journals (Sweden)

    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.

  16. Carbon supersaturation due to paraequilibrium carburization: Stainless steels with greatly improved mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Michal, G.M. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail: gmm3@case.edu; Ernst, F. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail: frank.ernst@case.edu; Kahn, H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail: harold.kahn@case.edu; Cao, Y. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States); Oba, F. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States); Agarwal, N. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail: heuer@case.edu

    2006-04-15

    Low-temperature gas-phase carburization has been used to generate very high surface interstitial carbon contents, up to {approx}12 at.%, in a 316L austenitic stainless steel. The high interstitial content leads to substantial surface hardening (Vickers hardness of {approx}12 GPa, equivalent to Rockwell C of {approx}71.5) with essentially no loss of ductility and with no carbide formation. Residual compressive stresses accompanying the low-temperature carburization enhance the high-cycle fatigue resistance, while the hardening enhances the wear resistance. These remarkable improvements in mechanical properties arise because the carburization is carried out at temperatures where 'paraequilibrium', rather than conventional thermodynamic equilibrium, determines the phase composition; paraequilibrium can be realized under conditions where substitutional solutes such as Cr and Ni are immobile whereas interstitial solutes such as carbon are not.

  17. Apatite Formation from Amorphous Calcium Phosphate and Mixed Amorphous Calcium Phosphate/Amorphous Calcium Carbonate.

    Science.gov (United States)

    Ibsen, Casper J S; Chernyshov, Dmitry; Birkedal, Henrik

    2016-08-22

    Crystallization from amorphous phases is an emerging pathway for making advanced materials. Biology has made use of amorphous precursor phases for eons and used them to produce structures with remarkable properties. Herein, we show how the design of the amorphous phase greatly influences the nanocrystals formed therefrom. We investigate the transformation of mixed amorphous calcium phosphate/amorphous calcium carbonate phases into bone-like nanocrystalline apatite using in situ synchrotron X-ray diffraction and IR spectroscopy. The speciation of phosphate was controlled by pH to favor HPO4 (2-) . In a carbonate free system, the reaction produces anisotropic apatite crystallites with large aspect ratios. The first formed crystallites are highly calcium deficient and hydrogen phosphate rich, consistent with thin octacalcium phosphate (OCP)-like needles. During growth, the crystallites become increasingly stoichiometric, which indicates that the crystallites grow through addition of near-stoichiometric apatite to the OCP-like initial crystals through a process that involves either crystallite fusion/aggregation or Ostwald ripening. The mixed amorphous phases were found to be more stable against phase transformations, hence, the crystallization was inhibited. The resulting crystallites were smaller and less anisotropic. This is rationalized by the idea that a local phosphate-depletion zone formed around the growing crystal until it was surrounded by amorphous calcium carbonate, which stopped the crystallization.

  18. Comparative absorption of calcium from carbonate tablets, lactogluconate/carbonate effervescent tablet, and chloride solution.

    Science.gov (United States)

    Ekman, M; Reizenstein, P; Teigen, S W; Rønneberg, R

    1991-01-01

    Intestinal absorption of calcium from three different labelled calcium preparations (all containing 500 mg elemental calcium) was determined using the whole body retention and urinary excretion of 47Ca in 14 normal subjects. Chewable calcium carbonate tablets showed a significantly (p less than 0.05) better mean minimum absorption of calcium (25.6% in exp. I, 22.8% in exp. II) than calcium given in the form of a lactogluconate/carbonate effervescent tablet, (17%), but similar to calcium in a chloride solution (24.7%). The minimum calcium absorption varied from 85 to 128 mg. All the preparations were taken with standardized low calcium test meals.

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

    Science.gov (United States)

    Jones, Elizabeth M.; Fenton, Mairi; Meredith, Michael P.; Clargo, Nicola M.; Ossebaar, Sharyn; Ducklow, Hugh W.; Venables, Hugh J.; de Baar, Hein J. W.

    2017-05-01

    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 carbonate minerals calcite and aragonite was observed in Ryder Bay, in the coastal sea-ice zone of the West Antarctic Peninsula. Glacial meltwater and melting sea ice stratified the water column and facilitated the development of large phytoplankton blooms and subsequent strong uptake of atmospheric CO2 of up to 55 mmol m-2 day-1 during austral summer. Concurrent high pH (8.48) and calcium carbonate mineral supersaturation (Ωaragonite 3.1) occurred in the meltwater-influenced surface ocean. Biologically-induced increases in calcium carbonate mineral saturation states counteracted any effects of carbonate ion dilution. Accumulation of CO2 through remineralisation of additional organic matter from productive coastal waters lowered the pH (7.84) and caused deep-water corrosivity (Ωaragonite 0.9) in regions impacted by Circumpolar Deep Water. Episodic mixing events enabled CO2-rich subsurface water to become entrained into the surface and eroded seasonal stratification to lower surface water pH (8.21) and saturation states (Ωaragonite 1.8) relative to all surface waters across Ryder Bay. Uptake of atmospheric CO2 of 28 mmol m-2 day-1 in regions of vertical mixing may enhance the susceptibility of the surface layer to future ocean acidification in dynamic coastal environments. Spatially-resolved studies are essential to elucidate the natural variability in carbonate chemistry in order to better understand and predict carbon cycling and the response of marine organisms to future ocean acidification in the Antarctic coastal zone.

  20. Growth of the calcium carbonate polymorph vaterite in mixtures of water and ethylene glycol at conditions of gas processing

    Science.gov (United States)

    Flaten, Ellen Marie; Seiersten, Marion; Andreassen, Jens-Petter

    2010-03-01

    Long subsea tie-ins for transportation of moist gas and condensate require corrosion and hydrate control. The combination of alkalinity for corrosion mitigation and monoethylene glycol (MEG) for hydrate inhibition strongly affects the tolerance for produced formation water. The elevated alkalinity downstream of the injection point increases the risk of carbonate formation. Calcium carbonate is the most common precipitate at such conditions. Our previous findings (Flaten et al., 2009) [1] show that MEG governs calcium carbonate precipitation and promotes formation of the metastable polymorph vaterite. This paper describes crystal growth of vaterite in mixed MEG water solvent with 0-70 wt% MEG at temperatures of 40 and 70 °C in solutions with high calcium to carbonate ratios representative of the production conditions. Results of some experiments in solutions with stoichiometric amounts of the reactants are included for comparison. The growth rate of vaterite can be described by second-order kinetics in most of the investigated supersaturation range. The growth order is lower at high MEG contents and high calcium concentrations when the carbonate activity is reduced in order to maintain comparable supersaturation values. It is then probable that the low carbonate activity makes the reaction diffusion limited. MEG reduces the growth rate constant of vaterite when the reaction is second order. Increasing the MEG concentration from 0 to 50 wt%, decreases the growth rate constant kr from 1.9 to 0.7 nm/s at 40 °C and from 2.6 to 1.2 nm/s at 70 °C. The growth reduction can be explained by a change of either de-hydration or diffusion rate along the surface when the ions are incorporated into the crystal lattice. Further investigations into which of the two mechanisms that is rate determining is outside the scope of this work.

  1. Effect of dietary moisture and sodium content on urine composition and calcium oxalate relative supersaturation in healthy miniature schnauzers and labrador retrievers.

    Science.gov (United States)

    Stevenson, A E; Hynds, W K; Markwell, P J

    2003-04-01

    The aim of this series of studies was to evaluate two possible feeding strategies as methods for reducing the risk of calcium oxalate (CaOx) formation in two breeds of healthy dog. The studies compared the effect of dietary moisture (Study 1) and dietary sodium (Na), (Study 2) on urine composition of labrador retrievers (LR) and miniature schnauzers (MS). A nutritionally complete dry dog food was fed to 16 dogs (eight LR, eight MS; Study 1) and 15 dogs (seven LR, eight MS; Study 2) for 24 days (Study 1), or 36 days (Study 2). The dogs were fed the diet alone (7% moisture, 0.06 g Na/100 kcal), or supplemented with deionised water to 73% moisture (Study 1), or dietary Na, to deliver 0.20 or 0.30 g Na per 100 kcal (Study 2). Urine pH, volume, specific gravity, and concentrations of 12 analytes were measured for each dog. Urinary relative supersaturations (RSS) with CaOx were calculated from these values. The effects of supplemental Na or water were established using t tests (Study 1) or analysis of variance, and multiple range tests (least significant difference) (Study 2); Phigh moisture diet may reduce the risk of CaOx formation in high-risk breeds. Increasing dietary Na led to production of urine with a significantly lower CaOx RSS in both breeds, indicating that sodium supplementation to dry diet formats may reduce the risk of CaOx formation. These feeding strategies should be considered when evaluating methods for preventing CaOx formation within high-risk groups.

  2. Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

    Science.gov (United States)

    Komar, Nemanja; Zeebe, Richard

    2016-04-01

    Negative carbon and calcium isotope excursions, as well as climate shifts, took place during the most severe mass extinction event in Earth's history, the end-Permian (˜252 Ma). Investigating the connection between carbon and calcium cycles during transient carbon cycle perturbation events, such as the end-Permian, may help resolve the intricacies between the coupled calcium-carbon cycles, as well as provide a tool for constraining the causes of mass extinction. Here, we identify the deficiencies of a simplified calcium model employed in several previous studies and we demonstrate the importance of a fully coupled carbon-cycle model when investigating the dynamics of carbon and calcium cycling. Simulations with a modified version of the LOSCAR model, which includes a fully coupled carbon-calcium cycle, indicate that increased weathering rates and ocean acidification (potentially caused by Siberian Trap volcanism) are not capable of producing trends observed in the record, as previously claimed. Our model results suggest that combined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the cessation of biological carbon export, and variable calcium isotope fractionation (due to a change in the seawater carbonate ion concentration) represents a more plausible scenario. This scenario successfully reconciles δ13C and δ44Ca trends observed in the sediment record, as well as the proposed warming of >6oC.

  3. [Formulation of calcium carbonate tablets with various binding substances].

    Science.gov (United States)

    Gazikalović, E; Obrenović, D; Nidzović, Z; Toskić-Radojicić, M

    1996-01-01

    The test results of calcium carbonate tablets, made of different binding substances (microcrystal cellulose, gelatin, 7pp sodium carboxymethylcellulose and starch) were presented. The content of calcium-carbonate in tablets as well as varying, solidity, prodigality and aptness to decay was determined. The best properties were observed in tablets made with starch.

  4. Calcium D-saccharate

    DEFF Research Database (Denmark)

    Garcia, André Castilho; Hedegaard, Martina Vavrusova; Skibsted, Leif Horsfelt

    2016-01-01

    K-1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d......-saccharate becomes spontaneously supersaturated with both d-gluconate and d-saccharate calcium salts, from which only calcium d-saccharate slowly precipitates. Calcium d-saccharate is suggested to act as a stabilizer of supersaturated solutions of other calcium hydroxycarboxylates with endothermic complex formation...

  5. Heat mass transfer model of fouling process of calcium carbonate on heat transfer surface

    Institute of Scientific and Technical Information of China (English)

    QUAN ZhenHua; CHEN YongChang; MA ChongFang

    2008-01-01

    A new heat mass transfer model was developed to predict the fouling process of calcium carbonate on heat transfer surface.The model took into account not only the crystallization fouling but also the particle fouling which was formed on the heat transfer surface by the suspension particles of calcium carbonate in the su-persaturated solution.Based on experimental results of the fouling process,the deposition and removal rates of the mixing fouling were expressed.Furthermore,the coupling effect of temperature with the fouling process was considered in the physics model.As a result the fouling resistance varying with time was obtained to describe the fouling process and the prediction was compared with experimental data under same conditions.The results showed that the present model could give a good prediction of fouling process,and the deviation was less than 15% of the experimental data in most cases.The new model is credible to predict the fouling process.

  6. Increased calcium absorption from synthetic stable amorphous calcium carbonate: Double-blind randomized crossover clinical trial in post-menopausal women

    Science.gov (United States)

    Calcium supplementation is a widely recognized strategy for achieving adequate calcium intake. We designed this blinded, randomized, crossover interventional trial to compare the bioavailability of a new stable synthetic amorphous calcium carbonate (ACC) with that of crystalline calcium carbonate (C...

  7. SECONDARY HYPERPARATHYROIDISM AFTER BARIATRIC SURGERY: TREATMENT IS WITH CALCIUM CARBONATE OR CALCIUM CITRATE?

    Science.gov (United States)

    BARETTA, Giorgio Alfredo Pedroso; CAMBI, Maria Paula Carlini; RODRIGUES, Arieli Luz; MENDES, Silvana Aparecida

    2015-01-01

    Background : Bariatric surgery, especially Roux-en-Y gastric bypass, can cause serious nutritional complications arising from poor absorption of essential nutrients. Secondary hyperparathyroidism is one such complications that leads to increased parathyroid hormone levels due to a decrease in calcium and vitamin D, which may compromise bone health. Aim : To compare calcium carbonate and calcium citrate in the treatment of secondary hyperparathyroidism. Method : Patients were selected on the basis of their abnormal biochemical test and treatment was randomly done with citrate or calcium carbonate. Results : After 60 days of supplementation, biochemical tests were repeated, showing improvement in both groups. Conclusion : Supplementation with calcium (citrate or carbonate) and vitamin D is recommended after surgery for prevention of secondary hyperparathyroidism. PMID:26537273

  8. The effect of brushing with nano calcium carbonate and calcium carbonate toothpaste on the surface roughness of nano-ionomer

    Science.gov (United States)

    Anisja, D. H.; Indrani, D. J.; Herda, E.

    2017-08-01

    Nanotechnology developments in dentistry have resulted in the development of nano-ionomer, a new restorative material. The surface roughness of restorative materials can increase bacteria adhesion and lead to poor oral hygiene. Abrasive agents in toothpaste can alter tooth and restorative material surfaces. The aim of this study is to identify the effect of brushing with nano calcium carbonate, and calcium carbonate toothpaste on surface roughness of nano-ionomer. Eighteen nano-ionomer specimens were brushed with Aquabidest (doubledistilled water), nano calcium carbonate and calcium carbonate toothpaste. Brushing lasted 30 minutes, and the roughness value (Ra) was measured after each 10 minute segment using a surface roughness tester. The data was analyzed using repeated ANOVA and one-way ANOVA test. The value of nano-ionomer surface roughness increased significantly (p<0.05) after 20 minutes of brushing with the nano calcium carbonate toothpaste. Brushing with calcium carbonate toothpaste leaves nano-ionomer surfaces more rugged than brushing with nano calcium carbonate toothpaste.

  9. Urea hydrolysis and calcium carbonate reaction fronts

    Science.gov (United States)

    Fox, D. T.; Redden, G. D.; Henriksen, J.; Fujita, Y.; Guo, L.; Huang, H.

    2010-12-01

    The mobility of toxic or radioactive metal contaminants in subsurface environments can be reduced by the formation of mineral precipitates that form co-precipitates with the contaminants or that isolate them from the mobile fluid phase. An engineering challenge is to control the spatial distribution of precipitation reactions with respect to: 1) the location of a contaminant, and 2) where reactants are introduced into the subsurface. One strategy being explored for immobilizing contaminants, such as Sr-90, involves stimulating mineral precipitation by forming carbonate ions and hydroxide via the in situ, microbially mediated hydrolysis of urea. A series of column experiments have been conducted to explore how the construction or design of such an in situ reactant production strategy can affect the temporal and spatial distribution of calcium carbonate precipitation, and how the distribution is coupled to changes in permeability. The columns were constructed with silica gel as the porous media. An interval midway through the column contained an adsorbed urease enzyme in order to simulate a biologically active zone. A series of influent solutions were injected to characterize hydraulic properties of the column (e.g., bromide tracer), profiles of chemical conditions and reaction products as the enzyme catalyzes urea hydrolysis (e.g., pH, ammonia, urea), and changes that occur due to CaCO3 precipitation with the introduction of a calcium+urea solutions. In one experiment, hydraulic conductivity was reduced as precipitate accumulated in a layer within the column that had a higher fraction of fine grained silica gel. Subsequent reduction of permeability and flow (for a constant head condition) resulted in displacement of the hydrolysis and precipitation reaction profiles upstream. In another experiment, which lacked the physical heterogeneity (fine grained layer), the precipitation reaction did not result in loss of permeability or flow velocity and the reaction profile

  10. Synthesis of calcium hydroxyapatite from calcium carbonate and different orthophosphate sources: A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Pham Minh, Doan, E-mail: doan.phamminh@mines-albi.fr [Universite de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Lyczko, Nathalie; Sebei, Haroun; Nzihou, Ange [Universite de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Sharrock, Patrick [Universite de Toulouse, SIMAD, IUT Paul Sabatier, Avenue Georges Pompidou, 81104 Castres (France)

    2012-08-01

    Highlights: Black-Right-Pointing-Pointer Calcium hydroxyapatite was synthesized from CaCO{sub 3} and four orthophosphates. Black-Right-Pointing-Pointer Only H{sub 3}PO{sub 4} led to the complete precipitation of orthophosphate species. Black-Right-Pointing-Pointer H{sub 3}PO{sub 4} was also the most efficient for calcium dissolution. Black-Right-Pointing-Pointer Reaction pathway was dissolution-precipitation accompanied by agglomeration step. - Abstract: The synthesis of calcium hydroxyapatite (Ca-HA) starting from calcium carbonate and different orthophosphate sources, including orthophosphoric acid, potassium, sodium and ammonium dihydrogen orthophosphates, was investigated under ambient conditions. The reaction started with calcium carbonate dissolution in an acid medium, followed by rapid precipitation of calcium cations with orthophosphate species to form calcium phosphate based particles which were in the size range of 0.4-1 {mu}m. These particles then agglomerated into much larger ones, up to 350 {mu}m in diameter (aggregates). These aggregates possessed an unstable porous structure which was responsible for the porosity of the final products. The highest specific surface area and pore volume were obtained with potassium dihydrogen orthophosphate. On the other hand, orthophosphoric acid led to the highest dissolution of calcium carbonate and the complete precipitation of orthophosphate species. Under ambient conditions, calcium phosphate based solid products of low crystallinity were formed. Different intermediates were identified and a reaction pathway proposed.

  11. Crystal growth and morphology of calcium oxalates and carbonates

    NARCIS (Netherlands)

    Heijnen, W.M.M.

    1986-01-01

    The main purpose of the research described in this thesis is to establish a relationship between the crystal structure and morphology of calcium oxalate and calcium carbonate crystals grown from aqueous solutions. Starting point is the PBC (Periodic Bond Chain) theory formulated by Hartman and Perdo

  12. Kinetics of the Carbonate Leaching for Calcium Metavanadate

    Directory of Open Access Journals (Sweden)

    Peiyang Shi

    2016-10-01

    Full Text Available The sodium salt roasting process was widely used for extracting vanadium due to its high yield rate of vanadium. However, the serious pollution was a problem. The calcium roasting process was environmentally friendly, but the yield rate of vanadium was relatively lower. Focusing on the calcium metavanadate produced in the calcium roasting process of vanadium minerals, the mechanism of the carbonate leaching for calcium metavanadate and its leaching kinetics of calcium metavanadate were studied. With the increase of the leaching agent content, the decrease of the particle size, the increase of the temperature and the increase of the reaction time, the leaching rate of vanadium increased, and the constant of reaction rate increased. In the carbonate leaching process, the calcium carbonate was globular and attached to the surface of calcium metavanadate. In the solution containing bicarbonate radical, lots of cracks formed in the dissolution process. However, the cracks were relatively fewer in the solution containing carbonate. In the present study, the carbonate leaching for calcium metavanadate was controlled by diffusion, the activation energy reached maximum and minimum in the sodium bicarbonate and the sodium carbonate solution, respectively. The activation energy value in the ammonium bicarbonate solution was between those two solutions. The kinetic equations of the carbonate leaching for calcium metavanadate were as follows: 1 − 2/3η − (1 − η2/3 = 4.39[Na2CO3]0.75/r0 × exp(−2527.06/Tt; 1 − 2/3η − (1 − η2/3 = 7.89[NaHCO3]0.53/r0 × exp(−2530.67/Tt; 1 − 2/3η − (1 − η2/3 = 6.78[NH4HCO3]0.69/r0 × exp(−2459.71/Tt.

  13. Calcium carbonate scaling in seawater desalination by ammonia-carbon dioxide forward osmosis: Mechanism and implications

    KAUST Repository

    Li, Zhenyu

    2015-02-07

    Forward osmosis (FO) is an osmotically driven membrane process, where the membrane separates a draw solution (DS) with high salinity from a feed solution (FS) with low salinity. There can be a counter direction flow of salt (i.e., salt leakage) that may interact with the water flux through the FO membrane. For the first time reported, this study describes a new calcium carbonate scaling phenomenon in the seawater FO desalination process using ammonium bicarbonate as the DS. The scaling on the membrane surface at the feed side is caused by the interaction between an anion reversely diffused from the DS and a cation present in the FS, causing a significant decline of the water flux. The composition of the scaling layer is dominated by the solubility (represented as solubility product constant, Ksp) of salt formed by the paired anion and cation. Membrane surface morphology plays a crucial role in the reversibility of the scaling. If the scaling occurs on the active layer of the FO membrane, hydraulic cleaning (increasing crossflow velocity) efficiency to restore the water flux is up to 82%. When scaling occurs on the support layer of the FO membrane, the hydraulic cleaning efficiency is strongly reduced, with only 36% of the water flux recovered. The present study reveals the risk of scaling induced by the interaction of feed solute and draw solute, which is different from the scaling caused by the supersaturation in reverse osmosis and other FO studies reported. The scaling investigated in this study can occur with a very low solute concentration at an early stage of the FO process. This finding provides an important implication for selection of draw solution and development of new membranes in the FO process.

  14. Amorphous calcium carbonate particles form coral skeletons

    Science.gov (United States)

    Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.; Gilbert, Pupa U. P. A.

    2017-09-01

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.

  15. Nanoparticle tracers in calcium carbonate porous media

    KAUST Repository

    Li, Yan Vivian

    2014-07-15

    Tracers are perhaps the most direct way of diagnosing subsurface fluid flow pathways for ground water decontamination and for natural gas and oil production. Nanoparticle tracers could be particularly effective because they do not diffuse away from the fractures or channels where flow occurs and thus take much less time to travel between two points. In combination with a chemical tracer they can measure the degree of flow concentration. A prerequisite for tracer applications is that the particles are not retained in the porous media as the result of aggregation or sticking to mineral surfaces. By screening eight nanoparticles (3-100 nm in diameter) for retention when passed through calcium carbonate packed laboratory columns in artificial oil field brine solutions of variable ionic strength we show that the nanoparticles with the least retention are 3 nm in diameter, nearly uncharged, and decorated with highly hydrophilic polymeric ligands. The details of these column experiments and the tri-modal distribution of zeta potential of the calcite sand particles in the brine used in our tests suggests that parts of the calcite surface have positive zeta potential and the retention of negatively charged nanoparticles occurs at these sites. Only neutral nanoparticles are immune to at least some retention. © 2014 Springer Science+Business Media.

  16. Improving the compaction properties of roller compacted calcium carbonate.

    Science.gov (United States)

    Bacher, C; Olsen, P M; Bertelsen, P; Kristensen, J; Sonnergaard, J M

    2007-09-05

    The effects of roller compaction process parameters, morphological forms of calcium carbonate and particle size of sorbitol on flow, compaction and compression properties were investigated. The morphology of the calcium carbonate and the sorbitol particle size were more influential on the compaction properties than the settings of the roller compactor. The roller compaction process was demonstrated to be robust and stable in regard to flowability and compactibility. The flowability of the granules was improved adequately to facilitate compression in a production scale rotary tablet press. By adding sorbitol to the calcium carbonate, the compressibility - characterized by the Walker coefficient W(ID) - and the compactibility C(P) were improved considerably. A correlation between the consolidation characteristics was demonstrated. Compactibility data from the compaction simulator correlated with the tablet press for two of the calcium carbonates, the cubic form and the ground quality.

  17. The production of precipitated calcium carbonate from industrial gypsum wastes

    CSIR Research Space (South Africa)

    De Beer, Morris

    2014-05-01

    Full Text Available Precipitated calcium carbonate is a material of great interest due to its large range of applications. Although there are extensive reserves of limestone worldwide, very few deposits are of sufficient quality to provide raw materials for specialised...

  18. 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.

  19. Fortification of all-purpose wheat-flour tortillas with calcium lactate, calcium carbonate, or calcium citrate is acceptable.

    Science.gov (United States)

    Romanchik-Cerpovicz, Joelle E; McKemie, Rebecca J

    2007-03-01

    Fortification helps provide adequate nutrients for individuals not meeting daily needs. Foods may be fortified with calcium to assist individuals with lactose intolerance and others preferring not to consume traditional forms of dairy. This study examined the quality of all-purpose wheat-flour tortillas fortified with calcium lactate, calcium carbonate, or calcium citrate. These tortillas were compared to similarly prepared nonfortified flour tortillas (control) and commercial nonfortified flour tortillas. Calcium-fortified tortillas contained 114 mg elemental calcium per standard serving (48 g tortilla), an 8.6-fold increase compared to nonfortified tortillas. Moisture contents and rollabilities of all tortillas were similar. Consumers (N=87) evaluated each tortilla in duplicate using a hedonic scale and reported liking the appearance, texture, flavor, aftertaste, and overall acceptability of all tortillas. However, the appearance of control tortillas was preferred over commercial tortillas (P<0.01), whereas the aftertaste of commercial tortillas or those fortified with calcium carbonate was preferred over the control (P<0.05). Despite these differences, consumers were equally willing to purchase both fortified and nonfortified tortillas, suggesting that appearance and aftertaste may not influence willingness to purchase. Overall, this study shows that fortification of flour tortillas with various forms of calcium is a feasible alternative calcium source.

  20. An automatic system for crystal growth studies at constant supersaturation

    Science.gov (United States)

    March, J. G.; Costa-Bauzá, A.; Grases, F.; Söhnel, O.

    1992-01-01

    An automatic system for growing crystals from seeded supersaturated solutions at constant supersaturation is described. Control of burettes and data acquisition are controlled by computer. The system was tested with a study of the calcium oxalate kinetics of crystal growth. PMID:18924950

  1. 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 E; McCabe, George P; Moe, Sharon M; Weaver, Connie M; Peacock, Munro

    2013-05-01

    Patients with chronic kidney disease (CKD) are given calcium carbonate to bind dietary phosphorus, reduce phosphorus retention, and prevent negative calcium balance; however, data are limited on calcium and phosphorus balance during CKD to support this. Here, we studied eight patients with stage 3 or 4 CKD (mean estimated glomerular filtration rate 36 ml/min) who received a controlled diet with or without a calcium carbonate supplement (1500 mg/day calcium) during two 3-week balance periods in a randomized placebo-controlled cross-over design. All feces and urine were collected during weeks 2 and 3 of each balance period and fasting blood, and urine was collected at baseline and at the end of each week. Calcium kinetics were determined using oral and intravenous (45)calcium. Patients were found to be in neutral calcium and phosphorus balance while on the placebo. Calcium carbonate supplementation 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 soft-tissue deposition. Fasting blood and urine biochemistries of calcium and phosphate homeostasis were unaffected by calcium carbonate. Thus, the positive calcium balance produced by calcium carbonate treatment within 3 weeks cautions against its use as a phosphate binder in patients with stage 3 or 4 CKD, if these findings can be extrapolated to long-term therapy.

  2. Calcium acetate versus calcium carbonate as phosphorus binders in patients on chronic haemodialysis: a controlled study.

    Science.gov (United States)

    Ring, T; Nielsen, C; Andersen, S P; Behrens, J K; Sodemann, B; Kornerup, H J

    1993-01-01

    The first reported double-blind cross-over comparison between the phosphorus binders calcium carbonate and calcium acetate was undertaken in 15 stable patients on chronic maintenance haemodialysis. Detailed registration of diet and analysis of the protein catabolic rate suggested an unchanged phosphorus intake during the study. It was found that predialytic serum phosphate concentration was significantly decreased by 0.11 mmol/l (0.34 mg/dl) (P = 0.021, 95% confidence limits 0.02-0.21 mmol/l; 0.06-0.65 mg/dl) during calcium acetate treatment. The calcium phosphate product was insignificantly decreased during treatment with calcium acetate whereas we could not exclude the possibility that calcium concentration had increased.

  3. A mixed flow reactor method to synthesize amorphous calcium carbonate under controlled chemical conditions.

    Science.gov (United States)

    Blue, Christina R; Rimstidt, J Donald; Dove, Patricia M

    2013-01-01

    This study describes a new procedure to synthesize amorphous calcium carbonate (ACC) from well-characterized solutions that maintain a constant supersaturation. The method uses a mixed flow reactor to prepare ACC in significant quantities with consistent compositions. The experimental design utilizes a high-precision solution pump that enables the reactant solution to continuously flow through the reactor under constant mixing and allows the precipitation of ACC to reach steady state. As a proof of concept, we produced ACC with controlled Mg contents by regulating the Mg/Ca ratio of the input solution and the carbonate concentration and pH. Our findings show that the Mg/Ca ratio of the reactant solution is the primary control for the Mg content in ACC, as shown in previous studies, but ACC composition is further regulated by the carbonate concentration and pH of the reactant solution. The method offers promise for quantitative studies of ACC composition and properties and for investigating the role of this phase as a reactive precursor to biogenic minerals.

  4. 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.

  5. 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

  6. Preparation and Characterization of a Calcium Carbonate Aerogel

    Directory of Open Access Journals (Sweden)

    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.

  7. [Does carbonate originate from carbonate-calcium crystal component of the human urinary calculus?].

    Science.gov (United States)

    Yuzawa, Masayuki; Nakano, Kazuhiko; Kumamaru, Takatoshi; Nukui, Akinori; Ikeda, Hitoshi; Suzuki, Kazumi; Kobayashi, Minoru; Sugaya, Yasuhiro; Morita, Tatsuo

    2008-09-01

    It gives important information in selecting the appropriate treatment for urolithiasis to confirm the component of urinary calculus. Presently component analysis of the urinary calculus is generally performed by infrared spectroscopy which is employed by companies providing laboratory testing services in Japan. The infrared spectroscopy determines the molecular components from the absorption spectra in consequence of atomic vibrations. It has the drawback that an accurate crystal structure cannot be analyzed compared with the X-ray diffraction method which analyzes the crystal constituent based on the diffraction of X-rays on crystal lattice. The components of the urinary calculus including carbonate are carbonate apatite and calcium carbonate such as calcite. Although the latter is reported to be very rare component in human urinary calculus, the results by infrared spectroscopy often show that calcium carbonate is included in calculus. The infrared spectroscopy can confirm the existence of carbonate but cannot determine whether carbonate is originated from carbonate apatite or calcium carbonate. Thus, it is not clear whether calcium carbonate is included in human urinary calculus component in Japan. In this study, we examined human urinary calculus including carbonate by use of X-ray structural analysis in order to elucidate the origin of carbonate in human urinary calculus. We examined 17 human calculi which were reported to contain calcium carbonate by infrared spectroscopy performed in the clinical laboratory. Fifteen calculi were obtained from urinary tract, and two were from gall bladder. The stones were analyzed by X-ray powder method after crushed finely. The reports from the clinical laboratory showed that all urinary culculi consisted of calcium carbonate and calcium phosphate, while the gallstones consisted of calcium carbonate. But the components of all urinary calculi were revealed to be carbonate apatite by X-ray diffraction. The components of

  8. Calcium acetate or calcium carbonate for hyperphosphatemia of hemodialysis patients: a meta-analysis.

    Directory of Open Access Journals (Sweden)

    Yong Wang

    Full Text Available High levels of serum phosphorus both at baseline and during follow-up are associated with increased mortality in dialysis patients, and administration of phosphate binders was independently associated with improved survival among hemodialysis population. Calcium-based phosphate binders are the most commonly used phosphate binders in developing countries for their relatively low costs.To compare the efficacy and safety between calcium carbonate and calcium acetate in the treatment of hyperphosphatemia in hemodialysis patients.PubMed, EMBASE, Cochrane Library, Google scholar and Chinese databases (Wanfang, Weipu, National Knowledge Infrastructure of China were searched for relevant studies published before March 2014. Reference lists of nephrology textbooks and review articles were checked. A meta-analysis of randomized controlled trials (RCTs and quasi-RCTs that assessed the effects and adverse events of calcium acetate and calcium carbonate in adult patients with MHD was performed using Review Manager 5.0.A total of ten studies (625 participants were included in this meta-analysis. There was insufficient data in all-cause mortality and cardiovascular events for meta-analysis. Compared with calcium carbonate group, the serum phosphorus was significantly lower in calcium acetate group after4 weeks' administration (MD -0.15 mmol/L, 95% CI -0.28 to -0.01 and after 8 weeks' administration (MD -0.25 mmol/L, 95% CI -0.40 to -0.11. There was no difference in serum calcium levels or the incidence of hypercalcemia between two groups at 4 weeks and 8 weeks. No statistical difference was found in parathyroid hormone (PTH levels or serum calcium by phosphorus (Ca x P product. There was significantly higher risk of intolerance with calcium acetate treatment (RR 3.46, 95% CI 1.48 to 8.26.For hyperphosphatemia treatment, calcium acetate showed better efficacy and with a higher incidence of intolerance compared with calcium carbonate. There are insufficient data

  9. Ultrasound influence upon calcium carbonate precipitation on bacterial cellulose membranes.

    Science.gov (United States)

    Stoica-Guzun, Anicuta; Stroescu, Marta; Jinga, Sorin; Jipa, Iuliana; Dobre, Tanase; Dobre, Loredana

    2012-07-01

    The effect of ultrasonic irradiation (40 kHz) on the calcium carbonate deposition on bacterial cellulose membranes was investigated using calcium chloride (CaCl(2)) and sodium carbonate (Na(2)CO(3)) as starting reactants. The composite materials containing bacterial cellulose-calcium carbonate were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and color measurements. The polymorphs of calcium carbonate that were deposited on bacterial cellulose membranes in the presence or in the absence of ultrasonic irradiation were calcite and vaterite. The morphology of the obtained crystals was influenced by the concentration of starting solutions and by the presence of ultrasonic irradiation. In the presence of ultrasonic irradiation the obtained crystals were bigger and in a larger variety of shapes than in the absence of ultrasounds: from cubes of calcite to spherical and flower-like vaterite particles. Bacterial cellulose could be a good matrix for obtaining different types of calcium carbonate crystals.

  10. Bioavailability of calcium supplements and the effect of Vitamin D: comparisons between milk, calcium carbonate, and calcium carbonate plus vitamin D.

    Science.gov (United States)

    Mortensen, L; Charles, P

    1996-03-01

    Our aim was to examine a regimen for calcium supplementation because various factors seem to be important for its bioavailability, and to examine the effect of adding vitamin D to the supplement. The participants were 20 healthy women aged 28-59 y (chi: 38 y). During the 3-d periods and 1 d before, the participants were consuming a calcium and energy-balanced diet as similar to their usual daily diet as possible. The study was designed as a randomized, placebo-controlled, partly blinded crossover study divided into four periods of 3 d each: 1) three tablets containing 1000 mg CaCO3/d, 2) three tablets containing 1000 mg CaCO3 plus 5 micrograms (200 IU) vitamin D/d, 3)1 L more milk than in the usual daily diet, and 4) three placebo tablets daily. Bioavailability of the different calcium-supplement regimens were evaluated by changes in 24-h urinary excretion of calcium, phosphate, and magnesium. A significant increase in urinary calcium excretion was found during all periods of supplementation compared with the placebo period (Pcalcium in the calcium carbonate period was not significantly higher that that in the milk period, but calcium carbonate plus vitamin D resulted in significantly higher calcium excretion compared with that in the milk period. We conclude that the examined calcium carbonate regimen is at least as good a calcium supplement as milk, and that addition of 600 IU vitamin D/d promptly resulted in an increase in urinary calcium excretion after an increase in calcium absorption, even in healthy women.

  11. 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...... on the bare surfaces, surfaces with an adsorbed oil layer, and surfaces after being exposed to aqueous salt solutions. This showed that the silica surface became more hydrophobic after oil adsorption, while the wettability of the calcium carbonate surface was not significantly changed by adsorption of an oil...... layer. A surface energy component analysis based on the acid base theory showed that oil adsorption on the surfaces depends upon apolar, acidic, and basic oil components of the crude oil and that the adsorbed oil components differ for adsorption to silica and calcium carbonate. Desorption of the crude...

  12. Reaction of Calcium Silicates with Carbon Dioxide and Water

    Science.gov (United States)

    1979-09-26

    for Ca3SiO5 to 22.9 kcal/mole for CaSiO3 . The reaction products were calcium carbonate (CaCO3) and a calcium silicate hydrate of variable...Ca3SiO5, beta-Ca2SiO4, and gamma-Ca2SiO4 if free water is present. Aragonite forms in the absence of free H2O and in the carbonation of CaSiO3 . The

  13. Effect of carbon fiber on calcium phosphate bone cement

    Institute of Scientific and Technical Information of China (English)

    戴红莲; 王欣宇; 黄健; 闫玉华; 李世普

    2004-01-01

    The calcium phosphate cement (α-TCP/TTCP) was reinforced with oxidation-treated carbon fibers. The effect of aspect ratio and content of carbon fiber on the compression strength and bending strength of the hardened body was discussed. The results show that the reinforcing effect is optimal as the aspect ratio is 375 and the additive amount is 0.3% (mass fraction). Under this condition, the compressive strength is increased by 55% (maximum 63.46 MPa), and the bending strength is nearly increased by 100% (maximum 11.95 MPa), respectively. However, if the additive quantity and aspect ratio are too high, the effect of the carbon fibers is limited because it can not be dispersed uniformly in the hardened body. The biological evaluation indicates that the calcium phosphate cement reinforced by carbon fibers has good biocompatibility.

  14. CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTACTORS

    Science.gov (United States)

    The rate of carbonate mineral dissolution from limestone was studied using a rotating disk apparatus and samples of limestone of varied composition. The purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. Th...

  15. Precipitation of calcium carbonate from a calcium acetate and ammonium carbamate batch system

    Science.gov (United States)

    Prah, J.; Maček, J.; Dražič, G.

    2011-06-01

    In this paper, we report a novel approach for preparing precipitated calcium carbonate using solutions of ammonium carbamate and calcium acetate as the sources of calcium and carbon dioxide, respectively. Two different concentrations of the starting solutions at three different temperatures (15, 25 and 50 °C) were used for the reaction. The influence of temperature and concentration on the polymorphism and the resulting morphology of calcium carbonate are discussed. The most important parameter for controlling a particular crystal structure and precipitate morphology were the concentrations of the initial solutions. When initial solutions with lower concentrations were used, the crystal form of the precipitate changed with time. Regardless the different polymorphism at different temperatures, after one day only the calcite form was detected in all samples, regardless of at which temperature the samples were prepared. At higher concentrations, pure vaterite or a mixture of vaterite and calcite were present at the beginning of the experiment. After one day, pure vaterite was found in the samples that were prepared at 15 and 25 °C. If calcium carbonate precipitated at 50 °C, the XRD results showed a mixture of calcite and vaterite regardless of the time at which the sample was taken. The morphology of calcium carbonate particles prepared at various conditions changed from calcite cubes to spherical particles of vaterite and aragonite needles. When a low starting concentration was used, the morphology at the initial stage was strongly affected by the temperature at which the experiments were conducted. However, after one day only, cubes were present in all cases at low initial concentrations. In contrast, at high concentrations spherical particles precipitated at all three temperatures at the beginning of the reaction. Spherical particles were made up from smaller particles. Over time, the size of the particles was diminishing due to their disintegration into

  16. Correlation between calcium carbonate content and emission characteristics of incense.

    Science.gov (United States)

    Yang, Chi-Ru; Lin, Ta-Chang; Chang, Feng-Hsiang

    2006-12-01

    In Taiwan and China, calcium carbonate is commonly added as a filler during incense production to lower the cost. This study has found an unexpected benefit for this practice: it reduces particulate emission. Nine types of the popular incense on the local market were chosen for this study. The calcium content in raw material incense was analyzed by inductively coupled plasma atomic emission spectrometry, followed by X-ray diffraction (XRD) spectroscopy. The correlation between the calcium content and emission characteristics of incense was investigated. The calcium content varied from 1.8 to 60 mg/g (incense burned) among those nine different types of incense. Very little calcium (incense. Instead, most calcium was artificially added in the form of CaCO3 during manufacturing. The combustion characteristics, including burning rate, emission factors of particulate, ash, and solid-phase polycyclic aromatic hydrocarbons (S-PAHs), varied significantly among the nine types of incense. Incense containing 2% calcium would emit 30% less S-PAHs, compared with those with little (incense by approximately 50%.

  17. 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.

  18. Formate oxidation driven calcium carbonate precipitation by Methylocystis parvus OBBP

    NARCIS (Netherlands)

    Ganendra, G; De Muynck, W; Ho, A.; Arvaniti, EC; Hosseinkhani, B; Ramos, JA; Rahier, H; Boon, N.

    2014-01-01

    Microbially Induced Carbonate Precipitation (MICP) applied in the construction industry poses several disadvantages such as ammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented in this study to overcome these disadv

  19. Protein mapping of calcium carbonate biominerals by immunogold

    NARCIS (Netherlands)

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

    2007-01-01

    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

  20. Interfacial energies for heterogeneous nucleation of calcium carbonate on mica and quartz.

    Science.gov (United States)

    Li, Qingyun; Fernandez-Martinez, Alejandro; Lee, Byeongdu; Waychunas, Glenn A; Jun, Young-Shin

    2014-05-20

    Interfacial free energies often control heterogeneous nucleation of calcium carbonate (CaCO3) on mineral surfaces. Here we report an in situ experimental study of CaCO3 nucleation on mica (muscovite) and quartz, which allows us to obtain the interfacial energies governing heterogeneous nucleation. In situ grazing incidence small-angle X-ray scattering (GISAXS) was used to measure nucleation rates at different supersaturations. The rates were incorporated into classical nucleation theory to calculate the effective interfacial energies (α'). Ex situ Raman spectroscopy identified both calcite and vaterite as CaCO3 polymorphs; however, vaterite is the most probable heterogeneous nuclei mineral phase. The α' was 24 mJ/m(2) for the vaterite-mica system and 32 mJ/m(2) for the vaterite-quartz system. The smaller α' of the CaCO3-mica system led to smaller particles and often higher particle densities on mica. A contributing factor affecting α' in our system was the smaller structural mismatch between CaCO3 and mica compared to that between CaCO3 and quartz. The extent of hydrophilicity and the surface charge could not explain the observed CaCO3 nucleation trend on mica and quartz. The findings of this study provide new thermodynamic parameters for subsurface reactive transport modeling and contribute to our understanding of mechanisms where CaCO3 formation on surfaces is of concern.

  1. Para-amino benzoic acid–mediated synthesis of vaterite phase of calcium carbonate

    Indian Academy of Sciences (India)

    T N Ramesh; S A Inchara; K Pallavi

    2015-05-01

    Calcium carbonate polymorphs were precipitated at room temperature and 80°C by varying the precipitation pH, carbonate source, effect of solvent in presence and absence of structure directing agent such as para-aminobenzoic acid. Calcite phase of calcium carbonate was obtained when sodium hydrogen carbonate and/or sodium carbonate (used as precipitating agents) were added to calcium chloride solution at different pHs in water and/or methanol as solvent in separate experiments. Vaterite phase of calcium carbonate (CaCO3) has been synthesized by mixing calcium chloride and sodium carbonate in presence of para-aminobenzoic acid when water–methanol binary mixture was used as solvent. Vaterite phase of calcium carbonate crystallizes in P63/mmc, while that of calcite phase in R-3mc, respectively. Calcite phase of calcium carbonate exhibits rhombohedral morphology, while vaterite phase has spherical morphology.

  2. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Science.gov (United States)

    2010-07-01

    ... resulting from the production of calcium carbonate by the milk of lime process and by the recovery process... calcium carbonate production subcategory. 415.300 Section 415.300 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of...

  3. 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)

  4. Preliminary Nanosims Analysis of Carbon Isotope of Carbonates in Calcium-Aluminum-Rich Inclusions

    OpenAIRE

    Guan, Y.; Paque, J. M.; Burnett, D.S.; Eiler, J. M.

    2009-01-01

    Carbonate minerals observed in primitive meteorites are products of either terrestrial weathering or aqueous alteration in the early solar system. Most of the carbonate minerals in carbonaceous chondrites occur primarily as isolated grains in matrix, as crosscutting veins, or as replacement minerals in chondrules [e.g., 1, 2]. A few calcium-aluminum-rich inclusions (CAIs) have been reported containing carbonate minerals as well [2, 3]. The C and O isotopes of carbonates in c...

  5. Mechano-activated surface modification of calcium carbonate in wet stirred mill and its properties

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface modification of calcium carbonate particles using sodium stearate(SDS) as a modification agent incorporated with the simultaneous wet ultra-fine grinding in the laboratory stirred mill was investigated. The physical properties and application properties of modified calcium carbonate were measured and evaluated. The action mechanism between SDS and calcium carbonate in the modification was studied by infrared spectrometry(IR) and X-ray photoelectron energy spectroscopy(XPS). The results indicate that the crushing mechanic force intensity can obviously influence the modification effect of calcium carbonate because of mechano-chemical effect. The hydrophilic surface of calcium carbonate is turned into hydrophobic after modification. The properties of polyethylene(PE) filled by modified calcium carbonate powder is markedly improved. And the adsorption of SDS could occur by chemical reaction with calcium carbonate surface.

  6. Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature

    Directory of Open Access Journals (Sweden)

    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 

  7. Effect of some organic solvent-water mixtures composition on precipitated calcium carbonate in carbonation process

    Science.gov (United States)

    Konopacka-Łyskawa, Donata; Kościelska, Barbara; Karczewski, Jakub

    2015-05-01

    Precipitated calcium carbonate particles were obtained during carbonation of calcium hydroxide slurry with carbon dioxide. Aqueous solutions of isopropyl alcohol, n-butanol and glycerol were used as solvents. Concentration of organic additives in the reactive mixture was from 0% to 20% (vol). Precipitation process were performed in a stirred tank reactor equipped with gas distributor. Multimodal courses of particles size distribution were determined for produced CaCO3 particles. Calcium carbonate as calcite was precipitated in all experiments. The mean Sauter diameter of CaCO3 particles decreased when the concentration of all used organic additives increased. The amount of small particle fraction in the product increased with the increasing concentration of organic solvents. Similar physical properties of used liquid phase resulted in the similar characteristics of obtained particles.

  8. Biomaterial-Derived Calcium Carbonate Nanoparticles for Enteric Drug Delivery

    OpenAIRE

    Diane Render; Temesgen Samuel; Howard King; Madan Vig; Shaik Jeelani; Ramapuram Jayachandra Babu; Vijaya Rangari

    2016-01-01

    Oral drug delivery systems provide the most convenient, noninvasive, readily acceptable alternatives to parenteral systems. In the current work, eggshell-derived calcium carbonate (CaCO3) nanoparticles were used to develop enteric drug delivery system in the form of tablets. CaCO3 nanoparticles were manufactured using top-down ball-milling method and characterized by X-ray diffractometry (XRD) and transmission electron microscopy (TEM) and loaded with 5-fluorouracil as a model drug. Tablets w...

  9. Compactibility of agglomerated mixtures of calcium carbonate and microcrystalline cellulose.

    Science.gov (United States)

    Garzón Serra, María de Lourdes; Villafuerte Robles, Leopoldo

    2003-06-04

    The tablet tensile strength (T) of agglomerated mixtures of microcrystalline cellulose-Avicel PH 102 (MC), calcium carbonate (CC) and polyvinylpyrrolidone (Povidone, PVP), lubricated with magnesium stearate (MS), and formed under a compaction pressure (P(c)) ranging up to 618MPa has been determined. The compactibility was defined through: ln(-ln(1-T/T(max)))=Slope x lnP(c)+Intercept. MC/CC mixtures added of an agglutinant, before and after lubrication, show an important positive effect on their tablet tensile strength compared to a lineal relationship. This positive effect becomes smaller with decreasing compaction pressures. By different mixing methods, the higher the mixing efficiency the higher the compactibility, following the order: spray-dried>wet massing>tumble mixing. The compactibility of MC/CC/PVP spray-dried mixtures with calcium carbonate content from 20 to 60% was equal to or greater than that of pure microcrystalline cellulose. After lubrication with 2% MS the compactibility decreased, only the mixture with the maximal tablet tensile strength attained the tensile strength of pure microcrystalline cellulose. The presence of the binder, the lubricant and higher compaction pressures allow the accommodation of higher calcium carbonate proportions in the mixtures, at the maximal tablet tensile strength of the series. The lubricant decreases in a greater extent the compactibility of mixtures with a continuous phase of MC/PVP than that of CC/PVP. This is attributed to the plastic behavior of the MC/PVP continuous phase compared to a calcium carbonate continuous phase able to disrupt the Povidone and the possible lubricant coatings allowing a stronger interparticle interaction.

  10. Preparation of calcium carbonate particles coated with titanium dioxide

    Institute of Scientific and Technical Information of China (English)

    Hai Lin; Ying-bo Dong; Le-yong Jiang

    2009-01-01

    The preparation of a new mineral composite material, calcium carbonate particles coated with titanium dioxide, was stud-ied. The mechanism of the preparation process was proposed. The new mineral composite material was made by the mechanochemi-eal method under the optimum condition that the mass ratio of calcium carbonate particles to titanium dioxide was 6.5:3.5. The mass ratios of two different types of titanium dioxide (anatase to rutile) and grinding media to grinded materials were 8:2 and 4:1 respec-tively, and the modified density was 60%. Under this condition, the new material was capable of forming after 120-min modification.The hiding power and oil absorption of this new material were 29.12 g/m~2 and 23.30%, respectively. The results show that the modi-fication is based on surface hydroxylation. After coating with titanium dioxide, the hiding power of calcium carbonate can be im-proved greatly. The new mineral composite materials can be used as the substitute for titanium dioxide.

  11. Mechanical properties of polypropylene/calcium carbonate nanocomposites

    Directory of Open Access Journals (Sweden)

    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.

  12. Effect of Cationic and Anionic Surfactants on the Application of Calcium Carbonate Nanoparticles in Paper Coating

    CERN Document Server

    Barhoum, Ahmed; Abou-Zaied, Ragab Esmail; Rehan, Mohamed; Dufour, Thierry; Hill, Gavin; Dufresne, Alain

    2016-01-01

    Modification of calcium carbonate particles with surfactant significantly improves the properties of the calcium carbonate coating on paper. Unmodified and CTAB and oleate-modified calcium carbonate nanoparticles were prepared using the wet carbonation technique for paper coating. CTAB (cationic surfactant) and sodium oleate (anionic surfactant) were used to modify the size, morphology, and surface properties of the precipitated nanoparticles. The obtained particles were characterized by XRD, FT-IR spectroscopy, zeta potential measurements, TGA and TEM. Coating colors were formulated from the prepared unmodified and modified calcium carbonates and examined by creating a thin coating layer on reference paper. The effect of calcium carbonate particle size and surface modification on paper properties, such as coating thickness, coating weight, surface roughness, air permeability, brightness, whiteness, opacity, and hydrophobicity, were investigated and compared with GCC calcium carbonate-coated papers. The obtai...

  13. Randomized crossover study comparing the phosphate-binding efficacy of calcium ketoglutarate versus calcium carbonate in patients on chronic hemodialysis.

    Science.gov (United States)

    Bro, S; Rasmussen, R A; Handberg, J; Olgaard, K; Feldt-Rasmussen, B

    1998-02-01

    The objective of the study was to evaluate the phosphate-binding efficacy, side effects, and cost of therapy of calcium ketoglutarate granulate as compared with calcium carbonate tablets in patients on chronic hemodialysis. The study design used was a randomized, crossover open trial, and the main outcome measurements were plasma ionized calcium levels, plasma phosphate levels, plasma intact parathyroid hormone (PTH) levels, requirements for supplemental aluminum-aminoacetate therapy, patient tolerance, and cost of therapy. Nineteen patients on chronic hemodialysis were treated with a dialysate calcium concentration of 1.25 mmol/L and a fixed alfacalcidol dose for at least 2 months. All had previously tolerated therapy with calcium carbonate. Of the 19 patients included, 10 completed both treatment arms. After 12 weeks of therapy, the mean (+/-SEM) plasma ionized calcium level was significantly lower in the ketoglutarate arm compared with the calcium carbonate arm (4.8+/-0.1 mg/dL v 5.2+/-0.1 mg/dL; P = 0.004), whereas the mean plasma phosphate (4.5+/-0.3 mg/dL v 5.1+/-0.1 mg/dL) and PTH levels (266+/-125 pg/mL v 301+/-148 pg/mL) did not differ significantly between the two treatment arms. Supplemental aluminum-aminoacetate was not required during calcium ketoglutarate treatment, while two patients needed this supplement when treated with calcium carbonate. Five of 17 (29%) patients were withdrawn from calcium ketoglutarate therapy within 1 to 2 weeks due to intolerance (anorexia, vomiting, diarrhea, general uneasiness), whereas the remaining 12 patients did not experience any side effects at all. The five patients with calcium ketoglutarate intolerance all had pre-existing gastrointestinal symptoms; four of them had received treatment with cimetidine or omeprazol before inclusion into the study. Calculations based on median doses after 12 weeks showed that the cost of the therapy in Denmark was 10 times higher for calcium ketoglutarate compared with calcium

  14. New agent to treat elevated phosphate levels: magnesium carbonate/calcium carbonate tablets.

    Science.gov (United States)

    Meyer, Caitlin; Cameron, Karen; Battistella, Marisa

    2012-01-01

    In summary, Binaphos CM, a magnesium carbonate/calcium carbonate combination phosphate binder, is marketed for treating elevated phosphate levels in dialysis patients. Although studies using magnesium/calcium carbonate as a phosphate binder are short term with small numbers of patients, this phosphate binder has shown some promising results and may provide clinicians with an alternative for phosphate binding. Using a combination phosphate binder may reduce pill burden and encourage patient compliance. In addition to calcium and phosphate, it is imperative to diligently monitor magnesium levels in patients started on this medication, as magnesium levels may increase with longer duration of use. Additional randomized controlled trials are necessary to evaluate long-term efficacy and safety of this combination phosphate binder.

  15. Effect of calcium on adsorption capacity of powdered activated carbon.

    Science.gov (United States)

    Li, Gang; Shang, Junteng; Wang, Ying; Li, Yansheng; Gao, Hong

    2013-12-01

    We investigated the effect of calcium ion on the adsorption of humic acid (HA) (as a target pollutant) by powered activated carbon. The HA adsorption isotherms at different pH and kinetics of two different solutions including HA alone and HA doped Ca(2+), were performed. It was showed that the adsorption capacity of powdered activated carbon (PAC) for HA was markedly enhanced when Ca(2+) was doped into HA. Also, HA and Ca(2+) taken as nitrate were tested on the uptake of each other respectively and it was showed that the adsorbed amounts of both of them were significantly promoted when HA and calcium co-existed. Furthermore, the adsorbed amount of HA slightly decreased with the increasing of Ca(2+) concentration, whereas the amount of calcium increased with the increasing of HA concentration, but all above the amounts without addition. Finally, the change of pH before and after adsorption process is studied. In the two different solutions including HA alone and HA doped Ca(2+), pH had a small rise, but the extent of pH of later solution was bigger.

  16. Randomized crossover study comparing the phosphate-binding efficacy of calcium ketoglutarate versus calcium carbonate in patients on chronic hemodialysis

    DEFF Research Database (Denmark)

    Bro, S; Rasmussen, R A; Handberg, J

    1998-01-01

    The objective of the study was to evaluate the phosphate-binding efficacy, side effects, and cost of therapy of calcium ketoglutarate granulate as compared with calcium carbonate tablets in patients on chronic hemodialysis. The study design used was a randomized, crossover open trial, and the main...

  17. 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

  18. Conversion of calcium sulphide to calcium carbonate during the process of recovery of elemental sulphur from gypsum waste.

    Science.gov (United States)

    de Beer, M; Maree, J P; Liebenberg, L; Doucet, F J

    2014-11-01

    The production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste can be achieved by thermally reducing the waste into calcium sulphide (CaS), which is then subjected to a direct aqueous carbonation step for the generation of hydrogen sulphide (H2S) and CaCO3. H2S can subsequently be converted to elemental sulphur via the commercially available chemical catalytic Claus process. This study investigated the carbonation of CaS by examining both the solution chemistry of the process and the properties of the formed carbonated product. CaS was successfully converted into CaCO3; however, the reaction yielded low-grade carbonate products (i.e. 99 mass% as CaCO3) or precipitated calcium carbonate (PCC).

  19. The influence of polyaspartate additive on the growth and morphology of calcium carbonate crystals

    Science.gov (United States)

    Gower, Laurie Anne

    The addition of low levels of polyaspartate to a supersaturated calcium carbonate (CaCOsb3) solution leads to unusual morphologies in the inorganic phase. Spherulitic vaterite aggregates with helical protrusions, and distorted calcite crystals that contain spiral pits, have been produced. The helical particles are coated with an inorganic membrane that appears to be responsible for the helical twist. The polymer also causes deposition of thin CaCOsb3 tablets and films on the glass substrate. Two distinct types of films are deposited; the first is a mosaic of calcite crystals, and the second is spherulitic vaterite. In situ observations of the crystallization reaction have determined that the thin-film morphology is a result of the phase separation of a hydrated CaCOsb3/polymer liquid-precursor, whereby accumulation of isotropic droplets creates a coating on the substrate, and subsequent dehydration and crystallization yields birefringent CaCOsb3 films. During the amorphous to crystalline transition, incremental growth steps lead to "transition bars" and sectored calcite tablets. This in vitro system was originally modeled after certain aspects of CaCOsb3 biomineralization, in which the soluble proteins extracted from biominerals tend to have high levels of aspartic acid residues. Based on the similarities between features exhibited by the products of this system and those in biominerals, an argument has been presented to suggest that this polymer-induced liquid-precursor (PILP) process is involved in the morphogenesis of CaCOsb3 biominerals. These features include the following: thin CaCOsb3 tablets that grow laterally; tablets that express unstable crystallographic faces; non-faceted single crystals with curved surfaces; spatially-delineated single crystals; sectored calcite tablets; hollow-shell spheres; calcium carbonate cements; and magnesium-bearing calcites. This work has demonstrated that a means of morphological control can be accomplished through non

  20. Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction.

    Science.gov (United States)

    Combes, C; Bareille, R; Rey, C

    2006-11-01

    The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.

  1. 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

  2. A comparative study of calcium absorption following a single serving administration of calcium carbonate powder versus calcium citrate tablets in healthy premenopausal women

    Directory of Open Access Journals (Sweden)

    Haiyuan Wang

    2014-04-01

    Full Text Available Background: Calcium is an essential mineral often taken as a daily, long-term nutritional supplement. Data suggests that once-daily dosing is important with regard to long-term compliance of both drugs and nutritional supplements. Objective: This study was undertaken to compare the bioavailability of a single serving of two calcium supplements in healthy, premenopausal women. Design: A two-period, crossover bioavailability study of a single serving of calcium citrate tablets (two tablets=500 mg calcium versus a single serving of calcium carbonate powder (one packet of powder=1,000 mg calcium was performed in healthy women aged between 25 and 45. All subjects were on a calcium-restricted diet 7 days prior to testing and fasted for 12 h before being evaluated at 0, 1, 2, and 4 h after oral administration of the test agents. Blood measurements for total and ionized calcium and parathyroid hormone were performed and adverse events were monitored. Results: Twenty-three women were evaluable with a mean age of 33.2±8.71. Results showed that administration of a single serving of a calcium carbonate powder resulted in greater absorption in total and ionized calcium versus a single serving of calcium citrate tablets at 4 h (4.25±0.21 vs. 4.16±0.16, p=0.001. There were minimal side effects and no reported serious adverse events. Conclusions: This study shows that a single serving of a calcium carbonate powder is more bioavailable than a single serving of calcium citrate tablets. This may be beneficial for long-term compliance.

  3. Crystal structures of calcium hemicarboaluminate and carbonated calcium hemicarboaluminate from synchrotron powder diffraction data.

    Science.gov (United States)

    Runčevski, Tomče; Dinnebier, Robert E; Magdysyuk, Oxana V; Pöllmann, Herbert

    2012-10-01

    One of the main phases formed at the beginning of the carbonation reaction of cementitious building materials is the calcium hemicarboaluminate (abbreviated as Hc). This AFm (shorthand for hydrated calcium aluminate phases structurally related to hydrocalumite) phase was synthesized, crystallized and then studied by synchrotron X-ray powder diffraction and micro-Raman spectroscopy. At room temperature and standard experimental conditions two major cementitious phases were detected, the Hc phase (as a major phase) and carbonated calcium hemicarboaluminate (abbreviated as cHc). By increasing the temperature the Hc form transforms into cHc. The crystal structures of these important AFm phases were successfully solved and refined in the R3c space group of the trigonal crystal system. Hc has the unit-cell parameters a = 5.7757 (1) and c = 48.812 (2) Å, and cHc the unit-cell parameters a = 5.7534 (1) and c = 46.389 (1) Å. The two crystal structures are composed of positively charged main layers, [Ca(4)Al(2)(OH)(12)](2+), and negatively charged interlayers, [OH(2n)(CO(3))(1 - n)·4H(2)O](2-). The structure of the main layers is typical of the AFm family. Conversely, the interlayer region has a characteristic structure built up from water molecules and statistically distributed anions. In the interlayer, the Hc carbonate and hydroxyl anions are distributed in a 0.25:0.5 ratio, whereas the ratio of the anions in the cHc interlayers is 0.4:0.2.

  4. Epitaxial Relationships between Calcium Carbonate and Inorganic Substrates

    Directory of Open Access Journals (Sweden)

    Taewook Yang

    2014-09-01

    Full Text Available The polymorph-selective crystallization of calcium carbonate has been studied in terms of epitaxial relationship between the inorganic substrates and the aragonite/calcite polymorphs with implication in bioinspired mineralization. EpiCalc software was employed to assess the previously published experimental results on two different groups of inorganic substrates: aragonitic carbonate crystals (SrCO3, PbCO3, and BaCO3 and a hexagonal crystal family (α-Al2O3, α-SiO2, and LiNbO3. The maximum size of the overlayer (aragonite or calcite was calculated for each substrate based on a threshold value of the dimensionless potential to estimate the relative nucleation preference of the polymorphs of calcium carbonate. The results were in good agreement with previous experimental observations, although stereochemical effects between the overlayer and substrate should be separately considered when existed. In assessing the polymorph-selective nucleation, the current method appeared to provide a better tool than the oversimplified mismatch parameters without invoking time-consuming molecular simulation.

  5. Crystallization of Calcium Carbonate in a Large Scale Field Study

    Science.gov (United States)

    Ueckert, Martina; Wismeth, Carina; Baumann, Thomas

    2017-04-01

    The long term efficiency of geothermal facilities and aquifer thermal energy storage in the carbonaceous Malm aquifer in the Bavarian Molasse Basin is seriously affected by precipitations of carbonates. This is mainly caused by pressure and temperature changes leading to oversaturation during production. Crystallization starts with polymorphic nuclei of calcium carbonate and is often described as diffusion-reaction controlled. Here, calcite crystallization is favoured by high concentration gradients while aragonite crystallization is occurring at high reaction rates. The factors affecting the crystallization processes have been described for simplified, well controlled laboratory experiments, the knowledge about the behaviour in more complex natural systems is still limited. The crystallization process of the polymorphic forms of calcium carbonate were investigated during a heat storage test at our test site in the eastern part of the Bavarian Molasse Basin. Complementary laboratory experiments in an autoclave were run. Both, field and laboratory experiments were conducted with carbonaceous tap water. Within the laboratory experiments additionally ultra pure water was used. To avoid precipitations of the tap water, a calculated amount of {CO_2} was added prior to heating the water from 45 - 110°C (laboratory) resp. 65 - 110°C (field). A total water volume of 0.5 L (laboratory) resp. 1 L (field) was immediately sampled and filtrated through 10 - 0.1

  6. Effect of Ultrasonic on the Preparation of Nanometer Calcium Carbonate%超声波对纳米碳酸钙合成过程的影响

    Institute of Scientific and Technical Information of China (English)

    于福家; 王泽红; 韩跃新

    2011-01-01

    The principle and method of nanometer calcium carbonate preparation are introduced.Under the ultrasonic condition,the effects of initial carbonizing temperature,density of Ca(OH)2 and flow rate of CO2 on nanometer calcium carbonate synthesis are investigated.The results show that the ultrasonic can strengthen the nanometer calcium carbonate preparation,improve the efficiency of mass and heat transfer,greatly enhance the supersaturation of calcium ions in the solution and induce rapid and uniform nucleations of the calcium carbonate.Moreover,the initial carbonizing temperature can be enhanced about 5 ℃ because of ultrasonic,which can shorten the preparation time and improve the synthetic efficiency.On the basis of experimental investigation,the nanometer calcium carbonate powders with diameter of 20~30 nm were synthesized steadily under optimal process conditions in a homemade ultrasonic reactor.The results indicate that high-quality nanometer calcium carbonates with smaller and homogeneous size can be obtained by ultrasonic method.%介绍了纳米碳酸钙的制备原理和方法.探讨了在超声波存在条件下,初始碳化温度、Ca(OH)2乳液浓度、CO2流量对合成反应过程的影响.研究结果表明,超声波具有强化纳米碳酸钙合成反应过程的作用,能够改善反应体系的传质、传热效果,大大提高溶液中钙离子的过饱和度,诱导碳酸钙迅速均匀成核;在超声波的作用下,碳化过程的最高初始温度可以提高5℃,从而能够缩短合成反应时间,提高合成效率.在试验研究的基础上,利用自制的超声合成反应器,在最佳工艺条件下,稳定地制备出了20-30 nm的纳米碳酸钙粉体;实现了利用超声波进一步细化

  7. Calcium Carbonate Produced by Coccolithophorid Algae in Long Term, Carbon Dioxide Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    V.J. Fabry

    2007-06-30

    Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO2 through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids - single-celled, marine algae that are the major global producers of calcium carbonate - to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

  8. Calcium Carbonate Production by Coccolithophorid Alge in Long Term Carbon Dioxide Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    V. J. Fabry

    2006-09-30

    Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

  9. CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION

    Energy Technology Data Exchange (ETDEWEB)

    V.J. Fabry

    2004-10-30

    Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds or bioreactors to abate CO{sub 2} emissions from power plants.

  10. CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM CARBON DIOXIDE SEQUESTRATION

    Energy Technology Data Exchange (ETDEWEB)

    V. J. Fabry

    2003-10-30

    Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds or bioreactors to abate CO{sub 2} emissions from power plants.

  11. CALCIUM CARBONATE PRODUCTION BY COCCOLITHAPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION

    Energy Technology Data Exchange (ETDEWEB)

    V. J.Fabry

    2004-01-30

    Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

  12. CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION

    Energy Technology Data Exchange (ETDEWEB)

    V.J. Fabry

    2004-04-26

    Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids single-celled, marine algae that are the major global producers of calcium carbonate to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

  13. Preparation and properties of gluten/calcium carbonate composites

    Institute of Scientific and Technical Information of China (English)

    Min Zuo; Zheng Zheng Lai; Yi Hu Song; Qiang Zheng

    2008-01-01

    Environment friendly thermosetting composites were prepared by blending wheat gluten (WG) as matrix, calcium carbonate (CaCO3) as filler and glycerol as plasticizer followed by compression molding the mixture at 120 ℃ to crosslink the WG matrix. Morphology observation showed that the CaCO3 particles were finely dispersed in matrix. Incorporation of CaCO3 up to 10 wt% into the composites caused Young's modulus and tensile strength to increase markedly. On the other hand, the moisture absorption and elongation at break decreased slightly.

  14. Crystalline calcium carbonate and hydrogels as microenvironment for stem cells.

    Science.gov (United States)

    Astachov, Liliana; Nevo, Zvi; Aviv, Moran; Vago, Razi

    2011-01-01

    Stem cell development and fate decisions are dictated by the microenvironment in which the stem cell is embedded. Among the advanced goals of tissue engineering is the creation of a microenvironment that will support the maintenance and differentiation of the stem cell--based on embryonic and adult stem cells as potent, cellular sources--for a variety of clinical applications. This review discusses some of the approaches used to create regulatory and instructive microenvironments for the directed differentiation of mesenchymal stem cells (MSCs) using three-dimensional crystalline calcium carbonate biomaterials of marine origin combined with a hydrated gel based on hyaluronan.

  15. 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)

  16. [Use of domestically produced corn starch in the manufacture of calcium carbonate tablets].

    Science.gov (United States)

    Gazikalović, E; Obrenović, D; Nidzović, Z; Toskić-Radojicić, M

    1998-01-01

    The results of the testing of calcium carbonate tablets, compounded with starch as the binding and decay substance are presented. The content of calcium carbonate in the tablets, as well as the mass varying, solidity, prodigality and aptness to decay were determined. The best properties were observed in the tablets with 15% starch mucilage, added suddenly, in the whole amount, to the prepared mixture of calcium carbonate and lactose. This procedure is fast and simple, and compound tablets of calcium carbonate are of regulated quality.

  17. Regulation of Microstructure of Calcium Carbonate Crystals by Egg White Protein

    Institute of Scientific and Technical Information of China (English)

    ZHU Wen-kun; LUO Xue-gang; ZHANG Chi; DUAN Tao; ZHOU Jian

    2012-01-01

    Crystal growth of calcium carbonate in biological simulation was investigated via egg white protein with different volume fractions,during which calcium carbonate was synthesized by calcium chloride and sodium carbonate.The morphology,thermal properties and microstructure of the calcium carbonate micro-to-nanoscale crystals were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TG)and X-ray diffraction(XRD)analysis.The results show that the volume fraction of egg white protein has great influence on the shape,size and morphology of calcium carbonate crystals.The calcium carbonate crystals were the mixtures of calcite-vaterite-like crystals including spherical and rough surface,which are different from that formed in pure water.With the increase of egg white protein concentration,the diameter of calcium carbonate crystals changed,the amount of formed spherical calcium carbonate particles decreased and that of vaterite increased.These results indicate that the coordination and electrostatic interaction between egg white protein and Ca2+ significantly affect the calcium carbonate crystalization.

  18. Carbonate-containing apatite (CAP) synthesis under moderate conditions starting from calcium carbonate and orthophosphoric acid

    Energy Technology Data Exchange (ETDEWEB)

    Pham Minh, Doan, E-mail: doan.phamminh@mines-albi.fr [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Tran, Ngoc Dung; Nzihou, Ange [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Sharrock, Patrick [Université de Toulouse, SIMAD, IUT Paul Sabatier, Avenue Georges Pompidou, 81104 Castres (France)

    2013-07-01

    The synthesis of carbonate-containing apatite (CAP) from calcium carbonate and orthophosphoric acid under moderate conditions was investigated. In all cases, complete precipitation of orthophosphate species was observed. The reaction temperature influenced strongly the decomposition of calcium carbonate and therefore the composition of formed products. The reaction temperature of 80 °C was found to be effective for the complete decomposition of calcium carbonate particles after 48 h of reaction. Infra-red spectroscopy (IR), nuclear magnetic resonance (NMR), thermogravimetry/mass spectroscopy (TG–MS) coupling, and X-ray diffraction (XRD) characterizations allowed the identification of the composition of formed products. By increasing the reaction temperature from 20 °C to 80 °C, the content of A-type CAP increased and that of B-type CAP decreased, according to the favorable effect of temperature on the formation of A-type CAP. The total amount of carbonate content incorporated in CAP's structure, which was determined by TG–MS analysis, increased with the reaction temperature and reached up to 4.1% at 80 °C. At this temperature, the solid product was mainly composed of apatitic components and showed the typical flat-needle-like structure of CAP particles obtained in hydrothermal conditions. These results show an interesting one-step synthesis of CAP from calcium carbonate and orthophosphoric acid as low cost but high purity starting materials. Highlights: • The synthesis of carbonate-containing apatites from CaCO{sub 3} and H{sub 3}PO{sub 4} was studied. • The decomposition of CaCO{sub 3} particles was complete at 80 °C, 13.2 bar for 48 h. • The transformation of CaCO{sub 3} and H{sub 3}PO{sub 4} into apatitic products was also complete. • Pure carbonate-containing apatite was directly obtained without water-rising step.

  19. Non-aqueous formation of the calcium carbonate polymorph vaterite: astrophysical implications

    CERN Document Server

    Day, Sarah J; Parker, Julia E; Evans, Aneurin

    2013-01-01

    We study the formation of calcium carbonate, through the solid-gas interaction of amorphous Ca-silicate with gaseous CO2, at elevated pressures, and link this to the possible presence of calcium carbonate in a number of circumstellar and planetary environments. We use in-situ synchrotron X-Ray powder diffraction to obtain detailed structural data pertaining to the formation of the crystalline calcium carbonate phase vaterite and its evolution with temperature. We found that the metastable calcium carbonate phase vaterite was formed alongside calcite, at elevated CO2 pressure, at room temperature and subsequently remained stable over a large range of temperature and pressure. We report the formation of the calcium carbonate mineral vaterite whilst attempting to simulate carbonate dust grain formation in astrophysical environments. This suggests that vaterite could be a mineral component of carbonate dust and also presents a possible method of formation for vaterite and its polymorphs on planetary surfaces.

  20. Analysis of barium hydroxide and calcium hydroxide slurry carbonation reactors

    Energy Technology Data Exchange (ETDEWEB)

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

    1980-05-01

    The removal of CO/sub 2/ from air was investigated by using a continuous-agitated-slurry carbonation reactor containing either barium hydroxide (Ba(OH)/sub 2/) or calcium hydroxide (Ca(OH)/sub 2/). Such a process would be applied to scrub /sup 14/CO/sub 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)/sub 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)/sub 2/. Overall reaction mechanisms are postulated.

  1. 电磁场对碳酸钙反应结晶成核影响的研究%Research on the effect of electromagnetic field on calcium carbonate crystallization nucleation

    Institute of Scientific and Technical Information of China (English)

    王建国; 陆帅; 李松

    2014-01-01

    Based on the self-made experimental device used for measuring the critical supersaturation of CaCO3 so-lution,the effects of electromagnetic field action on the CaCO3 supersaturation and nucleation induction period has been studied by comparative tests with magnetism and without magnetism on calcium carbonate solution conductivi-ty-titration fluid volume. The influence of magnetic field effect on CaCO3 on the supersaturation and nucleation in-duction period is studied. The changes of CaCO3 supersaturation and nucleation induction period,under different frequencies and magnetic fields action,are observed. A large number of experimental results show that under the ac-tion of electromagnetic field,the supersaturation of CaCO3 decreases,nucleation speed increases,and nucleation in-duction period decreases.%基于自制CaCO3溶液临界过饱和度实验装置,通过测量加磁与未加磁对比实验的碳酸钙溶液电导率-滴定液容积,研究了电磁场作用对CaCO3过饱和度及成核诱导期的影响。在不同频率的电磁场作用下观察了CaCO3过饱和度及成核诱导期的变化,大量实验结果表明:在电磁场作用下,CaCO3的过饱和度减小,成核速率加快,成核诱导期减小。

  2. Scaling and Removal of Calcium Carbonate on Electroless Plating Surface

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The scaling process of calcium carbonate on a low-energy heat transfer surface-electroless plating surface was investigated in a simulated cooling water system. Owing to the very low surface energy, the electroless plating surface exhibited less scaling susceptibility. A longer induction period and a lower scaling rate were obtained on the low-energy surface compared to copper surface under identical conditions. The calcite particles obtained on the electroless plating surface during the induction period were larger in size than those on copper surface because fewer crystals formed and grew at the same time on the low-energy surface. With increasing surface temperature, the induction period reduced and the scaling rate increased for the low-energy surface. When initial surface temperature was fixed, an increase in fluid velocity would reduce the induction period and increase the scaling rate due to the diffusion effect. However, when the heat flux was fixed, an increase in fluid velocity would decrease the surface temperature, and lead to a longer induction period and a lower scaling rate. The removal experiments of calcium carbonate scale indicated that during post induction period, the detachment was not obvious, while during the induction period, apparent removal of crystal particles was obtained on the electroless plating surface owing to the weak adhesion force. The more frequently the transient high hydrodynamic force acted, the more the detached crystal particles were.

  3. Supersaturation in human gastric fluids.

    Science.gov (United States)

    Bevernage, Jan; Hens, Bart; Brouwers, Joachim; Tack, Jan; Annaert, Pieter; Augustijns, Patrick

    2012-05-01

    The current study reports on supersaturation, precipitation and excipient mediated precipitation inhibition of five poorly soluble drugs (loviride, glibenclamide, itraconazole, danazol, and etravirine) in human and simulated gastric fluids. Upon induction of supersaturation in human gastric fluids (HGFs), simulated gastric fluid (SGF), and fasted state simulated gastric fluid (FaSSGF) using a solvent shift method, supersaturation and precipitation were assessed as a function of time. In addition, the precipitation inhibitory capacity of three polymers (Eudragit® E PO, HPMC-E5, and PVP K25) was investigated. Supersaturation in human gastric fluids was observed for all model compounds, but proved to be relatively unstable (fast precipitation), except for itraconazole. Only modest excipient-mediated stabilizing effects on supersaturation were observed using HPMC-E5 and Eudragit® E PO whereas PVP K25 exerted no effect. In contrast to SGF, the observed precipitation behavior in FaSSGF was similar to the behavior in human gastric fluids. The present study demonstrates that supersaturation stability of drugs in human gastric fluids is in general inferior to supersaturation stability in intestinal fluids. As the potential for excipient mediated precipitation inhibition in gastric fluids was only limited, our data suggest that supersaturation should preferably be targeted to the intestine. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. DECOMPOSITION STUDY OF CALCIUM CARBONATE IN COCKLE SHELL

    Directory of Open Access Journals (Sweden)

    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.

  5. Onsite defluoridation system for drinking water treatment using calcium carbonate.

    Science.gov (United States)

    Wong, Elaine Y; Stenstrom, Michael K

    2017-08-28

    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.

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

    Science.gov (United States)

    Huang, Sherry; Chen, Jin Ching; Hsu, Chin Wei; Chang, Walter H.

    2009-09-01

    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-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.

  7. 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.

  8. Preparation of hardened body in calcium carbonate-aspartic acid-chitosan system by using amorphous calcium carbonate; Hishoshitsu tansan calcium wo genryo to suru tansan calcium-asuparaginsan-kitosankei kokatai no sakusei

    Energy Technology Data Exchange (ETDEWEB)

    Yasue, T.; Aigami, H.; Arai, Y. [Nihon University, Tokyo (Japan). Faculty of Science and Engineering

    1998-11-01

    Notice was given on chitosan to discuss fabrication of hardened body in calcium carbonate-aspartic acid-chitosan system. First, aspartic acid (Asp) was adsorbed into surface of amorphous calcium carbonate (ACC). Then, discussions were given on effects of water-solid mass ratio and chitosan amount on compressive strength of the hardened body in the calcium carbonate-chitosan system made by using a flow-in molding process. As a result, approximately the same compressive strength as that of calcium carbonate (calcite type) was obtained when anhydrous ACC as a product of ACC heated at 250 deg C is used as the raw material. Thus, the hardened body in calcium carbonate-aspartic acid-chitosan system was fabricated by using the Asp adsorbed anhydrous ACC as the starting material. The compressive strength decreased with increasing Asp adsorption amount. Therefore, a hardened body was fabricated by using compression molding at 10 MPa, rather than using the flow-in molding process. It was revealed from the results of infrared absorption spectroscopy that the compression molding strengthens the compounding of Asp chemically adsorbed on the ACC surface with chtosan, and improves the compression strength. 23 refs., 8 figs.

  9. 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

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

    Directory of Open Access Journals (Sweden)

    E.O. Mikhailova

    2016-09-01

    Full Text Available 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 and chemical properties. To obtain a product of prescribed quality the process of calcium carbonate deposition was performed of still waste liquid, that is the waste of calcium carbonate production and contain significant amount of calcium ions, and excessive production of the purified stock solution of sodium bicarbonate, which is composed of carbonate and hydrocarbonate ions. Results: The dependence of bulk density and specific surface area of calcium carbonate sediments and degree of deposition from such technological parameters are established: method of mixing the stock solutions, the concentration and molar ratio of reactants, temperature and reaction time. Conclusions: The optimal mode of deposition process is determined and the concept of production of calcium carbonate is developed. The quality of calcium carbonate meets the modern requirements of high dispersion, low bulk density and evolved specific surface of the product.

  11. 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...

  12. 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.

  13. Magnesium and occluded water in calcium carbonate monohydrate

    Science.gov (United States)

    Dejehet, F.; Idrissi, S.; Debuys, R.

    1999-04-01

    Calcium carbonate monohydrate spherulites (˜102 μm diameter) with different magnesium contents were synthesized from artificial seawater. Stable spherulites are only obtained if [Mg]/[Ca] ≥ 1-1.3 in the mother solution. Spherulites are surrounded by a skin of ˜15 μm thickness, about 5 times richer in Mg2+ than the bulk and which play a protective role from the stability viewpoint. Etching and crushing experiments were performed which confirm i.a. that the isotropic CO3- and CO2- radicals are located in the occluded water surrounding the constituent crystallites of the spherulites. Des sphérules de carbonate de calcium monohydraté de ˜102 μm de diamètre avec des teneurs en magnésium différentes ont été synthétisées à partir d'eau de mer artificielle. Des sphérules stables ne sont obtenues que si [Mg]/[Ca] ≥ 1-1.3 dans la solution mère. Les sphérules sont entourées d'une peau de ˜15 μm d'épaisseur, à peu près 5 fois plus riche en Mg2+ que la masse et qui assure sa stabilité. Des expériences de décapage et de broyage ont confirmé e.a. que les radicaux isotropes CO3- et CO2- sont localisés dans l'eau occluse entourant les cristallites à l'intérieur des sphérules.

  14. Co-precipitation of dissolved organic matter by calcium carbonate in Pyramid Lake, Nevada

    Science.gov (United States)

    Leenheer, Jerry A.; Reddy, Michael M.

    2008-01-01

    Our previous research has demonstrated that dissolved organic matter (DOM) influences calcium carbonate mineral formation in surface and ground water. To better understand DOM mediation of carbonate precipitation and DOM co-precipitation and/or incorporation with carbonate minerals, we characterized the content and speciation of DOM in carbonate minerals and in the lake water of Pyramid Lake, Nevada, USA. A 400-gram block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter not dissolved by acetic acid was removed by centrifugation. DOM from the carbonate rock was fractionated into nine portions using evaporation, dialysis, resin adsorption, and selective precipitations to remove acetic acid and inorganic constituents. The calcium carbonate rock contained 0.23% DOM by weight. This DOM was enriched in polycarboxylic proteinaceous acids and hydroxy-acids in comparison with the present lake water. DOM in lake water was composed of aliphatic, alicyclic polycarboxylic acids. These compound classes were found in previous studies to inhibit calcium carbonate precipitation. DOM fractions from the carbonate rock were 14C-age dated at about 3,100 to 3,500 years before present. The mechanism of DOM co-precipitation and/or physical incorporation in the calcium carbonate is believed to be due to formation of insoluble calcium complexes with polycarboxylic proteinaceous acids and hydroxy-acids that have moderately large stability constants at the alkaline pH of the lake. DOM co-precipitation with calcium carbonate and incorporation in precipitated carbonate minerals removes proteinaceous DOM, but nearly equivalent concentrations of neutral and acidic forms of organic nitrogen in DOM remain in solution. Calcium carbonate precipitation during lime softening pretreatment of drinking water may have practical applications for removal of proteinaceous disinfection by-product precursors.

  15. Calcium carbonate production response to future ocean warming and acidification

    Directory of Open Access Journals (Sweden)

    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 (ΩCaCO3 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 ΩCaCO3 (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

  16. Calcium carbonate production response to future ocean warming and acidification

    Directory of Open Access Journals (Sweden)

    A. J. Pinsonneault

    2011-12-01

    Full Text Available Anthropogenic carbon dioxide (CO2 emissions are acidifying the ocean, affecting calcification rates in pelagic organisms and thereby modifying the oceanic alkalinity cycle. 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. Meanwhile, 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 will ultimately increase or decrease the globally-integrated pelagic calcification rate. Here, we assess the importance of this uncertainty by introducing a variable dependence of calcium carbonate (CaCO3 production on calcite saturation state (ΩCaCO3 in the University of Victoria Earth System Climate Model, an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of this parameterization on global ocean carbon cycling under two CO2 emissions scenarios, both integrated to the year 3500. The simulations show a significant sensitivity of the vertical and surface horizontal alkalinity gradients to the parameterization, as well as the removal of alkalinity from the ocean through CaCO3 burial. These sensitivities result in an additional oceanic uptake of carbon when calcification depends on ΩCaCO3 (of up to 13 % of total carbon emissions, compared to the case where calcification is insensitive to acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500, a 13 % reduction in the amplitude of warming. Narrowing these uncertainties will require better understanding of both temperature and acidification effects on pelagic calcifiers. Preliminary examination suggests that

  17. Technological testing of calcium carbonate tablets for use in the treatment of renal osteodystrophy.

    Science.gov (United States)

    Dal Zotto, M; Ragazzi, E; Realdon, N; Dalla Fini, G

    1993-07-01

    Samples of calcium carbonate tablets produced by different manufacturers were subjected to various tests in order to evaluate tablet quality parameters, mostly indicative for calcium availability. Indications about tablet suitability for treatment of renal osteodystrophy in uremic patients were also tested. The disintegration test turned out to be the most useful in evaluating calcium carbonate availability from tablets. Samples from several manufacturers varied in their behaviour to disaggregation. The availability of calcium dissolved in gastric fluid and the extent of phosphorus binding appeared to depend on disintegration behaviour.

  18. Calcium carbonate corrosivity in an Alaskan inland sea

    Directory of Open Access Journals (Sweden)

    W. Evans

    2013-09-01

    Full Text Available Ocean acidification is the hydrogen ion increase caused by the oceanic uptake of anthropogenic CO2, and is a focal point in marine biogeochemistry, in part, because this chemical reaction reduces calcium carbonate (CaCO3 saturation states (Ω to levels that are corrosive (i.e. Ω ≤ 1 to shell-forming marine organisms. However, other processes can drive CaCO3 corrosivity; specifically, the addition of tidewater glacial melt. Carbonate system data collected in May and September from 2009 through 2012 in Prince William Sound (PWS, a semi-enclosed inland sea located on the south-central coast of Alaska that is ringed with fjords containing tidewater glaciers, reveal the unique impact of glacial melt on CaCO3 corrosivity. Initial limited sampling was expanded in September 2011 to span large portions of the western and central sound, and included two fjords proximal to tidewater glaciers: Icy Bay and Columbia Bay. The observed conditions in these fjords affected CaCO3 corrosivity in the upper water column (pCO2 well below atmospheric levels. CaCO3 corrosivity in glacial melt plumes is poorly reflected by pCO2 or pHT, indicating that either one of these carbonate parameters alone would fail to track Ω in PWS. The unique Ω and pCO2 conditions in the glacial melt plumes enhances atmospheric CO2 uptake, which, if not offset by mixing or primary productivity, would rapidly exacerbate CaCO3 corrosivity in a positive feedback. The cumulative effects of glacial melt and air-sea gas exchange are likely responsible for the seasonal widespread reduction of Ω in PWS; making PWS highly sensitive to increasing atmospheric CO2 and amplified CaCO3 corrosivity.

  19. Calcium Carbonate Crystal Growth in Porous Media, in the presence of Water Miscible and Non-Miscible Organic Fluids

    Science.gov (United States)

    Jaho, Sofia; Sygouni, Varvara; Paraskeva, Christakis A.

    2015-04-01

    reduced compared to the induction time where no oil phase was present. The interface of n-dodecane and supersaturated solutions seems to be very active and favored the formation of the CaCO3 crystalline enhancing the heterogeneous nucleation which generally demands a decreased energy barrier. Acknowledgments This research was partially funded by the European Union (European Social Fund-ESF) and Greek National Funds through the Operational Program "Education and Lifelong Learning" under the action Aristeia II (Code No4420). References 1. Merdhah A. B. and Yassin A. A., Scale formation in oil reservoir during water injection at high-salinity formation water, Journal of Applied Sciences, 7, 3198-3207 (2007). 2. Moghadasi J., Muller-Steinhagen H., Jamialahmadi M. and Sharif A., Model study on the kinetics of oil field formation damage due to salt precipitation from injection, Journal of Petroleum Science and Engineering, 43, 201-217 (2004). 3. Nancollas G. H. and Reddy M. M., The crystallization of calcium carbonate II. Calcite growth mechanism, Journal of Colloid and Interface Science, 37, 824-830 (1971).

  20. Controls of Polysaccharide Chemistry on the Kinetics and Thermodynamics of Heterogeneous Calcium Carbonate Nucleation

    Science.gov (United States)

    Giuffre, A. J.; Han, N.; Dove, P. M.

    2011-12-01

    Polysaccharide fibrils control the orientation of calcium carbonate (CaCO3) biominerals. Good examples are found in the multilayered extracellular mucilaginous sheath of green algae and cyanobacteria and in specialized vesicles inside coccolithophorids. More complex organisms such as arthropods and mollusks form biomineralized exoskeletons and shells that consist of insoluble polysaccharides and soluble acid-rich proteins. In these structures, CaCO3 mineral orientation occurs along fibers of the polysaccharide chitin. This raises the question of whether polysaccharide chemistry has specific roles in directing biomineralization. The last three decades of research show that acidic proteins influence CaCO3 polymorph selection, crystallographic orientation, and nucleation and growth rates but little is known about the function of polysaccharides. In fact, polysaccharides are long considered an inert component of organic frameworks. In this experimental investigation, we test the hypothesis that polysaccharides have chemistry-specific influences on calcification by measuring the kinetics of calcite nucleation onto three types of polysaccharide films under controlled solution compositions. Characterized polysaccharides of simple repeating monomer sequences were chosen as model compounds to represent the major carbohydrates seen in microbial and calcifying environments: 1) alginic acid with carboxyl groups, 2) hyaluronic acid with alternating carboxyl and acetylamine groups, and 3) chitosan with amine and acetylamine groups. Biosubstrates were prepared by electrodeposition of these compounds as thin gel-like films onto gold-coated silicon wafers. Using a flow-through cell, heterogeneous nucleation rates of calcite were measured for a suite of supersaturation conditions. These rate data were compared to similar measurements for carboxyl- and hydroxyl-terminated self-assembled monolayers. Calcite nucleation rates onto the three polysaccharides vary by a factor of 400x

  1. Calcium Carbonate Formation by Genetically Engineered Inorganic Binding Peptides

    Science.gov (United States)

    Gresswell, Carolyn Gayle

    Understanding how organisms are capable of forming (synthesize, crystallize, and organize) solid minerals into complex architectures has been a fundamental question of biomimetic materials chemistry and biomineralization for decades. This study utilizes short peptides selected using a cell surface display library for the specific polymorphs of calcium carbonate, i.e., aragonite and calcite, to identify two sets of sequences which can then be used to examine their effects in the formation, crystal structure, morphology of the CaCO3 minerals. A procedure of counter selection, along with fluorescence microscopy (FM) characterization, was adapted to insure that the sequences on the cells were specific to their respective substrate, i.e., aragonite or calcite. From the resulting two sets of sequences selected, five distinct strong binders were identified with a variety of biochemical characteristics and synthesized for further study. Protein derived peptides, using the known sequences of the proteins that are associated with calcite or aragonite, were also designed using a bioinformatics-based similarity analysis of the two sets of binders. In particular, an aragonite binding protein segment, AP7, a protein found in nacre, was chosen for this design and the resulting effects of the designed peptides and the AP7 were examined. Specifically, the binding affinities of the selected and the protein derived peptides off the cells were then tested using FM; these studies resulted in different binding characteristics of the synthesized and cellular bound peptides. Two of the peptides that displayed strong binding on the cells bound to neither of the CaCO 3 substrates and both the high and low similarity protein-derived peptides bound to both polymorphs. However, two of the peptides were found to only bind to their respective polymorph showing; these results are significant in that with this study it is demonstrated that the designed peptides based on experimental library

  2. Effect of calcium carbonate combined with calcitonin on hypercalcemia in hemodialysis patients.

    Science.gov (United States)

    Wei, Yong; Kong, Xiang Lei; Li, Wen Bin; Wang, Zun Song

    2014-12-01

    This short-term study assessed the efficacy and safety of calcium carbonate combined with calcitonin in the treatment of hypercalcemia in hemodialysis patients. Patients (n=64) on hemodialysis for chronic kidney disease for more than 6 months were included based on total serum calcium more than 10.5 mg/dL. All patients were randomized (1:1) to receive calcium carbonate combined with calcitonin (Group I) or lanthanum carbonate (Group II) for 12 weeks. Blood levels of calcium, phosphorus and intact parathyroid hormone (iPTH) were measured every month, bone mass density (BMD) and coronary artery calcium scores (CACS) were measured at 3 months. During the study period, serum calcium decreased from 10.72 ± 0.39 to 10.09 ± 0.28 mg/dL (P carbonate combined with calcitonin and lanthanum carbonate were equally effective in the suppression of hypercalcemia in hemodialysis patients. There were no serious treatment-related adverse events in treatment with calcium carbonate combined with calcitonin.

  3. Waste oil shale ash as a novel source of calcium for precipitated calcium carbonate: Carbonation mechanism, modeling, and product characterization

    Energy Technology Data Exchange (ETDEWEB)

    Velts, O., E-mail: olga.velts@ttu.ee [Laboratory of Inorganic Materials, Tallinn University of Technology, Ehitajate tee 5, Tallinn 19086 (Estonia); Laboratory of Separation Technology, Lappeenranta University of Technology, P.O. Box 20, Lappeenranta FI-53851 (Finland); Uibu, M.; Kallas, J.; Kuusik, R. [Laboratory of Inorganic Materials, Tallinn University of Technology, Ehitajate tee 5, Tallinn 19086 (Estonia)

    2011-11-15

    Highlights: {yields} A method for converting oil shale waste ash into precipitated CaCO{sub 3} is elucidated. {yields} We discuss the mechanism of hazardous alkaline ash leachates carbonation. {yields} We report a model describing precipitation of CaCO{sub 3} from multi-ionic ash leachates. {yields} Model enables simulation of reactive species concentration profiles. {yields} Product contained {approx}96% CaCO{sub 3} with 4-10 {mu}m size calcite or/and vaterite particles. - Abstract: In this paper, a method for converting lime-containing oil shale waste ash into precipitated calcium carbonate (PCC), a valuable commodity is elucidated. The mechanism of ash leachates carbonation was experimentally investigated in a stirred semi-batch barboter-type reactor by varying the CO{sub 2} partial pressure, gas flow rate, and agitation intensity. A consistent set of model equations and physical-chemical parameters is proposed to describe the CaCO{sub 3} precipitation process from oil shale ash leachates of complex composition. The model enables the simulation of reactive species (Ca{sup 2+}, CaCO{sub 3}, SO{sub 4}{sup 2-}, CaSO{sub 4}, OH{sup -}, CO{sub 2}, HCO{sub 3}{sup -}, H{sup +}, CO{sub 3}{sup 2-}) concentration profiles in the liquid, gas, and solid phases as well as prediction of the PCC formation rate. The presence of CaSO{sub 4} in the product may also be evaluated and used to assess the purity of the PCC product. A detailed characterization of the PCC precipitates crystallized from oil shale ash leachates is also provided. High brightness PCC (containing up to {approx}96% CaCO{sub 3}) with mean particle sizes ranging from 4 to 10 {mu}m and controllable morphology (such as rhombohedral calcite or coexisting calcite and spherical vaterite phases) was obtained under the conditions studied.

  4. Sobresaturacion urinaria del Oxalato de Calcio más alla de la Nefrolitiasis: La relación con el daño tubulointersticial Urinary calcium oxalate supersaturation beyond nephrolithiasis: Relationship with tubulointerstitial damage

    Directory of Open Access Journals (Sweden)

    J. E. Toblli

    2003-04-01

    Full Text Available Numerosos estudios han demostrado que el producto de la actividad iónica (PAI de oxalato de calcio (OxCa en la orina, como indicador de sobresaturación (SS urinaria, es mayor en pacientes formadores de cálculos que en sujetos normales. Más allá de la relación entre SS urinaria del OxCa y litogénesis, la exposición de OxCa al epitelio tubular puede ocasionar lesiones en la célula tubular y en el intersticio renal. Nuestro objetivo fue evaluar la posible relación entre SS urinaria de OxCa y el daño tubulointersticial (TI en un modelo animal de hiperoxaluria. Durante cuatro semanas, ratas Sprague-Dawley machos, divididas en dos grupos recibieron: grupo 1 Control [G1], (n= 8 agua, grupo 2 [G2], (n = 8 etilenglicol (ETG al 1% en el agua de beber. La SS urinaria de OxCa se valoró mediante el PAI del OxCa. Las lesiones TI se analizaron al finalizar el estudio por microscopía óptica e inmunohistoquímica. El G2 (ETG presentó valores mayores (pA number of studies have demonstrated that the urinary ion activity product (IAP of calcium oxalate (CaOx, as an index of urinary CaOx supersaturation (SS, is higher in renal stone formers than in normal subjects. Besides, the relation between CaOx SS and lithogenesis, crystal CaOx exposition can produce tubular cell as well as renal interstitial lesions. The aim of our study was to evaluate the possible relationship between CaOx SS and tubulointerstitial (TI damage in an animal model of hyperoxaluria. During four weeks, male Sprague-Dawley rats received: G1 (n=8 control regular water, and G2 (n= 8 1% ethylene glycol (ETG (precursor for oxalates in drinking water. In order to evaluate urinary CaOx SS, IAP assessed by Tisselius formula was performed. At the end of the study, renal lesions were evaluated by light microscopy and immunohistochemistry. Animals from G2 (ETG presented higher (p< 0.01 values of: a urinary oxalate excretion; b urinary CaOx SS; c crystalluria score; d proteinuria; and lower (p

  5. Polymer surface modification and characterization of particulate calcium carbonate fillers

    Energy Technology Data Exchange (ETDEWEB)

    Shui Miao

    2003-12-30

    The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of the treating agent. Here, the ultra-fine calcium carbonate is surface treated with 1, 2, 3 and 4 wt.% polyacrylic acid (PAA) synthesized by ourselves, which has strong ionic interaction and is an efficient surface modifier. The PAA coated filler is submitted to the measurement of the surface bonded amount, bonding efficacy, X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography. Maximum efficacy is expected at the monolayer coverage of the surface, which is about 0.6 wt.% according to the calculation based on the way they are aligned and is basically in agreement with the 'substrate overlayer' model based on the mole ratio of C{sup 286} and C{sup 290} taking no account of the possible underestimation because of the inaccuracy or because of the CH{sub x} contamination present originally on the CaCO{sub 3}. The initial decrease of the mole ratio of C{sup 290}/O and C{sup 290}/Ca with the surface bonded PAA may indicate that the bonding interaction between the polymer and the filler surface is the leaving of one molecular carbon dioxide. The IGC measurement shows that there is a considerable surface tension falling in the case of the PAA modified filler compared with the reference. An abnormal high surface energy in the case of filler treated with 4% PAA is observed.

  6. Studying the Propensity of Compounds to Supersaturate

    DEFF Research Database (Denmark)

    Palmelund, Henrik; Madsen, Cecilie Maria; Plum, Jakob;

    2016-01-01

    Supersaturating drug delivery systems can enhance the oral bioavailability of poorly soluble drug compounds. Supersaturation of such compounds has been studied in many different ways; however, a more standardized method is required. The rationale of choosing suitable concentrations of supersatura......Supersaturating drug delivery systems can enhance the oral bioavailability of poorly soluble drug compounds. Supersaturation of such compounds has been studied in many different ways; however, a more standardized method is required. The rationale of choosing suitable concentrations...... of supersaturation to study has previously been very inconsistent. This makes comparisons between studies and compounds difficult, as the propensity of compounds to supersaturate varies greatly. This study presents a standardized method to study the supersaturation of drug compounds. The method allows, both......, for a ranking of compounds according to their supersaturation propensity and the effectiveness of precipitation inhibitors. The time-concentration profile of supersaturation and precipitation was studied in situ for 4 different concentrations for 6 model compounds (albendazole, aprepitant, danazol, felodipine...

  7. 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 technical feasibility of calcium carbonate recovery and its use for pre-treatment of Acid Mine Drainage (AMD) from coal mines. The effect of key process parameters, such as the amount of acid (HCl/Calcium molar ratio), the pH and the CO2 flow rate were...

  8. Hyaluronan and calcium carbonate hybrid nanoparticles for colorectal cancer chemotherapy

    Science.gov (United States)

    Bai, Jinghui; Xu, Jian; Zhao, Jian; Zhang, Rui

    2017-09-01

    A hybrid drug delivery system (DDS) composed of hyaluronan and calcium carbonate (CC) was developed. By taking advantage of the tumor-targeting ability of hyaluronan and the drug-loading property of CC, the well-formed hyaluronan–CC nanoparticles were able to serve as a DDS targeting colorectal cancer with a decent drug loading content, which is beneficial in the chemotherapy of colorectal cancer. In this study, hyaluronan–CC nanoparticles smaller than 100 nm were successfully developed to load the wide-range anti-cancer drug adriamycin (Adr) to construct hyaluronan–CC/Adr nanoparticles. On the other hand, we also found that hyaluronan–CC/Adr nanoparticles can possibly increase the uptake ratio of Adr into HT29 colorectal cancer cells when compared with hyaluronan-free nanoparticles (CC/Adr) via the CD44 receptor-mediated endocytosis via competitive uptake and in vivo imaging assays. Note that both in vitro (CCK-8 assay on HT29 cells) and in vivo (anti-cancer assay on HT-29 tumor-bearing nude mice model) experiments revealed that hyaluronan–CC/Adr nanoparticles exhibited stronger anti-cancer activity than free Adr or CC/Adr nanoparticles with minimized toxic side effects and preferable cancer-suppression potential.

  9. Facile Synthesis of Calcium Carbonate Nanoparticles from Cockle Shells

    Directory of Open Access Journals (Sweden)

    Kh. Nurul Islam

    2012-01-01

    Full Text Available A simple and low-cost method for the synthesis of calcium carbonate nanoparticles from cockle shells was described. Polymorphically, the synthesized nanoparticles were aragonites which are biocompatible and thus frequently used in the repair of fractured bone and development of advanced drug delivery systems, tissue scaffolds and anticarcinogenic drugs. The rod-shaped and pure aragonite particles of 30±5 nm in diameter were reproducibly synthesized when micron-sized cockle shells powders were mechanically stirred for 90 min at room temperature in presence of a nontoxic and nonhazardous biomineralization catalyst, dodecyl dimethyl betaine (BS-12. The findings were verified using a combination of analytical techniques such as variable pressure scanning electron microscopy (VPSEM, transmission electron microscopy (TEM, Fourier transmission infrared spectroscopy (FT-IR, X-ray diffraction spectroscopy (XRD, and energy dispersive X-ray analyser (EDX. The reproducibility and low cost of the method suggested that it could be used in industry for the large scale synthesis of aragonite nanoparticles from cockle shells, a low cost and easily available natural resource.

  10. Biomaterial-Derived Calcium Carbonate Nanoparticles for Enteric Drug Delivery

    Directory of Open Access Journals (Sweden)

    Diane Render

    2016-01-01

    Full Text Available Oral drug delivery systems provide the most convenient, noninvasive, readily acceptable alternatives to parenteral systems. In the current work, eggshell-derived calcium carbonate (CaCO3 nanoparticles were used to develop enteric drug delivery system in the form of tablets. CaCO3 nanoparticles were manufactured using top-down ball-milling method and characterized by X-ray diffractometry (XRD and transmission electron microscopy (TEM and loaded with 5-fluorouracil as a model drug. Tablets with varying CaCO3 core and binder compositions were fabricated and coated with Eudragit S100 or Eudragit L100. Suitability for enteric delivery of the tablets was tested by oral administration to rabbits and radiography. Radiograph images showed that the tablet remained in the stomach of the rabbit for up to 3 hours. Further modifications of these biomaterial-derived nanoparticles and the coatings will enable manufacturing of stable formulations for slow or controlled release of pharmaceuticals for enteric delivery.

  11. Tribological properties of nanosized calcium carbonate filled polyamide 66 nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Itagaki, Kaito [Department of Mechanical Engineering, Graduate School of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 Japan (Japan); Nishitani, Yosuke [Department of Mechanical Engineering, Faculty of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo, 192-0015 Japan (Japan); Kitano, Takeshi [Polymer Centre, Faculty of Technology, Tomas Bata University in Zlin, T.G.M. 275, Zlin, 767 72 Czech Republic (Czech Republic); Eguchi, Kenichiro [Shiraishi Central Laboratories, 4-78 Motohama,Amagasaki,Hyogo,660-0085 Japan (Japan)

    2016-03-09

    For the purpose of developing high performance tribomaterials for mechanical sliding parts such as gears, bearings and so on, nanosized calcium carbonate (nano-CaCO{sub 3}) filled polyamide 66 (PA66) nanocomposites were investigated. The nano-CaCO{sub 3} was a kind of precipitated (colloid typed) CaCO{sub 3}, and its average particle size was 40, 80 and 150 nm. Surface treatment was performed by fatty acid on the nano-CaCO{sub 3} and its volume fraction in the nanocomposite was varied from 1 to 20vol.%. These nanocomposites were melt-mixed by a twin screw extruder and injection-molded. Tribological properties were measured by two types of sliding wear testers such as ring-on-plate type and ball-on-plate type one under dry condition. The counterface, worn surface and wear debris were observed by digital microscope and scanning electron microscope. It was found that the nano-CaCO{sub 3} has a good effect on the tribological properties, although the effect on the frictional coefficient and specific wear rate is differed by the volume fraction and the type of sliding wear modes. This is attributed to the change of wear mechanisms, which is the change of form of the transfer films on the counterface and the size of wear debris. It follows from these results that PA66/nano-CaCO{sub 3} nanocomposites may be possible to be the high performance tribomaterials.

  12. 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.

  13. Pacific Remote Islands MNM: Initial Survey Instructions for Calcium Carbonate Accretion

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The purpose of the survey is to quantify the rate of calcium carbonate accretion to the coral reef benthos and to examine spatial and temporal variability in...

  14. 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....

  15. Effects of aluminum hydroxide and calcium carbonate antacids on the bioavailability of ciprofloxacin.

    OpenAIRE

    Frost, R W; Lasseter, K C; Noe, A J; Shamblen, E C; Lettieri, J T

    1992-01-01

    This study was designed to determine the effects of an aluminum hydroxide antacid and a calcium carbonate antacid on the bioavailability of ciprofloxacin (Cipro). Cipro (750 mg) was administered orally to 12 healthy volunteers in a three-way randomized crossover design. The three treatments included Cipro alone, four 850-mg calcium carbonate tablets taken 5 min before Cipro, and three 600-mg aluminum hydroxide tablets taken 5 min before Cipro. The relative bioavailability of Cipro when given ...

  16. Biologically formed calcium carbonate, a durable plugging agent for enhanced oil recovery

    Energy Technology Data Exchange (ETDEWEB)

    Nemati, M. [University of Saskatchewan, Dept. of Chemical Engineering, Saskatoon, SK (Canada); Voordouw, G. [University of Calgary, Dept. of Biological Sciences, Calgary, AB (Canada)

    2004-02-01

    The use of bacterially precipitated inorganic compounds such as calcium carbonate and silica have been suggested as an effective method for selective plugging of reservoirs as a means to improve microscopic and volumetric sweep efficiencies within a given geological formation. In this paper controlled enzymatic and bacterial formation of calcium carbonate were studied using a purified urease enzyme and a bacterium isolated from a Canadian oil field. Results showed that the quantity of produced calcium carbonate in the presence of bacteria was dependent on urea concentration. The highest amount achieved was 15 g/L urea. Enzymatically, the maximum concentration of calcium carbonate was 2.6 times higher than that achieved in the presence of bacteria (57.6 g/L vs 21.5 g/L). The production of calcium carbonate appeared to be less sensitive to temperature in the presence of bacteria, whereas production rates were enhanced with the urease enzyme as the temperature was increased from 20 degrees C to 50 degrees C. Plugging studies in unconsolidated porous media and in a core-flooding system with Beria sandstone indicated that in situ formation of calcium carbonate could effectively decrease the permeability of the porous media. Nevertheless, it should be noted that plugging by biomass is not permanent, and permeabilities will increase as degradation of bacterial cells progresses. 5 refs., 4 tabs., 1 fig.

  17. 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}.

  18. Calcite Supersaturation and Precipitation Kinetics in the Lower Colorado River, Ail-American Canal and East Highline Canal

    Science.gov (United States)

    Suarez, D. L.

    1983-06-01

    In situ pH determinations and analysis of major ions in solution indicated that the lower Colorado River is supersaturated with respect to calcite throughout the entire daily cycle, in both winter and summer. Although the ion activity product was 4 to 6 times greater than the calcite solubility product, there was no detectable precipitation. Chemical analyses of water samples taken along 350 km of the river and canals from Parker Dam to the Salton Sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows. Laboratory kinetic studies indicated that calcite crystal growth rates with Colorado River water are about 30% of the rate for pure Ca-HCO3 waters and about 70% of that for synthetic Colorado River water. Calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite. Critical supersaturation levels necessary for heterogeneous nucleation do not occur; a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime H2CO3 levels.

  19. Calcium

    Science.gov (United States)

    ... in luck if you like sardines and canned salmon with bones. Almond milk. previous continue Working Calcium ... drinks, and cereals. Other Considerations for Building Bones Vitamin D is essential for calcium absorption, so it's ...

  20. Green Synthesis of Calcium Carbonate Uniform Microspheres Using Vegetables%Green Synthesis of Calcium Carbonate Uniform Microspheres Using Vegetables

    Institute of Scientific and Technical Information of China (English)

    Chen, Long; Bao, Zuben; Pan, Jian; Xu, Weibing; Zhang, Heping; Hu, Hongbo; Hu, Jichao; Zhou, Lili

    2012-01-01

    We report a novel strategy for the green synthesis of calcium carbonate (CaCO3) microspheres by using four vegetables: potato, cucumber, aubergine, and carrot. The products were characterized by scanning electron microscopy, X-ray powder diffractometry and/or Fourier transform infrared spectroscopy. The results show that the spherical calcite crystals are obtained in the presence of potato, cucumber and aubergine extracts, while uniform vaterite and calcite mixed microspheres are produced with the extracts of carrot. The possible formation mechanism of the CaCO3 microspheres by using vegetables is also discussed, suggesting that the biomolecules especially proteins may induce and control the nucleation and growth of CaCO3 crystals. CaCO3 is an important biomineral and inorganic material. Uniform particles have numerous important applications in many areas. Therefore, this study is very significant not only for expanding the scope of crystal engineering, but also for biomineralization research and green synthesis of functional inorganic materials.

  1. Eggshell powder, a comparable or better source of calcium than purified calcium carbonate: Piglet studies

    NARCIS (Netherlands)

    Schaafsma, A.; Beelen, G.M.

    1999-01-01

    Powdered chicken eggshells might be an interesting and widely available source of calcium. In two studies using piglets we determined the digestibility of calcium from different diets. The first study compared casein-based diets with CaCO3 (CasCC) or eggshell powder (CasES). The second study compare

  2. Eggshell powder, a comparable or better source of calcium than purified calcium carbonate: Piglet studies

    NARCIS (Netherlands)

    Schaafsma, A.; Beelen, G.M.

    1999-01-01

    Powdered chicken eggshells might be an interesting and widely available source of calcium. In two studies using piglets we determined the digestibility of calcium from different diets. The first study compared casein-based diets with CaCO3 (CasCC) or eggshell powder (CasES). The second study

  3. 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.

  4. Compactibility of mixtures of calcium carbonate and microcrystalline cellulose.

    Science.gov (United States)

    Garzón, M de Lourdes; Villafuerte, Leopoldo

    2002-01-01

    A patented coprocessed mixture of microcrystalline cellulose (MC) and calcium carbonate (CC) is claimed to perform, as a pharmaceutical excipient, equal or better than pure MC. To investigate it, the tensile strength (T) of tablets made of mixtures of MC type 102, CC, magnesium stearate (MS) and polyvinylpyrrolidone (PVP) and formed under a compaction pressure (P(c)) ranging up to 618 MPa has been determined. The compactibility of the mixtures was defined through regression parameters obtained with ln(-ln(1-T/T(max)))=slope x lnP(c) + intercept. MC/CC mixtures, P(c)=618 MPa, show a small decrease in tablet tensile strength with CC proportions up to about 20%, falling considerably thereafter. Lower compaction pressures, P(c)tablet tensile strength due to 2%-MS, P(c)=487 MPa, was recovered to 35% of its original value admixing about 25% CC. This maximal value of recovery showed a shift to lower proportions of CC, up to 10%, as compaction pressure decreased. This was attributed to lower CC-particles fragmentation or agglomerates spreading at lower compaction pressures. Mixtures with increased plasticity (MC/CC/PVP and MC/CC/PVP/MS) showed an increased compactibility, which was more evident at higher compaction pressures and higher CC proportions, presumably due to higher deformation and erosion of PVP particles. Inclusion of about 40% CC in a MC/PVP/MS mixture showed 60% recovery of the original MC tablet tensile strength. Lower MS proportions are expected to allow a higher recovery.

  5. Review of calcium carbonate polymorph precipitation in spring systems

    Science.gov (United States)

    Jones, Brian

    2017-05-01

    Many spring deposits throughout the world are characterized by spectacular deposits of calcium carbonate that are formed of various combinations of aragonite and calcite, and in very rare cases vaterite. The factors that control the precipitation of the aragonite and calcite have been the subject of considerable debate that has been based on natural precipitates and information gained from numerous laboratory experiments. Synthesis of this information indicates that there is probably no single universal factor that controls calcite and aragonite precipitation in all springs. Instead, the reason for aragonite as opposed to calcite precipitation should be ascertained by considering the following ordered series of possibilities for each system. First, aragonite, commonly with calcite as a co-precipitate, will form from spring water that has a high CO2 content and rapid CO2 degassing, irrespective of the Mg:Ca ratio and scale of precipitation. Second, aragonite can be precipitated from waters that have low levels of CO2 degassing provided that the Mg:Ca ratio is high enough to inhibit calcite precipitation. Third, the presence of biofilms may lead to the simultaneous precipitation of aragonite and calcite (irrespective of CO2 degassing or Mg:Ca ratio) either within the different microdomains that develop in the biofilm or because of diurnal changes in various geochemical parameters associated with the biofilm. Although the precipitation of calcite and aragonite has commonly been linked directly to water temperature, there is no clear evidence for this proposition. It is possible, however, that temperature may be influencing another parameter that plays a more direct role in the precipitation of these CaCO3 polymorphs. Despite the advances that have been made, the factors that ultimately control calcite and aragonite are still open to debate because this long-standing problem has still not been fully resolved.

  6. Preparation of pure calcium carbonate by mineral carbonation using industrial byproduct FGD gypsum

    Science.gov (United States)

    Song, K.; Kim, W.; Bang, J. H.; Park, S.; Jeon, C. W.

    2015-12-01

    Mineral carbonation is one of the geological approaches for the sequestration of anthropogenic CO2 gas. Its concept is based on the natural weathering processes in which silicate minerals containing divalent cations such as Ca or Mg are carbonated to CaCO3 or MgCO3 in the reaction with CO2gas. Raw materials for the mineral carbonation have been extended to various industrial solid wastes such as steel slag, ashes, or FGD (flue gas desulfurization) gypsum which are rich in divalent cations. These materials have economic advantages when they are produced in CO2 emission sites. Flue gas desulfurization (FGD) gypsum is such a byproduct obtained in at coal-fired power plants. Recently, we carried out a research on the direct mineral carbonation of FGD gypsum for CO2sequestration. It showed high carbonation reactivity under ambient conditions and the process can be described as follows: CaSO4·2H2O + CO2(g) + 2NH4OH(aq) → CaCO3(s) + (NH4)2SO4(aq) (1) At the early stage of the process, calcium carbonate (CaCO3) exists as a dissolved ion pair during the induction period. High-purity CaCO3 could be precipitated from dissolved calcium carbonate solution extracted during the induction period. The effect of experimental parameters on pure CaCO3 was evaluated: CO2 flow rate (1-3 L/min), ammonia content (4-12%), and solid-to-liquid (S/L) ratio (5-300 g/L). FE-SEM (field-emission scanning electron microscopy) and XRD (X-ray diffraction) study revealed that the precipitated CaCO3 was round-shaped vaterite crystals. The induction time was inversely proportional to the CO2 flow rate and the yield for pure CaCO3 increased with the ammonia content. The formation efficiency for pure CaCO3 decreased with S/L (solid/liquid) ratio. It was 90% (mol/mol) when the S/L ratio was 5 g/L. However, S/L ratio didn't affect the maximum solubility limit of dissolved CaCO3.

  7. SUPERSATURATED DESIGN WITH MORE THAN TWO LEVELS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Supersaturated designs are useful in screening experiments. This paper discusses the topic of multi-level supersaturated design. Two quantities, E(d2) and Df, are proposed to evaluate the optimality of supersaturated designs. A lower bound of E(d2) is obtained with a necessary condition for achieving it. Some E(d2)-optimal supersaturated designs of 3, 4, and 5 levels are given.

  8. Performance of separation processes for precipitated calcium carbonate produced with an innovative method from steelmaking slag and carbon dioxide

    Directory of Open Access Journals (Sweden)

    Sebastian eTeir

    2016-02-01

    Full Text Available 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 CO2 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 CO2 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/m2h and a low cake residual moisture content (12-14 wt-%. Vacuum filtration gave slightly higher filtration rates (500-610 kg/m2h 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 solids can be achieved

  9. 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

  10. Calcium-decorated carbon nanostructures for the selective capture of carbon dioxide.

    Science.gov (United States)

    Koo, Jahyun; Bae, Hyeonhu; Kang, Lei; Huang, Bing; Lee, Hoonkyung

    2016-10-26

    The development of advanced materials for CO2 capture is of great importance for mitigating climate change. In this paper, we outline our discovery that calcium-decorated carbon nanostructures, i.e., zigzag graphene nanoribbons (ZGNRs), carbyne, and graphyne, have great potential for selective CO2 capture, as demonstrated via first-principles calculations. Our findings show that Ca-decorated ZGNRs can bind up to three CO2 molecules at each Ca atom site with an adsorption energy of ∼-0.8 eV per CO2, making them suitable for reversible CO2 capture. They adsorb CO2 molecules preferentially, compared with other gas molecules such as H2, N2, and CH4. Moreover, based on equilibrium thermodynamical simulations, we confirm that Ca-decorated ZGNRs can capture CO2 selectively from a gas mixture with a capacity of ∼4.5 mmol g(-1) under ambient conditions. Similar results have been found in other carbon nanomaterials, indicating the generality of carbon based nanostructures for selective CO2 capture under ambient conditions.

  11. 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.

  12. 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.

  13. Ubiquitylation functions in the calcium carbonate biomineralization in the extracellular matrix.

    Directory of Open Access Journals (Sweden)

    Dong Fang

    Full Text Available Mollusks shell formation is mediated by matrix proteins and many of these proteins have been identified and characterized. However, the mechanisms of protein control remain unknown. Here, we report the ubiquitylation of matrix proteins in the prismatic layer of the pearl oyster, Pinctada fucata. The presence of ubiquitylated proteins in the prismatic layer of the shell was detected with a combination of western blot and immunogold assays. The coupled ubiquitins were separated and identified by Edman degradation and liquid chromatography/mass spectrometry (LC/MS. Antibody injection in vivo resulted in large amounts of calcium carbonate randomly accumulating on the surface of the nacreous layer. These ubiquitylated proteins could bind to specific faces of calcite and aragonite, which are the two main mineral components of the shell. In the in vitro calcium carbonate crystallization assay, they could reduce the rate of calcium carbonate precipitation and induce the calcite formation. Furthermore, when the attached ubiquitins were removed, the functions of the EDTA-soluble matrix of the prismatic layer were changed. Their potency to inhibit precipitation of calcium carbonate was decreased and their influence on the morphology of calcium carbonate crystals was changed. Taken together, ubiquitylation is involved in shell formation. Although the ubiquitylation is supposed to be involved in every aspect of biophysical processes, our work connected the biomineralization-related proteins and the ubiquitylation mechanism in the extracellular matrix for the first time. This would promote our understanding of the shell biomineralization and the ubiquitylation processes.

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

    Science.gov (United States)

    Mulopo, J; Mashego, M; Zvimba, J N

    2012-01-01

    The conversion of steelmaking slag (a waste product of the steelmaking process) to calcium carbonate (CaCO(3)) was tested using hydrochloric acid, ammonium hydroxide and carbon dioxide via a pH-swing process. Batch reactors were used to assess the technical feasibility of calcium carbonate recovery and its use for pre-treatment of acid mine drainage (AMD) from coal mines. The effects of key process parameters, such as the amount of acid (HCl/calcium molar ratio), the pH and the CO(2) flow rate were considered. It was observed that calcium extraction from steelmaking slag significantly increased with an increase in the amount of hydrochloric acid. The CO(2) flow rate also had a positive effect on the carbonation reaction rate but did not affect the morphology of the calcium carbonate produced for values less than 2 L/min. The CaCO(3) recovered from the bench scale batch reactor demonstrated effective neutralization ability during AMD pre-treatment compared with the commercial laboratory grade CaCO(3).

  15. Effect of acid rain on calcium carbonate saturation in the Albemarle sound of North Carolina

    Energy Technology Data Exchange (ETDEWEB)

    Rudolph, K.A.; Burgess, S.K.; Willey, J.D.; Kieber, R.J. [Univ. of North Carolina, Wilmington, NC (United States)

    1996-10-01

    The effects of acidic rainwater additions on calcium carbonate solubility and alkalinity in the poorly buffered, biologically active and commercially important waters of the Albemarle Sound, NC are reported. Samples collected monthly at four sites were analyzed for salinity, pK total alkalinity, and calcium concentrations. Five percent and 10% dilutions of sulfuric acid at pH 4, mimicking acid rain additions, were added and total alkalinity and calcium concentrations again determined. The addition of acid decreased the alkalinity in the Albemarle samples by as much as 15%, although the magnitude of the impact depended both on site and season. The effects of acid additions on dissolved calcium concentrations were more variable,. and also displayed a site and season dependency. Calcium concentrations, alkalinity, and pH values were also determined during controlled laboratory experiments, where 25 mg/L Callinectes sapidus shells were added to Albemarle Sound water. All three analytes increased significantly upon acid additions relative to controls.

  16. Supersaturation in the Boolean lattice

    NARCIS (Netherlands)

    Dove, A.P.; Griggs, J.R.; Kang, Ross; Sereni, Jean-Sébastien

    2014-01-01

    We seek families of subsets of an n-set of given size that contain the fewest k-chains. We prove a “supersaturation-type” extension of both Sperner’s Theorem (1928) and its generalization by Erd˝os (1945). Erd˝os showed that a largest k-chain free family in the Boolean lattice is formed by taking

  17. Effects of iron and calcium carbonate on the variation and cycling of carbon source in integrated wastewater treatments.

    Science.gov (United States)

    Zhimiao, Zhao; Xinshan, Song; Yufeng, Zhao; Yanping, Xiao; Yuhui, Wang; Junfeng, Wang; Denghua, Yan

    2017-02-01

    Iron and calcium carbonate were added in wastewater treatments as the adjusting agents to improve the contaminant removal performance and regulate the variation of carbon source in integrated treatments. At different temperatures, the addition of the adjusting agents obviously improved the nitrogen and phosphorous removals. TN and TP removals were respectively increased by 29.41% and 23.83% in AC-100 treatment under 1-day HRT. Carbon source from dead algae was supplied as green microbial carbon source and Fe(2+) was supplied as carbon source surrogate. COD concentration was increased to 30mg/L and above, so the problem of the shortage of carbon source was solved. Dead algae and Fe(2+) as carbon source supplement or surrogate played significant role, which was proved by microbial community analysis. According to the denitrification performance in the treatments, dead algae as green microbial carbon source combined with iron and calcium carbonate was the optimal supplement carbon source in wastewater treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Preparation and mechanism of calcium phosphate coatings on chemical modified carbon fibers by biomineralization

    Institute of Scientific and Technical Information of China (English)

    HUANG Su-ping; ZHOU Ke-chao; LI Zhi-you

    2008-01-01

    In order to prepare HA coatings on the carbon fibers, chemical modification and biomineralization processes were applied. The phase components, morphologies, and possible growth mechanism of calcium phosphate were studied by infrared spectroscopy(IR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM). The results show that calcium phosphate coating on carbon fibers can be obtained by biomineralization. But the phase components and morphologies of calcium phosphate coatings are different due to different modification methods. Plate-like CaHPO4-2H2O (DCPD) crystals grow from one site of the active centre by HNO3 treatment. While on the para-aminobenzoic acid treated fibers, the coating is composed of nano-structural HA crystal homogeneously. This is because the -COOH functional groups of para-aminobenzoic acid graft on fibers, with negative charge and arranged structure, accelerating the HA crystal nucleation and crystallization on the carbon fibers.

  19. Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing.

    Science.gov (United States)

    Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

    2012-03-01

    Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm(3), had a specific surface area of 65 m(2)/g and a composition of CaCO(3)•0.5H(2)O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature.

  20. The influence of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation

    Science.gov (United States)

    Putro, Triswantoro; Endarko

    2016-04-01

    The influences of electron discharge and magnetic field on calcium carbonate (CaCO3) 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.

  1. MINERALIZATION STUDY OF RENAL RATS FOLLOWING OVARYOHYSTERECTOMY AND ADMINISTRATION HIGH DOSE CALCIUM CARBONATE

    OpenAIRE

    Wiwik Misaco Yuniarti; Ira Sari Yudaniayanti; Nusdianto Triakoso

    2008-01-01

    The aim of this study was to determine the effect of high dose calcium carbonate in rat (Rattus norvegicus) following ovaryohysterectomy. A total of twenty female rats at 13 week-old were used in this study. Following ovaryohitectomy, the animals were randomized in four treatment groups. Group P0 were :fed with standard food only P1, P2 and P2 groups treated with standard food but supplemented calcium carbonate respectively at the dose of 75 mg per animal per day, 225 mg per animal per day , ...

  2. Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles

    OpenAIRE

    Gebauer, Denis; Liu, Xing-Min; Aziz, Baroz; Hedin, Niklas; Zhao, Zhe

    2013-01-01

    Porous tablets of crystalline calcium carbonate were formed upon sintering of a precursor powder of amorphous calcium carbonate (ACC) under compressive stress (20 MPa) at relatively low temperatures (120–400 °C), induced by pulsed direct currents. Infrared spectroscopy ascertained the amorphous nature of the precursor powders. At temperatures of 120–350 °C and rates of temperature increase of 20–100 °C min−1, the nanoparticles of ACC transformed into crystallites of mainly aragonite, which is...

  3. 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.

  4. Chemical analysis and molecular models for calcium-oxygen-carbon interactions in black carbon found in fertile Amazonian anthrosoils.

    Science.gov (United States)

    Archanjo, Braulio S; Araujo, Joyce R; Silva, Alexander M; Capaz, Rodrigo B; Falcão, Newton P S; Jorio, Ado; Achete, Carlos A

    2014-07-01

    Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change.

  5. Study on Electromagnetic Field Influence on Nucleation Induction Period of Calcium Carbonate%电磁场对碳酸钙成核诱导期影响的实验研究

    Institute of Scientific and Technical Information of China (English)

    王建国; 李松; 朱和升

    2013-01-01

    基于电导率随滴定液容积变化特征与碳酸钙结晶过程的对比分析,研究了电磁场作用对碳酸钙结晶过程中成核诱导期的影响.在不同频率的电磁场作用下观察了碳酸钙溶液临界过饱和度及成核诱导期的变化,大量实验结果表明:电磁场作用能够降低碳酸钙溶液临界过饱和度,加速碳酸钙成核,缩短成核诱导期.通过机理分析,电磁场对碳酸钙成核过程的主要作用为:在洛伦兹力的影响下,溶液中的Ca2+及CO32-等带电离子运动方向要向相反方向偏离,增加了Ca2+和CO32-离子间的碰撞几率,加快新相晶核的生成.%Based on analyzing the conductivity which changing with titration volume and comparing the calcium carbonate fouling process,the electromagnetic field influence on nucleation induction period of calcium carbonate crystallization was analyzed; and the changes of critical supersaturation ratio and nucleation induction period of calcium carbonate solution were observed at the electromagnetic field with different frequencies.Experiment results show that:the electromagnetic field influence can decrease the critical supersaturation ratio,and can speed up the nucleation rate and shorten nucleation induction period.The mechanism analysis shows that the main influence of electromagnetic field on calcium carbonate nucleation process is under the Lorentz force,the charge ions like Ca2+ and CO32-can move in opposite direction so as to increase collision probability of Ca2+ and CO32-and to speeded up the formation of new phase crystal nucleus.

  6. Identification and comparison of amorphous calcium carbonate-binding protein and acetylcholine-binding protein in the abalone, Haliotis discus hannai.

    Science.gov (United States)

    Huang, Jing; Wang, Hongzhong; Cui, Yu; Zhang, Guiyou; Zheng, Guilan; Liu, Shiting; Xie, Liping; Zhang, Rongqing

    2009-01-01

    Nacre has two different microarchitectures: columnar nacre and sheet nacre. We previously identified an important regulator of the morphology of sheet nacre tablets, which was named amorphous calcium carbonate-binding protein (pf-ACCBP). However, little is known about its counterpart in columnar nacre. Moreover, pf-ACCBP shares significant sequence similarity with a group of acetylcholine-binding proteins (AChBP) that participate in neuronal synapses transmission, but the relationships between the two proteins, which are homologous in sequences but disparate in function, have not been studied yet. Here, we identified an amorphous calcium carbonate-binding protein and an acetylcholine-binding protein in the abalone, Haliotis discus hannai, named hdh-ACCBP and hdh-AChBP, respectively. Studies of hdh-ACCBP indicated that it was a counterpart of pf-ACCBP in gastropods that might function similarly in columnar nacre formation and supersaturated extrapallial fluid. Analysis of hdh-AChBP showed that unlike previously identified AChBP, hdh-AChBP was not only expressed in the nervous system but could also be detected in non-nervous system cells, such as the goblet cells of the mantle pallial. Additionally, its expression patterns during embryo and larval development did not accord with ganglion development. These phenomena indicated that AChBP might play more general roles than just in neuronal synapses transmission. Comparison of hdh-ACCBP and hdh-AChBP revealed that they were quite different in their post-translational modification and oligomerization and that they were controlled under different transcriptional regulation systems, consequently obtaining disparate expression profiles. Our results also implied that ACCBP and AChBP might come from a common ancestor through gene duplication and divergence.

  7. Calcium in diet

    Science.gov (United States)

    ... D is needed to help your body use calcium. Milk is fortified with vitamin D for this reason. ... of calcium dietary supplements include calcium citrate and calcium carbonate. Calcium citrate is the more expensive form of ...

  8. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    2015-01-01

    Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenviro......Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track...

  9. THE DYNAMIC EXPERIMENT OF THRESHOLD SCALING INHIBITORS AGAINST THE PRECIPITATION OF CALCIUM CARBONATE IN AQUEOUS SOLUTION%非化学配比阻垢剂对水垢析晶过程影响的动力学研究

    Institute of Scientific and Technical Information of China (English)

    李广兵; 方健; 李杰

    2001-01-01

    The effect of two threshold indibitors, sodium polyphosphate(SPP) and polypropylene acid (PAA) on the precipitation of calcium carbonate were investigated. The formation of species from solution was computed from the recorded conductivity values and mass-balance and charge-balance equations by successive approximations for the ionic strenght. The nano-scale crystals of calcium carbonate was seeded. This made the experiments reproducible. The inhibitors' threshold in our experiments was independent on the solution's supersaturation and inhibitor effectiveness defined by static method was sensitive to supersaturation.%我们基于溶液电离平衡、质子平衡、离子活度原理以及法拉第分布电解定律,建立了精确测量碳酸钙过饱和溶液在析晶过程中所有离子变化的试验系统,并使用该系统研究了阻垢剂聚丙烯酸和多聚磷酸钠对碳酸钙析晶过程的影响。试验中使用了植晶的方法,保证了试验具有高重复性。试验研究表明,静态法所定义的阻垢率数值易受溶液过饱和度的影响,但是动力学方法测量的阻垢剂的阻垢阈值不受影响。动力学的研究和静态法的结合加深了我们对阻垢剂的阻垢过程的了解。

  10. MINERALIZATION STUDY OF RENAL RATS FOLLOWING OVARYOHYSTERECTOMY AND ADMINISTRATION HIGH DOSE CALCIUM CARBONATE

    Directory of Open Access Journals (Sweden)

    Wiwik Misaco Yuniarti

    2008-06-01

    Full Text Available The aim of this study was to determine the effect of high dose calcium carbonate in rat (Rattus norvegicus following ovaryohysterectomy. A total of twenty female rats at 13 week-old were used in this study. Following ovaryohitectomy, the animals were randomized in four treatment groups. Group P0 were :fed with standard food only P1, P2 and P2 groups treated with standard food but supplemented calcium carbonate respectively at the dose of 75 mg per animal per day, 225 mg per animal per day , and 450 mg per animal per day. The calcium carbonate supplement were given daily in the morning for 42 days. The experimental animals were sacrificed at 21 week-old. Calcium and phosphor level in sinister kidneys were determined by spectrofotometric method. The data obtained from this study were analysed using one way analysis of variance. No significant difference was observed in calcium level among four treatment groups, with the lowest level were found in P3 group. However, the phosphor level of P1 was significantly lower than those of P2 and P3 groups. The highest phosphor level was observed in P3 group, indicating a phosphorous retension and the signs of renal failure.

  11. 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.

  12. Microwave -assisted Synthesis Calcium Carbonate in Water/Ethylene Glycol Mixed Solvents%水/乙二醇混合溶剂中微波辅助合成碳酸钙

    Institute of Scientific and Technical Information of China (English)

    孙新园; 张群; 陈敏; 潘玉锁

    2012-01-01

    在水/乙二醇混合溶剂中,通过微波辅助加热的方法,研究溶液过饱和度对碳酸钙成核生长的影响。分别采用扫描电子显微镜(SEM)、X-射线粉末衍射(XRD)对所得的样品进行了表征。结果表明,过饱和度的改变对碳酸钙形貌和晶型具有非常明显的影响,分别获得了菱面体状方解石、纤维捆扎状文石、松树枝状球霰石为主体的碳酸钙晶体。%In this paper, the influence of diffident supersaturations of the bulk solution on the nucleation and crystal growth of calcium carbonate is studied through the method of microwave - assisted beating in water/ethylene glycol mixed solvents. The ob- tained crystals are characterized by scanning electron microscopy (SEM) and X -ray diffraction (XRD). The resuh shows that the morphologies and polymorphs are obvious varied from rhombohedron calcite, fiber strapping aragonite to pine - dendritic vater- ite with the changes of supersaturations.

  13. Effects of Sigma Anti-bonding Molecule Calcium Carbonate on bone turnover and calcium balance in ovariectomized rats.

    Science.gov (United States)

    Choi, So-Young; Park, Dongsun; Yang, Goeun; Lee, Sun Hee; Bae, Dae Kwon; Hwang, Seock-Yeon; Lee, Paul K; Kim, Yun-Bae; Kim, Ill-Hwa; Kang, Hyun-Gu

    2011-12-01

    This study was conducted to evaluate the effect of Sigma Anti-bonding Molecule Calcium Carbonate (SAC) as therapy for ovariectomy-induced osteoporosis in rats. Three weeks after surgery, fifteen ovariectomized Sprague-Dawley rats were divided randomly into 3 groups: sham-operated group (sham), ovariectomized group (OVX) and SAC-treatment group (OVX+SAC). The OVX+SAC group was given drinking water containing 0.0012% SAC for 12 weeks. Bone breaking force and mineralization as well as blood parameters related to the bone metabolism were analyzed. In OVX animals, blood concentration of 17β-estradiol decreased significantly, while osteocalcin and type I collagen C-terminal telopeptides (CTx) increased. Breaking force, bone mineral density (BMD), calcium and phosphorus in femurs, as well as uterine and vaginal weights, decreased significantly following OVX. However, SAC treatment (0.0012% in drinking water) not only remarkably restored the decreased 17β-estradiol and increased osteocalcin and CTx concentrations, but also recovered decreased femoral breaking force, BMD, calcium and phosphorus, although it did not reversed reproductive organ weights. It is suggested that SAC effectively improve bone density by preventing bone turnover mediated osteocalcin, CTx and minerals, and that it could be a potential candidate for therapy or prevention of postmenopausal osteoporosis.

  14. Chemical and physical controls on the transformation of amorphous calcium carbonate into crystalline CaCO3 polymorphs

    Science.gov (United States)

    Blue, C. R.; Giuffre, A.; Mergelsberg, S.; Han, N.; De Yoreo, J. J.; Dove, P. M.

    2017-01-01

    Calcite and other crystalline polymorphs of CaCO3 can form by pathways involving amorphous calcium carbonate (ACC). Apparent inconsistencies in the literature indicate the relationships between ACC composition, local conditions, and the subsequent crystalline polymorphs are not yet established. This experimental study quantifies the control of solution composition on the transformation of ACC into crystalline polymorphs in the presence of magnesium. Using a mixed flow reactor to control solution chemistry, ACC was synthesized with variable Mg contents by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within the output suspension under stirred or quiescent conditions while characterizing the evolving solutions and solids. As the ACC transforms into a crystalline phase, the solutions record a polymorph-specific evolution of pH and Mg/Ca. The data provide a quantitative framework for predicting the initial polymorph that forms from ACC based upon the solution aMg2+/aCa2+ and aCO32-/aCa2+ and stirring versus quiescent conditions. This model reconciles discrepancies among previous studies that report on the nature of the polymorphs produced from ACC and supports the previous claim that monohydrocalcite may be an important, but overlooked, transient phase on the way to forming some aragonite and calcite deposits. By this construct, organic additives and extreme pH are not required to tune the composition and nature of the polymorph that forms. Our measurements show that the Mg content of ACC is recorded in the resulting calcite with a ≈1:1 dependence. By correlating composition of these calcite products with the Mgtot/Catot of the initial solutions, we find a ≈3:1 dependence that is approximately linear and general to whether calcite is formed via an ACC pathway or by the classical step-propagation process. Comparisons to calcite grown in synthetic seawater show a ≈1:1 dependence. The relationships suggest that the

  15. The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

    Science.gov (United States)

    Kramer, Henry

    1956-01-01

    A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement. The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range. The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere. The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

  16. Constant-distance mode scanning potentiometry. 1. Visualization of calcium carbonate dissolution in aqueous solution.

    Science.gov (United States)

    Etienne, Mathieu; Schulte, Albert; Mann, Stefan; Jordan, Guntram; Dietzel, Irmgard D; Schuhmann, Wolfgang

    2004-07-01

    Constant-distance mode scanning potentiometry was established by integrating potentiometric microsensors as ion-selective scanning probes into a SECM setup that was equipped with a piezoelectric shear force-based tip-to-sample distance control. The combination of specially designed micrometer-sized potentiometric tips with an advanced system for tip positioning allowed simultaneous acquisition of both topographic and potentiometric information at solid/liquid interfaces with high spatial resolution. The performance of the approach was evaluated by applying Ca(2+)-selective constant-distance mode potentiometry to monitor the dissolution of calcium carbonate occurring either at the (104) surface of calcite crystals or in proximity to the more complex surface of cross sections of a calcium carbonate shell of Mya arenaria exposed to slightly acidic aqueous solutions. Micrometer-scale heterogeneities in the apparent calcium activity profiles have successfully been resolved for both samples.

  17. 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...

  18. Soil tillage, water erosion, and calcium, magnesium and organic carbon losses

    Directory of Open Access Journals (Sweden)

    Bertol Ildegardis

    2005-01-01

    Full Text Available Soil tillage influences water erosion, and consequently, losses of calcium, magnesium and organic carbon in surface runoff. Nutrients and organic carbon are transported by surface runoff in particulate form, adsorbed to soil colloids or soluble in water, depending on the soil tillage system. This study was carried out on an Inceptisol, representative of the Santa Catarina highlands, southern Brazil, between November 1999 and October 2001, under natural rainfall. The soil tillage treatments (no replications were: no-tillage (NT, minimum soil tillage with chiseling + disking (MT, and conventional soil tillage with plowing + two diskings (CT. The crop cycles sequence was soybean (Glycine max, oats (Avena sativa, beans (Phaseolus vulgaris and vetch (Vicia sativa. Conventional soil tillage treatment with plowing + two disking in the absence of crops (BS was also studied. Calcium and magnesium concentrations were determined in both water and sediments of the surface runoff, while organic carbon was measured only in sediments. Calcium and magnesium concentrations were greater in sediments than in surface runoff, while total losses of these elements were greater in surface runoff than in sediments. The greatest calcium and magnesium concentrations in surface runoff were obtained under CT, while in sediments the greatest concentration occurred under MT. Organic carbon concentration in sediments did not differ under the different soil tillage systems, and the greatest total loss was under CT system.

  19. Calcium carbonate crystallization controlled by functional groups: A mini-review

    Institute of Scientific and Technical Information of China (English)

    Hua DENG; Xing-Can SHEN; Xiu-Mei WANG; Chang DU

    2013-01-01

    Various functional groups have been suggested to play essential roles on biomineralization of calcium carbonate (CaCO3) in natural system. 2D and 3D models of regularly arranged functional groups have been established to investigate their effect on CaCO3 crystallization, This mini-review summarizes the recent progress and the future development is prospected.

  20. [Study on solid dispersion of precipitated calcium carbonate-based oleanolic acid].

    Science.gov (United States)

    Yan, Hong-mei; Zhang, Zhen-hai; Jia, Xiao-bin; Jiang, Yan-rong; Sun, E

    2015-05-01

    Oleanolic acid-precipitated calcium carbonate solid dispersion was prepared by using solvent evaporation method. The microscopic structure and physicochemical properties of solid dispersion were analyzed using differential scanning calorimetry and scanning electron microscopy (SEM). And its in vitro release also was investigated. The properties of the precipitated calcium carbonate was studied which was as a carrier of oleanolic acid solid dispersion. Differential scanning calorimetry analysis suggested that oleanolic acid may be present in solid dispersion as amorphous substance. The in vitro release determination results of oleanolic acid-precipitated calcium carbonate (1: 5) solid dispersion showed accumulated dissolution rate of.oleanolic acid was up to 90% at 45 min. Accelerating experiment showed that content and in vitro dissolution of oleanolic acid solid dispersion did not change after storing over 6 months. The results indicated that in vitro dissolution of oleanolic acid was improved greatly by the solid dispersion with precipitated calcium carbonate as a carrier. The solid dispersion is a stabilizing system which has actual applied value.

  1. Amorphous and crystalline calcium carbonate distribution in the tergite cuticle of moulting Porcellio scaber (Isopoda, Crustacea).

    Science.gov (United States)

    Neues, Frank; Hild, Sabine; Epple, Matthias; Marti, Othmar; Ziegler, Andreas

    2011-07-01

    The main mineral components of the isopod cuticle consists of crystalline magnesium calcite and amorphous calcium carbonate. During moulting isopods moult first the posterior and then the anterior half of the body. In terrestrial species calcium carbonate is subject to resorption, storage and recycling in order to retain significant fractions of the mineral during the moulting cycle. We used synchrotron X-ray powder diffraction, elemental analysis and Raman spectroscopy to quantify the ACC/calcite ratio, the mineral phase distribution and the composition within the anterior and posterior tergite cuticle during eight different stages of the moulting cycle of Porcellio scaber. The results show that most of the amorphous calcium carbonate (ACC) is resorbed from the cuticle, whereas calcite remains in the old cuticle and is shed during moulting. During premoult resorption of ACC from the posterior cuticle is accompanied by an increase within the anterior tergites, and mineralization of the new posterior cuticle by resorption of mineral from the anterior cuticle. This suggests that one reason for using ACC in cuticle mineralization is to facilitate resorption and recycling of cuticular calcium carbonate. Furthermore we show that ACC precedes the formation of calcite in distal layers of the tergite cuticle.

  2. Preparation and Characterization of Three-dimensional Chrysanthemun Flower-like Calcium Carbonate

    Institute of Scientific and Technical Information of China (English)

    CHEN Xianyong; TANG Qin; LIU Daijun; HU Weibing; DAN Youmeng

    2012-01-01

    Calcium carbonate with three-dimensional chrysanthemun flower-like structure was successfully prepared from calcium chloride and sodium carbonate ethanol/water mixed solution by a simple precipitation method,using trisodium citrate as crystal modifier.The experimental results show that the threedimensional structure of chrysanthemun flower-like calcium carbonate is built up with several symmetrical micrometer multi-layer petals arranged around the multi-layer pancake-liked center,and the micrometer center and petals are assemblied by a large number of nanometer spherical particles with size 10-20 nm.It is found that the amount of trisodium citrate,the ethanol volume content has an important influence on the formation of this morphology.A possible mechanism is proposed to explain the formation of three-dimensional chrysanthemun flower-like calcium carbonate according the results.Scanning electron microscopy (SEM),X-ray powder diffraction (XRD),flourier transform infrared spectroscopy (FT-IR),thermogravimety analysis (TG),transmission electron microscopy (TEM) equipped with energy-dispersive X-ray (EDX),and selected area electron diffraction (SAED) were used to characterize the crystals.

  3. Kinetics and Mechanism of Decomposition of Nano-sized Calcium Carbonate under Non-isothermal Condition

    Institute of Scientific and Technical Information of China (English)

    刘润静; 陈建峰; 郭奋; 吉米; 沈志刚

    2003-01-01

    Experiments on thermal decomposition of nano-sized calcium carbonate were carried out in a thermo-gravimetric analyzer under non-isothermal condition of different heating rates (5 to 20K·min-1). The Coats and Redfern''s equation was used to determine the apparent activation energy and the pre-exponential factors. The mechanism of thermal decomposition was evaluated using the master plots, Coats and Redfern's equation and the kinetic compensation law. It was found that the thermal decomposition property of nano-sized calcium carbonate was different from that of bulk calcite. Nano-sized calcium carbonate began to decompose at 640℃, which was 180℃ lower than the reported value for calcite. The experimental results of kinetics were compatible with the mechanism of one-dimensional phase boundary movement. The apparent activation energy of nano-sized calcium carbonate was estimated to be 151 kJ·mo1-1 while the literature value for normal calcite was approximately 200 kJ ·mol-1. The order of magnitude of Dre-exvonential factors was estimated to be 109 s-1.

  4. A new crystallization process in polypropylene highly filled with calcium carbonate

    NARCIS (Netherlands)

    Schawe, Jurgen E.K.; Vermeulen, Paul A.; van Drongelen, Martin

    2015-01-01

    The influence of high amounts of calcium carbonate filler on the crystallization behavior of polypropylene (PP) is investigated by differential scanning calorimetry (DSC) and fast scanning DSC measurements. The non-isothermal crystallization process at industrially relevant cooling rates of about

  5. 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

  6. Calcium carbonate production of the mare incognitum, the upper windward reef slope, at enewetak atoll.

    Science.gov (United States)

    Smith, S V; Harrison, J T

    1977-08-05

    Corals and algal pavement produce calcium carbonate more slowly on the windward reef slope of Enewetak Atoll than on the reef flat despite the high standing crop of reef-building organisms on the slope. The capacity of reefs to remain at or near sea level is therefore not determined primarily by growth on the seaward slope.

  7. Coexistence of three calcium carbonate polymorphs in the shell of the Antarctic clam Laternula elliptica

    Science.gov (United States)

    Nehrke, Gernot; Poigner, Harald; Wilhelms-Dick, Dorothee; Brey, Thomas; Abele, Doris

    2012-05-01

    We analyzed shell cuts of five individuals of the Antarctic bivalve Laternula elliptica from three locations along the Antarctic Peninsula by means of Confocal Raman Microscopy (CRM) as well as Electron Microprobe (EMP). The shell of L. elliptica has been previously described as being composed of aragonite exclusively. Now, CRM mapping reveals that three polymorphs of calcium carbonate - aragonite, calcite, and vaterite - are present in the chondrophore region of the examined individuals. Annual shell growth layers continue through aragonite and vaterite, suggesting simultaneous mineralization of both polymorphs. Spatially congruent EMP scans showed that the calcium carbonate polymorph affects the distribution of magnesium and strontium within the chondrophore. This is, to our knowledge, the first report of the coexistence of these three calcium carbonate polymorphs within the mineralized structures of a marine calcifying organism. Particularly the presence of vaterite is unexpected, but shows striking similarities to some fish otoliths. The strong effect of the calcium carbonate polymorph on trace element incorporation restrict the suitability of magnesium and strontium based proxies for the chondrophore area of L. elliptica.

  8. Introduction of enzymatically degradable poly(trimethylene carbonate) microspheres into an injectable calcium phosphate cement

    NARCIS (Netherlands)

    Habraken, Wouter J. E. M.; Zhang, Zheng; Wolke, Joop G. C.; Grijpma, Dirk W.; Mikos, Antonios G.; Feijen, Jan; Jansen, John A.

    2008-01-01

    Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polyester with rubber-like properties. Introduction of this polymer into an injectable calcium phosphate bone cement can therefore be used to introduce macroporosity into the cement for tissue engineering purposes as well as to impro

  9. Introduction of enzymatically degradable poly(trimethylene carbonate) microspheres into an injectable calcium phosphate cement.

    NARCIS (Netherlands)

    Habraken, W.J.E.M.; Zhang, Z.; Wolke, J.G.C.; Grijpma, D.W.; Mikos, A.G.; Feijen, J.; Jansen, J.A.

    2008-01-01

    Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polyester with rubber-like properties. Introduction of this polymer into an injectable calcium phosphate bone cement can therefore be used to introduce macroporosity into the cement for tissue engineering purposes as well as to impro

  10. Scientific Opinion on the safety assessment of the active substances, sodium erythorbate, sodium carbonate, sodium bicarbonate, iron sulphate, activated carbon, cellulose, calcium hydroxide, calcium chloride and water, for use as active system in food contact materials

    OpenAIRE

    2014-01-01

    This scientific opinion of EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids deals with the safety assessment of the active substances sodium erythorbate, sodium carbonate, sodium bicarbonate, iron sulfate, activated carbon, cellulose, calcium hydroxide, calcium chloride and water, used in mixture which is packed into sachets for absorbing oxygen/carbon dioxide emitting from/into the headspace surrounding packed food. All substances of this formulation have been e...

  11. Amorphous calcium carbonate controls avian eggshell mineralization: A new paradigm for understanding rapid eggshell calcification.

    Science.gov (United States)

    Rodríguez-Navarro, Alejandro B; Marie, Pauline; Nys, Yves; Hincke, Maxwell T; Gautron, Joel

    2015-06-01

    Avian eggshell mineralization is the fastest biogenic calcification process known in nature. How this is achieved while producing a highly crystalline material composed of large calcite columnar single crystals remains largely unknown. Here we report that eggshell mineral originates from the accumulation of flat disk-shaped amorphous calcium carbonate (ACC) particles on specific organic sites on the eggshell membrane, which are rich in proteins and sulfated proteoglycans. These structures known as mammillary cores promote the nucleation and stabilization of a amorphous calcium carbonate with calcitic short range order which predetermine the calcite composition of the mature eggshell. The amorphous nature of the precursor phase was confirmed by the diffuse scattering of X-rays and electrons. The nascent calcitic short-range order of this transient mineral phase was revealed by infrared spectroscopy and HRTEM. The ACC mineral deposited around the mammillary core sites progressively transforms directly into calcite crystals without the occurrence of any intermediate phase. Ionic speciation data suggest that the uterine fluid is equilibrated with amorphous calcium carbonate, throughout the duration of eggshell mineralization process, supporting that this mineral phase is constantly forming at the shell mineralization front. On the other hand, the transient amorphous calcium carbonate mineral deposits, as well as the calcite crystals into which they are converted, form by the ordered aggregation of nanoparticles that support the rapid mineralization of the eggshell. The results of this study alter our current understanding of avian eggshell calcification and provide new insights into the genesis and formation of calcium carbonate biominerals in vertebrates.

  12. SO{sub 2} retention on CaO/activated carbon sorbents. Part I: Importance of calcium loading and dispersion

    Energy Technology Data Exchange (ETDEWEB)

    M.C. Macias-Perez; A. Bueno-Lopez; M.A. Lillo-Rodenas; C. Salinas-Martinez de Lecea; A. Linares-Solano [University of Alicante, Alicante (Spain). Department of Inorganic Chemistry

    2007-03-15

    Sorbents for SO{sub 2} retention at low temperature consisting of CaO supported on activated carbons have been prepared by different methods (physical mixing, incipient wetness impregnation, rotary evaporator impregnation, complex formation and ionic exchange). Ca(OH){sub 2}, CaCO{sub 3}, CaO, Ca(CH{sub 3}COO){sub 2} and Ca(C{sub 2}H{sub 5}COO){sub 2} have been used as calcium precursors. The preparation method affects calcium loading as well as calcium dispersion. SO{sub 2} retention depends both on the calcium loading and on the calcium dispersion. The best preparation method, among those tested, was impregnation of the activated carbon with calcium acetate. Similar calcium loading can be obtained by the physical mixing method but the resulting calcium dispersion is low. On the contrary, samples with higher calcium dispersion were obtained by the complex formation method, presenting the disadvantage of the low calcium loading reached. The molar calcium conversion results are much higher than values reported for unsupported calcium compounds. 20 refs., 7 figs., 2 tabs.

  13. Calcium carbonate mineralization: involvement of extracellular polymeric materials isolated from calcifying bacteria.

    Science.gov (United States)

    Ercole, Claudia; Bozzelli, Paola; Altieri, Fabio; Cacchio, Paola; Del Gallo, Maddalena

    2012-08-01

    This study highlights the role of specific outer bacterial structures, such as the glycocalix, in calcium carbonate crystallization in vitro. We describe the formation of calcite crystals by extracellular polymeric materials, such as exopolysaccharides (EPS) and capsular polysaccharides (CPS) isolated from Bacillus firmus and Nocardia calcarea. Organic matrices were isolated from calcifying bacteria grown on synthetic medium--in the presence or absence of calcium ions--and their effect on calcite precipitation was assessed. Scanning electron microscopy observations and energy dispersive X-ray spectrometry analysis showed that CPS and EPS fractions were involved in calcium carbonate precipitation, not only serving as nucleation sites but also through a direct role in crystal formation. The utilization of different synthetic media, with and without addition of calcium ions, influenced the biofilm production and protein profile of extracellular polymeric materials. Proteins of CPS fractions with a molecular mass between 25 and 70 kDa were overexpressed when calcium ions were present in the medium. This higher level of protein synthesis could be related to the active process of bioprecipitation.

  14. Effects of Sevelamer Hydrochloride and Calcium Carbonate on Renal Osteodystrophy in Hemodialysis Patients

    Science.gov (United States)

    Ferreira, Aníbal; Frazão, João Miguel; Monier-Faugere, Marie-Claude; Gil, Célia; Galvao, José; Oliveira, Carlos; Baldaia, Jorge; Rodrigues, Ilidio; Santos, Carla; Ribeiro, Silvia; Hoenger, Regula Mueller; Duggal, Ajay; Malluche, Hartmut H.

    2008-01-01

    Disturbances in mineral metabolism play a central role in the development of renal bone disease. In a 54-wk, randomized, open-label study, 119 hemodialysis patients were enrolled to compare the effects of sevelamer hydrochloride and calcium carbonate on bone. Biopsy-proven adynamic bone disease was the most frequent bone abnormality at baseline (59%). Serum phosphorus, calcium, and intact parathyroid hormone were well controlled in both groups, although calcium was consistently lower and intact parathyroid hormone higher among patients who were randomly assigned to sevelamer. Compared with baseline values, there were no changes in mineralization lag time or measures of bone turnover (e.g., activation frequency) after 1 yr in either group. Osteoid thickness significantly increased in both groups, but there was no significant difference between them. Bone formation rate per bone surface, however, significantly increased from baseline only in the sevelamer group (P = 0.019). In addition, of those with abnormal microarchitecture at baseline (i.e., trabecular separation), seven of 10 in the sevelamer group normalized after 1 yr compared with zero of three in the calcium group. In summary, sevelamer resulted in no statistically significant changes in bone turnover or mineralization compared with calcium carbonate, but bone formation increased and trabecular architecture improved with sevelamer. Further studies are required to assess whether these changes affect clinical outcomes, such as rates of fracture. PMID:18199805

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

    Science.gov (United States)

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

    2012-07-30

    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.

  16. On supersaturation evaluation for solution growth

    Science.gov (United States)

    Söhnel, O.; Garside, J.

    1981-08-01

    The relation between the thermodynamic driving force for crystallization and the relative supersaturation is considered. A method devised by Van Leeuwen and Blomen, J. Crystal Growth 46 (1979) 96, for converting growth rat constant derived using relative supersaturation into those based on the thermodynamic driving force is discussed, its range of utility assessed and illustrated for several substances.

  17. Microbially-Mediated Precipitation of Calcium Carbonate Nanoparticles.

    Science.gov (United States)

    Kang, Ser Ku; Roh, Yul

    2016-02-01

    The objective of this study was to investigate the biomineralization of carbonate minerals using microorganisms (Wu Do-1) enriched from rhodoliths. A 16S rRNA sequence analysis showed that Wu Do-1 mainly contained Proteus mirabilis. The pH decreased from 6.5 to 5.3 over the first 4 days of incubation due to microbial oxidation of organic acids, after which it increased to 7.8 over the remaining incubation period. XRD analysis showed that the precipitates were Mg-rich cal- cite (MgxCa(1-x)CO3), whereas no precipitates were formed without the addition of Wu Do-1 in D-1 medium. SEM-EDS analyses showed that the Mg-rich calcite had a rhombohedron shape and consisted of Ca, Si and Mg with an extracelluar polymeric substance (EPS). In addition, TEM-EDS analyses revealed they were hexagon in shape, 500-700 nm in size, and composed of Ca, Mg, C, and O. These results indicated that Wu Do-1 induced precipitation of Mg-rich calcite on the cell walls and EPS via the accumulation of Ca and/or Mg ions. Therefore, microbial precipitation of carbonate nanoparticles may play an important role in metal and carbon biogeochemistry, as well as in carbon sequestration in natural environments.

  18. Ocean acidification accelerates net calcium carbonate loss in a coral rubble community

    Science.gov (United States)

    Stubler, Amber D.; Peterson, Bradley J.

    2016-09-01

    Coral rubble communities are an important yet often overlooked component of a healthy reef ecosystem. The organisms inhabiting reef rubble are primarily bioeroders that contribute to the breakdown and dissolution of carbonate material. While the effects of ocean acidification on calcifying communities have been well studied, there are few studies investigating the response of bioeroding communities to future changes in pH and calcium carbonate saturation state. Using a flow-through pH-stat system, coral rubble pieces with a naturally occurring suite of organisms, along with bleached control rubble pieces, were subjected to three different levels of acidification over an 8-week period. Rates of net carbonate loss in bleached control rubble doubled in the acidification treatments (0.02 vs. 0.04% CaCO3 d-1 in ambient vs. moderate and high acidification), and living rubble communities experienced significantly increased rates of net carbonate loss from ambient to high acidification conditions (0.06 vs. 0.10% CaCO3 d-1, respectively). Although more experimentation is necessary to understand the long-term response and succession of coral rubble communities under projected conditions, these results suggest that rates of carbonate loss will increase in coral rubble as pH and calcium carbonate saturation states are reduced. This study demonstrates a need to thoroughly investigate the contribution of coral rubble to the overall carbonate budget, reef resilience, recovery, and function under future conditions.

  19. A review: Different methods producing different particles size and distribution in synthesis of calcium carbonate nano particles

    Science.gov (United States)

    Sulimai, N. H.; Rusop, M.; Alrokayan, Salman A. H.; Khan, Haseeb A.

    2016-07-01

    Carbonates exist as 73 percent of world crust carbon. Abundance and bioavailability of Calcium Carbonates offer reliable resources, costs saving and environmental friendly potentials in its applications. Studies proven nano-sized Calcium Cabonate (nCC) employs a more significant characteristics compared to larger sizes. Properties of nCC is affected by the dispersion of the particles in which agglomeration occurs. It is important to gain more understanding of the conditions contributing or stunting the agglomeration to gain more control of the particles morphology and dynamic. A few recent studies with different methods to prepare calcium carbonate nanoparticles were listed in Table 1 .Particle size and dispersity of calcium carbonate are affected by different conditions of its preparation. Other factors such as mechanical aggression, concentration of solution, temperature of precipitation, pH of reaction are all contributing factors towards particle sizes and distribution.

  20. Evolution of supersaturation of amorphous pharmaceuticals: nonlinear rate of supersaturation generation regulated by matrix diffusion.

    Science.gov (United States)

    Sun, Dajun D; Lee, Ping I

    2015-04-06

    The importance of rate of supersaturation generation on the kinetic solubility profiles of amorphous systems has recently been shown by us; however, the previous focus was limited to constant rates of supersaturation generation. The objective of the current study is to further examine the effect of nonlinear rate profiles of supersaturation generation in amorphous systems, including (1) instantaneous or infinite rate (i.e., initial degree of supersaturation), (2) first-order rate (e.g., from dissolution of amorphous drug particles), and (3) matrix diffusion regulated rate (e.g., drug release from amorphous solid dispersions (ASDs) based on cross-linked poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels), on the kinetic solubility profiles of a model poorly soluble drug indomethacin (IND) under nonsink dissolution conditions. The previously established mechanistic model taking into consideration both the crystal growth and ripening processes was extended to predict the evolution of supersaturation resulting from nonlinear rates of supersaturation generation. Our results confirm that excessively high initial supersaturation or a rapid supersaturation generation leads to a surge in maximum supersaturation followed by a rapid decrease in drug concentration owing to supersaturation-induced precipitation; however, an exceedingly low degree of supersaturation or a slow rate of supersaturation generation does not sufficiently raise the supersaturation level, which results in a lower but broader maximum kinetic solubility profile. Our experimental data suggest that an optimal area-under-the-curve of the kinetic solubility profiles exists at an intermediate initial supersaturation level for the amorphous systems studied here, which agrees well with the predicted trend. Our model predictions also support our experimental findings that IND ASD in cross-linked PHEMA exhibits a unique kinetic solubility profile because the resulting supersaturation level is governed by a matrix

  1. An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

    Institute of Scientific and Technical Information of China (English)

    XIAO Yingkai; LI Shizhen; WEI Haizhen; SUN Aide; ZHOU Weijian; LIU Weiguo

    2006-01-01

    Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally. The results show the clear positive relationships between boron concentration and δ11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic fractionation between inorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis that B(OH)4- is the dominant species incorporated into the biogenic calcite structure. The isotopic fractionation factors α Between synthetic calcium carbonate precipitate and parent solutions increase systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072 at pH 8.60 for seawater and from 0.9826 at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopic fractionation factor of larger than 1 in synthetic calcium carbonate precipitated from seawater/saline water at higher pH is observed, which implies that a substantial amount of the isotopically heavier B(OH)3 species must be incorporated preferentially into synthetic inorganic carbonate. The results propose that the incorporation of B(OH)3 is attributed to the formation of Mg(OH)2 at higher pH of calcifying microenvironment during the synthetic calcium carbonate precipitation. The preliminary experiment of Mg(OH)2 precipitated from artificial seawater shows that heavier 11B is enriched in Mg(OH)2 precipitation, which suggests that isotopically heavier B(OH)3 species incorporated preferentially into Mg(OH)2 precipitation.This result cannot be applied to explain the boron isotopic fractionation of marine bio-carbonate because of the possibility that the unusual environment in this study appears in formation of marine bio-carbonate is infinitesimal. We, however, must pay more attention to this phenomenon observed in this study, which accidentally appears in especially natural environment.

  2. Chromium isotope fractionation during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes

    The chromium (Cr) isotopic composition of carbonates can potentially be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenvironmental changes, for example related to the rise of oxygen during the Ar...... et al., 2007, Water Air Soil Poll. 179, 381-390. [2] Sánchez-Pastor et al., 2011, Cryst. Growth Des. 11, 3081-3089....

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

    Directory of Open Access Journals (Sweden)

    Taylor Joanna

    2011-09-01

    Full Text Available Abstract 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

  4. 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

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

    Science.gov (United States)

    Wu, Yuxin; Ajo-Franklin, Jonathan B; Spycher, Nicolas; Hubbard, Susan S; Zhang, Guoxiang; Williams, Kenneth H; Taylor, Joanna; Fujita, Yoshiko; Smith, Robert

    2011-09-23

    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 NH4

  6. Amorphous calcium carbonate precipitation by cellular biomineralization in mantle cell cultures of Pinctada fucata.

    Directory of Open Access Journals (Sweden)

    Liang Xiang

    Full Text Available The growth of molluscan shell crystals is generally thought to be initiated from the extrapallial fluid by matrix proteins, however, the cellular mechanisms of shell formation pathway remain unknown. Here, we first report amorphous calcium carbonate (ACC precipitation by cellular biomineralization in primary mantle cell cultures of Pinctada fucata. Through real-time PCR and western blot analyses, we demonstrate that mantle cells retain the ability to synthesize and secrete ACCBP, Pif80 and nacrein in vitro. In addition, the cells also maintained high levels of alkaline phosphatase and carbonic anhydrase activity, enzymes responsible for shell formation. On the basis of polarized light microscopy and scanning electron microscopy, we observed intracellular crystals production by mantle cells in vitro. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed the crystals to be ACC, and de novo biomineralization was confirmed by following the incorporation of Sr into calcium carbonate. Our results demonstrate the ability of mantle cells to perform fundamental biomineralization processes via amorphous calcium carbonate, and these cells may be directly involved in pearl oyster shell formation.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sivasankar, V., E-mail: vsivasankar@tce.edu [Department of Chemistry, Thiagarajar College of Engineering (Autonomous), Madurai 625015, Tamil Nadu (India); Rajkumar, S. [Department of Chemistry, Thiagarajar College of Engineering (Autonomous), Madurai 625015, Tamil Nadu (India); Murugesh, S. [Department of Chemistry, SACS M.A.V.M.M. Engineering College, Madurai 625301, Tamil Nadu (India); Darchen, A. [UMR CNRS No. 6226 Sciences Chimiques de Rennes, ENSCR, Avenue du General Leclerc, CS 50837, 35708 Rennes, Cedex 7 (France)

    2012-07-30

    Highlights: Black-Right-Pointing-Pointer The carbonization of Tamarind fruit shell improved its defluoridation efficiency. Black-Right-Pointing-Pointer Calcium carbonate particles were involved in the defluoridation process. Black-Right-Pointing-Pointer Adsorbent dose, pH, and fluoride concentration showed significant effects. Black-Right-Pointing-Pointer Maximum adsorption of fluoride was achieved at pH 7-8. Black-Right-Pointing-Pointer 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.

  8. 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.

  9. Carbonation acceleration of calcium hydroxide nanoparticles: induced by yeast fermentation

    Science.gov (United States)

    Lopez-Arce, Paula; Zornoza-Indart, Ainara

    2015-09-01

    Carbonation of Ca(OH)2 nanoparticles and consolidation of limestone are accelerated by high humidity and a yeast fermentation system that supplies a saturated atmosphere on CO2, H2O vapor and ethanol during 28 days. Nanoparticles were analyzed by X-ray diffraction and differential thermal analyses with thermogravimetry. Spectrophotometry, scanning electron microscopy analyses, and hydric and mechanical tests were also performed in stones specimens. Samples exposed to the yeast environment achieve 100 % relative CaCO3 yield, whereas at high humidity but without the yeast and under laboratory environment, relative yields of 95 % CaCO3 and 15 % CaCO3 are, respectively, reached, with white crusts and glazing left on the stone surfaces when the nanoparticles are applied at a concentration of 25 g/l. The largest increase in the drilling resistance and surface hardness values with slight increase in the capillarity absorption and desorption coefficients and with lesser stone color changes are produced at a concentration of 5 g/l, in the yeast system environment. This especially happens in stone specimens initially with bimodal pore size distributions, more amounts of pores with diameters between 0.1 and 1 µm, higher open porosity values and faster capillary coefficients. An inexpensive and reliable method based on water and yeast-sugar solution is presented to speed up carbonation of Ca(OH)2 nanoparticles used as a consolidating product to improve the mechanical properties of decayed limestone from archaeological and architectural heritage.

  10. Lithium and calcium carbides with polymeric carbon structures.

    Science.gov (United States)

    Benson, Daryn; Li, Yanling; Luo, Wei; Ahuja, Rajeev; Svensson, Gunnar; Häussermann, Ulrich

    2013-06-01

    We studied the binary carbide systems Li2C2 and CaC2 at high pressure using an evolutionary and ab initio random structure search methodology for crystal structure prediction. At ambient pressure Li2C2 and CaC2 represent salt-like acetylides consisting of C2(2-) dumbbell anions. The systems develop into semimetals (P3m1-Li2C2) and metals (Cmcm-Li2C2, Cmcm-CaC2, and Immm-CaC2) with polymeric anions (chains, layers, strands) at moderate pressures (below 20 GPa). Cmcm-CaC2 is energetically closely competing with the ground state structure. Polyanionic forms of carbon stabilized by electrostatic interactions with surrounding cations add a new feature to carbon chemistry. Semimetallic P3m1-Li2C2 displays an electronic structure close to that of graphene. The π* band, however, is hybridized with Li-sp states and changed into a bonding valence band. Metallic forms are predicted to be superconductors. Calculated critical temperatures may exceed 10 K for equilibrium volume structures.

  11. Influence of surface treatment of carbon fibers on electrochemical crystallization of calcium phosphate

    Institute of Scientific and Technical Information of China (English)

    TAO Ke; HUANG Su-ping; ZHOU Ke-chao

    2005-01-01

    Electrodeposition technique was used to coat calcium phosphate on carbon fiber which can be used to reinforce hydroxyapatite. The differences between fibers treated with and without nitric acid in electrodeposition were evaluated. The X-ray diffractometry results show that CaHPO4·2H2O is obtained as the kind of calcium phosphate coating on carbon fiber. The scanning electron microscopy photographs and deposit kinetic curve indicate that the influences of the functional group attained by nitric acid treatment, the crystal morphology and crystallization of the coating layers on the fiber with and without treatment rate are obviously different. The functional group, especially the acidic group, can act as nucleation centers of electrochemical crystallization.

  12. Dehydration and crystallization of amorphous calcium carbonate in solution and in air.

    Science.gov (United States)

    Ihli, Johannes; Wong, Wai Ching; Noel, Elizabeth H; Kim, Yi-Yeoun; Kulak, Alexander N; Christenson, Hugo K; Duer, Melinda J; Meldrum, Fiona C

    2014-01-01

    The mechanisms by which amorphous intermediates transform into crystalline materials are poorly understood. Currently, attracting enormous interest is the crystallization of amorphous calcium carbonate, a key intermediary in synthetic, biological and environmental systems. Here we attempt to unify many contrasting and apparently contradictory studies by investigating this process in detail. We show that amorphous calcium carbonate can dehydrate before crystallizing, both in solution and in air, while thermal analyses and solid-state nuclear magnetic resonance measurements reveal that its water is present in distinct environments. Loss of the final water fraction--comprising less than 15% of the total--then triggers crystallization. The high activation energy of this step suggests that it occurs by partial dissolution/recrystallization, mediated by surface water, and the majority of the particle then crystallizes by a solid-state transformation. Such mechanisms are likely to be widespread in solid-state reactions and their characterization will facilitate greater control over these processes.

  13. Heat mass transfer model of fouling process of calcium carbonate on heat transfer surface

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new heat mass transfer model was developed to predict the fouling process of calcium carbonate on heat transfer surface. The model took into account not only the crystallization fouling but also the particle fouling which was formed on the heat transfer surface by the suspension particles of calcium carbonate in the su- persaturated solution. Based on experimental results of the fouling process, the deposition and removal rates of the mixing fouling were expressed. Furthermore, the coupling effect of temperature with the fouling process was considered in the physics model. As a result the fouling resistance varying with time was obtained to describe the fouling process and the prediction was compared with experimental data under same conditions. The results showed that the present model could give a good prediction of fouling process, and the deviation was less than 15% of the experimental data in most cases. The new model is credible to predict the fouling process.

  14. The effect of glycine on the growth of calcium carbonate in alkaline silica gel

    Science.gov (United States)

    Gan, Xiong; He, Kunhuan; Qian, Baosong; Deng, Qin; Lu, Laixian; Wang, Yun

    2017-01-01

    Calcium carbonate was crystallized in alkaline silica gel with the presence of glycine. The crystallization proceeded with a counterdiffusion method by the reaction of calcium chloride and sodium carbonate. Optical microscopy observation showed a significant effect of glycine on the morphology control of calcite crystals. When the initial concentration of glycine was high enough (10 mg/mL, 20 mg/mL), spherical vaterite particles formed in alkaline silica gel concomitantly together with dumbbell shaped calcite particles. The in situ study by micro-Raman spectroscopy demonstrated that both vaterite and the concomitant calcite were stable phases during their growth processes since the initial appearance. A possible mechanism has been discussed to emphasize the effect of glycine on the nucleation of vaterite and the morphological control of calcite.

  15. Comparative study of calcium alginate, activated carbon, and their composite beads on methylene blue adsorption.

    Science.gov (United States)

    Hassan, A F; Abdel-Mohsen, A M; Fouda, Moustafa M G

    2014-02-15

    Three adsorbents, calcium alginate beads (AB), sodium hydroxide activated carbon based coconut shells (C), and calcium alginate/activated carbon composite beads (ACB) were prepared. Their textural properties were characterized by N2-adsorption at -196°C and scanning electron microscopy. The porosity, surface area and total pore volume of C>ACB>AB, but AB adsorbent was more acidic function groups more than the other adsorbents. Adsorption experiments were conducted to examine the effects of adsorbent dosage, pH, time, temperature and initial concentration of methylene blue. Methylene blue adsorption on C, AB and ACB was observed at pH>6 to avoid the competition of H(+). The amount of dye adsorbed increases as the adsorbent dosage increase. Adsorption of dye follows pseudo-second order mechanism. Thermodynamic studies show spontaneous and endothermic nature of the overall adsorption process.

  16. Calcium Carbonate versus Sevelamer Hydrochloride as Phosphate Binders after Long-Term Disease Progression in 5/6 Nephrectomized Rats

    Directory of Open Access Journals (Sweden)

    Suvi Törmänen

    2014-01-01

    Full Text Available Our aim was to compare the effects of calcium carbonate and sevelamer-HCl treatments on calcium-phosphate metabolism and renal function in 5/6 nephrectomized (NX rats so that long-term disease progression preceded the treatment. After 15-week progression, calcium carbonate (3.0%, sevelamer-HCl (3.0%, or control diets (0.3% calcium were given for 9 weeks. Subtotal nephrectomy reduced creatinine clearance (−40%, plasma calcidiol (−25%, and calcitriol (−70% and increased phosphate (+37%, parathyroid hormone (PTH (11-fold, and fibroblast growth factor-23 (FGF-23 (4-fold. In NX rats, calcium carbonate diet increased plasma (+20% and urinary calcium (6-fold, reduced plasma phosphate (−50% and calcidiol (−30%, decreased creatinine clearance (−35% and FGF 23 (−85%, and suppressed PTH without influencing blood pH. In NX rats, sevelamer-HCl increased urinary calcium (4-fold and decreased creatinine clearance (−45%, PTH (−75%, blood pH (by 0.20 units, plasma calcidiol (−40%, and calcitriol (−65%. Plasma phosphate and FGF-23 were unchanged. In conclusion, when initiated after long-term progression of experimental renal insufficiency, calcium carbonate diet reduced plasma phosphate and FGF-23 while sevelamer-HCl did not. The former induced hypercalcemia, the latter induced acidosis, while both treatments reduced vitamin D metabolites and deteriorated renal function. Thus, delayed initiation influences the effects of these phosphate binders in remnant kidney rats.

  17. Uniform supersaturated design and its construction

    Institute of Scientific and Technical Information of China (English)

    方开泰; 葛根年; 刘民千

    2002-01-01

    Supersaturated designs are factorial designs in which the number of main effects is greater than the number of experimental runs. In this paper, a discrete discrepancy is proposed as a measure of uniformity for supersaturated designs, and a lower bound of this discrepancy is obtained asa benchmark of design uniformity. A construction method for uniform supersaturated designs via resolvable balanced incomplete block designs is also presented along with the investigation of properties of the resulting designs. The construction method shows a strong link between these two different kinds of designs.

  18. Metal scavenging by calcium carbonate at the Eyjafjallajökull volcano

    DEFF Research Database (Denmark)

    Olsson, J.; Stipp, S. L S; Makovicky, E.

    2014-01-01

    in the Icelandic river, Hvanná, in the vicinity of the volcano. The river water emerged from under the lava flow and was heavily charged with cations and dissolved CO2. The concentration of the major dissolved constituents was: dissolved inorganic carbon (DIC), 33.08mM; calcium, 6.17mM; magnesium, 4.27mM; sodium...

  19. 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.

  20. The Impact of Adsorbed Triethylene Glycol on Water Wettability of the {1014} Calcium Carbonate Surface

    Science.gov (United States)

    Olsen, R.

    2015-12-01

    Water flooding is increasingly being used as a method of enhanced oil recovery and frequently involves calcium carbonate reservoirs. Very often, thermodynamic conditions in the upper few hundred meters allow for hydrate formation. One possible method of preventing hydrates is to inject hydrate inhibitors such as triethylene glycol (TEG) into the reservoir. Thus, it is of importance to know how such glycols affect water wettability, which is an important factor defining the oil behavior in such reservoirs. Wettability of a surface is defined by the contact angle of a liquid drop on the surface. The stronger the liquid is attracted to the surface, the smaller the wetting angle becomes, implying an increased degree of wetting. Therefore, it is possible to gain qualitative knowledge of the change in wetting properties with respect to external influences by studying corresponding changes in free energy of adsorption of the liquid. In our work [1], we used molecular dynamics (MD) and Born-Oppenheimer molecular dynamics (BOMD) to study how adsorbed TEG on the {1014} calcium carbonate surface affected adsorbed water. We used the changes in density profiles of water to estimate changes in adsorption free energy of water. The adaptive biasing force (ABF) method was applied to TEG to calculate the adsorption free energy of TEG on the calcium carbonate surface. We found that water wetting of the calcium carbonate surface decreased in the presence of adsorbed TEG. [1] - Olsen, R.; Leirvik, K.; Kvamme, B.; Kuznetsova, T. Adsorption Properties of Triethylene Glycol on a Hydrated {1014} Calcite Surface and Its Effect on Adsorbed Water, Langmuir 2015, DOI: 10.1021/acs.langmuir.5b02228

  1. Metal scavenging by calcium carbonate at the Eyjafjallajökull volcano

    DEFF Research Database (Denmark)

    Olsson, J.; Stipp, S. L S; Makovicky, E.

    2014-01-01

    in the Icelandic river, Hvanná, in the vicinity of the volcano. The river water emerged from under the lava flow and was heavily charged with cations and dissolved CO2. The concentration of the major dissolved constituents was: dissolved inorganic carbon (DIC), 33.08mM; calcium, 6.17mM; magnesium, 4.27mM; sodium...

  2. 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)

  3. REINFORCEMENT OF POLYDIMETHYLSILOXANE NETWORKS BY NANO-CALCIUM CARBONATE

    Institute of Scientific and Technical Information of China (English)

    Ya Peng; Rong-ni Du; Qiang Fu; Yue-lin Wang

    2005-01-01

    Although a number of investigations have been devoted to the analysis of silica or carbon black filled elastomer networks, little work has been done on the reinforcement of CaCO3 filled elastomer network. In this work, the reinforcement of polydimethylsiloxane (PDMS) network by using CaCO3 nano-particles was investigated. We have found a simultaneous increase of tensile strength, modulus and elongation with the increase in nano-CaCO3 content, which suggests that nanoCaCO3 panicles can indeed be used as a reinforcing agent, just like silica or carbon black. Interestingly, the tensile strength,modulus and elongation were seen to leave off for the first time when the content of nano-CaCO3 paticles reaches to 80%.PDMS also showed an enhanced elastic modulus and storage modulus with the increase in nano-CaCO3 content, particularly for samples with high nano-CaCO3 content. SEM was used to investigate the dispersion of the filler in PDMS matrix. A better dispersion was found for samples with high nano-CaCO3 content. A great increase of viscosity was found for samples with higher filler content, which is considered to be the reason for the good dispersion thus the reinforcement, because high viscosity will be helpful for breaking the agglomerates of fillers into small size particles under effect of shear. Our work provides a new way for the reinforcement of elastomer by using an adequate amount of nano-CaCO3 particles instead of a small quantity of silica, which is not only economically cheap but also very effective.

  4. Synthesis and Characterisation of Calcium Carbonate Aragonite Nanocrystals from Cockle Shell Powder (Anadara granosa

    Directory of Open Access Journals (Sweden)

    Abdullahi Shafiu Kamba

    2013-01-01

    Full Text Available The synthesis of pure calcium carbonate nanocrystals using a high pressure homogeniser (HPH via a microemulsion system produced uniform nanosized particles, which were characterised using transmission electron microscopy (TEM, field-emission scanning electron microscopy (FESEM, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, and thermogravimetric analysis (TGA. The identified particles were aragonite polymorphs with a rod shape and were approximately 50 nm in size. The aragonite polymorph of calcium carbonate was prepared from biogenic materials, cockle shells, and exhibited unique characteristics (i.e., a higher density than that of calcite, which makes it biocompatible and potentially suitable for applications in the medical, pharmaceutical, cosmetic, and paint industries. The methods adopted and the nonionic surfactant used in the synthesis of calcium carbonate nanocrystalline aragonite polymorphs were environmentally friendly and can be scaled up for industrial production. The sources are naturally available materials that are by-products of the seafood industry, which offers an opportunity for exploitation in numerous industrial applications.

  5. Compaction of functionalized calcium carbonate, a porous and crystalline microparticulate material with a lamellar surface.

    Science.gov (United States)

    Stirnimann, Tanja; Atria, Susanna; Schoelkopf, Joachim; Gane, Patrick A C; Alles, Rainer; Huwyler, Jörg; Puchkov, Maxim

    2014-05-15

    In the present study, we aimed to characterize the compressibility and compactibility of the novel pharmaceutical excipient, functionalized calcium carbonate (FCC). We studied three FCC modifications and compared the values for compressibility and compactibility with mannitol, microcrystalline cellulose (MCC), and ground calcium carbonate (CC 330) as well as mixtures of paracetamol and MCC or FCC at drug loads of 0%, 25%, 50%, 75%, and 100% (w/w). We used Heckel analysis, modified Heckel analysis, and Leuenberger analysis to characterize the compaction and compression behavior of the mixtures. Compaction analysis of FCC showed this material to markedly differ from ground calcium carbonate, exhibiting properties, i.e. plastic deformability, similar to those of MCC. This effect was attributed to the highly lamellar structure of FCC particles whose thickness is of the order of a single crystal unit cell. According to Leuenberger parameters, we concluded that FCC-based tablet formulations had mechanical properties equal or superior to those formulated with MCC. FCC tablets with high tensile strength were obtained already at low compressive pressures. Owing to these favorable properties (i.e. marked tensile strength and porosity), FCC promises to be suitable for the preparation of solid dosage forms.

  6. Characterization of calcium carbonate obtained from oyster and mussel shells and incorporation in polypropylene

    Directory of Open Access Journals (Sweden)

    Michele Regina Rosa Hamester

    2012-04-01

    Full Text Available There is a high content of calcium carbonate in mussel and oyster shells, which can be used in the formulation of medicine, in construction or as filler in polymer materials. This work has as its main objective to obtain calcium carbonate from mussel and oyster shells and used as filler in polypropylene compared their properties with polypropylene and commercial calcium carbonate composites. The shellfish was milling and heated at 500 ºC for 2 hours. The powder obtained from shellfish were characterized by scanning electron microscopy (SEM, X-ray fluorescence, particle size distribution and abrasiveness and compared with commercial CaCO3 and mixed with polypropylene. The thermal and mechanical properties of polypropylene with CaCO3 obtained from oyster and mussel shells and with commercial CaCO3 were analysed. The results showed that CaCO3­ can be obtained from oyster and mussel shell and is technically possible to replace the commercial CaCO3 for that obtained from the shells of shellfish in polypropylene composites.

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

    Directory of Open Access Journals (Sweden)

    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.

  8. 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.

  9. 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.

  10. Heterogeneous uptake and reactivity of formic acid on calcium carbonate particles: a Knudsen cell reactor, FTIR and SEM study.

    Science.gov (United States)

    Al-Hosney, Hashim A; Carlos-Cuellar, Sofia; Baltrusaitis, Jonas; Grassian, Vicki H

    2005-10-21

    The heterogeneous uptake and reactivity of formic acid (HCOOH), a common gas-phase organic acid found in the environment, on calcium carbonate (CaCO(3)) particles have been investigated using a Knudsen cell reactor, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). FTIR measurements show that the adsorption of formic acid on the surface of calcium carbonate results in the formation of calcium formate. Besides calcium formate, carbonic acid is also a reaction product under dry conditions (dry conditions and at low pressures, the initial uptake coefficient of formic acid on CaCO(3) particles is measured to be 3 +/- 1 x 10(-3) and decreases as the surface saturates with adsorbed products. The maximum surface coverage of formic acid under dry conditions is determined to be (3 +/- 1)x 10(14) molecules cm(-2). Under humidified conditions (RH >10%), adsorbed water on the surface of the carbonate particles participates in the surface reactivity of these particles, which results in the enhanced uptake kinetics and extent of reaction of this organic acid on CaCO(3) as well as opens up several new reaction pathways. These reaction pathways include: (i) the water-assisted dissociation of carbonic acid to CO(2) and H(2)O and (ii) the formation of calcium formate islands and crystallites, as evident by SEM images. The results presented here show that adsorbed water plays a potentially important role in the surface chemistry of gas-phase organic acids on calcium carbonate particles.

  11. Diet, but not oral probiotics, effectively reduces urinary oxalate excretion and calciumoxalate supersaturation

    Science.gov (United States)

    Lieske, John C.; Tremaine, William J.; De Simone, Claudio; O’Connor, Helen M.; Li, Xujian; Bergstralh, Eric J.; Goldfarb, David S.

    2014-01-01

    We examined the effect of a controlled diet and two probiotic preparations on urinary oxalate excretion, a risk factor for calcium oxalate kidney stone formation, in patients with mild hyperoxaluria. Patients were randomized to a placebo, a probiotic, or a synbiotic preparation. This tested whether these probiotic preparations can increase oxalate metabolism in the intestine and/or decrease oxalate absorption from the gut. Patients were maintained on a controlled diet to remove the confounding variable of differing oxalate intake from food. Urinary oxalate excretion and calcium oxalate supersaturation on the controlled diet were significantly lower compared with baseline on a free-choice diet. Neither study preparation reduced urinary oxalate excretion nor calcium oxalate supersaturation. Fecal lactobacilli colony counts increased on both preparations, whereas enterococcal and yeast colony counts were increased on the synbiotic. Total urine volume and the excretion of oxalate and calcium were all strong independent determinants of urinary calcium oxalate supersaturation. Hence, dietary oxalate restriction reduced urinary oxalate excretion, but the tested probiotics did not influence urinary oxalate levels in patients on a restricted oxalate diet. However, this study suggests that dietary oxalate restriction is useful for kidney stone prevention. PMID:20736987

  12. Scientific Opinion on the safety assessment of the active substances, sodium erythorbate, sodium carbonate, sodium bicarbonate, iron sulphate, activated carbon, cellulose, calcium hydroxide, calcium chloride and water, for use as active system in food contact materials

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF

    2014-02-01

    Full Text Available This scientific opinion of EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids deals with the safety assessment of the active substances sodium erythorbate, sodium carbonate, sodium bicarbonate, iron sulfate, activated carbon, cellulose, calcium hydroxide, calcium chloride and water, used in mixture which is packed into sachets for absorbing oxygen/carbon dioxide emitting from/into the headspace surrounding packed food. All substances of this formulation have been evaluated and approved for use as additives in plastic food contact materials or as food additives. No migration of calcium, iron and sodium ions was detected. No volatile organic compounds other than carbon dioxide were detected at the limit of detection of 0.5 μg/l. The CEF Panel concluded that the use of the substances sodium erythorbate, sodium carbonate, sodium bicarbonate, iron sulfate, activated carbon, cellulose, calcium hydroxide, calcium chloride and water does not raise a safety concern when used in oxygen absorber/carbon dioxide emitter systems, in sachets that prevent the physical release of their contents into the food. The sachets are to be placed in the headspace of the packaging and as such may come into occasional contact with the food, e.g. during handling. The sachet should not come into direct contact with liquid foods or foods that have and external aqueous liquid phase on the surface (liquid or exudates.

  13. Comparison of in vitro and in vivo tests for determination of availability of calcium from calcium carbonate tablets.

    Science.gov (United States)

    Whiting, S J; Pluhator, M M

    1992-10-01

    In vitro tests of calcium (Ca) availability and the oral Ca load test were conducted on eight brands of calcium carbonate (CaCO3) tablets (products A-H) each providing 500 mg Ca. Data were collected over three experiments with nine to 11 healthy premenopausal women testing two to four products. Subjects followed a low Ca diet (less than 10 mmol/day). On test mornings, fasting subjects collected baseline urine for 2 hours (-2 to 0 hours), then ingested the tablet with water. Urine was collected from 0 to 2 hours and 2 to 4 hours; for products E-H, urine was collected for an additional 2 hours (4 to 6 hours). Blood was sampled at hours 0, 4 and 6 during testing of products E and F. Three in vitro tests were run: the United States Pharmacopeia (USP) dissolution test, USP disintegration test, and a disintegration test using vinegar. Ca excretion rose significantly at hours 2 to 4 (p less than 0.05) compared to baseline for seven products. Ca excretion either fell or remained constant between hours 4 and 6. Serum Ca rose and serum parathyroid hormone fell at hour 4, compared to fasting values, suggesting that 4 hours represents peak response time. In vivo availability, measured as the incremental increase in Ca excretion (mmol/mmol creatinine) in hours 2 to 4 compared to baseline, did not correlate significantly with results of the USP dissolution test but did with results of either the USP disintegration test or the vinegar test.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Surface-functionalized cockle shell–based calcium carbonate aragonite polymorph as a drug nanocarrier

    Directory of Open Access Journals (Sweden)

    Mohd Abd Ghafar SL

    2017-05-01

    Full Text Available Syairah Liyana Mohd Abd Ghafar,1 Mohd Zobir Hussein,2 Yaya Rukayadi,1,3 Md Zuki Abu Bakar Zakaria1,4 1Institute of Bioscience, 2Institute of Advance Technology, 3Department of Food Science, Faculty of Food Science and Technology, 4Department of Veterinary Preclinical Sciences, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Selangor, Malaysia Abstract: Calcium carbonate aragonite polymorph nanoparticles derived from cockle shells were prepared using surface functionalization method followed by purification steps. Size, morphology, and surface properties of the nanoparticles were characterized using transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, zetasizer, X-ray powder diffraction, and Fourier transform infrared spectrometry techniques. The potential of surface-functionalized calcium carbonate aragonite polymorph nanoparticle as a drug-delivery agent were assessed through in vitro drug-loading test and drug-release test. Transmission electron microscopy, field emission scanning electron microscopy, and particle size distribution analyses revealed that size, morphology, and surface characterization had been improved after surface functionalization process. Zeta potential of the nanoparticles was found to be increased, thereby demonstrating better dispersion among the nanoparticles. Purification techniques showed a further improvement in the overall distribution of nanoparticles toward more refined size ranges <100 nm, which specifically favored drug-delivery applications. The purity of the aragonite phase and their chemical analyses were verified by X-ray powder diffraction and Fourier transform infrared spectrometry studies. In vitro biological response of hFOB 1.19 osteoblast cells showed that surface functionalization could improve the cytotoxicity of cockle shell–based calcium carbonate aragonite nanocarrier. The sample was also sensitive to pH changes and

  15. Can Supersaturation Affect Protein Crystal Quality?

    Science.gov (United States)

    Gorti, Sridhar

    2013-01-01

    In quiescent environments (microgravity, capillary tubes, gels) formation of a depletion zone is to be expected, due either to limited sedimentation, density driven convection or a combination of both. The formation of a depletion zone can: Modify solution supersaturation near crystal; Give rise to impurity partitioning. It is conjectured that both supersaturation and impurity partitioning affect protein crystal quality and size. Further detailed investigations on various proteins are needed to assess above hypothesis.

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

    Energy Technology Data Exchange (ETDEWEB)

    Park, HyangKyu [Center for Underground Physics, Institute for Basic Science, 70, Yuseong-daero 1689-gil, Yuseong-gu, Daejeon, Korea, 305-811 (Korea, Republic of)

    2015-08-17

    The AMoRE (Advanced Mo based Rare process Experiment) collaboration is going to use calcium molybdate crystals to search for neutrinoless double beta decay of {sup 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.

  17. 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.

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

    Science.gov (United States)

    Lapenis, Andrei; Lawrence, Gregory; Buyantuev, Alexander

    2015-04-01

    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.

  19. Deposition of calcium carbonate in karst caves: role of bacteria in Stiffe's cave.

    Directory of Open Access Journals (Sweden)

    Ercole Claudia

    2001-01-01

    Full Text Available Bacteria make a significant contribution to the accumulation of carbonate in several natural habitats where large amounts of carbonates are deposited. However, the role played by microbial communities in speleothem formation (stalactites, stalagmites etc. in caves is still unclear. In bacteria carbonate is formed by autotrophic pathways, which deplete CO2 from the environment, and by heterotrophic pathways, leading to active or passive precipitation. We isolated cultivable heterotrophic microbial strains, able to induce CaCO3 precipitation in vitro, from samples taken from speleothems in the galleries of Stiffe’s cave, L’Aquila, Italy. We found a large number of bacteria in the calcite formations (1 x 104 to 5 x 109 cells g-1. Microscopic examination, in laboratory conditions at different temperatures, showed that most of the isolates were able to form calcium carbonate microcrystals. The most crystalline precipitates were observed at 32°C. No precipitation was detected in un-inoculated controls media or in media that had been inoculated with autoclaved bacterial cells. X-ray diffraction (XRD analysis showed that most of the carbonate crystals produced were calcite. Bacillus strains were the most common calcifying isolates collected from Stiffe’s Cave. Analysis of carbonate-solubilization capability revealed that the non-calcifying bacteria were carbonate solubilizers.

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

    Directory of Open Access Journals (Sweden)

    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.

  1. 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.

  2. Hydration Characteristics of Tetracalcium Alumino-Ferrite Phase in the presence Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    M. M. Radwan

    2011-12-01

    Full Text Available Tetracalcium alumino-ferrite phase (C4AF prepared from pure starting materials was employed for composing various mixes prepared of C4AF phase, CaSO4·2H2O, Ca(OH2 and CaCO3. The effect of replacing calcium sulphate (gypsum by calcium carbonate as a set retarder on the hydration behaviour of ferrite phase was studied. The mixes were hydrated for various periods and the hydration products were investigated using the appropriate techniques. The kinetics of hydration was studied by measuring the chemically-combined water as well as the combined lime contents. The mineralogical constitution was studied by using XRD, and DTA. The microstructure of some represented hydrated samples was investigated by scanning electron microscopy. Some interesting conclusions have been drawn. It was found that calcium carbonate reacts with tetracalcium alumino-ferrite phase (C4AF in the presence of hydrolime [Ca(OH2] to form carboferrite compounds which may coat the aluminate grains as ettringite does and this may probably regulate the setting time.

  3. A Chemical Template for Synthesis of Molecular Sheets of Calcium Carbonate

    Science.gov (United States)

    Rianasari, Ina; Benyettou, Farah; Sharma, Sudhir Kumar; Blanton, Thomas; Kirmizialtin, Serdal; Jagannathan, Ramesh

    2016-05-01

    Inspired by the discovery of graphene and its unique properties, we focused our research to develop a scheme to create nacre like lamellar structures of molecular sheets of CaCO3 interleaved with an organic material, namely carbon. We developed a facile, chemical template technique, using a formulation of poly(acrylic) acid (PAA) and calcium acetate to create lamellar stacks of single crystal sheets of CaCO3, with a nominal thickness of 17 Å, the same as a unit-cell dimension for calcite (c-axis = 17.062 Å), interleaved with amorphous carbon with a nominal thickness of 8 Å. The strong binding affinity between carboxylate anions and calcium cations in the formulation was used as a molecular template to guide CaCO3 crystallization. Computational modeling of the FTIR spectra showed good agreement with experimental data and confirmed that calcium ions are bridged between polymer chains, resulting in a net-like polymer structure. The process readily lends itself to explore the feasibility of creating molecular sheets of other important inorganic materials and potentially find applications in many fields such as super capacitors and “low k di-electric” systems.

  4. From atoms to minerals: how calcium carbonates form and why we should care.

    Science.gov (United States)

    Diego Rodriguez-Blanco, Juan

    2017-04-01

    Calcium carbonate minerals are ubiquitous on Earth where they play a key role in many marine and terrestrial biomineralization processes, controlling the evolution of past and future ocean chemistry and a large part of the global carbon cycle. However, the mechanisms by which biominerals form and transform are not well understood because these processes frequently involve the formation of poorly-ordered and crystalline metastable phases (e.g., amorphous calcium carbonate, vaterite, monohydrocalcite). Furthermore, the degree of ordering, hydration and particle size of these phases and their crystallisation pathways are largely controlled by their origin and conditions of formation. These include a number of factors like temperature, pH, and concentration of foreign ions in solution (e.g., Mg2+, Sr2+, SO42-, organics, etc.). Over the last few years, new experimental and characterization approaches have been developed, combining classical characterization techniques with synchrotron-based methods that allow in situ and real-time monitoring of the reactions (e.g., time-resolved synchrotron-based scattering and diffraction, pair distribution function). These techniques have provided very useful data to attain the mechanisms and quantify the kinetics of crystallization in abiotic systems. I will present a series of results obtained from synchrotron- and lab-based experiments that shed light on the mechanisms of formation of a number of biominerals (e.g., vaterite, calcite, aragonite, monohydrocalcite, dolomite). These results provide a detailed understanding of how calcium carbonate phases form during biomineralization processes, the effects of seawater ions and organics during the formation and transformation of biominerals, and the implications for past and future ocean chemistry, CO2 capture and storage and industrial mineral synthesis.

  5. Isolation and characterization of biogenic calcium carbonate/phosphate from oral bacteria and their adhesion studies on YSZ-coated titanium substrate for dental implant application

    Indian Academy of Sciences (India)

    GOBI SARAVANAN KALIARAJ; KAMALAN KIRUBAHARAN; G PRADHABAN; P KUPPUSAMI; VINITA VISHWAKARMA

    2016-04-01

    Biogenic calcium carbonate/phosphate were isolated and characterized from oral bacteria (CPOB). The crystalline nature and morphology of calcium carbonate/phosphate were characterized by X-ray diffraction (XRD)and field emission scanning electron microscopy (FESEM), respectively. XRD analysis revealed the cubic phase of YSZ coating as well as biogenic calcium carbonate (rhombohedral) and calcium phosphate oxide (hexagonal) wasobserved from CPOB. FESEM confirmed the extracellular synthesis of calcium compounds. Bacterial adhesion result reveals that YSZ coating drastically reduce bacterial invasion than titanium substrate.

  6. 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

  7. Persistent Ice Supersaturation in Tropical Anvil Cirrus

    Science.gov (United States)

    Jensen, E.; Fridlind, A.; Ackerman, A.; Pfister, L.; Herman, R.; Bui, T.; Baumgardner, D.; Lawson, P.

    2003-12-01

    During the 2002 Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE), the NASA WB-57 spent many hours sampling cloud microphysical properties, temperature, turbulence, and water vapor concentration within subtropical anvil cirrus. These measurements indicate that air within the cirrus is often substantially supersaturated with respect to ice, with average ice supersaturations increasing from about 5 to 30% as cloud temperature decreases from 220 to 195 K. The persistence of large supersaturations in cirrus with high ice crystal surface areas is unexpected. In this study, we examine the dependence of the measured anvil supersaturations on parameters such as ice water content, turbulence, anvil age, and temperature. We also use a three-dimensional cloud model that resolves the size distributions of cloud particles to investigate the physical processes responsible for the maintenance of ice supersaturation in anvils. The effects of radiatively driven turbulence, wave-driven temperature oscillations, and entrainment of ambient air will be discussed.

  8. Dynamical characteristics of ice supersaturated regions

    Directory of Open Access Journals (Sweden)

    K. Gierens

    2012-12-01

    Full Text Available The typical distributions of dynamical fields within ice supersaturated regions are investigated. The dynamical fields divergence, relative vorticity, and vertical velocity are analysed statistically in two ways, namely using the unconditioned data and data conditioned on the presence of ice supersaturation. Two geographical regions are considered, namely Europe (250 hPa level and the tropical belt from 30° S to 30° N on two pressure levels (200 and 150 hPa. The study is based on forecast data from the European Centre for Medium-Range Weather Forecasts for four months covering the four seasons, June, September, December 2011 and March 2012. We find that histograms (frequency distributions and low order moments of the dynamical fields differ substantially and statistically significantly inside and outside of ice supersaturated regions. As expected, upward and divergent flow favours ice supersaturation. But we find also that ice supersaturation is mostly located in anti-cyclonic flow. The latter result is probably due to the structure of warm/moist and cold/dry air streams in synoptic disturbances in mid-latitudes, but probably merely coincidental in the tropical belt.

  9. Dynamical characteristics of ice supersaturated regions

    Directory of Open Access Journals (Sweden)

    K. Gierens

    2012-08-01

    Full Text Available The typical distributions of dynamical fields within ice supersaturated regions are investigated. The dynamical fields divergence, relative vorticity, and vertical velocity are analysed statistically in two ways, namely using the unconditioned data and data conditioned on the presence of ice supersaturation. Two geographical regions are considered, namely Europe (250 hPa level and the tropical belt from 30° S to 30° N on two pressure levels (200 and 150 hPa. The study is based on forecast data from the European Centre for Medium-Range Weather Forecasts for March 2012 solely. We find that histograms (frequency distributions and low order moments of the dynamical fields differ substantially and statistically significantly inside and outside of ice supersaturated regions. As expected, upward and divergent flow favours ice supersaturation. But we find also that ice supersaturation is mostly located in anti-cyclonic flow. The latter result is probably due to the structure of warm/moist and cold/dry air streams in synoptic disturbances in mid-latitudes, but probably merely coincidental in the tropical belt.

  10. Characterization of a biodegradable coralline hydroxyapatite/calcium carbonate composite and its clinical implementation.

    Science.gov (United States)

    Fu, Kun; Xu, Qingguo; Czernuszka, Jan; Triffitt, James T; Xia, Zhidao

    2013-12-01

    A partially converted, biodegradable coralline hydroxyapatite/calcium carbonate (CHACC) composite comprising a coral calcium carbonate scaffold enveloped by a thin layer of hydroxyapatite was used in the present study. The CHACC was characterized using powder x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The ability of the CHACC to promote conductive osteogenesis was assessed in vitro using human mesenchymal stem cells (hMSCs) and in vivo using an immunodeficient mouse model. The clinical performance of CHACC as a bone substitute to fill voids caused by excision of bone tumours was also observed in 16 patients. The CHACC was found to consist of two overlapping layers both morphologically and chemically. Hydroxyapatite formed a thin layer of nanocrystals on the surface and a thick rough crystal layer of around 30 µm in thickness enveloping the rock-like core calcium carbonate exoskeletal architecture. hMSCs cultured on CHACC in osteogenic medium demonstrated significant osteogenic differentiation. After subcutaneous implantation of CHACC incorporating osteogenically differentiated hMSCs and an anti-resorptive agent, risedronate, into an immunodeficient mouse model, bone formation was observed on the surface of the implants. Clinical application of CHACC alone in 16 patients for bone augmentation after tumour removal showed that after implantation, visible callus formation was observed at one month and clinical bone healing achieved at four months. The majority of the implanted CHACC was degraded in 18-24 months. In conclusion, CHACC appears to be an excellent biodegradable bone graft material. It biointegrates with the host, is osteoconductive, biodegradable and can be an attractive alternative to autogenous grafts.

  11. Influence of zinc on the calcium carbonate biomineralization of Halomonas halophila.

    Science.gov (United States)

    Rothenstein, Dirk; Baier, Johannes; Schreiber, Thomas D; Barucha, Vera; Bill, Joachim

    2012-12-01

    The salt tolerance of halophilic bacteria make them promising candidates for technical applications, like isolation of salt tolerant enzymes or remediation of contaminated saline soils and waters. Furthermore, some halophilic bacteria synthesize inorganic solids resulting in organic-inorganic hybrids. This process is known as biomineralization, which is induced and/or controlled by the organism. The adaption of the soft and eco-friendly reaction conditions of this formation process to technical syntheses of inorganic nano materials is desirable. In addition, environmental contaminations can be entrapped in biomineralization products which facilitate the subsequent removal from waste waters. The moderately halophilic bacteria Halomonas halophila mineralize calcium carbonate in the calcite polymorph. The biomineralization process was investigated in the presence of zinc ions as a toxic model contaminant. In particular, the time course of the mineralization process and the influence of zinc on the mineralized inorganic materials have been focused in this study. H. halophila can adapt to zinc contaminated medium, maintaining the ability for biomineralization of calcium carbonate. Adapted cultures show only a low influence of zinc on the growth rate. In the time course of cultivation, zinc ions accumulated on the bacterial surface while the medium depleted in the zinc contamination. Intracellular zinc concentrations were below the detection limit, suggesting that zinc was mainly bound extracellular. Zinc ions influence the biomineralization process. In the presence of zinc, the polymorphs monohydrocalcite and vaterite were mineralized, instead of calcite which is synthesized in zinc-free medium. We have demonstrated that the bacterial mineralization process can be influenced by zinc ions resulting in the modification of the synthesized calcium carbonate polymorph. In addition, the shape of the mineralized inorganic material is chancing through the presence of zinc ions

  12. Sucrose/bovine serum albumin mediated biomimetic crystallization of calcium carbonate

    Indian Academy of Sciences (India)

    Cheng-Li Yao; Wang-Hua Xu; Ai-Min Ding; Jin-Mao Zhu

    2009-01-01

    To understand the role of the sucrose/bovine serum albumin system in the biomineralization process, we have tested the influence of different concentration of the sucrose/bovine serum albumin (BSA) on calcium carbonate (CaCO3) precipitation. The CaCO3 crystals were characterized by scanning electron microscope (SEM), Fourier transform infrared spectrograph (FT-IR) and powder X-ray diffractometry (XRD). The possible formation mechanism of CaCO3 in the sucrose/bovine serum albumin system was discussed.

  13. Synthesis and structure of synthetically pure and deuterated amorphous (basic) calcium carbonates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hsiu-Wen; Daemen, Luke L.; Cheshire, Michael C.; Kidder, Michelle K.; Stack, Andrew G.; Allard, Lawrence F.; Neuefeind, Jörg; Olds, Daniel; Liu, Jue; Page, Katharine

    2017-01-01

    It is generally believed that H2O and OH- are the key species stabilizing and controlling amorphous calcium carbonate “polyamorph” forms, and may in turn control the ultimate crystallization products during synthesis and in natural systems. Yet, the locations and hydrogen-bonding network of these species in ACC have never been measured directly using neutron diffraction. We report a synthesis route that overcomes the existing challenges with respect to yield quantities and deuteration, both of which are critically necessary for high quality neutron studies.

  14. Radiation does response of calcium carbonate crystal in marine shells samples

    Directory of Open Access Journals (Sweden)

    Changkian, S.

    2002-01-01

    Full Text Available A study of the evolution of element, crystal structure and thermoluminescence signal versus gamma irradiation dose were carried out for calcite shells samples. The composition of element was studied by X-ray fluorescence spectrometer. As identified by X-ray diffraction and SEM/EDS analysis, two polymorphs of calcium-carbonate were extracted: calcite and aragonite. The evolution of TL signal versus gamma irradiation dose using the TL reader (Harshaw 2000 was initially dependent on crystal structure and fading effect of the thermoluminescence signal .

  15. Evolution of supersaturation of amorphous pharmaceuticals: the effect of rate of supersaturation generation.

    Science.gov (United States)

    Sun, Dajun D; Lee, Ping I

    2013-11-04

    The combination of a rapidly dissolving and supersaturating "spring" with a precipitation retarding "parachute" has often been pursued as an effective formulation strategy for amorphous solid dispersions (ASDs) to enhance the rate and extent of oral absorption. However, the interplay between these two rate processes in achieving and maintaining supersaturation remains inadequately understood, and the effect of rate of supersaturation buildup on the overall time evolution of supersaturation during the dissolution of amorphous solids has not been explored. The objective of this study is to investigate the effect of supersaturation generation rate on the resulting kinetic solubility profiles of amorphous pharmaceuticals and to delineate the evolution of supersaturation from a mechanistic viewpoint. Experimental concentration-time curves under varying rates of supersaturation generation and recrystallization for model drugs, indomethacin (IND), naproxen (NAP) and piroxicam (PIR), were generated from infusing dissolved drug (e.g., in ethanol) into the dissolution medium and compared with that predicted from a comprehensive mechanistic model based on the classical nucleation theory taking into account both the particle growth and ripening processes. In the absence of any dissolved polymer to inhibit drug precipitation, both our experimental and predicted results show that the maximum achievable supersaturation (i.e., kinetic solubility) of the amorphous solids increases, the time to reach maximum decreases, and the rate of concentration decline in the de-supersaturation phase increases, with increasing rate of supersaturation generation (i.e., dissolution rate). Our mechanistic model also predicts the existence of an optimal supersaturation rate which maximizes the area under the curve (AUC) of the kinetic solubility concentration-time profile, which agrees well with experimental data. In the presence of a dissolved polymer from ASD dissolution, these observed trends

  16. A comparative study of calcium absorption following a single serving administration of calcium carbonate powder versus calcium citrate tablets in healthy premenopausal women

    OpenAIRE

    Wang, Haiyuan; Bua, Peter; Capodice, Jillian

    2014-01-01

    Background: Calcium is an essential mineral often taken as a daily, long-term nutritional supplement. Data suggests that once-daily dosing is important with regard to long-term compliance of both drugs and nutritional supplements.Objective: This study was undertaken to compare the bioavailability of a single serving of two calcium supplements in healthy, premenopausal women.Design: A two-period, crossover bioavailability study of a single serving of calcium citrate tablets (two tablets=500 mg...

  17. A comparative study of calcium absorption following a single serving administration of calcium carbonate powder versus calcium citrate tablets in healthy premenopausal women

    OpenAIRE

    Haiyuan Wang; Peter Bua; Jillian Capodice

    2014-01-01

    Background: Calcium is an essential mineral often taken as a daily, long-term nutritional supplement. Data suggests that once-daily dosing is important with regard to long-term compliance of both drugs and nutritional supplements. Objective: This study was undertaken to compare the bioavailability of a single serving of two calcium supplements in healthy, premenopausal women. Design: A two-period, crossover bioavailability study of a single serving of calcium citrate tablets (two tablets=500 ...

  18. A comparative study of calcium absorption following a single serving administration of calcium carbonate powder versus calcium citrate tablets in healthy premenopausal women

    OpenAIRE

    Wang, Haiyuan; Bua, Peter; Capodice, Jillian

    2014-01-01

    Background Calcium is an essential mineral often taken as a daily, long-term nutritional supplement. Data suggests that once-daily dosing is important with regard to long-term compliance of both drugs and nutritional supplements. Objective This study was undertaken to compare the bioavailability of a single serving of two calcium supplements in healthy, premenopausal women. Design A two-period, crossover bioavailability study of a single serving of calcium citrate tablets (two tablets=500 mg ...

  19. The effect of brushing with toothpaste containing nano calcium carbonate upon nanofill composite resin surface roughness

    Science.gov (United States)

    Ramadhani, A. M.; Herda, E.; Triaminingsih, S.

    2017-08-01

    This study aims to determine the effect of brushing with toothpaste containing nanocalcium carbonate on the roughness of nanofill composite resin surface. Brushing was conducted with 3 types of materials for 3 consecutive brushing periods of 10 minutes each. Surface roughness was measured using a surface-roughness tester and the results were analyzed using the repeated ANOVA and the one-way ANOVA test. The surface morphology was observed using SEM after 3 months’ worth of brushing with the 3 materials. It was found that the nanofill composite resin surface-roughness value increased significantly (p<0.005) after brushing with toothpaste containing nano calcium carbonate for 3 months, but the value was not as high as that obtained when brushing with other types of toothpaste.

  20. Supersaturation of vertically propagating internal gravity waves

    Science.gov (United States)

    Lindzen, Richard S.

    1988-01-01

    The usual assumption that vertically propagating internal gravity waves will cease growing with height once their amplitudes are such as to permit convective instability anywhere within the wave is reexamined. Two factors lead to amplitude limitation: (1) wave clipping associated with convective mixing, and (2) energetic constraints associated with the rate at which the wave can supply energy to the convection. It is found that these two factors limit supersaturation to about 50 percent for waves with short horizontal wavelengths and high relative phase speeds. Usually the degree of supersaturation will be much less. These factors also lead to a gradual, rather than sudden, cessation of wave growth with height.

  1. The evolution of metazoan α-carbonic anhydrases and their roles in calcium carbonate biomineralization

    OpenAIRE

    Le Roy, Nathalie; Jackson, Daniel J.; Marie, Benjamin; Ramos-Silva, Paula; Marin, Frédéric

    2014-01-01

    The carbonic anhydrase (CA; EC 4.2.1.1) superfamily is a class of ubiquitous metallo-enzymes that catalyse the reversible hydration of carbon dioxide. The ?-CA family, present in all metazoan clades, is a key enzyme involved in a wide range of physiological functions including pH regulation, respiration, photosynthesis, and biocalcification. This paper reviews the evolution of the ?-CA family, with an emphasis on metazoan ?-CA members involved in biocalcification. Phylogenetic analyses reveal...

  2. 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.

  3. Experimental modelling of Calcium carbonate precipitation in the presence of phototrophic anaerobic bacteria Rhodovulum sp.

    Science.gov (United States)

    Bundeleva, Irina; Shirokova, Liudmila; Benezeth, Pascale; Pokrovsky, Oleg; Kompantseva, Elena

    2010-05-01

    -potential of the cells. To characterise the link between the rate of bacterial growth (biomass production) and the rate of CaCO3 precipitation, batch kinetic experiments were performed. These experiments were carried out in closed (anaerobic) bottles with initial concentration of calcium from 1 to 20 mM and from 5 to 20 mM bicarbonate. The biomass of cells, pH, [Ca2+] and [Alk] were measured as a function of time. Blank experiments (without cell or autoclaved cells) were always carried out. We found that the optimal conditions for both CaCO3 precipitation and biomass increase for the culture Rhodovulum sp. A-20s, is calcium concentration of 3 mM, whatever the concentration of bicarbonate (5, 10, 15 mM). Note also that for calcium concentration higher than 3 mM, the biomass production decreases. In the case of strictly anaerobic Rhodovulum sp. S-1765 bacteria, the optimal conditions for calcium carbonate precipitation is observed for the bicarbonate concentration of 10 mM, whatever the calcium concentration (3, 5, 10 mM). Overall, the present study allows quantitative modeling of bacterially-induced CaCO3 precipitation. It helps to distinguish between the effect of cell surface functional groups, surface electrical charge, soluble organic matter and metabolic change of solution pH on the rate and nature of precipitating calcium carbonate solid phase.

  4. A laboratory study of the heterogeneous reaction of nitric acid on calcium carbonate particles

    Science.gov (United States)

    Goodman, A. L.; Underwood, G. M.; Grassian, V. H.

    2000-12-01

    It has been postulated that the reaction of nitric acid with calcium carbonate, namely, CaCO3(s) + 2HNO3(g) → Ca(NO3)2(s) + CO2(g) + H2O(g), plays an important role in the atmosphere. In this study, transmission FTIR spectroscopy, diffuse reflectance UV-visible spectroscopy, transmission electron microscopy and a Knudsen cell reactor coupled to a quadrupole mass spectrometer have been used to investigate the heterogeneous reactivity of HNO3 on CaCO3 at 295 K as a function of relative humidity. Transmission FTIR spectroscopy was used to probe both gas-phase and adsorbed products and showed that the reaction of HNO3 and CaCO3 is limited to the surface of the CaCO3 particle in the absence of adsorbed water. However, in the presence of water vapor, the reaction is greatly enhanced and is not limited to the surface of the particle producing both solid calcium nitrate and gaseous carbon dioxide. The enhanced reactivity of the particles is attributed to the presence of a layer of adsorbed water on the particle surface. The amount of adsorbed water on the particle surface is strongly dependent on the extent of the reaction. This can be understood in terms of the increased hydrophilicity of calcium nitrate as compared to calcium carbonate. Data from experiments using a mass-calibrated Knudsen cell reactor showed the stoichiometry for the reaction determined from gas-phase species deviated from that expected from the balanced equation. Water adsorption on the particle surface and gases dissolved into the water layer appear to be the cause of this discrepancy. The measured uptake coefficient accounting for the BET area of the sample is determined to be 2.5±0.1×10-4 for HNO3 on CaCO3 under dry conditions and is found to increase in the presence of water vapor. Atmospheric implications of the results presented here are discussed.

  5. Assessing potential diagenetic alteration of primary iodine-to-calcium ratios in carbonate rocks

    Science.gov (United States)

    Hardisty, D. S.; Lu, Z.; Swart, P. K.; Planavsky, N.; Gill, B. C.; Loyd, S. J.; Lyons, T. W.

    2015-12-01

    We have evaluated iodine-to-calcium (I/Ca) ratios from a series of carbonate samples with well-constrained histories of diagenetic alteration to assess the likelihood of overprints on primary water column-derived signals. Because only the oxidized iodine species, iodate, is incorporated during carbonate precipitation, I/Ca ratios have strong potential as proxies for both marine redox and carbon cycling. This utility lies with the combination of iodate's redox sensitivity as well as the close association between iodine and marine organic matter. However, despite the possibility of large pore water iodine enrichments relative to overlying seawater, carbonate alteration under reducing diagenetic conditions, and iodate-to-iodide reduction, no study has assessed the prospect of diagenetic alteration of primary I/Ca ratios. Here, we evaluated aragonite-to-calcite transformations and dolomitization within the Key Largo Limestone of South Florida and the Clino and Unda drill cores of the Bahamas Bank. Also, early burial diagenesis was studied through analysis of I/Ca ratios in short cores from a variety of shallow settings within the Exuma Bay, Bahamas. Further, we evaluated authigenic carbonates through analysis of iodine in concretions constrained to have formed during varying stages of evolving pore fluid chemistry. In all cases, I/Ca ratios show the potential for diagenetic iodine loss relative to water-column derived values, consistent with observations of quantitative reduction of dissolved iodate to iodide in pore waters before or synchronous with carbonate alteration. In no case, however, did we observe an increase in I/Ca during diagenetic transformation. Our results suggest both that primary I/Ca values and trends can be preserved but that maximum I/Ca ratios should be considered a minimum estimate of seawater iodate. We recommend that ancient carbonates with distinct I/Ca trends not indicative of diagenetic iodine loss reflect preservation of or very early

  6. 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.

  7. Study on the thermal decomposition kinetics of nano-sized calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    李代禧; 史鸿运; 邓洁; 徐元植

    2003-01-01

    This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energy Ea; and that the top-temperature of decomposition Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.

  8. 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.

  9. Calcium Carbonate Storage in Amorphous Form and Its Template-Induced Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Han, T Y; Aizenberg, J

    2007-08-31

    Calcium carbonate crystallization in organisms often occurs through the transformation from the amorphous precursor. It is believed that the amorphous phase could be temporarily stabilized and stored, until its templated transition to the crystalline form is induced. Here we develop a bio-inspired crystallization strategy that is based on the above mechanism. Amorphous calcium carbonate (ACC) spherulitic particles are formed and stabilized on a self-assembled monolayer (SAM) of hydroxy-terminated alkanethiols on Au surface. The ACC is stored as a reservoir for ions and is induced to crystallize on command by introducing a secondary surface that is functionalized with carboxylic acid-terminated SAM. This secondary surface acts as a template for oriented and patterned nucleation. Various oriented crystalline arrays and micropatterned films are formed. We also show that the ACC phase can be doped with foreign ions (e.g. Mg) and organic molecules (e.g. dyes) and that these dopants later function as growth modifiers of calcite crystals and become incorporated into the crystals during the transformation process of ACC to calcite. We believe that our strategy opens the way of using a stabilized amorphous phase as a versatile reservoir system that can be converted in a highly controlled fashion to a crystalline form upon contacting the nucleating template.

  10. Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  12. Synthesis of three-dimensional calcium carbonate nanofibrous structure from eggshell using femtosecond laser ablation

    Directory of Open Access Journals (Sweden)

    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.

  13. 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.

  14. Adsorption studies of cadmium ions on alginate-calcium carbonate composite beads

    Science.gov (United States)

    Mahmood, Zahid; Amin, Athar; Zafar, Uzma; Raza, Muhammad Amir; Hafeez, Irfan; Akram, Adnan

    2017-05-01

    Alginate-calcium carbonate composite material was prepared in the form of beads and characterized using Fourier transform infra red (FT-IR) spectroscopy and scanning electron microscope (SEM) techniques. The adsorption of Cd2+ ions was studied through batch experiments. The adsorption parameters such as contact time (120 min), adsorbent dose (1.5 g), initial metal ion concentration(10 mg/L), pH (6) and agitation speed (150 rpm) were optimized at room temperature. Langmuir and Freundlich isotherms were applied to the data and it was noted that the adsorption of Cd2+ ions is better explained by Freundlich model. The kinetic studies showed that the adsorption of Cd2+ ions followed pseudo-first order kinetics. Thermodynamic parameters like ∆ G 0, ∆ H 0 and ∆ S 0 were calculated and on the basis of these values it was established that the adsorption process is feasible and endothermic in nature. It was concluded from the study that the composite material of alginate and calcium carbonate can effectively be used to recover Cd2+ ions from wastewater.

  15. Restoration of parathyroid function after change of phosphate binder from calcium carbonate to lanthanum carbonate in hemodialysis patients with suppressed serum parathyroid hormone.

    Science.gov (United States)

    Inaba, Masaaki; Okuno, Senji; Nagayama, Harumi; Yamada, Shinsuke; Ishimura, Eiji; Imanishi, Yasuo; Shoji, Shigeichi

    2015-03-01

    Control of phosphate is the most critical in the treatment of chronic kidney disease with mineral and bone disorder (CKD-MBD). Because calcium-containing phosphate binder to CKD patients is known to induce adynamic bone disease with ectopic calcification by increasing calcium load, we examined the effect of lanthanum carbonate (LaC), a non-calcium containing phosphate binder, to restore bone turnover in 27 hemodialysis patients with suppressed parathyroid function (serum intact parathyroid hormone [iPTH] ≦ 150 pg/mL). At the initiation of LaC administration, the dose of calcium-containing phosphate binder calcium carbonate (CaC) was withdrawn or reduced based on serum phosphate. After initiation of LaC administration, serum calcium and phosphate decreased significantly by 4 weeks, whereas whole PTH and iPTH increased. A significant and positive correlation between decreases of serum calcium, but not phosphate, with increases of whole PTH and iPTH, suggested that the decline in serum calcium with reduction of calcium load by LaC might increase parathyroid function. Serum bone resorption markers, such as serum tartrate-resistant acid phosphatase 5b, and N-telopeptide of type I collagen increased significantly by 4 weeks after LaC administration, which was followed by increases of serum bone formation markers including serum bone alkaline phosphatase, intact procollagen N-propeptide, and osteocalcin. Therefore, it was suggested that LaC attenuated CaC-induced suppression of parathyroid function and bone turnover by decreasing calcium load. In conclusion, replacement of CaC with LaC, either partially or totally, could increase parathyroid function and resultant bone turnover in hemodialysis patients with serum iPTH ≦ 150 pg/mL.

  16. 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

  17. Acrylic acid-allylpolyethoxy carboxylate copolymer dispersant for calcium carbonate and iron(III) hydroxide scales in cooling water systems

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Guangqing; Huang, Jingyi; Zhou, Yuming; Yao, Qingzhao; Ling, Lei; Zhang, Peixin; Fu, Change [Southeast Univ., Nanjing (China). School of Chemistry and Chemical Engineering; Wu, Wendao; Sun, Wei; Hu, Zhengjun [Jianghai Chemical Co., Ltd., Changzhou (China)

    2012-05-15

    A novel environmentally friendly type of calcium carbonate and iron(III) scale inhibitor (ALn) was synthesized. The anti-scale property of the Acrylic acid-allylpolyethoxy carboxylate copolymer (AA-APELn or ALn) towards CaCO{sub 3} and iron(III) in the artificial cooling water was studied through static scale inhibition tests. The observation shows that both calcium carbonate and iron(III) inhibition increase with increasing the degree of polymerization of ALn from 5 to 15, and the dosage of ALn plays an important role on calcium carbonate and iron(III)-inhibition. The effect on formation of CaCO{sub 3} was investigated with a combination of scanning electronic microscopy (SEM), Transmission electron microscopy (TEM), X-ray powder diffraction (XRD) analysis and Fourier transform infrared spectrometer, respectively. The results showed that the ALn copolymer not only influences calcium carbonate crystal morphology and crystal size but also the crystallinity. The crystallization of CaCO{sub 3} in the absence of inhibitor was rhombohedral calcite crystal, whereas a mixture of calcite with vaterite crystals was found in the presence of the ALn copolymer. Inhibition mechanism is proposed that the interactions between calcium or iron ions and polyethylene glycol (PEG) are the fundamental impetus to restrain the formation of the scale in cooling water systems. (orig.)

  18. Evidence for the involvement of carbonic anhydrase and urease in calcium carbonate formation in the gravity-sensing organ of Aplysia californica

    Science.gov (United States)

    Pedrozo, H. A.; Schwartz, Z.; Dean, D. D.; Harrison, J. L.; Campbell, J. W.; Wiederhold, M. L.; Boyan, B. D.

    1997-01-01

    To better understand the mechanisms that could modulate the formation of otoconia, calcium carbonate granules in the inner ear of vertebrate species, we examined statoconia formation in the gravity-sensing organ, the statocyst, of the gastropod mollusk Aplysia californica using an in vitro organ culture model. We determined the type of calcium carbonate present in the statoconia and investigated the role of carbonic anhydrase (CA) and urease in regulating statocyst pH as well as the role of protein synthesis and urease in statoconia production and homeostasis in vitro. The type of mineral present in statoconia was found to be aragonitic calcium carbonate. When the CA inhibitor, acetazolamide (AZ), was added to cultures of statocysts, the pH initially (30 min) increased and then decreased. The urease inhibitor, acetohydroxamic acid (AHA), decreased statocyst pH. Simultaneous addition of AZ and AHA caused a decrease in pH. Inhibition of urease activity also reduced total statoconia number, but had no effect on statoconia volume. Inhibition of protein synthesis reduced statoconia production and increased statoconia volume. In a previous study, inhibition of CA was shown to decrease statoconia production. Taken together, these data show that urease and CA play a role in regulating statocyst pH and the formation and maintenance of statoconia. CA produces carbonate ion for calcium carbonate formation and urease neutralizes the acid formed due to CA action, by production of ammonia.

  19. Mineralization of Calcium Carbonate on Multifunctional Peptide Assembly Acting as Mineral Source Supplier and Template.

    Science.gov (United States)

    Murai, Kazuki; Kinoshita, Takatoshi; Nagata, Kenji; Higuchi, Masahiro

    2016-09-13

    Crystal phase and morphology of biominerals may be precisely regulated by controlled nucleation and selective crystal growth through biomineralization on organic templates such as a protein. We herein propose new control factors of selective crystal growth by the biomineralization process. In this study, a designed β-sheet Ac-VHVEVS-CONH2 peptide was used as a multifunctional template that acted as mineral source supplier and having crystal phase control ability of calcium carbonate (CaCO3) during a self-supplied mineralization. The peptides formed three-dimensional nanofiber networks composed of assembled bilayer β-sheets. The assembly hydrolyzed urea molecules to one carbonate anion and two ammonium cations owing to a charge relay effect between His and Ser residues under mild conditions. CaCO3 was selectively mineralized on the peptide assembly using the generated carbonate anions on the template. Morphology of the obtained CaCO3 was fiber-like structure, similar to that of the peptide template. The mineralized CaCO3 on the peptide template had aragonite phase. This implies that CaCO3 nuclei, generated using the carbonate anions produced by the hydrolysis of urea on the surface of the peptide assembly, preferentially grew into aragonite phase, the growth axis of which aligned parallel to the direction of the β-sheet fiber axis.

  20. Removal of oxyanions from synthetic wastewater via carbonation process of calcium hydroxide: applied and fundamental aspects.

    Science.gov (United States)

    Montes-Hernandez, G; Concha-Lozano, N; Renard, F; Quirico, E

    2009-07-30

    Removal of oxyanions (selenite, selenate, arsenate, phosphate and nitrate) during calcite formation was experimentally studied using aqueous carbonation of calcium hydroxide under moderate pressure (P(CO2) congruent with 20 bar) and temperature (30 degrees C). The effects of Ca(OH)(2) dose (10 and 20 g), Ca(OH)(2) source (commercial pure material or alkaline paper mill waste) and oxyanion initial concentration (from 0 to 70 mg atom/L) were investigated for this anisobaric gas-liquid-solid system. The Ca(OH)(2) carbonation reaction allowed successfully the removal of selenite (>90%), arsenate (>78%) and phosphate (congruent with 100%) from synthetic solutions. Conversely, nitrate and selenate had not any physicochemical affinity/effect during calcite formation. The rate of CO(2) transfer during calcite formation in presence of oxyanions was equal or slower than for an oxyanion-free system, allowing to define a retarding kinetic factor RF that can vary between 0 (no retarding effect) to 1 (total inhibition). For selenite and phosphate RF was quite high, close to 0.3. A small retarding effect was detected for arsenate (RF approximately 0.05) and no retarding effect was detected for selenate and nitrate (RF approximately 0). In general, RF depends on the oxyanion initial concentration, oxyanion nature and Ca(OH)(2) dose. The presence of oxyanions could also influence the crystal morphology and aggregation/agglomeration process. For example, a c-axis elongation of calcite crystals was clearly observed at the equilibrium, for calcite formation in presence of selenite and phosphate. The oxyanions removal process proposed herein was inspired on the common physicochemical treatment of wastewater using calcium hydroxide (Ca(OH)(2)). The particularity, for this novel method is the simultaneous calcium hydroxide carbonation with compressed carbon dioxide in order to stabilise the solid matter. This economical and ecological method could allow the removal of various oxyanions

  1. Maintenance of supersaturation II: indomethacin crystal growth kinetics versus degree of supersaturation.

    Science.gov (United States)

    Patel, Dhaval D; Anderson, Bradley D

    2013-05-01

    This study compares the kinetics of crystal growth of indomethacin from supersaturated suspensions at varying degrees of supersaturation (2 ≤ S ≥ 9) in the presence of seed crystals of the γ-form of indomethacin, the lowest energy polymorph. At high S (6 ≤ S ≥ 9), the crystal growth was first order with rate coefficients (kG ) that were nearly constant and consistent with the value predicted for bulk-diffusion control. At lower S (supersaturation suggesting that a higher energy surface layer was deposited on the γ-form seed crystals during crystal growth. When growth experiments were repeated at low S in the presence of indomethacin seed crystals isolated from a previous crystal growth experiment (i.e., seed crystals having higher energy surface), kG matched the higher values observed for bulk diffusion-controlled crystal growth. Crystal growth experiments were also conducted at S supersaturation during oral absorption. Copyright © 2013 Wiley Periodicals, Inc.

  2. Export of calcium carbonate corrosive waters from the East Siberian Sea

    Science.gov (United States)

    Anderson, Leif G.; Ek, Jörgen; Ericson, Ylva; Humborg, Christoph; Semiletov, Igor; Sundbom, Marcus; Ulfsbo, Adam

    2017-04-01

    The Siberian shelf seas are areas of extensive biogeochemical transformation of organic matter, both of marine and terrestrial origin. This in combination with brine production from sea ice formation results in a cold bottom water of relative high salinity and partial pressure of carbon dioxide (pCO2). Data from the SWERUS-C3 expedition compiled on the icebreaker Oden in July to September 2014 show the distribution of such waters at the outer shelf, as well as their export into the deep central Arctic basins. Very high pCO2 water, up to ˜ 1000 µatm, was observed associated with high nutrients and low oxygen concentrations. Consequently, this water had low saturation state with respect to calcium carbonate down to less than 0.8 for calcite and 0.5 for aragonite. Waters undersaturated in aragonite were also observed in the surface in waters at equilibrium with atmospheric CO2; however, at these conditions the cause of under-saturation was low salinity from river runoff and/or sea ice melt. The calcium carbonate corrosive water was observed all along the continental margin and well out into the deep Makarov and Canada basins at a depth from about 50 m depth in the west to about 150 m in the east. These waters of low aragonite saturation state are traced in historic data to the Canada Basin and in the waters flowing out of the Arctic Ocean north of Greenland and in the western Fram Strait, thus potentially impacting the marine life in the North Atlantic Ocean.

  3. Iodine-to-calcium ratios in carbonates suggest a primary origin for the Precambrian Lomagundi and Shuram carbon isotope excursions

    Science.gov (United States)

    Hardisty, D. S.; Lu, Z.; Planavsky, N. J.; Osburn, M. R.; Bekker, A.; Lyons, T. W.

    2013-12-01

    Systematic increases in iodine-to-calcium ratios (I/Ca) in carbonates from both the Precambrian Lomagundi and Shuram carbonate carbon isotope (δ13Ccarb) excursion intervals suggest primary origins for these events. Iodate (IO3-), the oxidized iodine species, is the exclusive species incorporated into carbonates. The high redox sensitivity of IO3- to deoxygenation requires highly oxidizing fluids for IO3- production, making I/Ca in platform carbonates a simple indicator of the presence of oxidizing fluids in the surface ocean. Similarly, redox sensitivity makes the proxy host susceptible to diagenetic iodine loss during carbonate recrystallization in reducing pore fluids. Recent work has shown carbonates to experience near-complete iodine loss during dolomitization in the Permian, and work from our group evaluating modern and recent carbonates demonstrate the potential for diagenetic iodine loss during carbonate recrystallization. In some cases, however, such as meteoric aragonite-to-calcite transitions, oxidizing pore fluids have the potential to buffer IO3- concentrations, causing negligible alteration to primary I/Ca despite negative shifts in δ13Ccarb. These results highlight that diagenetic alterations to I/Ca and δ13Ccarb need not always be coupled, but importantly, no observed scenario promotes post-depositional addition of iodine to carbonates. This means that, independent of δ13Ccarb, systematic, stratigraphic increases in I/Ca ratios observed in the carbonate record are most easily interpreted as resulting from depositional controls such as surface ocean redox or shifts in the total marine iodine reservoir. From this, increasing I/Ca ratios coincident with rising and falling δ13Ccarb trends for the Paleoproterozic Lomagundi and Neoproterozoic Shuram events, respectively, support suggestions of a primary origin for the δ13Ccarb excursions. Significant increase in I/Ca in dolomites deposited during the Lomagundi excursion, rising from blank values in

  4. Biomineralization of electrospun poly(L-lactic acid)/gelatin composite fibrous scaffold by using a supersaturated simulated body fluid with continuous CO{sub 2} bubbling

    Energy Technology Data Exchange (ETDEWEB)

    Cai Qing; Xu Qingqing; Feng Qiaofang; Cao Xiaoyan [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Yang Xiaoping, E-mail: yangxp@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Deng Xuliang [School and Hospital of Stomatology, Peking University, Beijing 100081 (China)

    2011-09-15

    To promote the biomineralization, supersaturated simulated body fluids (SBFs), e.g. five times SBF (5 x SBF), were usually applied. In these SBFs, however, homogeneous nucleation of Ca-P mineralites and deposition unavoidably took place owing to the HCO{sub 3}{sup -} decomposition and the pH value increment, which made the prediction of bone bioactivity of substrates controversial. In this study, the classically prepared 5 x SBF was continuously bubbled with CO{sub 2} to keep the pH value stable at 6.4 and the solution transparent, and a kind of electrospun poly(L-lactic acid)/gelatin composite fibers was used for the biomineralization study. In such a modified 5 x SBF, heterogenenous nucleation occurred dominantly and thermodynamical unstable brushites (dicalcium phosphate dihydrate, DCPD) were detected shortly on both electrospun PLLA fibers and PLLA/gelatin (1:1 in weight) composite fibers. In comparison with electrospun PLLA fibers, the sheet-like DCPD mineralites transformed into flaky carbonated calcium-deficient hydroxyapatite (CDHA) within 24 h on the PLLA/gelatin composite fibers due to the accelerating effect of gelatin component. The formed apatite coating contained much less Mg{sup 2+} ions than that deposited in the classical 5 x SBF. The results of this study showed that supersaturated SBFs buffered with gassy CO{sub 2} were expected good choices for the accelerated biomineralization, and for the prediction of the bone bonding bioactivity of substrates.

  5. Stabilization and transformation of amorphous calcium carbonate: structural and kinetic studies

    Science.gov (United States)

    Schmidt, Millicent Promise

    Amorphous calcium carbonate (ACC) is a common transient precursor in the formation of more stable crystalline calcium carbonate minerals, most notably calcite, vaterite, and aragonite. Formation of ACC from calcium carbonate rich aqueous solution rather than direct crystallization of crystalline polymorphs by organisms provides several advantages: control of morphology, grain size, orientation, hardness, and other bulk properties as well as reduction of energy costs during growth cycles. Despite decades of study, stabilization and transformation mechanisms of synthetic and biogenic ACC remain unclear. In particular, the roles of H2O and inorganic phosphate in ACC structure and transformation, and the variables affecting transformation kinetics and polymorph selection are understudied. In this research, we addressed structure and kinetic behavior of ACC through four complementary investigations: two studies focus on synthetic ACC stabilization and two focus on synthetic and biogenic ACC transformation behavior in solution at ambient temperatures. We explored ACC stabilization via compositional and thermal analyses, X-ray scattering, X-ray absorption spectroscopy, and nuclear magnetic resonance spectroscopy. Transformation experiments used a novel method of in situ structural analysis that provided quantitative kinetic and structural data and allowed us to visualize the ACC transformation pathway. Results revealed the complexity of H2O structure in ACC samples synthesized from three methods, indicating that the distinct hydrous populations produced define ACC behavior. Transformation kinetics and polymorph selection were strongly affected by the hydration state and type of synthetic ACC reacted. In situ transformation experiments also showed differences in kinetic behavior due to reaction medium. The structural role of hydrous components was again evident in in situ transformation experiments for ACC from a biogenic lobster gastrolith (LG) reacted with water. LG

  6. 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.

  7. Formation of amorphous calcium carbonate in caves and its implications for speleothem research

    Science.gov (United States)

    Demény, Attila; Németh, Péter; Czuppon, György; Leél-Őssy, Szabolcs; Szabó, Máté; Judik, Katalin; Németh, Tibor; Stieber, József

    2016-12-01

    Speleothem deposits are among the most valuable continental formations in paleoclimate research, as they can be dated using absolute dating methods, and they also provide valuable climate proxies. However, alteration processes such as post-depositional mineralogical transformations can significantly influence the paleoclimatic application of their geochemical data. An innovative sampling and measurement protocol combined with scanning and transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy is presented, demonstrating that carbonate precipitating from drip water in caves at ~10 °C contains amorphous calcium carbonate (ACC) that later transforms to nanocrystalline calcite. Stable oxygen isotope fractionations among calcite, ACC and water were also determined, proving that ACC is 18O-depleted (by >2.4 ± 0.8‰) relative to calcite. This, in turn, has serious consequences for speleothem-based fluid inclusion research as closed system transformation of ACC to calcite may induce a negative oxygen isotope shift in fluid inclusion water, resulting in deterioration of the original compositions. ACC formation increases the speleothems’ sensitivity to alteration as its interaction with external solutions may result in the partial loss of original proxy signals. Mineralogical analysis of freshly precipitating carbonate at the studied speleothem site is suggested in order to determine the potential influence of ACC formation.

  8. Chemically modified carbon paste ion-selective electrodes for determination of atorvastatin calcium in pharmaceutical preparations

    Directory of Open Access Journals (Sweden)

    Salwa Fares Rassi

    2017-06-01

    Full Text Available A simple, rapid and sensitive method for the determination of atorvastatin calcium in pharmaceutical preparations using two modified carbon paste electrodes was developed. One electrode (sensor A is based on ion-pair of atorvastatin with 5,6-diaminouracil hydrochloride (ATS-DAUH and the other (sensor B is based on atorvastatin with picric acid (ATS-PC. Among three different solvent mediators tested, dioctylphthalate (DOPH exhibited a proper behavior including Nernstian slopes of the calibration curve at 58.76 ± 0.8 and 57.48±1 mV per decade for sensors A and B. The response times were 10 and 12 s, detection limits 1.3 × 10−6 and 2.2 × 10−6 M; the concentration range 2.5 × 10−6-7.9 × 10−2 M and 3.0 × 10−6 to 7.9 × 10−2 M respectively. The present electrodes show good discrimination of atorvastatin calcium from several inorganic, organic ions, sugars and some common excipients. The sensors were applied for the determination of atorvastatin calcium in pharmaceutical preparations using standard addition and the calibration curve methods. The results obtained were satisfactory with excellent percentage recovery comparable and sometimes better than those obtained by other routine methods for the assay. The proposed potentiometric methods offer the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.

  9. Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition

    Science.gov (United States)

    Posavec, Lidija; Knijnenburg, Jesper T. N.; Hilty, Florentine M.; Krumeich, Frank; Pratsinis, Sotiris E.; Zimmermann, Michael B.

    2016-10-01

    Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO3) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO3 made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO3 and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO3, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca2P2O7 with increasing hydroxyapatite content at higher Ca:P. Aging of powders with Ca:P = 1.0 and 1.5 for over 500 days gradually increased particle size (but less than for CaCO3) without a change in phase composition or crystallinity. In 0.01 M H3PO4 calcium phosphate nanopowders dissolved ≈4 times more Ca than micronsized compounds and about twice more Ca than CaCO3 nanopowders, confirming that nanosizing and/or amorphous structuring sharply increases Ca powder dissolution. Because higher Ca solubility in vitro generally leads to greater absorption in vivo, these novel FASP-made Ca nanostructured compounds may prove useful for nutrition applications, including supplementation and/or food fortification.

  10. Influence of acid-soluble proteins from bivalve Siliqua radiata ligaments on calcium carbonate crystal growth

    Science.gov (United States)

    Huang, Zeng-Qiong; Zhang, Gang-Sheng

    2016-08-01

    In vitro biomimetic synthesis of calcium carbonate (CaCO3) in the presence of shell proteins is a heavily researched topic in biomineralization. However, little is known regarding the function of bivalve ligament proteins in the growth of CaCO3 crystals. In this study, using fibrous protein K58 from Siliqua radiata ligaments or coverslips as substrates, we report the results of our study of CaCO3 precipitation in the presence or absence of acid-soluble proteins (ASP) from inner ligament layers. ASP can disturb the controlling function of K58 or a coverslip on the crystalline phase, resulting in the formation of aragonite, calcite, and vaterite. In addition, we identified the following four primary components from ASP by mass spectroscopy: alkaline phosphatase (ALP), ABC transporter, keratin type II cytoskeletal 1 (KRT 1), and phosphate ABC transporter, phosphate-binding protein (PstS). Further analysis revealed that the first three proteins and especially ALP, which is important in bone mineralisation, could affect the polymorphism and morphology of CaCO3 crystals by trapping calcium ions in their domains. Our results indicate that ALP may play an important role in the formation of aragonite in S. radiata ligaments. This paper may facilitate our understanding of the biomineralization process.

  11. Calcium carbonate formation on mica supported extracellular polymeric substance produced by Rhodococcus opacus

    Science.gov (United States)

    Szcześ, Aleksandra; Czemierska, Magdalena; Jarosz-Wilkołazka, Anna

    2016-10-01

    Extracellular polymeric substance (EPS) extracted from Rhodococcus opacus bacterial strain was used as a matrix for calcium carbonate precipitation using the vapour diffusion method. The total exopolymer and water-soluble exopolymer fraction of different concentrations were spread on the mica surface by the spin-coating method. The obtained layers were characterized using the atomic force microscopy measurement and XPS analysis. The effects of polymer concentration, initial pH of calcium chloride solution and precipitation time on the obtained crystals properties were investigated. Raman spectroscopy and scanning electron microscopy were used to characterize the precipitated minerals. It was found that the type of precipitated CaCO3 polymorph and the crystal size depend on the kind of EPS fraction. The obtained results indicates that the water soluble fraction favours vaterite dissolution and calcite growth, whereas the total EPS stabilizes vaterite and this effect is stronger at basic pH. It seems to be due to different contents of the functional group of EPS fractions.

  12. Introduction of enzymatically degradable poly(trimethylene carbonate) microspheres into an injectable calcium phosphate cement.

    Science.gov (United States)

    Habraken, Wouter J E M; Zhang, Zheng; Wolke, Joop G C; Grijpma, Dirk W; Mikos, Antonios G; Feijen, Jan; Jansen, John A

    2008-06-01

    Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polyester with rubber-like properties. Introduction of this polymer into an injectable calcium phosphate bone cement can therefore be used to introduce macroporosity into the cement for tissue engineering purposes as well as to improve mechanical properties. Aim of this study was to investigate calcium phosphate cements with incorporated PTMC microspheres (PTMC CPCs) on their physical/mechanical properties and in vitro degradation characteristics. Therefore, composites were tested on setting time and mechanical strength as well as subjected to phosphate buffered saline (PBS) and enzyme containing medium. PTMC CPCs (12.5 and 25 wt%) with molecular weights of 52.7 kg mol(-1) and 176.2 kg mol(-1) were prepared, which showed initial setting times similar to that of original CPC. Though compression strength decreased upon incorporation of PTMC microspheres, elastic properties were improved as strain-at-yield increased with increasing content of microspheres. Sustained degradation of the microspheres inside PTMC CPC occurred when incubated in the enzymatic environment, but not in PBS, which resulted in an interconnected macroporosity for the 25 wt% composites.

  13. Nanoplasmonic smooth silica versus porous calcium carbonate bead biosensors for detection of biomarkers

    Energy Technology Data Exchange (ETDEWEB)

    Yashchenok, A.M.; Borisova, D.; Pinchasik, B.; Moehwald, H. [Department of Interfaces, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam (Germany); Parakhonskiy, B.V. [BIOtech center, University of Trento, 38123 Mattarello (Italy); Shubnikov Institute of Crystallography, Russian Academy of Science, Moscow (Russian Federation); Masic, A. [Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam (Germany); Skirtach, A.G. [Department of Interfaces, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam (Germany); Department of Molecular Biotechnology, Ghent University, 9000 Ghent, and Nano-Bio (NB)-Photonics, Ghent University, 9000 Ghent (Belgium)

    2012-11-15

    Nanoplasmonic biosensors based on gold nanoparticle functionalized smooth silica and porous calcium carbonate particles are presented. It is identified in this comparative study the role of porosity for adsorbing gold nanoparticles and subsequent detection of biomarkers. That is further applied in this study for detection of biomarkers. Detection of glucose - a biomarker of diabetes is studied together with that of bovine serum albumin - a very relevant bio-molecule. Raman scattering is used for label-free detection of molecules in the sub-{mu}M-mM range detection capabilities, which covers the range corresponding to healthy and diseased persons. Implications of current study for detection and identification of biomarkers are discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Deposition of calcium carbonate films by a polymer-induced liquid-precursor (PILP) process

    Science.gov (United States)

    Gower, Laurie B.; Odom, Damian J.

    2000-03-01

    A polypeptide additive has been used to transform the solution crystallization of calcium carbonate to a solidification process of a liquid-phase mineral precursor. In situ observations reveal that polyaspartate induces liquid-liquid phase separation of droplets of a mineral precursor. The droplets deposit on the substrate and coalesce to form a coating, which then solidifies into calcitic tablets and films. Transition bars form during the amorphous to crystalline transition, leading to sectorization of calcite tablets, and the defect textures and crystal morphologies are atypical of solution grown crystals. The formation of nonequilibrium crystal morphologies using an acidic polypeptide may have implications in the field of biomineralization, and the environmentally friendly aspects of this polymer-induced liquid-precursor (PILP) process may offer new techniques for aqueous-based processing of ceramic films, coatings, and particulates.

  15. Physico-chemical analysis of flexible polyurethane foams containing commercial calcium carbonate

    Directory of Open Access Journals (Sweden)

    Sabrina Sá e Sant'Anna

    2008-12-01

    Full Text Available Calcium carbonate (CaCO3 is a filler often utilized by the Brazilian mattress factories in the production of polyurethane foams. The filler allows the substitution of part of the polymeric agents, conferring dimensional stability and hardness to the foams. However, in agreement with experimental data, it is observed that the excess of commercial CaCO3 utilized in industry causes the increase of hysteresis, possibly causing permanent deformations and damaging the quality of the final product. In the present work, the physico-chemical analyses of the flexible polyurethane foams with different contents of CaCO3 were performed. The foams are submitted to the morphological, mechanical and positron analyses to verify the alterations provoked by the progressive introduction of this filler.

  16. Chiral acidic amino acids induce chiral hierarchical structure in calcium carbonate

    Science.gov (United States)

    Jiang, Wenge; Pacella, Michael S.; Athanasiadou, Dimitra; Nelea, Valentin; Vali, Hojatollah; Hazen, Robert M.; Gray, Jeffrey J.; McKee, Marc D.

    2017-04-01

    Chirality is ubiquitous in biology, including in biomineralization, where it is found in many hardened structures of invertebrate marine and terrestrial organisms (for example, spiralling gastropod shells). Here we show that chiral, hierarchically organized architectures for calcium carbonate (vaterite) can be controlled simply by adding chiral acidic amino acids (Asp and Glu). Chiral, vaterite toroidal suprastructure having a `right-handed' (counterclockwise) spiralling morphology is induced by L-enantiomers of Asp and Glu, whereas `left-handed' (clockwise) morphology is induced by D-enantiomers, and sequentially switching between amino-acid enantiomers causes a switch in chirality. Nanoparticle tilting after binding of chiral amino acids is proposed as a chiral growth mechanism, where a `mother' subunit nanoparticle spawns a slightly tilted, consequential `daughter' nanoparticle, which by amplification over various length scales creates oriented mineral platelets and chiral vaterite suprastructures. These findings suggest a molecular mechanism for how biomineralization-related enantiomers might exert hierarchical control to form extended chiral suprastructures.

  17. INFLUENCE OF SURFACE-MODIFICATION FOR CALCIUM CARBONATE ON THE INTERACTION BETWEEN THE FILLERS AND POLYDIMETHYLSILOXANE

    Institute of Scientific and Technical Information of China (English)

    Xiao-ming Xu; Xiao-le Tao; Qiang Zheng

    2008-01-01

    The surface of calcium carbonate (CaCO3) particles was modified with stearic acid (SA) and the chemicalstructures of the product were characterized by FT-IR analysis. The interaction between polydimethylsiloxane (PDMS) andCaCO3 fillers with different surface character was investigated by means of dynamic rheologicai and bound rubber tests foruncured compounds and mechanical properties measurements for the corresponding vulcanites. The results of dynamic testsindicate that with the increase of SA mass fraction, the span of the linear viscoelastic region broadens and the height of themodulus plateau decreases. The reasons for these are ascribed to that the SA decreases the surface energy of filler particlesand weakens their tendency to agglomerate. Moreover, the results of mechanical measurements reveal that the vulcanizedcompound filled with modified filler has a relative high tensile strength induced by a reinforced interaction between fillerand polymer matrix, which is confirmed by the bound rubber tests and transmission electron microscopy (TEM) observations.

  18. A New Method for Descaling Wool Fibres by Nano Abrasive Calcium Carbonate Particles in Ultrasonic Bath

    Directory of Open Access Journals (Sweden)

    Ali rezaghasemi

    2016-08-01

    Full Text Available Up to now, the most conventional methods for descaling of wool fibre are based on chemical degradation and resin covering of scales or a combination of them. These methods are producing wastewater and can cover physical properties of the fibres beside scales orderly. In this study, a new and clean method is developed on the basis of abrasion effect of calcium carbonate Nano particles (CCNP in an ultrasonic bath. Woolen Samples (fibre and yarn were sonicated with different levels of CCNP. Tensile properties of the yarns, directional friction effect of the fibres and scanning electron microscope images of the fibres were studied. Test results showed that sonicated Nano treatment of woolyarn reduced its tenacity, extension and work of rupture and increased its coefficient of friction. Scanning electron microscope images of fibres and measurement of fibres directional displacement confirmed descaling of Nano abrasive treated wool samples in comparison to the raw wool.

  19. Effect of precipitated calcium carbonate--Cellulose nanofibrils composite filler on paper properties.

    Science.gov (United States)

    He, Ming; Cho, Byoung-Uk; Won, Jong Myoung

    2016-01-20

    A new concept of composite filler was developed by using cellulose nanofibrils (CNF), precipitated calcium carbonate (PCC) and cationic starch (C-starch). In this study, cellulose nanofibrils were utilized in two different ways: a PCC-CNF composite filler and a papermaking additive in sheet forming. The aim was to elucidate their effects on flocculation, filler retention and the strength and optical properties of handsheets. The highest filler retention was obtained by using the PCC-CNF composite filler in paper sheets. The paper filled with the composite fillers had much higher bursting and tensile strengths than conventional PCC loading. It was also found that the paper prepared with PCC-CNF composite fillers became denser with increasing the filler content of paper.

  20. Effect of Hydraulic Activity on Crystallization of Precipitated Calcium Carbonate (PCC for Eco-Friendly Paper

    Directory of Open Access Journals (Sweden)

    Hwan Kim

    2009-11-01

    Full Text Available Wt% of aragonite, a CaCO3 polymorph, increased with higher hydraulic activity (°C of limestone in precipitated calcium carbonate (PCC from the lime-soda process (Ca(OH2-NaOH-Na2CO3. Only calcite, the most stable polymorph, was crystallized at hydraulic activity under 10 °C, whereas aragonite also started to crystallize over 10 °C. The crystallization of PCC is more dependent on the hydraulic activity of limestone than CaO content, a factor commonly used to classify limestone ores according to quality. The results could be effectively applied to the determination of polymorphs in synthetic PCC for eco-friendly paper manufacture.

  1. 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.

  2. Heterogeneous reactions of gaseous methanesulfonic acid with calcium carbonate and kaolinite particles

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Heterogeneous reactions of gaseous methanesulfonic acid (MSA) with calcium carbonate (CaCO3) and kaolinite particles at room temperature were investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC).Methanesulfonate (MS-) was identified as the product in the condensed phase,in accordance with the product of the reaction of gaseous MSA with NaCl and sea salt particles.When the concentration of gaseous MSA was 1.34 × 10-13 molecules cm-3,the uptake coefficient was (1.21 ± 0.06) × 10-8 (1) for the reaction of gaseous MSA with CaCO3 and (4.10 ± 0.65) × 10 10 (1) for the reaction with kaolinite.Both uptake coefficients were significantly smaller than those of the reactions of gaseous MSA with NaCl and sea salt particles.

  3. Influence of active sites organisation on calcium carbonate formation at model biomolecular interfaces

    Science.gov (United States)

    Hacke, S.; Möbius, D.; Lieu, V.-T.

    2005-06-01

    In an approach to understand the influence of structural parameters of interfaces on calcification in biomineralisation, the distribution and conformation of head groups as active sites in an inert matrix were varied using two-component phospholipid model monolayers. Dimyristoylphosphatidic acid (DMPA) and dipalmitoylphosphatidylcholin (DPPC), respectively, were the active components, and methyl octadecanoate (MOD) was used as inactive matrix. Surface pressure-area isotherms provide evidence for a different distribution of the active components in the matrix. Formation of solid calcium carbonate with two-component monolayers on subphases containing aqueous CaCO 3 was observed in situ by Brewster angle microscopy, where CaCO 3 domains appear bright. Striking differences in kinetics and extent of CaCO 3 formation are observed between monolayers containing dimyristoylphosphatidic acid and those containing dipalmitoylphosphatidylcholin. The presence of κ-carrageenan in the subphase as a further active component resulted in partial inhibition of CaCO 3 formation.

  4. 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.

  5. 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 o

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

    Science.gov (United States)

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

    2016-06-01

    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 Na2CO3 and CaCl2 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.

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

    NARCIS (Netherlands)

    Hu, Yu-Bin; Wolthers, Mariëtte|info:eu-repo/dai/nl/244773394; 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

  8. Non-ureolytic calcium carbonate precipitation by Lysinibacillus sp. YS11 isolated from the rhizosphere of Miscanthus sacchariflorus.

    Science.gov (United States)

    Lee, Yun Suk; Kim, Hyun Jung; Park, Woojun

    2017-06-01

    Although microbially induced calcium carbonate precipitation (MICP) through ureolysis has been widely studied in environmental engineering fields, urea utilization might cause environmental problems as a result of ammonia and nitrate production. In this study, many non-ureolytic calcium carbonate-precipitating bacteria that induced an alkaline environment were isolated from the rhizosphere of Miscanthus sacchariflorus near an artificial stream and their ability to precipitate calcium carbonate minerals with the absence of urea was investigated. MICP was observed using a phase-contrast microscope and ion-selective electrode. Only Lysinibacillus sp. YS11 showed MICP in aerobic conditions. Energy dispersive X-ray spectrometry and X-ray diffraction confirmed the presence of calcium carbonate. Field emission scanning electron microscopy analysis indicated the formation of morphologically distinct minerals around cells under these conditions. Monitoring of bacterial growth, pH changes, and Ca(2+) concentrations under aerobic, hypoxia, and anaerobic conditions suggested that strain YS11 could induce alkaline conditions up to a pH of 8.9 and utilize 95% of free Ca(2+) only under aerobic conditions. Unusual Ca(2+) binding and its release from cells were observed under hypoxia conditions. Biofilm and extracellular polymeric substances (EPS) formation were enhanced during MICP. Strain YS11 has resistance at high pH and in high salt concentrations, as well as its spore-forming ability, which supports its potential application for self-healing concrete.

  9. 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.

  10. Calcium Carbonate Precipitation by Bacillus and Sporosarcina Strains Isolated from Concrete and Analysis of the Bacterial Community of Concrete.

    Science.gov (United States)

    Kim, Hyun Jung; Eom, Hyo Jung; Park, Chulwoo; Jung, Jaejoon; Shin, Bora; Kim, Wook; Chung, Namhyun; Choi, In-Geol; Park, Woojun

    2016-03-01

    Microbially induced calcium carbonate precipitation (CCP) is a long-standing but re-emerging environmental engineering process for production of self-healing concrete, bioremediation, and long-term storage of CO2. CCP-capable bacteria, two Bacillus strains (JH3 and JH7) and one Sporosarcina strain (HYO08), were isolated from two samples of concrete and characterized phylogenetically. Calcium carbonate crystals precipitated by the three strains were morphologically distinct according to field emission scanning electron microscopy. Energy dispersive X-ray spectrometry mapping confirmed biomineralization via extracellular calcium carbonate production. The three strains differed in their physiological characteristics: growth at alkali pH and high NaCl concentrations, and urease activity. Sporosarcina sp. HYO08 and Bacillus sp. JH7 were more alkali- and halotolerant, respectively. Analysis of the community from the same concrete samples using barcoded pyrosequencing revealed that the relative abundance of Bacillus and Sporosarcina species was low, which indicated low culturability of other dominant bacteria. This study suggests that calcium carbonate crystals with different properties can be produced by various CCP-capable strains, and other novel isolates await discovery.

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

    Science.gov (United States)

    Jost, Adam B.; Mundil, Roland; He, Bin; Brown, Shaun T.; Altiner, Demir; Sun, Yadong; DePaolo, Donald J.; Payne, Jonathan L.

    2014-06-01

    A negative δC13 excursion in carbonate sediments near the Guadalupian/Lopingian (Middle/Late Permian) boundary has been interpreted to have resulted from a large carbon cycle disturbance during the end-Guadalupian extinction event (ca. 260 Ma). However, the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbation to the global carbon cycle. Calcium isotopes can be used to further constrain the cause of a carbon isotope excursion because the carbon and calcium cycles are coupled via CaCO3 burial. In this study, we present coupled carbon and calcium isotope records from three Guadalupian-Lopingian (G/L) sections in China (Penglaitan and Chaotian) and Turkey (Köserelik Tepe). The δC13 and δCa44/40 records differ among our studied sections and do not co-vary in the same manner. No section shows δC13 and δCa44/40 changes consistent with massive, rapid volcanic CO2 emissions or methane clathrate destabilization. Additionally, many sections with large (>3‰) changes in δC13 exhibit δO18 evidence for diagenetic alteration. Only one section exhibits a large excursion in the δCa44/40 of limestone but the absence of a similar excursion in the δCa44/40 of conodont apatite suggests that the limestone excursion reflects a mineralogical control rather than a perturbation to the global calcium cycle. Hence, we interpret the large isotopic changes observed in some sections to have resulted from local burial conditions or diagenetic effects, rather than from a large carbon and calcium cycle disturbance. Perturbations to the global carbon and calcium cycles across the G/L transition were much less intense than the disturbances that occurred across the subsequent Permian-Triassic boundary. This finding is consistent with the much smaller magnitude of the end-Guadalupian extinction relative to the end-Permian.

  12. GFP facilitates native purification of recombinant perlucin derivatives and delays the precipitation of calcium carbonate.

    Directory of Open Access Journals (Sweden)

    Eva Weber

    Full Text Available Insolubility is one of the possible functions of proteins involved in biomineralization, which often limits their native purification. This becomes a major problem especially when recombinant expression systems are required to obtain larger amounts. For example, the mollusc shell provides a rich source of unconventional proteins, which can interfere in manifold ways with different mineral phases and interfaces. Therefore, the relevance of such proteins for biotechnological processes is still in its infancy. Here we report a simple and reproducible purification procedure for a GFP-tagged lectin involved in biomineralization, originally isolated from mother-of-pearl in abalone shells. An optimization of E. coli host cell culture conditions was the key to obtain reasonable yields and high degrees of purity by using simple one-step affinity chromatography. We identified a dual functional role for the GFP domain when it became part of a mineralizing system in vitro. First, the GFP domain improved the solubility of an otherwise insoluble protein, in this case recombinant perlucin derivatives. Second, GFP inhibited calcium carbonate precipitation in a concentration dependent manner. This was demonstrated here using a simple bulk assay over a time period of 400 seconds. At concentrations of 2 µg/ml and higher, the inhibitory effect was observed predominantly for HCO(3 (- as the first ionic interaction partner, but not necessarily for Ca(2+. The interference of GFP-tagged perlucin derivatives with the precipitation of calcium carbonate generated different types of GFP-fluorescent composite calcite crystals. GFP-tagging offers therefore a genetically tunable tool to gently modify mechanical and optical properties of synthetic biocomposite minerals.

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

    Science.gov (United States)

    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

  14. 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.

  15. Experimental study on total dissolved gas supersaturation in water

    Directory of Open Access Journals (Sweden)

    Lu QU

    2011-12-01

    Full Text Available More and more high dams have been constructed and operated in China. The total dissolved gas (TDG supersaturation caused by dam discharge leads to gas bubble disease or even death of fish. Through a series of experiments, the conditions and requirements of supersaturated TDG generation were examined in this study. The results show that pressure (water depth, aeration, and bubble dissolution time are required for supersaturated TDG generation, and the air-water contact area and turbulence intensity are the main factors that affect the generation rate of supersaturated TDG. The TDG supersaturation levels can be reduced by discharging water to shallow shoals downstream of the dam or using negative pressure pipelines. Furthermore, the TDG supersaturation levels in stilling basins have no direct relationship with those in reservoirs. These results are of great importance for further research on the prediction of supersaturated TDG generation caused by dam discharge and aquatic protection.

  16. Study on conductance of supersaturated chloride microdroplets

    Institute of Scientific and Technical Information of China (English)

    HE KeJuan; CHENG Hua; ZHU YanYing; WANG LiangYu; ZHANG YunHong

    2009-01-01

    By using the measuring system previously designed by the authors,the conductance of KCI,NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range,especially in the supersaturation region,which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state.The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCI),75.7% and 93.3% (NaCl),and 69.9% and 96.6% (NH4Cl),respectively.In addition,it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.

  17. Study on conductance of supersaturated chloride microdroplets

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    By using the measuring system previously designed by the authors, the conductance of KCl, NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range, especially in the supersaturation region, which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state. The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCl), 75.7% and 93.3% (NaCl), and 69.9% and 96.6% (NH4Cl), respectively. In addition, it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.

  18. Decomposition of supersaturated sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    陈启元; 李洁; 尹周澜; 张平民

    2003-01-01

    The decomposition of supersaturated sodium aluminate solution in the process of alumina production was reviewed. Some fundamental problems, such as the structure of supersaturated sodium aluminate solution and the growth unit of gibbsite precipitation as well as the decomposition mechanism of sodium aluminate solution, were investigated by model analytic technique and theoretical calculation. It is found that the main Al-contained species is S4 symmetric [Al(OH)4(H2O)4]-. [Na+(H2O)4*Al(OH)-4] is found to form in intermediate concentrated solution while [Na+(H2O)2*Al(OH)-4] in highly concentrated solution. Meanwhile, it is proved that [(H2O)2Al(OH)4]- is the basic growth unit of gibbsite and [Al6(OH)18(H2O)6] is a favorable growth unit. Based on above results and ab initio quantum mechanical calculation and transition state theory, a reaction pathway of the decomposition of supersaturated sodium aluminate solution was put forward, in which the transformation of pentacoordinate aluminates ion to hexacoordinate basic growth unit as well as the formation of circled growth unit [Al6(OH)22(H2O)2]4- are the controlling steps.

  19. Impact of Micellar Surfactant on Supersaturation and Insight into Solubilization Mechanisms in Supersaturated Solutions of Atazanavir.

    Science.gov (United States)

    Indulkar, Anura S; Mo, Huaping; Gao, Yi; Raina, Shweta A; Zhang, Geoff G Z; Taylor, Lynne S

    2017-06-01

    The goals of this study were to determine: 1) the impact of surfactants on the "amorphous solubility"; 2) the thermodynamic supersaturation in the presence of surfactant micelles; 3) the mechanism of solute solubilization by surfactant micelles in supersaturated solutions. The crystalline and amorphous solubility of atazanavir was determined in the presence of varying concentrations of micellar sodium dodecyl sulfate (SDS). Flux measurements, using a side-by-side diffusion cell, were employed to determine the free and micellar-bound drug concentrations. The solubilization mechanism as a function of atazanavir concentration was probed using fluorescence spectroscopy. Pulsed gradient spin-echo proton nuclear magnetic resonance (PGSE-NMR) spectroscopy was used to determine the change in micelle size with a change in drug concentration. Changes in the micelle/water partition coefficient, K m/w , as a function of atazanavir concentration led to erroneous estimates of the supersaturation when using concentration ratios. In contrast, determining the free drug concentration using flux measurements enabled improved determination of the thermodynamic supersaturation in the presence of micelles. Fluorescence spectroscopic studies suggested that K m/w changed based on the location of atazanavir solubilization which in turn changed with concentration. Thus, at a concentration equivalent to the crystalline solubility, atazanavir is solubilized by adsorption at the micelle corona, whereas in highly supersaturated solutions it is also solubilized in the micellar core. This difference in solubilization mechanism can lead to a breakdown in the prediction of amorphous solubility in the presence of SDS as well as challenges with determining supersaturation. PGSE-NMR suggested that the size of the SDS micelle is not impacted at the crystalline solubility of the drug but increases when the drug concentration reaches the amorphous solubility, in agreement with the proposed changes in

  20. The Study of Thermal Decomposition of Natural Calcium Carbonate by the Temperature-programmed Mass Spectrometry Technique

    OpenAIRE

    S.N. Danilchenko; V.D. Chіvanov; A.G. Ryabishev; S.V. Novіkov; A.A. Stepanenko; V.N. Kuznetsov; E.V. Mironets; A.V. Marіychuk; A.A. Yanovska; O.G. Bordunova; A.N. Bugay

    2016-01-01

    The experiments have shown that the heating range for quantitative evolution of carbon dioxide gas (CO2) from natural calcium carbonates (e.g., chalk, corals, shells of the Anadara clams (Anadara inaequivalvis), shell of bird eggs) is from 500 to 850 C with a total heating time of 30-50 minutes. The only exception is the sample of a mortar from a masonry of Saint Sophia Cathedral (the architectural monument of XI century), in which the lowest border of the heating range for carbon dioxide ev...

  1. Mechanochemically Activated, Calcium Oxide-Based, Magnesium Oxide-Stabilized Carbon Dioxide Sorbents.

    Science.gov (United States)

    Kurlov, Alexey; Broda, Marcin; Hosseini, Davood; Mitchell, Sharon J; Pérez-Ramírez, Javier; Müller, Christoph R

    2016-09-01

    Carbon dioxide capture and storage (CCS) is a promising approach to reduce anthropogenic CO2 emissions and mitigate climate change. However, the costs associated with the capture of CO2 using the currently available technology, that is, amine scrubbing, are considered prohibitive. In this context, the so-called calcium looping process, which relies on the reversible carbonation of CaO, is an attractive alternative. The main disadvantage of naturally occurring CaO-based CO2 sorbents, such as limestone, is their rapid deactivation caused by thermal sintering. Here, we report a scalable route based on wet mechanochemical activation to prepare MgO-stabilized, CaO-based CO2 sorbents. We optimized the synthesis conditions through a fundamental understanding of the underlying stabilization mechanism, and the quantity of MgO required to stabilize CaO could be reduced to as little as 15 wt %. This allowed the preparation of CO2 sorbents that exceed the CO2 uptake of the reference limestone by 200 %.

  2. Atomistic simulations of calcium uranyl(VI) carbonate adsorption on calcite and stepped-calcite surfaces.

    Science.gov (United States)

    Doudou, Slimane; Vaughan, David J; Livens, Francis R; Burton, Neil A

    2012-07-17

    Adsorption of actinyl ions onto mineral surfaces is one of the main mechanisms that control the migration of these ions in environmental systems. Here, we present computational classical molecular dynamics (MD) simulations to investigate the behavior of U(VI) in contact with different calcite surfaces. The calcium-uranyl-carbonate [Ca(2)UO(2)(CO(3))(3)] species is shown to display both inner- and outer-sphere adsorption to the flat {101̅4} and the stepped {314̅8} and {31̅2̅16} planes of calcite. Free energy calculations, using the umbrella sampling method, are employed to simulate adsorption paths of the same uranyl species on the different calcite surfaces under aqueous condition. Outer-sphere adsorption is found to dominate over inner-sphere adsorption because of the high free energy barrier of removing a uranyl-carbonate interaction and replacing it with a new uranyl-surface interaction. An important binding mode is proposed involving a single vicinal water monolayer between the surface and the sorbed complex. From the free energy profiles of the different calcite surfaces, the uranyl complex was also found to adsorb preferentially on the acute-stepped {314̅8} face of calcite, in agreement with experiment.

  3. Influences of iron and calcium carbonate on wastewater treatment performances of algae based reactors.

    Science.gov (United States)

    Zhao, Zhimiao; Song, Xinshan; Wang, Wei; Xiao, Yanping; Gong, Zhijie; Wang, Yuhui; Zhao, Yufeng; Chen, Yu; Mei, Mengyuan

    2016-09-01

    The influences of iron and calcium carbonate (CaCO3) addition in wastewater treatments reactors performance were investigated. Adding different concentrations of Fe(3+) (5, 10, 30 and 50mmol/m(3)), iron and CaCO3 powder led to changes in algal characteristics and physico-chemical and microbiological properties. According to the investigation results, nutrient removal efficiency in algae based reactors was obviously increased by the addition of 10mmol/m(3) Fe(3+), iron (5mmol/m(3)) and CaCO3 powder (0.2gm(-3)) and the removal efficiencies of BOD5, TN, and TP in Stage 2 were respectively increased by 28%, 8.9%, and 22%. The improvements in physico-chemical performances were verified by microbial community tests (bacteria quantity, activity and community measured in most probable number, extracellular enzymes activity, and Biolog Eco Plates). Microbial variations indicated the coexistence of Fe ions and carbonate-bicarbonate, which triggered the synergistic effect of physico-chemical action and microbial factors in algae based reactors. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Pore-size-dependent calcium carbonate precipitation controlled by surface chemistry.

    Science.gov (United States)

    Stack, Andrew G; Fernandez-Martinez, Alejandro; Allard, Lawrence F; Bañuelos, José L; Rother, Gernot; Anovitz, Lawrence M; Cole, David R; Waychunas, Glenn A

    2014-06-03

    Induced mineral precipitation is potentially important for the remediation of contaminants, such as during mineral trapping during carbon or toxic metal sequestration. The prediction of precipitation reactions is complicated by the porous nature of rocks and soils and their interaction with the precipitate, introducing transport and confinement effects. Here X-ray scattering measurements, modeling, and electron microscopies were used to measure the kinetics of calcium carbonate precipitation in a porous amorphous silica (CPG) that contained two discrete distributions of pore sizes: nanopores and macropores. To examine the role of the favorability of interaction between the substrate and precipitate, some of the CPG was functionalized with a self-assembled monolayer (SAM) similar to those known to enhance nucleation densities on planar substrates. Precipitation was found to occur exclusively in macropores in the native CPG, while simultaneous precipitation in nanopores and macropores was observed in the functionalized CPG. The rate of precipitation in the nanopores estimated from the model of the X-ray scattering matched that measured on calcite single crystals. These results suggest that the pore-size distribution in which a precipitation reaction preferentially occurs depends on the favorability of interaction between substrate and precipitate, something not considered in most studies of precipitation in porous media.

  5. Synthesis of nanostructured carbon by chlorination of calcium carbide at moderate temperatures and its performance evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Dai Chunling [School of Chemistry, Xiangtan University, Hunan 411105 (China); Wang, Xianyou [School of Chemistry, Xiangtan University, Hunan 411105 (China)], E-mail: wxianyou@yahoo.com; Wang Ying [School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Hubei 430073 (China); Li Na; Wei Jianliang [School of Chemistry, Xiangtan University, Hunan 411105 (China)

    2008-12-01

    A new type of one-step preparation technique for the calcium carbide-derived carbon (CaC{sub 2}-CDC) was developed. In this study, CaC{sub 2}-CDC was synthesized from CaC{sub 2} in a freshly prepared chlorine environment in the temperature range of 100-600 deg. C. The structure and morphology of as-prepared CaC{sub 2}-CDC were studied by X-ray diffraction, transmission electron microscopy and nitrogen sorption experiment. Analysis of X-ray diffraction and transmission electron microscopy showed that CaC{sub 2}-CDC is an amorphous nanoporous material, and the structure depended on the synthesis temperature. The resultant carbon demonstrated narrow pore size distribution (PSD) and specific surface area (SSA) close to 800 m{sup 2} g{sup -1} (for nitrogen sorption) at a synthesized temperature of 100 deg. C. Increasing the reaction temperature above 400 deg. C resulted in a lower SSA of CaC{sub 2}-CDC due to the beginning of graphitization tendency. The nanoporous structure and narrow PSD of CaC{sub 2}-CDC indicated potential application as electrode materials in supercapacitor. The CaC{sub 2}-CDC exhibited a specific capacitance of 127.7 F g{sup -1} measured from the three-electrode cyclic voltammetry experiment at 10 mV s{sup -1}.

  6. 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.

  7. The formation of web-like connection among electrospun chitosan/PVA fiber network by the reinforcement of ellipsoidal calcium carbonate.

    Science.gov (United States)

    Sambudi, Nonni Soraya; Kim, Minjeong G; Park, Seung Bin

    2016-03-01

    The electrospun fibers consist of backbone fibers and nano-branch network are synthesized by loading of ellipsoidal calcium carbonate in the mixture of chitosan/poly(vinyl alcohol) (PVA) followed by electrospinning. The synthesized ellipsoidal calcium carbonate is in submicron size (730.7±152.4 nm for long axis and 212.6±51.3 nm for short axis). The electrospun backbone fibers experience an increasing in diameter by loading of calcium carbonate from 71.5±23.4 nm to 281.9±51.2 nm. The diameters of branch fibers in the web-network range from 15 nm to 65 nm with most distributions of fibers are in 30-35 nm. Calcium carbonate acts as reinforcing agent to improve the mechanical properties of fibers. The optimum value of Young's modulus is found at the incorporation of 3 wt.% of calcium carbonate in chitosan/PVA fibers, which is enhanced from 15.7±3 MPa to 432.4±94.3 MPa. On the other hand, the ultimate stress of fibers experiences a decrease. This result shows that the fiber network undergoes changes from flexible to more stiff by the inclusion of calcium carbonate. The thermal analysis results show that the crystallinity of polymer is changed by the existence of calcium carbonate in the fiber network. The immersion of fibers in simulated body fluid (SBF) results in the formation of apatite on the surface of fibers.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ben Amor, Y., E-mail: yasser_ben@yahoo.f [Institut Superieur des Sciences et Technologies de l' Environnement de Borj-Cedria, B.P 1003, Hammam-Lif 2050 (Tunisia); Bousselmi, L. [Laboratoire Traitement et Recyclage des Eaux, B.P 273, Hammam-Lif, Technopole de Borj-Cedria, 8020 Soliman (Tunisia); Tribollet, B. [UPR 15 CNRS - Physique des liquides et Electrochimie, Universite Pierre et Marie Curie - Tour 22, 4 place Jussieu, 75252 Paris Cedex 05 (France); Triki, E. [Unite de recherche Corrosion et Protection des metalliques, Ecole Nationale d' Ingenieurs de Tunis, P.B. 37, 1002 Tunis, Belvedere (Tunisia)

    2010-06-30

    Different allotropic forms of calcium carbonate scales were electrochemically deposited on a carbon steel surface in artificial underground Tunisian water at -0.95 V{sub SCE} and various Mg{sup 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{sub 3} crystals and the metallic surface.

  9. Ionising radiation effect on the luminescence emission of inorganic and biogenic calcium carbonates

    Energy Technology Data Exchange (ETDEWEB)

    Boronat, C. [CIEMAT, Av. Complutense 40, Madrid 28040 (Spain); Correcher, V., E-mail: v.correcher@ciemat.es [CIEMAT, Av. Complutense 40, Madrid 28040 (Spain); Virgos, M.D. [CIEMAT, Av. Complutense 40, Madrid 28040 (Spain); Garcia-Guinea, J. [CSIC, Museo Nacional Ciencias Naturales, José Gutiérrez Abascal 2, Madrid 28006 (Spain)

    2017-06-15

    Highlights: • Aragonite and biogenic Ca-carbonates could be used as a TL dosimeters. • TL can be employed for retrospective dosimetry purposes. • Calcium carbonates show an acceptable ionizing radiation sensitivity. • The stability of the radiation–induced TL remains, at least, till 700 h. - Abstract: As known, the luminescence emission of mineral phases could be potentially employed for dosimetric purposes in the case of radiological terrorism or radiation accident where conventional monitoring is not available. In this sense, this paper reports on the thermo- (TL) and cathodoluminescence (CL) emission of both biogenic (common periwinkle – littorina littorera – shell made of calcite 90% and aragonite 10%) and inorganic (aragonite 100%) Ca-rich carbonates previously characterized by X-ray diffraction and Raman spectroscopy. Whereas the aragonite sample displays the main CL waveband peaked in the red region (linked to point defects), the more intense emission obtained from the common periwinkle shell appears at higher energies (mainly associated with structural defects). The UV-blue TL emission of the samples, regardless of the origin, displays (i) an acceptable ionizing radiation sensitivity, (ii) linear dose response in the range of interest (up to 8 Gy), (iii) reasonable stability of the TL signal after 700 h of storage with an initial decay of ca. 88% for the mineral sample and 60% for the biogenic sample and maintaining the stability from 150 h onwards. (iv) The tests of thermal stability of the TL emission performed in the range of 180–320 °C confirm a continuum in the trap system.

  10. Kinetic versus thermodynamic factors in calcium renal lithiasis.

    Science.gov (United States)

    Grases, F; Costa-Bauzá, A; Königsberger, E; Königsberger, L C

    2000-01-01

    Calcium renal lithiasis formation depends on the balance between thermodynamic (supersaturation) and kinetic (inhibitors, nucleants) factors. In this paper, the importance of both groups was evaluated using (a) the complete urine analysis data obtained from 32 healthy volunteers and 141 active stone-formers, and (b) a comprehensive computer model to calculate the supersaturation values of calcium oxalate monohydrate, hydroxyapatite and brushite in each urine sample. The results of this evaluation were used to assess the possible effectiveness of a given pharmacological treatment.

  11. Photoinduced crystallization of calcium carbonate from a homogeneous precursor solution in the presence of partially hydrolyzed poly(vinyl alcohol)

    Science.gov (United States)

    Nishio, Takashi; Naka, Kensuke

    2015-04-01

    Photoinduced crystallization of calcium carbonate (CaCO3) was demonstrated by the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphenyl)propionic acid) under alkaline conditions (pH 10). In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol %) was used as the precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. Thermogravimetric analysis of the obtained xerogels showed that increasing the UV irradiation time increased the amount of CaCO3 formed and the complete conversion of calcium ions to calcite was achieved after 50 min of UV irradiation. Furthermore, solid phase analyses suggested that nanometer-to-micron-sized calcite crystals were formed and dispersed in the obtained PVAPS matrix.

  12. Monodispersed calcium carbonate nanoparticles modulate local pH and inhibit tumor growth in vivo

    Science.gov (United States)

    Som, Avik; Raliya, Ramesh; Tian, Limei; Akers, Walter; Ippolito, Joseph E.; Singamaneni, Srikanth; Biswas, Pratim; Achilefu, Samuel

    2016-06-01

    The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3 in tumors increases tumor pH over time. The associated induction of tumor growth stasis is putatively interpreted as a pHe increase. This study establishes an approach to prepare nano-CaCO3 over a wide particle size range, a formulation that stabilizes the nanomaterials in aqueous solutions, and a pH-sensitive nano-platform capable of modulating the acidic environment of cancer for potential therapeutic benefits.The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3

  13. Shallow cirrus convection – a source for ice supersaturation

    Directory of Open Access Journals (Sweden)

    Peter Spichtinger

    2014-09-01

    Full Text Available The origin and persistence of high ice supersaturation is still not well understood. In this study, the impact of local dynamics as source for ice supersaturation inside cirrus clouds is investigated. Nucleation and growth of ice crystals inside potentially unstable layers in the tropopause region might lead to shallow convection inside (layered cirrus clouds due to latent heat release. The intrinsic updraught inside convective cells constitutes a dominant but transient source for ice supersaturation. A realistic case of shallow cirrus convection is investigated using radiosonde data, meteorological analyses and large-eddy simulations of cirrus clouds. The simulations corroborate the existence of ice supersaturation inside cirrus clouds as a transient phenomenon. Ice supersaturation is frequent, but determined by the life cycle of convective cells in shallow cirrus convection. Cirrus clouds driven by shallow cirrus convection are mostly not in thermodynamic equilibrium; they are usually in a subsaturated or supersaturated state.

  14. Calcium carbonate saturation in the surface water of the Arctic Ocean: undersaturation in freshwater influenced shelves

    Directory of Open Access Journals (Sweden)

    M. Chierici

    2009-05-01

    Full Text Available In the summer of 2005, we sampled surface water and measured pH and total alkalinity (AT underway aboard IB Oden along the Northwest Passage from Cape Farwell (South Greenland to the Chukchi Sea. We investigated variability of carbonate system parameters, focusing particularly on carbonate concentration [CO32−] and calcium carbonate saturation states, as related to freshwater addition, biological processes and physical upwelling. Measurements on AT, pH at 15°C, salinity (S and sea surface temperature (SST, were used to calculate total dissolved inorganic carbon (DIC, [CO32−] and saturation of aragonite (ΩAr and calcite (ΩCa in the surface water. The same parameters were measured in the water column of the Bering Strait. Some surface waters in the Canadian Arctic Archipelago (CAA and on the Mackenzie shelf (MS were found to be undersaturated with respect to aragonite (ΩAr<1. In these areas, surface water was low in AT and DIC (<1500 μmol kg−1 relative to seawater and showed low [CO32−]. The low saturation states were probably due to the effect of dilution due from freshwater addition by sea ice melt (CAA and river runoff (MS. High AT and DIC and low pH, corresponded with the lowest [CO32−], ΩAr and ΩCa, observed near Cape Bathurst and along the South Chukchi Peninsula. This was linked to physical upwelling of subsurface water with elevated CO2. Highest surface ΩAr and ΩCa of 3.0 and 4.5, respectively, were found on the Chukchi Sea shelf and in the cold water north of Wrangel Island, which is heavily influenced by high CO2 drawdown and lower DIC from intense biological production. In the western Bering Strait, the cold and saline Anadyr Current carries water that is enriched in AT and DIC from enhanced organic matter remineralization, resulting in

  15. Calcium carbonate saturation in the surface water of the Arctic Ocean: undersaturation in freshwater influenced shelves

    Directory of Open Access Journals (Sweden)

    A. Fransson

    2009-11-01

    Full Text Available In the summer of 2005, we sampled surface water and measured pH and total alkalinity (AT underway aboard IB Oden along the Northwest Passage from Cape Farewell (South Greenland to the Chukchi Sea. We investigated the variability of carbonate system parameters, focusing particularly on carbonate concentration [CO32−] and calcium carbonate saturation states, as related to freshwater addition, biological processes and physical upwelling. Measurements on AT, pH at 15°C, salinity (S and sea surface temperature (SST, were used to calculate total dissolved inorganic carbon (CT, [CO32−] and the saturation of aragonite (ΩAr and calcite (ΩCa in the surface water. The same parameters were measured in the water column of the Bering Strait. Some surface waters in the Canadian Arctic Archipelago (CAA and on the Mackenzie shelf (MS were found to be undersaturated with respect to aragonite (ΩAr<1. In these areas, surface water was low in AT and CT (<1500 μmol kg−1 relative to seawater and showed low [CO32−]. The low saturation states were probably due to the likely the effect of dilution due to freshwater addition by sea ice melt (CAA and river runoff (MS. High AT and CT and low pH, corresponded with the lowest [CO32−], ΩAr and ΩCa, observed near Cape Bathurst and along the South Chukchi Peninsula. This was linked to the physical upwelling of subsurface water with elevated CO2. The highest surface ΩAr and ΩCa of 3.0 and 4.5, respectively, were found on the Chukchi Sea shelf and in the cold water north of Wrangel Island, which is heavily influenced by high CO2 drawdown and lower CT from intense biological production. In the western Bering Strait, the cold and saline Anadyr Current carries water that is enriched in AT and

  16. 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

  17. Response of cloud supersaturation to radiative forcing

    Science.gov (United States)

    Davies, R.

    1985-01-01

    Time-dependent solutions are obtained for droplet temperatures and supersaturation, in a study of the diffusional growth or evaporation of cloud droplets due to net emission or absorption of radiation, taking into account the partitioning of the net radiation budget between the droplets and the ambient air. Radiative perturbations are noted to result in very high rates of change in droplet temperatures. As the droplets evaporate or grow due to radiative effects, the saturation ratio of the ambient air adjusts in keeping with changes in the water vapor density and temperature of the air.

  18. Construction, Analysis, and Data-Driven Augmentation of Supersaturated Designs

    Science.gov (United States)

    2013-09-01

    CONSTRUCTION, ANALYSIS, AND DATA-DRIVEN AUGMENTATION OF SUPERSATURATED DESIGNS DISSERTATION Alex J. Gutman, AFIT-ENC-DS-13-S-02 DEPARTMENT OF THE AIR...DRIVEN AUGMENTATION OF SUPERSATURATED DESIGNS DISSERTATION Presented to the Faculty Graduate School of Engineering and Management Air Force Institute...13-S-02 CONSTRUCTION, ANALYSIS, AND DATA-DRIVEN AUGMENTATION OF SUPERSATURATED DESIGNS Alex J. Gutman, BS, MS Approved: //signed// September 2013

  19. Biocompatibility of Ricinus communis polymer with addition of calcium carbonate compared to titanium. Experimental study in guinea pigs.

    Science.gov (United States)

    Graça, Yorgos Luiz Santos De Salles; Opolski, Ana Cristina; Barboza, Barbara Evelin Gonçalves; Erbano, Bruna Olandoski; Mazzaro, Caroline Cantalejo; Klostermann, Flávia Caroline; Sucharski, Enéas Eduardo; Kubrusly, Luiz Fernando

    2014-01-01

    The aim of the present investigation was to determine whether the difference in inflammatory tissue reaction between the Riccinus communis (castor) polymer with calcium carbonate and the titanium implant is statistically significant. Thirty-two Cavia porcellus were allocated into four groups of eight animals each. We implanted the two types of materials in the retroperitoneal space of all the animals. They were euthanized at 7, 20, 30 and 40 days after surgery, and an histological study of the samples was conducted. All implants showed characteristics of chronic inflammation regardless of the material and timepoint of evaluation. There was no statistically significant difference between Pm+CaCO3 and Ti with regard to the presence of granulation tissue, tissue congestion, histiocytes, lymphocytes, neutrophils, giant cells, and fibrosis (P> 0.05). The castor oil polymer plus calcium carbonate implant was not statistically different from the titanium implant regarding inflammatory tissue reaction.

  20. Biologically formed calcium carbonate : a durable plugging agent for enhanced oil recovery

    Energy Technology Data Exchange (ETDEWEB)

    Nemati, M.; Voordouw, G. [Calgary Univ., AB (Canada)

    2002-06-01

    Waterflooding is a common enhanced oil recovery method in which water is injected into an oil reservoir. The flow is diverted into high permeability zones from which oil has already been recovered during primary production. The increased permeability variation decreases volumetric sweep efficiency of injected water. Cross flow complicates this problem by allowing flow between contrasting layers. This results in a ratio of produced water to oil that is much too high. The use of calcium carbonate (CaCO{sub 3}) and silica may be an effective method for selective plugging of reservoirs. The controlled biological formation of CaCO{sub 3} depends on the decomposition of urea to carbonate and ammonium ions by the catalytic action of urease enzyme. This study shows that biological formation of CaCO{sub 3} could be induced successfully using a bacterium with urease producing activity or urease enzyme. It is shown that the yield of enzymatically produced CaCO{sub 3} is substantially higher than when bacterially produced because the tolerable level of urea for bacteria is lower than the concentration of urea that participates in the enzymatic reaction. Plugging studies in unconsolidated porous media have shown that in situ formation of CaCO{sub 3} may decrease the permeability of porous media. The extent of plugging depends on the enzyme and reactant concentration. The extent of enzymatically produced CaCO{sub 3} increases with higher enzyme concentrations as well as with higher temperature. In situ formation of CaCO{sub 3} could result in a major decrease in permeability. 4 refs., 1 tab., 1 fig.

  1. Dissolution of calcium carbonate: observations and model results in the North Atlantic

    Directory of Open Access Journals (Sweden)

    K. Friis

    2006-10-01

    Full Text Available We investigate the significance of in situ dissolution of calcium carbonate above its saturation horizons. The study relies on observations from the open subpolar North Atlantic [sNA] and on a 3-D biogeochemical model. The sNA is particularly well suited for observation-based detections of in situ, i.e. shallow depth CaCO3 dissolution [SDCCD] as it is a region of high CaCO3 production, deep CaCO3 saturation horizons, and precisely-defined pre-formed alkalinity. Based on the analysis of a comprehensive alkalinity data set we find that SDCCD does not appear to be a significant process in the open sNA. The results from the model support the observational findings and do not indicate a significant need of SDCCD to explain observed patterns of alkalinity in the North Atlantic. Instead our investigation points to the importance of mixing processes for the redistribution of alkalinity from dissolution of CaCO3 from below its saturation horizons. However, mixing has recently been neglected for a number of studies that called for SDCCD in the sNA and on global scale.

  2. The effects of electrolyte on the supercapacitive performance of activated calcium carbide-derived carbon

    Science.gov (United States)

    Wu, Hao; Wang, Xianyou; Jiang, Lanlan; Wu, Chun; Zhao, Qinglan; Liu, Xue; Hu, Ben'an; Yi, Lanhua

    2013-03-01

    Porous calcium carbide-derived carbon (CCDC) has been prepared by one-step route from CaC2 in a freshly prepared chlorine environment at lower temperature, and following activated by ZnCl2 to get activated CCDC. The performances of the supercapacitors based on activated CCDC as electrode active material in aqueous KOH, K2SO4, KCl and KNO3 electrolytes are studied by cyclic voltammetry, constant current charged/discharged, cyclic life and electrochemical impedance spectroscopy. It has been found that the supercapacitor using 6 M KOH as electrolyte shows an energy density of 8.3 Wh kg-1 and a power density of 1992 W kg-1 based on the total weight of the electrode active materials with a voltage range 0 V-1 V. Meanwhile, the specific capacitance of the supercapacitor in 6 M KOH electrolyte is 68 F g-1 at the scan rate of 1 mV s-1 in the voltage range of 0 V-1 V, the charge-transfer resistance is extremely low and the relaxation time is the least of all. The supercapacitor also exhibits a good cycling performance and keeps 95% of initial capacity over 5000 cycles.

  3. One-step bulk preparation of calcium carbonate nanotubes and its application in anticancer drug delivery.

    Science.gov (United States)

    Tang, Jing; Sun, Dong-Mei; Qian, Wen-Yu; Zhu, Rong-Rong; Sun, Xiao-Yu; Wang, Wen-Rui; Li, Kun; Wang, Shi-Long

    2012-06-01

    Bulk fabrication of ordered hollow structural particles (HSPs) with large surface area and high biocompatibility simultaneously is critical for the practical application of HSPs in biosensing and drug delivery. In this article, we describe a smart approach for batch synthesis of calcium carbonate nanotubes (CCNTs) based on supported liquid membrane (SLM) with large surface area, excellent structural stability, prominent biocompatibility, and acid degradability. The products were characterized by transmission electron micrograph, X-ray diffraction, Fourier transform infrared spectra, UV-vis spectroscopy, zeta potential, and particle size distribution. The results showed that the tube-like structure facilitated podophyllotoxin (PPT) diffusion into the cavity of hollow structure, and the drug loading and encapsulation efficiency of CCNTs for PPT are as high as 38.5 and 64.4 wt.%, respectively. In vitro drug release study showed that PPT was released from the CCNTs in a pH-controlled and time-dependent manner. The treatment of HEK 293T and SGC 7901 cells demonstrated that PPT-loaded CCNTs were less toxic to normal cells and more effective in antitumor potency compared with free drugs. In addition, PPT-loaded CCNTs also enhanced the apoptotic process on tumor cells compared with the free drugs. This study not only provides a new kind of biocompatible and pH-sensitive nanomaterial as the feasible drug container and carrier but more importantly establishes a facile approach to synthesize novel hollow structural particles on a large scale based on SLM technology.

  4. Osteoblasts Growth Behaviour on Bio-Based Calcium Carbonate Aragonite Nanocrystal

    Directory of Open Access Journals (Sweden)

    Abdullahi Shafiu Kamba

    2014-01-01

    Full Text Available Calcium carbonate (CaCO3 nanocrystals derived from cockle shells emerge to present a good concert in bone tissue engineering because of their potential to mimic the composition, structure, and properties of native bone. The aim of this study was to evaluate the biological response of CaCO3 nanocrystals on hFOB 1.19 and MC3T3 E-1 osteoblast cells in vitro. Cell viability and proliferation were assessed by MTT and BrdU assays, and LDH was measured to determine the effect of CaCO3 nanocrystals on cell membrane integrity. Cellular morphology was examined by SEM and fluorescence microscopy. The results showed that CaCO3 nanocrystals had no toxic effects to some extent. Cell proliferation, alkaline phosphatase activity, and protein synthesis were enhanced by the nanocrystals when compared to the control. Cellular interactions were improved, as indicated by SEM and fluorescent microscopy. The production of VEGF and TGF-1 was also affected by the CaCO3 nanocrystals. Therefore, bio-based CaCO3 nanocrystals were shown to stimulate osteoblast differentiation and improve the osteointegration process.

  5. Consolidation of archaeological gypsum plaster by bacterial biomineralization of calcium carbonate.

    Science.gov (United States)

    Jroundi, Fadwa; Gonzalez-Muñoz, Maria Teresa; Garcia-Bueno, Ana; Rodriguez-Navarro, Carlos

    2014-09-01

    Gypsum plasterworks and decorative surfaces are easily degraded, especially when exposed to humidity, and thus they require protection and/or consolidation. However, the conservation of historical gypsum-based structural and decorative materials by conventional organic and inorganic consolidants shows limited efficacy. Here, a new method based on the bioconsolidation capacity of carbonatogenic bacteria inhabiting the material was assayed on historical gypsum plasters and compared with conventional consolidation treatments (ethyl silicate; methylacrylate-ethylmethacrylate copolymer and polyvinyl butyral). Conventional products do not reach in-depth consolidation, typically forming a thin impervious surface layer which blocks pores. In contrast, the bacterial treatment produces vaterite (CaCO3) biocement, which does not block pores and produces a good level of consolidation, both at the surface and in-depth, as shown by drilling resistance measurement system analyses. Transmission electron microscopy analyses show that bacterial vaterite cement formed via oriented aggregation of CaCO3 nanoparticles (∼20nm in size), resulting in mesocrystals which incorporate bacterial biopolymers. Such a biocomposite has superior mechanical properties, thus explaining the fact that drilling resistance of bioconsolidated gypsum plasters is within the range of inorganic calcite materials of equivalent porosity, despite the fact that the bacterial vaterite cement accounts for only a 0.02 solid volume fraction. Bacterial bioconsolidation is proposed for the effective consolidation of this type of material. The potential applications of bacterial calcium carbonate consolidation of gypsum biomaterials used as bone graft substitutes are discussed.

  6. 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.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  8. Genesis of amorphous calcium carbonate containing alveolar plates in the ciliate Coleps hirtus (Ciliophora, Prostomatea).

    Science.gov (United States)

    Lemloh, Marie-Louise; Marin, Frédéric; Herbst, Frédéric; Plasseraud, Laurent; Schweikert, Michael; Baier, Johannes; Bill, Joachim; Brümmer, Franz

    2013-02-01

    In the protist world, the ciliate Coleps hirtus (phylum Ciliophora, class Prostomatea) synthesizes a peculiar biomineralized test made of alveolar plates, structures located within alveolar vesicles at the cell cortex. Alveolar plates are arranged by overlapping like an armor and they are thought to protect and/or stiffen the cell. Although their morphology is species-specific and of complex architecture, so far almost nothing is known about their genesis, their structure and their elemental and mineral composition. We investigated the genesis of new alveolar plates after cell division and examined cells and isolated alveolar plates by electron microscopy, energy-dispersive X-ray spectroscopy, FTIR and X-ray diffraction. Our investigations revealed an organic mesh-like structure that guides the formation of new alveolar plates like a template and the role of vesicles transporting inorganic material. We further demonstrated that the inorganic part of the alveolar plates is composed out of amorphous calcium carbonate. For stabilization of the amorphous phase, the alveolar vesicles, the organic fraction and the element phosphorus may play a role.

  9. Distinct Short-Range Order Is Inherent to Small Amorphous Calcium Carbonate Clusters (<2 nm)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Shengtong [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; School of Chemical Engineering, State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, 130 Meilong Road Shanghai 200237 P.R. China; Chevrier, Daniel M. [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Zhang, Peng [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Gebauer, Denis [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; Cölfen, Helmut [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany

    2016-09-09

    Amorphous intermediate phases are vital precursors in the crystallization of many biogenic minerals. While inherent short-range orders have been found in amorphous calcium carbonates (ACCs) relating to different crystalline forms, it has never been clarified experimentally whether such orders already exist in very small clusters less than 2 nm in size. Here, we studied the stability and structure of 10,12-pentacosadiynoic acid (PCDA) protected ACC clusters with a core size of ca. 1.4 nm consisting of only seven CaCO3 units. Ligand concentration and structure are shown to be key factors in stabilizing the ACC clusters. More importantly, even in such small CaCO3 entities, a proto-calcite short-range order can be identified but with a relatively high degree of disorder that arises from the very small size of the CaCO3 core. Our findings support the notion of a structural link between prenucleation clusters, amorphous intermediates, and final crystalline polymorphs, which appears central to the understanding of polymorph selection.

  10. 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.

  11. Retention of silica nanoparticles on calcium carbonate sands immersed in electrolyte solutions

    KAUST Repository

    Li, Yan Vivian

    2014-12-01

    © 2014 Elsevier Inc. Understanding nanoparticle-surface adhesion is necessary to develop inert tracers for subsurface applications. Here we show that nanoparticles with neutral surface charge may make the best subsurface tracers, and that it may be possible to used SiO2 nanoparticle retention to measure the fraction of solid surface that has positive charge. We show that silica nanoparticles dispersed in NaCl electrolyte solutions are increasingly retained in calcium carbonate (calcite) sand-packed columns as the solution ionic strength increases, but are not retained if they are injected in pure water or Na2SO4 electrolyte solutions. The particles retained in the NaCl experiments are released when the column is flushed with pure water or Na2SO4 solution. AFM measurements on calcite immersed in NaCl solutions show the initial repulsion of a silica colloidal probe as the surface is approached is reduced as the solution ionic strength increases, and that at high ionic strengths it disappears entirely and only attraction remains. These AFM measurements and their interpretation with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory shows the calcite surface charge is always negative for Na2SO4 solutions, but changes from negative to positive in a patchy fashion as the ionic strength of the NaCl solution increases. Since mixed-charge (patchy) surfaces may be common in the subsurface, nanoparticles with near-zero charge may make the best tracers.

  12. Polypropylene/calcium carbonate nanocomposites – effects of processing techniques and maleated polypropylene compatibiliser

    Directory of Open Access Journals (Sweden)

    2010-10-01

    Full Text Available The mechanical properties and crystalline characteristics of polypropylene (PP and nano precipitated calcium carbonate (NPCC nanocomposites prepared via melt mixing in an internal mixer and melt extrusion in a twin screw extruder, were compared. The effect of maleic anhydride grafted PP (PP-g-MAH as a compatibiliser was also studied using the internal mixer. At low filler concentration of 5 wt%, impact strength was better for the nanocomposites produced using the internal mixer. At higher filler loading of more than 10 wt%, the extrusion technique was more effective to disperse the nanofillers resulting in better impact properties. The impact results are consistent with the observations made from Scanning Electron Microscope (SEM morphology study. As expected, the flexural modulus of the nanocomposites increased with filler concentration regardless of the techniques utilised. At a same filler loading, there was also no significant difference in the moduli for the two techniques. The tensile strength of the mixed nanocomposites were found to be inferior to the extruded nanocomposites. Introduction of PP-g-MAH improved the impact strength, tensile strength and modulus of the mixed nanocomposites. The improvements may be attributed to better interfacial adhesion, as evident from the SEM micrographs which displayed better dispersion of the NPCC in the presence of the compatibiliser. Though NPCC particles have weak nucleating effect on the crystallization of the PP, addition of PP-g-MAH into the mixed nanocomposites has induced significant crystallization of the PP.

  13. 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.

  14. Skeletal development in Acropora cervicornis: I. Patterns of calcium carbonate accretion in the axial corallite

    Science.gov (United States)

    Gladfeiter, E. H.

    1982-06-01

    Scanning electron microscopy and serial petrographic thin sections were used to investigate skeletal elongation and mineralization in the perforate coral, Acropora cervicornis. The axial corallite extends by the formation of randomly oriented fusiform crystals which are deposited on its distal edge. Aragonitic needle-like crystals grow in random directions from the surface of these fusiform crystals. Only those needle-like crystals growing toward the calicoblastic epithelium (i.e. crystals whose growth axis is perpendicular to the plane of the calicoblastic cell membrane) continue to elongate. Groups of these growing crystals join to form well-defined fasciculi which make up the primary skeletal elements comprising the septotheca. The resulting skeleton is highly porous with all surfaces covered by the continuous calicoblastic epithelium. This cell layer is separated by thin mesoglea from the flagellated gastrodermis which lines the highly ramified coelenteron. Porosity and permeability of the skeleton decrease with distance from the tip. Density correspondingly increases due to the addition of aragonite to the fasciculi whose boundaries become less distinct as channels fill with calcium carbonate.

  15. Effect of L (+) ascorbic acid and monosodium glutamate concentration on the morphology of calcium carbonate

    Science.gov (United States)

    Saraya, Mohamed El-shahte Ismaiel

    2015-11-01

    In this study, monosodium glutamate and ascorbic acid were used as crystal and growth modifiers to control the crystallization of CaCO3. Calcium carbonate prepared by reacting a mixed solution of Na2CO3 with CaCl2 at ambient temperature, (25 °C), constant Ca++/ CO3- - molar ratio and pH with stirring. The polymorph and morphology of the crystals were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results indicate that rhombohedral calcite was only formed in water without organic additives, and both calcite and spherical vaterite with various morphologies were produced in the presence of monosodium glutamate. The content of vaterite increased as the monosodium glutamate increased. In addition, spherical vaterite was obtained in the presence of different concentrations of ascorbic acid. The spherical vaterite posses an aggregate shape composed of nano-particles, ranging from 30 to 50 nm as demonstrated by the SEM and TEM analyses. Therefore, the ascorbic stabilizes vaterite and result in nano-particles compared to monosodium glutamate.

  16. Calcium carbonate crystallization in the presence of modified polysaccharides and linear polymeric additives

    Science.gov (United States)

    Matahwa, H.; Ramiah, V.; Sanderson, R. D.

    2008-10-01

    Crystallization of calcium carbonate was performed in the presence of grafted polysaccharides, polyacrylamide (PAM) and polyacrylic acid (PAA). The grafted polysaccharides gave crystal morphologies that were different from the unmodified polysaccharides but similar to the ones given by homopolymers of the grafted chains. PAM-grafted α-cellulose gave rectangular platelets that aggregated to form 'spherical' crystals on the surface of the fiber, whereas PAA grafted α-cellulose gave spherical crystals on the surface of the fiber. X-ray diffraction (XRD) spectroscopy showed that PAM-grafted α-cellulose, PAM as well as the control (no polymeric additive) gave calcite crystals at both 25 and 80 °C. However, the PAA-grafted α-cellulose and PAA homopolymer gave calcite and vaterite crystals at 25 °C with calcite and aragonite crystals along with traces of vaterite being formed at 80 °C. The fiber surface coverage by these crystals was more on the acrylic- and acrylamide-grafted cellulose than on the ungrafted α-cellulose. The evolution of CaCO 3 polymorphs as well as crystal morphology in PAA-grafted starch was similar to that of PAA-grafted α-cellulose at the two temperatures employed.

  17. 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.

  18. Study on the Functionality of Nano-Precipitated Calcium Carbonate as Filler in Thermoplastics

    Science.gov (United States)

    Basilia, Blessie A.; Panganiban, Marian Elaine G.; Collado, Archilles Allen V. C.; Pesigan, Michael Oliver D.; de Yro, Persia Ada

    This research aims to investigate the functionality of nano-precipitated calcium carbonate (NPCC) as filler in thermoplastic resins based on property enhancement. Three types of thermoplastics were used: polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC). The resins were evaluated by determining the effect of different NPCC loading on the chemical structure, thermal and mechanical properties of thermoplastics. Results showed that there was an interfacial bonding with the NPCC surface and the thermoplastics. Change in absorption peak and area were predominant in the PVC filled composite. There was a decreased in crystallinity of the PE and PP with the addition of filler. Tremendous increase on the tensile and impact strength was exhibited by the NPCC filled PVC composites while PE and PP composites maintained a slight increase in their mechanical properties. Nano-sized filler was proven to improve the mechanical properties of thermoplastics compared with micron-sized filler because nano-sized filler has larger interfacial area between the filler and the polymer matrix.

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

    Energy Technology Data Exchange (ETDEWEB)

    He, Fupo [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China); Zhang, Jing [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Yang, Fanwen; Zhu, Jixiang; Tian, Xiumei [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China); Chen, Xiaoming, E-mail: xmchenw@126.com [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China)

    2015-05-01

    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.

  20. Investigation of scale inhibition mechanisms based on the effect of scale inhibitor on calcium carbonate crystal forms

    Institute of Scientific and Technical Information of China (English)

    ZHANG GuiCai; GE JiJiang; SUN MingQin; PAN BinLin; MAO Tao; SONG ZhaoZheng

    2007-01-01

    To probe the scale inhibition mechanisms, calcium carbonate scale occurring before and after the addition of scale inhibitors was collected. The results from scale SEM confirm that, without scale inhibitor, calcium carbonate scale shows rhombohedron and hexagon, which are the characteristic feathers of calcite. After addition of inhibitors, morphology of scale is changed, and the more efficient the scale inhibitor is, the more greatly the morphology is modified. To elucidate the scale constitute, they were further analyzed by FT-IR, XRD. Besides calcite, vaterite and aragonite occur in calcium carbonate scale after addition of inhibitors, and the higher scale inhibition efficiency is, the more vaterite presents in scale. It can be concluded that the alteration of morphology is ascribed to the change of crystal form. There are three stages in the crystallizing process including occurrence and disappearing of unstable phase, occurrence and disappearing of metastable phase, development of stable phase. Without scale inhibitors, metastable phases usually transform into stable phase, thus the main constitute of formed scale is calcite. When scale inhibitors are added, both formation and transformation of metastable phases are inhibited, which results in the occurrence of aragonite and vaterite. From the fact that more vaterite presents in scale with a more efficient scale inhibitor added, we can see that the function of scale inhibitor is realized mainly by controlling the crystallizing process at the second stage.

  1. Investigation of scale inhibition mechanisms based on the effect of scale inhibitor on calcium carbonate crystal forms

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To probe the scale inhibition mechanisms,calcium carbonate scale occurring before and after the ad- dition of scale inhibitors was collected.The results from scale SEM confirm that,without scale inhibitor, calcium carbonate scale shows rhombohedron and hexagon,which are the characteristic feathers of calcite.After addition of inhibitors,morphology of scale is changed,and the more efficient the scale inhibitor is,the more greatly the morphology is modified.To elucidate the scale constitute,they were further analyzed by FT-IR,XRD.Besides calcite,vaterite and aragonite occur in calcium carbonate scale after addition of inhibitors,and the higher scale inhibition efficiency is,the more vaterite presents in scale.It can be concluded that the alteration of morphology is ascribed to the change of crystal form. There are three stages in the crystallizing process including occurrence and disappearing of unstable phase,occurrence and disappearing of metastable phase,development of stable phase.Without scale inhibitors,metastable phases usually transform into stable phase,thus the main constitute of formed scale is calcite.When scale inhibitors are added,both formation and transformation of metastable phases are inhibited,which results in the occurrence of aragonite and vaterite.From the fact that more vaterite presents in scale with a more efficient scale inhibitor added,we can see that the function of scale inhibitor is realized mainly by controlling the crystallizing process at the second stage.

  2. Spatial distribution of calcite and amorphous calcium carbonate in the cuticle of the terrestrial crustaceans Porcellio scaber and Armadillidium vulgare.

    Science.gov (United States)

    Hild, Sabine; Marti, Othmar; Ziegler, Andreas

    2008-07-01

    The crustacean cuticle is an interesting model to study the properties of mineralized bio-composites. The cuticle consists of an organic matrix composed of chitin-protein fibres associated with various amounts of crystalline and amorphous calcium carbonate. It is thought that in isopods the relative amounts of these mineral polymorphs depend on its function and the habitat of the animal. In addition to the composition, the distribution of the various components should affect the properties of the cuticle. However, the spatial distribution of calcium carbonate polymorphs within the crustacean cuticle is unknown. Therefore, we analyzed the mineralized cuticles of the terrestrial isopods Armadillidium vulgare and Porcellio scaber using scanning electron-microscopy, electron probe microanalysis and confocal mu-Raman spectroscopic imaging. We show for the first time that the mineral phases are arranged in distinct layers. Calcite is restricted to the outer layer of the cuticle that corresponds to the exocuticle. Amorphous calcium carbonate is located within the endocuticle that lies below the exocuticle. Within both layers mineral is arranged in rows of granules with diameters of about 20 nm. The results suggest functional implications of mineral distribution that accord to the moulting and escape behaviour of the animals.

  3. Energies of the adsorption of functional groups to calcium carbonate polymorphs: the importance of -OH and -COOH groups.

    Science.gov (United States)

    Okhrimenko, D V; Nissenbaum, J; Andersson, M P; Olsson, M H M; Stipp, S L S

    2013-09-01

    The adsorption behavior of calcium carbonate is an important factor in many processes in nature, industry, and biological systems. We determined and compared the adsorption energies for a series of small molecules of different sizes and polarities (i.e., water, several alcohols, and acetic acid) on three synthetic CaCO3 polymorphs (calcite, aragonite, and vaterite). We measured isosteric heats of adsorption from vapor adsorption isotherms for 273 < T < 293 K, and we used XRD and SEM to confirm that samples did not change phase during the experiments. Density functional calculations and molecular dynamics simulations complemented the experimental results and aided interpretation. Alcohols with molecular mass greater than that of methanol bind more strongly to the calcium carbonate polymorphs than water and acetic acid. The adsorption energies for the alcohols are typical of chemisorption and indicate alcohol displacement of water from calcium carbonate surfaces. This explains why organisms favor biomolecules that contain alcohol functional groups (-OH) to control which polymorph they use, the crystal face and orientation, and the particle shape and size in biomineralization processes. This new insight is also very useful in understanding organic molecule adsorption mechanisms in soils, sediments, and rocks, which is important for predicting the behavior of mineral-fluid interactions when the challenge is to remediate contaminated groundwater aquifers or to produce oil and gas from reservoirs.

  4. Pore-scale network modeling of microbially induced calcium carbonate precipitation: Insight into scale dependence of biogeochemical reaction rates

    Science.gov (United States)

    Qin, Chao-Zhong; Hassanizadeh, S. Majid; Ebigbo, Anozie

    2016-11-01

    The engineering of microbially induced calcium carbonate precipitation (MICP) has attracted much attention in a number of applications, such as sealing of CO2 leakage pathways, soil stabilization, and subsurface remediation of radionuclides and toxic metals. The goal of this work is to gain insight into pore-scale processes of MICP and scale dependence of biogeochemical reaction rates. This will help us develop efficient field-scale MICP models. In this work, we have developed a comprehensive pore-network model for MICP, with geochemical speciation calculated by the open-source PHREEQC module. A numerical pseudo-3-D micromodel as the computational domain was generated by a novel pore-network generation method. We modeled a three-stage process in the engineering of MICP including the growth of biofilm, the injection of calcium-rich medium, and the precipitation of calcium carbonate. A number of test cases were conducted to illustrate how calcite precipitation was influenced by different operating conditions. In addition, we studied the possibility of reducing the computational effort by simplifying geochemical calculations. Finally, the effect of mass transfer limitation of possible carbonate ions in a pore element on calcite precipitation was explored.

  5. Can Solution Supersaturation Affect Protein Crystal Quality?

    Science.gov (United States)

    Gorti, Sridhar

    2013-01-01

    The formation of large protein crystals of "high quality" is considered a characteristic manifestation of microgravity. The physical processes that predict the formation of large, high quality protein crystals in the microgravity environment of space are considered rooted in the existence of a "depletion zone" in the vicinity of crystal. Namely, it is considered reasonable that crystal quality suffers in earth-grown crystals as a result of the incorporation of large aggregates, micro-crystals and/or large molecular weight "impurities", processes which are aided by density driven convective flow or mixing at the crystal-liquid interface. Sedimentation and density driven convection produce unfavorable solution conditions in the vicinity of the crystal surface, which promotes rapid crystal growth to the detriment of crystal size and quality. In this effort, we shall further present the hypothesis that the solution supersaturatoin at the crystal surface determines the growth mechanism, or mode, by which protein crystals grow. It is further hypothesized that protein crystal quality is affected by the mechanism or mode of crystal growth. Hence the formation of a depletion zone in microgravity environment is beneficial due to inhibition of impurity incorporatoin as well as preventing a kinetic roughening transition. It should be noted that for many proteins the magnitude of neither protein crystal growth rates nor solution supersaturation are predictors of a kinetic roughening transition. That is, the kinetic roughening transition supersaturation must be dtermined for each individual protein.

  6. Clinical evidence for the superior efficacy of a dentifrice containing 8.0% arginine and calcium carbonate in providing instant and lasting relief of dentin hypersensitivity.

    Science.gov (United States)

    Cummins, D

    2011-01-01

    This paper briefly discusses recent scientific and clinical research validating the effectiveness of a toothpaste containing 8.0% arginine and calcium carbonate, known as Pro-Argin technology, including clinical evidence for the superior efficacy of this toothpaste versus a potassium-based desensitizing toothpaste. It also introduces new clinical data which prove that a toothpaste containing 8.0% arginine and calcium carbonate delivers superior instant and lasting relief of dentin hypersensitivity compared to a toothpaste containing 8% strontium acetate.

  7. Lab-Scale Study of the Calcium Carbonate Dissolution and Deposition by Marine Cyanobacterium Phormidium subcapitatum

    Science.gov (United States)

    Karakis, S. G.; Dragoeva, E. G.; Lavrenyuk, T. I.; Rogochiy, A.; Gerasimenko, L. M.; McKay, D. S.; Brown, I. I.

    2006-01-01

    Suggestions that calcification in marine organisms changes in response to global variations in seawater chemistry continue to be advanced (Wilkinson, 1979; Degens et al. 1985; Kazmierczak et al. 1986; R. Riding 1992). However, the effect of [Na+] on calcification in marine cyanobacteria has not been discussed in detail although [Na+] fluctuations reflect both temperature and sea-level fluctuations. The goal of these lab-scale studies therefore was to study the effect of environmental pH and [Na+] on CaCO3 deposition and dissolution by marine cyanobacterium Phormidium subcapitatum. Marine cyanobacterium P. subcapitatum has been cultivated in ASN-III medium. [Ca2+] fluctuations were monitored with Ca(2+) probe. Na(+) concentrations were determined by the initial solution chemistry. It was found that the balance between CaCO3 dissolution and precipitation induced by P. subcapitatum grown in neutral ASN III medium is very close to zero. No CaCO3 precipitation induced by cyanobacterial growth occurred. Growth of P. subcapitatum in alkaline ASN III medium, however, was accompanied by significant oscillations in free Ca(2+) concentration within a Na(+) concentration range of 50-400 mM. Calcium carbonate precipitation occurred during the log phase of P. subcapitatum growth while carbonate dissolution was typical for the stationary phase of P. subcapitatum growth. The highest CaCO3 deposition was observed in the range of Na(+) concentrations between 200-400 mM. Alkaline pH also induced the clamping of P. subcapitatum filaments, which appeared to have a strong affinity to envelop particles of chemically deposited CaCO3 followed by enlargement of those particles size. EDS analysis revealed the presence of Mg-rich carbonate (or magnesium calcite) in the solution containing 10-100 mM Na(+); calcite in the solution containing 200 mM Na(+); and aragonite in the solution containing with 400 mM Na(+). Typical present-day seawater contains xxmM Na(+). Early (Archean) seawater was

  8. Conversion of calcium sulphide to calcium carbonate during the process of recovery of elemental sulphur from gypsum waste

    CSIR Research Space (South Africa)

    De Beer, Morris

    2014-11-01

    Full Text Available of hydrogen sulphide (H(sub2)S) and CaCO(sub3). H(sub2)S can subsequently be converted to elemental sulphur via the commercially available chemical catalytic Claus process. This study investigated the carbonation of CaS by examining both the solution chemistry...

  9. Remineralization efficacy of a toothpaste containing 8% arginine and calcium carbonate on enamel surface.

    Science.gov (United States)

    Huang, Yajing; Duan, Yanxia; Qian, Yingzi; Huang, Rui; Yang, Zhengyan; Li, Yueheng; Zhou, Zhi

    2013-10-01

    To investigate the remineralization efficacy of different types of toothpastes on initial enamel lesions in vitro. Artificial initial lesions were created on 150 enamel discs from freshly extracted bovine incisors. These enamel discs were divided into five groups. The test treatment consisted of undiluted Colgate Sensitive Pro-Relief Toothpaste containing 8.0% arginine, calcium carbonate and 1,450 ppm fluoride that was applied on the enamel surface under a pH-cycling including 4 x 3-minute application daily for 12 days and soaked in remineralizing solution during the untreated periods. The two other test products were commercial products: Crest Cavity Protection Toothpaste, containing 0.11% fluoride and GC Tooth Mousse, a professional remineralizing treatment paste (the active ingredients: casein phosphopeptide - amorphous calcium phosphate, fluoride). NaF solution (0.14% fluoride) was used as the positive control, while double distilled water (ddH2O) was used as the negative control. The remineralization of enamel discs was evaluated using Knoop hardness test, confocal laser scanning microscopy (CLSM) and polarized light microscopy (PLM), and the caries lesion depth was quantified using an image analyzer. The data were analyzed by ANOVA. All test products showed a recovery of the Knoop Hardness Number (KHN) after remineralization cycling treatment. The recovery of enamel KHN for Colgate Sensitive Pro-Relief, GC Mousse, Crest toothpasteand NaF groups were 44.53 +/- 6.72%, 35.00 +/- 7.83%, 24.56 +/- 5.95% and 42.51 +/- 6.74% respectively, while the recovery of negative control group was 18.99 +/- 4.98%. PLM results indicated the lesion depth recovery of 49.63 +/- 8.06%, 35.08 +/- 2.19%, 22.60 +/- 7.30% and 53.20 +/- 1.48% respectively, which were also significantly greater than that of the negative group (20.51 +/- 4.80%). CLSM analysis showed a reduction of average area, and total and average dye fluorescence of the lesions after treatment. The Colgate Sensitive

  10. Amelogenin–chitosan matrix for human enamel regrowth: effects of viscosity and supersaturation degree

    Science.gov (United States)

    Ruan, Qichao; Siddiqah, Nadia; Li, Xiaochen; Nutt, Steven; Moradian-Oldak, Janet

    2015-01-01

    We recently reported an amelogenin-chitosan (CS-AMEL) hydrogel as a promising biomimetic material for future in situ human enamel regrowth. To further optimize the necessary conditions for clinical applicability of CS-AMEL hydrogel, herein we studied the effects of viscosity and supersaturation degree on the size and orientation of synthetic crystals by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Raising the hydrogel viscosity by increasing chitosan concentration from 1% to 2% (w/v) improved the orientation of the crystals, while a higher supersaturation (σ(HAp) >10.06, [Ca2+] >5 mM) resulted in the formation of random crystals with larger sizes and irregular structures. We conclude that optimal conditions to produce organized enamel-like crystals in a CS-AMEL hydrogel are: 2% (w/v) chitosan, 2.5 mM calcium, and 1.5 mM phosphate (degree of supersaturation = 8.23) and 200 μg/ml of amelogenin. PMID:25158201

  11. Performance of functionally graded implants of polylactides and calcium phosphate/calcium carbonate in an ovine model for computer assisted craniectomy and cranioplasty.

    Science.gov (United States)

    Eufinger, Harald; Rasche, Christian; Lehmbrock, Jutta; Wehmöller, Michael; Weihe, Stephan; Schmitz, Inge; Schiller, Carsten; Epple, Matthias

    2007-01-01

    Biodegradable functionally graded skull implants on the basis of polylactides and calcium phosphate/calcium carbonate were prepared in an individual mould using a combination of different processing techniques. A geometrically corresponding resection template was designed to enable a craniectomy and cranioplasty with the prepared implant in the same operation. After various preliminary experiments concerning degradation kinetics, pH evolution during degradation, micromorphology, biocompatibility tests in human osteoblast cell cultures and surgery of cadaver heads, a new large-animal model was developed for long-term in vivo studies. In eight 12-months-old sheep, the surgical templates were used to create 4.5 x 5 cm(2) calvarial defects which were then filled with the corresponding degradable implants in the same operation. The animals were sacrificed after 2, 9, 12 and 18 months, and the implants and the surrounding tissues were analysed by computer tomography (CT), macroscopic examination and microscopy. The new animal model proved to be reliable and very suitable for large individual craniectomies and cranioplasties. The formation of new bone from the dural layer of the meninges corresponded well to the degradation of the porous inner layer of the implants whereas the skull contour was stabilised by the compact outer layer over the follow-up period.

  12. Preparation of calcium alginate microgel beads in an electrodispersion reactor using an internal source of calcium carbonate nanoparticles.

    Science.gov (United States)

    Zhao, Yinyan; Carvajal, M Teresa; Won, You-Yeon; Harris, Michael T

    2007-12-04

    An electrodispersion reactor has been used to prepare calcium alginate (Ca-alginate) microgel beads in this study. In the electrodispersion reactor, pulsed electric fields are utilized to atomize aqueous mixtures of sodium alginate and CaCO3 nanoparticles (dispersed phase) from a nozzle into an immiscible, insulating second liquid (continuous phase) containing a soluble organic acid. This technique combines the features of the electrohydrodynamic force driven emulsion processes and externally triggered gelations in microreactors (the droplets) ultimately to yield soft gel beads. The average particle size of the Ca-alginate gels generated by this method changed from 412 +/- 90 to 10 +/- 3 microm as the applied peak voltage was increased. A diagram depicting structural information for the Ca-alginate was constructed as a function of the concentrations of sodium alginate and CaCO3 nanoparticles. From this diagram, a critical concentration of sodium alginate required for sol-gel transformation was observed. The characteristic highly porous structure of Ca-alginate particles made by this technique appears suitable for microencapsulation applications. Finally, time scale analysis was performed for the electrodispersion processes that include reactions in the microreactor droplets to provide guidelines for the future employment of this technique. This electrodispersion reactor can be used potentially in the formation of many reaction-based microencapsulation systems.

  13. Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods

    Science.gov (United States)

    Cao, Zhi; Daly, Michael; Clémence, Lopez; Geever, Luke M.; Major, Ian; Higginbotham, Clement L.; Devine, Declan M.

    2016-08-01

    Calcium carbonate (CaCO3) is often treated with stearic acid (SA) to decrease its polarity. However, the method of application of the SA treatments has a strong influence on CaCO3 thermoplastic composite's interfacial structure and distribution. Several of papers describe the promising effects of SA surface treatment, but few compare the treatment process and its effect on the properties of the final thermoplastic composite. In the current study, we assessed a new SA treatment method, namely, complex treatment for polymer composite fabrication with HDPE. Subsequently, a comparative study was performed between the "complex" process and the other existing methods. The composites were assessed using different experiments included scanning electron microscopy (SEM), void content, density, wettability, differential scanning calorimetry (DSC), and tensile tests. It was observed that the "complex" surface treatment yielded composites with a significantly lower voids content and higher density compared to other surface treatments. This indicates that after the "complex" treatment process, the CaCO3 particles and HDPE matrix are more tightly packed than other methods. DSC and wettability results suggest that the "wet" and "complex" treated CaCO3 composites had a significantly higher heat of fusion and moisture resistance compared to the "dry" treated CaCO3 composites. Furthermore, "wet" and "complex" treated CaCO3 composites have a significantly higher tensile strength than the composites containing untreated and "dry" treated CaCO3. This is mainly because the "wet" and "complex" treatment processes have increased adsorption density of stearate, which enhances the interfacial interaction between matrix and filler. These results confirm that the chemical adsorption of the surfactant ions at the solid-liquid interface is higher than at other interface. From this study, it was concluded that the utilization of the "complex" method minimised the negative effects of void

  14. Hybrid calcium carbonate/polymer microparticles containing silver nanoparticles as antibacterial agents

    Energy Technology Data Exchange (ETDEWEB)

    Dlugosz, Maciej; Bulwan, Maria; Kania, Gabriela; Nowakowska, Maria; Zapotoczny, Szczepan, E-mail: zapotocz@chemia.uj.edu.pl [Jagiellonian University, Faculty of Chemistry (Poland)

    2012-12-15

    We report here on synthesis and characterization of novel hybrid material consisting of silver nanoparticles (nAgs) embedded in calcium carbonate microparticles ({mu}-CaCO{sub 3}) serving as carriers for sustained release. nAgs are commonly used as antimicrobial agents in many commercial products (textiles, cosmetics, and drugs). Although they are considered to be safe, their interactions with human organisms are still not fully understood; therefore it is important to apply them with caution and limit their presence in the environment. The synthesis of the new material was based on the co-precipitation of CaCO{sub 3} and nAg in the presence of poly(sodium 4-styrenesulfonate). Such designed system enables sustained release of nAg to the environment. This hybrid colloidal material (nAg/{mu}-CaCO{sub 3}) was characterized by microscopic and spectroscopic methods. The release of nAg from {mu}-CaCO{sub 3} microparticles was followed in water at various pH values. Microbiological tests confirmed the effectiveness of these microparticles as an antibacterial agent. Importantly, the material can be stored as a dry powder and subsequently re-suspended in water without the risk of losing its antimicrobial activity. nAg/{mu}-CaCO{sub 3} was applied here to insure bacteriostatic properties of down feathers that may significantly prolong their lifetime in typical applications. Such microparticles may be also used as, e.g., components of coatings and paints protecting various surfaces against microorganism colonization.

  15. Sustained release of small molecules from carbon nanotube-reinforced monetite calcium phosphate cement.

    Science.gov (United States)

    Lin, Boren; Zhou, Huan; Leaman, Douglas W; Goel, Vijay K; Agarwal, Anand K; Bhaduri, Sarit B

    2014-10-01

    The interest in developing calcium phosphate cement (CPC) as a drug delivery system has risen because of its capability to achieve local and controlled treatment to the site of the bone disease. The purpose of this study was to investigate the release pattern of drug-carrying carboxylic acid-functionalized multi-walled carbon nanotube (MWCNT)-reinforced monetite (DCPA, CaHPO4)-based CPC. Z-Leu-Leu-Leu-al (MG132), a small peptide molecule inhibiting NF-κB-mediated osteoclastic resorption, was used as a model drug. MG132 was added into the cement during setting and released into the medium used to culture indicator cells. Significant cell death was observed in osteoblast MC3T3-E1 cells cultured in the medium incubated with MG132-loaded CPC; however, with the presence of MWCNTs in the cement, the toxic effect was not detectable. NF-κB activation was quantified using a NF-κB promoter-driving luciferase reporter in human embryonic kidney 293 cells. The medium collected after incubation with drug-incorporated CPC with or without MWCNT inhibited TNFα-induced NF-κB activation indicating that the effective amount of MG132 was released. CPC/drug complex showed a rapid release within 24h whereas incorporation of MWCNTs attenuated this burst release effect. In addition, suppression of TNFα-induced osteoclast differentiation in RAW 264.7 cell culture also confirmed the sustained release of MWCNT/CPC/drug. Our data demonstrated the drug delivery capability of this cement composite, which can potentially be used to carry therapeutic molecules to improve bone regeneration in conjunction with its fracture stabilizing function. Furthermore, it suggested a novel approach to lessen the burst release effect of the CPC-based drug delivery system by incorporating functionalized MWCNTs.

  16. Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.

    Directory of Open Access Journals (Sweden)

    Bernardo Vargas-Ángel

    Full Text Available This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2 yr(-1 of early successional recruitment communities on Calcification Accretion Unit (CAU plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons

  17. Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.

    Science.gov (United States)

    Vargas-Ángel, Bernardo; Richards, Cristi L; Vroom, Peter S; Price, Nichole N; Schils, Tom; Young, Charles W; Smith, Jennifer; Johnson, Maggie D; Brainard, Russell E

    2015-01-01

    This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2) yr(-1)) of early successional recruitment communities on Calcification Accretion Unit (CAU) plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years) of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA) percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons makes CCA

  18. CCN-supersaturation spectra slopes (k)

    Science.gov (United States)

    Jiusto, J. E.; Lala, G. G.

    1981-01-01

    Theoretically the slope k of a CCN-supesaturation spectrum should equal two thirds of the slope of the total (soluble) aerosol size distribution. Workshop results tended to verify this relation. The k values are markedly different depending on whether one is measuring ambient CCN concentrations at supersaturations S above or below approximately 0.1-0.2%. The larger k values for S approximately 0.1% is consistent with the greater decrease in large particle concentration with increasing size. It is concluded that over the S range of 0.02% to 2%, two power fits (and k values) may sometimes suffice for a reasonable approximation of the CCN distribution. At other times, and with laboratory generated aeosols, such an approach is inadequate and requires refinement.

  19. Thermodynamics of supersaturated steam: Molecular simulation results

    Science.gov (United States)

    Moučka, Filip; Nezbeda, Ivo

    2016-12-01

    Supersaturated steam modeled by the Gaussian charge polarizable model [P. Paricaud, M. Předota, and A. A. Chialvo, J. Chem. Phys. 122, 244511 (2005)] and BK3 model [P. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)] has been simulated at conditions occurring in steam turbines using the multiple-particle-move Monte Carlo for both the homogeneous phase and also implemented for the Gibbs ensemble Monte Carlo molecular simulation methods. Because of these thermodynamic conditions, a specific simulation algorithm has been developed to bypass common simulation problems resulting from very low densities of steam and cluster formation therein. In addition to pressure-temperature-density and orthobaric data, the distribution of clusters has also been evaluated. The obtained extensive data of high precision should serve as a basis for development of reliable molecular-based equations for properties of metastable steam.

  20. Impact of High Calcium Intake from Calcium Carbonate or Dairy on Cardiovascular Function, Coronary Artery Calcification and Coronary Artery Disease Burden in Ossabaw Miniature Swine

    OpenAIRE

    Phillips, Alyssa K.

    2013-01-01

    Recent secondary analyses have associated supplemental calcium use with increased risk for myocardial infarction and cardiovascular-related death in healthy, older adults. Subsequent concern over the safety of calcium supplements has spurred a calcium controversy, because calcium is a shortfall essential nutrient that is critical for bone health and a mainstay of osteoporosis prevention and treatment. The proposed mechanism by which calcium intake may detriment cardiovascular health is throug...

  1. Modification of asphaltic concrete with a mineral polymeric additive based on butadiene-styrene rubber and chemically precipitated calcium carbonate

    Directory of Open Access Journals (Sweden)

    S. I. Niftaliev

    2016-01-01

    Full Text Available Modification of asphaltic concrete with a mineral polymeric additive based on butadiene – styrene rubber and chemically precipitated calcium carbonate. This paper presents the results of the study of physical – mechanical and service properties of the asphaltic concrete modified with the mineral polymeric composition. Calcium carbonate is used both as a filler and a coagulant. The chalk was preliminarily ground and hydrophobizated by stearic acid. These operations contribute to even distribution of the filler and interfere with lump coagulation. As a result of the experiments, it was found that the best results were obtained by combining the operations of dispersion and hydrophobization. The optimal amount of stearic acid providing the finest grinding in a ball mill is a content from 3 to 5% by weight. The optimal grinding time of the filler was found (4–6 hours. With increasing dispersion time the particles form agglomerates. Filling the butadiene styrene latex with the hydrophobic fine-grained calcium carbonate was carried out in the laboratory mixer. As a result of the experimental works, it was found that the best distribution of the filler takes place with ratio of rubber: chalk – 100:400. The resulting modifier was subjected to the thermal analysis on the derivatograph to determine its application temperature interval. A marked reduction in weight of the mineral polymeric modifier begins at 350 °C. Thus, high temperature of the modifier destruction allows to use it at the temperature of the technological process of asphaltic concrete preparation (up to 170 °C. It was found that an increase in the amount of the carbonate filler in the rubber SKS 30АRК significantly increases its thermal resistance and connection of the polymer with the chalk in the composition.

  2. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    Science.gov (United States)

    Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

    2012-04-01

    Processes in the carbonate system of surface waters are in particular sensitive to variations of boundary conditions as, for instance, the partial pressure of carbon dioxide in the atmosphere and the aqueous solution. Examples range from streams, rivers, to coastal marine waters. The flux of carbon dioxide from continental flowing waters was recently included into calculations of the global carbon budget (Butman & Raymond, 2011, Nature Geo.). These solutions, are often supersaturated in carbon dioxide with respect to the atmosphere. The degassing of carbon dioxide is associated with a kinetically controlled fractionation of the stable carbon isotopes, which has to be considered in balancing water-air carbon dioxide fluxes. The degassing process additionally leads to the super-saturation of the aqueous solution with respect to calcium carbonate. Stable isotope fractionation is of particular value to identify and quantify processes at the water-gas phase interface and link these non-equilibrium processes to the formation mechanisms of calcite and the hydrodynamics of surface waters. Experiments were carried out with or without inert N2 gas flow to degas carbon dioxide from initially supersaturated solutions. Natural solutions used are from different stations of the Elbe estuary, the Jade Bay, the backbarrier tidal area of Spiekeroog Island, carbonate springs of Rügen Island, and the Baltic Sea coastline. Results are compared experiments using bottled mineral waters. By following the (physico) chemical changes in the solutions (pH, TA, Ca PHREEQC modeling) it was found, that two evolutionary stages can be differentiated. Reaction progress led to the preferential liberation of carbon dioxide containing the light carbon isotope, following a Rayleigh-type process. After an induction period, where only degassing of carbon dioxide took place, a second stage was observed where calcite began to form from the highly supersaturated solutions. In this stage the carbonate

  3. Optimization of Calcium Carbonate Precipitation for Carbonate Mineralization Bacteria%碳酸盐矿化菌诱导碳酸钙沉淀条件的优化

    Institute of Scientific and Technical Information of China (English)

    竹文坤; 罗学刚

    2012-01-01

    The effects of temperature, pH value, precipitation time, reaccant concentration, the crystal formation additive on the yield of calcium carbonate precipitation induced by carbonate mineralization bacteria were investigated through single-factor and orthogonal tests. The morphology, thermal property, elements and structure of the calcium carbonate were characterized by scanning electron microscopic (SEM) and flouner transform infrared spectroscopy (IR), energy dispersive spectroscopy (EDS), thermal analyzer (TG) and powder X-ray diffraction (XRD). The results showed that the optimum conditions of calcium carbonate precipitation induced by carbonate mineralization bacteria were temperature of 40 ℃, pH value of 8, time of 3 d, Ca2+ concentration of 1.5 mol/L and Mg2+ concentration of 0.05 mol/L. Precipitation sediment contain mainly C, O, Ca elements and a little of organic matter, its crystal structure, morphology and packing density were changed by different external conditions, in order to improve the yield of calcium carbonate precipitation, and to provide bases for the efficiency of microbial remediation technology.%通过单因素及正交试验研究了温度、pH值、沉淀时间、反应物浓度和成核剂5个因素对微生物诱导CaCO3沉淀量的影响,以期提高微生物沉积碳酸钙的产率,为微生物修复技术的时效性提供参考.采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、热分析仪(TG)、能谱分析(EDS)对CaCO3样品形貌、结构、热性质、元素等进行表征分析.结果表明,沉淀物质主要含有C、O、Ca元素和少量有机质,其晶型、形貌和堆积密度随外界条件改变而不同.微生物诱导CaCO3沉淀的最佳外界条件是:pH值为8,Mg2+浓度0.05 mol/L,温度40℃,沉淀时间3d,Ca2+浓度1.5 mol/L.

  4. Corrosion inhibition of carbon steel in the near neutral media by blends of tannin and calcium gluconate

    Energy Technology Data Exchange (ETDEWEB)

    Lahodny-Sarc, O.; Kapor, F. [Mining, Geology and Petrol. Eng. Dept., Univ. of Zagreb (Croatia)

    2002-04-01

    The efficiency of tannin/calcium gluconate blends, as corrosion inhibitors for carbon steel in near neutral water media, have been studied. Synergistic behaviour of two components blend of different concentrations has been demonstrated in solutions prepared with distilled and a tap water. The anodic character of the inhibitor was recognised by the shift of corrosion potential to more positive values and a decrease of the passivation current on potentiodynamic polarisation curves. The cathodic inhibition was also recognised by slowing down the cathodic current of the polarisation run. Soluble iron tannate chelate has been observed as a dark blue flux flowing down from the metal surface into solution of tannin in the tap water, resulting in a corrosion process. Tannin decreases the pH of tap water. Calcium gluconate added in tannin solutions increases the pH maintaining it in the near neutral region enabling the precipitation of a low soluble protective iron tannate and metal gluconate. (orig.)

  5. 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.

  6. 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

  7. Determination of calcium carbonate and sodium carbonate melting curves up to Earth's transition zone pressures with implications for the deep carbon cycle

    Science.gov (United States)

    Li, Zeyu; Li, Jie; Lange, Rebecca; Liu, Jiachao; Militzer, Burkhard

    2017-01-01

    Melting of carbonated eclogite or peridotite in the mantle influences the Earth's deep volatile cycles and bears on the long-term evolution of the atmosphere. Existing data on the melting curves of calcium carbonate (CaCO3) and sodium carbonate (Na2CO3) are limited to 7 GPa and therefore do not allow a full understanding of carbon storage and cycling in deep Earth. We determined the melting curves of CaCO3 and Na2CO3 to the pressures of Earth's transition zone using a multi-anvil apparatus. Melting was detected in situ by monitoring a steep and large increase in ionic conductivity, or inferred from sunken platinum markers in recovered samples. The melting point of CaCO3 rises from 1870 K at 3 GPa to ∼2000 K at 6 GPa and then stays within 50 K of 2000 K between 6 and 21 GPa. In contrast, the melting point of Na2CO3 increases continuously from ∼1123 K at 3 GPa to ∼1950 K at 17 GPa. A pre-melting peak in the alternating current through solid CaCO3 is attributed to the transition from aragonite to calcite V. Accordingly the calcite V-aragonite-liquid invariant point is placed at 13 ± 1 GPa and 1970 ± 40 K, with the Clapeyron slope of the calcite V to aragonite transition constrained at ∼70 K/GPa. The experiments on CaCO3 suggest a slight decrease in the melting temperature from 8 to 13 GPa, followed by a slight increase from 14 to 21 GPa. The negative melting slope is consistent with the prediction from our ab initio simulations that the liquid may be more compressible and become denser than calcite V at sufficiently high pressure. The positive melting slope at higher pressures is supported by the ab initio prediction that aragonite is denser than the liquid at pressures up to 30 GPa. At transition zone pressures the melting points of CaCO3 are comparable to that of Na2CO3 but nearly 400 K and 500 K lower than that of MgCO3. The fusible nature of compressed CaCO3 may be partially responsible for the majority of carbonatitic melts found on Earth's surface

  8. 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.

  9. The adsorption and inhibition effect of calcium lignosulfonate on Q235 carbon steel in simulated concrete pore solution

    Science.gov (United States)

    Wang, Yishan; Zuo, Yu; Zhao, Xuhui; Zha, Shanshan

    2016-08-01

    The corrosion inhibition of calcium lignosulfonate (CLS) for Q235 carbon steel in saturated Ca(OH)2 + 0.1 mol/L NaCl solution was studied by means of weight loss, polarization, fluorescence microscopy (FM), scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), microscopic infrared spectral imaging (M-IR) and X-ray photoelectron spectroscopy (XPS). For the steel in simulated concrete pore solution (pH 12.6), an increase of Eb value and a decrease of icorr value occurred with different concentrations of CLS. The optimal content of CLS was 0.001 mol/L at which the inhibition rate was 98.86% and the Eb value increased to 719 mV after 10 h of immersion. In mortar solution and in reinforced concrete environment, CLS also showed good inhibition for steel. The preferential adsorption of CLS around pits was detected by M-IR. The result illustrates that at the early stage the adsorption of CLS was heterogeneous and CLS may have a competitive adsorption with chloride ions at the active sites, which would be beneficial for decreasing the susceptibility of pitting corrosion. After the pre-filming time, an intact adsorption CLS film formed on carbon steel surface. The adsorption between CLS and calcium presented as Casbnd Osbnd S bonds. The adsorption of CLS on carbon steel surface occurred probably by both physisorption and chemisorption.

  10. 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

  11. Evaluation of gastrointestinal drug supersaturation and precipitation: strategies and issues.

    Science.gov (United States)

    Bevernage, Jan; Brouwers, Joachim; Brewster, Marcus E; Augustijns, Patrick

    2013-08-30

    Supersaturating drug delivery systems (SDDS) hold the promise of enabling intestinal absorption for difficult-to-formulate, poorly soluble drug candidates based on a design approach that includes (1) converting the drug into a high energy or rapidly dissolving system which presents a supersaturated solution to the gastrointestinal environment and (2) dosage form components that act to stabilize the formed metastable drug solution through nucleation and/or crystal growth inhibition. The appropriate development and study of SDDS require that useful and biorelevant supersaturation and precipitation assays are available. This review summarizes different methodological aspects of currently available in vitro assays, including the generation of supersaturation (solvent shift, pH shift or formulation-induced), the quantification of supersaturation and the detection of precipitation. Also down-scaled approaches, including 96-well plate setups, are described and situated in the pharmaceutical development cycle based on their consumption of API as well as time requirements. Subsequently, the ability to extrapolate in vitro supersaturation assessment to the in vivo situation is discussed as are direct and indirect clinical tools that can shed light on SDDS. By emphasizing multiple variables that affect the predictive power of in vitro assays (e.g. the nature of the test media, hydrodynamics, temperature and sink versus non-sink conditions), this review finally highlights the need for further harmonization and biorelevance improvement of currently available in vitro procedures for supersaturation and precipitation evaluation. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Calcium and Vitamin D Metabolism in Submariners. Carbon Dioxide, Sunlight, and Absorption Considerations

    Science.gov (United States)

    1986-01-15

    synthe- sis, and melatonin production by the pineal gland . Less obvious and explainable^are findings by several investigators of increased 30 yard...hypercapnia--’ ’ and- in the persistent renal response in the post-exposure period. Poyart ’ studied the bone CO? content in rats and found...calcium-pnosphorus metabolism in hypokinetic rats . Aviat. Space. Environ. Med. 55: 534-537. 47. Will, M.R. 1973. Intestinal absorption of calcium

  13. Phosphate binders and metabolic acidosis in patients undergoing maintenance hemodialysis—sevelamer hydrochloride, calcium carbonate, and bixalomer.

    Science.gov (United States)

    Sanai, Toru; Tada, Hideo; Ono, Takashi; Fukumitsu, Toma

    2015-01-01

    The serum bicarbonate (HCO3(-)) levels are decreased in chronic hemodialysis (HD) patients treated with sevelamer hydrochloride (SH). We assessed the effects of bixalomer on the chronic metabolic acidosis in these patients. We examined 12 of the 122 consecutive Japanese patients with end-stage renal disease on HD, who orally ingested a dose of SH (≥2250 mg), and an arterial blood gas analysis and biochemical analysis were performed before HD. Patients whose serum HCO3(-) levels were under 18 mmol/L were changed from SH to the same dose of bixalomer. A total of 12 patients were treated with a large amount of SH. Metabolic acidosis (a serum HCO3(-) level under 18 mmol/L) was found in eight patients. These patients were also treated with or without small dose of calcium carbonate (1.2 ± 1.1 g). The dose of SH was changed to that of bixalomer. After 1 month, the serum HCO3(-) levels increased from 16.3 ± 1.4 to 19.6 ± 1.7 mmol/L (P Metabolic acidosis was not observed in four patients (serum HCO3(-) level: 20.3 ± 0.7 mmol/L) likely because they were taking 3 g of calcium carbonate with SH. In the present study, the development of chronic metabolic acidosis was induced by HCl containing phosphate binders, such as SH, and partially ameliorated by calcium carbonate, then subsequently improved after changing the treatment to bixalomer.

  14. Oxygen spectroscopy and polarization-dependent imaging contrast (PIC)-mapping of calcium carbonate minerals and biominerals.

    Science.gov (United States)

    DeVol, Ross T; Metzler, Rebecca A; Kabalah-Amitai, Lee; Pokroy, Boaz; Politi, Yael; Gal, Assaf; Addadi, Lia; Weiner, Steve; Fernandez-Martinez, Alejandro; Demichelis, Raffaella; Gale, Julian D; Ihli, Johannes; Meldrum, Fiona C; Blonsky, Adam Z; Killian, Christopher E; Salling, C B; Young, Anthony T; Marcus, Matthew A; Scholl, Andreas; Doran, Andrew; Jenkins, Catherine; Bechtel, Hans A; Gilbert, Pupa U P A

    2014-07-17

    X-ray absorption near-edge structure (XANES) spectroscopy and spectromicroscopy have been extensively used to characterize biominerals. Using either Ca or C spectra, unique information has been obtained regarding amorphous biominerals and nanocrystal orientations. Building on these results, we demonstrate that recording XANES spectra of calcium carbonate at the oxygen K-edge enables polarization-dependent imaging contrast (PIC) mapping with unprecedented contrast, signal-to-noise ratio, and magnification. O and Ca spectra are presented for six calcium carbonate minerals: aragonite, calcite, vaterite, monohydrocalcite, and both hydrated and anhydrous amorphous calcium carbonate. The crystalline minerals reveal excellent agreement of the extent and direction of polarization dependences in simulated and experimental XANES spectra due to X-ray linear dichroism. This effect is particularly strong for aragonite, calcite, and vaterite. In natural biominerals, oxygen PIC-mapping generated high-magnification maps of unprecedented clarity from nacre and prismatic structures and their interface in Mytilus californianus shells. These maps revealed blocky aragonite crystals at the nacre-prismatic boundary and the narrowest calcite needle-prisms. In the tunic spicules of Herdmania momus, O PIC-mapping revealed the size and arrangement of some of the largest vaterite single crystals known. O spectroscopy therefore enables the simultaneous measurement of chemical and orientational information in CaCO3 biominerals and is thus a powerful means for analyzing these and other complex materials. As described here, PIC-mapping and spectroscopy at the O K-edge are methods for gathering valuable data that can be carried out using spectromicroscopy beamlines at most synchrotrons without the expense of additional equipment.

  15. Biodegradable calcium polyphosphate/polyvinyl-urethane carbonate composites for osteosynthesis applications

    Science.gov (United States)

    Ramsay, Scott Desmond

    The formation of biodegradable implants for use in osteosynthesis has been a major goal of biomaterials research for the past two to three decades. Self-reinforced polylactide systems represent the most significant success of this research to date, however with elastic constants of, at most, 12--15 GPa, they fail to provide the necessary initial stiffness required of devices designed for stabilizing fractures of major load-bearing bones. One objective of this study has been the development of a biodegradable composite suitable for fabrication of implants for the repair of fractures of major load-bearing bones. Specifically, this research has focussed on the use of calcium polyphosphate (CPP), an uiorganic polymer in combination with polyvinyl-urethane carbonate (PVUC) organic polymers. Composite samples were formed as interpenetrating phase composites (IPC), particle-reinforced composites (PRC), and fibre-reinforced composites (FRC). Additionally, the IPCs were produced as both monolithic and laminated specimens. PRC samples exhibit too low asmade elastic constant for fracture fixation applications, while the IPC and FRC samples exhibit desired as-made strength and bending stiffness but lose these properties too rapidly when exposed to aqueous-based in vitro aging, simulating in vivo conditions. An investigation to determine the mechanism of the rapid in vitro degradation was undertaken using a model IPC system to study the effect of the interfacial strength on the mechanical properties of the composite. In addition, these studies provided further support for a hypothesis to explain the observed high mechanical properties of the as-made CPP-PVUC interpenetrating phase composites. It was found that strong interfacial strength is very significant in obtaining appropriate mechanical properties in the IPC system. Results support the conclusion that a rapid loss of the CPP-PVUC interface through exposure to an aqueous environment, as well as stresses imposed on the CPP

  16. Penggunaan precipitated calcium carbonate (PCC sebagai filler untuk sol karet sepatu olah raga

    Directory of Open Access Journals (Sweden)

    Herminiwati

    2010-12-01

    Full Text Available Abstract The objective of the research was to investigate the utilization of Precipitated Calcium Carbonate (PCC as filler in producing sport shoe rubber soles. PCC is a white filler needed for production of nonblack colour rubber products. There are four types of PCC that have been used including two local PCC from Wonosari and East Java, and two imported PCC from Japan and Taiwan. The amount of PCC added into the sport shoe sole rubber compound was varied in 30,45,60,75 and 90 per hundred rubber (phr. The compounding was carried-out by using two roll mills machine, and the compound was subsequently measured their optimum vulcanization time by using rheometer. The produced compound was then subjected to vulcanistion process by using hydrolic press at temperature 1500C and pressure 150 kg/ cm2. The quality of shoes sole vulcanisates were compare to standard quality of SNI. 12-7075-2005 about cemented system sport shoes. The results indicated that the best formula of rubber compound for sport shoes sole were made by using NR 80 phr, NBR 20 phr, paraffinic oil 10 phr, aluminium silicate 30 phr, ZnO 5 phr, TiO2 10 phr, stearic acid 1 phr, vulkanox SP 1 phr, paraffin wax 1 phr, TMTD 0,5 phr, CBS 2 phr, sulphur 1,2 phr with the amount of PCC Actifort 700 of 45 phr. The best formula meet the requirement SNI 12-7075-2005 and they were characterized by tensile sterength 16,79 N/mm2, elongation at break 529,92% tear resistance 9,06 N/mm2, specific gravity 1,28 g/cm3, hardness 55 shore A, Grasselli absrassion resistancing filler. The local PCC from Wonosari can be used for substitution of the imported PCC as the white filler for the production of rubber compound sport shoes sole. However, particle size reduction and coating or surface treatment of local PCC were needed for improving the quality and the role of reinforcing filler.

  17. Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Zhi [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland); Daly, Michael [Mergon International, Castlepollard, Westmeath (Ireland); Clémence, Lopez [Polytech Grenoble, Grenoble (France); Geever, Luke M.; Major, Ian; Higginbotham, Clement L. [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland); Devine, Declan M., E-mail: ddevine@ait.ie [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland)

    2016-08-15

    Highlights: • The effects of stearic acid treatment for CaCO{sub 3} are highly influenced by the treatment method of application. • A new stearic acid treatment method, namely, combination treatment for CaCO{sub 3} was developed. • The combination treatment was compared with two of the existing methods dry and wet method. • The negative effects of void coalescence was minimised by the utilization of the combination method. - Abstract: Calcium carbonate (CaCO{sub 3}) is often treated with stearic acid (SA) to decrease its polarity. However, the method of application of the SA treatments has a strong influence on CaCO{sub 3} thermoplastic composite’s interfacial structure and distribution. Several of papers describe the promising effects of SA surface treatment, but few compare the treatment process and its effect on the properties of the final thermoplastic composite. In the current study, we assessed a new SA treatment method, namely, complex treatment for polymer composite fabrication with HDPE. Subsequently, a comparative study was performed between the “complex” process and the other existing methods. The composites were assessed using different experiments included scanning electron microscopy (SEM), void content, density, wettability, differential scanning calorimetry (DSC), and tensile tests. It was observed that the “complex” surface treatment yielded composites with a significantly lower voids content and higher density compared to other surface treatments. This indicates that after the “complex” treatment process, the CaCO{sub 3} particles and HDPE matrix are more tightly packed than other methods. DSC and wettability results suggest that the “wet” and “complex” treated CaCO{sub 3} composites had a significantly higher heat of fusion and moisture resistance compared to the “dry” treated CaCO{sub 3} composites. Furthermore, “wet” and “complex” treated CaCO{sub 3} composites have a significantly higher tensile

  18. Precipitation and dissolution of calcium carbonate: key processes bridging the bio- and geosciences (Vladimir Ivanovich Vernadsky Medal Lecture)

    Science.gov (United States)

    Gattuso, J.-P.

    2012-04-01

    In this Vladimir Ivanovich Vernadsky medal lecture, I will focus on the biogeochemical cycle of calcium carbonate (CaCO3) which is arguably one of the best example of a set processes that bridge the bio- and geosciences. The main reactions involved are calcification and dissolution that, respectively, manufacture and destroy calcium carbonate. Biology is intimately involved in these two processes which are key controls of the Earth's climate and leave remains that are of great use to human societies (as building materials) and geoscientists. I will illustrate the bridge between the bio- and geosciences by providing brief examples for each of the following four issues. (1) The marine cycle of CaCO3 and its relationship with climate. The release of CO2 by the precipitation of calcium carbonate and the uptake of CO2 by its dissolution are important controls of atmospheric CO2 and climate. The vertical distribution of Ψ, the ratio of CO2 released/used per CaCO3 precipitated/dissolved in the ocean will be shown to be consistent with the Högbom-Urey reactions. (2) The use of CaCO3 in paleooceanography. The remains of calcium carbonate shells and skeletons are wonderful archives of past environmental changes. Their isotopic composition and the concen-tration of trace elements are invaluable in the reconstruction of past climate. I will address the challenge of calibrating one of the proxies used to reconstruct past ocean pH. (3) The challenge of understanding calcification. Despite having been investigated for decades, many aspects of the physiological and molecular processes involved in calcification by marine organisms remain obscure. Recent breakthroughs, mostly on reef-building corals, will be briefly reviewed. (4) The response of calcification and dissolution to environmental change. The critical importance of CaCO3 precipitation and dissolution as climate controls makes it vital to understand their response to global environmental changes such as ocean warming and

  19. Ecological comparison of calcium hydroxide and sodium hydrogen carbonate as sorbents; Oekologischer Vergleich der Sorptionsmittel Calciumhydroxid und Natriumhydrogencarbonat

    Energy Technology Data Exchange (ETDEWEB)

    Pacher, Christian; Weber-Blaschke, Gabriele [Technische Univ. Muenchen, Freising (Germany). Lehrstuhl fuer Rohstoff- und Energietechnologie; Mocker, Mario [ATZ Entwicklungszentrum, Sulzbach-Rosenberg (Germany); Faulstich, Martin [Technische Univ. Muenchen, Straubing (Germany). Wissenschaftszentrum Straubing

    2009-07-01

    Lime products have long been used with success for flue gas purification in waste incineration plants, where they serve to eliminate acid gas pollutants such as sulphur dioxide, hydrogen chloride and hydrogen fluoride. This article presents excerpts of a study commissioned by the German lime industry association for the purpose of obtaining an unbiased well-founded comparison of the environmental impact of the two sorbents calcium hydroxide and sodium hydrogen carbonate. The following questions were addressed by the study: Which of the two flue gas additives provides greater environmental benefit under specified conditions? What parameters influence the outcome? How can the results be viewed in regard to different plant configurations?.

  20. Instant and supersaturated dissolution of naproxen and sesamin (poorly water-soluble drugs and supplements) nanoparticles prepared by continuous expansion of liquid carbon dioxide solution through long dielectric nozzle

    Science.gov (United States)

    Arita, Toshihiko; Manabe, Noriyoshi; Nakahara, Koichi

    2012-11-01

    Nanoparticles (NPs) of naproxen (a nonsteroidal anti-inflammatory drug, BCS Class 2) and sesamin (a poorly water-soluble lignan) were investigated. By applying a newly developed rapid expansion system of liquid carbon dioxide solutions equipped with a dielectric nozzle, well-separated and fine both naproxen NPs (averaged particle size (APS) = 46.9 nm) and sesamin NPs (APS = 60.2 nm) were obtained without heating, surfactants, and co-solvents. Obtained naproxen and sesamin NPs had large surface/weight ratio, therefore, they showed instant dissolution to water until about ten percent higher than the saturated concentrations. In addition, the technique developed in the study has big advantage on producing especially drug NPs because the NPs produced by the method never includes neither poisonous additives (especially co-solvents and detergents) nor thermally denatured compounds.

  1. Instant and supersaturated dissolution of naproxen and sesamin (poorly water-soluble drugs and supplements) nanoparticles prepared by continuous expansion of liquid carbon dioxide solution through long dielectric nozzle

    Energy Technology Data Exchange (ETDEWEB)

    Arita, Toshihiko, E-mail: tarita@tagen.tohoku.ac.jp [Tohoku University, Institute of Multidisciplinary Research for Advanced Materials (Japan); Manabe, Noriyoshi [Tohoku University, Graduate School of Engineering (Japan); Nakahara, Koichi [Suntory Bussiness Expert Limited, Frontier Center for Value Creation (Japan)

    2012-11-15

    Nanoparticles (NPs) of naproxen (a nonsteroidal anti-inflammatory drug, BCS Class 2) and sesamin (a poorly water-soluble lignan) were investigated. By applying a newly developed rapid expansion system of liquid carbon dioxide solutions equipped with a dielectric nozzle, well-separated and fine both naproxen NPs (averaged particle size (APS) = 46.9 nm) and sesamin NPs (APS = 60.2 nm) were obtained without heating, surfactants, and co-solvents. Obtained naproxen and sesamin NPs had large surface/weight ratio, therefore, they showed instant dissolution to water until about ten percent higher than the saturated concentrations. In addition, the technique developed in the study has big advantage on producing especially drug NPs because the NPs produced by the method never includes neither poisonous additives (especially co-solvents and detergents) nor thermally denatured compounds.

  2. Low temperature synthesis of high quality carbon nanospheres through the chemical reactions between calcium carbide and oxalic acid

    Energy Technology Data Exchange (ETDEWEB)

    Xie Yonggui, E-mail: xieyg2004@163.com [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Huang Qizhong, E-mail: qzhuang@mail.csu.edu.cn [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Huang Baiyun [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Xie Xiangmin [Applied Chemistry Department, College of Science, Hunan Agricultural University, Changsha, Hunan 410128 (China)

    2010-11-01

    Carbon nanospheres (CNSs) were synthesized through the chemical reactions of calcium carbide and oxalic acid without using catalysts. The chemical reactions were carried out in a sealed stainless steel pressure vessel with various molar ratios at temperatures of 65-250 deg. C. The synthesized CNSs have been characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) attached to the SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The total yield of carbonaceous materials relative to the starting material is about 4% (w/w). SEM and TEM results reveal that the percentage of CNSs is high (>95%). The CNSs that have been synthesized are roe-like spheres of relatively uniform size with diameters of 60-120 nm. The attached EDS result shows that the carbon content of CNSs reaches up to 98%.

  3. ELECTRICAL RESISTIVITY, CRYSTALLIZATION AND MECHANICAL PROPERTIES OF POLYPROPYLENE/MULTI-WALLED CARBON NANOTUBE/CALCIUM CARBONATE COMPOSITES PREPARED BY MELT MIXING

    Institute of Scientific and Technical Information of China (English)

    Ha-da Bao; Zhao-xia Guo; Jian Yu

    2009-01-01

    Polypropylene (PP)/multi-walled carbon nanotube (MWCNT)/calcium carbonate (CaCO3) composites are prepared by melt mixing using two types of CaCO3 of different sizes. The electrical resistivities of the composites with the two types of CaCO3 are all lower than those of the corresponding PP/MWCNT composites at various MWCNT loadings (1 wt%-5 wt%). The morphology of the composites is investigated by field emission scanning electron microscopy (FESEM). The crystallization behavior of PP in the composites is characterized by differential scanning calorimetry (DSC). The storage modulus, as measured by dynamic mechanical analysis (DMA), increases significantly by the presence of CaCO3.

  4. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate.

    Science.gov (United States)

    Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

    2016-03-25

    The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

  5. Consolidation of degraded ornamental porous limestone stone by calcium carbonate precipitation induced by the microbiota inhabiting the stone.

    Science.gov (United States)

    Jimenez-Lopez, C; Rodriguez-Navarro, C; Piñar, G; Carrillo-Rosúa, F J; Rodriguez-Gallego, M; Gonzalez-Muñoz, M T

    2007-08-01

    Although it has already been shown that calcareous stone can be consolidated by using a bacterially inoculated culture medium, a more user-friendly method is the in situ application of a sterile culture medium that is able to activate, among the microbial community of the stone, those bacteria with a potential for calcium carbonate precipitation. In order to test this new method for stone consolidation, non-sterilized decayed porous limestone was immersed in sterile nutritional media. Results were compared to those of the runs in which stone sterilized prior to the treatment was used. The effects of the microbial community on stone consolidation were determined by recording the evolution of the culture media chemistry. The treated stone was tested for mechanical resistance and porosity. Results demonstrate that the tested media were able to activate bacteria from the microbial community of the stone. As a consequence of the growth of these bacteria, an alkalinization occurred that resulted in calcium carbonate precipitation. The new precipitate was compatible with the substrate and consolidated the stone without pore plugging. Therefore, a good candidate to in situ consolidate decayed porous limestone is the application of a sterile culture medium with the characteristics specified in the present study.

  6. The synthesis of spherical calcium carbonate composite in amphiphilic PS-b-PAA solution and its thermal dynamic characteristic

    Institute of Scientific and Technical Information of China (English)

    YUE Linhai; JIN Dalai

    2004-01-01

    Spherical calcium carbonate composite is synthesized in the solution of amphiphilic block copolymer of polystyrene(PS) and poly(acrylic acid)(PAA). SEM and XRD measurements show that the diameter of the particulates decreases with the augment of the PS-b-PAA concentration, crystalline in the composite is calcite and its morphology as well as the structure is changed too. TG-DTA together with IR analysis is applied to investigating the thermal dynamic behavior of the composite. The results show that the composite is mainly composed of two phases, that is, the nano- crystalline calcium carbonate and the PS-b-PA-Ca composites. PS phase decomposes first with a large heat release at about 330℃. However, the PAA chains have relatively high thermal stability, probably due to the structural Ca-O bond, and decomposes at above 400℃. Matching opinions are used to explain the possible reasons for the regular as well as the particular characteristics of the composite corresponding to a certain copolymer concentration.

  7. The role of inorganic ions in the calcium carbonate scaling of seawater reverse osmosis systems

    KAUST Repository

    Waly, Tarek

    2012-01-01

    In supersaturated solutions the period preceding the start of \\'measurable\\' crystallization is normally referred to as the \\'induction time\\'. This research project aimed to investigate the induction times of CaCO 3 in the presence of Mg 2+ and SO 4 2-. The prepared synthetic solutions have the same ionic strength values found in the Gulf of Oman SWRO concentrates at 30% and 50% recovery. The results showed a significant increase in the induction time by 1140%, 2820%, and 3880% for a recovery of 50%, when adding SO 4 2- only, Mg 2+ only, or both Mg 2+ and SO 4 2-, respectively, to synthetic SWRO concentrate compared to that obtained in the absence of Mg 2+ and SO 4 2- at an initial pH of 8.3. The increase in the induction time in the presence of SO 4 2- was more than likely to be due to nucleation and growth inhibition while the presence of Mg 2+ affected the nucleation and growth through both complexation and inhibition. After a 5-month solution stabilization period, ESEM and XRD analyses showed aragonite in solutions containing Mg 2+. On the contrary, calcite was the final crystal phase formed in solutions with no Mg 2+. This suggests that magnesium may play an important role in inhibiting the formation of calcite. © 2011 Elsevier B.V..

  8. Supersaturation-limited amyloid fibrillation of insulin revealed by ultrasonication.

    Science.gov (United States)

    Muta, Hiroya; Lee, Young-Ho; Kardos, József; Lin, Yuxi; Yagi, Hisashi; Goto, Yuji

    2014-06-27

    Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. We proposed that ultrasonication may be an effective agitation to trigger nucleation that would otherwise not occur under the persistent metastability of supersaturation. However, the roles of supersaturation and effects of ultrasonication have not been elucidated in detail except for limited cases. Insulin is an amyloidogenic protein that is useful for investigating the mechanisms underlying amyloid fibrillation with biological relevance. We studied the alcohol-induced amyloid fibrillation of insulin using various concentrations of 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol at pH 2.0 and 4.8. Ultrasonic irradiation effectively triggered fibrillation under conditions in which insulin retained persistent supersaturation. Structural analyses by circular dichroism, Fourier transform infrared spectroscopy, transmission electron microscopy, and atomic force microscopy revealed that the dominant structures of fibrils varied between parallel and antiparallel β-sheets depending on the solvent conditions. pH and alcohol concentration-dependent phase diagrams showed a marked difference before and after the ultrasonic treatment, which indicated that the persistent metastability of supersaturation determined the conformations of insulin. These results indicate the importance of an alternative view of amyloid fibrils as supersaturation-limited crystal-like aggregates formed above the solubility limit. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  9. Supersaturation-limited Amyloid Fibrillation of Insulin Revealed by Ultrasonication*

    Science.gov (United States)

    Muta, Hiroya; Lee, Young-Ho; Kardos, József; Lin, Yuxi; Yagi, Hisashi; Goto, Yuji

    2014-01-01

    Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. We proposed that ultrasonication may be an effective agitation to trigger nucleation that would otherwise not occur under the persistent metastability of supersaturation. However, the roles of supersaturation and effects of ultrasonication have not been elucidated in detail except for limited cases. Insulin is an amyloidogenic protein that is useful for investigating the mechanisms underlying amyloid fibrillation with biological relevance. We studied the alcohol-induced amyloid fibrillation of insulin using various concentrations of 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol at pH 2.0 and 4.8. Ultrasonic irradiation effectively triggered fibrillation under conditions in which insulin retained persistent supersaturation. Structural analyses by circular dichroism, Fourier transform infrared spectroscopy, transmission electron microscopy, and atomic force microscopy revealed that the dominant structures of fibrils varied between parallel and antiparallel β-sheets depending on the solvent conditions. pH and alcohol concentration-dependent phase diagrams showed a marked difference before and after the ultrasonic treatment, which indicated that the persistent metastability of supersaturation determined the conformations of insulin. These results indicate the importance of an alternative view of amyloid fibrils as supersaturation-limited crystal-like aggregates formed above the solubility limit. PMID:24847058

  10. Surface area dependence of calcium isotopic reequilibration in carbonates: Implications for isotopic signatures in the weathering zone

    Science.gov (United States)

    Fernandez, N. M.; Druhan, J. L.; Potrel, A.; Jacobson, A. D.

    2016-12-01

    The concept of dynamic equilibrium carries the implicit assumption of continued isotopic exchange between a mineral and the surrounding fluid. While this effect has received much attention in the marine paleoproxy literature, it has been relatively overlooked in application to the terrestrial environment. In weathering systems, a potential consequence is that rapid reequilibration may alter or erase isotopic signatures generated during secondary mineral formation. The extent and timescale over which isotopic signatures are reset in these hydrologic systems is unknown. Using reactive transport modeling, we show isotopic reequilibration under conditions reflecting terrestrial hydrologic settings to be significant and dependent on the reactive surface area of the solid. In particular, we suggest that the non-traditional stable isotopes commonly used in application to carbonates (e.g., Ca, Mg, Sr) are sensitive to these effects due to their rapid reaction rates. We aim to characterize the dependence of Ca isotopic reequilibration on surface area during calcite precipitation via batch experiments conducted at ambient temperature over 48-hour time periods. Calcite precipitation was performed in a closed batch reactor utilizing a controlled free-drift method. The batch reactors contained mixed supersaturated solutions of CaCl2 and NaHCO3 at an initial pH of 8.54. Precipitation was initiated by seed inoculation of calcite crystals with two distinct, pre-constrained surface areas. All experiments achieved the same final state of chemical equilibrium, but as expected, the fastest approach to equilibrium occurred for experiments employing calcite seeds with the highest surface area. This implies that differences in equilibrated Ca isotope ratios (δ44/40Ca) should reflect differences in surface area. This prediction is upheld by models of the experiments, indicating a measureable difference in δ44Ca during calcite precipitation where the higher surface area corresponds to

  11. Strontium hydroxyapatite and strontium carbonate as templates for the precipitation of calcium-phosphates in the absence and presence of fluoride

    Science.gov (United States)

    Sternitzke, Vanessa; Janousch, Markus; Heeb, Michèle B.; Hering, Janet G.; Johnson, C. Annette

    2014-06-01

    The heterogeneous precipitation of calcium-phosphates on calcium hydroxyapatite (Ca10(PO4)6(OH)2 or HAP) in the presence and absence of fluoride is important in the formation of bone and teeth, protection against tooth decay, dental and skeletal fluorosis and defluoridation of drinking water. Strontium hydroxyapatite (Sr10(PO4)6(OH)2 or SrHAP) and strontium carbonate (SrCO3) were used as calcium-free seed templates in precipitation experiments conducted with varying initial calcium-to-phosphate (Ca/P) or calcium-to-phosphate-to-fluoride (Ca/P/F) ratios. Suspensions of SrHAP or SrCO3 seed templates (which were calcium-limited for both templates and phosphate-limited in the case of SrCO3) were reacted at pH 7.3 (25 °C) over 3 days. The resulting solids were examined with Scanning Transmission Electron Microscopy (STEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Near Edge Structure (XANES), and Extended X-ray Absorption Fine Structure spectroscopy (EXAFS). Calcium apatite was the predominant phase identified by all techniques independent of the added Ca/P ratios and of the presence of fluoride. It was not possible to make an unambiguous distinction between HAP and fluorapatite (Ca10(PO4)6F2, FAP). The apatite was calcium-deficient and probably contained some strontium.

  12. Exposure Assessment and Inflammatory Response Among Workers Producing Calcium Carbonate Nanomaterials

    Science.gov (United States)

    Cui, Ling

    Problem: Nanotechnology is one of the most rapidly growing fields of science and engineering, and its applications have expanded to numerous research and industrial sectors, from consumer products to medicine to energy. Nano-materials and nanotechnology promise substantial benefits. However, there are many uncertainties and concerns regarding human health and the environment. Numerous toxicological studies on animals and cells in vitro have demonstrated that nanomaterials could cause various adverse health effects, including inflammation, oxidative stress, fibrosis and mutagenesis in the lungs, and cardiovascular and nervous system impairment. Objectives: The overall objective of this study was to characterize particulate exposures in a calcium carbonate nanoparticle manufacturing facility, investigate possible respiratory and cardiovascular effects, and explore the plausibility of an inflammatory mechanism. The associations between exposure level and various health outcomes were investigated. Methodology: Each job was characterized by mass, number and surface area concentration. Job classification was performed based on ranking of the exposure level and statistical models. Lung function tests, exhaled NO and blood pressure (BP) were measured before and after the workshift in the year of 2011. Inflammatory cytokines from induced sputum were measured cross-sectionally in the year of 2011. Data of lung function tests and blood pressure were collected cross-sectionally in the year of 2012. The associations between each exposure metric and health measures in 2012 were investigated. Only mass concentration was linked to both 2011 and 2012 health outcomes. Results: The sampling and analytic methodology used in the study presents the potential to characterize nanoparticle exposure for a variety of operational processes. We found the highest mass exposure occurred at bagging job whereas the highest number and surface area concentration was found at modification

  13. Effect of cetyl trimethyl ammonium bromide concentration on structure, morphology and carbon dioxide adsorption capacity of calcium hydroxide based sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Hlaing, Nwe Ni, E-mail: nwenihlaing76@gmail.com [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo (Japan); Department of Physics, University of Yangon, 11041 Kamayut, Yangon (Myanmar); Vignesh, K., E-mail: vignesh134@gmail.com [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Anano Sphere Sdn Bhd, Lorong Industri 11, Kawasan Industri Bukit Panchor, 14300 Nibong Tebal, Penang (Malaysia); Sreekantan, Srimala, E-mail: srimala@usm.my [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Pung, Swee-Yong [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Hinode, Hirofumi; Kurniawan, Winarto [Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo (Japan); Othman, Radzali [Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Malacca (Malaysia); Thant, Aye Aye [Department of Physics, University of Yangon, 11041 Kamayut, Yangon (Myanmar); Mohamed, Abdul Rahman [Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Salim, Chris [Department of Environmental Engineering, Surya University, Tangerang 15810, Banten (Indonesia)

    2016-02-15

    Graphical abstract: Carbonation conversions of (a) CC, (b) CH-2, (c) CH-4, (d) CH-6, (e) CH-8 precursor adsorbents for 10 cycles. - Highlights: • Ca(OH){sub 2} precursor was synthesized using precipitation method. • The effect of CTAB concentration on the synthesis of Ca(OH){sub 2} was studied. • The sorbent synthesized using 0.8 M of CTAB showed good CO{sub 2} adsorption capacity. • The cyclic stability of Ca(OH){sub 2} was increased with increase of CTAB concentration. - Abstract: Calcium hydroxide (Ca(OH){sub 2}) has been proposed as an important material for industrial, architectural, and environmental applications. In this study, calcium acetate was used as a precursor and cetyl trimethyl ammonium bromide (CTAB) was used as a surfactant to synthesize Ca(OH){sub 2} based adsorbents for carbon dioxide (CO{sub 2}) capture. The effect of CTAB concentration (0.2–0.8 M) on the structure, morphology and CO{sub 2} adsorption performance of Ca(OH){sub 2} was studied in detail. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), BET surfaced area and thermogravimetry-differential thermal analysis (TG–DTA) techniques. The phase purity, crystallite size, Brunauer–Emmett–Teller (BET) surface area and CO{sub 2} adsorption performance of Ca(OH){sub 2} precursor adsorbents were significantly increased when the concentration of CTAB was increased. XRD results showed that pure Ca(OH){sub 2} phase was obtained at the CTAB concentration of 0.8 M. TGA results exhibited that 0.8 M of CTAB-assisted Ca(OH){sub 2} precursor adsorbent possessed a residual carbonation conversion of ∼56% after 10 cycles.

  14. Isolation and metagenomic characterization of bacteria associated with calcium carbonate and struvite precipitation in a pure moving bed biofilm reactor-membrane bioreactor.

    Science.gov (United States)

    Gonzalez-Martinez, A; Leyva-Díaz, J C; Rodriguez-Sanchez, A; Muñoz-Palazon, B; Rivadeneyra, A; Poyatos, J M; Rivadeneyra, M A; Martinez-Toledo, M V

    2015-01-01

    A bench-scale pure moving bed bioreactor-membrane bioreactor (MBBR-MBR) used for the treatment of urban wastewater was analyzed for the identification of bacterial strains with the potential capacity for calcium carbonate and struvite biomineral formation. Isolation of mineral-forming strains on calcium carbonate and struvite media revealed six major colonies with a carbonate or struvite precipitation capacity in the biofouling on the membrane surface and showed that heterotrophic bacteria with the ability to precipitate calcium carbonate and struvite constituted ~7.5% of the total platable bacteria. These belonged to the genera Lysinibacillus, Trichococcus, Comamomas and Bacillus. Pyrosequencing analysis of the microbial communities in the suspended cells and membrane biofouling showed a high degree of similarity in all the samples collected with respect to bacterial assemblage. The study of operational taxonomic units (OTUs) identified through pyrosequencing suggested that ~21% of the total bacterial community identified in the biofouling could potentially form calcium carbonate or struvite crystals in the pure MBBR-MBR system used for the treatment of urban wastewater.

  15. CRACK2. Modelling calcium carbonate deposition from bicarbonate solutions in cracks in concrete

    DEFF Research Database (Denmark)

    Brodersen, Knud Erik

    2003-01-01

    The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description ofthe model. Hydroxyl ions are transported...... by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. Thecementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide...... dissolved in the pore solution. Diffusive migration of cesium as radioactive isotope is also considered. Electrical interaction of the migratingions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack...

  16. 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…

  17. 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…

  18. Technical Note: Calcium and carbon stable isotope ratios as paleodietary indicators.

    Science.gov (United States)

    Melin, Amanda D; Crowley, Brooke E; Brown, Shaun T; Wheatley, Patrick V; Moritz, Gillian L; Yit Yu, Fred Tuh; Bernard, Henry; DePaolo, Donald J; Jacobson, Andrew D; Dominy, Nathaniel J

    2014-08-01

    Calcium stable isotope ratios are hypothesized to vary as a function of trophic level. This premise raises the possibility of using calcium stable isotope ratios to study the dietary behaviors of fossil taxa and to test competing hypotheses on the adaptive origins of euprimates. To explore this concept, we measured the stable isotope composition of contemporary mammals in northern Borneo and northwestern Costa Rica, two communities with functional or phylogenetic relevance to primate origins. We found that bone collagen δ(13) C and δ(15) N values could differentiate trophic levels in each assemblage, a result that justifies the use of these systems to test the predicted inverse relationship between bioapatite δ(13) C and δ(44) Ca values. As expected, taxonomic carnivores (felids) showed a combination of high δ(13) C and low δ(44) Ca values; however, the δ(44) Ca values of other faunivores were indistinguishable from those of primary consumers. We suggest that the trophic insensitivity of most bioapatite δ(44) Ca values is attributable to the negligible calcium content of arthropod prey. Although the present results are inconclusive, the tandem analysis of δ(44) Ca and δ(13) C values in fossils continues to hold promise for informing paleodietary studies and we highlight this potential by drawing attention to the stable isotope composition of the Early Eocene primate Cantius.

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

    NARCIS (Netherlands)

    Jones, Elizabeth M.; Fenton, Mairi; Meredith, Michael P.; Clargo, Nicola M.; Ossebaar, Sharyn; Ducklow, Hugh W.; Venables, Hugh J.; de Baar, Henricus

    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 (Omega) for two biologically-important

  20. The Study of Thermal Decomposition of Natural Calcium Carbonate by the Temperature-programmed Mass Spectrometry Technique

    Directory of Open Access Journals (Sweden)

    S.N. Danilchenko

    2016-11-01

    Full Text Available The experiments have shown that the heating range for quantitative evolution of carbon dioxide gas (CO2 from natural calcium carbonates (e.g., chalk, corals, shells of the Anadara clams (Anadara inaequivalvis, shell of bird eggs is from 500 to 850 C with a total heating time of 30-50 minutes. The only exception is the sample of a mortar from a masonry of Saint Sophia Cathedral (the architectural monument of XI century, in which the lowest border of the heating range for carbon dioxide evolution is 400 C. The shape of the CO2 evolution curves for every sample is significantly different in width and intensity as compared to the standard sample (chemically pure synthetic CaCO3. The results, which were obtained on the thermoprogrammed mass-spectrometry (TP‑MS unit, designed and produced by the authors of the current paper, are of great importance for the development of a gas input technique for radiocarbon dating with accelerator mass-spectrometry.

  1. Fabrication of Carbonate Apatite Block through a Dissolution–Precipitation Reaction Using Calcium Hydrogen Phosphate Dihydrate Block as a Precursor

    Directory of Open Access Journals (Sweden)

    Kanji Tsuru

    2017-03-01

    Full Text Available Carbonate apatite (CO3Ap block, which is a bone replacement used to repair defects, was fabricated through a dissolution–precipitation reaction using a calcium hydrogen phosphate dihydrate (DCPD block as a precursor. When the DCPD block was immersed in NaHCO3 or Na2CO3 solution at 80 °C, DCPD converted to CO3Ap within 3 days. β-Tricalcium phosphate was formed as an intermediate phase, and it was completely converted to CO3Ap within 2 weeks when the DCPD block was immersed in Na2CO3 solution. Although the crystal structures of the DCPD and CO3Ap blocks were different, the macroscopic structure was maintained during the compositional transformation through the dissolution–precipitation reaction. CO3Ap block fabricated in NaHCO3 or Na2CO3 solution contained 12.9 and 15.8 wt % carbonate, respectively. The diametral tensile strength of the CO3Ap block was 2 MPa, and the porosity was approximately 57% regardless of the carbonate solution. DCPD is a useful precursor for the fabrication of CO3Ap block.

  2. 硝酸浸取磷矿制轻质碳酸钙工艺研究%Preparation of light calcium carbonate by nitric acid leaching phosphate ore

    Institute of Scientific and Technical Information of China (English)

    胡兆平; 贾洪秀; 庞世花; 刘阳; 贾亮

    2013-01-01

    Calcium nitrate crystal can be obtained by freezing crystallization method from acid solution acquired from nitric acid extracting phosphate rock.After that,light calcium carbonate was prepared by carbonization reaction between ammonium hydrogen carbonate and calcium nitrate crystal.Results show that,the initial carbonization reaction temperature was the normal temperature,mass fraction of calcium nitrate solution was about 23%,ammonium hydrogen carbonate and ammonia dosages were both 110% of theoretical addition amounts,and products were washed by four times of product weight washing water.All quality indexes of the product can meet the standard of Industrial Precipitated Calcium Carbonate,HG/T 2226-2000.%硝酸萃取磷矿后的酸解液,通过冷冻结晶法得到硝酸钙晶体,然后以硝酸钙为原料,通过加入碳酸氢铵进行碳化制取轻质碳酸钙.结果表明,碳化反应的初始反应温度为常温,硝酸钙溶液的质量分数为23%左右,碳酸氢铵和氨水按理论加入量的110%进行反应,用产品质量的4倍洗水量洗涤产品,制备的轻质碳酸钙产品各项指标均达到HG/T 2226-2000《工业沉淀碳酸钙》标准的要求.

  3. Amelogenin-chitosan matrix for human enamel regrowth: effects of viscosity and supersaturation degree.

    Science.gov (United States)

    Ruan, Qichao; Siddiqah, Nadia; Li, Xiaochen; Nutt, Steven; Moradian-Oldak, Janet

    2014-08-01

    We recently reported an amelogenin-chitosan (CS-AMEL) hydrogel as a promising biomimetic material for future in situ human enamel regrowth. To further optimize the necessary conditions for clinical applicability of CS-AMEL hydrogel, herein we studied the effects of viscosity and supersaturation degree on the size and orientation of synthetic crystals by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Raising the hydrogel viscosity by increasing chitosan concentration from 1% to 2% (w/v) improved the orientation of the crystals, while a higher supersaturation (σ(HAp) >10.06, [Ca(2+)] >5 mM) resulted in the formation of random crystals with larger sizes and irregular structures. We conclude that optimal conditions to produce organized enamel-like crystals in a CS-AMEL hydrogel are: 2% (w/v) chitosan, 2.5 mM calcium, and 1.5 mM phosphate (degree of supersaturation = 8.23) and 200 µg/ml of amelogenin.

  4. Amelogenin-assisted ex vivo remineralization of human enamel: effects of supersaturation degree and fluoride concentration

    Science.gov (United States)

    Fan, Yuwei; Nelson, James R.; Alvarez, Jason R.; Hagan, Joseph; Berrier, Allison; Xu, Xiaoming

    2011-01-01

    The formation of organized nanocrystals that resemble enamel is crucial for successful enamel remineralization. Calcium, phosphate and fluoride ions and amelogenin are important ingredients for the formation of organized hydroxyapatite (HAP) crystals in vitro. However, the effects of these remineralization agents on the enamel crystal morphology have not been thoroughly studied. The objective of this study was to investigate the effects of fluoride ions, supersaturation degree and amelogenin on the crystal morphology and organization of ex vivo remineralized human enamel. Extracted third molars were sliced thin and acid-etched to provide the enamel surface for immersion in different remineralization solutions. The crystal morphology and mineral phase of the remineralized enamel surface were analyzed by FE-SEM, ATR-FTIR and XRD. The concentration of fluoride and supersaturation degree of hydroxyapatite had significant effects on the crystal morphology and crystal organization, which varied from plate-like loose crystals to rod-like densely packed nanocrystal arrays. Densely packed arrays of fluoridated hydroxyapatite nanorods were observed under the following conditions: σ(HAP) = 10.2±2.0 with fluoride 1.5±0.5 mg/L and amelogenin 40±10 µg/mL, pH 6.8±0.4. A phase diagram summarized the conditions that form dense or loose hydroxyapatite nanocrystal structures. This study provides the basis for the development of novel dental materials for caries management. PMID:21256987

  5. Structure of supersaturated solution and crystal nucleation induced by diffusion

    Science.gov (United States)

    Ooshima, Hiroshi; Igarashi, Koichi; Iwasa, Hideo; Yamamoto, Ren

    2013-06-01

    The effect of a seed crystal on nucleation of L-alanine from a quiescent supersaturated solution was investigated. When a seed crystal was not used, nucleation did not occur at least for 5 h. When a seed crystal was introduced into the supersaturated solution with careful attention to avoid convection of the solution, fine crystals appeared at the place far from the seed crystal. At that time, there was no convection at the place that fine crystals appeared. Namely, there was no possibility that those fine crystals came from the surface of seed crystal. We supposed that nucleation was induced by directional diffusion of solute molecules caused by growth of the seed crystal. In order to prove this hypothesis, we designed an experiment using an apparatus composed of two compartments divided by a dialysis membrane that L-alanine molecules could freely permeate. Two supersaturated solutions having a supersaturation ratio of 1.2 and a smaller ratio were placed in the two compartments in the absence of seed crystals. This apparatus allowed the directional diffusion of solute molecules between two solutions. Nucleation occurred within 30 min. The frequency of nucleation among 7-times repeated experiments was in proportion to the difference of supersaturation ratio between the two solutions. This result poses a new mechanism of the secondary nucleation that the directional diffusion caused by growth of existing crystals induces nucleation.

  6. Physical chemistry of supersaturated solutions and implications for oral absorption.

    Science.gov (United States)

    Taylor, Lynne S; Zhang, Geoff G Z

    2016-06-01

    Amorphous solid dispersion (ASD) formulations are widely used for delivery of poorly soluble drugs for dissolution enhancement and bioavailability improvement. When administered, ASDs often exhibit fast dissolution to yield supersaturated solutions. The physical chemistry of these supersaturated solutions is not well understood. This review will discuss the concepts of solubility, supersaturation, and the connection to membrane transport rate. Liquid-liquid phase separation (LLPS), which occurs when the amorphous solubility is exceeded, leading to solutions with interesting properties is extensively discussed as a phenomenon that is relevant to all enabling formulations. The multiple physical processes occurring during dissolution of the ASD and during oral absorption are analyzed. The beneficial reservoir effect of a system that has undergone LLPS is demonstrated, both experimentally and conceptually. It is believed that formulations that rapidly supersaturate and subsequently undergo LLPS, with maintenance of the supersaturation at this maximum value throughout the absorption process, i.e. those that exhibit "spring and plateau" behavior, will give superior performance in terms of absorption. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Utilization of calcium carbonate particles from eggshell waste as coating pigments for ink-jet printing paper.

    Science.gov (United States)

    Yoo, Sukjoon; Hsieh, Jeffery S; Zou, Peter; Kokoszka, John

    2009-12-01

    The effective treatment and utilization of biowaste have been emphasized in our society for environmental and economic concerns. Recently, the eggshell waste in the poultry industry has been highlighted because of its reclamation potential. This study presents an economical treatment process to recover useful bioproducts from eggshell waste and their utilization in commercial products. We developed the dissolved air floatation (DAF) separation unit, which successfully recovered 96% of eggshell membrane and 99% of eggshell calcium carbonate (ECC) particles from eggshell waste within 2 h of operation. The recovered ECC particles were utilized as coating pigments for ink-jet printing paper and their impact on the ink density and paper gloss were investigated. The addition of the ECC particles as coating pigments enhances the optical density of cyan, magenta and yellow inks while decreasing the black ink density and the gloss of the coated paper.

  8. 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.

  9. Effect of solid loading and aggregate size on the rheological behavior of PDMS/Calcium Carbonate suspensions

    Directory of Open Access Journals (Sweden)

    E. Behzadfar

    2009-12-01

    Full Text Available The purpose of this study is to examine the effect of solid loading and aggregate size on the rheological behavior of PDMS (polydimethylsiloxane/CC (calcium carbonate suspensions. Mixtures containing 10 to 40 vol% of CC were prepared; the effect of shear rate and particle content on aggregate size and rheological properties was studied. Rheological properties including viscosity, loss modulus, storage modulus and yield stress were measured using rotational and oscillatory rheometry. Casson's equation was found to satisfactorily model the samples' stress response as a function of shear rate for different solid content. While solid content did not have any effect on the aggregate size, shear rate did influence the aggregate median diameter. It was observed that suspensions with higher aggregate size had a higher viscosity. In general, for a given volume fraction, a small change in the aggregate size had a significant impact on the viscosity, particularly at low shear rates.

  10. Vapor diffusion method: Dependence of polymorphs and morphologies of calcium carbonate crystals on the depth of an aqueous solution

    Science.gov (United States)

    Liu, Qing; Wang, Hai-Shui; Zeng, Qiang

    2016-09-01

    The polymorph control of calcium carbonate by the vapor diffusion method is still a challenging issue because the resultant crystal polymorphs and morphologies highly depend on the experimental setup. In this communication, we demonstrated that the concentration gradients accompanied by the vapor diffusion method (ammonia concentration, pH and the ratio of CO32- to Ca2+ are changed with the solution depth and with time) are probably the main reasons to significantly affect the formation of crystal polymorphs. Raman, SEM and XRD data showed that calcite and vaterite crystals were preferred to nucleate and grow in the upper or the lower areas of aqueous solution respectively. The above results can be explained by the gradient effect.

  11. 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.

  12. Preeminent productivity of 1,3-propanediol by Clostridium butyricum JKT37 and the role of using calcium carbonate as pH neutraliser in glycerol fermentation.

    Science.gov (United States)

    Tee, Zhao Kang; Jahim, Jamaliah Md; Tan, Jian Ping; Kim, Byung Hong

    2017-06-01

    Calcium carbonate was evaluated as a replacement for the base during the fermentation of glycerol by a highly productive strain of 1,3-propanediol (PDO), viz., Clostridium butyricum JKT37. Due to its high specific growth rate (µmax=0.53h(-1)), 40g/L of glycerol was completely converted into 19.6g/L of PDO in merely 7h of batch fermentation, leaving only acetate and butyrate as the by-products. The accumulation of these volatile fatty acids was circumvented with the addition of calcium carbonate as the pH neutraliser before the fermentation was inoculated. An optimal amount of 15g/L of calcium carbonate was statistically determined from screening with various glycerol concentrations (20-120g/L). By substituting potassium hydroxide with calcium carbonate as the pH neutraliser for fermentation in a bioreactor, a similar yield (YPDO/glycerol=0.6mol/mol) with a constant pH was achieved at the end of the fermentation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Enhancing and Sustaining AMG 009 Dissolution from a Matrix Tablet Via Microenvironmental pH Modulation and Supersaturation

    OpenAIRE

    Bi, Mingda; Kyad, Ali; Kiang, Yuan-Hon; Alvarez-Nunez, Fernando; Alvarez, Francisco

    2011-01-01

    The objective of this study was to investigate the combined effect of pH modifiers and nucleation inhibitors on enhancing and sustaining the dissolution of AMG 009 tablet via supersaturation. Several bases and polymers were added as pH modifiers and nucleation inhibitors, respectively, to evaluate their impact on the dissolution of AMG 009 tablets. The results indicate that sodium carbonate, among the bases investigated, enhanced AMG 009 dissolution the most. HPMC E5 LV, among the nucleation ...

  14. Depositional environments inferred from variations of calcium carbonate, organic carbon, and sulfide sulfur: a core from southeastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Paropkari, A; Iyer, S.D.; Chauhan, O.S; PrakashBabu, C.

    The variations in CaCO3 and organic carbon and their inter-relationship in a core from the southeastern Arabian Sea (water depth 2,212 m) have been used to demarcate the Holocene/Pleistocene boundary; an increased terrigenous deposition during Late...

  15. Nanoconfinement in activated mesoporous carbon of calcium borohydride for improved reversible hydrogen storage.

    Science.gov (United States)

    Comănescu, Cezar; Capurso, Giovanni; Maddalena, Amedeo

    2012-09-28

    Mesoporous carbon frameworks were synthesized using the soft-template method. Ca(BH(4))(2) was incorporated into activated mesoporous carbon by the incipient wetness method. The activation of mesoporous carbon was necessary to optimize the surface area and pore size. Thermal programmed absorption measurements showed that the confinement of this borohydride into carbon nanoscaffolds improved its reversible capacity (relative to the reactive portion) and performance of hydrogen storage compared to unsupported borohydride. Hydrogen release from the supported hydride started at a temperature as low as 100 °C and the dehydrogenation rate was fast compared to the bulk borohydride. In addition, the hydrogen pressure necessary to reg