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Sample records for calcium carbonate

  1. 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.

  2. 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 ...

  3. 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...

  4. 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)

  5. 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.

  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 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

  8. 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.

  9. 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

  10. 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...

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. [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.

  20. 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...

  1. 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

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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...

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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...

  19. 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.

  20. 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%.

  1. 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...

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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...

  7. 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)

  8. 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...

  9. 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.

  10. 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 

  11. 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...

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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...

  18. 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.

  19. 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.

  20. 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...

  1. 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

  2. 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).

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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)

  9. 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.

  10. [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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  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. 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.

  4. 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.

  5. 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.

  6. 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.

  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. 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

  9. 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...

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Studies on structure and organization of calcium carbonate deposits in algae

    Digital Repository Service at National Institute of Oceanography (India)

    Kerkar, V.; Untawale, A.G.

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

  3. 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...

  4. 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....

  5. 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 ...

  6. 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}.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  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. 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.

  15. 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.

  16. 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).

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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 ...

  3. 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 , ...

  4. 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...

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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...

  19. 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

  20. 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

  1. 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...

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. 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)

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  15. 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.

  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. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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 .

  9. 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...

  10. 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 ...

  11. 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 ...

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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...

  1. 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

  2. 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.

  3. 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

  4. 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.)

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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)

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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...

  14. 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.

  15. 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.

  16. 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 %.

  17. 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.

  18. 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}.

  19. 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.

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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...

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  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. 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.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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?.

  17. 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%.

  18. 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

    The deposition of sparingly soluble salts (scaling) within porous media is a major problem encountered in many industrial and environmental applications. In the oil industry scaling causes severe operational malfunctions and, therefore, increasing the total operating and maintenance cost [1]. The most common types of sparingly soluble salts located in oil fields include carbonate and sulfate salts of calcium, strondium and barium[1,2]. Multiple phase flow and tubing surface properties are some of the factors affecting scale formation [3]. The main purpose of the present work was the investigation of the precipitation mechanisms of calcium carbonate (CaCO3) through in situ mixing of two soluble salt solutions in a flow granular medium, in the presence of water miscible organic fluid (ethylene glycol) or non-miscible organic fluid (n-dodecane). All series of experiments were carried out in a two dimensional porous medium made of Plexiglas. For all solutions used in the experiments, the contact angles with the surface of the porous medium and the interfacial tensions were measured. During the experiments, the calcium carbonate crystal growth was continuously monitored and recorded through an optical microscope equipped with a digital programmed video camera. The snap-shots were taken within specific time intervals and their detailed procession gave information concerning the crystal growth rate and kinetics. The pH of the effluent was measured and fluids samples were collected for calcium analysis using Atomic Absorption Spectroscopy (AAS). In all experiments effluent calcium concentration decreased as a function of time, suggesting that CaCO3 precipitation took place inside the porous medium. Crystals of the precipitated salt were identified using Infrared Spectroscopy (IR) and the morphology of the crystals was examined using Scanning Electron Microscopy (SEM). The induction time for precipitation of CaCO3 crystals in the presence of n-dodecane was significantly

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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...

  8. 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…

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 脲解型微生物诱导碳酸钙沉积研究%Investigation on ureolytic microbiologically-induced calcium carbonate precipitation

    Institute of Scientific and Technical Information of China (English)

    徐晶; 杜雅莉; 白慧莉

    2016-01-01

    研究了钙源种类对脲解型微生物诱导碳酸钙沉积的生物-化学过程的影响。利用电位分析法实时测试了沉积过程中钙离子、铵离子及p H 值的变化,并利用显微计数对细菌浓度进行了监测。采用扫描电镜(SEM)、X射线衍射(XRD)和分析红外光谱(IR)对沉积产物进行了研究。结果表明,不同钙源环境下脲解型微生物诱导矿化沉积都存在化学沉淀、微生物诱导矿化沉积和沉淀完全3个阶段;有机钙源环境下细菌的产矿动力比在无机钙源中高,且两种钙源所获得的方解石晶体沉积物在形貌上差异显著。%The effects of calcium source type on the bio-chemical processes of ureolytic microbiologically-induced calcium carbonate precipitation was investigated in this paper.By using potentiometric analysis,calcium ions concentration,ammonium ions concentration,and pH value were measured.Cell density was also monitored by microscopic counting method.Sediments were characterized by scanning electron microscopy,X-ray diffraction, and infrared spectroscopy.The results showed that the processes of microbiologically-induced calcium carbonate precipitation consists the abiotic precipitation stage,the microbiologically-induced calcium carbonate precipitati-on stage,and the calcium ions depletion stage,regardless of the calcium source type.The efficiency of bacterial-ly-induce mineralized precipitation in organic calcium source environment is higher than that in inorganic calcium source environment.Significant morphological difference of precipitated calcites from two types of calcium sources was detected.

  17. 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 regenerate the borohydride from the dehydrogenation products was reduced.

  18. 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; 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...

  19. Optical planar waveguide in sodium-doped calcium barium niobate crystals by carbon ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jin-Hua, E-mail: zhaojinhuazjh@gmail.com [School of Science, Shandong Jianzhu University, Jinan 250101 (China); Qin, Xi-Feng; Wang, Feng-Xiang; Fu, Gang; Wang, Hui-Lin [School of Science, Shandong Jianzhu University, Jinan 250101 (China); Wang, Xue-Lin [School of Physics, Key Laboratory of Particle Physics and Particle Irradiation, Ministry of Education, and State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

    2013-07-15

    There is great interest in niobate crystals which belong to the tetragonal tungsten bronze (TTB) families owing to their intriguing properties. As one representative of such crystals, CBN (calcium barium niobate) has attracted rapidly growing attention. Because it has a higher Curie temperature than SBN (strontium barium niobate), possesses outstanding ferroelectric and it possesses optical properties. In addition, doped with sodium, CBN will show a higher Curie temperature than pure CBN. We report on the fabrication and characterization of optical planar waveguide in x-cut sodium-doped calcium barium niobate crystal by using C ion implantation. The guided-mode properties at the wavelength of 633 and 1539 nm are investigated through prism-coupling measurements, respectively. By applying direct end-face coupling arrangement, the near-field optical intensity distribution of waveguide modes is measured at 633 nm. For comparison, the modal profile of the same guided mode is also numerically calculated by the finite difference beam-propagation method via computer software BeamPROP. The transmission spectra of the waveguide before and after ion implantation treatments were investigated also. Our experiment results reveal that the waveguide could propagate light with transverse magnetic polarized direction only and it is assumed that the polarization selectivity of CBN crystal may responsible for this phenomenon.

  20. CRACK2 - Modelling calcium carbonate deposition from bicarbonate solution in cracks in concrete

    Energy Technology Data Exchange (ETDEWEB)

    Brodersen, K

    2003-03-01

    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 of the 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. The cementitious 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 migrating ions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack and on the composition of the outflowing solution, which can be compared directly with experimental results. Leaching behavior of sodium can be used to tune the model to experimental observations. The calcite is mostly precipitated on top of the original crack surface and may under certain circumstances fill the crack. The produced thin layers of low porosity calcite act as a diffusion barrier limiting contact between cement and solution. Pore closure mechanisms in such layers are discussed. Implications for safety assessment of radioactive waste disposal are shortly mentioned. The model is also relevant for conventional uses of concrete. (au)

  1. Enrichment of 88Sr in continental waters due to calcium carbonate precipitation

    Science.gov (United States)

    Shalev, Netta; Gavrieli, Ittai; Halicz, Ludwik; Sandler, Amir; Stein, Mordechai; Lazar, Boaz

    2017-02-01

    δ88/86Sr data published over the last few years suggest that continental waters are enriched with 88Sr as compared to the rocks in their drainage basins. In an attempt to understand this phenomenon, this study established the fractionation in the 88Sr/86Sr ratio during precipitation of continental carbonates (i.e., carbonates precipitated on land from surface, pedogenic, or ground waters), and evaluated the contribution of this process to the 88Sr-enrichment in rivers. For this, stable and radiogenic Sr isotopes (88Sr, 87Sr and 86Sr) were measured in calcite samples and their precipitating waters collected in various continental environments, such as soil, cave, streams and groundwater. The results indicate that continental carbonates are 88Sr-depleted relative to their precipitating waters, placing them as one of the most 88Sr-depleted reservoirs on earth. The average difference in δ88/86Sr values between waters and solid CaCO3 (tufas or speleothems) that they precipitate is Δcarb-water = - 0.218 ± 0.014 ‰ (1SD). An even larger fractionation (εcarb-water = - 0.285 ± 0.02 ‰) was measured in groundwater with particularly high carbonate-alkalinity and high carbonate precipitation rate that depleted ∼65% of the Sr in the groundwater, resulting in substantial 88Sr-enrichment in the residual dissolved Sr (δ88/86Sr = 0.656 ‰). Results also suggest that pedogenic carbonate precipitation in soil profile removes 50-85% of the Sr from the recharging soil-water, thereby increasing the δ88/86Sr value of the soil-water from ∼ 0.18 ‰ to 0.3 ‰- 0.6 ‰. Similar 88Sr-enrichment was observed in drip water from a karst cave. A maximum removal flux of Sr into continental carbonates of about 20 Gmol(Sr)ṡy-1 is required to yield the reported 88Sr-enrichment in global rivers (δ88/86Sr = 0.32 ‰) relative to their rock sources when using the fractionation factor derived in this study, Δcarb-water = - 0.218 ‰, and the published δ88/86Sr composition of marine

  2. Effects of lanthanum carbonate versus calcium carbonate on vascular stiffness and bone mineral metabolism in hemodialysis patients with type 2 diabetes mellitus: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Wada K

    2015-08-01

    Full Text Available Kentaro Wada,1 Yuko Wada,2 Haruhito Adam Uchida,3 Shuichi Tsuruoka4 1Division of Nephrology and Dialysis, Department of Internal Medicine, Nippon Kokan Fukuyama Hospital, Hiroshima, 2Department of Internal Medicine, Central Hospital, Hiroshima, 3Department of Chronic Kidney Disease and Cardiovascular Disease, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, 4Division of Nephrology, Department of Internal Medicine, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan Background: Vascular calcification contributes to cardiovascular disease in hemodialysis (HD patients with diabetes. The randomized controlled trial reported here compared the effects of lanthanum carbonate (LC and calcium carbonate (CC on vascular stiffness assessed using brachial-ankle pulse wave velocity (ba-PWV, intima-media thickness (IMT, bone mineral density (BMD, and serum markers of chronic kidney disease – mineral and bone disorder in such patients. Methods: Ba-PWV, IMT, BMD, and the biomarkers osteocalcin (OC and bone alkaline phosphatase (BAP were examined in 43 type 2 diabetes HD patients treated with LC (n=21 or CC (n=22 for 2 years. Results: Forty-one patients completed the study (19, LC; 22, CC. The mean ba-PWV significantly increased only in the CC group (median: 2,280.5 to 2,402.5 cm/s, P<0.05, after 24-month treatment; it remained unchanged in the LC group (median: 1,830.5 to 2,018.3 cm/s. However, the difference between the groups did not reach statistical significance. Changes in IMT and BMD were not different between the two groups. Changes in serum phosphorus, corrected calcium, and intact parathyroid hormone levels were similar between the groups. The incidence of fracture was 0% (0/19 in the LC group, and 13.6% (3/22 in the CC group (P=0.2478. The OC/BAP ratio increased significantly in the LC group (median: 0.83 to 2.47, compared with in the CC group (median: 0.77 to 1.40 (P=0.036. Conclusion: From

  3. Calcium carbonate precipitation by heterotrophic bacteria isolated from biofilms formed on deteriorated ignimbrite stones: influence of calcium on EPS production and biofilm formation by these isolates.

    Science.gov (United States)

    López-Moreno, Angélica; Sepúlveda-Sánchez, José David; Mercedes Alonso Guzmán, Elia Mercedes; Le Borgne, Sylvie

    2014-01-01

    Heterotrophic CaCO3-precipitating bacteria were isolated from biofilms on deteriorated ignimbrites, siliceous acidic rocks, from Morelia Cathedral (Mexico) and identified as Enterobacter cancerogenus (22e), Bacillus sp. (32a) and Bacillus subtilis (52g). In solid medium, 22e and 32a precipitated calcite and vaterite while 52g produced calcite. Urease activity was detected in these isolates and CaCO3 precipitation increased in the presence of urea in the liquid medium. In the presence of calcium, EPS production decreased in 22e and 32a and increased in 52g. Under laboratory conditions, ignimbrite colonization by these isolates only occurred in the presence of calcium and no CaCO3 was precipitated. Calcium may therefore be important for biofilm formation on stones. The importance of the type of stone, here a siliceous stone, on biological colonization is emphasized. This calcium effect has not been reported on calcareous materials. The importance of the effect of calcium on EPS production and biofilm formation is discussed in relation to other applications of CaCO3 precipitation by bacteria.

  4. Carbon nanotubes play an important role in the spatial arrangement of calcium deposits in hydrogels for bone regeneration.

    Science.gov (United States)

    Cancian, Giulia; Tozzi, Gianluca; Hussain, Amirul Ashraf Bin; De Mori, Arianna; Roldo, Marta

    2016-08-01

    Age related bone diseases such as osteoporosis are considered among the main causes of reduced bone mechanical stability and bone fractures. In order to restore both biological and mechanical function of diseased/fractured bones, novel bioactive scaffolds that mimic the bone structure are constantly under development in tissue engineering applications. Among the possible candidates, chitosan-based thermosensitive hydrogel scaffolds represent ideal systems due to their biocompatibility, biodegradability, enhanced antibacterial properties, promotion of osteoblast formation and ease of injection, which makes them suitable for less invasive surgical procedures. As a main drawback, these chitosan systems present poor mechanical performance that could not support load-bearing applications. In order to produce more mechanically-competent biomaterials, the combined addition of hydroxyapatite and carbon nanotubes (CNTs) is proposed in this study. Specifically, the aim of this work is to develop thermosensitive chitosan hydrogels containing stabilised single-walled and multi-walled CNTs, where their effect on the mechanical/physiochemical properties, calcium deposition patterns and ability to provide a platform for the controlled release of protein drugs was investigated. It was found that the addition of CNTs had a significant effect on the sol-gel transition time and significantly increased the resistance to compression for the hydrogels. Moreover, in vitro calcification studies revealed that CNTs played a major role in the spatial arrangements of newly formed calcium deposits in the composite materials studied, suggesting that they may have a role in the way the repair of fragile and/or fractured bones occurs in vivo.

  5. Application of calcium carbonate slows down organic amendments mineralization in reclaimed soils

    Science.gov (United States)

    Zornoza, Raúl; Faz, Ángel; Acosta, José A.; Martínez-Martínez, Silvia; Ángeles Muñoz, M.

    2014-05-01

    A field experiment was set up in Cartagena-La Unión Mining District, SE Spain, aimed at evaluating the short-term effects of pig slurry (PS) amendment alone and together with marble waste (MW) on organic matter mineralization, microbial activity and stabilization of heavy metals in two tailing ponds. These structures pose environmental risk owing to high metals contents, low organic matter and nutrients, and null vegetation. Carbon mineralization, exchangeable metals and microbiological properties were monitored during 67 days. The application of amendments led to a rapid decrease of exchangeable metals concentrations, except for Cu, with decreases up to 98%, 75% and 97% for Cd, Pb and Zn, respectively. The combined addition of MW+PS was the treatment with greater reduction in metals concentrations. The addition of PS caused a significant increase in respiration rates, although in MW+PS plots respiration was lower than in PS plots. The mineralised C from the pig slurry was low, approximately 25-30% and 4-12% for PS and MW+PS treatments, respectively. Soluble carbon (Csol), microbial biomass carbon (MBC) and β-galactosidase and β-glucosidase activities increased after the application of the organic amendment. However, after 3 days these parameters started a decreasing trend reaching similar values than control from approximately day 25 for Csol and MBC. The PS treatment promoted highest values in enzyme activities, which remained high upon time. Arylesterase activity increased in the MW+PS treatment. Thus, the remediation techniques used improved soil microbiological status and reduced metal availability. The combined application of PS+MW reduced the degradability of the organic compounds. Keywords: organic wastes, mine soils stabilization, carbon mineralization, microbial activity.

  6. Asymmetric hydration structure around calcium ion restricted in micropores fabricated in activated carbons

    Science.gov (United States)

    Ohkubo, Takahiro; Kusudo, Tomoko; Kuroda, Yasushige

    2016-11-01

    The adsorbed phase and hydration structure of an aqueous solution of Ca(NO3)2 restricted in micropores fabricated in activated carbons (ACs) having different average pore widths (0.63 and 1.1 nm) were investigated with the analysis of adsorption isotherms and x-ray absorption fine structure (XAFS) spectra on Ca K-edge. The adsorbed density of Ca2+ per unit micropore volume in the narrower pore was higher than in the wider pore, while the adsorbed amount per unit mass of carbon with the narrower pore was half of the amount of ACs with the larger pore. On the other hand, variations in the bands assigned to double-electron (KM I) and 1s  →  3d excitations in XAFS spectra demonstrate the formation of a distorted hydration cluster around Ca2+ in the micropore, although the structural parameters of hydrated Ca2+ in the micropores were almost consistent with the bulk aqueous solution, as revealed by the analysis of extended XAFS (EXAFS) spectra. In contrast to the hydration structure of monovalent ions such as Rb+, which generally presents a dehydrated structure in smaller than 1 nm micropores in ACs, the present study clearly explains that the non-spherically-symmetric structure of hydrated Ca2+ restricted in carbon micropores whose sizes are around 1 nm is experimentally revealed where any dehydration phenomena from the first hydration shell around Ca2+ could not be observed.

  7. Simulation on an aqueous solution of Calcium Carbonate%碳酸钙水溶液的模拟研究

    Institute of Scientific and Technical Information of China (English)

    游秀芬; 张雪峰; 游小嘉

    2012-01-01

    选取方解石水溶液和文石水溶液为研究对象,采用分子动力学方法,对构建的碳酸钙水溶液进行分子动力学模拟计算.计算结果表明:水分子的活性及渗透性随温度上升呈增大趋势,只有333 K温度下明显降低.方解石水溶液中Ca2+和CO32-的扩散系数随温度变化波动较大,文石水溶液中Ca2+和CO32-的扩散系数呈逐渐上升趋势.模拟得到的文石水溶液Ca2+-CO32-径向分布函数图和H2O径向分布函数图第一、二峰高度明显低于方解石水溶液.计算结果还显示离子与方解石晶面的相互作用能比文石晶面高0.02 kcal/mol.%In order to study the Calcium Carbonate crystallization, the aqueous solution of calcite and the aqueous solution of aragonite are treated as the research object by u-sing the Molecular dynamics simulate the Calcium Carbonate system. The conclusions are drew that the diffusion coefficient of water molecules increases ceaselessly with the increasing of the temperature and it's relatively small only when the temperature is 333 K. And it's also concluded that the diffusion coefficients of Ca2+ and COff in the a-queous solution of calcite vary relatively with the increasing of the temperature and those in the aqueous solution of aragonite increases ceaselessly. The radial distribution function graphs of Ca2+-CO?i~ and H2O the simulation has concluded display that the first and the second peak height is obviously lower than that of the aqueous solution of aragonite. Then it's calculated that the binding energy between the surface of calcite and 0. 02 kcal/mol higher than the surface of aragonite.

  8. 碳酸钙微米球的制备与表征%Preparation and characterization of calcium carbonate micro-spheres

    Institute of Scientific and Technical Information of China (English)

    陈先勇; 唐琴; 刘代俊

    2012-01-01

    采用醋酸钙和碳酸钠为原料,在反应温度为5℃和柠檬酸三钠质量百分浓度为15%的条件下,采用沉淀法合成出了粒度为1 ~4μm、分散性好的球形碳酸钙粉体.用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、红外光谱仪(IR)、原子力扫描探针显微镜(ASPM)、光学显微镜、粒度分析仪等对样品进行了表征,并用光学显微镜跟踪考察了碳酸钙微米球的形成过程.结果表明,碳酸钙微米球是由大量纳米级颗粒组装而成.%The uniform spherical calcium carbonate particles with granular size 1 ~4μm were prepared from a calcium acetate and sodium calcium solution at 5℃ by using precipitation method,and mass percent concentration of trisodium citrate 15%. The obtained CaCO, samples were characterized by means of Scanning electron microscope(SEM) ,X-ray diffraction( XRD) .Fourier transform infrared spectroscopy( FT-IR) .Atomic force scanning probe microscopy( ASPM) .Optical microscopy and Grain size analyzer. The formation process of calcium carbonate micro-spheres are observed though optical microscopy. The results showed that the calcium carbonate micro-spheres were assembled by a large number of nanometer particles.

  9. Are cyclopentadienylberyllium, magnesium and calcium hydrides carbon or metal acids in the gas phase?

    Science.gov (United States)

    Hurtado, Marcela; Lamsabhi, Al-Mokhtar; Mó, Otilia; Yáñez, Manuel; Guillemin, Jean-Claude

    2010-05-21

    The structure and bonding of cyclopentadienylberyllium (CpBeH), magnesium (CpMgH), and calcium (CpCaH) hydrides as well as those of their deprotonated species have been investigated by means of B3LYP/6-311+G(3df,2p)//B3LYP/6-311+G(d,p) and B3LYP/6-311+G(3df,2p)//QCISD/6-311+G(d,p) density functional theory (DFT) calculations. The three compounds exhibit C(5v) equilibrium conformations in their ground states. For CpBeH the agreement between the calculated geometry and that determined by MW spectroscopy is excellent. CpMgH and CpCaH can be viewed almost as the result of the interaction between a C₅H₅⁻ anion and a XH(+) (X = Mg, Ca) cation. Conversely, for CpBeH the interaction between the C₅H₅ and the BeH subunits is significantly covalent. These compounds exhibit a significant aromaticity, usually named three-dimension aromaticity, in contrast with the unsubstituted cyclopentadiene compound. The CpBeH derivative behaves as a C acid in the gas phase and is less acidic than cyclopentadiene. More importantly, CpMgH and CpCaH, in spite of the X(+δ)H(-δ) polarity exhibited by the X-H bond in the neutral systems, are predicted to be metal acids in the gas phase. Also surprisingly, both the Mg and the Ca derivatives are stronger acids than the Be analogue, and only slightly weaker acids than cyclopentadiene. This somewhat unexpected result is the consequence of two concomitant facts: the lower dissociation energy of the X-H (X = Mg, Ca) bonds with respect to the C-H bonds, and the significantly high electron affinity of the C₅H₅X* (X = Mg, Ca) radicals.

  10. Short time spreading and wetting of offset printing liquids on model calcium carbonate coating structures.

    Science.gov (United States)

    Koivula, Hanna; Toivakka, Martti; Gane, Patrick

    2012-03-01

    Spreading of oils and water on porous and pre-saturated model carbonate coating structures was studied with high speed video imaging. The short-time data were complemented with long time absorption and wicking experiments. The results indicate a strong dependence between surface structural features of the pigment tablets and water spreading at short times, both in non-saturated and water pre-saturated cases, while the oil spreading is mainly dependent on the liquid properties. Sodium polyacrylate dispersant on pigment surfaces is shown to contribute to water spreading and absorption. On pre-saturated structures the liquid-liquid interactions are dominant and the majority of results support spreading according to the molecular kinetic model. The evidence supports the hypothesis of S. Rousu, P. Gane, and D. Eklund, ["Influence of coating pigment chemistry and morphology on the chromatographic separation of offset ink constituents," in The Science of Papermaking Transactions of the 12th Fundamental Research Symposium, FRC The Pulp & Paper Fundamental Research Society, Oxford, UK, 2001, p. 1115] that at long times the oils absorb into the porous structure at a rate proportional to the ratio of viscosity and surface tension, provided there is no sorptive action with the binder. A combination of nanosized pores and large surface area is useful for providing sufficient absorption capability for carbonate based coatings.

  11. 碳酸钙颗粒的细菌诱导形成%The Formation of Calcium Carbonate Particles Induced by Bacteria

    Institute of Scientific and Technical Information of China (English)

    李辉; 连宾; 龚国洪; 杜开和

    2011-01-01

    In order to study whether Bacillus mucilaginosus can promote the formation of calcium carbonate or not under certain conditions, this research adopted two commonly used basic media of Bacillus mucilaginosus. The one is the nitrogen medium, and the other is the nitrogen-free medium. The apatite mineral was the sole source of calcium, and the B. mucilaginosus was grown in different media to synthesis calcium carbonate. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS)quantitative analysis, and X-ray diffraction (XRD) analysis were used to observe and study the crystal structure and chemical composition of the formed calcium carbonate. The results showed that B. mucilaginosus can accelerate formation of calcium carbonate. The crystals, calcium carbonate particles formed in the nitrogen medium containing apatite powders were more than those in the nitrogen-free medium containing apatite powders. Meanwhile, the columnar calcium carbonate crystals were observed in the nitrogen medium containing apatite powders. The mechanism for B. mucilaginosus to promote formation of calcium carbonate might be the secretion of carbonic anhydrase (CA) and dissolved CO2 in the process of apatite weathering and strong absorption features of bacteria.%为研究胶质芽孢杆菌(Bacillus mucilaginosus)在特定条件下能否诱导合成碳酸钙,作者采用胶质芽孢杆菌两种常用基本培养基(有氮培养基和无氮培养基),以磷灰石矿物为钙源,进行了利用胶质芽孢杆菌促进碳酸钙形成的实验,借助扫描电镜(SEM)、能谱定量分析(EDS)和X-射线衍射(XRD)等手段观察分析形成碳酸钙的晶体结构和化学组成.结果表明,胶质芽孢杆菌能促进碳酸钙晶体的形成,在有氮加磷矿粉的细菌培养液中形成的碳酸钙多于无氮加磷矿粉的细菌培养液,在有氮加磷矿粉的细菌培养液中观察到柱状碳酸钙的形成.作者认为,胶质芽孢杆菌通过其风化作用及较强的

  12. Crystal growth of calcium carbonate on the cellulose acetate/pyrrolidon blend films in the presence of L-aspartic acid

    Science.gov (United States)

    Zhang, Xiuzhen; Xie, Anjian; Huang, Fangzhi; Shen, Yuhua

    2014-03-01

    The morphogenesis and growth process of calcium carbonate on the cellulose acetate/polyvinyl pyrrolidone (CA/PVP) blend films in the presence of L-aspartic acid was carefully investigated. The results showed that the concentration of L-aspartic acid, the initial pH value of reaction solution and temperature turned out to be important factors for the control of morphologies and polymorphs of calcium carbonate. Complex morphologies of CaCO3 particles, such as cubes, rose-like spheres, twinborn-spheres, cone-like, bouquet-like, etc. could be obtained under the different experimental conditions. The dynamic process of formation of rose-like sphere crystals was analyzed by monitoring the continuous morphological and structural evolution and components of crystals in different crystal stages. This research may provide a promising method to prepare other inorganic materials with complex morphologies.

  13. Influence des ions étrangers et de la matière organique sur la cristallisation des carbonates de calcium Influence of Foreign Ions and of Organic Matter on the Crystallization of Calcium Carbonates

    Directory of Open Access Journals (Sweden)

    Cailleau P.

    2006-11-01

    Full Text Available On présente les résultats d'un travail de recherche entrepris pour des aspects de la diagenèse des roches carbonatées : la cimentation cal le rôle est capital pour la conservation ou le colmatage de la porosit de ce type de sédiments. Après une synthèse bibliographique des connaissances actuelles sur et la cimentation du CaC03 en milieu naturel et en laboratoire, on a mentalement l'influence des ions étrangers et de la matière organique sur germination et la croissance des carbonates de calcium. Les principaux résultats obtenus peuvent se résumer comme suit a En ce qui concerne les ions étrangers. Leur action se traduit en général par une augmentation du temps de germination et une réduction de la vitesse de croissance des cristaux de CaCO3; l'apparition de faciès particuliers pour certains des minéraux formés ; l'inhibition des transformations d'une variété en une autre. On obtient un classement par ordre d'efficacité croissante action à peu près nulle: K+, CI-; action modérée : Bat+, Na+, AI3+, Cul+, Sr2+, SO2 , P0;-; action dominante de Mg'+. b Pour les matières organiques. Seules l'acide citrique et, dans une moindre mesure, l'acide tartrique, ont une influence notable, d'ailleurs analogue à celle des ions étrangers en ce qui concerne les cinétiques de germination et de croissance du CaCO. L'adsorption de certains de ces produits se traduit en outre par des faciès particuliers des minéraux formés et éventuellement par l'inhibition des transformations d'une variété en une autre. This article gives the results of a research project undertaken to study one of the aspects of the diagénesis of carbonate rocks, 1. e. calcite cementing, which plays a capital role in preserving or plugging up the original porosity of such sediments.After making a bibliographic synthesis of what is now known about the origin and cementation of CaC03 in a natural environment and in the laboratory, the article experimentally

  14. Influence of precipitated calcium carbonate (CaCO3) on shiitake (Lentinula edodes) yield and mushroom size.

    Science.gov (United States)

    Royse, Daniel J; Sanchez-Vazquez, Jose E

    2003-11-01

    Synthetic substrate consisting of oak sawdust (50%), white millet (28%), winter rye (11%) and soft red wheat bran (11%) was non-supplemented or supplemented with 0.2%, 0.4% or 0.6% (dry weight basis) precipitated calcium carbonate (CaCO(3)). Shiitake (Lentinula edodes) was grown in two crops to determine the effect of three CaCO(3) levels on mushroom yield and size. Yields and biological efficiencies (averages for two crops) from substrates non-supplemented with CaCO(3) were lower by 14.1%, 18.4% and 24.9% compared to treatments supplemented with 0.2%, 0.4% and 0.6% CaCO(3), respectively. Mushroom size (weight) was larger with non-supplemented substrate (16.8 g) compared to substrate supplemented with 0.6% CaCO(3) (15.1 g). However, mushroom production was more consistent from crop to crop when 0.6% CaCO(3) was added to substrate.

  15. Preparation of Calcium Carbonate Nanoparticles with a Continuous Gas-liquid Membrane Contactor:Particles Morphology and Membrane Fouling

    Institute of Scientific and Technical Information of China (English)

    JIA Zhiqian; CHANG Qing; QIN Jin; MAMAT Aynur

    2013-01-01

    Nanosized calcium carbonate particles were prepared with a continuous gas-liquid membrane contactor.The effects of Ca(OH)2 concentration,CO2 pressure and liquid flow velocity on the particles morphology,pressure drop and membrane fouling were studied.With rising Ca(OH)2 concentrations,the average size of the particles increased.The effects of Ca(OH)2 concentration and CO2 pressure on particles were not apparent under the experimental conditions.When the Ca(OH)2 concentration and liquid flow velocity were high,or the CO2 pressure was low,the fouling on the membrane external surface at the contactor entrance was serious due to liquid leakage,whereas the fouling was slight at exit.The fouling on the membrane inner-surface at entrance was apparent due to adsorption of raw materials.The membrane can be recovered by washing with dilute hydrochloric acid and reused for at least 6 times without performance deterioration.

  16. Ciprofloxacin HCl-loaded calcium carbonate nanoparticles: preparation, solid state characterization, and evaluation of antimicrobial effect against Staphylococcus aureus.

    Science.gov (United States)

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

    2017-05-01

    Ciprofloxacin HCl-loaded calcium carbonate (CaCO3) nanoparticles were prepared via a w/o microemulsion method and characterized by dynamic light scattering, scanning electron microscopy, X-ray powder diffraction (XRPD) analysis, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The in vitro drug release profiles as well as antimicrobial effect against Staphylococcus aureus (S. aureus) were also evaluated. The antibacterial effect was studied using serial dilution technique to determine the minimum inhibitory concentration (MIC) of the nanoparticles and was confirmed by streak cultures. The mean particle size, drug loading and entrapment efficiency were calculated to be 116.09 nm, 20.49% and 44.05%, respectively. PXRD and FTIR studies confirmed that both vaterite and calcite polymorphs of CaCO3 were formed during the preparation process. In vitro release profiles of the nanoparticles showed slow release pattern for 12 h. The drug-loaded nanoparticles showed similar MICs against S. aureus compared to untreated drug. However, a preserved antimicrobial effect was observed for drug-loaded nanoparticles compared to untreated drug after 2 days of incubation.

  17. Direct electrochemistry of horseradish peroxidase immobilized on the layered calcium carbonate-gold nanoparticles inorganic hybrid composite.

    Science.gov (United States)

    Li, Feng; Feng, Yan; Wang, Zhen; Yang, Limin; Zhuo, Linhai; Tang, Bo

    2010-06-15

    A mediator-free hydrogen peroxide (H(2)O(2)) biosensor was fabricated based on immobilization of horseradish peroxidase (HRP) on layered calcium carbonate-gold nanoparticles (CaCO(3)-AuNPs) inorganic hybrid composite. The proposed biosensor showed a strong electrocatalytic activity toward the reduction of H(2)O(2), which could be attributed to the favored orientation of HRP in the well-confined surface as well as the high electrical conductivity of the resulting CaCO(3)-AuNPs inorganic hybrid composite. The hybrid composite was obtained by the adsorption of AuNPs onto the surfaces of layered CaCO(3) through electrostatic interaction. The key analytical parameters relative to the biosensor performance such as pH and applied potential were optimized. The developed biosensor also exhibited a fast amperometric response (3s), a good linear response toward H(2)O(2) over a wide range of concentration from 5.0x10(-7) to 5.2x10(-3)M, and a low detection limit of 1.0x10(-7)M. The facile, inexpensive and reliable sensing platform based on layered CaCO(3)-AuNPs inorganic hybrid composite should hold a huge potential for the fabrication of more other biosensors.

  18. Effect of calcium carbonate on cadmium and nutrients uptake in tobacco (Nicotiana tabacum L.) planted on contaminated soil.

    Science.gov (United States)

    Zeng, Wei-Ai; Li, Fan; Zhou, Hang; Qin, Xiao-Li; Zou, Zi-Jin; Tian, Tao; Zeng, Min; Liao, Bo-Han

    2016-01-01

    In the present study, calcium carbonate (CaCO3) was applied to Cd-contaminated soil at rates of 0, 0.5 and 1.0 g kg(-1). The effect of CaCO3 on soil pH, organic matter, available Cd, exchangeable Cd and level of major nutrients in a tobacco field and on accumulation of various elements in tobacco plants was determined. The results showed that CaCO3 application significantly increased the pH level, available P and exchangeable Ca but decreased organic matter, available Cd, exchangeable Cd, available heavy metals (Fe, Mn, Zn and Cu) and available K in soil. Additionally, CaCO3 application substantially reduced Cd accumulation in tobacco roots, stems, upper leaves, middle leaves and lower leaves, with maximum decrease of 22.3%, 32.1%, 24.5%, 22.0% and 18.2%, respectively. There were large increase in total Ca and slight increases in total N and K but decrease to varying degrees in total Fe, Cu and Zn due to CaCO3 application. CaCO3 had little effect on total P and Mn levels in tobacco leaves.

  19. A promising lightweight multicomponent microwave absorber based on doped barium hexaferrite/calcium titanate/multiwalled carbon nanotubes

    Science.gov (United States)

    Afghahi, Seyyed Salman Seyyed; Jafarian, Mojtaba; Atassi, Yomen

    2016-07-01

    We present the design of a microwave absorber in the X band based on ternary nanocomposite of doped barium hexaferrite (Ba-M)/calcium titanate (CTO)/multiwall carbon nanotubes (MWCNTs) in epoxy matrix. The hydrothermal method has been used to synthesize Ba-M and CTO nanopowder. The phase identification has been investigated using XRD patterns. Scanning electron microscope, transmission electron microscope, vibrating sample magnetometer, and vector network analyzer are used to analyze the morphology of the different components and the magnetic, electromagnetic, and microwave absorption properties of the final composite absorbers, respectively. As far as we know, the design of this type of multicomponent microwave absorber has not been investigated before. The results reveal that the combination of these three components with their different loss mechanisms has a synergistic effect that enhances the attenuation properties of the final composite. The absorber of only 2.5-mm thickness and 35 wt% of loading ratio exhibits a minimum reflection loss of -43 dB at 10.2 GHz with a bandwidth of 3.6 GHz, while the corresponding absorber based on pure (Ba-M) shows a minimum reflection loss of -34 dB at 9.8 GHz with a bandwidth of 0.256 GHz and a thickness of 4 mm.

  20. Neutron and X-ray diffraction and empirical potential structure refinement modelling of magnesium stabilised amorphous calcium carbonate

    DEFF Research Database (Denmark)

    Cobourne, G.; Mountjoy, G.; Rodriguez Blanco, Juan Diego

    2014-01-01

    from CO3 molecules and 0.6 oxygen atoms from H2O molecules. The average CaO bond length is 2.40 Å. The distribution of Ca in the model is homogeneous with a uniformly distributed Ca-rich network and no evidence of the Ca-poor channels as previously reported for a reverse Monte Carlo model of ACC......Amorphous calcium carbonate (ACC) plays a key role in biomineralisation processes in sea organisms. Neutron and X-ray diffraction have been performed for a sample of magnesium-stabilised ACC, which was prepared with a Mg:Ca ratio of 0.05:1 and 0.25 H2O molecules per molecule of CO3. The empirical...... potential structure refinement method has been used to make a model of magnesium-stabilised ACC and the results revealed a fair agreement with the experimental diffraction data. The model has well-defined CO3 and H2O molecules. The average coordination number of Ca is 7.4 and is composed of 6.8 oxygen atoms...

  1. Review of the extrinsic stain removal and enamel/dentine abrasion by a calcium carbonate and perlite containing whitening toothpaste.

    Science.gov (United States)

    Joiner, Andrew

    2006-08-01

    There has been an increase in the demand from consumers and patients for products that whiten teeth. To meet this demand, a whitening toothpaste containing calcium carbonate and perlite as the abrasive system and an efficacious fluoride source has recently been launched. The aim of the current paper is to review the toothpaste's stain removal efficacy and its effects on enamel and dentine wear. It has been shown to be effective at removing model extrinsic stain in vitro. Further, it has been shown to be more effective in removing naturally occurring extrinsic tooth stain than a silica non-whitening control toothpaste after two weeks of twice daily brushing in a parallel group, double-blind clinical study using 152 adult volunteers. In addition, the enhanced whitening effect did not give a clinically relevant level of wear to enamel or a significant increase in dentine wear compared to marketed non-whitening toothpaste formulations, as shown by using an in situ type model with ex vivo brushing.

  2. Evaluation of strength-enhancing factors of a ductile binder in direct compression of sodium bicarbonate and calcium carbonate powders.

    Science.gov (United States)

    Mattsson, S; Nyström, C

    2000-03-01

    This study evaluated the effectiveness of a ductile binder in direct compression of sodium bicarbonate and calcium carbonate powders. Properties associated with both the binder and the compound were studied. The addition of binder materials, such as polyethylene glycols (PEGs) of differing molecular weights or microcrystalline cellulose, generally resulted in an increase in the axial tensile strength of the corresponding compacts. The increase in tablet strength was generally greater with the PEGs than with microcrystalline cellulose. The results indicate that the improvement in tablet strength caused by the binder is dependent on properties of both the binder and the compound. By utilising different methods it was established that the fracture during tablet strength testing mainly occurred around the compound particles. As a consequence of this, it appears that the ability of the binder to fill the voids between the compound particles is a determinative factor for increasing tablet strength. The binder appeared to have less effect when added to compounds that fragmented during compaction. Characteristics of the binder resulting in the greatest decrease in porosity, and thus the greatest increase in the tensile strength of the compound, included a high degree of plastic deformation with a limited elastic component and a small particle size. Obviously, the amount of binder added to the mixture also affected the results.

  3. The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

    Science.gov (United States)

    Zheng, Liping; Wang, Ying; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie; Guo, Jia

    Calcium carbide (CaC 2)-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N 2 sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g -1 measured by cyclic voltammetry at 1 mV s -1. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles.

  4. The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Liping; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie [School of Chemistry, Key Laboratory of Environmentally Friendly Chemistry and Applications of Minister of Education, Xiangtan University, Hunan 411105 (China); Wang, Ying; Guo, Jia [School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Hubei 430073 (China)

    2010-03-15

    Calcium carbide (CaC{sub 2})-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N{sub 2} sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g{sup -1} measured by cyclic voltammetry at 1 mV s{sup -1}. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles. (author)

  5. Development and characterization of a novel bioresorbable and bioactive biomaterial based on polyvinyl acetate, calcium carbonate and coralline hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Javier Aragón

    2011-03-01

    Full Text Available Coralina® HAP-200 (coralline hydroxyapatite obtained by hydrothermal treatment of marine corals and POVIAC® (polymeric matrix based on PVAc, commercial trade marks were mixed with a natural product from the Cuban sea costs, i.e. calcium carbonate from Porites Porites coral, to obtain a novel bioactive composite with potential use as bone restoration material. The samples were characterized by physical-chemical (FTIR, XRD, SEM, EDS and mechanical studies. It was shown that there is no chemical interaction between the inorganic filler and the polymer matrix, each conserving the original properties of the raw materials. The studied formulation had a compressive strength similar to that reported for trabecular bone. Scanning electron microscopy examination revealed that the addition of CaCO3 induces a change on the morphologic structure of the composite obtained after 30 days of SBF immersion. These composites generate novel biomaterials capable of promoting the deposition of a new phase, a Ca-P layer due to the bioactivity of a Ca2+ precursors.

  6. Influence of Calcium Carbonate Fillers on the Properties of Recycled Poly(e-caprolactone Based Thermoplastic Polyurethane

    Directory of Open Access Journals (Sweden)

    Vitalija BETINGYTĖ

    2012-09-01

    Full Text Available In this work the effects of different crystallographic modifications of calcium carbonate (CaCO3 filler on the melt flow, mechanical properties, hydrolytic degradation, and shape memory behaviour of recycled low-temperature poly(e-caprolactone-based polyurethane (rTPU were evaluated. Composites were prepared by two-roll milling varying filler content from 2 wt % to 6 wt %. It was found that at temperature range from 20 °C to 50 °C CaCO3 fillers do not change Young’s modulus, they decrease tensile stress and deformation of rTPU, but improve its mechanical properties at elevated temperatures (up to 65 °C. rTPU melt flow index increases due to chain scission during the recycling and filler mixing with mill. Therefore, destruction temperature of rTPU is 20 °C lower than that of TPU. The CaCO3 does not change shape memory properties independently of filler type and transition from secondary shape to the primary shape at 70 °C temperature is completed within 17 s for both filled and unfilled rTPU. The investigation of hydrolytic degradation shows that CaCO3 only slightly increases degradation rate of rTPU.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2433

  7. Preparation and investigation of polylactic acid, calcium carbonate and polyvinylalcohol nanofibrous scaffolds for osteogenic differentiation of mesenchymal stem cells

    Directory of Open Access Journals (Sweden)

    A. Doustgani

    2016-04-01

    Full Text Available Objective(s: In this study, the effect of electrospun fiber orientation on proliferation and differentiation of mesenchymal stem cells (MSCs was evaluated. Materials and Methods: Aligned and random nanocomposite nanofibrous scaffolds were electrospun from polylactic acid (PLA, poly (vinyl alcohol (PVA and calcium carbonate nanoparticles (nCaP. The surface morphology of prepared nanofibrous scaffolds with and without cell was examined using scanning electron microscopy. Mechanical properties of electrospun nanofibrous scaffolds were determined with a  universal testing machine. The in vitro properties of fabricated scaffolds was also investigated by the MTT assay and alkaline phosphatase activity (ALP.Results: The average fiber diameter for aligned and random nanofibers were 82 ± 12 nm and 124 ± 25 nm, respectively. The mechanical testing indicated the higher tensile strength and elastic modulus of aligned nanofibers. MTT and ALP results showed that alignment of nanofiber increased the osteogenic differentiation of stem cells.Conclusion: Aligned nanofibrous nanocomposite scaffolds of PLA/nCaP/PVA could be an excellent substrate for MSCs and represents a potential bone-filling material.

  8. Influence of Sticky Rice and Anionic Polyacrylamide on the Crystallization of Calcium Carbonate in Chinese Organic Sanhetu

    Science.gov (United States)

    Liu, Hui; Peng, Changsheng; Dai, Min; Gu, Qingbao; Song, Shaoxian

    2015-09-01

    The crystallization of calcium carbonate (CaCO3) in soil controlled by natural organic material was considered a very important reason to enhance the property of ancient Chinese organic Sanhetu (COS), but how the organic material affected the crystallization of CaCO3 in COS is still unclear. In this paper, a natural organic material (sticky rice, SR) and a synthetic organic material (anionic polyacrylamide, APAM) were selected as additives to investigate their effect on the crystallization of CaCO3. The experimental results showed that the morphology and size of CaCO3 crystals could be affected by the concentration of additives and reaction time, while only the size of CaCO3 crystals could be affected by the concentration of reactant. Although the morphology and size of CaCO3 crystals varied greatly with the variation of additive concentration, reactant concentration and reaction time, the polymorph of CaCO3 crystals were always calcite, according to SEM/EDX, XRD and FTIR analyses. This study may help us to better understand the mechanism of the influence of organic materials on CaCO3 crystallization and properties of COS.

  9. Real-time monitoring of calcium carbonate and cationic peptide deposition on carboxylate-SAM using a microfluidic SAW biosensor

    Directory of Open Access Journals (Sweden)

    Anna Pohl

    2014-10-01

    Full Text Available A microfluidic biosensor with surface acoustic wave technology was used in this study to monitor the interaction of calcium carbonate with standard carboxylate self-assembled monolayer sensor chips. Different fluids, with and without biomolecular components, were investigated. The pH-dependent surface interactions of two bio-inspired cationic peptides, AS8 and ES9, which are similar to an extracellular domain of the chitin synthase involved in mollusc shell formation, were also investigated in a biological buffer system. A range of experimental conditions are described that are suitable to study non-covalent molecular interactions in the presence of ionic substances, such as, mineral precursors below the solubility equilibrium. The peptide ES9, equal to the mollusc chitin synthase epitope, is less sensitive to changes in pH than its counterpart AS8 with a penta-lysine core, which lacks the flanking acidic residues. This study demonstrates the extraordinary potential of microfluidic surface acoustic wave biosensors to significantly expand our experimental capabilities for studying the principles underlying biomineralization in vitro.

  10. The preparation and crystal types of precipitated Calcium Carbonate%沉淀碳酸钙的制备与晶型

    Institute of Scientific and Technical Information of China (English)

    方卫民

    2000-01-01

      This review introduces the basic principle and the preparation method of a series of crystal types that calcium carbonate is precipitated and discusses various factors for control particle size.%  本文介绍了生产沉淀CaCO3的基本原理和各种晶型的制备方法控制粒径大小的因素。

  11. COMPARATIVE EVALUATION OF IMMEDIATE EFFICACY OF DIODE LASER VERSUS DESENSITIZING PASTE CONTAINING 8% ARGININE AND CALCIUM CARBONATE IN TREATMENT OF DENTINE HYPERSENSITIVITY: AN IN VIVO STUDY

    Directory of Open Access Journals (Sweden)

    Anisha

    2015-03-01

    Full Text Available BACKGROUND & OBJECTIVES: The aim of the study was to evaluate the immediate efficacy of diode laser versus desensitizing paste containing 8% arginine and calcium carbonate in the treatment of dentine hypersensitivity. MET HODOLOGY: 50 patients with complain of tooth hypersensitivity were randomly selected for an 8 week clinical trial with the set inclusion and exclusion criteria. Each patient was assigned to one of the two study groups: Group 1 ( n=25 - 8% arginine and calcium carbonate paste (Pro - Relief paste , Colgate - Palmolive Ltd , India and Group 2 (n=25 - Diode laser(AMD , Picasso Diode , Indianapolis , Indiana , who received a baseline evaluation of tactile hypersensitivity with the help of dental explorer and an air blast hypersensitivity. The effectiveness of the therapy was assessed by VAS Scale of 10 , along with the hard and soft tissue evaluation , at 4 examination periods: 1 immediately after the application of the diode laser 2 after 15 days 3 after 4 weeks & 4 after 8 weeks. RESULTS: 8% arginine and calcium carbonate showed significant results (67.27% than diode laser (56.55% at immediate and 4 weeks evaluation by mechanical stimulus and immediate evaluation by air stimulus. Diode laser showed highly signi ficant results in progressive decrease in the dentin hypersensitivity till 8 weeks whereas 8% arginine showed highly significant results till 4 weeks. CONCLUSION : The immediate efficacy of 8% arginine and calcium carbonate (Colgate Pro Relief was higher a s compared to diode laser. Diode laser showed progressive reduction till 8 weeks whereas Colgate Pro Relief showed progressive reduction only till 4 weeks

  12. Influence of proton pump inhibitors and histamine H2 receptor antagonists on serum phosphorus level control by calcium carbonate in patients undergoing hemodialysis: a retrospective medical chart review

    OpenAIRE

    Tatsuzawa, Masaomi; Ogawa, Ryuichi; OHKUBO, Atsushi; Shimojima, Kazuyo; Maeda, Kunimi; Echizen, Hirotoshi; Miyazaki, Akihisa

    2016-01-01

    Background Hyperphosphatemia is one of the common complications in patients undergoing hemodialysis. Although calcium carbonate (CaC) is often used to control serum inorganic phosphorus level in dialysis patients, co-administration of gastric acid reducers (ARs) may interfere with the phosphate binding effect of CaC. We performed a retrospective medical chart review to study whether ARs attenuate the hypophosphatemic effect of CaC in patients undergoing hemodialysis. Methods One hundred and e...

  13. [INDICES OF THE OXIDATIVE STATUS IN CHRONIC ADMINISTRATION OF COLLOID CARBONATE CALCIUM PRAPARATION WITH FAUCET AND LOW-MINERALIZED DRINKING WATER IN RATS].

    Science.gov (United States)

    Khripach, L V; Mikhaylova, R I; Koganova, Z I; Knyazeva, T D; Alekseeva, A V; Savostikova, O N; Ryzhova, I N; Kruglova, E V; Revzova, T L

    2015-01-01

    There are discussed the changes of an array of indices of the oxidative status in chronic administration of colloidal calcium carbonate preparation with faucet and low-mineralized drinking water to rats. Slight differences between significant effects of administration of 3 and 30 mg/L of preparation permit to suggest that the process of its incoming delivery into organism of rats has a bottleneck in the nature of total capacity of macrophages of intestinal lymphoid tissue to absorption of particles.

  14. The calcium carbonate saturation state in cyanobacterial mats throughout Earth’s history

    Science.gov (United States)

    Aloisi, Giovanni

    2008-12-01

    Through early lithification, cyanobacterial mats produced vast amounts of CaCO 3 on Precambrian carbonate platforms (before 540 Myr ago). The superposition of lithified cyanobacterial mats forms internally laminated, macroscopic structures known as stromatolites. Similar structures can be important constituents of Phanerozoic carbonate platforms (540 Myr to present). Early lithification in modern marine cyanobacterial mats is thought to be driven by a metabolically-induced increase of the CaCO 3 saturation state ( Ω) in the mat. However, it is uncertain which microbial processes produce the Ω increase and to which extent similar Ω shifts were possible in Precambrian oceans whose chemistry differed from that of the modern ocean. I developed a numerical model that calculates Ω in cyanobacterial mats and used it to tackle these questions. The model is first applied to simulate Ω in modern calcifying cyanobacterial mats forming at Highborne Cay (Bahamas); it shows that while cyanobacterial photosynthesis increases Ω considerably, sulphate reduction has a small and opposite effect on mat Ω because it is coupled to H 2S oxidation with O 2 which produces acidity. Numerical experiments show that the magnitude of the Ω increase is proportional to DIC in DIC-limited waters (DIC concentration of Ca 2+ in ambient waters. With oceanic Ca 2+ concentrations greater than a few millimolar, an appreciable increase in Ω occurs in mats under a wide range of environmental conditions, including those supposed to exist in the oceans of the past 2.8 Gyr. The likely lithological expression is the formation of the microsparitic stromatolite microtexture—indicative of CaCO 3 precipitation within the mats under the control of microbial activity—which is found in carbonate rocks spanning from the Precambrian to recent. The model highlights the potential for an increase in the magnitude of the Ω shift in cyanobacterial mats throughout Earth's history produced by a decrease in

  15. Determination of calcium ion in sap using carbon nanotube-based ion-selective electrodes.

    Science.gov (United States)

    Hernández, Rafael; Riu, Jordi; Rius, F Xavier

    2010-08-01

    A new reduced-size solid-state electrode using carbon nanotubes as the transducing layer has been developed for the direct determination of Ca(2+) in sap, overcoming problems encountered by commercial ISEs analysing real complex samples. We show that this solid-contact ISE, which can be easily miniaturized, can be used directly in diluted real samples without any other pretreatment. The performance parameters of the new ISE include a Nernstian slope and excellent stability, good coefficients of selectivity, range of linearity (10(-5) to 10(-2.5) M) and limit of detection (10(-6.2) M), thus making it an excellent tool for determining Ca(2+) in a wide range of plant species.

  16. Calcium carbonate crystallizations on hypogean mural paintings: a pilot study of monitoring and diagnostics in Roman catacombs

    Science.gov (United States)

    Tapete, D.; Fratini, F.; Mazzei, B.; Camaiti, M.; Cantisani, E.; Riminesi, C.; Manganelli Del Fà, R.; Cuzman, O.; Tiano, P.

    2012-04-01

    One of the deterioration processes affecting mural paintings and rock surfaces within manmade hypogea consists in the formation of calcium carbonate crystallizations, which can create thick coverage and incrustations, even in some cases speleothems. These chemical reactions necessarily require the availability of calcium sources, which can be also of anthropogenic origin (e.g., lime-based mortars). Microclimate parameters also represent environmental forcing factors, on which the morphology and the degree of crystallinity of the precipitated carbonates depend. Understanding past/recent dynamics of carbonate precipitation implies a deep knowledge of the relationships between the exposed surfaces and the microclimate conditions, the impacts of external factors (e.g., groundwater infiltration and percolation from the overlying soil) and how they change over time. This is particularly fundamental for the preservation of hypogean sites which have not comparison with other typologies of environment due to their uniqueness, such as the ancient catacombs carved underneath the suburbs of Rome (Italy), since the 2nd century AD. In this paper we present the multidisciplinary methodological approach designed for the instrumental monitoring of the microphysical environment of the Catacombs of Saints Mark, Marcellian and Damasus, in the framework of the co-operation between the Institute for the Conservation and Valorization of Cultural Heritage and Pontifical Commission for Sacred Archaeology, Vatican, on the project HYPOGEA. Temperature inside the catacomb and on the surfaces, air relative humidity and CO2 concentration are the main of the parameters continuously measured by means of data loggers installed within the cubicles. Contemporarily, standardized methods of photographic documentation and digital micro-photogrammetry are used for change detection analysis of the painted surfaces and ancient plasters, as well as of the test areas purposely realized by applying fresh

  17. The preparation of porous superfine calcium carbonate microspheres%多孔超细碳酸钙微球的制备

    Institute of Scientific and Technical Information of China (English)

    杨辉; 李欢

    2013-01-01

    采用乳状液膜与共沉淀结合法制备多孔超细碳酸钙微球,考察了不同反应条件对碳酸钙微球形貌的影响.通过X射线衍射、扫描电子显微镜及激光粒度仪对所得的碳酸钙微球的晶体组成、形貌以及粒度进行了表征.结果表明,超细碳酸钙微球生成的最佳工艺条件为:CaCl2溶液浓度0.1 mol/L、吐温-80加量4 mL、超声乳化5 min、搅拌反应3 h ,此工艺条件下获得多孔碳酸钙微球粒径在2~10μm ,球形圆整,且组成为球霰石与方解石的共混体.%The porous superfine calcium carbonate microspheres was prepared by using a e-mulsion liquid membrane method combining with a precipitation method in this paper . Effects of different reaction conditions on the calcium carbonate microspheres morphology were investigated ,and finally the crystal composition ,morphology and particle size of the obtained calcium carbonate were characterized through X-ray diffraction (XRD) ,scanning e-lectron microscope(SEM ) and laser particle size instrument .The results showed that the op-timal conditions for porous superfine calcium carbonate microspheres are as follow s :the so-lution concentration of CaCl2 was 0 .15 mol/L ,the amount of Tween-80 used in preparation was 4 mL ,the time of ultrasonic emulsification was 5 min ,the reaction time with stirring was 3 h .Under these conditions ,the particle size of porous superfine calcium carbonate ranged from 2 to 10 μm ,round ,and composed of the vaterite and calcite .

  18. Subchronic pulmonary toxicity of nano-sized calcium carbonate in rats%纳米碳酸钙对大鼠亚慢性肺毒性作用

    Institute of Scientific and Technical Information of China (English)

    仇玉兰; 宋秋坤; 王慧; 刘凤琴; 贺连平; 张永雷; 梁艳芳

    2011-01-01

    目的 初步探讨纳米碳酸钙亚慢性染毒对大鼠肺毒性作用.方法 将32只雄性Wistar大鼠按体重随机分为4组,分别为阴性对照组(生理盐水)、低(0.8 mg/InL)、中(4.0 mg/mL)、高(20.0 mg/mL)剂量纳米碳酸钙组,用气管注入法进行染毒,每周染毒1次,连续5周.分别对肺泡灌洗液中乳酸脱氢酶(LDH)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)含量和肺组织匀浆中超氧化物歧化酶(SOD)和丙二醛(MDA)含量进行测定,并进行肺病理组织学观察.结果 高剂量组与对照组LDH含量分别为(1 427.808±577.792)和(733.151±463.907)u/L,差异有统计学意义(P=0.046);高、中剂量组ACP含量分别为(42.605±17.778)和(39.868±11.233)U/L,均高于对照组(15.397±10.234)U/L,差异均有统计学意义(P<0.05);与对照组比较,肺泡灌洗液中AKP含量以及各剂量组肺组织中SOD和MDA含量差异均无统计学意义(P>0.05);病理组织学观察发现染毒组大鼠支气管和肺泡均有不同程度损伤,淋巴细胞、中性粒细胞浸润,间质纤维细胞增生等.结论 纳米碳酸钙具有一定的肺毒性作用.%Objective To explore subchronic pulmonary toxicity of nano-sized calcium carbonate in rats.Methods Thirty-two male rats were randomly divided into negative control group and three experimental groups exposed to 0.8,4, and 20mg/ml nano-sized calcium carbonate.The rats were instilled with physiological saline and different doses nano-sized calcium carbonate once a week for five weeks through tracheal injection method.The indices in bronchoalveolar lavage fluid (BALF) and lung tissue were determined, including lactate dehydrogenase( LDH), alkaline phosphatase (AKP), acid phosphatase( ACP ), superoxide dismutase (SOD), and malonaldehyde (MDA).The pathological changes in the lung of the rars were also observed.Results The level of LDH in 20mg/ml nano-sized calcium carbonate group, ACP in 4,20 mg/ml nano-sized calcium carbonate group were all nigher than

  19. Study on Fixation of CO2 and Production of Precipitated Calcium Carbonate Using Steel Slag%利用钢渣固结CO2制备沉淀碳酸钙的试验研究

    Institute of Scientific and Technical Information of China (English)

    朱蓓蓉; 杨全兵

    2011-01-01

    The possibility of fixation of CO2 and production of precipitated calcium carbonate by carbonating acetate solution of calcium extracted from steel slag was investigated. The composition of precipitate produced after carbonation was then analyzed with XRD and TG-DTA. The results show that calcium acetate must be converted into calcium hydroxide by adding sodium hydroxide into calcium acetate solution and then precipitated calcium carbonate can be produced by carbonating the solution. Acetate solution of calcium extracted from steel slag can be carbonated by adding enough sodium hydroxide but the purity of precipitated calcium carbonate produced is only about 60% and the conversion of calcium is only about 35. 00%. To improve the effect of carbonation and to produce precipitated calcium carbonate with a high purity, other ions dissolved in steel slag should be removed from acetate solution of calcium extracted from steel slag.%研究了基于醋酸提取钢渣中钙离子所获得的醋酸钙溶液碳化固结CO2并制备沉淀碳酸钙的可行性,借助于XRD,TG-DTA对碳化后生成的沉淀物进行了成分分析和综合热分析.结果表明:醋酸钙溶液需掺入氢氧化钠,将其中的醋酸钙转化成氢氧化钙,方可碳化生成沉淀碳酸钙;在由醋酸提取钢渣中钙离子所获得的醋酸钙溶液中掺入足量氢氧化钠,可使其中的钙离子碳化生成沉淀碳酸钙,但该碳酸钙的纯度(质量分数)仅为60%左右,钙离子转化率(质量分数)仅为35.00%左右,如果将该溶液进行分离处理,除去其中其他离子的干扰,则可高效碳化成高纯度沉淀碳酸钙.

  20. The effect of alginates, fucans and phenolic substances from the brown seaweed Padina gymnospora in calcium carbonate mineralization in vitro

    Science.gov (United States)

    Salgado, L. T.; Amado Filho, G. M.; Fernandez, M. S.; Arias, J. L.; Farina, M.

    2011-04-01

    The mineralization of calcium carbonate (CaCO 3) in the brown seaweed Padina gymnospora is a biologically induced process and is restricted to the cell wall surface. It has been suggested that the CaCO 3 crystallization that occurs over the thallus cell wall surface is induced by changes in the surface pH caused by a local efflux of OH -, Ca ++ and HCO3- ions. However, no studies on the roles of the P. gymnospora cell wall components in this mineralization process had been performed. Therefore, we evaluated the influence of a subset of P. gymnospora cell wall molecules on CaCO 3 crystallization in vitro. The molecules tested were the anionic polysaccharides alginates and fucans (with potential nucleation activity) and phenolic substances (secondary metabolites with amphipathic property). The crystallization assays were performed using polystyrene microbridges as the crystallization apparatus. Crystals formed in the microbridges were analyzed using scanning electron microscopy. Interestingly, the results confirmed that the phenolic substances have the specific capability of changing the morphology of calcite crystals grown in vitro by inducing an elongated morphology in the direction of the c-axis. This morphology is similar to that induced by molecules that attach to { h k 0}-crystal planes. It was also shown that the alginates and the fucans do not specifically modulate the morphology of the growing crystals. In fact, these crystals exhibited a rounded shape due to the slower growth rates of several new crystal planes that appeared in the place of the original corners and edges.

  1. Incorporating benthic community changes into hydrochemical-based projections of coral reef calcium carbonate production under ocean acidification

    Science.gov (United States)

    Shaw, Emily C.; Hamylton, Sarah M.; Phinn, Stuart R.

    2016-06-01

    The existence of coral reefs is dependent on the production and maintenance of calcium carbonate (CaCO3) framework that is produced through calcification. The net production of CaCO3 will likely decline in the future, from both declining net calcification rates (decreasing calcification and increasing dissolution) and shifts in benthic community composition from calcifying organisms to non-calcifying organisms. Here, we present a framework for hydrochemical studies that allows both declining net calcification rates and changes in benthic community composition to be incorporated into projections of coral reef CaCO3 production. The framework involves upscaling net calcification rates for each benthic community type using mapped proportional cover of the benthic communities. This upscaling process was applied to the reef flats at One Tree and Lady Elliot reefs (Great Barrier Reef) and Shiraho Reef (Okinawa), and compared to existing data. Future CaCO3 budgets were projected for Lady Elliot Reef, predicting a decline of 53 % from the present value by end-century (800 ppm CO2) without any changes to benthic community composition. A further 5.7 % decline in net CaCO3 production is expected for each 10 % decline in calcifier cover, and net dissolution is predicted by end-century if calcifier cover drops below 18 % of the present extent. These results show the combined negative effect of both declining net calcification rates and changing benthic community composition on reefs and the importance of considering both processes for determining future reef CaCO3 production.

  2. 碳纤维增强磷酸钙骨水泥%The calcium phosphate bone cement reinforced by carbon fiber

    Institute of Scientific and Technical Information of China (English)

    张睿; 张彭风; 薛润苗; 王志强

    2012-01-01

    以碳纤维为增强相,Na2HPO4/柠檬酸为调和液,α-磷酸三钙、磷酸四钙、磷酸二氢钙、羟基磷灰石和碳酸钙为原料制备骨水泥,研究不同掺杂比例的短碳纤维对其性能的影响.在磷酸钙骨水泥中掺杂碳纤维能够提高样品的致密性,缩短固化时间,提高抗压强度.当掺杂质量分数0.5%的碳纤维时,骨水泥的初凝、终凝时间分别为9.3和24.9 min,模拟体液中浸泡28 d后抗压强度最大为38.24MPa.掺杂的碳纤维对浸泡液pH影响不大,pH在小范围内浮动,均在人体安全范围内.%The effect of carbon fiber on the performance of calcium phosphate bone cement was studied. Calcium phosphate bone cement doped with carbon fiber was prepared from crtricalcium phosphate, tetracalcium phosphate, monocalcium phosphate monohydrate, hydroxyapatite and calcium carbonate, in which Na2 HPO4/citric acid was added as mixing liquid. The results show that carbon fiber doped in calcium phosphate cement can increase the density, reduce the setting time and enhance the compressive strength. When the doping amount of carbon fiber is 0.5%, the initial setting time and the final setting time is respectively 9. 3 and 24. 9 min. The compressive strength reaches up to 38. 24 MPa after immersed 28 d in the simulated body fluid. Meanwhile, the doping of carbon fiber has little influence on the change of pH, which is in the range of human security.

  3. 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

  4. Salt-enhanced chemical weathering of building materials and bacterial mineralization of calcium carbonate as a treatment

    Science.gov (United States)

    Schiro, M.; Ruiz-Agudo, E.; Jroundi, F.; Gonzalez-Muñoz, M. T.; Rodriguez-Navarro, C.

    2012-04-01

    Salt weathering is an important mechanism contributing to the degradation and loss of stone building materials. In addition to the physical weathering resulting from crystallization pressure, the presence of salts in solution greatly enhances the chemical weathering potential of pore waters. Flow through experiments quantify the dissolution rates of calcite and quartz grains (63-125 micrometer diameter) when subjected to 1.0 ionic strength solutions of MgSO4, MgCl, Na2SO4 or NaCl. Results indicate that the identity of the cation is the primary control over the dissolution rate of both calcite and quartz substrates, with salt-enhanced dissolution occurring most rapidly in Mg2+ bearing solutions. It has been observed that weathering rates of rocks in nature, as well as building stones, are slowed down by naturally occurring or artificially produced patinas. These tend to be bacterially produced, durable mineralized coatings that lend some degree of protection to the underlying stone surface [1]. Our research shows that bacterially produced carbonate coatings can be quite effective at reducing chemical weathering of stone by soluble salts. The calcite-producing-bacteria used in this study were isolated from stone monuments in Granada, Spain [2] and cultivated in an organic-rich culture medium on a variety of artificial and natural substrates (including limestone, marble, sandstone, quartz, calcite single crystals, glass cover-slips, and sintered porous glass). Scanning electron microscopy (FESEM) was used to image bacterial calcite growth and biofilm formation. In-situ atomic force microscopy (AFM) enabled calculation of dissolution rates of untreated and bacterially treated surfaces. 2D-XRD showed the mineralogy and crystallographic orientation of bacterial calcium carbonate. Results indicate that bacterially produced calcite crystals form a coherent, mechanically resistant surface layer in perfect crystallographic continuity with the calcite substrate (self

  5. The cationic composition and pH in the moulting fluid of Porcellio scaber (Crustacea, Isopoda) during calcium carbonate deposit formation and resorption.

    Science.gov (United States)

    Ziegler, Andreas

    2008-01-01

    Before moulting, terrestrial isopods resorb calcium carbonate (CaCO(3)) from the posterior cuticle and store it in sternal deposits. These consist mainly of amorphous calcium carbonate (ACC) spherules that develop within the ecdysial space between the anterior sternal epithelium and the old cuticle. Ions that occur in the moulting fluid, including those required for mineral deposition, are transported from the hemolymph into the ecdysial space by the anterior sternal epithelial cells. The cationic composition of the moulting fluid probably affects mineral deposition and may provide information on the ion-transport activity of the sternal epithelial cells. This study presents the concentrations of inorganic cations within the moulting fluid of the anterior sternites during the late premoult and intramoult stages. The most abundant cation is Na(+) followed by Mg(2+), Ca(2+) and K(+). The concentrations of these ions do not change significantly between the stages whereas the mean pH changed from 8.2 to 6.9 units between mineral deposition in late premoult, and resorption in intramoult, respectively. Measurements of the transepithelial potential show that there is little driving force for passive movements of calcium across the anterior sternal epithelium. The results suggest a possible role of magnesium ions in ACC formation, and a contribution of pH changes to CaCO(3) precipitation and dissolution.

  6. A comparison of the long-term effects of lanthanum carbonate and calcium carbonate on the course of chronic renal failure in rats with adriamycin-induced nephropathy.

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Takashima

    Full Text Available Lanthanum carbonate (LA is an effective phosphate binder. Previous study showed the phosphate-binding potency of LA was twice that of calcium carbonate (CA. No study in which LA and CA were given at an equivalent phosphate-binding potency to rats or humans with chronic renal failure for a long period has been reported to date. The objective of this study was to compare the phosphate level in serum and urine and suppression of renal deterioration during long-term LA and CA treatment when they were given at an equivalent phosphate-binding potency in rats with adriamycin (ADR-induced nephropathy. Rats were divided into three groups: an untreated group (ADR group, a CA-treated (ADR-CA group and a LA-treated (ADR-LA group. The daily oral dose of LA was 1.0 g/kg/day and CA was 2.0 g/kg/day for 24 weeks. The serum phosphate was lower in the ADR-CA or ADR-LA group than in the ADR group and significantly lower in the ADR-CA group than in the ADR group at each point, but there were no significant differences between the ADR and ADR-LA groups. The serum phosphate was also lower in the ADR-CA group than in the ADR-LA group, and there was significant difference at week 8. The urinary phosphate was significantly lower in the ADR-CA group than in the ADR or ADR-LA group at each point. The urinary phosphate was also lower in the ADR-LA group than in the ADR group at each point, and significant difference at week 8. There were no significant differences in the serum creatinine or blood urea nitrogen among the three groups. In conclusion, this study indicated the phosphate-binding potency of LA isn't twice as strong as CA, and neither LA nor CA suppressed the progression of chronic renal failure in the serum creatinine and blood urea nitrogen, compared to the untreated group.

  7. [Microbial geochemical calcium cycle].

    Science.gov (United States)

    Zavarzin, G A

    2002-01-01

    The participation of microorganisms in the geochemical calcium cycle is the most important factor maintaining neutral conditions on the Earth. This cycle has profound influence on the fate of inorganic carbon, and, thereby, on the removal of CO2 from the atmosphere. The major part of calcium deposits was formed in the Precambrian, when prokaryotic biosphere predominated. After that, calcium recycling based on biogenic deposition by skeletal organisms became the main process. Among prokaryotes, only a few representatives, e.g., cyanobacteria, exhibit a special calcium function. The geochemical calcium cycle is made possible by the universal features of bacteria involved in biologically mediated reactions and is determined by the activities of microbial communities. In the prokaryotic system, the calcium cycle begins with the leaching of igneous rock predominantly through the action of the community of organotrophic organisms. The release of carbon dioxide to the soil air by organotrophic aerobes leads to leaching with carbonic acid and soda salinization. Under anoxic conditions, of major importance is the organic acid production by primary anaerobes (fermentative microorganisms). Calcium carbonate is precipitated by secondary anaerobes (sulfate reducers) and to a smaller degree by methanogens. The role of the cyanobacterial community in carbonate deposition is exposed by stromatolites, which are the most common organo-sedimentary Precambrian structures. Deposition of carbonates in cyanobacterial mats as a consequence of photoassimilation of CO2 does not appear to be a significant process. It is argued that carbonates were deposited at the boundary between the "soda continent", which emerged as a result of subaerial leaching with carbonic acid, and the ocean containing Ca2+. Such ecotones provided favorable conditions for the development of the benthic cyanobacterial community, which was a precursor of stromatolites.

  8. In-situ encapsulation and application of nano-sized calcium carbonate%纳米碳酸钙的原位包覆及应用

    Institute of Scientific and Technical Information of China (English)

    王权广; 朱勇; 黄炜民; 黄炜波

    2012-01-01

    In order to modify the nano-sized calcium carbonate better,fatty acid was adopted to dope it in-situ and the mechanism of in-situ encapsulation was discussed.An appropriate amount of alkali was introduced to some just prepared milk of nano-sized calcium carbonate which followed by being heated to 75.0-90.0 t.By the aid of stirring,needed amount of fatty acid was added into the milk.After filtrating, drying, and pulverizing, nano-sized encapsulated calcium carbonate powders were obtained.Characterization of oil absorption,contact angles,and scanning electron microscopy of the powders,and their filling application experiments in vulcanized silicone rubber and DOP in room temperature indicated: each calcium carbonate particle was uniformly and thoroughly encapsulated by fatty acid, and the calcium carbonate fillers could drastically enhance some properties of polymer.Research showed that 90 °C ,re(SA+OA):re(OH")=l:l and 7i(SA+OA)/ro(CaCO3)=1.0x 10^" mol/g were the suitable conditions for the in-situ encapsulation of nano-sized calcium carbonate.%为更好地改性纳米碳酸钙,采用脂肪酸(SA)对纳米碳酸钙进行原位包覆,并对原位包覆法机理作了探讨.先在纳米碳酸钙浆液中加入一定量强碱,然后将浆液加热至75.0~90.0℃,再在机械搅拌辅助下加入适量脂肪酸,浆液经过滤、干燥和粉碎解聚得表面包覆改性的纳米碳酸钙.包覆碳酸钙的吸油值、接触角测试,扫描电子显微镜表征及其在室温硫化硅橡胶和DOP糊中的应用实验表明:脂肪酸在纳米碳酸钙表面形成均匀、完整的包覆层,改性碳酸钙在聚合物中具有极佳的应用效果.研究发现,温度为90℃,n(SA+OA)∶n(OH-)=1∶1,n(SA+OA)/m(CaCO3)=1.Ox 10-4 mol/g是原位法表面包覆纳米碳酸钙比较合适的条件.

  9. Study on the Effect of Process before Carbonation for Nano Calcium Carbonate%碳化前工艺条件对纳米碳酸钙产品性能的影响

    Institute of Scientific and Technical Information of China (English)

    苏承炎

    2012-01-01

    Nano calcium carbonate can be achieved by the process of calcining limestone, digesting quicklime and carbonation. The effect of process before carbonation was studied, and the rusult was that by the process of calcining limestone by electric heating, digestion reactivity and yield of milk of lime could be increased, and the performance of the product of nano calcium carbonate, included specific surface area, oil absorption value and whiteness, could be improved obvious; The performance of nano calcium carbonate also could be improved by the process of high temperature of digestion or increasing the aging time. Aging time could be shortened through adding agent H in the process of digestion.%石灰石经煅烧、消化、碳化可制取纳米碳酸钙产品,文章考察了碳化前的工艺条件对制备的纳米碳酸钙产品性能的影响,实验结果表明:采用电加热方式煅烧石灰石能过提高消化反应活性以及石灰乳的产率,并能提高碳化得到的纳米碳酸钙产品的比表面积,降低吸油值,提高产品的白度:采用高温消化以及增加石灰乳的陈化时间的方法,也能提高石灰乳的产率以及纳米碳酸钙产品的比表面积,并且在消化时加入药剂H能过缩短陈化时间。

  10. Isolation and Identification of a Bacterial Strain Inducing Mineralization of Calcium Carbonate%一株碳酸钙矿化菌的分离与鉴定

    Institute of Scientific and Technical Information of China (English)

    张振远; 李广悦; 丁德馨; 王永东; 胡南

    2014-01-01

    基于微生物诱导碳酸钙沉积的岩土工程加固技术是一种环境友好的新技术。碳酸钙矿化菌是该技术应用的前提。为获得具有诱导碳酸钙沉积能力的菌株,采用选择性富集培养、平板分离方法从土壤中分离得到了一株具有尿素分解能力的菌株,细菌诱导产生的沉积物检测结果表明该菌株具有诱导碳酸钙沉积能力。通过形态学、革兰氏染色和16 S rDNA序列同源性分析鉴定该菌株为巴斯德芽孢杆菌。%Biocementation through microbial calcium carbonate precipitation is an innova-tive and environmentally friendly rock and soil reinforcement technique in geotechnical en-gineering. The bacteria inducing mineralization of calcium carbonate is a prerequisite to im-plement the biological treatment process. In order to obtain the strain with ability to induce CaCO3 precipitation,a ureolytic strain was isolated from soil using selective enrichment cul-ture and plate screening techniques. The precipites induced by this stain were examined, and the results showed it was capable of inducing calcium carbonate mineralization. The strain was identified as Sporosarcina pasteurii based on morphology,Gram stain and 16S rDNA sequence analysis.

  11. Crystallization of calcium carbonate (CaCO3) in a flowing system: Influence of Cu2+ additives on induction time and crystalline phase transformation

    Science.gov (United States)

    Usmany, Y.; Putranto, W. A.; Bayuseno, A. P.; Muryanto, S.

    2016-04-01

    Scaling of calcium carbonate (CaCO3) is commonly found in piping systems in oil, gas, desalination and other chemical processes. The scale may create technical problems, leading to the reduction of heat transfer, increase of energy consumption and unscheduled equipment shutdown. This paper presents crystallization scaling experiments and evaluation of the effect of Cu2+ additives on the induction time and calcium carbonate transformation. The crystals precursors were prepared using equimolar of CaCl2 and Na2CO3 resulted in concentrations of 3000 ppm Ca2+ in the solution. The Cu2+ in amounts of 0, 1 and 10 ppm was separately added in the solution. The flow rates (20, 35, and 60 mL/min) and elevated temperatures (27, 35 and 45°C) were selected in the study. The induction time for crystallization of CaCO3 was observed by measuring the solution conductivity over time, while the phase transformation of calcium carbonate was examined by XRD method and SEM/EDX. It was found that the conductivity remained steady for a certain period reflecting to the induction time of crystal formation, and then decreased sharply afterwards,. The induction time was increased from 34 and 48 minutes in the presence of Cu additives (1 and 10 ppm), depending on the flow rates and temperature observed. In all the experiments, the Cu2+ addition leads to the reduction of mass of crystals. Apparently, the presence of Cu2+ could inhibit the CaCO3 crystallization. In the absence of Cu2+ and at elevated temperature, the crystals obtained were a mixture of vaterite and calcite. In the presence of Cu2+ and at elevated temperature, the crystals formed were aragonite and calcite. Here, the presence of Cu2+ additives might have controlled the crystal transformation of CaCO3.

  12. Atributos químicos de solos influenciados pela substituição do carbonato por silicato de cálcio Soil chemical properties influenced by the substitution of calcium carbonate by calcium silicate

    Directory of Open Access Journals (Sweden)

    Renato Ferreira de Souza

    2008-08-01

    ácia do silicato de Ca foi inferior à de carbonato de Ca na melhoria das condições químicas do solo.The application of silicates to soils can result in increased soil cation exchange capacity (CEC, displace anions, especially H2PO4- (diacid phosphate, neutralize the pH and Al toxicity and, in general, increase the nutrient availability to plants. However, calcium silicates may be less efficient than calcium carbonates. To evaluate the effect of calcium carbonate substitution by calcium silicate on the soil chemical properties, especially on phosphorus availability, four experiments were conducted in an entirely randomized design with four replications, in a greenhouse. The treatments consisted of five levels (0, 25, 50, 75, and 100 % of calcium carbonate substitution by calcium silicate, with a 4:1 Ca:Mg stoichiometric and the same amount of CaO, enough to reach a 60 % base saturation. The treatments were applied to 4 dm³ samples of a sandy orthic Quartzarenic Neosol (Quartzpsament, a sandy loam dystrophic Red-Yellow Latosol (Oxisol, sandy clay loam dystrophic Red-Yellow Latosol (Oxisol and a clayey dystrophic Red Latosol (Oxisol; each soil represented one experiment. The pH values in H2O, P, phosphorus in the equilibrium solution (P-rem, K, Ca, Mg, Si, Al, H + Al, organic matter (OM, Cu, Mn, Zn and B, sum of bases (S, effective (t ant total (T CEC, base saturation (V and Al saturation (m were submitted to analysis of variance and simple regression models fitted as a function of CaCO3 substitution by CaSiO3 levels. It was observed that carbonate substitution by silicate promoted significant increases in the values of Si, Al, H + Al and m and reduction in the values of P-rem, pH, S, t and V. The values of Mehlich 1 P, K, Mg, OM, T, Mn, Cu, and B were not influenced significantly. A reduction in Zn availability was verified in the dystrophic orthic Quartzarenic Neosol only. Calcium silicate was less efficient than calcium carbonate in the improvement of soil chemical

  13. Study on the Effect of Digestion Temperature for Nano Calcium Carbonate%消化用水的温度对纳米碳酸钙产品性能的影响

    Institute of Scientific and Technical Information of China (English)

    苏承炎; 刘亚雄; 韩艳敏; 林新仁

    2011-01-01

    Nano calcium carbonate can be produced by carbonating Ca(OH)2 slurry.The effect of digestion temperture for calcium carbonate,included the yield of milk of lime,particle size distribution,specific surface area,oil absorption and whiteness,was studied.The result was that through the high digestion temperature,a high yield of milk of lime about 92% can be achieved,the specific surface area of nano calcium carbonate was increased obviously,while the particle size and oil absorption of nano calcium carbonate was decreased,but less impact on the whiteness of nano calcium carbonate.The best digestion temperature was 60 ℃ to get higher specific surface area and lower oil absorption of nano calcium carbonate.%采用碳化法制备了纳米碳酸钙,考察了消化时的水温对石灰乳产率、制备的纳米碳酸钙产品的粒径分布、比表面积、吸油值和白度等物理性能的影响。结果表明:石灰经高温消化,能够提高石灰乳的产率,产率可达92%;高温消化有利于碳酸钙比表面积的升高、同时降低碳酸钙的颗粒粒度及吸油值,对碳酸钙的白度影响较小。当消化用水的温度为60℃时,制备的碳酸钙比表面积较高,而其粒度和吸油值较低。

  14. 磷石膏脱硫钙渣制备轻质碳酸钙%Preparation of light calcium carbonate from phosphorus gypsum desulfurization slag

    Institute of Scientific and Technical Information of China (English)

    时婷; 王新刚; 巫建锋; 杨秀山; 杨林; 王辛龙

    2015-01-01

    To recycle desulfurization slag from phosphorous gypsum,spherical calcium carbonate was prepared from calcium-containing phosphorus gypsum desulfurization slag. The composition of raw materials were analyzed by XRD and SEM. The main substance was calcium oxide and the main impurity was silica. It also contained a small amount of iron,aluminum and magnesium. A new process leaching desulfurization slag by ammonium chloride and subsequent carbonization was firstly proposed. The affecting factors , such as amount of ammonium chloride , ratio of water and desulfurization slag(mass ratio),and temperature on the performance of leaching were investigated. The optimal conditions were: Amount of ammonium chloride 50% of the total weight of the solid, ratio of water and desulfurization slag 9∶1,temperature 40℃. Conversion of calcium was about 67.98% and removal of silica was 97.80% under the optimal conditions. The purity of the obtained calcium carbonate was 97.90%,sedimentation volume was 3.5mL/g and whiteness was 94.2, meeting the norm of first grade product in(HG/T 2226—2010). Main polymorph of calcium carbonate crystals was vaterite.%为了有效利用磷石膏脱硫钙渣资源,以磷石膏脱硫钙渣为原料合成了球形轻质碳酸钙。本文首先利用XRD 和 SEM 等测试手段分析了磷石膏脱硫钙渣的主要组成是氧化钙,主要杂质为二氧化硅以及少量铁铝镁。在此基础上首次提出了氯化铵浸取磷石膏脱硫钙渣,而后碳化合成轻质碳酸钙的新工艺。探讨了浸取过程中氯化铵的添加量,水与钙渣的液固比(质量比),温度工艺参数对钙浸取率和硅脱除率的影响,确定了较优工艺条件为:氯化铵添加量为总固体质量的50%,水与钙渣的液固比为9∶1,温度为40℃。在该工艺条件下,钙的浸取率可达67.98%,硅的脱除率可达97.80%。对上述浸取液经碳化制备出的轻质碳酸钙,其纯度为97.90%,白度为94.2

  15. 由低品位菱镁矿制备碳酸钙和氧化镁%Preparation of Calcium Carbonate and Magnesia from Low-grade Magnesite

    Institute of Scientific and Technical Information of China (English)

    朱世玲; 张悦; 薛向欣

    2013-01-01

      低品位菱镁矿经煅烧、消化、碳化反应及镁的沉淀反应可制备碳酸钙和氧化镁,沉淀反应产生的氯化钙母液可循环使用,并实现低品位菱镁矿中钙和镁的完全分离。结果表明,低品位菱镁矿950℃煅烧2 h时,其失重率接近理论失重率;煅烧粉末中主要含有MgO和CaO。消化、碳化反应的最佳条件为:反应温度20℃,反应时间1 h,CaCl2过量系数0,CO2流量400 mL/h,相应镁溶出率为95.0%。氧化镁产物中MgO含量为95.6%;碳酸钙产物中MgO和CaO的含量分别为1.24%和53.40%。%The low-grade magnesite was calcined, hydrated and then reacted with CO2 and calcium chloride solution to obtain calcium carbonate and the solution of MgCl2. The precipitation reaction of magnesium was processed to produce MgO, and filtrate of CaCl2 solution can be used circularly. In addition, calcium and magnesium contained in low-grade magnesite was separated. The results showed that the mass loss of the low-grade magnesite calcined at 950℃for 2 h was close to the theoretical mass loss, and the calcined low-grade magnesite mainly contained CaO and MgO. The best conditions of hydrated and carbonized reaction was:20℃for 1 h, the excess coefficient of CaCl2 was 0, and CO2 gas flow of 400 mL/h, under which the dissolved ratio of magnesium was 95.0%. The content of MgO in magnesia was 95.6%, the content of MgO and CaO in calcium carbonate was 1.24%and 53.40%, respectively.

  16. Biomimetic mineralization of CaCO3 on a phospholipid monolayer: from an amorphous calcium carbonate precursor to calcite via vaterite.

    Science.gov (United States)

    Xiao, Junwu; Wang, Zhining; Tang, Yecang; Yang, Shihe

    2010-04-06

    A phospholipid monolayer, approximately half the bilayer structure of a biological membrane, can be regarded as an ideal model for investigating biomineralization on biological membranes. In this work on the biomimetic mineralization of CaCO(3) under a phospholipid monolayer, we show the initial heterogeneous nucleation of amorphous calcium carbonate precursor (ACC) nanoparticles at the air-water interface, their subsequent transformation into the metastable vaterite phase instead of the most thermodynamically stable calcite phase, and the ultimate phase transformation to calcite. Furthermore, the spontaneity of the transformation from vaterite to calcite was found to be closely related to the surface tension; high surface pressure could inhibit the process, highlighting the determinant of surface energy. To understand better the mechanisms for ACC formation and the transformation from ACC to vaterite and to calcite, in situ Brewster angle microscopy (BAM), ex situ scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction analysis were employed. This work has clarified the crystallization process of calcium carbonate under phospholipid monolayers and therefore may further our understanding of the biomineralization processes induced by cellular membranes.

  17. 柠檬酸钠表面改性重钙粉体的研究%Study on sodium citrate surface modification ground calcium carbonate powder

    Institute of Scientific and Technical Information of China (English)

    周国永; 陈丽莎; 成琳

    2011-01-01

    研究了柠檬酸钠用量、反应温度、反应时间、浆料浓度对重钙粉体表面改性的影响.结果表明,柠檬酸钠用量为重钙粉体的6.0%(质量分数),改性温度65℃,改性时间45 min,浆料浓度为12.5%时,重钙粉体沉降体积降为0.65 mL/g,活化度可达到67.9%,吸油值降为230 mg/g,粘度值降低为120 mPa·s,pH值8.50.%The effect of modifier amount, modification temperature, time and slurry concentration on modification were studied. The results showed sodium citrate can be used to modify calcium carbonate powder, the best conditions were as follows: sodium citrate amount 6% , modification temperature 65 X., modification time 45 min, slurry concentration 12.5%. The settling volume reduced to 0.65 Ml/g, the activation grade was 67. 9% ,the oil absorption decreased to 230 mg/g, viscosity of calcium carbonate reduced to 120 mPa·S,Ph value was 8.50.

  18. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris

    Energy Technology Data Exchange (ETDEWEB)

    Brinza, Loredana [Diamond Light Source, Harwell Campus, Didcot, Oxon OX11 0DE (United Kingdom); Schofield, Paul F. [Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom); Hodson, Mark E. [University of York, York YO10 5DD (United Kingdom); Weller, Sophie [University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D.; Mosselmans, J. Frederick W., E-mail: fred.mosselmans@diamond.ac.uk [Diamond Light Source, Harwell Campus, Didcot, Oxon OX11 0DE (United Kingdom)

    2014-01-01

    A new experimental set-up enabling microfocus fluorescence XANES mapping and microfocus XRD mapping on the same sample at beamline I18 at Diamond Light Source is described. To demonstrate this set-up the heterogeneous mineralogy in calcium carbonate granules excreted by the earthworm Lumbricus terrestris has been analysed. Data analysis methods have been developed which enable µXRD and µXANES two-dimensional maps to be compared. The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.

  19. A PRELIMINARY INVESTIGATION INTO THE USE OF ACID-TOLERANT PRECIPITATED CALCIUM CARBONATE FILLERS IN PAPERMAKING OF DEINKED PULP DERIVED FROM RECYCLED NEWSPAPER

    Directory of Open Access Journals (Sweden)

    Jing Shen

    2009-08-01

    Full Text Available The use of acid-tolerant precipitated calcium carbonate fillers, including phosphoric acid/sodium hexametaphosphate modified precipitated CaCO3 filler, and sodium silicate/phosphoric acid/sodium hexametaphos-phate modified precipitated CaCO3 filler in papermaking of deinked pulp derived from recycled newspaper was explored. These two acid-tolerant fillers provided considerably more brightness improvement in papers in comparison the unmodified filler, presumably indicating alleviated pulp darkening achieved as a result of better acid-resistant properties. The addition of acid-tolerant fillers into the furnish slurries gave lower system pH as compared with unmodified filler. Among the three fillers used in this work, the effect on retention of modification of the filler with sodium silicate/phosphoric acid/sodium hexametaphosphate was probably the best, as evaluated from ash content measurements. For air permeability of the paper, the use of acid-tolerant fillers provided slightly more improvement in comparison to the unmodified filler. For tensile and burst strength of the paper, the use of sodium silicate/phosphoric acid/sodium hexameta-phosphate modified precipitated calcium carbonate filler gave better results as compared with the other two fillers. Additionally, the improving effect of acid-tolerant fillers on furnish static drainage was found to be slightly weaker than that of unmodified filler.

  20. The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering

    Science.gov (United States)

    Hain, Mathis P.; Sigman, Daniel M.; Higgins, John A.; Haug, Gerald H.

    2015-05-01

    Reconstructed changes in seawater calcium and magnesium concentration ([Ca2+], [Mg2+]) predictably affect the ocean's acid/base and carbon chemistry. Yet inaccurate formulations of chemical equilibrium "constants" are currently in use to account for these changes. Here we develop an efficient implementation of the MIAMI Ionic Interaction Model to predict all chemical equilibrium constants required for carbon chemistry calculations under variable [Ca2+] and [Mg2+]. We investigate the impact of [Ca2+] and [Mg2+] on the relationships among the ocean's pH, CO2, dissolved inorganic carbon (DIC), saturation state of CaCO3 (Ω), and buffer capacity. Increasing [Ca2+] and/or [Mg2+] enhances "ion pairing," which increases seawater buffering by increasing the concentration ratio of total to "free" (uncomplexed) carbonate ion. An increase in [Ca2+], however, also causes a decline in carbonate ion to maintain a given Ω, thereby overwhelming the ion pairing effect and decreasing seawater buffering. Given the reconstructions of Eocene [Ca2+] and [Mg2+] ([Ca2+]~20 mM; [Mg2+]~30 mM), Eocene seawater would have required essentially the same DIC as today to simultaneously explain a similar-to-modern Ω and the estimated Eocene atmospheric CO2 of ~1000 ppm. During the Cretaceous, at ~4 times modern [Ca2+], ocean buffering would have been at a minimum. Overall, during times of high seawater [Ca2+], CaCO3 saturation, pH, and atmospheric CO2 were more susceptible to perturbations of the global carbon cycle. For example, given both Eocene and Cretaceous seawater [Ca2+] and [Mg2+], a doubling of atmospheric CO2 would require less carbon addition to the ocean/atmosphere system than under modern seawater composition. Moreover, increasing seawater buffering since the Cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and CO2 concentration mechanisms that aid photosynthesis.

  1. Study on Precipitation Process of Spherical Calcium Carbonate Controlled by Polyaspartic Acid%PASP调控球形碳酸钙沉积过程研究

    Institute of Scientific and Technical Information of China (English)

    杨士林; 宋微

    2013-01-01

    Using polyaspartic acid (PASP) as the organic template,the precipitation process of calcium carbonate in aqueous solution was examined by the carbonation method.The precipitated samples were characterized by FTIR,XRD,SEM and Granularity analyzer.Moreover,the form and growth process of crystal nucleus and morphology changes of precipitated calcium carbonate were analyzed according to the biomimetic mineralization theory.The results showed that crystal transformation of calcium carbonate from calcite to vaterite and its morphology changes from rhombic to sphere is produced in the presence of polyaspartic acid.The average size of precipitated particles has reduced 64.3%,and the distribution of particle size tends to narrow.The main reason was that the distance of both adjacent COO-was matchedto that of both oxygen atoms in the 12 spatial configuration ligands of Ca2+.The spherical particles with small crystal on its surface was formed via mesomorphic,thus crystal growth was inhibited because of polyaspartic acid adsorbed on the surface of particle.%本文以聚天冬氨酸(PASP)为有机质模板,采用碳化法研究了水溶液中碳酸钙的沉积过程,利用FT-IR、XRD、SEM及粒度分析等方法对碳酸钙沉积样品晶型和晶貌进行了表征,并结合生物矿化的基本原理分析了晶体形成和成长变化过程.结果表明,有机质PASP能够调控碳酸钙沉积由方解石型转变为球霰石型,晶体形貌由菱形转变为球形,同时晶体平均粒径减小64.3%,且粒径分布收窄.主要原因是PASP模板中相邻两-COO-间距离与Ca2+的12配位体空间构型中的两个氧原子间距离相匹配,碳酸钙颗粒经过介晶形成了表面为小颗粒附着的球形晶体,PASP吸附在颗粒表面能够抑制晶体生长.

  2. Coating of Microbially Produced Calcium Carbonate Precipitation on Marble%大理石表面微生物诱导碳酸钙覆膜

    Institute of Scientific and Technical Information of China (English)

    牟涛; 竹文坤; 段涛; 张友魁; 陈晓明

    2014-01-01

    选育碳酸盐矿化菌,利用其诱导CaCO3沉积,采用涂覆法和浸泡法进行细菌矿化试验,最终在大理石样品表面形成一层致密的矿化膜。采用扫描电镜(SEM)和X射线衍射(XRD)对大理石空白试样和处理后试样进行分析,并对矿化膜进行抗酸性测试。结果表明,涂覆法和浸泡法均能在大理石表面粘结一层细小颗粒,形成一层致密、厚度为50~100μm的CaCO3矿化膜。经过覆膜处理的大理石耐酸性能得到了明显提升。%CaCO3 precipitation was induced by carbonate-mineralization microbe using the immersion method and the coating method, and ifnally formed a dense mineralization membrane layer on marble sample surface. The immersed and smeared samples were characterized by scanning electron microscopic (SEM) and X-ray diffraction (XRD), as well as tested the acid-resistance of the calcium carbonate layer. Experimental results showed that both immersion method and coating method can produce calcium carbonate particle forming a layer of dense mineralization membrane of 50~100μm, acid-resistance of the coated marble samples was improved signiifcantly.

  3. Sedimentation rates of Sao Paulo coast by carbonate calcium content: an alternative for radiometric methods; Levantamento das taxas de sedimentacao do litoral de Sao Paulo a partir do teor de carbonato de calcio: uma alternativa aos metodos radiometricos

    Energy Technology Data Exchange (ETDEWEB)

    Figueira, Rubens C.L. [Universidade Cruzeiro do Sul, Sao Paulo, SP (Brazil). Centro de Tecnologia e Ciencias Exatas]. E-mail: figueira@ipen.br; figueiraru@yahoo.com.br; Tessler, Moyses G.; Mahiques, Michel M. de; Fukumoto, Marina M.M. [Sao Paulo Univ., SP (Brazil). Inst. Oceanografico. Dept. de Oceanografia Geologica]. E-mail: mgtessle@usp.br; mahiques@usp.br; marina@io.usp.br

    2005-07-01

    In this work it is presented a methodology of sedimentation rate determination by carbonate calcium content. The technique developed is an alternative for radiometric methods where are used {sup 210}Pb{sub unsupported} and {sup 137}Cs radionuclides. This methodology consisted in a determination of chronologic event along sedimentary column. In this work two events were used: the tsunami in Sao Vicente city, in 1542, and the maximum of 1{sup 37}Cs radioactive fallout from nuclear atmospheric tests, in 1963-65. It was possible to calculate the accumulation rate of total sediments and precipitation rate of calcium carbonate, which values are necessary to determine the age of slice from sedimentary column and consequently the sedimentation rate. The results obtained for Sao Paulo Continental Shelf had a good agreement with radiometric methods, the values were: 0.32({+-}0.12) cm.y{sup -1}, 0.23({+-}0.08) cm.y{sup -1} and 0.25({+-}0.9) cm.y{sup -1} for carbonate method, {sup 210}Pb{sub unsupported} (CIC model) and {sup 137}Cs (radioactive fallout), respectively. The analytical procedure using carbonate calcium content showed to be fast, efficient and with low cost. However, it must be used carefully, because the results can be strongly influenced by environmental factors which could change the precipitation rate of calcium carbonate and it could cause errors on sedimentation rate values in a determined area (author)

  4. Effectof Material Ratio on Phase Transfer Rate of Calcium Ions During Reaction between Calcium Sulfate Dihydrate and Ammonium Carbonate%二水硫酸钙与碳酸铵反应过程中物料比对钙离子相转移速率的影响

    Institute of Scientific and Technical Information of China (English)

    陈昌国; 周加贝; 夏素兰; 王子宁; 宫源; 刘仕忠

    2015-01-01

    选择二水硫酸钙晶须为研究对象,在温度、搅拌速度、料浆浓度不变的条件下,探究了二水硫酸钙与碳酸铵反应过程中物料比 n(NH 4)2 CO 3:nCaSO 4∙2 H 2 O 对钙离子相转移速率的影响。结果表明,物料比在1.05∶1~1.4∶1之间时,生成的碳酸钙沉淀于溶液中,钙离子相转移是溶解-结晶过程,二水硫酸钙转化率和碳酸钙颗粒粒径均随物料比增大而增大,即相转移速率与物料比成正比。%Calcium sulfate dihydrate whiskers were applied under constant temperature,stirring speed and slurry concentration.The material ratio of n(NH 4 )2 CO 3 ∶nCaSO 4 ∙2 H 2 O was changed to study its effect on phase transfer of calcium ions during the reaction between calcium sulfate dihydrate and ammonium car-bonate.The result showed that calcium carbonate crystals were precipitate in solution as the material ratio between 1.05∶1 and 1.4∶1,so corresponding mechanism of calcium ions phase transfer was dissolution-precipitation.It could found that both the conversion rate of calcium sulfate dihydrate and the calcium car-bonate particles size were increased with the increasing value of materials ratio.It indicated that the phase transfer rate of calcium ions was proportional to the material ratio.

  5. 电石渣制备轻质碳酸钙的研究%Study on Preparation of Light Calcium Carbonate with Carbide Slag

    Institute of Scientific and Technical Information of China (English)

    舒均杰

    2012-01-01

    The technology of preparation of light calcium carbonate by leaching,carbonization,filtrating,washing and drying precipitation using the material of carbide slag was studied,TEM and distribution measurement of particle size were employed to characterize the as-prepared samples.The effect of reaction temperature,concentration of carbon dioxide,gas velocity and stirring rate on reaction rate and particle size distribution are investigated,thus the optimal process conditions are determined.%研究了以电石渣为原料,经浸取、碳化、过滤、洗涤、干燥制备轻质碳酸钙的工艺。用TEM、粒径分布测试对所合成的样品进行表征。重点考查了碳化反应温度、二氧化碳体积浓度、气体流速、搅拌速率等因素对反应速率及产品粒径的影响,确定了最佳的工艺条件。

  6. Immobilization of trace elements in municipal solid waste incinerator (MSWI) fly ash by producing calcium sulphoaluminate cement after carbonation and washing.

    Science.gov (United States)

    Wang, Lei; Jamro, Imtiaz Ali; Chen, Qi; Li, Shaobai; Luan, Jingde; Yang, Tianhua

    2016-03-01

    The possibility of producing calcium sulphoaluminate cement (CSA) by adding municipal solid waste incinerator (MSWI) fly ash to raw meal was investigated. After subjecting MSWI fly ash to accelerated carbonation and washing with water (ACW), various amounts (i.e., 5, 10 and 15 wt%) of the treated ash were added to raw meal composed of a mixture of bauxite, limestone and gypsum. The mixtures were sintered in a laboratory-scale muffle furnace at temperatures of 1250°, 1300°, 1325° and 1350 °C for various durations. The influence of different quantities of MSWI fly ash on the mineralogy, major phase composition and strength development of the resulting clinker was studied, as was the effect of ash treatments on leaching and volatilization of trace elements. The ACW treatment reduced the volatilization ratio of trace elements during the clinkerization process. Volatilization ratios for lead, cadmium and zinc were 21.5%, 33.6% and 16.3%, respectively, from the ACW fly ash treatment, compared with ratios of 97.5%, 93.1% and 85.2% from untreated fly ash. The volatilization ratios of trace elements were ordered as follows: untreated fly ash > carbonated fly ash > carbonated and water-washed fly ash. The ACW process also reduced the chloride content in the MSWI fly ash by 90 wt% and prevented high concentrations of trace elements in the effluents.

  7. [Calcium carbide of different crystal formation synthesized by calcium carbide residue].

    Science.gov (United States)

    Lu, Zhong-yuan; Kang, Ming; Jiang, Cai-rong; Tu, Ming-jing

    2006-04-01

    To recycle calcium carbide residue effectively, calcium carbide of different crystal form, including global aragonite, calcite and acicular calcium carbide was synthesized. Both the influence of pretreatment in the purity of calcium carbide, and the influence of temperatures of carbonization reaction, release velocity of carbon dioxide in the apparition of calcium carbide of different crystal form were studied with DTA-TG and SEM. The result shows that calcium carbide residue can take place chemistry reaction with ammonia chlorinate straight. Under the condition that pH was above 7, the purity of calcium carbide was above 97%, and the whiteness was above 98. Once provided the different temperatures of carbonization reaction and the proper release velocity of carbon dioxide, global aragonite, calcite and acicular calcium carbide were obtained.

  8. Evaluation of polymer efficiency on the inhibition of calcium carbonate scale in synthetic brines; Avaliacao da acao de polimeros sobre a inibicao de incrustacoes de carbonato de calcio em salmouras sinteticas

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Juliana M.; Rodrigues, Jessica S.; Loureiro, Tatiana S.; Lucas, Elizabete F.; Spinelli, Luciana S. [Universidade Federal do Rio de Janeiro, Instituto de Macromoleculas, Laboratorio de Macromoleculas e Coloides na Industria de Petroleo, RJ (Brazil)], e-mail: julianamatos@ima.ufrj.br

    2011-07-01

    The inorganic scale results in serious problems for oil production. This scale results from the incompatibility between the chemical compositions of formation water and injection, and the changes of thermodynamic system. These deposits consist mainly of calcium carbonate and barium sulfate. In order to prevent the formation of these deposits, the petroleum industry has made use of chemicals that act as scale inhibitors. The aim of this study was to test the ability of two types of polymeric inhibitors prevent the formation of calcium carbonate from brines of different compositions with high concentrations of calcium. The inhibitors were tested at varying concentrations and at fixed conditions of temperature, pH, pressure and time. The estimated effectiveness of each inhibitor was measured by complexometric titration. The inhibitor carboxylic acid-based (poly (maleic acid)) was more efficient at relatively low concentrations, which is important both economically and environmentally. (author)

  9. Negundoside, an irridiod glycoside from leaves of Vitex negundo, protects human liver cells against calcium-mediated toxicity induced by carbon tetrachloride

    Institute of Scientific and Technical Information of China (English)

    Sheikh A Tasduq; Peerzada J Kaiser; Bishan D Gupta; Vijay K Gupta; Rakesh K Johri

    2008-01-01

    AIM: To evaluate the protective effect of 2'-p-hydroxy benzoylmussaenosidic acid [negundoside (NG), against carbon tetrachloride (CCl4)-induced toxicity in HUH-7 cells.METHODS: CCl4 is a well characterized hepatotoxin, and inducer of cytochrome P4502E1 (CYP2E1)-mediated oxidative stress. In addition, lipid peroxidation and accumulation of intracellular calcium are important steps in the pathway involved in CCl4 toxicity. Liver cells (HUH-7) were treated with CCl4, and the mechanism of the cytoprotective effect of NG was assessed. Silymarin, a known hepatoprotective drug, was used as control.RESULTS: NG protected HUH-7 cells against CCl4 toxicity and loss of viability without modulating CYP2E1 activity. Prevention of CCl4, toxicity was associated with a reduction in oxidative damage as reflected by decreased generation of reactive oxygen species (ROS), a decrease in lipid peroxidation and accumulation of intracellular Ca2+ levels and maintenance of intracellular glutathione homeostasis. Decreased mitochondrial membrane potential (MMP), induction of caspases mediated DNA fragmentation and cell cycle arrest, as a result of CCl4 treatment, were also blocked by NG. The protection afforded by NG seemed to be mediated by activation of cyclic adenosine monophosphate (cAMP) synthesis and inhibition of phospholipases (cPLA2).CONCLUSION: NG exerts a protective effect on CYP2El-dependent CCl4 toxicity via inhibition of lipid peroxidation, followed by an improved intracellular calcium homeostasis and inhibition of Ca2+-dependent proteases.

  10. Leguminous Plants Rhizobia Degradation of Calcium Carbonate and Magnesium Carbonate%石漠化地区豆科植物根瘤菌降解碳酸钙、镁能力研究

    Institute of Scientific and Technical Information of China (English)

    王明月; 刘绍雄; 熊智; 丁雅迪; 王艳玲; 李克艳; 阳廷丹; 陶茜; 王金华

    2014-01-01

    , the thesis studied on the 9 strains from leguminous plants rhizobia by the test of doing the strains in liquid medium with difficult soluble calcium carbonate or magnesium carbonate, then, handled with 28.5℃, 160 r·min-1 and 15 d table culture, sampled 2 ml of three at 0, 1, 3, 6, 10, 15 d. Samples added into the 10 mL digestive juices for a night, nitric acid and perchloric acid volume ratio was 5 to 1 of the digestive juices, heating Slowly, get clear solutions, the capacity to 10 mL by adding 2% hydrochloric acid solution which contain La3+,the same do with blank,used the flame atomic absorption method to determin contents of Ca2+ and Mg2+ in the samples parallel. We eagered to obtain the certain strains had strong degradation of calcium carbonate or magnesium carbonate. The results showed that the best calcium carbonate degradation strains wereRhizobium tropici (SWFU09) andRhizobium sp. (SWFU02), the best strains of magnesium carbonate degradation wereRhizobiumsp. (SWFU03), Rhizobium tropici(SWFU05) andBradyrhizobium sp. (SWFU01). The solution pH had an important influence on degradation of magnesium carbonate, but not obvious on calcium carbonate degradation. We could have a conclusion: acid producted by microbial metabolism had a certain influence on degradations of calcium carbonate and magnesium carbonate, but it was not the only factor. Organic ligand (base) also producted by microbial metabolism might adsorpt on calcium carbonate or magnesium carbonate surface, it could form compounds with ingredients in the water, change the balance of dissolution, Ca2+ and Mg2+were replaced.

  11. A fundamental study on carbon composites of FeF3.0.33H2O as open-framework cathode materials for calcium-ion batteries

    Science.gov (United States)

    Murata, Yoshiaki; Minami, Ryoji; Takada, Shoki; Aoyanagi, Kengo; Tojo, Tomohiro; Inada, Ryoji; Sakurai, Yoji

    2017-01-01

    Carbon composites of open-framework iron fluoride (FeF3.0.33H2O/C) was investigated as a new cathode material for calcium ion batteries for the first time. FeF3.0.33H2O/C delivers a relatively large capacity of ca. 110mAhg-1. Its reversible capacity was greatly improved over non-composite FeF3.0.33H2O. During the first discharge and discharge-charge, insertion/extraction of Ca2+ into/from FeF3.0.33H2O/C were confirmed by an ex-situ X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) analysis. From the ex-situ analysis results, it was confirmed that Ca2+ was inserted and extracted with redox of Fe.

  12. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris.

    Science.gov (United States)

    Brinza, Loredana; Schofield, Paul F; Hodson, Mark E; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D; Mosselmans, J Frederick W

    2014-01-01

    The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.

  13. Effects of SEBS-g-MAH on the properties of injection moulded poly(lactic acid/nano-calcium carbonate composites

    Directory of Open Access Journals (Sweden)

    W. S. Chow

    2012-06-01

    Full Text Available Poly(lactic acid/nano-precipitated calcium carbonate (PLA/NPCC composites toughened with maleated styrene-ethylene/butylene-styrene (SEBS-g-MAH were prepared by melt-compounding on a co-rotating twin-screw extruder followed by injection moulding. The mechanical properties of the PLA nanocomposites were characterized by tensile, flexural and impact tests, while their morphology were investigated using transmission electron microscopy (TEM. The thermal properties of the composites were examined with differential scanning calorimeter (DSC and thermogravimetric analyzer (TGA. The elongation at break and impact strength of the PLA/NPCC nanocomposites increased significantly after addition of SEBS-g-MAH. Both nano-dispersed NPCC and small NPCC clusters were found in PLA matrix. Also, some SEBS-g-MAH encapsulated NPCC can be observed. Thermal stability of PLA/NPCC was enhanced prominently by the addition of SEBS-g-MAH.

  14. Test and evaluation of different ifllers and calcium carbonate in paper-process reconstituted tobacco%造纸法烟草薄片中不同填料CaCO3的测试及评价

    Institute of Scientific and Technical Information of China (English)

    刘旭强; 李军; 王亚明; 刘维娟; 冯文超; 冀雅文; 朱红琴

    2014-01-01

    Through experiment, the influence of different fillers and additives on retention of paper-process reconstituted tobacco was analyzed. The results show that different fillers and additives on the retention are obviously different, the sedimentation volume of Rui bosi’s calcium carbonate is between precipitated calcium carbonate and ground calcium carbonate; the changing trend in basis weight of reconstituted tobacco made with different additives is different;ash content of different reconstituted tobacco leaves with different calcium carbonate ifller is also different.%分析研究了不同填料、不同助剂对造纸法再造烟叶薄片留着率的影响。结果表明:不同的填料和助剂制成的薄片的留着率存在明显差异;#4CaCO3沉降体积要介于轻质CaCO3和重质CaCO3的沉降体积之间;不同助剂的再造烟叶定量变化趋势有所不同;不同类型CaCO3填料的再造烟叶灰分不同。

  15. INTERFACE BEHAVIOR'S OF MODIFIED PRECIPITATED CALCIUM CARBONATE AND THE INFLUENCE ON PAPER'S PROPERTIES%轻质碳酸钙的改性及其对纸张性能的影响

    Institute of Scientific and Technical Information of China (English)

    陈均志; 单世群; 赵艳娜

    2006-01-01

    以自制的水溶性阳离子铝锆偶联剂对轻质碳酸钙进行了表面改性,比较了改性前后轻质碳酸钙的Zeta电位、润湿性、粘度、比表面积、沉降高度、扫描电镜图像以及在水中分散情况的变化,结果表明改性后轻质碳酸钙的表面性能得到改善,将此改性轻质碳酸钙作为填料抄纸发现,改性后轻质碳酸钙在纸页中的留着率大大提高,同时纸张抗张强度、耐破度、撕裂度等也得到提高.%Precipitated calcium carbonate was modified by homemade water-soluble cationic zircoaluminate coupling agents. The zata potential, the wettability, the viscidity, the surface area, the sedimentation height, the SEM image and the dispersion in water of precipitated calcium carbonate before and after modification were compared. The result indicates that the surface performance of precipitated calcium carbonate improve after modification. The modified precipitated calcium carbonate was used as filler in papermaking. The result indicates that the filler retention rate improves and the tensile strength, the burst strength and the tear strength of paper also improve too.

  16. Calcium supplements

    Science.gov (United States)

    ... do not help. Always tell your provider and pharmacist if you are taking extra calcium. Calcium supplements ... 2012:chap 251. The National Osteoporosis Foundation (NOF). Clinician's Guide to prevention and treatment of osteoporosis . National ...

  17. The Frontier Between Adsorption and Precipitation of Polyacrylic Acid on Calcium Carbonate Frontière entre adsorption et précipitation de l'acide polyacrylique sur le carbonate de calcium

    Directory of Open Access Journals (Sweden)

    Cabane B.

    2006-12-01

    Full Text Available Adsorption of polymers on mineral surfaces allowing colloidal stability have widespread applications in industrial processes. The binding mechanism has been quite well described on oxide surfaces. Mainly in terms of hydrogen bonds and electrostatic interactions between charged sites and polymer segments. This phenomenon has been modelized and the influence of pH. Ionic strentgh, and molecular weight can be calculated or predicted. In the case of sparingly soluble substrates such as BaSO4, CaCO3 or CaSO4, several problems arise : the difficulty for the identification of surface sites and the interference of ions coming from the material's solubility. In the case of calcite, the solubility imposes dissolved calcium ions in solution which could complex the polyelectrolyte and reduce its solubility. For that purpose, we have measured the binding energy using microcalorimetry. Microcalorimetric measurements have shown that the adsorption enthalpy is weakly enclothermic: about + 2 kj/mol. Interestingly, this value is very closed to that of calcium complexation with PANa. It is suggested that the driving force for adsorption is the net gain in entropy of the system. The microcalorimetric adsorption isotherm does not show any evidence for a strongly exothermic interaction between positive edges and negative segment of the polyion. Practically, in most cases, adsorption of polymers is calculated from the decrease of its concentration in the solution after separation of the solid by centrifugation. This procedure does not discriminate therefore between real adsorption and phase separation. To answer the question, we have performed adsorption experiments using a dialysis membrane to separate the solid particles from the solution. It has been established that in some circumstances, depending on the relative amount of calcite, calcium ions and polyelectrolyte, precipitation takes place rather than adsorption. This is especially the case at low polymer

  18. 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.

  19. 两种蔬菜汁液中碳酸钙介晶的生长%Crystal Growth of Calcium Carbonate Mesocrystals in the Juice of Two Vegetables

    Institute of Scientific and Technical Information of China (English)

    陈龙; 吴瑕玉; 万景建

    2012-01-01

    As is narrated in this paper, the and bok choy were used to induce the growth characterized by SEM images crystals were produced in the biomolecules in the juice of two vegetables such as turnip of calcium carbonate mesocrystals, and the products were and XRD patterns. The results showed that rhombus and spherical calcite juice of turnip while spherical calcite and vaterite crystals were generated in the juice of bok choy. Also, the formation mechanism of the products was discussed, calcium carbonate mesocrystals are formed through nonclassical crystallization pathways with the finding that under the control of vegetable biomolecules.%利用白萝卜和小白菜两种蔬菜汁液中的生物分子诱导碳酸钙介观晶体(介晶)的生长,采用扫描电子显微镜和X-衍射对所得产物进行表征。结果表明,白萝卜汁液中生成了菱面体形和球形的方解石型碳酸钙晶体;而小白菜汁液中则产生了球形的方解石和球霰石型碳酸钙晶体。对所得产物的形成机理进行了探讨,表明它们是在蔬菜生物分子的调控下通过非经典的结晶途径形成的碳酸钙介晶。

  20. 微纳分级结构碳酸钙中空微球的可控制备%Controllable Fabrication of Calcium Carbonate Hollow Microspheres with Micro-nano Hierarchical Structure

    Institute of Scientific and Technical Information of China (English)

    邹俭鹏; 杨洪志; 肖平; 潘一峰

    2016-01-01

    以CaCl2和Na2CO3为反应原料,以聚乙烯吡咯烷酮(PVP)和十二烷基磺酸钠(SDSN)为模板剂,在50℃采用化学沉淀反应,干燥、煅烧后成功制备了具有微纳分级结构的 CaCO3中空微球。采用扫描电子显微镜、透射电子显微镜和X射线衍射等检测手段对所制备的样品形貌、结构进行了表征,结果显示:所制备的微纳分级结构CaCO3中空微球直径为4~6μm,壳壁由直径约60 nm的CaCO3颗粒组成,壳层厚度约为200 nm, CaCO3中空微球晶相组成为方解石和球霰石的共混体。同时,在反应温度为50℃、PVP添加量为0.4 g, SDSN浓度为0.1 mol/L的条件下,所制备的微纳分级结构CaCO3中空微球分散性好,且形貌比较完整。%With polyvinyl pyrrolidone (PVP) and sodium dodecyl sulfonate (SDSN) as the template, calcium car-bonate hollow microspheres with micro-nano hierarchical structure were successfully synthesized using sodium carbonate and calcium chloride as starting materials through a precipitation reaction method at reaction temperature of 50℃. The products were characterized by scanning electronic microscopy (SEM), transmission electron micro-scope (TEM), X-ray diffraction (XRD) and other detection methods. The results show that the hollow calcium car-bonate microspheres with micro-nano hierarchical structure are about 4-6μm in diameter. The shell thickness of calcium carbonate hollow microspheres is about 200 nm, which consists of calcium carbonate particles with size about 60 nm. The phase of calcium carbonate hollow microspheres is composed of calcite and vaterite. Excellent dispersibility and spherical morphology of calcium carbonate hollow microspheres can be achieved with addition of 0.1 mol/L SDSN and 0.4 g PVP consequently.

  1. Nano Calcium Carbonate and Organic Acid-Modified Phenolic Resin on Water Resistance%有机酸改性纳米碳酸钙及其对酚醛树脂耐水性能的影响

    Institute of Scientific and Technical Information of China (English)

    邓丽娟; 王陆阳; 程昊; 黄文艺

    2016-01-01

    以硬脂酸、油酸及十二酸为改性剂,利用湿法活化工艺对纳米碳酸钙进行表面改性,并将其填充到酚醛树脂中。利用正交实验考察了改性时间、改性温度及改性剂用量对改性效果的影响,并确定了不同改性剂改性纳米碳酸钙的最佳条件。结果表明,油酸改性纳米碳酸钙的效果最好,其最佳改性条件为:改性时间30min,改性温度75℃,改性剂用量为纳米碳酸钙用量的4%(wt.)纳米碳酸钙经油酸改性后吸油值降低至22,比未改性纳米碳酸钙降低了71.05%,活化度接近100%。将改性纳米碳酸钙分散到酚醛树脂中,使它的耐水性能提高3倍以上。%Stearic acid,oleic acid and lauric acid as modifier,a wet activation process for surface modification of nanometer calcium carbonate,and filled phenolic resin.Orthogonal experiment to investigate the modification time,temperature and iMPact modified the amount of modification effect modifier and determine the optimum conditions of different modifiers modified nano calcium carbonate.The results showed that oleic acid modified nano calcium carbonate of the best,the best modification conditions:(.Wt) modification time 30min,modification temperature 75℃,modifier in an amount of 4% of the amount of nano-calcium carbonate nano calcium carbonate modified by oleic acid oil absorption value decreased to 22,than the unmodified nano calcium carbonate decreased 71.05%,activation of close to 100%.The modified nano calcium carbonate dispersed phenolic resin to make it water resistance increased by more than 3 times.

  2. 75 FR 39025 - Determination That ACTONEL (Risendronate Sodium) Tablets, 75 Milligrams, and ACTONEL WITH CALCIUM...

    Science.gov (United States)

    2010-07-07

    ... ACTONEL WITH CALCIUM (risendronate sodium and calcium carbonate (copackaged)) Tablets, 35 mg/500 mg, were... and calcium carbonate (copackaged)) Tablets, 35/500 mg, is the subject of NDA 21-823, held by Procter... (risendronate sodium) Tablets, 75 mg, nor ACTONEL WITH CALCIUM (risendronate sodium and calcium......

  3. 阳离子苯乙烯-丙烯酸酯对沉淀碳酸钙表面改性的研究%Surface Structure and Application of Precipitated Calcium Carbonate Modified with Cationic styrene/acrylate

    Institute of Scientific and Technical Information of China (English)

    谢亚桐; 裴继诚

    2011-01-01

    Surface modification of precipitated calcium carbonate with cationic styrene/acrylate was carried out. The surface structure and performance of modified precipitated calcium carbonate were characterized by DSC, FT-IR, Zeta potential, laser particle analyzer, sedimentation volume and contact angle and compared with unmodified precipitated calcium carbonate. According to the results of DSC and the spectra of FT-IR, the physical adsorption between surface modifiers and precipitated calcium carbonate took place. It was found that particle size of modified sample was smaller than unmodified one, sedimentation volume was larger and Zeta potential was higher. The results showed that the modified precipitated calcium carbonate is beneficial to improve physical properties, retention rate and hydrophobic ability of the paper when it is used as filler.%采用阳离子苯乙烯-丙烯酸酯乳液对沉淀碳酸钙进行改性,使用DSC、FT-IR、Zeta电位、激光粒度仪、沉降体积、接触角等对改性沉淀碳酸钙的表面结构及其性能进行表征,并与未改性沉淀碳酸钙进行对比分析.DSC和FT-IR分析表明,阳离子苯乙烯-丙烯酸酯乳液包覆在沉淀碳酸钙表面,影响其表面性质.研究结果说明,改性后沉淀碳酸钙的粒径变小、沉降体积增大、Zeta电位提高.以改性沉淀碳酸钙作为造纸填料,与添加未改性沉淀碳酸钙的相比,纸张的物理性能和憎水性能得到改善,纸张灰分含量提高.

  4. O carbonato de cálcio na desacidificação do vinho Isabel The calcium carbonate in the desacidification of Isabella wine

    Directory of Open Access Journals (Sweden)

    Luiz Antenor Rizzon

    2005-06-01

    Full Text Available A uva Isabel (Vitis labrusca é a cultivar de videira mais difundida na Região Vitícola da Serra Gaúcha. Entre outras finalidades, é utilizada para a elaboração de vinho tinto de mesa, o qual, geralmente, apresenta acidez elevada, devido ao teor de ácido tartárico livre. O objetivo do presente trabalho foi avaliar a influência de diferentes doses de carbonato de cálcio (0,0; 0,5; 1,0; 1,5; 2,0; 2,5 e 3,0 g L-1 na correção da acidez e na composição do vinho Isabel da Serra Gaúcha. O estudo foi realizado na Embrapa Uva e Vinho, em Bento Gonçalves - RS, na safra de 2002. O delineamento experimental utilizado foi o de blocos casualizados, com sete tratamentos e quatro repetições. As análises dos vinhos, realizadas dez dias após o tratamento, constaram da densidade, álcool, acidez total, acidez volátil, pH, açúcares redutores, extrato seco, extrato seco reduzido, cinzas, densidade ótica a 420, 520 e 620 nm, intensidade de cor e coloração, efetuadas através de métodos físico-químicos. O ácido tartárico foi determinado através da cromatografia líquida de alta eficiência (CLAE. O potássio e o cálcio foram analisados por espectrofotometria de absorção atômica. Além da redução da acidez do vinho Isabel, o carbonato de cálcio interferiu na cor, no extrato seco, nas cinzas e no teor de elementos minerais do vinho Isabel.Isabel grape (Vitis labrusca is the variety mostly spread in the Serra Gaúcha Region which is used, among other purposes, to elaborate red table wines. This wine usually presents high acidity, due to the level of free tartaric acid. The purpose of this work was to evaluate the effect of different doses of calcium carbonate in acidity and in the Isabel wine composition of the Serra Gaúcha region. The study carried out at Embrapa Uva e Vinho consisted of application in Isabel wine, from the 2002 vintage, different concentrations of calcium carbonate (0,0; 0,5; 1,0; 1,5; 2,0; 2,5 and 3,0 g L-1. The

  5. CO2碳酸化石灰岩酸解产物回收乙酸及副产沉淀碳酸钙%CO2 carbonation of calcium acetate derived from acidolysis of natural CaCO3 for recycling of acetic acid and production of precipitated calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    杨政; 岳海荣; 周向葛; 梁斌; 谢和平

    2014-01-01

    Acetic acid dissolution of limestone for formation of cavity is a kind of environmental approach to fabricating underground storage and preparing precipitated calcium carbonate. This process is an integrated technology consisting of acetic acid dissolution of limestone and CO2 carbonation of calcium acetate. The kinetics of limestone acidolysis with acetic acid was investigated. Orthogonal experiments were conducted with emphasis on operation conditions (i.e., concentration of calcium acetate, pressure of CO2, reaction temperature, and reaction time) of the carbonation reaction. The highest conversion of calcium acetate (23.13%) was achieved at the calcium acetate concentration of 0.631 mol·L-1, CO2 pressure of 5 MPa, reaction temperature of 80℃ and reaction for 50 min. The product of calcium carbonate was analyzed and could meet the requirements of Chinese national standard.%乙酸酸解石灰石造腔是一种建造地下储库同时环保地开采石灰岩制备沉淀碳酸钙的新方法。通过耦合乙酸酸解石灰石及酸解产物乙酸钙 CO2碳酸化的工艺过程,研究了乙酸酸解石灰岩的表面反应动力学和乙酸钙 CO2碳酸化的工艺技术条件。采用正交实验分析法,研究了CO2碳酸化反应中乙酸钙浓度、反应温度、CO2压力、反应时间对乙酸钙碳酸化反应制沉淀碳酸钙的影响,并通过正交实验确定了最优化操作条件。实验结果表明,乙酸酸解反应速率主要受乙酸浓度控制。CO2碳酸化反应在当乙酸钙溶液浓度为0.631 mol·L-1,CO2压力为5.0 MPa,温度为80℃,反应时间为50 min时CO2碳酸化效率达到最高(23.13%),生成的沉淀碳酸钙产品各项指标均符合中国国标优级要求。

  6. Calcium isotope constraints on the marine carbon cycle and CaCO3 deposition during the late Silurian (Ludfordian) positive δ13C excursion

    Science.gov (United States)

    Farkaš, Juraj; Frýda, Jiří; Holmden, Chris

    2016-10-01

    This study investigates calcium isotope variations (δ 44 / 40 Ca) in late Silurian marine carbonates deposited in the Prague Basin (Czech Republic), which records one of the largest positive carbon isotope excursion (CIE) of the entire Phanerozoic, the mid-Ludfordian CIE, which is associated with major climatic changes (abrupt cooling) and global sea-level fluctuations. Our results show that during the onset of the CIE, when δ13 C increases rapidly from ∼0‰ to ∼8.5‰, δ 44 / 40Ca remains constant at about 0.3 ± 0.1 ‰ (relative to NIST 915a), while 87Sr/86Sr in well-preserved carbonates are consistent with a typical Ludfordian seawater composition (ranging from ∼0.70865 to ∼0.70875). Such decoupling between δ13 C and δ 44 / 40Ca trends during the onset of the CIE is consistent with the expected order-of-magnitude difference in the residence times of Ca (∼106yr) and C (∼105yr) in the open ocean, suggesting that the mid-Ludfordian CIE was caused by processes where the biogeochemical pathways of C and Ca in seawater were mechanistically decoupled. These processes may include: (i) near shore methanogenesis and photosynthesis, (ii) changes in oceanic circulation and stratification, and/or (iii) increased production and burial of organic C in the global ocean. The latter, however, is unlikely due to the lack of geological evidence for enhanced organic C burial, and also because of unrealistic parameterization of the ocean C cycle needed to generate the observed CIE over the relatively short time interval. In contrast, higher up in the section where δ13 C shifts back to pre-excursion baseline values, there is a correlated shift to higher δ 44 / 40Ca values. Such coupling of the records of Ca and C isotope changes in this part of the study section is inconsistent with the abovementioned differences in oceanic Ca and C residence times, indicating that the record of δ 44 / 40Ca changes does not faithfully reflect the evolution of the oceanic Ca

  7. Fabrication of granular activated carbons derived from spent coffee grounds by entrapment in calcium alginate beads for adsorption of acid orange 7 and methylene blue.

    Science.gov (United States)

    Jung, Kyung-Won; Choi, Brian Hyun; Hwang, Min-Jin; Jeong, Tae-Un; Ahn, Kyu-Hong

    2016-11-01

    Biomass-based granular activated carbon was successfully prepared by entrapping activated carbon powder derived from spent coffee grounds into calcium-alginate beads (SCG-GAC) for the removal of acid orange 7 (AO7) and methylene blue (MB) from aqueous media. The dye adsorption process is highly pH-dependent and essentially independent of ionic effects. The adsorption kinetics was satisfactorily described by the pore diffusion model, which revealed that pore diffusion was the rate-limiting step during the adsorption process. The equilibrium isotherm and isosteric heat of adsorption indicate that SCG-GAC possesses an energetically heterogeneous surface and operates via endothermic process in nature. The maximum adsorption capacities of SCG-GAC for AO7 (pH 3.0) and MB (pH 11.0) adsorption were found to be 665.9 and 986.8mg/g at 30°C, respectively. Lastly, regeneration tests further confirmed that SCG-GAC has promising potential in its reusability, showing removal efficiency of more than 80% even after seven consecutive cycles.

  8. Calcium supplement: humanity's double-edged sword.

    Science.gov (United States)

    Bunyaratavej, Narong; Buranasinsup, Shutipen

    2011-10-01

    The principle aim of the present study is to investigate the dark side of calcium, pollutions in calcium preparation especially lead (Pb), mercury (Hg) and cadmium (Cd). The collected samples were the different calcium salts in the market and 18 preparations which were classified into 3 groups: Calcium carbonate salts, Chelated calcium and natural-raw calcium. All samples were analyzed for lead, cadmium and mercury by inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique, in house method based on AOAC (2005) 999.10 by ICP-MS. The calcium carbonate and the natural-raw calcium in every sample contained lead at 0.023-0.407 mg/kg of calcium powder. Meanwhile, the natural-raw calcium such as oyster, coral and animal bone showed amount of lead at 0.106-0.384 mg/kg with small amounts of mercury and cadmium. The chelated calcium such as calcium gluconate, calcium lactate and calcium citrate are free of lead.

  9. Precipitação de carbonato de cálcio para aplicação industrial Calcium carbonate precipitation for industrial application

    Directory of Open Access Journals (Sweden)

    Felipe Ventura Oliveira

    2009-06-01

    Full Text Available Esse trabalho apresenta os resultados experimentais da síntese de partículas de carbonato de cálcio precipitado (PCC depositadas sobre carbonato de cálcio natural (GCC, onde se variaram a relação [Ca]/[CO3]T inicial, a temperatura e o pH da solução aquosa de síntese e a concentração de coagulante (EDTA. As amostras foram caracterizadas por microscopia eletrônica de varredura, carbono total (TOC, área superficial específica (método BET, distribuição granulométrica e refletância de luz visível para se determinar o brilho. Os resultados foram comparados a amostras de referência utilizadas por indústrias de papel. O aumento do teor de EDTA favoreceu a coagulação das partículas de PCC entre si, aumentando o tamanho dos agregados. Em valores de pH entre 10 e 11, o PCC tendeu a coagular entre si e, em valores de pH entre 8 e 9, na superfície das partículas de GCC. Observou-se uma redução da densidade do material obtido. Os valores de área superficial específica do material estão dentro do aceitável pelas indústrias de papel e de plásticos.This work presents the experimental results for precipitated calcium carbonate (PCC synthesis over a ground calcium carbonate (GCC substrate. The parameters [Ca]/[CO3]T initial ratio, aqueous synthesis solution temperature, pH and coagulant concentration (EDTA were investigated. The samples were characterized by scanning electron microscopy (SEM, total carbon (TOC, specific surface area (BET method, particle size distribution and visible light reflectance (to measure the brightness of the samples. The results were compared with values from standard samples used in the paper industry. According to the experimental results, it was noted that an increase in the EDTA amount added to the pulp favored PCC homo-coagulation and also increased the size of the coagulum. PCC tends to homo-coagulate between pH 10 and 11, while it tends to precipitate over GCC particles between pH 8 and 9. A

  10. 纳米碳酸钙在非等温条件下热分解动力学及机理研究%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 20 K@min-1). The Coats andRedfern's equation was used to determine the apparent activation energy and the pre-exponential factors. Themechanism of thermal decomposition was evaluated using the master plots, Coats and Redfern's equation and thekinetic compensation law. It was found that the thermal decomposition property of nano-sized calcium carbonatewas 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 mechanismof one-dimensional phase boundary movement. The apparent activation energy of nano-sized calcium carbonate wasestimated to be 151kJ@mol-1 while the literature value for normal calcite was approximately 200kJ@mol-1. Theorder of magnitude of pre-exponential factors was estimated to be 109 s-1.

  11. Glacial to interglacial contrast in the calcium carbonate content and influence of Indus discharge in two eastern Arabian sea cores

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    , G.P., 1986. Late Quaternary carbon- ate sedimentation at the Sierra Leone Rise (eastern equatorial Atlantic Ocean). Mar. Geol., 70: 223-250. Cullen, J.L. and Prell, W.L., 1984. Planktonic foraminifera of northern Indian Ocean distribution...

  12. Histological evaluation of degradable guided bone regeneration membranes prepared from poly(trimethylene carbonate) and biphasic calcium phosphate composites

    NARCIS (Netherlands)

    Zeng, Ni; Leeuwen, van Anne; Bos, Ruud R.M.; Grijpma, Dirk W.; Kuijer, Roel

    2013-01-01

    In oral and maxillofacial surgery, guided bone regeneration using barrier membranes is an important strategy to treat bone defects. The currently used barrier membranes have important disadvantages. Barrier membranes prepared from resorbable poly(trimethylene carbonate) (PTMC) performed as well as c

  13. Histological Evaluation of Degradable Guided Bone Regeneration Membranes Prepared from Poly(trimethylene carbonate) and Biphasic Calcium Phosphate Composites

    NARCIS (Netherlands)

    Zeng, Ni; van Leeuwen, Anne; Bos, Ruud R.M.; Grijpma, Dirk W.; Kuijer, Roel

    2013-01-01

    In oral and maxillofacial surgery, guided bone regeneration using barrier membranes is an important strategy to treat bone defects. The currently used barrier membranes have important disadvantages. Barrier membranes prepared from resorbable poly(trimethylene carbonate) (PTMC) performed as well as c

  14. POLY(TRIMETHYLENE CARBONATE) AND BIPHASIC CALCIUM PHOSPHATE COMPOSITES FOR ORBITAL FLOOR RECONSTRUCTION : A FEASIBILITY STUDY IN SHEEP

    NARCIS (Netherlands)

    van Leeuwen, A. C.; Yuan, H.; Passanisi, G.; van der Meer, J. W.; de Bruijn, J. D.; van Kooten, T. G.; Grijpma, D. W.; Bos, R. R. M.

    2014-01-01

    In the treatment of orbital floor fractures, bone is ideally regenerated. The materials currently used for orbital floor reconstruction do not lead to the regeneration of bone. Our objective was to render polymeric materials based on poly(trimethylene carbonate) (PTMC) osteoinductive, and to evaluat

  15. The effect of calcium gluconate and other calcium supplements as a dietary calcium source on magnesium absorption in rats.

    Science.gov (United States)

    Chonan, O; Takahashi, R; Yasui, H; Watanuki, M

    1997-01-01

    The effects of commercially available calcium supplements (calcium carbonate, calcium gluconate, oyster shell preparation and bovine bone preparation) and gluconic acid on the absorption of calcium and magnesium were evaluated for 30 days in male Wistar rats. There were no differences in the apparent absorption ratio of calcium among rats fed each calcium supplement; however, the rats fed the calcium gluconate diet had a higher apparent absorption ratio of magnesium than the rats fed the other calcium supplements. Dietary gluconic acid also more markedly stimulated magnesium absorption than the calcium carbonate diet, and the bone (femur and tibia) magnesium contents of rats fed the gluconic acid diet were significantly higher than those of the rats fed the calcium carbonate diet. Furthermore, the weight of cecal tissue and the concentrations of acetic acid and butyric acid in cecal digesta of rats fed the calcium gluconate diet or the gluconic acid diet were significantly increased. We speculate that the stimulation of magnesium absorption in rats fed the calcium gluconate diet is a result of the gluconic acid component and the effect of gluconic acid on magnesium absorption probably results from cecal hypertrophy, magnesium solubility in the large intestine and the effects of volatile fatty acids on magnesium absorption.

  16. 偶联剂对聚丁烯-1/碳酸钙复合材料性能的影响%Inlfuences of Coupling Agents on Properties of Polybutene-1/Calcium Carbonate Composites

    Institute of Scientific and Technical Information of China (English)

    乔辉; 王树建; 刘维松; 丁筠

    2016-01-01

    采用硅烷、铝酸酯和钛酸酯偶联剂对碳酸钙进行表面处理,并以聚丁烯–1为基体制备了聚丁烯–1/碳酸钙复合材料,研究了这3种偶联剂对复合材料性能的影响。结果表明,钛酸酯和铝酸酯偶联剂对碳酸钙改性的效果最好,其中铝酸酯偶联剂改性的碳酸钙接触角最大,对复合材料的增韧效果最明显,当铝酸酯偶联剂改性的用量为碳酸钙的1.5%时,改性后的碳酸钙接触角可达162.4°,相应的复合材料缺口冲击强度由未改性时的21.5 kJ/m2提高至31.7 kJ/m2。对铝酸酯偶联剂改性碳酸钙填充的复合材料的结晶性能及微观结构进行了分析与表征,发现铝酸酯偶联剂改性碳酸钙能够提高聚丁烯–1的结晶度,在基体内形成紧密堆积的细小球晶;铝酸酯偶联剂改性碳酸钙在聚丁烯–1中的分散性较佳,无明显团聚现象,与聚丁烯–1界面结合能力强,能够吸收形变功,提高复合材料的韧性。%Polybutene-1/calcium carbonate composites were prepared with polybutene-1 as matrix by using different coupling agents including silane,titanate and aluminate for surface treatment of calcium carbonate. The effects of the three coupling agents on the properties of the composites were studied. The results show that the titanate and aluminate coupling agents have the best modi-fication effects for calcium carbonate,among them,the calcium carbonate modified by aluminate coupling agent has the maximum contact angle and the most obvious toughening effects. When the content of aluminate coupling agent is 1.5% of calcium carbonate mass,the contact angle of the modified calcium carbonate can reach 162.4° and the notched impact strength increases from 21.5 kJ/m2 (unmodified) to 31.7 kJ/m2. The crystallization and micro-structure of the compositesfilled with calcium carbonate modi-fied by aluminate coupling agent were analyzed,it is found that the crystallization

  17. Summertime calcium carbonate undersaturation in shelf waters of the western Arctic Ocean – how biological processes exacerbate the impact of ocean acidification

    Directory of Open Access Journals (Sweden)

    N. R. Bates

    2013-08-01

    Full Text Available The Arctic Ocean accounts for only 4% of the global ocean area, but it contributes significantly to the global carbon cycle. Recent observations of seawater CO2-carbonate chemistry in shelf waters of the western Arctic Ocean, primarily in the Chukchi Sea, from 2009 to 2011 indicate that bottom waters are seasonally undersaturated with respect to calcium carbonate (CaCO3 minerals, particularly aragonite. Nearly 40% of sampled bottom waters on the shelf have saturation states less than one for aragonite (i.e., Ωaragonite 3-secreting organisms, while 80% of bottom waters present had Ωaragonite values less than 1.5. Our observations indicate seasonal reduction of saturation states (Ω for calcite (Ωcalcite and aragonite (Ωaragonite in the subsurface in the western Arctic by as much as 0.8 and 0.5, respectively. Such data indicate that bottom waters of the western Arctic shelves were already potentially corrosive for biogenic and sedimentary CaCO3 for several months each year. Seasonal changes in Ω are imparted by a variety of factors such as phytoplankton photosynthesis, respiration/remineralization of organic matter and air–sea gas exchange of CO2. Combined, these processes either increase or enhance in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA on Ω in surface and subsurface waters, respectively. Future monitoring of the western Arctic shelves is warranted to assess the present and future impact of ocean acidification and seasonal physico-biogeochemical processes on Ω values and Arctic marine ecosystems.

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

    KAUST Repository

    Ha, J.

    2011-09-07

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

  19. Inhibition of gastric secretion by omeprazole and efficiency of calcium carbonate on the control of hyperphosphatemia in patients on chronic hemodialysis.

    Science.gov (United States)

    Hardy, P; Sechet, A; Hottelart, C; Oprisiu, R; Abighanem, O; Said, S; Rasombololona, M; Brazier, M; Moriniere, P; Achard, J M; Pruna, A; Fournier, A

    1998-07-01

    Contradictions exist in the literature regarding the effect of gastric secretion inhibition on phosphate absorption. In healthy controls, omeprazole would decrease the hyperphosphatemia or the hyperphosphaturia induced by an acute phosphate load, suggesting an inhibition of phosphate absorption. In chronic hemodialysis patients, gastric hypersecretion is associated with hyperphosphatemia, but inhibition of gastric hypersecretion by ranitidine in those receiving calcium carbonate (CaCO3) as a phosphate binder would paradoxically exacerbate their hyperphosphatemia. Because of these conflicting observations, we performed an open crossover study on 16 chronic stable hemodialyzed patients with a daily mean intake of 9.4+/-4 g of CaCO3, and we compared the plasmatic predialysis levels of phosphate, calcium, protides, bicarbonates, intact parathyroid hormone (PTH), urea, and creatininemia during 2 successive periods of 2 months, the first one without omeprazole and the second one with 20 mg omeprazole intake in the morning. Phosphatemia increased with omeprazole but not significantly from 1.80+/-0.38 to 1.89+/-0.42 mM whereas corrected calcemia decreased significantly (p = 0.04) from 2.41+/-0.18 to 2.36+/-0.16 mM as did bicarbonatemia from 26.7+/-3.5 to 25.7+/-3.1 mM (p omeprazole increases the plasmatic phosphate predialytic level but in a nonsignificant way. This increase may be explained by a slight but significant concomitant decrease of calcemia and bicarbonatemia. These results do not support the phosphate binding efficiency of CaCO3 being decreased by the inhibition of gastric acid secretion.

  20. Thermodynamics and Kinetics of Boron Removal from Metallurgical Grade Silicon by Addition of High Basic Potassium Carbonate to Calcium Silicate Slag

    Science.gov (United States)

    Wu, Jijun; Wang, Fanmao; Ma, Wenhui; Lei, Yun; Yang, Bin

    2016-06-01

    In this study, we investigated the thermodynamics and kinetics of boron removal from metallurgical grade silicon (MG-Si) using a calcium silicate slag containing a high basic potassium carbonate. The distribution of boron between slag and silicon was theoretically derived and the distribution coefficients ( L B) of boron with different compositions of CaO, SiO2, and K2CO3 in slag reagents were determined. The maximal value of L B reached 2.08 with a high basicity slag of 40 pctCaO-40 pctSiO2-20 pctK2CO3 (Λ = 0.73). The boron removal rates from MG-Si using CaO-SiO2 and CaO-SiO2-K2CO3 slags at 1823 K (1550 °C) were investigated in an electromagnetic induction furnace. The results showed that the boron concentration in MG-Si can be reduced from 22 to 1.8 ppmw at 1823 K (1550 °C) with 20 pct K2CO3 addition to calcium silicate slag, where the removal efficiency of boron reached 91.8 pct. The mass transfer coefficient ( β S) of boron in binary 50 pctCaO-50 pctSiO2 slag was 3.16 × 10-6 m s-1 at 1823 K (1550 °C) and was 2.43 × 10-5 m s-1 in ternary 40 pctCaO-40 pctSiO2-20 pctK2CO3 slag.

  1. Effect of Impurities on Conversion of Gypsum and Crystallization of Calcium Carbonate%杂质对磷石膏与碳酸铵反应及产物碳酸钙结晶的影响

    Institute of Scientific and Technical Information of China (English)

    丁光月; 李岳; 樊彩梅; 荆宏健; 冯军强

    2011-01-01

    用碳酸铵与磷石膏反应制取硫酸铵是磷石膏利用的有效途径之一,但磷石膏中的杂质会对石膏的转化过程及碳酸钙的结晶产生不利影响,进而影响碳酸钙的分离过程.以二水硫酸钙与碳酸铵为原料,以磷酸、硝酸镁、氟化钠及酸不溶物(AI)为杂质添加剂,研究了磷石膏复分解反应制取硫酸铵过程中杂质P2O5、Mg2+、F-及AI对硫酸钙转化率的影响,并对反应产物碳酸钙的结晶形态和晶型进行了SEM和XRD分析.结果表明,杂质的存在不仅降低了石膏中硫的转化率,而且使碳酸钙的晶型和晶体形状发生了变化,从而将影响产物的物性和过滤性能.%An effective approach of phosphogypsum utilization is the production of ammonium sulfate from ammonium carbonate and phosphogypsum. However, impurities in phosphogypsum have a negative impact on gypsum transformation process and the crystallization of calcium carbonate , and thus on the separation process of calcium carbonate. In this paper, calcium sulfate dihydrate and ammonium carbonate were used as raw materials, with phosphoric acid, magnesium nitrate, sodium fluoride and acid-insoluble material(AI) as impurity additives, to investigate the effects of the impurities P, Mg2+ , F- and AI on the conversion of calcium sulfate. The crystal line state and morphology of the product calcium carbonate were characterized by SEM and XRD analysis. The results show that the impurities not only affected the conversion of sulfur in gypsum, but also changed the type and shape of calcium carbonate crystal, consequently, affected the physical properties and filtration performance of products.

  2. Energy loss and charge state distribution of calcium ions in dense moderately coupled carbon plasma; Energieverlust und Ladungsverteilung von Calciumionen in dichtem, schwach gekoppeltem Kohlenstoffplasma

    Energy Technology Data Exchange (ETDEWEB)

    Ortner, Alex

    2015-07-15

    In this thesis the interaction of swift calcium ions (Energy: 3.5 MeV/u) with a dense and moderately coupled carbon plasma (Coupling parameter: Γ=0.1-0.5) is investigated. The plasma state is generated by heating a thin carbon foil volumetrically by thermal X-ray radiation. The thermal X-ray radiation itself is generated by the conversion of a high energy laser beam in a hohlraum cavity. Compared to earlier ion stopping experiments the electron density and the plasma coupling parameter could be increased by an order of magnitude. This work provides the first time experimental energy loss and charge state distribution data in this moderately coupled interaction regime. The thesis consists of a theoretical part where the ion beam plasma interaction is studied for a broad range of plasma parameters and an experimental part where the ion beam interaction with the hohlraum plasma target is measured. All the described experiments were carried out at the GSI Helmholtzzentrum fuer Schwerionenforschung in Darmstadt. This facility offers the unique possibility to combine a heavy ion beam from an accelerator with a high energy laser beam in one interaction chamber. An intense laser pulse (150 J of laser energy in 1 ns at λ{sub L}=527 nm) is focused inside a 600 μm diameter spherical cavity and generates a hot gold plasma that emits X-rays. The absorbed and reemitted radiation establishes a spatially uniform temperature distribution in the cavity and serves as an intense, isotropic X-ray source with a quasi-thermal spectral distribution. These thermal X-rays with a radiation temperature of T{sub r}=98±6 eV then propagate into a secondary cylindrical hohlraum (diameter: 1000 μm, length: 950 μm) where they volumetrically heat two thin carbon foils to the plasma state. The radiation temperature in the secondary hohlraum is T{sub r}=33±5 eV. This indirect laser heating scheme has the advantage that the whole sample volume is instantaneously heated and that the plasma is

  3. Behavior of POP-calcium carbonate hydrogel as bone substitute with controlled release capability: a study in rat.

    Science.gov (United States)

    Dewi, Anne Handrini; Ana, Ika Dewi; Wolke, Joop; Jansen, John

    2015-10-01

    Gypsum or calcium sulfate (CS) or plaster of Paris (POP) is considered as a fast degradable material that usually resorbs before the bone defect area is completely filled by new bone. In this study, the incorporation of CaCO3 hydrogel into POP in different compositions was proposed to enhance the bone biological activity of POP and to decrease its degradability. The mechanical and degradation properties of the various materials were characterized by in vitro analysis. Subsequently, the materials were inserted into cylindrically sized bone defects as created into the femoral condyle of rats and left in situ for 1, 4, and 8 weeks. Histological analysis of the retrieved specimens indicated that the addition of CaCO3 hydrogel into POP increased bone formation, angiogenesis and collagen density and resulted into faster bone formation and maturation. It was also confirmed that the degradation rate of the POP decreased by the addition of CaCO3 hydrogel. The in vivo findings did corroborate with the in vitro analysis. In conclusion, the incorporation of CaCO3 hydrogel provides a promising technology to improve the properties of POP, the oldest biomaterial used for bone grafting.

  4. Factors affecting calcium balance in Chinese adolescents.

    Science.gov (United States)

    Yin, Jing; Zhang, Qian; Liu, Ailing; Du, Weijing; Wang, Xiaoyan; Hu, Xiaoqi; Ma, Guansheng

    2010-01-01

    Chinese dietary reference intakes (DRIs) for calcium were developed mainly from studies conducted amongst Caucasians, yet a recent review showed that reference calcium intakes for Asians are likely to be different from those of Caucasians (Lee and Jiang, 2008). In order to develop calcium DRIs for Chinese adolescents, it is necessary to explore the characteristics and potential influencing factors of calcium metabolic balance in Chinese adolescents. A total of 80 students (15.1+/-0.8 years) were recruited stratified by gender from a 1-year calcium supplementation study. Subjects were randomly designed to four groups and supplemented with calcium carbonate tablets providing elemental calcium at 63, 354, 660, and 966 mg/day, respectively. Subjects consumed food from a 3-day cycle menu prepared by staff for 10 days. Elemental calcium in samples of foods, feces, and urine was determined in duplicates by inductively coupled plasma atomic emission spectrometry. The total calcium intake ranged from 352 to 1323 mg/day. The calcium apparent absorption efficiency and retention in boys were significantly higher than that in girls (68.7% vs. 46.4%, 480 mg/day vs. 204 mg/day, PCalcium retention increased with calcium intakes, but did not reach a plateau. Calcium absorption efficiency in boys increased with calcium intake up to 665 mg/day, and decreased after that. In girls, calcium absorption efficiency decreased with calcium intake. Calcium absorption efficiency increased within 1 year after first spermatorrhea in boys, but decreased with pubertal development in girls. Sex, calcium intake, age, and pubertal development were the most important determinants of calcium absorption (R(2)=0.508, Pcalcium intake, age, and pubertal development are important factors for calcium retention and absorption during growth, which should be considered for the development of calcium DRIs for Chinese adolescents.

  5. Novel injectable, self-gelling hydrogel-microparticle composites for bone regeneration consisting of gellan gum and calcium and magnesium carbonate microparticles.

    Science.gov (United States)

    Douglas, Timothy E L; Łapa, Agata; Reczyńska, Katarzyna; Krok-Borkowicz, Małgorzata; Pietryga, Krzysztof; Samal, Sangram Keshari; Declercq, Heidi A; Schaubroeck, David; Boone, Marijn; Van der Voort, Pascal; De Schamphelaere, Karel; Stevens, Christian V; Bliznuk, Vitaliy; Balcaen, Lieve; Parakhonskiy, Bogdan V; Vanhaecke, Frank; Cnudde, Veerle; Pamuła, Elżbieta; Skirtach, Andre G

    2016-11-21

    The suitability of hydrogel biomaterials for bone regeneration can be improved by incorporation of an inorganic phase in particle form, thus maintaining hydrogel injectability. In this study, carbonate microparticles containing different amounts of calcium (Ca) and magnesium (Mg) were added to solutions of the anionic polysaccharide gellan gum (GG) to crosslink GG by release of Ca(2+) and Mg(2+) from microparticles and thereby induce formation of hydrogel-microparticle composites. It was hypothesized that increasing Mg content of microparticles would promote GG hydrogel formation. The effect of Mg incorporation on cytocompatibility and cell growth was also studied. Microparticles were formed by mixing Ca(2+) and Mg(2+) and [Formula: see text] ions in varying concentrations. Microparticles were characterized physiochemically and subsequently mixed with GG solution to form hydrogel-microparticle composites. The elemental Ca:Mg ratio in the mineral formed was similar to the Ca:Mg ratio of the ions added. In the absence of Mg, vaterite was formed. At low Mg content, magnesian calcite was formed. Increasing the Mg content further caused formation of amorphous mineral. Microparticles of vaterite and magnesium calcite did not induce GG hydrogel formation, but addition of Mg-richer amorphous microparticles induced gelation within 20 min. Microparticles were dispersed homogeneously in hydrogels. MG-63 osteoblast-like cells were cultured in eluate from hydrogel-microparticle composites and on the composites themselves. All composites were cytocompatible. Cell growth was highest on composites containing particles with an equimolar Ca:Mg ratio. In summary, carbonate microparticles containing a sufficient amount of Mg induced GG hydrogel formation, resulting in injectable, cytocompatible hydrogel-microparticle composites.

  6. Performances of PVC filled with different kinds of calcium carbonate%不同品种碳酸钙填充PVC性能的研究

    Institute of Scientific and Technical Information of China (English)

    骆振福; 任晓玲; 乔军; 朱再胜; 李海滨; 代宁宁

    2012-01-01

    In order to investigate the effects of different kinds of calcium carbonate on performance of PVC/CaCO3 composite, a twin-screw extruder was used for extrusion and granulation, while an injection molding machine was used for model injection. The mechanical properties were tested by a universal testing machine and a simply supported beam impact testing machine. The microscopic morphology of fractured surface was observed by a SEM. The results show that the filling effects of nano-CaCO3 and coated CaCO3 are the best. The tensile strengths of PVC were increased by 19% and 17%, respectively. The non-notched impact strengths of PVC were increased by four times, which are 54. 05 kJ/m^2 and 51.67 kJ/m^2 , respectively. The notched impact strengths of PVC were increased by about three times, which are 28.94 kJ/m^2 and 22.59 kJ/m^2 , respectively. The filling effect of composite calcium is mediocre, and those of GCC and PCC are the worst. After being filled with many varieties of calcium carbonate, the flat outline of original PVC changed, nano-CaCO3 and coated CaCO3 formed many uneven and rounded surfaces, and GCC and PCC form more flaws and holes.%为了考察不同品种碳酸钙对PVC/CaCO3复合材料性能的影响,采用双螺杆挤出机挤出造粒、注塑机注塑成型,通过万能试验机和简支梁冲击试验机检测其力学性能,使用SEM观察断面微观形貌。结果表明:纳米钙和包覆钙的填充效果最好,分别使PVC的拉伸强度增加19%和17%,PVC的无缺口冲击强度增加4倍以上,分别达54.05和51.67kJ/m^2;PVC的缺口冲击强度增加3倍左右,分别达28.94和22.59kJ/m^2;复合钙的填充效果居中,重钙和轻钙最差。多种CaCO3填充PVC后,PVC原来平整的颗粒轮廓发生了变化,纳米钙和包覆钙形成了大量高低不平而圆润的表面,重钙和轻钙形成较多的裂纹和空穴。

  7. 大豆异黄酮联合碳酸钙调节去势大鼠骨代谢的研究%STUDY OF SOYBEAN ISOFLAVONES AND CALCIUM CARBONATE ON BONE METABOLISM IN OVARIECTOMIZED RATS

    Institute of Scientific and Technical Information of China (English)

    谭剑斌; 赵敏; 周轶琳; 陈瑞仪; 王凤岩; 胡帅尔

    2012-01-01

    [Objective] To observe the regulating effects of combining soybean isoflavones and calcium carbonate on bone metabolism in ovariectomized rats. [Methods] 60 female SD rats were divided randomly into sham, ovariectomized control group, calcium carbonate group, and three dosage groups, each group had 10 rats. Low, middle and high dosage groups were lavaged the test materials every day for 3 months { soybean isoflavones 4.8, 9.7, 29.0mg/kg BW, and calcium carbonate 25.5, 50.9, 152.8mg/kg BW) , and calcium carbonate group was given calcium carbonate (152.8mg/kg BW) in the same way. Body weight was recorded every week. At the end of the experiment, rats' serum AKP and serum calcium were measured, and femur were taken out to determine the bone density (middle and distal end point) and bone calcium content [Results] The femur bone density (distal side) of low and middle dosage groups were significantly higher than ovariectomized control group (P< 0.05), and bone calcium of low and high dosage groups were significantly higher than ovariectomized control group (P < 0.05). [Conclusion] Combining soybean isoflavones and calcium might increase bone density and bone calcium in o-variectomized rats.%[目的]观察大豆异黄酮联合碳酸钙对去势大鼠骨代谢的调节作用.[方法]将60只雌性SD大鼠随机分为6组,分别为假手术组、3个剂量组、碳酸钙组和去卵巢对照组,每组10只.假手术组单纯开腹,其余5组切除双例卵巢.低、中、高剂量组分别灌胃给予受试物(大豆异黄酮4.8、9.7、29.omg/kg BW,碳酸钙25.5、50.9、152.8mg/kg BW),碳酸钙组灌胃给予碳酸钙152.8 mg/kg BW,实验共3个月.每周记录一次体重.实验结束后测定大鼠血清碱性磷酸酶(AKP)和血清钙,取股骨检测股骨中点和远心端骨密度和骨钙含量.[结果]低、中剂量组大鼠股骨远心点骨密度与去卵巢对照组比较显著增加(P<0.05),低、高剂量组大鼠股骨骨钙含量与去卵巢

  8. A Cenozoic record of the equatorial Pacific carbonate compensation depth

    Digital Repository Service at National Institute of Oceanography (India)

    Palike, H.; Lyle, M.W.; Nishi, H.; Raffi, I.; Ridgwell, A; Gamage, K.; Klaus, A; Acton, G.; Anderson, L.; Backman, J.; Baldauf, J.; Beltran, C.; Bohaty, S.M.; Bown, P.; Busch, W.; Channell, J.E.T.; Chun, C.O.J.; Delaney, M.; Dewangan, P.; et al.

    of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation...

  9. Theoretical calculation model of calcium carbonate precipitation potential and its application%碳酸钙沉淀势理论计算模型及其应用

    Institute of Scientific and Technical Information of China (English)

    许仕荣; 赵伟; 王长平; 徐洪福

    2012-01-01

    Among many water chemical stability indexes, the calcium carbonate precipitation potential (CCPP) is the one that can quantitatively analyze the accurate dissolved or precipitated CaCO3. This paper deduced a calculation model of CCPP from theory, and offered a calculating solving by Matlab. Compared with other existing related softwares, the results of CCPP were closer to the experimental results than the results of other softwares, therefor it could be used to replace the experimental data for water quality chemical stability analysis.%水质化学稳定性评价指数较多,其中碳酸钙沉淀势(CCPP)是一个能定量分析CaCO3溶解或沉淀的精确指数.从理论上推导了CCPP计算模型,并基于Matlab计算求解.模型计算结果与已有相关软件的计算结果相比,该理论模型的计算值更接近试验结果,可以用其代替试验值进行水质化学稳定性分析.

  10. Antibacterial Activity of Ciprofloxacin-Encapsulated Cockle Shells Calcium Carbonate (Aragonite Nanoparticles and Its Biocompatability in Macrophage J774A.1

    Directory of Open Access Journals (Sweden)

    Tijani Isa

    2016-05-01

    Full Text Available The use of nanoparticle delivery systems to enhance intracellular penetration of antibiotics and their retention time is becoming popular. The challenge, however, is that the interaction of nanoparticles with biological systems at the cellular level must be established prior to biomedical applications. Ciprofloxacin–cockle shells-derived calcium carbonate (aragonite nanoparticles (C-CSCCAN were developed and characterized. Antibacterial activity was determined using a modified disc diffusion protocol on Salmonella Typhimurium (S. Typhimurium. Biocompatibilittes with macrophage were evaluated using the 3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and 5-Bromo-2′-deoxyuridine (BrdU assays. Transcriptional regulation of interleukin 1 beta (IL-1β was determined using reverse transcriptase-polymerase chain reaction (RT-PCR. C-CSCCAN were spherical in shape, with particle sizes ranging from 11.93 to 22.12 nm. Encapsulation efficiency (EE and loading content (LC were 99.5% and 5.9%, respectively, with negative ζ potential. X-ray diffraction patterns revealed strong crystallizations and purity in the formulations. The mean diameter of inhibition zone was 18.6 ± 0.5 mm, which was better than ciprofloxacin alone (11.7 ± 0.9 mm. Study of biocompatability established the cytocompatability of the delivery system without upregulation of IL-1β. The results indicated that ciprofloxacin–nanoparticles enhanced the antibacterial efficacy of the antibiotic, and could act as a suitable delivery system against intracellular infections.

  11. Antibacterial Activity of Ciprofloxacin-Encapsulated Cockle Shells Calcium Carbonate (Aragonite) Nanoparticles and Its Biocompatability in Macrophage J774A.1.

    Science.gov (United States)

    Isa, Tijani; Zakaria, Zuki Abu Bakar; Rukayadi, Yaya; Mohd Hezmee, Mohd Noor; Jaji, Alhaji Zubair; Imam, Mustapha Umar; Hammadi, Nahidah Ibrahim; Mahmood, Saffanah Khuder

    2016-05-19

    The use of nanoparticle delivery systems to enhance intracellular penetration of antibiotics and their retention time is becoming popular. The challenge, however, is that the interaction of nanoparticles with biological systems at the cellular level must be established prior to biomedical applications. Ciprofloxacin-cockle shells-derived calcium carbonate (aragonite) nanoparticles (C-CSCCAN) were developed and characterized. Antibacterial activity was determined using a modified disc diffusion protocol on Salmonella Typhimurium (S. Typhimurium). Biocompatibilittes with macrophage were evaluated using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 5-Bromo-2'-deoxyuridine (BrdU) assays. Transcriptional regulation of interleukin 1 beta (IL-1β) was determined using reverse transcriptase-polymerase chain reaction (RT-PCR). C-CSCCAN were spherical in shape, with particle sizes ranging from 11.93 to 22.12 nm. Encapsulation efficiency (EE) and loading content (LC) were 99.5% and 5.9%, respectively, with negative ζ potential. X-ray diffraction patterns revealed strong crystallizations and purity in the formulations. The mean diameter of inhibition zone was 18.6 ± 0.5 mm, which was better than ciprofloxacin alone (11.7 ± 0.9 mm). Study of biocompatability established the cytocompatability of the delivery system without upregulation of IL-1β. The results indicated that ciprofloxacin-nanoparticles enhanced the antibacterial efficacy of the antibiotic, and could act as a suitable delivery system against intracellular infections.

  12. Use of precision agriculture technologies in studying the relationships among soil pH, calcium carbonate equivalent, soybean cyst nematode population density, and soybean yield

    Science.gov (United States)

    Rogovska, Natalia

    Iron deficiency chlorosis (IDC) and soybean cyst nematode (SCN; Heterodera glycines) infestation are major factors that contribute to soybean (Glycine max Merr.) yield reduction in the Midwest. The IDC is often associated with soybean grown on high pH, calcareous soils. In addition, it was documented that SCN population density is higher in high pH soils. The objectives of this paper were to assess the proportion of within-field soybean yield and SCN variability that could be explained by soil pH, calcium carbonate equivalent (CCE), and a previously defined alkalinity stress index (ASI). Aerial images from 21 fields planted to SCN-resistant or susceptible soybean varieties were collected from 2001 through 2005 and used as a guide for soil and grain sampling. Ten to 16 sampling sites were selected on each field. Regression analyses within and across sites were used to study relationships between the measured variables. The SCN population density increased and yield decreased with increasing pH, CCE, and ASI across the fields. The percentage of yield variability across fields explained by soil pH, CCE, ASI, and SCN was 13%, 15%, 18%, and 1%, respectively, for resistant soybean varieties and 37%, 24%, 39%, and 10%, respectively, for susceptible varieties. The yield reduction due to high pH, CCE, and ASI was greater for SCN-susceptible varieties in field areas heavily infested with SCN.

  13. Comparison of calcium carbonate and aluminium hydroxide as phosphate binders on biochemical bone markers, PTH(1-84), and bone mineral content in dialysis patients

    DEFF Research Database (Denmark)

    Jespersen, B; Jensen, J D; Nielsen, H K;

    1991-01-01

    Bone mineral content, estimated by single-photon absorptiometry of the forearm, serum values of intact parathyroid hormone (PTH(1-84], osteocalcin, alkaline phosphatase, 1,25-dihydroxycholecalciferol (1,25(OH)2D3), and aluminium were determined during treatment with calcium carbonate (CaCO3...... 0.05), osteocalcin decreased (89% versus 117%, P less than 0.01), alkaline phosphatase decreased (92% versus 116%, P less than 0.05), and aluminium decreased (56% versus 189%, P less than 0.05). 1,25(OH)2D3 remained unchanged in both periods. No increase in soft-tissue calcification was demonstrated......) or aluminium hydroxide (Al(OH)3) in 11 dialysis patients participating in a randomised cross-over study. Each treatment period lasted 6 months. Serum phosphorus was maintained in the range 1.5-2.0 mmol/l. During Al(OH)3 treatment bone mineral content (BMC) decreased by 11% per half-year (mean), but only by 3...

  14. Effects of Biochar on Air and Water Permeability and Colloid and Phosphorus Leaching in Soils from a Natural Calcium Carbonate Gradient

    DEFF Research Database (Denmark)

    Kahawaththa Gamage, Inoka Damayanthi Kumari; Møldrup, Per; Paradelo Pérez, Marcos;

    2014-01-01

    in an agricultural field in Denmark with a calcium carbonate (CaCO3) gradient. The field comprised four reference plots and four plots to which biochar (birch wood pyrolyzed at 500°C) was applied at a rate of 20 t ha−1. Five undisturbed soil columns (10 cm diam., 8 cm height) were sampled from each plot 7 mo after...... biochar application, and a series of leaching experiments was conducted. The leachate was analyzed for tritium (used as a tracer), colloids, and phosphorus concentration. The results revealed that the presence of CaCO3 has resulted in marked changes in soil structure (bulk density) and soil chemical...... to be time dependent in soils with low CaCO3. Biochar-amended soils showed higher colloid and P release than reference soils. Field-scale variations in total colloid and P leaching reflected clear effects of changes in pH and ionic strength due to the presence of CaCO3. There was a linear relationship...

  15. Removal of Heavy Metal Ions by using Calcium Carbonate Extracted from Starfish Treated by Protease and Amylase

    Directory of Open Access Journals (Sweden)

    Kyong-Soo Hong

    2011-10-01

    Full Text Available CaCO3 extracted from starfish by using the commercial protein lyase having α-amylase, β-amylase, and protease is applied to remove heavy metal ions. The extracted CaCO3 shows excellent characteristics in removing heavy metal ions such as Cu2+, Cd2+, Pb2+, and Cr6+ compared with conventional materials such as crab shells, sawdust, and activated carbon except for removing Zn2+. SEM images reveal that the extracted CaCO33 has a good morphology and porosity. We characterize the removal efficiencies of the extracted CaCO3 for the heavy metal ions according to the concentrations, pH, temperatures, and conditions of empty bed contact times.

  16. Pilot experimental investigation on preparation of nanometer calcium carbonate with microstructure reactor%微反应器制备纳米碳酸钙的中试实验研究

    Institute of Scientific and Technical Information of China (English)

    丁涛; 郑长征; 陈绪奎

    2011-01-01

    利用微反应器制备纳米碳酸钙,得到平均粒径在25 ~ 55nm之间的超细CaCO3颗粒.研究了不同操作条件对颗粒粒径的影响,并使用XRD、TEM、比表面积仪(BET)等仪器对样品进行了分析.结果表明,在优化条件下制得的纳米CaCO3颗粒有很好的分散性能,同时CO2的利用率可达到80%以上.%Using the preparation of nanometer calcium carbonate microstructure reactor pilot experiment, Ultra-fine calcium carbonate particles with average crystal between 25-SSmn are produced by membrane dispersion precipitation technology. The influence of the different operating conditions on the particle size are investigated and the samples are analyzed by using XRD, TEM, specific surface area instrument (BET). The results show that the prepared nanometer calcium carbonate particles have good dispersibility under the optimum conditions,at the same time the utilization of CO2 up to 80%.

  17. Application of Modified Needle-shaped Nano-calcium Carbonate in PVC%改性针形纳米碳酸钙在PVC中的应用研究

    Institute of Scientific and Technical Information of China (English)

    焦其帅; 胡永琪; 陈瑞珍; 郝宏强; 庞秀

    2011-01-01

    Needle-shaped nano-calcium carbonate was modified and was introduced into poly(vinyl chloride)(PVC), and the mechanical properties of the composites were studied. The tensile and impact strength of the composites containing 5 % modified nano-calcium carbonate increased by 5 % and 10 %, respectively, compared with unfilled PVC. Scanning electron micrograph showed that the dispersioa of the modified nano-calcium carbonate was uniform, and fracture surface showed a ductile mode.%用市售改性剂对自制的针形纳米碳酸钙进行表面改性,然后将改性针形纳米碳酸钙填充到聚氯乙烯(PVC)材料中,研究了PVC复合材料的力学性能。与未填充改性针形纳米碳酸钙的PVC相比,添加5份改性针形碳酸钙的PVC复合材料拉伸强度提高了10%、冲击强度提高了7%;扫描电子显微镜分析显示,改性针形纳米碳酸钙在PVC体系中分散均匀,冲击试样断面和拉伸试样断面均呈现明显的韧性断裂特征。

  18. Calcium Electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha;

    2015-01-01

    BACKGROUND: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill...... efficacy-and normal cell sensitivity. METHODS: Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780......), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). RESULTS: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p

  19. Molecular mechanisms of crystallization impacting calcium phosphate cements

    OpenAIRE

    2010-01-01

    The biomineral calcium hydrogen phosphate dihydrate (CaHPO4·2H2O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite’s excellent biocompatibility, can be used to gr...

  20. Effects of calcium gluconate on the utilization of magnesium and the nephrocalcinosis in rats fed excess dietary phosphorus and calcium.

    Science.gov (United States)

    Chonan, O; Takahashi, R; Kado, S; Nagata, Y; Kimura, H; Uchida, K; Watanuki, M

    1996-08-01

    The effects of calcium gluconate on the utilization of magnesium and nephrocalcinosis in male Wistar rats made magnesium-deficient by adding excess dietary phosphorus (1.195 g of phosphorus/100 g of diet) and calcium (1.04 g of calcium/100 g of diet) were compared with the effects of calcium carbonate. The effects of dietary magnesium concentration on the magnesium status and nephrocalcinosis were also examined. Adding excess dietary phosphorus and calcium decreased the apparent magnesium absorption ratios and the concentrations of magnesium in the serum and femur and increased the deposition of calcium in the kidney, and the low magnesium condition (0.024 g of magnesium/100 g of diet) aggravated the deposition of calcium and the low magnesium status. The apparent magnesium absorption ratios and femur magnesium concentration in the rats fed a calcium gluconate diet (an equimolar mixture of calcium gluconate and calcium carbonate was used as a source of calcium) were significantly higher than in the rats fed a calcium carbonate diet (only calcium carbonate was used as a source of calcium), irrespective of dietary magnesium concentration. Dietary calcium gluconate lessened the accumulation of calcium in the kidney and increased the serum magnesium concentration compared with dietary calcium carbonate, when the rats were fed the normal magnesium diet (0.049 g of magnesium/100 g of diet) but not the low magnesium diet. We speculate that the increased utilization of magnesium by feeding the calcium gluconate diet to a limited extent prevented the low magnesium status and the severity of nephrocalcinosis caused by adding excess dietary phosphorus and calcium.

  1. Effect of lanthanum carbonate combined calcium acetate on calcium and phosphorus metabolism in patients with mai-ntenance hemodialysis%碳酸镧联合醋酸钙对维持性血液透析患者钙磷代谢的影响

    Institute of Scientific and Technical Information of China (English)

    汪嘉莉; 杨晗; 张林; 廖丹; 张逢莲

    2016-01-01

    Objective To investigate the effect of lanthanum carbonate combined calcium acetate in maintaining he-modialysis patients.Methods Seventy-eighy cases of maintenance hemodialysis patients in Mianyang Central Hospital from December 2014 to January 2009 were randomly divided into 3 groups:lanthanum carbonate group (16 cases), calcium acetate group (37 cases) and lanthanum carbonate group ( combined group 25 cases) .Treatment of 12 weeks, compared the 3 groups of patients'calcium and phosphorus metabolism.Results ( 1 ) Calcium and phosphorus metabolism: Compared with before treatment, serum calcium levels after 12 weeks in the three groups showed no significant changes, the difference was not statis-tically significant ( P >0.05), serum phosphorus, serum calcium and phosphorus product parathyroid hormone (iPTH) were significantly lower, the difference was statistically significant (lanthanum carbonate group:t =5.88,2.22,6.20,calcium ace-tate group:t =5.11,3.28,6.02, combined group:t =10.08,6.90,9.33, P 0.05);among the three groups, before and after treatment, the indicators showed no significant differences ( P >0.05).(3)Ultrasound:3 groups of patients before and after treatment of carotid intimal thickening and plaque formation ratio's difference did not show statistically significant ( P >0.05).Conclusion Lanthanum carbonate combined with calcium acetate can be used in the treatment of chronic kidney dis-ease hemodialysis patients with high phosphorus, it can effectively reduce the level of serum phosphorus and PTH.%目的 观察碳酸镧联合醋酸钙对维持性血液透析患者钙磷代谢的影响.方法 选取2009年1月—2014年12月绵阳市中心医院维持性血液透析高磷血症患者78例,采用简单随机化分组法分为碳酸镧组(16例)、醋酸钙组(37例)和碳酸镧联合醋酸钙组(联合组,25例).治疗12周,比较3组患者的钙磷代谢情况.结果 (1)钙磷代谢指标:与治疗前比较,治疗12周后3组患者血钙水平均

  2. 复方碳酸钙泡腾颗粒剂人体相对生物利用度研究%The study on relative bioavailability of compound calcium carbonate granules in Human

    Institute of Scientific and Technical Information of China (English)

    张学农; 陶亮; 王新玲; 周云龙

    2001-01-01

    OBJECTIVE:To study the relative bioavailability of compound calcium carbonate granules in Human.METHODS:Comparing with caltrate D 600 tablets,the cumulate amount of calcium in urine was determined with atomic absorption spectrophotometer after taking compound calcium carbonate granules and caltrate D for 12 volunteers.RESULTS:The average excreteive calcium qualities in urine in three gorups,compound calcium carbonate granules and caltrate D tablets and blankness volunteer groups,were orderly 125.21±26.60,124.49±36.60 and 67.31±19.39mg in 12 hours.Comparing with the space group,the increasing amount of calcium in extracted urine were 57.97±24.24mg in compound calcium carbonate granules and 57.31±32.68mg in caltrate D tablets groups.The releative bioavaillability of compound calcium carbonate granules in human was 101.5%.There was no remarkable differentias between two groups(P>0.05).CONCLUSION:According to the urinous drugs excretive rate methods,there was similar absorption rate between two test drugs.%目的:考察复方碳酸钙颗粒剂的人体相对生物利用度。方法:以钙尔奇D600为对照品,原子吸收分光光度法测定12名自愿受试者口服复方碳酸钙颗粒剂后的尿钙排泄量。结果:在12h内,复方碳酸钙颗粒剂组,钙尔奇D组和空白对照组的平均尿钙排泄总量分别为125.21±26.60,124.49±36.60和67.24±19.39mg。集尿期内复方碳酸钙颗粒剂和钙尔奇D尿钙排泄总量的净增值分别为57.97±24.24和57.31±32.68mg。复方碳酸钙颗粒剂的相对生物利用度101.50%。结论:两种药物的吸收程度相当,无统计学差异(P>0.05),由尿钙排泄速率推测,复方碳酸颗粒剂的吸收速度与钙尔奇D片一致。

  3. Overbased Calcium sulfonate Detergent Technology Overview

    Institute of Scientific and Technical Information of China (English)

    MA Qing-gao; MUIR Ronald J.

    2009-01-01

    Overbased calcium sulfonate is used widely as detergent in automotive and marine lubricants, as well as various industrial oil applications. In this paper, the process to produce overbased calcium sulfonate is overviewed. The sulfonate structure and molecular weight and its molecular weight distribution, the enclosed calcium carbonate nanoparticle size and crystalline structure, properties of the carrier oil, all influence its properties, such as stability, viscosity, and detergency of the system.

  4. Energy loss and charge state distribution of calcium ions in dense moderately coupled carbon plasma; Energieverlust und Ladungsverteilung von Calciumionen in dichtem, schwach gekoppeltem Kohlenstoffplasma

    Energy Technology Data Exchange (ETDEWEB)

    Ortner, Alex

    2015-07-15

    In this thesis the interaction of swift calcium ions (Energy: 3.5 MeV/u) with a dense and moderately coupled carbon plasma (Coupling parameter: Γ=0.1-0.5) is investigated. The plasma state is generated by heating a thin carbon foil volumetrically by thermal X-ray radiation. The thermal X-ray radiation itself is generated by the conversion of a high energy laser beam in a hohlraum cavity. Compared to earlier ion stopping experiments the electron density and the plasma coupling parameter could be increased by an order of magnitude. This work provides the first time experimental energy loss and charge state distribution data in this moderately coupled interaction regime. The thesis consists of a theoretical part where the ion beam plasma interaction is studied for a broad range of plasma parameters and an experimental part where the ion beam interaction with the hohlraum plasma target is measured. All the described experiments were carried out at the GSI Helmholtzzentrum fuer Schwerionenforschung in Darmstadt. This facility offers the unique possibility to combine a heavy ion beam from an accelerator with a high energy laser beam in one interaction chamber. An intense laser pulse (150 J of laser energy in 1 ns at λ{sub L}=527 nm) is focused inside a 600 μm diameter spherical cavity and generates a hot gold plasma that emits X-rays. The absorbed and reemitted radiation establishes a spatially uniform temperature distribution in the cavity and serves as an intense, isotropic X-ray source with a quasi-thermal spectral distribution. These thermal X-rays with a radiation temperature of T{sub r}=98±6 eV then propagate into a secondary cylindrical hohlraum (diameter: 1000 μm, length: 950 μm) where they volumetrically heat two thin carbon foils to the plasma state. The radiation temperature in the secondary hohlraum is T{sub r}=33±5 eV. This indirect laser heating scheme has the advantage that the whole sample volume is instantaneously heated and that the plasma is

  5. Effect of Free Calcium Carbonate on Soil pH and Enzyme Activities%土壤中游离碳酸钙对土壤pH及酶活性的影响

    Institute of Scientific and Technical Information of China (English)

    贺婧; 赵亚平; 关连珠

    2011-01-01

    游离碳酸钙是我国北方石灰性土壤的重要组成物质,密切影响着土壤的物理、化学、生物学性质以及土壤的环境学效应,但是将游离碳酸钙作为土壤重要组成物质而探讨其对土壤生物学特性尤其是对土壤酶活性的影响研究较少.通过研究探讨碳酸钙与土壤pH值之间的定量关系以及碳酸钙含量对土壤酶活性的影响,为进一步研究游离碳酸钙对土壤生物学性质及土壤环境效应的影响提供理论参考.采用实验室模拟培养及分析测试的方法进行试验.结果表明:土壤pH随游离碳酸钙含量的增加而增加,趋近于达到该试验条件下的最大值(pH=8.19),但并非呈直线相关,而是呈非线性相关关系.中性磷酸酶活性和转化酶随碳酸钙浓度的增加而降低,其最大降低幅度分别为0.402个活性单位和3.16个活性单位.碳酸钙含量与土壤pH值之间呈非线性相关关系.碳酸钙对土壤中性磷酸酶和转化酶活性产生极显著的抑制作用,对脲酶活性呈现低含量促进而高含量抑制的作用,而对过氧化氢酶则产生极显著的促进作用.%Free calcium carbonate is the important substance of calcareous soil component in North China, and has closely effect on the physical, chemical and biochemical properties of soil and the effect of soil environment. So this experiment aims to provide theory reference for further study on the effect of free calcium carbonate on soil microbial character and soil environmental. The study used the method of indoor simulated culture and analysis. Soil pH gradually rose with the increase of free calcium carbonate content, and approached the maximum on this experiment conditions (pH=8.19). The relation was not linear relation. Soil neutral phosphatase and invertase gradually decreased with the rose of calcium carbonate, the max-decreased ranges respectively were 0.402 and 3.16 activity unit. Soil pH with the contents of free calcium

  6. 草浆白泥碳酸钙的性能及应用%Research on the Application of Calcium Carbonate Prepared from Chemical Recovery in Straw Pulping as Filler

    Institute of Scientific and Technical Information of China (English)

    夏新兴; 杜明珠

    2012-01-01

    The physical characteristics of conventional lime mud from straw pulping process, the refined lime mud and the commercial precipitated calcium carbonate were investigated, and the potential of applying these mineral materials as filler was also studied. The results showed the refined lime mud with an average particle size of 6.36 μm, and about 82% particles less than 10 μm, which were similar to commercial precipitated calcium carbonate. However, the conventional lime mud had a wide size distribution, with an average particle size of 12.78 μm, and 66% particles above 10μm. The refined lime mud had higher oil absorption and lower sedimentation volume. The effect of conventional lime mud and refined lime mud loading on paper properties were also investigated and compared with that of commercial precipitated calcium carbonate loading. The results showed that loading with refined lime mud and commercial precipitated calcium carbonate could increase paper whiteness, on the contrary, loading with conventional lime mud decreased the paper whiteness. The refined lime mud was found to impart good opacity, and the commercial precipitated calcium carbonate took the second place for improving opacit . The paper loaded with refined lime mud improved apparently in sizing effect and strength properties compared with conventional lime mud. Thus it can be concluded that the refined lime mud can take place of commercial precipitated calcium carbonate as filler, while conventional lime mud cannot be accepted as filler.%对比分析了传统草浆白泥碳酸钙、精制草浆白泥碳酸钙及商品轻质碳酸钙的物理性能及其作为填料对纸张性能的影响研究发现,精制草浆白泥碳酸钙平均粒径为6.36μm,10μm以下粒径约占82%,其粒径与商品轻质碳酸钙相近;而传统草浆白泥碳酸钙粒度分布范围宽,10μm以上粒径的约占66%,平均粒径达12.78μm。精制草浆白泥碳酸钙吸油值高、沉降体积小

  7. Calcium and bones

    Science.gov (United States)

    Bone strength and calcium ... calcium (as well as phosphorus) to make healthy bones. Bones are the main storage site of calcium in ... your body does not absorb enough calcium, your bones can get weak or will not grow properly. ...

  8. Calcium Test

    Science.gov (United States)

    ... if a person has symptoms of a parathyroid disorder , malabsorption , or an overactive thyroid. A total calcium level is often measured as part of a routine health screening. It is included in the comprehensive metabolic panel (CMP) and the basic metabolic panel (BMP) , ...

  9. Propriedades de compósitos híbridos de borracha nitrílica, fibras de sisal e carbonato de cálcio Properties of nitrile rubber, sisal fiber and calcium carbonate hybrid composites

    Directory of Open Access Journals (Sweden)

    Marco A. Iozzi

    2004-06-01

    Full Text Available Neste trabalho, estudou-se a influência do teor de carbonato de cálcio nas propriedades mecânicas e térmicas da borracha nitrílica, e do comprimento das fibras de sisal nas propriedades mecânicas dos compósitos de borracha nitrílica/fibras de sisal, e borracha nitrílica/carbonato de cálcio/fibras de sisal. Os materiais foram caracterizados através de ensaios mecânicos de resistência à tração, microscopia eletrônica de varredura (MEV, e termogravimetria (TG. O melhor desempenho mecânico dos compósitos com as fibras curtas aleatoriamente distribuídas foi obtido para o comprimento das fibras de 6 mm, e teor de carbonato de 67 pcr. A análise térmica mostrou que os compósitos são estáveis até cerca de 300 °C. Os resultados mostraram que os materiais obtidos possuem uma boa relação custo/benefício tornando promissora sua utilização.In this work, nitrile rubber with sisal fibers composites and nitrile rubber with calcium carbonate and sisal fibers composites were developed. The influence from the calcium carbonate amount and size of sisal fibers on the composite properties was studied. The composites, with short fibers randomly distributed, were characterized by mechanical analysis, scanning electron microscopy (SEM, and thermogravimetric analysis (TGA. The optimal size of sisal fibers to reinforce the nitrile matrix was 6 mm. The ideal volume of calcium carbonate was 67 phr. TGA analysis demonstrated that the composites are stable up to 300 °C. The materials developed have a good cost/benefits relation, being therefore promising their utilization.

  10. Calcium carbonate with magnesium overdose

    Science.gov (United States)

    ... K. General approach to the poisoned patient. In: Marx JA, Hockberger RS, Walls RM, eds. Rosen's Emergency ... 147. Pfennig CL, Slovis CM. Electrolyte disorders. In: Marx JA, Hockberger RS, Walls RM, eds. Rosen's Emergency ...

  11. Hydroxypropyl-β-cyclodextrin functionalized calcium carbonate microparticles as a potential carrier for enhancing oral delivery of water-insoluble drugs

    Directory of Open Access Journals (Sweden)

    Zhang L

    2015-04-01

    Full Text Available Lihua Zhang,1 Wufu Zhu,2 Qisi Lin,1 Jin Han,1 Liqun Jiang,1 Yanzhuo Zhang1,3 1Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, People’s Republic of China; 2School of Pharmacy, Jiangxi Science and Technology Normal University, Nanchang, People’s Republic of China; 3Department of Pharmaceutics, School of Pharmacy, Xuzhou Medical College, Xuzhou, People’s Republic of China Abstract: The objective of the present study was to demonstrate that a novel hydroxypropyl-β-cyclodextrin functionalized calcium carbonate (HP-β-CD/CC based amorphous solid dispersion (ASD can be used to increase the solubility and oral bioavailability of water-insoluble drugs. Irbesartan (IRB was selected as a model compound and loaded into the nanoporous HP-β-CD/CC matrix using an immersion method. The IRB-loaded HP-β-CD/CC formulation was characterized by various analytical techniques, such as specific surface area analysis, scanning electron microscopy (SEM, dynamic light scattering (DLS, powder X-ray diffraction (PXRD, and differential scanning calorimetry (DSC. Analyses with PXRD and DSC confirmed that IRB was fully converted into the amorphous form in the nanopores of HP-β-CD/CC. From the solubility and dissolution tests, it was observed that the aqueous solubility and dissolution rate of IRB-loaded HP-β-CD/CC were increased significantly compared with those of pure IRB and IRB-loaded mesoporous silica. Likewise, the IRB-loaded HP-β-CD/CC formulation exhibited better absorption compared with that of the commercially available IRB capsules in beagle dogs. The mean peak plasma concentration (Cmax and the area under the mean plasma concentration–time curve (AUC[0→48] of IRB-loaded HP-β-CD/CC were 1.56- and 1.52-fold higher than that of the commercial product, respectively. Furthermore, the IRB-loaded HP-β-CD/CC formulation exhibited excellent stability against re-crystallization. These results clearly

  12. 碳酸钙的制备及其分散体系的流变性能%Preparation of calcium carbonate by mechanochemical processing and its rheological property of suspension

    Institute of Scientific and Technical Information of China (English)

    谢元彦; 杨海林; 阮建明; 白波

    2011-01-01

    利用固态置换反应,在机械化学条件下制备碳酸钙,即把氯化钙和碳酸钠混合,在常温下机械球磨,然后把粉末混合物加热至350℃保温1h,使反应完全,最后通过洗涤去除副产品,即得到方解石型纳米碳酸钙.在反应过程中,通过X线衍射对不同反应时间粉末混合物进行分析,利用扫描电镜(SEM)对碳酸钙粉末进行表征,并采用AR2000流变仪对CaCO3-PEG分散体系的流变性进行测定.研究结果表明,机械化学法能够制备单一形貌的纳米级碳酸钙粉末;CaCO3-PEG分散体系具有剪切增稠现象,而且CaCO3体积分数越高越明显.%A solid-state displacement reaction was induced to synthesize calcium carbonate during mechanochemical processing. Calcium chloride and sodium carbonate were mixed together and milled at room temperature, and then the as-milled powder was heat-treated at 350℃ for 1 h. The calcite nanoparticles were gained by removing the by-product through a simple washing process. The mixture was analyzed by X-ray diflractrometry(XRD) at different reaction time, the calcium carbonate powder was characterized by scanning electron microscope(SEM) and the rheological property of CaCO3-PEG suspension was investigated by AR2000 stress controlled rheometer. The results show that single crystal calcium carbonate nanoparticles can be prepared by mechanochemical processing, and the CaCO3-PEG suspension has shear-thickening behavior when it is sheared. It is illustrated that the higher volume fraction of CaCO3, the more obvious the phenomenon.

  13. Modification of calcium carbonate by polyether coupling and the properties of CaCO3/PP material%聚醚偶联剂改性碳酸钙及CaCO3/PP复合材料的性能

    Institute of Scientific and Technical Information of China (English)

    曲燕; 杨大伟; 李乾斌; 程如清; 魏鑫

    2013-01-01

    自制了偶联剂四氢呋喃均聚醚(PTHF),并用其对轻质碳酸钙表面进行处理,将处理后的碳酸钙填充到聚丙烯塑料中,探讨了新型改性剂对复合材料力学性能的影响.结果表明,四氢呋喃均聚醚能够使碳酸钙的吸油值降低到22%,接触角降低到68.6°.改性后的碳酸钙填充进聚丙烯,能在一定程度上缓解拉伸强度的下降趋势,使复合材料的断裂伸长率达到28.47%、冲击强度达到6.7 kJ/m2.SEM观察四氢呋喃均聚醚添加前后复合材料的断面形态,表明碳酸钙在聚丙烯中分散良好.%Homemade agent-tetrahydrofuran polyether (PTHF) was used to treat the surface of the precipitated calcium carbonate.The impacts of surface modified CaCO3 with coupling agent of PTHF on CaCO3/PP mechanical properties of composite material were studied.The result showed that tetrahydrofuran polyether was able to make the oil absorption of calcium carbonate reduced to 22% and the contact angle decreased to 68.6°.CaCO3 with PTHF filling in the polypropylene can also alleviate the downward trend of the tensile strength to a certain extent,making the elongation at break of composites reached 28.47% and the impact strength of the composites reached 6.7 kJ/m2.Calcium carbonate with PTHF dispersed better in polypropylene than calcium carbonate by scanning electron microscopy (SEM).

  14. Viability study on using calcium carbonate for the boron adsorption process in waste waters; Estudio de viabilidad del proceso de adsorcion de boro de aguas residuales con carbonato calcico

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Guerreiro, M. J.; Munoz Camacho, E.; Bernal Pita da Veiga, M. B.

    2009-07-01

    This study evaluates how viable it is to employ calcium carbonate for the boron adsorption process in waters that could be contaminated by this element. A residue form mussel shells-abundant in Galicia, northwestern Spain, was used. The data gathered from the experiments show that the performance of the boron adsorption within the sample is below 2%. Despite the inferior data obtained, the general aim was reached. An attempt was made to find solutions to the environmental problem caused by the residues mentioned above. (Author) 11 refs.

  15. 磷石膏-碳铵-氨水球磨制备硫酸铵和碳酸钙%Ammonium Sulfate and Calcium Carbonate Prepared by Ball-milling from Phosphogypsum-Ammonium Bicarbonate-Ammonia Water

    Institute of Scientific and Technical Information of China (English)

    李娜; 邓跃全; 董发勤; 罗绍东; 李珊珊; 彭宝瑶

    2013-01-01

    Ammonium sulfate and calcium carbonate were prepared using phosphogypsum, ammonium bicarbonate and ammonia water as raw materials by ball-milling technique. The optimum conditions were explored through orthogonal test, the major elements and phase composition of two kinds of products were analyzed by XRF and XRD, and the grain size distribution and poisonous elements of calcium carbonate were determined using laser particle size analyzer and ICP. The analysis results showed that the optimum technological conditions were as follows: the liquid-solid ratio was 0.5, the response time was 45 min, the ball-material ratio was 3:1, rotational speed was 600 r/min, and the average conversion reaction was up to 97.95%; the product quality of ammonium sulfate reached the standard of byproduct ammonium sulfate, poisonous and harmful elements contents of calcium carbonate were far lower than quality criteria of soil environment allows. Preparation of ammonium sulfate and calcium carbonate from phosphogypsum by ball-milling achieved the purpose of effectively using phosphogypsum.%  以磷石膏、碳酸氢铵和氨水为原料,采用球磨工艺制备硫酸铵和碳酸钙.通过正交试验设计,探索磷石膏球磨制备硫酸铵和碳酸钙的最佳工艺条件,采用 XRF 和 XRD 分析了2种产物的化学组成及物相组成,采用激光粒度仪和 ICP 分别测定了碳酸钙的粒度分布及有毒有害元素含量.结果表明,球磨制备硫酸铵和碳酸钙适宜的工艺条件为:液固比0.5,反应时间45 min,球料比3∶1,转速600 r/min,反应的平均转化率达97.95%;硫酸铵产品质量达到了副产硫酸铵标准,碳酸钙中有毒有害元素的含量远低于土壤环境质量标准要求.磷石膏球磨制备硫酸铵和碳酸钙,实现了磷石膏的高效利用.

  16. 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.

  17. Polymorph transformation and formation mechanism of calcium carbonate during reactive extraction-crystallization process%反应-萃取-结晶过程制备碳酸钙的晶型转变与结晶机理

    Institute of Scientific and Technical Information of China (English)

    李云钊; 宋兴福; 孙玉柱; 孙泽; 于建国

    2015-01-01

    Distiller waste produced in ammonia-soda process restricts the development of soda industry. In this study, the polymorph transformation and crystallization mechanism of calcium carbonate in the reactive extraction-crystallization coupled process were investigated. The results show that carbon dioxide (CO2) is first absorbed by the organic phase and then transferred to the aqueous phase. Calcium bicarbonate is generated and then decomposed into amorphous calcium carbonate rapidly. Temperature has a significant effect on the polymorph of calcium carbonate. Needle-like aragonite forms preferentially at higher temperatures and spherical and flower-like vaterite forms preferentially at lower temperatures. Both of them will finally transform into rhombic calcite by dissolution and recrystallization. At 20℃, the formation of new vaterite and its transformation to calcite occur simultaneously in the coupled process. The content of vaterite in the particles increases with the increase of CO2 concentration.%氨碱法制碱过程中产生的大量蒸氨废液制约了纯碱工业的发展。本文对反应-萃取-结晶耦合工艺产物碳酸钙的晶型转变和结晶机理进行了研究。结果表明,在此耦合过程中,二氧化碳优先被有机相吸收,然后传递到水相进行反应,首先生成的是碳酸氢钙,之后迅速分解为无定形碳酸钙。温度对碳酸钙晶型影响显著,温度较高时,无定形碳酸钙优先转变为针状文石;温度较低时,无定形碳酸钙优先转变为球状球霰石。随后文石和球霰石均会通过溶解-重结晶作用逐渐转变为稳定的菱形方解石。常温下,反应过程中同时进行着新的球霰石的生成和球霰石转变为方解石两个过程,参与反应的二氧化碳浓度越高,晶体中球霰石的含量越高。

  18. Follow up of low calcium dialysate and lanthanum carbonate in peritoneal dialysis patients with calcium and phosphorus metabolism disorder%腹膜透析钙磷代谢紊乱患者使用低钙腹膜透析液及碳酸镧的随访分析

    Institute of Scientific and Technical Information of China (English)

    夏阳阳; 万骋; 张庆燕; 汤天凤; 张苗

    2016-01-01

    目的:调查腹膜透析患者血钙(Ca)、血磷(P)及甲状旁腺激素的情况,并观察使用低钙腹膜透析液结合药物治疗高 Ca、高 P 及甲状旁腺功能亢进(甲旁亢)的效果。方法统计2010年以后在南京鼓楼医院规律随访一直使用普通钙腹膜透析液(钙离子浓度为1.75 mmol·L -1)1年以上时间的腹膜透析患者血 Ca、血 P 及全段甲状旁腺激素(iPTH)水平。根据患者血Ca、血 P 及 iPTH 水平挑选120例高 Ca、高 P、甲旁亢患者,随机平均分为 A、B 两组,A 组改用低钙腹膜透析液(钙离子浓度为1.25 mmol·L -1),B 组改用低钙腹膜透析液的同时加用碳酸镧降磷治疗。结果6个月后,A 组与之前比较,血 Ca 降低,血P、iPTH 升高(P <0.05),B 组与之前比较血 Ca、血 P、iPTH 降低(P <0.05),半年后 B 组与 A 组比较血 Ca、血 P、iPTH 降低(P<0.05)。结论对于出现高 Ca、高 P 及高 iPTH 的患者建议使用低钙腹膜透析液,同时必须使用碳酸镧加强降磷治疗。%Objective To investigate blood calcium,phosphate and intact parathyroid hormone(iPTH)in peritoneal dialysis patients treated at The Affiliated Drum Tower Hospital of Nanjing University Medical School,and to observe the efficacy of high blood calcium, phosphate and iPTH by using low calcium dialysate with medicine.Methods We investigated blood calcium,phosphate and iPTH in peritoneal dialysis patients who were regularly followed up at least one year using regular calcium dialysate (calcium concentration was 1.75mmol/L).One hundred and twenty patients with high calcium phosphorus and iPTH were selected,who were randomized into group A,and group B.Group A with sixty patients changed to low calcium dialysate (calcium concentration was 1.25 mmol·L -1 ), while group B with sixty patients changed to low calcium dialysate and used lanthanum carbonate at the same time.Results After six

  19. Osteoclastic resorption of biomimetic calcium phosphate coatings in vitro.

    NARCIS (Netherlands)

    Leeuwenburgh, S.C.G.; Layrolle, P.; Barrere, F.; Bruijn, J.G.M. de; Schoonman, J.; Blitterswijk, C.A. van; Groot, K. de

    2001-01-01

    A new biomimetic method for coating metal implants enables the fast formation of dense and homogeneous calcium phosphate coatings. Titanium alloy (Ti6Al4V) disks were coated with a thin, carbonated, amorphous calcium phosphate (ACP) by immersion in a saturated solution of calcium, phosphate, magnesi

  20. Scientific Opinion on the safety assessment of the active substances iron powder, activated carbon, calcined kaolin, sodium chloride, polyacrylic acid, sodium salt, crosslinked and calcium chloride, 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

    2014-05-01

    Full Text Available This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids deals with the safety assessment of the active substances iron powder, activated carbon, calcined kaolin, sodium chloride, polyacrylic acid, sodium salt, crosslinked and calcium chloride, used in mixture which is packed into labels, for absorbing oxygen from 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 supplements. Migration of substances from the labels and formation and release of volatile constituents are not expected under the intended conditions of use. The CEF Panel concluded that the use of substances iron powder, activated carbon, calcined kaolin, sodium chloride, polyacrylic acid, sodium salt, crosslinked and calcium chloride does not raise a safety concern when used in oxygen absorbers in labels, which prevent the physical release of their content into the food. When placed in the headspace of the packaging or when used in direct contact with foods, the labels should not intentionally or unintentionally come into direct contact with liquid foods or foods that have an external aqueous phase on the surface such as sliced fruits.

  1. A five way crossover human volunteer study to compare the pharmacokinetics of paracetamol following oral administration of two commercially available paracetamol tablets and three development tablets containing paracetamol in combination with sodium bicarbonate or calcium carbonate.

    Science.gov (United States)

    Grattan, T; Hickman, R; Darby-Dowman, A; Hayward, M; Boyce, M; Warrington, S

    2000-05-01

    This report concerns a single dose randomized five way crossover study to compare the pharmacokinetics of paracetamol from two commercially available paracetamol (500 mg) tablets and three different development paracetamol (500 mg) tablet formulations containing either sodium bicarbonate (400 mg), sodium bicarbonate (630 mg) or calcium carbonate (375 mg). The results demonstrated that addition of sodium bicarbonate (630 mg) to paracetamol tablets, increased the rate of absorption of paracetamol relative to conventional paracetamol tablets and soluble paracetamol tablets. Addition of sodium bicarbonate (400 mg) to paracetamol tablets increased the absorption rate of paracetamol relative to conventional paracetamol tablets, but there was no difference in the rate of absorption compared to soluble paracetamol tablets. Inclusion of calcium carbonate (375 mg) to paracetamol tablets had no effect on absorption kinetics compared to the conventional paracetamol tablet. The faster absorption observed for the sodium bicarbonate formulations may be as a result of an increase in gastric emptying rate leading to faster transport of paracetamol to the small intestine where absorption takes place.

  2. Late Quaternary paleoceanographic features as deduced from calcium carbonate and faunal changes of planktonic foraminifers in core samples from northeastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, K.K.; Jayalakshmy, K.V.; Singh, A.D.

    carbonate and planktonic foraminifers, with implications on paleoceanography of the Arabian Sea during late Quaternary. Paleoclimatic curve based on per cent variations of carbonate<