Effect Of Phosphate Ions Research Articles

Effect of Phosphate Ions on the Dianion–Anion Equilibrium of Fluorescein Excited State

Effect of Phosphate Ions on the Dianion–Anion Equilibrium of Fluorescein Excited State

Effect of phosphate ions on the formation of iron oxide/hydroxide as a stabilizer

Hematite (α-Fe2O3) nanoparticles were synthesized using a facile precipitation method under mild conditions by adding phosphate anions (PO43−). The solid-state phase transformation of α-Fe2O3 nanoparticles follows dehydration and internal rearrangement of ferrihydrite initially precipitated at a high pH, while PO43− ions acted as a stabilizer for preventing the dissolution of ferrihydrite. This phase transformation resulted in tiny spherical α-Fe2O3 nanoparticles with a size of approximately 5 ​nm, which is similar to that of the initial ferrihydrite. Conversely, acicular goethite (α-FeOOH) nanoparticles were formed without PO43− ions by dissolution and recrystallization of ferrihydrite. Furthermore, anions such as sulfate (SO42−) and chloride (Cl−) had no significant effect on the α-Fe2O3 formation due to their low Lewis basicity, resulting in an acicular α-FeOOH structure. These results extend the possibility to synthesize α-Fe2O3 nanoparticles, which could have various practical applications.

Rare-earth leaching from Florida phosphate rock in wet-process phosphoric acid production

Phosphorite, or phosphate rock, is the most significant secondary rare-earth resource. It contains high amounts of phosphate-bearing minerals along with low contents of rare earth elements (REEs). In Florida, about 19 Mt of phosphate rock are mined annually and most are used to manufacture fertilizers using a wet process, in which sulfuric acid reacts with phosphates to produce phosphoric acid and phosphogypsum. In the wet process, REEs are also leached out into solution and eventually get lost in the leaching residue and phosphate fertilizer. Recovering REEs from Florida phosphate rock in the wet process will be beneficial to broadening rare-earth availability, improving the quality of phosphoric acid product and protecting the environment. This study focuses on the influences of wet-process operating conditions on REE leaching efficiency. The results indicate that REE leaching efficiency increases with phosphoric acid addition in the initial pulp. At a temperature of 75 °C, a stoichiometric ratio of sulfuric acid (H2 SO4) to calcium oxide (CaO) of 1.05 and a weight ratio of liquid to solid of 3.5, REE leaching efficiency reached a relatively high value of 52.82 percent. The trends of REE leaching efficiency were similar to those for phosphoric acid (P2O5). Extensive tests on the leaching residue showed that during leaching, about 90 percent of the REEs were released from the phosphate rock but only 52.82 percent ended up in the leaching solution. This phenomenon can be attributed to two factors: (1) the effect of phosphate ions (PO 4 3- ) in the solution, which caused REE ions to form REE phosphates and be precipitated into the leaching residue, and (2) the influence of large amounts of anions such as sulfate (SO 4 2- ), dihydrogen phosphate (H2 PO 4 - ) and hydrogen phosphate (HPO 4 2- ) anions as well as the polar molecule H3 PO4, which surrounded the REE cations and formed an ion atmosphere that prevented the PO43- from contacting and combining with REE cations. Interaction of these two opposite effects determined the REE distribution between leaching solution and residue.

Nanocube-based hematite photoanode produced in the presence of Na2HPO4 for efficient solar water splitting

A thin film of α-Fe2O3 on FTO substrate has been synthesized from hydrothermal process in an aqueous solution of FeCl3 and Na2HPO4. A nanocube structure of α-Fe2O3 is observed within the formed hematite films and coated with phosphate ions on the surface. For comparison, another phosphate modified hematite film has been prepared by soaking the bare hematite film in Na2HPO4 solution. A negative electrostatic field can be built up on the surface of both phosphate modified hematite which will promote charge separation and extraction of photoexcited holes to the electrode surface. It is found that different types of phosphate complex exist in the hematite films, which has been determined by the isoelectric point (IEP) of the hematite films, and consequently influences the formation and strength of the electrostatic field. The effects of phosphate ions on the morphology, surface characteristics and the photoelectrochemical properties of the hematite thin films are investigated and the mechanism is proposed.

A novel approach to synthesize hollow α-Fe2O3 spheres via hydrothermal treatment

Novel α-Fe2O3 hollow crystal spheres were formed on a large scale by a facile and efficient hydrothermal process. In this paper, the inorganic anions are important in the formation of α-Fe2O3. And the concentration of H2PO4− is important for forming hollow spheres. The coordination effect of phosphate ions with Fe3+ ions is another important aspect in the formation of hollow spheres. H2PO4− is important for forming hollow structures. The samples were characterized by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction.

Effect of phosphate ions on preparation of fly ash based geopolymer

An experimental investigation was conducted to study the performance of fly ash based geopolymer specimens in Sodium Aluminium Phosphate solution. High strength geopolymer is produced from coal combustion fly ash and sodium aluminium phosphate chemical which can be obtained by hydrated alumina powder reacting with ortho phosphoric acid and sodium hydroxide. The curing is done by both atmospheric and accelerated means. Performance of the specimens was evaluated in terms of visual appearance, change in compressive strength, phase development and micro-structural analysis over the exposure period of time. Evidence is provided with micro structural studies and mechanical strength properties on the presence of amorphous binding phase. These characteristics are similar to alumino-silicate geopolymer.

Phosphate Inhibition Effect on Chloride-Induced Crevice Corrosion of Alloy 22

ABSTRACTAlloy 22 has been extensively studied regarding its crevice corrosion (CC) resistance both in pure chloride solutions and in solutions containing different oxyanions that may act as inhibitors of crevice corrosion. The scope of this work was to study the general and localized corrosion behavior of Alloy 22 when phosphate ions were added to a 1 M NaCl solution at 90°C. Results from the electrochemical tests indicate that the size of the passive potential range and the localized corrosion repassivation potential value increased in the presence of phosphate ions. Results from creviced specimens showed a strong inhibition effect of phosphate ions on the chloride induced crevice corrosion of Alloy 22. The critical molar concentration ratio (RCRIT = [phosphate]/[Cl]) to inhibit crevice corrosion was 0.3.

Ternary [Al 2O 3–electrolyte–Cu 2+] species: EPR spectroscopy and surface complexation modeling

Cu 2+ binding on γ-Al 2O 3 is modulated by common electrolyte ions such as Mg 2+, SO 4 2 - , and PO 4 3 - in a complex manner: (a) At high concentrations of electrolyte ions, Cu 2+ uptake by γ-Al 2O 3 is inhibited. This is partially due to bulk ionic strength effects and, mostly, due to direct competition between Mg 2+ and Cu 2+ ions for the SO − surface sites of γ-Al 2O 3. (b) At low concentrations of electrolyte ions, Cu 2+ uptake by γ-Al 2O 3 can be enhanced. This is due to synergistic coadsorption of Cu 2+ and electrolyte anions, SO 4 2 - and PO 4 3 - . This results in the formation of ternary surface species ( SOH 2SO 4Cu) +, ( SOH 2PO 4Cu), and ( SOH 2HPO 4Cu) + which enhance Cu 2+ uptake at pH < 6. The effect of phosphate ions may be particularly strong resulting in a 100% Cu uptake by the oxide surface. (c) EPR spectroscopy shows that at pH ≪ pH PZC, Cu 2+ coordinates to one SO − group. Phosphate anions form stronger, binary or ternary, surface species than sulfate anions. At pH ≫ pH PZC Cu 2+ may coordinate to two SO − groups. At pH ≪ pH PZC electrolyte ions SO 4 2 - and PO 4 3 - are bridging one O-atom from the γ-Al 2O 3 surface and one Cu 2+ ion forming ternary [ γ-Al 2O 3/elecrolyte/Cu 2+] species.

Effects of phosphate ions on dissolution rate of calcite

Effects of phosphate ions on dissolution rate of calcite

Protein adsorption on needle-shaped hydroxyapatite prepared by hydrothermal treatment of mixture composed of CaHPO4 2H2O and .BETA.-Ca3(PO4)2

The behavior of protein adsorption on needle-shaped hydroxyapatite (HAp) crystals was investigated and compared with that on irregularly shaped HAp crystals in phosphate buffer solutions. The proteins used were bovine serum albumin (BSA) and lysozyme chloride (LSZ). The effect of phosphate ions in the buffered solutions was evaluated at concentrations in the range 2-200 mol·m-3. In 50 mol·m-3 or lower buffer concentrations, the saturated amount of BSA adsorbed on needle-shaped HAp was greater than that on irregularly shaped HAp. The saturated amount of BSA adsorbed on needle-shaped HAp decreased with increasing phosphate buffer concentration. This resulted in little difference in BSA adsorption between the needle-shaped HAp and the irregularly shaped HAp at phosphate concentrations of 100 mol·m-3 or higher. In contrast, the saturated amount of adsorbed LSZ increased with increasing phosphate buffer concentrations up to 10 mol·m-3 and subsequently decreased with increasing phosphate concentrations between 10 and 200 mol·m-3. There were no differences in the protein adsorption behaviors between the needle-shaped HAp and irregularly shaped HAp at a phosphate concentration of 200 mol·m-3. A specific adsorption, useful for the separation of BSA and LSZ proteins was observed for the needle-shaped HAp at a low phosphate buffer concentration. This separation was caused by the large a-face surface area of the needle-shaped HAp by comparison with that of the irregularly shaped HAp.

Effect of phosphate ions in the properties of titania sol-gel

Sol-gel titania was phosphated in two different ways: i) “in situ” phosphation using phosphoric acid as hydrolysis catalyst in the titanium butoxide gelling system, and ii) gelling with nitric acid and impregnation with ammonium phosphate solution. In calcined samples at 600°C a positive effect on the specific surface area for the “in situ” phosphated sample was found. X-ray diffraction patterns showed that the presence of phosphates ions stabilized the anatase phase. FTIR-pyridine adsorption identified only Lewis acid sites in phosphated samples. In the isopropanol decomposition for “in situ” phosphated titania, the activity was six times higher than that obtained for titania phosphated by impregnation, showing strong acidity for the in situ phosphated TiO2 catalyst.

Effects of phosphate ions on intergranular pressure solution in calcite: An experimental study

Intergranular pressure solution (IPS) is a coupled chemical-mechanical process of widespread importance that occurs during diagenesis and low-temperature deformation of sedimentary rocks. Laboratory experiments on IPS in halite, quartz, and calcite have largely concentrated on the mechanical aspects of the process. In this study, we report the effects of pore fluid chemistry, specifically varying phosphate ion concentration, on the mechanical compaction by IPS of fine-grained calcite powders at room temperature and 1 to 4 MPa applied effective stress. Phosphate was investigated because of its importance as a biogenic constituent of sea and pore waters. Increasing the pore fluid phosphate concentration from 0 to 10 −3 mol/L systematically reduced compaction strain rates by up to two orders of magnitude. The sensitivity of the compaction strain rate to phosphate concentration was the same as the sensitivity of calcite precipitation rates to the addition of phosphate ions reported in the literature, suggesting that the rate of IPS in phosphate-bearing samples was controlled by calcite precipitation on pore walls. The results imply that IPS and associated porosity/permeability reduction rates in calcite sediments may be strongly reduced when pore fluids are enriched in phosphates, for example, through high biologic productivity or a seawater origin. Future modeling of IPS-related processes in carbonates must therefore take into account the effects of pore fluid chemistry, specifically the inhibition of interfacial reactions.

Effect of phosphate ions on electrochemical behaviour of copper in sulphate solutions

Abstract The effect of phosphate ions on the corrosion behaviour of copper in sulphate solutions was investigated at different temperatures (293, 313, 333, and 353 K) and at different pH values (pH = 2·1, 7·2, and 12·3). A three electrode electrochemical technique was used for the measurements, using a saturated calomel electrode (SCE) for reference purposes. Both anodic and cathodic polarisation curves were established, from which the anodic and cathodic Tafel constants were determined. Corrosion potentials were determined by extra trapolation of the anodic and cathodic Tafel lines to the point of zero current density. The results showed that for a pH value of 2·1, the corrosion rate of copper showed a marked tendency to increase with increasing temperature in solutions containing either sulphate alone or sulphate plus phosphate. However, at pH values of 7·2 and 12·3, this tendency became less pronounced in solutions containing sulphate alone and in solutions containing sulphate plus phosphate together, ...

Electrodeposition of silver from nitrate solution: Part II. Mechanism of the effect of phosphate ions

The mechanism of compact Ag-film formation by electrolysis from nitrate solution with addition of small amounts of phosphate ions is elucidated. It is shown that the phosphate ions exert their effect by lowering the exchange current density. Consequently, the radii of nucleation exclusion zones also diminishes, thus producing conditions stimulating electrodeposition of continuous thin Ag-film.

A simple spectrophotometric determination of submicromolar quantities of vanadium oxyions.

Widespread interest has developed in the study of vanadium as an essential nutrient [l] and as a possible regulator of several ATP hydrolysing enzymes [2-41 in mammalian species. Available methods for the determination of vanadium are costly [l, 5, 61, complex [7-121, and of very low sensitivity [13, 141. Oxyvanadium species are known to react with molybdic acid in the presence of phosphate to form a heteropolymolybdate complex [ 15, 161. The complex, molybdivanadophosphoric acid, is characterized by a yellow colour that maximally absorbs light at 385 nm. The intensity of colour resulting from the formation of this heteropoly complex has been shown to vary with changes in the concentration of inorganic phosphate. The dependence of the reaction on the concentration of vanadium oxyions has not been evaluated. In the present study we examined the possibility that the intensity of yellow colour development resulting from the reaction of oxyvanadium with molybdic acid and phosphate may vary as a function of oxyvanadium concentration. The effect of phosphate ions and the pH of the medium on the colour intensity were also investigated. The study included the stoichiometric determination of the composition of the complex species. Experimental

Effects of Phosphate Ions on Copper Dissolution and Passivation

The dissolution and passivation of copper was studied in the presence of phosphate and phosphate + chloride in aqueous solution at pH 8 for temperatures ranging from 5 to 60°C. The copper oxidation current increased with (i) the concentration of phosphate ions in chloride‐free solutions, (ii) the concentration of chloride ions in solution containing phosphate ions, and (iii) the temperature in both solutions. Two passivation mechanisms are postulated. Below 30°C, a protective base layer of Cu(II) compounds was formed while between 30 and 60°C a porous layer of a Cu(I) compound was formed first on the electrode surface followed by the growth of Cu(II) passive film. The presence of Cu(II) compound was necessary to slow down the copper dissolution. High [phosphate]/[chloride] ratio was favorable for the formation of a thin, compact, passive layer while a high [chloride]/[phosphate] ratio led to the precipitation of a thick porous protective deposit on the copper surface.

ChemInform Abstract: Effect of Phosphate Ions on the Surface Chemistry and Microstructure of Amorphous Alumina.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effect of phosphate ions on the surface chemistry and microstructure of amorphous alumina

High-surface-area amorphous Al2O3–AlPO4 samples (P/Al ratio: 0–0.17) have been prepared by reductive decomposition of aluminium nitrate in the presence of phosphoric acid. The materials obtained are amorphous up to 1100–1200 K and present “zeolitic-type” monomodal microporosity (r= 10–15 A). They are weakly acidic. The Lewis acidity changes from being weak (associated with octahedrally coordinated Al3+ ions) to being strong by increasing P content due to the formation of tetrahedral Al3+ ions induced by phosphate species. Bronsted sites are also present; these are associated with phosphate species. The catalytic activity in methanol dehydration increases with P content up to P/Al = 10/90. P inhibits both the crystallization of the γ-alumina phase and the γ- to α-alumina phase transition.

Structuring of H1 histone. Evidence of high-affinity binding sites for phosphate ions

Circular dichroism studies show that low concentrations of phosphate ions induce folding of the H1 histones. Sulfate and perchlorate anions have effects similar to phosphate indicating the presence on H1 histones of binding sites with high affinity for ions with tetrahedral geometry. In fact, the structuring efficiency of different ions, as determined by the midpoint value of the effect/concentration curve, is 0.05 M for NaCl, 0.005 M for NaClO4, 0.001 M for sodium phosphate and 0.0003 M for sodium sulfate on H1 histone from Chaetopterus variopedatus sperm chromatin. Phosphate shows similar folding efficiency also on calf thymus and on sea-urchin sperm H1 histones. The effect of phosphate ions on the H1 molecule is observed also by differential absorption spectroscopy in the region of absorption of amino acid side-chains. Binding studies by gel filtration chromatography on Sephadex columns show that phosphate binding occurs in the presence of structuring concentrations of sodium chloride. About 9 ATP molecules bind to H1 histones derived from non-active cell chromatins while only 3.5 ATP molecules bind to H1 derived from active somatic chromatins. The fluorescence of the tyrosine residues of Chaetopterus sperm H1 is enhanced by chloride ions and heavily quenched by phosphate ions in correlation with structuring of the molecule, demonstrating direct interactions between tyrosine residues and phosphate ions. The defined and limited number of phosphate groups bound per histone molecule, the high affinity of the interaction and the effect on the structure of the histone suggest the participation of phosphate groups in the binding of H1 histones to DNA.

亜硫酸カルシウム水和物の生成に与えるリン酸イオンの影響および球晶の多層構造

亜硫酸カルシウム水和物の生成に与えるリン酸イオンの影響および球晶の多層構造