Concentrations Of CaCO3 Research Articles

Optimization of mechanical properties of PP/Nanoclay/CaCO3 ternary nanocomposite using response surface methodology

AbstractResponse surface method of experimental design was applied to optimize the mechanical properties of polypropylene (PP)/nanoclay/CaCO3 hybrid ternary nanocomposite using three different levels of melt flow index (MFI) of PP, nanoclay, and CaCO3 contents. The samples were prepared by melt mixing in a lab scale corotating twin screw extruder. The main effect of each parameter on the tensile modulus, tensile strength, and impact strength was extensively discussed. The structure of obtained nanocomposite was studied using X‐ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques. Tensile modulus and impact resistance of prepared ternary nanocomposite were correlated to considered parameters using a second‐order polynomial model. Also, the optimum values of studied variables were determined using contour plots. The obtained results show that increasing the nanoclay and CaCO3 contents improve the tensile modulus up to 45%, whereas the optimum value of impact strength, about 54%, is achieved at low concentrations of nanoclay (2 wt %) and CaCO3 (8 wt %). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Formulation Evaluation and Optimization of Stomach Specific In situ Gel of Ranitidine Hydrochloride

The objectives of this research work were preparation, optimization and evaluation of in situ gelling system of Ranitidine. HCl based on sodium alginate that retains in the stomach by adherence to gastric wall providing an increased gastric residence time resulting in prolonged drug delivery in gastrointestinal tract. Sodium alginate was used as a polymer and CaCO3 as a cross-linking agent. The in situ formulation exhibited the expectations, viscosity, drug content and sustained drug release. This study reports that oral administration of aqueous solutions containing sodium alginate results in formation of in situ gel and such formulations are homogenous liquids when administered orally and become gel at the contact site. The results of a 32 full factorial design revealed that the concentrations of sodium alginate and CaCO3 significantly affected the dependent variables of viscosity, Q50 and Q80. These in situ gels are, thus, suitable for oral sustained release of Ranitidine HCL.

Benthic foraminifer communities of the Persian Gulf

Eighteen types of benthic foraminifer communities inhabiting depths of 0–200 m are described for the Persian Gulf including the analysis of 269 sampling sites. The species area is mostly localized by the geographical position and bathymetrical features, including the water masses advection, the upwelling, the river discharge, and the concentrations of CaCo3 and Corg in the bottom sediments.

Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

Geochemical and rock-magnetic investigations were carried out on a sediment core collected from the SE Arabian Sea at 1420 m depth in oxygenated waters below the present-day oxygen minimum zone. The top 250 cm of the core sediments represent the last 35 kaBP. The · 18O values of Globigerinoides ruber are heaviest during the Last Glacial Maximum (LGM) and appear unaffected by low-saline waters transported from the Bay of Bengal by the strong northeast monsoon and West Indian coastal current. The signatures of Bølling-Allerød and Younger Dryas events are distinct in the records of magnetic susceptibility, organic carbon (OC) and · 18O. Glacial sediments show higher OC, CaCO3, Ba, Mo, U and Cd, while the early-to-late Holocene sediments show increasing concentrations of OC, CaCO3, Ba, Cu, Ni and Zn and decreasing concentrations of Mo, U and Cd. Productivity induced low-oxygenated bottom waters and reducing sedimentary conditions during glaciation, and productivity and oxygenated bottom waters in the Holocene are responsible for their variation. The core exhibits different stages of diagenesis at different sediment intervals. The occurrence of fine-grained, low-coercivity, ferrimagnetic mineral during glacial periods is indicative of its formation in organic-rich, anoxic sediments, which may be analogous to the diagenetic magnetic enhancement known in sapropels of the Mediterranean Sea and Japan Sea. The glacial sediments exhibiting reductive diagenesis with anoxic sedimentary environment in this core correspond to reductive diagenesis and intermittent bioturbation (oxygenation) reported in another core in the vicinity. This suggests that the poorly oxygenated bottom water conditions during glacial times should not be generalized, but are influenced locally by productivity, sedimentation rates and sediment reworking.

Development of a Novel Floating In-situ Gelling System for Stomach Specific Drug Delivery of the Narrow Absorption Window Drug Baclofen.

The present study deals with development of a floating in-situ gel of the narrow absorption window drug baclofen. Sodium alginate-based in-situ gelling systems were prepared by dissolving various concentrations of sodium alginate in deionized water, to which varying concentrations of drug and calcium bicarbonate were added. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to check the presence of any interaction between the drug and the excipients. A 3(2) full factorial design was used for optimization. The concentrations of sodium alginate (X1) and calcium bicarbonate (X2) were selected as the independent variables. The amount of the drug released after 1 h (Q1) and 10 h (Q10) and the viscosity of the solution were selected as the dependent variables. The gels were studied for their viscosity, in-vitro buoyancy and drug release. Contour plots were drawn for each dependent variable and check-point batches were prepared in order to get desirable release profiles. The drug release profiles were fitted into different kinetic models. The floating lag time and floating time found to be 2 min and 12 h respectively. A decreasing trend in drug release was observed with increasing concentrations of CaCO3. The computed values of Q1 and Q10 for the check-point batch were 25% and 86% respectively, compared to the experimental values of 27.1% and 88.34%. The similarity factor (f 2) for the check-point batch being 80.25 showed that the two dissolution profiles were similar. The drug release from the in-situ gel follows the Higuchi model, which indicates a diffusion-controlled release. A stomach specific in-situ gel of baclofen could be prepared using floating mechanism to increase the residence time of the drug in stomach and thereby increase the absorption.

Morphological and thermal analyses of flexible polyurethane foams containing commercial calcium carbonate

One filler often utilized in flexible polyurethane foams is calcium carbonate (CaCO3) because it is non-abrasiveness, non-toxicity and facilitated pigmentation. However, it is observed that the excess of commercial CaCO3 utilized in industry possibly causing permanent deformations and damaging the quality of the final product. The effect of different concentrations of commercial CaCO3, in flexible foams, was studied. Different concentrations of CaCO3 were used for the synthesis of flexible polyurethane foams, which were submitted to morphological and thermal analyses to verify the alterations provoked by the progressive introduction of this filler.

Effects of Coupling Agents on the Tensile Properties of Calcium Carbonate Filled LDPE Compatibilized with Maleic Anhydride-g-LDPE (Part I)

In this study many composites based on low density polyethylene (LDPE) with calcium carbonate (CaCO3) and maleic anhydride-grafted polyethylene (MAH-g-LDPE) as a compatibilizer have been investigated in order to study their behavior and the reinforcing mechanisms involved. Different types of chemical modifications of the filler surface were carried out in an attempt to enhance the interactions with the polymeric matrix by using silane and zirconate coupling agents. The compatibilizer was created using a single screw extruder by impregnating LDPE granulates with a solution obtained by dissolving in acetone the dicumyl peroxide used as the initiator for the grafting reaction, maleic anhydride as the grafting monomer, and triphenyl phosphine (TPP) as the stabilizer. Titration measurements indicated that the extent of grafting achieved was 0.21% by weight. The composites containing different concentrations of untreated CaCO3 and those treated with 2% of the compatibilizer were prepared by melt mixing using a two roll mill. It was found that the mechanical properties, which depended greatly on the state of the dispersion of the filler as well as the nature of the interface, were relatively better than the composites prepared by the humid method. Higher reinforcement was obtained with the composites treated with the zirconate coupling agent than those modified with the silane coupling agent.

Morphological and thermal analyses of flexible polyurethane foams containing commercial calcium carbonate

One filler often utilized in flexible polyurethane foams is calcium carbonate (CaCO3) because it is non-abrasiveness, non-toxicity and facilitated pigmentation. However, it is observed that the excess of commercial CaCO3 utilized in industry possibly causing permanent deformations and damaging the quality of the final product. The effect of different concentrations of commercial CaCO3, in flexible foams, was studied. Different concentrations of CaCO3 were used for the synthesis of flexible polyurethane foams, which were submitted to morphological and thermal analyses to verify the alterations provoked by the progressive introduction of this filler.

Changes in germination and glyoxylate and respiratory enzymes of Pinus pinea seeds under various abiotic stresses

This study examined Pinus pinea seeds for their tolerance to osmotic potentials of −0.30MPa (10% polyethylene glycol [PEG]), −0.58MPa (18% PEG), −0.80MPa (21% PEG), −1.05MPa (24% PEG), pH values of 4, 5, 6, 7, 8, 9, 10, and different calcareous solutions (5, 10, 20 and 40% CaCO3). The main enzymes of glyoxylate cycle and respiratory pathway were tested. Pinus pinea seeds under no stressful condition (Control) and 5% CaCO3 reached 100% of germination. Higher concentrations of CaCO3 (20, 40%) and lower pH (4–5) adversely affected seed germination percentage, glyoxylic and respiratory enzyme activities. PEG caused the most detrimental effects on Pinus seeds; increasing the osmotic potential the germination was completely inhibited. These results suggest that Pinus pinea is able to germinate in calcareous and alkaline soils rather than in soils with lower water availability and acidic conditions.

Influence of PSSS on the morphology and polymorph of calcium carbonate in the ethanol–water mixed system

The morphogenesis and phase changes of calcium carbonate in an ethanol/water mixed solvent in the presence of polyelectrolyte poly-(sodium 4-styrene-sulfate) (PSSS) were carefully investigated. The results showed that the ethanol volume content in the mixed solvent, temperature, the molar ratio of [CO32−]/[Ca2+] (R), and the concentrations of PSSS and CaCO3 turned out to be important parameters for the control of morphologies and polymorphs of CaCO3. Various morphologies of CaCO3 particles, such as rhombohedras, cubes, flowers, spheres, pancakes, etc. could be obtained dependent on the experimental conditions. Especially, monodispersed spheroid vaterite particles were obtained at the concentration of CaCO3 of 4 mM. In addition, pancake-like vaterite particles were synthesized at 100 °C. This research may provide a promising route for the selective synthesis of other inorganic materials with different morphologies and polymorphs.

Selective and in-situ determination of carbonate and oxide particles in aqueous solution using laser-induced breakdown spectroscopy (LIBS) for wearable information equipment

Laser-induced breakdown spectroscopy (LIBS) has been applied for quantitative analysis of Al2O3, CaCO3 and MgO particles suspended in water. In the single elemental system, the plasma emission intensities of Al, Ca and Mg were linearly increased with concentration of elements in the range of 1.0×10−5–1.0×10−3 M, 1.0×10−4–2.0×10−3 M and 8.0×10−5 –4.0×10−3 M, respectively. We also investigated the concentration dependence of breakdown spectra for suspended mixtures of Al2O3, CaCO3 and MgO particles. The emission lines, such as Al I, Ca I, Ca II and Mg I, were appeared in the LIBS spectrum simultaneously, and each emission peak could be deconvoluted. The plasma emission intensities of Al, Ca and Mg in the multielemental system were also linearly increased with their concentrations in the range of 1.0×10−5–1.0×10−3 M, 1.0×10−4–2.0×10−3 M and 4.0×10−4–2.0×10−3 M, respectively. LIBS was found to be available for quantitative and qualitative measurement of the concentrations of Al2O3, CaCO3 and MgO particles suspended in water. The present results suggest that LIBS is a potentially useful tool for in-situ analysis on particles composition and concentrations for environmental monitoring by the wearable information equipments.

English

Amplification of gene expression of the most productive colony type of Amycolatopsis mediterranei strain N1 under stress of chloramphenicol, resulted in isolation of a variant NCH with productivity of 2.56 g/l compared to 1.15 g/l by the parent strain N1 (2.2 fold increase) . This amplified variant has a further advantage of reduced variation in colony morphology with predominance of the most productive colony type. Using variant NCH, modification of the fermentation medium F1 by the addition of 0.1%  yeast extract or the use of 1.8% KNO3  resulted in 3.8 and 5.8-fold increase in productivity, respectively, compared to  strain N1. When the F1 medium was replaced by a new medium F2 containing soytone, instead of the particulate constituents (peanut meal and soybean meal) the yield by variant NCH reached 7.85 g/l (6.8-fold increase). Modification of the F2 medium by addition of glycerol or the replacement of glucose by glucose syrup decreased rifamycin B production. Changing the concentration of soytone increased the yield only slightly while replacing it with peptone or tryptone or the addition of 1 % corn steep liquor failed to increase the yield. On the other hand, the addition of 0.1 % yeast extract, or the replacement of 0.6% (NH4)2SO4 by 1.2% KNO3 or 0.4% NH4NO3,  to F2 medium led to 8.2, 10.2 and 10.4-fold increase in productivity, respectively, compared to productivity of strain N1 in F1 medium. The change in the concentrations of either MgSO4 or CaCO3, the use of different types of antifoams and the use of higher concentrations  of sodium diethyl barbiturate did not significantly influence the yield. These collective optimization attempts thus resulted in a 10.4-fold increase in productivity, from 1.15 to 11.99 g/l.   Key words: Rifamycin B, fermentation, biotechnology, Amycolatopsis mediterranei,optimization, gene amplification, physiological factors.

Melt strength of calcium carbonate filled polypropylene melts

AbstractThis paper investigates the extensional rheology (through melt strength measurement) of calcium carbonate (CaCO3) filled polypropylene (PP) melts. Different concentrations of CaCO3 filled PP were produced by mixing two master batches of pure PP and 70 wt% CaCO3 filled PP in required proportions in a counter‐rotating twin‐screw extruder. It was found that the melt strength of the CaCO3–PP melts was independent of CaCO3 concentrations up to 25 vol%. Further increase in CaCO3 concentration led to a severe reduction of melt strength.© 2002 Society of Chemical Industry

Densification and thermal conductivity of low-sintering-temperature AlN materials

The aim of the study was the sintering of aluminium nitride at rather low temperatures (≤1650°C). Various sintering aids were studied, in particular AlSi- and Ca-based oxides. CaCO 3 and 3CaO-3SiO 2 -Al 2 O 3 are the most efficient additives, because quantities as low as 0·5 wt% are enough to yield sintered AlN substrates with no open porosity. TEM observations showed that low concentrations of CaCO 3 or CaSiO 3 lead to location of the secondary phases at the triple points, whereas high concentrations lead to wetting of the grains. Thermal diffusivity of sintered materials was determined by a laser flash method. The highest conductivity (70 W m −1 K −1 ) is obtained with CaCO 3 additions. These additions promote liquid formation, which cleans the surface of the AlN grains from oxygen and thereby prevents oxygen from entering the AlN lattice. The CaAl 2 O 4 compound exhibits a lower thermal conductivity than the CaAl 4 O 7 and Ca 3 Al 10 O 18 compounds. The Ca 2 SiAl 2 O 7 compound and the 27R AlN polytype have a strong negative influence on the thermal conductivity of sintered materials. Das Ziel dieser Untersuchung war, Aluminiumnitrid bei relativ niedrigen Temperaturen (≤1650°C) zu sintern. Es wurden verschiedene Sinterhilfsmittel untersucht, speziell Al-, Si- und Ca-haltige Oxide. CaCO 3 und 3CaO-3SiO 2 -Al 2 O 3 sind die effektivsten Additive, weil auch niedrige Gehalte von 0·5 Masse-% ausreichen, um AlN-Substrate mit geschlossener Porosität herzustellen. TEM-Untersuchungen zeigen, daß niedrige CaCO 3 - oder CaSiO 3 -Konzentrationen zu einer zweiten Phase an den Trippelpunkten führen, wogegen hohe Konzentrationen die Körner benetzen. Die Temperaturleitfähigkeit der gesinterten Proben wurde mit der Laser flash Methode bestimmt. Die höchste Leitfähigkeit (70 W m −1 K −1 ) wird mit dem CaCO 3 -Additiv erreicht. Dieses Additiv fördert die Flüssigphasenbildung, die die Oberflächen der AlN-Körner von Sauerstoff reinigt und daher die Diffusion von Sauerstoff in das AlN-Gitter verhindert. Die CaAl 2 O 4 -Verbindung führt zu einer niedrigeren thermischen Wärmeleitfähigkeit als CaAl 4 O 7 und Ca 3 Al 10 O 18 -Verbindungen. Ca 2 SiAl 2 O 7 und die 27R AlN-Polytypen haben einen starken negativen Einfluß auf die Wärmeleitfähigkeit der gesinterten Werkstoffe. Le but de cette étude est le frittage du nitrure d'aluminium à basses températures (≤1650°C). Différents additifs de frittage ont été étudiés, en particulier des oxyges à base d'Al, de Si et de Ca. Le CaCO 3 et le 3CaO-3SiO 2 -Al 2 O 3 sont les plus efficaces car des quantités de 0·5% massique sont suffisantes pour donner des substrats frittés ne présentant plus de porosité ouverte. Des observations par TEM montrent que de faibles concentrations de CaCO 3 ou de CaSiO 3 entraînent une localisation des phases secondaires aux points triples, alors que des concentrations élevées conduisent au mouillage des grains. La diffusivité thermique des matériaux frittés a été déterminée par la méthode de flash laser. La conductivité la plus élevée (70 W m −1 K −1 ) a été obtenue avec des ajouts de CaCO 3 . Ces additions provoquent la formation d'un liquide qui extrait l'oxygène de la surface des grains, l'empêchant ainsi de pénétrer dans la maille cristalline de l'AlN. Le composé fritté à l'aide de CaAl 2 O 4 présente une conductivité thermique plus faible que ceux contenant CaAl 4 O 7 ou Ca 3 Al 10 O 18 . Le Ca 2 SiAl 2 O 7 et le polytype 27R de l'AlN ont une influence néfaste sur la conductivité thermique des matériaux.

The calcium- and iron bound phosphate phase diagram

A phase diagram for Ca- and Fe-bound phosphate has been calculated based on two criteria: The phase diagram explains why ortho-phosphate (o-PO4) in sediments, containing high concentrations of CaCO3 (about 10–30%), is bound onto the iron hydroxide rather than onto the CaCO3. The concentration of the iron hydroxide has an effect on the equilibrium between the two phosphates, whilst the concentration of CaCO3 has no effect whatsoever.

Dolomite decomposition in a high temperature fluidised bed reactor

AbstractThe decomposition of dolomite was investigated in a bench‐scale fluidised bed reactor (30 cm diameter) at temperatures between 600°C and 1000°C in batch and continuous operations. The composition of the solids was determined by X‐ray analysis, the gas composition by infrared (i.r.) spectroscopic analysis. The reaction kinetics were investigated in a small fluidised bed (2.6 cm diameter) as well as in the bench‐scale equipment and compared with kinetic data evaluated from differential thermal gravimetric (DTG) curves. The measurements were carried out by adding small amounts of dolomite into the isothermal fluidised bed. The resulting CO2 concentration within the gas could then be very low, thus MgCO3 and CaCO3 decompose as parallel reactions (singlestage reaction). At somewhat higher CO2 gas concentrations prevailing in technical operational conditions the decomposition mechanism changes into a two‐stage reaction where MgCO3 decomposes first. The bed temperature, pressure drop, superficial gas velocity, solid conversion, and specific interfacial area of solids were determined as functions of time and/or reactor wall temperature with a constant temperature increase rate for batch runs. The distributions of the residence time of solids indicate that in the continuously operated fluidised bed well‐mixed conditions prevail. The concentrations of dolomite, CaCO3, MgO, CaO, and solid conversion as well as the specific surface area of particles were determined as functions of the mean residence time in the continuous reactor. By means of the CO2 concentration in the gas phase and the mean residence time the conversions of the consecutive reactions can be controlled.

The Role of the Western Harvester Ant (Pogonomyrmex occidentalis) in Soil Formation

AbstractThe effects of harvester ants (Pogonomyrmex occidentalis) on the physical and chemical properties of soils were determined for 20 ant mounds in the semiarid subalpine region of south‐central Colorado. Comparisons of soil materials in mounds of active colonies with surrounding unaffected soils showed significant differences in particlesize distribution and concentrations of CaCO3, exchangeable K, Na, Mg, and total N. The activity of ants in the study area appears to affect less ground surface area than in more humid regions (1 to 10% of respective land areas by regional comparison). The ants also tend to rearrange particles preferentially in the sand fraction instead of in the finer fractions as recorded for more humid regions. However, their role in nutrient enrichment of mound soils is similar to that of different ant species in other regions. The soil alterations induced by P. occidentialis are favorable for plant growth, and the ant mounds may aid revegetation in disturbed areas.

Differential Response of Blueberry (Vaccinium) Progenies to pH and Subsequent Use of Iron1

Abstract Iron chlorosis often develops in blueberries (Vaccinium) grown on soils with a pH above 5.2. Seedlings of 4 blueberry intra- and interspecific progenies, involving V. ashei, V. corymbosum, and V. darrowii, were tested for Fe-efficiency (use of Fe) by growing them in nutrient solutions containing different concentrations of CaCO3 to vary the pH. Plants received Fe during the first 4 harvests (up to 75 days) but received no Fe during the subsequent 2 harvests. The Fe supply for plant growth in the last 2 harvests was limited to that available in the roots. T-65 × US 67 blueberry plants [a 3-species hybrid of V. ashei × (V.darrowii × V. corymbosum)] lowered the pH of the nutrient solution by releasing H+ from their roots which freed Fe from root accumulations and made it available for plant use. ‘Climax’ × T-151 (V. ashei × V. ashei) progeny did not do this. Seedlings of V. corymbosum and those from a cross of V. corymbosum with V. darrowii were intermediate in their response.

Differential Use of Fe3+ and Fe2+ by Oats

AbstractPlants have specific Fe requirements, dependent on their ability to make Fe available in a useful form. They are classed Fe‐efficient if they respond to Fe‐deficiency stress by inducing biochemical reactions that make Fe available in a useful form, and Fe‐inefficient if they do not. This study was conducted to characterize the use of Fe by Fe‐inefficient oats (Avena byzantina K. Koch) ‘TAM 0‐312,’ and Fe‐efficient oats ‘Coker 227.’ These cultivars were grown in nutrient solutions where they were subjected to different degrees of Fe stress induced by variable concentrations of either phosphate, CaCO3, or Fe. The oat plants were grown in an environmentally‐controlled chamber with 16 hours of light at approximately 320 µEm‐3 sec‐1 and 8 hours of darkness at a temperature of 24 ± 2 C. Coker 227 was more Fe‐efficient than TAM 0‐312 regardless of how Fe stress was induced and usually contained less Ca than TAM 0‐312. TAM 0.312 required 1.2 mg Fe/liter in the nutrient solution before it was green, whereas Coker 227 required only 0.6 mg Fe/liter. Susceptibility to Fe chlorosis in these cultivars was caused by the inherent nature of the plant to use either Fe8+ or F2+ and by the greater use of Ca by TAM 0‐312 than by Coker 227. The plant plays a key role in maintaining a proper nutrient elememt balance and the availability of a nutrient element for plant use.

Forest soils of Greece: Physical, chemical and biological properties

Physical, chemical and biological properties of Greek forest soils are reported and their use for forestry is discussed on the basis of the following underlying strata: (i) hard limestone, (ii) metamorphic rocks, (iii) Tertiary deposits, (iv) flysch, and (v) ultrabasic igneous rocks.Soils derived from hard limestone are clay to clay loam in texture, acid, neutral or alkaline in chemical reaction, adequately supplied with Ca, Mg and K of high biological activity. Soils from metamorphic rocks are considered as two separate sub-types, those derived from mica schists and those from gneisses. Soils from mica schists are silt loam to loamy in texture, acid to very acid in chemical reaction, poor in Ca, Mg and K, especially the mineral horizons of high elevation soils, and of very low biological activity possibly due to toxic concentrations of Al3+ and Mn. Soils from gneiss are loamy sand to sandy in texture,(their major distinction from the soils of the previous sub-type), acid in chemical reaction, moderately to poorly supplied with Ca, Mg and K and of very low biological activity.Soils derived from Tertiary deposits are also examined as two sub-types, those from materials rich in CaCO3 (marls) and those from siliceous materials. Soils in the first sub-type are clay to clay loam in texture and alkaline in chemical reaction with excess bases, especially Ca, and high concentrations of free CaCO3. Soils from siliceous materials are clay loam to loamy in texture, acid in chemical reaction and moderately to poorly supplied with Ca, Mg and K. Soils from flysch are clay loam to loamy in texture, acid in chemical reaction, sufficiently supplied with Ca, Mg and K and of moderate biological activity.Finally, soils derived from ultrabasic igneous rocks are clay loam to clay in texture, acid in chemical reaction, moderately to sufficiently supplied with Ca, Mg and K, and of restricted biological activity. They have high concentrations of Mg and Mn and low concentrations of Ca, K, N and P.