Aqueous Solutions Of Calcium Nitrate Research Articles

X-Ray Diffraction Data on the Structure of the Nearest Environment of Ions in Aqueous Solutions of Calcium Nitrate

X-Ray Diffraction Data on the Structure of the Nearest Environment of Ions in Aqueous Solutions of Calcium Nitrate

Addressing of different synthetic and shaping approaches for β-tri calcium phosphate macro-microporous scaffold fabrication

The importance of facile and reliable route for preparing pure beta-tricalcium phosphate (β-TCP) is immense for bone grafting application. In addition to compositional purity, repercussions related with control over development of porosity, i.e. shaping, are even greater. In this study, we considered two facile synthesis paths from aqueous solutions of calcium nitrate and diammonium hydrogenphosphate for preparation of β-TCP based powder; (I) controlled approach; a slow calcium deficient hydroxyapatite (CDHA) precipitation method with controlled pH, and (II) fast approach; a rapid CDHA precipitation, followed by calcination to obtain the β-TCP based form. After synthesis, we experimentally optimised the parameters for the production of ceramic templates with various morphology and microstructure through: (I) 3D printing, and (II) foam replication templating. Regarding the synthesis, X-ray diffraction (XRD) confirmed that the slow precipitation method yields pure β-TCP after calcination, while for the fast method, β-TCP in mixture with minor β-CPP (beta-calcium pyrophosphate) quantities was obtained. For both approaches, hydroxyapatite (HA) was not observed even in traces. The prepared porous ceramic bodies were broadly characterized through their total porosity (Archimedes' method), microporosity and specific surface (adsorption-desorption isotherms) and morphology by scanning electron microscopy (SEM). Characterisations give rise to a reliable synthetic route for preparing of highly porous monophasic β-TCP bodies. The course of shaping and porosity development of β-TCP bodies was meticulously considered.

Nanocomposites Based on Porous Polylactide, Obtained by Crazing Mechanism in Water–Ethanol Solutions, and Calcium Phosphates

Systematic investigations of uniaxial deformation of an amorphous isotropic polylactide film in water–ethanol solutions of different composition are carried out and optimal conditions for polymer deformation by the crazing mechanism are determined. In the whole range of the solution compositions, the polylactide deformation is accompanied by the formation of a highly dispersed fibrillar-porous structure according to the mechanism of classical crazing. When the ethanol content is ~35 wt %, the film deformability increases sharply, and it reaches 400–500% in solutions with the ethanol content of more than 45 wt %. The fine structure of the polylactide crazes during deformation in a 50% aqueous ethanol solution is studied in situ by X-ray scattering at small angles. The intensity distribution curves for polylactide samples, regardless of the degree of deformation, are characterized by the presence of an interference maximum, which indicates the regular arrangement of the individual fibrils in crazes relative to each other. The interfibrillar distance is 40 nm at the degree of deformation up to 200%. Composite materials containing nanoparticles (average crystallite size is ~30 nm) of various biologically active calcium phosphates are obtained on the basis of porous polylactide matrices (with a volumetric porosity of ~45 vol %) using the method of countercurrent diffusion between aqueous solutions of calcium nitrate and ammonium hydrogen phosphate. The filler content has reached 30 wt %. Such organomineral materials are considered promising in the field of biomedicine.

Full Color Camouflage in a Printable Photonic Blue-Colored Polymer.

A blue reflective photonic polymer coating which can be patterned in full color, from blue to red, by printing with an aqueous calcium nitrate solution has been fabricated. Color change in the cholesteric liquid-crystalline polymer network over the entire visible spectrum is obtained by the use of nonreactive mesogen. The pattern in the coating is hidden in the blue color dry state and appears upon exposure to water or by exhaling breath onto it due to different degrees of swelling of the polymer network. The degree of swelling depends on the printed amount of calcium which acts as a cross-linker. The printed full color pattern can also be hidden simply by using a circular polarizer. The responsive full color camouflage polymers are interesting for various applications ranging from responsive house and automobile decors to anticounterfeit labels and data encryption.

ВЛИЯНИЕ ТЕМПЕРАТУРЫ НА ФАЗООБРАЗОВАНИЕ В ТРОЙНОЙ СИСТЕМЕ Ca(NO3)2–H2O– n-C3H7OH

В работе представлены сведения по изучению трехкомпонентной системы нитрат кальция – пропанол-1 – вода при отрицательных температурах (-5, -10, -15, -20 °С) и нахождению ее оптимального состава с перспективой применения в качестве хладоносителя. По полученным экспериментальным данным и построенным фазовым диаграммам установлен оптимальный состав раствора, пригодный к применению в качестве хладоносителя: массовая доля пропанола –1 – 5 %, воды – 55 % и соли – 40 %.

Synthesis and characterization of Ag-containing calcium phosphates with various Ca/P ratios.

Ag-containing calcium phosphate (CaP) powders were synthesized by a precipitation method using aqueous solutions of calcium nitrate, silver nitrate, and ammonium phosphate. The powders were sintered at temperatures ranging from 1173 to 1473 K. The charged atomic ratios of (Ca+Ag)/P and Ag/(Ca+Ag) in solution were varied from 1.33 to 1.67 and from 0 to 0.30, respectively. The Ag content in the as-precipitated CaP powders increased with the charged Ag/(Ca+Ag) atomic ratio in solution and was lower than the charged Ag/(Ca+Ag) value. The as-precipitated CaP powders consisted of hydroxyapatite (HA) as the main phase. Ag nanoparticles were observed on the as-precipitated HA particles under all conditions of Ag addition. After the sintering, HA, β-TCP (tricalcium phosphate), α-TCP, and β-CPP (calcium pyrophosphate) were mainly detected as CaPs on the basis of the Ca/P atomic ratio of the as-precipitated powders. The addition of Ag stabilized the β-TCP phase, and the distribution of Ag in β-TCP was homogeneous. A metallic Ag phase coexisted with HA. The solubility of Ag in HA was estimated to be 0.0019-0.0061 (Ag/(Ca+Ag)) atomic ratio, which was lower than that in β-TCP (higher than 0.0536) and higher than that of β-CPP (below the detection limit of analyses).

Corrosion behavior of low carbon steel in technological aqueous calcium nitrate solutions

Corrosion behavior of low carbon steel in technological aqueous calcium nitrate solutions

Biodiesel production from waste cooking palm oil using calcium oxide supported on activated carbon as catalyst in a fixed bed reactor

A reactor has been developed to produce high quality fatty acid methyl esters (FAME) from waste cooking palm oil (WCO). Continuous transesterification of free fatty acids (FFA) from acidified oil with methanol was carried out using a calcium oxide supported on activated carbon (CaO/AC) as a heterogeneous solid-base catalyst. CaO/AC was prepared according to the conventional incipient-wetness impregnation of aqueous solutions of calcium nitrate (Ca(NO3)2·4H2O) precursors on an activated carbon support from palm shell in a fixed bed reactor with an external diameter of 60 mm and a height of 345 mm. Methanol/oil molar ratio, feed flow rate, catalyst bed height and reaction temperature were evaluated to obtain optimum reaction conditions. The results showed that the FFA conversion increased with increases in alcohol/oil molar ratio, catalyst bed height and temperature, whereas decreased with flow rate and initial water content in feedstock increase. The yield of FAME achieved 94% at the reaction temperature 60 °C, methanol/oil molar ratio of 25: 1 and residence time of 8 h. The physical and chemical properties of the produced methyl ester were determined and compared with the standard specifications. The characteristics of the product under the optimum condition were within the ASTM standard. High quality waste cooking palm oil methyl ester was produced by combination of heterogeneous alkali transesterification and separation processes in a fixed bed reactor. In sum, activated carbon shows potential for transesterification of FFA.

Reverse Micelle-Mediated Synthesis and Characterization of Tricalcium Phosphate Nanopowder for Bone Graft Applications

Nanocrystalline β-tricalcium phosphate (β-TCP) powder was synthesized using reverse micelle as a template system. Cyclohexane was used as the oil phase, aqueous solutions of calcium nitrate and phosphoric acid as the aqueous phase, and poly(oxyethylene)5 nonylphenol ether (NP-5) and/or poly(oxyethylene)12 nonylphenol ether (NP-12) as the surfactants. The powder were synthesized at a fixed Ca/P molar ratio of 1.5 at a pH of 10. The synthesized powder were calcined at 800°C to obtain monophasic β-TCP. Particle size, morphology, and surface area of the synthesized powder were dependent on the chemistry of the surfactant and composition of the microemulsion. The powder were characterized using a BET surface area analyzer, powder X-ray diffraction, dynamic light scattering technique, and transmission electron microscopy. TCP nanoparticles had a particle size between 32 and 135 nm, and a BET-specific average surface area between 57 and 103 m2/g with controlled morphology. The powder were consolidated and sintered at 1250°C in a 3 kW microwave furnace in the form of a compact disk. Human osteoprecursor cells (osteoblastic precursor cell line 1 [OPC1]) were used to assess the biocompatibility of TCP disks after 1, 5, and 11 days in culture using scanning electron microscopy, MTT assay, and alkaline phosphatase expressions. Disk samples were biocompatible and showed excellent OPC1 cell adhesion, growth, and proliferation. Biocompatible β-TCP nanopowder were synthesized with controlled particle size, morphology, and surface area using a reverse micelle-mediated template system.

Nanocomposites of bacterial cellulose/hydroxyapatite for biomedical applications

In the present work, a nanocomposite material formed by bacterial cellulose (BC) networks and calcium-deficient hydroxyapatite (HAp) powders was synthesized and characterized. The HAp nanoparticles were previously prepared by a wet chemical precipitation method, starting from aqueous solutions of calcium nitrate and di-ammonium phosphate salts. Energy-dispersive spectroscopy reveals that the prepared HAp corresponds to calcium-deficient hydroxyapatite. BC-HAp nanocomposites were prepared by introducing carboxymethylcellulose (CMC) into the bacteria culture media. HAp nanoparticles were then introduced and remained suspended in the culture medium during the formation of cellulose nanofibrils. The maximum gel thickness was obtained after 21 days of bacteria cultivation. X-ray diffractograms showed the difference of crystallinity among the materials involved in the formation of nanocomposites. The inorganic and organic bonds that corresponded to hydroxyapatite and bacterial cellulose respectively, were depicted by attenuated total reflectance Fourier transform infrared spectra. Scanning electron microscopy and atomic force microscopy measurements confirmed the formation of networks and fibres with smaller diameter corresponding to BC synthesized in the presence of CMC. Image analysis was also used to assess the orientation distributions and Feret diameters for networks of BC and BC-CMC. Thermogravimetric analysis showed that the amount of the mineral phase is 23.7% of the total weight of the nanocomposite. Moreover, HEK cells were cultivated and the biocompatibility of the materials and the cell viability was demonstrated.

Calcium phosphate nanoparticles for the transfection of cells

Transfection is a widely used method in molecular biology for the introduction of foreign nucleic acids (DNA or RNA) into eukaryotic cells that permits to control intracellular processes, i.e. the induction or inhibition of protein expression. Nucleic acids alone cannot penetrate the cell membrane, therefore special carriers like cationic polymers or inorganic nanoparticles are required. Single-shell and multi-shell calcium phosphate nanoparticles were prepared and functionalized with DNA and siRNA. Thereby, the expression of enhanced green fluorescing protein (EGFP) can be induced (by using pcDNA3-EGFP) or silenced (by using siRNA). The single-shell nanoparticles were prepared by rapid mixing of aqueous solutions of calcium nitrate and diammonium hydrogen phosphate. The multi-shell nanoparticles were produced by adding further layers of calcium phosphate and DNA to protect DNA from the intracellular degradation by endonucleases. The size of the nanoparticles according to dynamic light scattering and electron microscopy was up to 100 nm with a zeta potential around -30 mV. The transfection efficiency of the nanoparticles was tested in vitro in cell culture.

Hydroxyapatite of platelet morphology synthesized by ultrasonic precipitation from solution

Hydroxyapatite (HA) synthesis by precipitation with urea from aqueous solutions of calcium nitrate and ammonium hydrogenphosphate is studied. Ultrasonication during the synthesis decreases the size of platelet HA crystals from several micrometers to 200–300 nm. At low calcium concentrations in solution, the crystallizing phase is carbonate-hydroxyapatite, whereas at high calcium concentrations, octacalcium phosphate (OCP) precedes hydroxyapatite crystallization.

Silicon-containing hydroxylapatite nanopowders

Silicon-substituted hydroxylapatite nanopowders containing 0.14–1.4 wt % Si have been synthesized by the heterophase reaction between calcium hydroxide, diammonium hydrogen phosphate, tetraethoxysilane, and water and by precipitation from aqueous solutions of calcium nitrate, diammonium hydrogen phosphate, and tetraethoxysilane. The products have been characterized by specific surface area (S BET) measurements, X-ray powder diffraction, chemical analysis, and IR spectroscopy. The phase composition of the products depends on the synthesis method. The heterophase reaction yields nanopowders with S BET = 20–24 m2/g in which the main crystalline phase is silicon-substituted hydroxylapatite. The product synthesized by precipitation from solution has an S BET of up to 73 m2/g and an increased tricalcium phosphate content, which crystallizes from the amorphous phase during heat treatment.

Ruthenium-containing small-pore zeolites for shape-selective catalysis

Ruthenium-containing small-pore zeolites with the framework types LTA, KFI, MER and RHO were prepared by addition of ruthenium(III) chloride to the gel of the hydrothermal zeolite synthesis in the absence of organic templates. This synthesis strategy was described earlier for the large- and medium-pore zeolites Ru/Na-X (FAU) and Ru/Na-ZSM-5 (MFI), respectively. The majority of the ruthenium species in the modified small-pore zeolites has a diameter in the order of 1 nm or less and is located inside the pores of the frameworks. These species are available for shape-selective catalytic conversions as demonstrated by the competitive hydrogenation of 1-hexene and 2,4,4-trimethyl-1-pentene. This test reaction allows to differentiate between ruthenium particles within the zeolite pores and those on the external crystal surface. Consequently, LTA-type zeolites with intrazeolitic ruthenium species could be synthesized with ruthenium loadings of up to 4.0 wt.%. A further increase of the ruthenium content to 8.0 wt.% resulted in a significant fraction of the ruthenium (oxide) clusters on the external crystal surface. Ruthenium species on the outer crystal surface also exist after the hydrothermal zeolite synthesis. These can, however, be removed by ion exchange with an aqueous calcium nitrate solution.

Sorption, desorption and extraction of cadmium from some arable and forest soils

The behavior of cadmium labeled with 109Cd in different depth horizons of arable and forest soils were studied under static (batch) conditions in three interconnected processes, which consist of sorption, desorption and extraction. In the sorption, Cd2+ was applied in the aqueous calcium nitrate solution. Both untreated soils and peroxide treated soils were used in order to remove organic matter from some of the soil samples used in parallel. The influence of the V/m ratio on the sorption coefficients was investigated in preliminary experiments with untreated soils. Contrary to the usually short-term sorption, a long-term sorption of cadmium was investigated in untreated and treated soil horizons, which lasted more than fortnight. Kinetic studies of sorption were carried out and cadmium concentration dependence in aqueous phase of the second order kinetic constants was observed. For evaluation of sorption and desorption processes Freundlich isotherms were used. It was found that the Freundlich adsorption intensity coefficient is more time dependent than the absorption capacity coefficient, and the sorption itself consists of rapid and slow processes according to the soil constituents. Desorption and extraction processes revealed the possibility of cadmium recovery from various soil horizons. Based on the obtained results two- or three-stage theory of cadmium retention in soils was proposed. Some new insight into the role of organic matter in the sorption/desorption process of cadmium is also presented.

Effect of Some Physical-Chemical Variables in the Synthesis of Hydroxyapatite by the Precipitation Route

The synthetic hydroxyapatite is a very useful material for numerous applications in medicine as a biomaterial. One of the most economic manufacturing process is the precipitation route. In the present work, synthetic hydroxyapatite was prepared using the precipitation route, starting with aqueous solutions of calcium nitrate (Ca(NO3).4H2O ) and ammonium phosphate (H2(PO4)NH4). The effects of physical-chemical variables such as pH, temperature, time of agitation, ageing time and heat treatment of the mixture were evaluated. The characterization of the samples obtained in different conditions made possible to conclude about the optimal values of the studied variables for the synthesis of this material in laboratory conditions.

Formation of apatitic calcium phosphates in a Na-K-phosphate solution of pH 7.4

Poorly crystalline, apatitic calcium phosphate powders have been synthesized by slowly adding a Na- and K-containing reference phosphate solution with a pH value of 7.4 to an aqueous calcium nitrate solution at 37 degrees C. Nano-particulated apatitic powders obtained were shown to contain small amounts of Na and K, which render them more similar in chemical composition to that of the bone mineral. Precipitated and dried powders were found to exhibit self-hardening cement properties when kneaded in a mortar with a sodium citrate- and sodium phosphate-containing starter solution. The same phosphate solution used in powder synthesis was found to be able to partially convert natural, white and translucent marble pieces of calcite (CaCO3) into calcium-deficient hydroxyapatite upon aging the samples in that solution for 3 days at 60 degrees C. Sample characterization was performed by using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, inductively-coupled plasma atomic emission spectroscopy, and simultaneous thermogravimetry and differential thermal analysis.

Process Intensification: Precipitation of Calcium Carbonate Using Narrow Channel Reactors

Precipitation processes are widely used in industry for the production of particulate solids. Efficient mixing of the reagents influences the development of supersaturation in the reaction environment and therefore the particle characteristics. Intensified modules can provide a new route for obtaining improved mixing and this paper illustrates an experimental investigation using narrow channel reactors for the precipitation of calcium carbonate by reacting aqueous solutions of calcium nitrate and sodium carbonate. Two channels of square cross sectional area, having a diagonal line of 1 x 10–3 and 2 x 10–3m, respectively, were used and experiments were carried out by varying flow rates and reagent concentration. A flow visualization technique has been used to understand the flow behaviour in the reactor channels, which were also characterized by calculating the specific power input transmitted to the reagents. The calcium carbonate slurry was analysed for particle size and dispersity with a Malvern Mastersizer 2000. Images of the particles were obtained by using an optical microscope connected to a digital camera and a scanning electron microscope (SEM). Selected samples were also analysed by X-ray diffraction. Limited batch experiments were conducted for benchmarking the performance of the narrow channel reactors.

Ion-Complex Formation in Aqueous Solutions of Calcium Nitrate. Acoustical Absorption Spectrometry Study

Ultrasonic absorption spectra between 800 kHz and 2 GHz and sound velocities of aqueous solutions of calcium nitrate have been measured at different salt concentrations and temperatures, as well as...

Radiation-Initiated Dehalogenation of Trichloroacetic Acid in Aqueous Solutions

Organochlorine compounds are widespread anthropogenic water pollutants. These compounds are toxic and carcinogenic. They are released into natural water from industrial emissions and as a consequence of agricultural use of pesticides or are formed upon the chlorination of drinking water because of the presence of various organic compounds. According to data [1], more than 150 chlorine-containing organic compounds are formed in the chlorination of water. Chlorinated organic compounds in water can be destroyed with the use of ionizing radiation [2, 3]. The knowledge of the mechanisms of radiolysis of chlorinated organic compounds from various classes is necessary for the development and application of radiation technologies to the removal of organochlorine compounds from natural water. Moreover, chlorinated organic compounds are convenient test materials for studying nucleophilic substitution reactions in radicals [4, 5]. Previously [4‐6], the reactions of chlorinated organic compounds ( CH 2 Cl 2 , ClCH 2 CH 2 Cl, CHCl 3 , CH 3 CHClCH 3 , C 6 H 5 Cl, ClC 6 H 5 CH 3 , and C 6 H 6 Cl 6 ) in aqueous alkaline solutions under exposure to ionizing radiation were examined. In this work, deaerated aqueous 0.1 M trichloroacetic acid solutions with different concentrations of an alkali were irradiated. The solutions were prepared with the use of twice-distilled water. Freshly prepared solutions were irradiated in sealed ampules. The γ -radiation dose rate was 0.34 Gy/s as measured with a ferrous sulfate dosimeter. The concentrations of chloride and oxalate ions in the samples were determined as functions of radiation dose. The radiation-chemical yields of chloride ions and oxalic acid were calculated from the dose curves. Chloride ions were determined by potentiometric titration with silver nitrate [6]. The determination error in the radiation-chemical yields of chloride ions was no higher than 15%. Oxalate ions were identified by the formation of a precipitate on the addition of an aqueous calcium nitrate solution to irradiated and acidified samples. Quantitative analysis for ions was performed by back titration with potassium permanganate [7] at room temperature. The analytical procedure was developed with standard C 2 O 4 2 ‐ oxalic acid solutions containing trichloroacetic acid (0.1 mol/l) and chloride ions in concentrations that were expected to form by irradiation. Trichloroacetic acid and chloride ions did not interfere with the determination of oxalate ions. The maximum determination error for oxalate ions was 19%. The figure illustrates the experimental results. The intensity of dehalogenation of trichloroacetic acid increased with alkali concentration in solution. The radiation-chemical yields of chloride and oxalate ions were as high as 14.4 ∠ 0.8 and 4.8 ∠ 0.9 molecule/100 eV, respectively, at [NaOH] = 0.8 mol/l. The formation of Cl — and ions on irradiation of alkaline solutions can be represented by the following reaction scheme: