Aqueous Solutions Of Orthophosphoric Acid Research Articles

Influence of an addition amount of a new type of alumina on the properties of ramming mullite-corundum mixes and samples from them

Effect investigation of an addition amount of spherical alumina on the properties of ramming mullite-corundum mixes of the MMK-90 (on a binder of an aqueous solution of orthophosphoric acid) and MMKPBF (with a MgO addition on a borophosphate binder) brands, as well as samples from them, have been carried out.
 As a result of the carried out studies, it was found that the use of an optimal amount (4 %) of spherical alumina in the composition of ramming mullite-corundum mixes provides an increase in by 30 % in the cold crushing strength of samples made from them, fired at a temperature of 1580 °C, while maintaining at sufficiently high level indicators of their thermal shock resistance and slag resistance. The indicated alumina use in the composition of the MMK-90 mix during high-temperature firing of samples leads to an intensification of the mullite synthesis process. In fired samples from the MMKPBF mix, the spherical alumina forms a dense intergrowth of "felt-like" structure, which reinforces the structure, increasing the strength and thermal shock resistance of the samples.
 Indicators of physical and chemical properties of ramming mullite-corundum mixes of improved composition and samples made from them (for MMK-90 and MMKPBF mixes, respectively): chemical composition, wt. %: Al2O3 — not less than 90.0 and 85.0; SiO2 — within 3.2-5.0 and no more than 2.5; Fe2O3 — no more than 1.0 and 0.6; P2O5 — in the range of 2.5-3.5 and 0.5-1.0; grain size composition, mm — 3-0; cold crushing strength after firing at a temperature of 1580 °С — 110 and 70 N/mm2; thermal shock resistance — > 20 thermal cycles 950 °С — water.
 Ramming mullite-corundum mixes of improved composition are recommended for use in various heating units with high specific mechanical loads on the lining.

Phosphate solution wetting of graphite blocks for magnesium electrolysis to enhance their oxidation resistance. Part 1

Graphitized electrodes are broadly used in industry. However, when they are used in high-temperature operating environments, they are subject to oxidation, which can lead to abnormal operation or premature failure of an electrolytic cell. Use of protective coatings or special wetting solutions (melts) help increase the oxidation resistance of a wide assortment of components. It is obvious that a coating that covers an electrode completely will hinder or stop the electric current from flowing at the electrode/electrolyte boundary, which makes this technique inapplicable to anodes for magnesium electrolysis. Aqueous solutions of phosphates are widely used around the world to make materials more resistant to high-temperature oxidation due to the formation of glassy phases during drying. This paper examines the efficiency of using a mixture of zinc and aluminium dihydrophosphates dissolved in an aqueous solution of orthophosphoric acid to enhance the oxidation resistance of the graphite electrode EGP (NR). A comprehensive thermal analysis was carried out to examine the solution for suitability. And X-ray diffractometry helped verify the formation of crystals after the solution had been dried. Cube-shaped specimens with the side length of 50 mm were used in the experiments aimed at identifying optimum graphite wetting and drying conditions. Isopropanol was used as a surfactant to ensure proper wetting. The specimens were first subjected to vacuum degassing for air to be removed from the pores, and then they were soaked in a rarefied solution. A kinetic model was selected to describe the post-wetting drying procedure. The oxidation resistance was analyzed in a dynamic air flow. The experiments were carried out at 700 oC as it is the highest possible temperature for magnesium electrolysis. The results of the experiments showed that the above wetting technique, when applied in a laboratory environment, helped achieve a five-fold increase in the oxidation resistance of the model graphite electrodes. The authors looked at the feasibility of scaling the experiments and developing process circuits to produce graphite with high oxidation resistance.

The development of methods for the determination of residues of the insecticide pymetrozine in water, soil, cucumber and rape

Based on the literature data on the solubility of pymetrozine in water and organic solvents, as well as experimental data on the extraction of pymetrozine from water, soil and plant matrices, the optimal conditions for the extraction of pymetrozine from water; soil; cucumber; rape seeds, oil and green pods were selected. The conditions for cleaning extracts were selected as well. At the first stage, acetonitrile, a mixture of dichloromethane – isopropanol, or a mixture of dichloromethane – methanol in the presence or absence of inorganic salts were used for extraction of the pesticide. Pymetrozine was found to be a highly hydrophilic substance. For the purification of extracts of pymetrozine from plant matrices the extraction systems hexane – 0.02 mol/L aqueous solution of orthophosphoric acid, hexane or chloroform – aqueous solutions of ammonium sulfate were successfully used. The samples, obtained after this treatment, were pure enough to determine the residual amounts of pymetrozine in them at the maximum residue level (MRL), determined in Russia and the countries of the European Union, or lower using widespread liquid chromatography with diode-array (ultraviolet) detection.

Simultaneous determination of bisoprolol fumarate and rosuvastatin calcium in a new combined formulation by validated RP-HPLC

A simple, specific, and precise RP-HPLC method was developed and validated for simultaneous determination of Bisoprolol fumarate (BIS) and Rosuvastatin calcium (ROS) in new formulated tablets. The developed RP-HPLC method depended on chromatographic separation using C18 column (150×4.6 mm, 0.5 μm) with mobile phase consisted of acetonitrile and 0.05 aqueous solution of orthophosphoric acid at the ratio of 65:35 % (v:v) with a flow rate of 1 mL/min and UV detection was carried out at 230 nm. Factors affecting the developed methods were studied and optimized and the retention times for BIS and ROS were found to be 2.758 and 4.974 min, respectively. Linearity of the proposed method was observed over a concentration range 0.2-50 μg/mL for each of BIS (r = 0.9999) and ROS (r = 0.9998). The proposed method was successfully applied for the determination of the studied drugs in their bulk powder, laboratory prepared mixtures and in the formulated tablets. The developed method is the first chromatographic method for determination of those drugs and showed no significant difference when compared with the reported methods.

Behavioral Changes of Multipotent Mesenchymal Stromal Cells in Contact with Synthetic Calcium Phosphates in vitro

Migration, proliferation, and osteogenic differentiation of human adipose-derived (AD) multipotent mesenchymal stromal cells (MMSCs) during in vitro modeling of indirect contact with calcium phosphate (CP) or nanoparticles of synthetic hydroxyapatite (HA) have been studied. The results were registered with electrode (real-time cell analysis, RTCA) or visual (Cell-IQ) systems of long-term observation of cell cultures. Bulk specimens were use in a Cell-IQ® v2 MLF device as pure titanium substrates (10 × 10 × 1 mm3) covered by a CP relief (roughness index Ra = 2.4–4.4 μm) bilateral coating that was prepared by the micr-arc method from an aqueous solution of orthophosphoric acid (20 wt %), calcium carbonate (9 wt %), and synthetic HA (6 wt %). HA crystallites (1 mg/mL) were fabricated by mechanochemical synthesis and served as an irritant in RTCA investigation. The Cell-IQ system identified a 3.5- to 10-fold decrease in cell number at the interface with CP coatings with differing roughness during 14-day cell culturing. After 21 days, it was accompanied by a weak reduction of MMSC antigen expression (CD73, CD90, and CD105) as opposed to an increase in MMSC osteogenic differentiation and intercellular-matrix mineralization. In turn, HA nanodispersion reduced the speed of MMSC migration by 1.5 times (P < 0.001) during 25-h RTCA recording, which simulated cell invasion through the microporous membrane (8-μm diameter). Inhibition of migration and cell division with increased osteogenic differentiation of MMSCs has been suggested to be a possible effect of biodegradation products of synthetic CP materials.

Pulse Reverse Voltage Electropolishing of Superconducting Radio Frequency Niobium Cavities in Aqueous, Low Concentration Sulfuric Acid Electrolytes without Hydrofluoric Acid

Niobium superconducting radio frequency cavities (SRF) are required for the International Linear Collider as well as other high energy physics projects. In order for these cavities to achieve the required particle acceleration gradients, electropolishing is conducted as a final surface finishing operation. Conventional electropolishing of SRF cavities is based on the well-established viscous salt film paradigm [[1]] and utilizes a viscous electrolyte consisting of a mixture of sulfuric acid (95-98%) and hydrofluoric acid (49%) in a 9:1 volume ratio [[2]]. The concentrated is included to establish a thick, viscous boundary layer to result in surface brightening or smoothing [[3]]. The hydrofluoric acid is included to remove the niobium oxide film formed during electropolishing [[4]]. Previously we described efforts directed towards demonstrating an innovative electropolishing process for niobium coupons in low concentration (5%) aqueous sulfuric acid without hydrofluoric acid enabled by pulse reverse voltage waveforms electrolyte [[5],[6]]. The advantages of pulse reverse voltage electropolishing are summarized in in Figure 1. Specifically, the forward (anodic) pulse on-time and peak voltage are tuned to eliminate the need for concentrated sulfuric acid; the off-time is adjusted to dissipate heat, and the reverse (cathodic) pulse on-time and peak voltage are tuned to eliminate the need for hydrofluoric acid. In this contribution, we review and describe continuing efforts leading to the scale-up of the electropolishing process to single-cell and three-cell niobium SRF cavities [[7],[8]]. Finally, we present a first order economic comparison of the pulse reverse voltage low concentration aqueous sulfuric acid process compared to baseline concentrated sulfuric acid-hydrofluoric acid process [[9]]. Acknowledgements: The financial support of Faraday corporate, DOE P.O. No. 594128 and DOE Contract No. DE-SC0004588 is acknowledged. [1] Jacquet, P.A. (1936) On the Anodic Behavior of Copper in Aqueous Solutions of Orthophosphoric Acid. Trans. Electrochem. Soc. 69(1) 629-655. [2] Tian, H., Corcoran, S., Reece, C. and Kelly, M. (2008) The Mechanism of Electropolishing of Niobium in Hydrofluoric-Sulfuric Acid Electrolyte. J. Electrochem. Soc., 155, D563-568. [3] D. Landolt,(1987) “Fundamental Aspects of Electropolishing” Electrochimica Acta 32(1) 1-11 (1987). [4] MacDougall, B. (1995) “The Importance of Surface Oxide Films in Corrosion, Semiconductor and Environmental Research” Proceedings of the Symposium on High Rate Metal Dissolution Processes, Vol. 95-19, (Eds. M. Datta, B. MacDougall and J. Fenton) The Electrochemical Society, Pennington, NJ, pp 16-31. [5] M. Inman, E.J. Taylor, T.D. Hall “Electropolishing of Passive Materials in HF-Free Low Viscosity Aqueous Electrolytes” J. Electrochem. Soc., 160(9) E94-E98 (2013). [6] E.J. Taylor, M.E. Inman, T.D. Hall (2015) “Electrochemical system and method for electropolishing superconductive radio frequency cavities” U.S. Patent No. 9,006,147 issued April 14, 2015. [7] E.J. Taylor, T.D. Hall, M. Inman, S. Snyder (2013) “Electropolishing of Niobium SRF Cavities in Low Viscosity Aqueous Electrolytes without Hydroflouric Acid” Paper No. TUP054, Presented SRF2013, Paris, FRANCE. [8] A.M. Rowe, A. Grassellino, T.D. Hall, M.E. Inman, S.T. Snyder, E.J. Taylor (2013) “Bipolar EP: Electropolishing without Flourine in a Water Based Electrolyte” Paper No. TUIOC02, Presented SRF2013, Paris, FRANCE. [9] E.J. Taylor, M. Inman, T. Hall, S. Snyder, A. Rowe, D. Holmes (2015) “Economics of Electropolishing Niobium SRF Cavities in Eco-Friendly Aqueous Electrolytes without Hydrofluoric Acid” Paper No. MOPB092, Presented SRF2015, Whistler, CANADA. Figure 1

Growth of LiH2PO4 single crystals from phosphate solutions

Lithium dihydrogen phosphate (LiH2PO4, LDP) single crystals were grown from aqueous solutions of orthophosphoric acid. The influence of the concentration of the acid in the mother liquor on the solubility of LDP crystals and the conditions of their crystallization, was studied. The change of LDP solubility with the rise of the temperature was found to be not higher than 5mass%, irrespective of the acid concentration. The solubility diminished with the increase of the acid concentration in the mother liquor.The conditions of the growth of LDP crystals were analyzed from the viewpoint of the method of creation of the solution supersaturation, e.g. change of the acid concentration or evaporation of the solvent. The latter method is most optimal for the growth of LDP crystals from aqueous solutions of orthophosphoric acid. The habitus of the crystals was established to change with the rise of the acid concentration in the solution: the growth of the faces of the pyramid {111-} and the dome {011-} is suppressed, whereas the face of the pedestal {001-} continues to grow. The model of the influence of hydrogen bonds on the habitus of the crystals was considered.

Esterification of viscose fibres with orthophosphoric acid and study of their physicochemical and mechanical properties

Esterification of viscose fibres with aqueous solutions of orthophosphoric acid and urea at different ratios of components was investigated. It was shown that in phosphorylation of cellulose with these solutions, one-substituted cellulose phosphates are formed and a side process of formation of cellulose carbamates takes place together with accumulation of phosphate groups. A decrease was found in the mechanical strength of the phosphorylated cellulose preparations and the degree was a function of the concentration of orthophosphoric acid and urea as the phosphorylating solution. Phosphorus-containing viscose fibres (up to 0.5 mmole/g of phosphate groups) obtained in solutions of orthophosphoric acid and urea with a 0.25–0.63 and 3.33–4.17 M concentration have the most satisfactory mechanical properties and stability in phosphate buffer with pH 7.5.

Reaction of Cellulose with Aqueous Solutions of Orthophosphoric Acid

Experimental data were obtained that suggest that total amorphization of hydrated cellulose is attained in 79-80% aqueous solutions of H3PO4. The reaction of cellulose with aqueous solutions of H3PO4 is accompanied by selective sorption of molecules of the acid. Aqueous, especially concentrated, solutions of H3PO4 are characterized by low wetting power with respect to natural and hydrated cellulose.

Reaction of Cellulose with Aqueous Solutions of Orthophosphoric Acid. Structural and Chemical Aspects of the Reaction of H 3 PO 4 with Hydrated Cellulose Film

Total amorphization and formation of a trihydrophosphate complex precedes dissolution of cellulose in aqueous solution of H3PO4. With respect to absolutely dry polysaccharide, these conditions are attained in a large excess of 78.5 and 81.8% acids, respectively. The reaction of hydrated cellulose with 5-15% solutions of H3PO4 is accompanied by an increase in the molecular packing density, which attains the maximum value in 10% acid.

Improvement of white pinewood properties by impregnation with thiourea-formaldehyde resin and orthophosphoric acid

White pinewood was impregnated with thiourea–formaldehyde (TUF) resin and orthophosphoric acid (OPA) as a crosslinking agent. The best weight gains (55–138%) were obtained after impregnation with an aqueous solution of TUF resin for 1 h and impregnation with aqueous solutions of OPA at different concentrations for 1 h. Water uptake of treated wood was found to be 23% after a water-soaking test of 168 h, and a maximum antiswell efficiency was found to be 18% for a 85% OPA solution. Compression strength of the treated wood also improved with the highest value 62 KN/m2 for wood treated with a 70% OPA solution versus a value of 40 KN/m2 for untreated samples. Fire retardancy of the treated wood samples was also improved based on concentration of OPA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 390–397, 2000

Aluminosilicate air-hardening mortar solutions with elevated strength

A composition of air-hardening mortar solution consisting of mullite mortar of grade MML-62 moistened by an aqueous solution of orthophosphoric acid or liquid glass with a density of 1.2–1.25 g/cm3 is developed. The mortar solution has a good capacity for retaining water, does not condense in long-term storage (up to 12 h), and has high adhesion to refractory materials under cold conditions and after heat treatment at 1350°C in reducing and oxidizing media or in vacuum.

Phosphorus-31 and aluminum-27 NMR investigations of highly acidic, aqueous solutions containing aluminum and phosphorus

[sup 31]P and [sup 27]Al NMR spectroscopies have been used to characterize acidic, aqueous solutions of orthophosphoric acid, aluminum chloride, and tetramethylammonium (TMA) hydroxide. The final compositions of the solutions range from 0.1 to 1 mol % P, 0.0 to 20 mol % HCl, P/Al = 0.1 to 20, and P/(TMA)[sub 2]O = 2 to 20. Soluble aluminophosphate cations form reactions of hexaaqua Al monomeric cations, [Al(H[sub 2]O)[sub 6]][sup 3+], with phosphate ligands (i.e., H[sub 3]PO[sub 4], H[sub 2]PO[sub 4][sup [minus]], and acid dimers H[sub 6]P[sub 2]O[sub 8] and H[sub 5]P[sub 2]O[sub 7][sup [minus]]). [sup 31]P NMR spectra of aluminophosphate solutions reveal five distinct chemical shift regions. A correlation between the partial charge on P nuclei (calculated using semiempirical molecular orbital theory, MNDO [modified neglect of differential overlap]) and the [sup 31]P NMR chemical shift confirms the assignments of the [sup 31]P NMR resonances. Regardless of the total charge of the complex or the connectivity of the Al to -O-P units, the MNDO calculations show that P atoms in the same type of phosphate ligand bonded to Al monomers have similar partial charges, and, therefore, exhibit nearly identical [sup 31]P chemical shifts. [sup 27]Al NMR spectra of aluminophosphate solutions displaymore » four resonances. The assignment of the [sup 27]Al NMR resonances is based on the manner in which the [sup 27]Al and [sup 31]P NMR peaks change in intensity with pH, P, and Al concentration. Estimates of the number of Al-O-P bonds are calculated independently from [sup 31]P and [sup 27]Al NMR spectra and agree quite closely for a range of pH's and both Al and P concentrations. 44 refs., 17 figs., 3 tabs.« less

Spectroscopic and physicochemical characterization of P-Modified H-ZSM-5

Acidic properties of P-modified H-ZSM-5 have been characterized by means of ammonium exchange, temperature-programmed desorption of ammonia (NH 3 TPD), as well as IR, 27Al MAS NMR, and 31P MAS NMR spectroscopy. The introduction of phosphorus by impregnation of the zeolite with an aqueous solution of orthophosphoric acid decreases the number of Brønsted acid sites. Brønsted acidity can be restored completely by elution of the orthophosphoric acid with hot water. Only after calcination or steaming at elevated temperatures of the H 3PO 4-impregnated sample is an irreversible decrease of Brønsted acidity caused by dealumination observed. The formation of aluminum phosphates in nonframework positions proceeds simultaneously. Thermal treatment of H 3PO 4-impregnated H-ZSM-5 results in degrees of dealumination lower than those with non-impregnated samples, indicating that phosphorus partially protects aluminum ions from being removed from their substitutional positions in the silica framework.

Proton Longitudinal Relaxation Rates of Water in Aqueous Orthophosphoric Acid

Abstract Longitudinal relaxation rates of water protons were determined for aqueous solutions of orthophosphoric acid at concentrations up to 85% by weight, and their concentration dependence was investigated. An appropriate choice of variables yielded an essentially linear plot for concentrations up to at least 15% by weight. Deviations from linearity are discussed and are interpreted in terms of mass-law effects. The use of parameters of this plot for deriving values for correlation coefficients and for a hydration parameter is illustrated by application to observed data and data from the literature.

The mechanism of ?-caprolactam polymerization initiated with a concentrated aqueous solution of orthophosphoric acid

The mechanism of ?-caprolactam polymerization initiated with a concentrated aqueous solution of orthophosphoric acid

Caprolactam polymerization in the presence of aqueous solutions of orthophosphoric acid

Caprolactam polymerization in the presence of aqueous solutions of orthophosphoric acid

Thermodynamics of aqueous solutions of orthophosphoric acid from the freezing point to 298.15�K

The osmotic coefficients of aqueous phosphoric acid have been determined at 298.15°K, at 273.15°K, and at the freezing point, and for concentrations from about 10−4 m to 15 m. Phosphoric acid is incompletely dissociated even at very low concentrations, but it was possible to derived mean activity coefficients for the species H+ and H2PO 4 − by treating phosphoric acid as a 1-1 electrolyte.

Distribution coefficients of 52 elements on a strongly basic anion-exchange resin in aqueous solutions of orthophosphoric acid

Distribution coefficients of 52 elements on a strongly basic anion-exchange resin in aqueous solutions of orthophosphoric acid

Activity of phosphate ions measured with phosphate electrodes of the second kind

Phosphate electrodes of the second kind were employed to measure the activity of phosphate ions in aqueous solutions of orthophosphoric acid. The equation relating the emf with the activity of the various phosphate ions, which has been previously assumed to apply only under limited experimental conditions, is developed rigorously, and shown to be of general validity. The calculated results obtained by the use of the approximate equations developed agree well with the experimental values in the range of concentrations of phosphoric acid of 10 −2 to 10 −1 M. In the range of concentrations of phosphoric acid of 10 −4 to 10 M the activity of HPO 4 2− appears to be constant, and the change of emf between the phosphate electrodes and the H + electrodes is due only to the change in the activity of the hydrogen ions. The value of the phosphate electrodes of the second kind described in the literature appears to be limited, and considerable additional evaluation is necessary before they can be employed as reliable ion-specific reference electrodes.