Influence Of Phosphate Ions Research Articles

Influence of phosphate ions on passive film formation in amino acid-containing concrete pore solutions with chloride ions

There is need for development of highly effective green corrosion inhibitors to protect steel rebar. In the present study, 2 wt % L-arginine (LA: C6H14N4O2) with different amounts (i.e., 0.1, 0.25 and 0.50 wt %) of trisodium phosphate dodecahydrate (SP: Na3PO4∙12H2O) was used as an eco-friendly corrosion inhibitor in a simulated concrete pore (SCP) solution with 3.5 wt % NaCl to mitigate the corrosion of steel rebar. Steel rebar immersed in 2 wt % LA with 0.25 wt % SP (i.e., L2P2 solution) exhibited excellent corrosion resistance by forming P-zwitterion-(Cl)–Fe, zwitterion-(Cl)–Fe, and FePO4 complexes as uniform and protective passive films. However, SP concentrations lesser or greater than 0.25 wt % with 2 wt % LA exhibited a reduction in total impedance. The small amount of SP could not form and stabilize the P-zwitterion-(Cl)–Fe complex, whereas a large amount caused competition between P-zwitterion-(Cl)–Fe and zwitterion-(Cl)–Fe complexes where phosphate ions interfere with the formation of P-zwitterion-(Cl)–Fe. Therefore, a proper concentration of phosphate ions is required to form and stabilize the P-zwitterion-(Cl)–Fe and FePO4 complexes. Density functional theory (DFT) and molecular dynamic (MD) simulation results suggest that the energy gap (ΔE) for formation of LA-P (C6H13O5N4P: N(ω)-phosphonato-L-Arginine) is high, and it tends to strongly adsorb from amino acid groups and carbon chains until N–P bonds are formed.

Influence of phosphate ions on pit initiation and growth on the stainless steel – 316L in chloride contaminated simulated coal gasification wastewater (CGW) environment

The influence of phosphate ions on the pitting corrosion of stainless steel type 316L was investigated with electrochemical and thermo-chemical methods. DC polarization measurements showed that the pitting could occur spontaneously above 72 °C on SS-316L in chloride containing simulated coal gasification waste water (CGW). Addition of phosphate ions above critical pitting temperature (CPT) in the simulated CGW retarded the oxygen reduction reactions, reduced the pitting frequency and impeded the pitting growth considerably. EIS study revealed that the PO43− ions enhanced the pitting resistance of SS-316L by absorbing and modifying the passive film through the interaction with the hydrated Fe species. XRD analysis of SS-316L surface exposed in simulated CGW containing PO43− ions at 170 °C further confirmed the existence of iron phosphate in the surface corrosion layer.

A thermal, sorptive and spectral study of HDTMA-bentonite loaded with uranyl phosphate

The influence of phosphate ions on the thermal stability of complexes obtained by adsorption of uranium(VI) on organobentonite was determined. Organoclay samples were prepared by the reaction of hexadecyltrimethylammonium bromide with bentonite. The isotherms of sorption/desorption of U(VI) from aqueous solutions containing phosphate ions onto different forms of bentonite were measured using the batch method. The highest amount of uranium was absorbed on HDTMA-bentonite in the presence of phosphates. This may have been associated with the complexing of U(VI) ions by phosphate ions, which interacted with surfactant cations probably via electrostatic forces. A TG–DSC–MS study showed that the thermal decomposition of the surfactant sorbed on bentonite proceeded in two stages: at 200–400 and at 600–800 °C. The first stage involved defragmentation and oxidation of surfactant cations present in the interior and on the surface of the mineral. The second stage involved oxidation of charcoal and simultaneous dehydroxylation of the sorbent. The oxidation of surfactant cations and the dehydroxylation of the mineral were suppressed in the presence of phosphates.

Influence of phosphate ion on the morphology, adhesion strength, and corrosion performance of zirconium-based surface treatment

In this study, the effect of phosphate ion (PO4 3−) was investigated on the different properties of a zirconium-based nanoceramic conversion layer. At the first step, the phosphate ion concentration was optimized using the DC polarization technique. In the next step, the surface morphological aspect of the bare and treated mild steel was evaluated utilizing field emission scanning electron microscopy technique. The results indicate formation of a composite conversion coating on the mild steel surface. Practical adhesion strength between treated mild steels and an epoxy resin was studied by pull-off adhesion test. Finally, the effect of phosphate ion on the corrosion properties of epoxy-coated mild steel was evaluated utilizing electrochemical impedance spectroscopy. It was revealed that the phosphate ion could increase both the adhesion strength and anticorrosion properties of the epoxy-coated substrate.

Influence of phosphate ions on buffer capacity of soil humic acids

Influence of phosphate ions on buffer capacity of soil humic acidsThe object of this study was to determine change of natural buffer capacity of humic acids by strong buffering agents, which were phosphate ions. Studies were carried out on the humic acids extracted from peat soils. Additional information was obtained by determination of water holding capacity, density, ash and pH for peats and optical parameter Q4/6for humic acids. Humic acid suspensions exhibited the highest buffer properties at low pH and reached maximum at pH ~ 4. Phosphates possessed buffer properties in the pH range from 4.5 to 8.0. The maximum of buffering was at pH~6.8 and increased proportionally with an increase in the concentration of phosphate ions. The study indicated that the presence of phosphate ions may strongly change natural buffer capacity of humic acids by shifting buffering maximum toward higher pH values. Significant correlations were found for the degree of the secondary transformation with both the buffer capacity and the titrant volume used during titration.

Adsorption kinetics of proteins in plastic microfluidic channels: Real-time monitoring of lysozyme adsorption by pulsed streaming potentials

A proof-of-concept study is presented illustrating the real-time monitoring of lysozyme (Ly) adsorption on the surface of microchannels made with cyclic olefin copolymer (COC). The signal arises from changes in the surface charge upon adsorption of Ly which is monitored by pulsed streaming potentials. Because streaming potentials are electrochemical potentials resulting from the pressure-driven flow of the liquid and the surface charge of the microchannel, this approach is ideal for microfluidics. Initial adsorption rates showed a linear correlation with the bulk concentration of [Ly] in the range between 7.0 and 350 nM. Fitting of the adsorption isotherms allowed the estimation of equilibrium and rate constants of adsorption. The influence of phosphate ions on the adsorption kinetics of Ly was also investigated. Unlike the steady flow used in conventional streaming potential measurements, the present approach incorporates pulsed flow and the ability to inject finite samples into the microfluidic stream. The pulsed flow allows the use of non-reference electrodes which removes the need for special electrolytes to stabilize the electrode potentials. Likewise, the injection permits monitoring of adsorption and desorption events in real time. The label-free monitoring of these events and the high sensitivity of the adsorption kinetics of Ly to solution species found in this work indicates that this method could be applicable to study protein–protein interactions.

Influence of Phosphate Ions on the Stability of Amorphous Calcium Carbonate

Amorphous calcium carbonate (ACC) occurs with varying stabilities in different organisms. It is thought that the stability is influenced by certain ions and proteins. We describe here a study investigating the particular influence of phosphate ions on the stability of ACC. Synthesised ACC was treated with different concentrations of Na2HPO4 and molar ratios of PO4:Ca ≥ 12:1 were shown to be effective in preventing crystallisation of ACC to calcite. The nature of the resulting sample is discussed.

Temperature-induced denaturation of ribonuclease S: a thermodynamic study.

In this paper the thermal denaturation of ribonuclease S, the product of mild digestion of ribonuclease A by subtilisin, is deeply investigated by means of DSC and CD measurements. It results that at whatever pH in the range 4-7.5 the process if fully reversible but not well represented by the simple two-state N<-->D transition. Actually, a two-state model that considers both unfolding and dissociation, NL<-->D + L*, well accounts for the main features of the process: the tail present in the low-temperature side of DSC peaks and the marked dependence of denaturation temperature on protein concentration. This mechanism is strictly linked to the exact stoichiometry of RNase S. An excess of the protein component of RNase S, the so-called S-protein, shifts the system toward a more complex behavior, that deserves a separate treatment in the accompanying paper [Graziano, G., Catanzano, F., Giancola, C., & Barone, G. (1996) Biochemistry 35, 13386-13392]. The thermodynamic analysis leads to the conclusion that the difference in thermal stability between RNase S and RNase A is due to entropic effects, i.e., a greater conformational flexibility of both backbone and side chains in RNase S. The process becomes irreversible at pH 8.0-8.5, probably due to side-reactions occurring at high temperature. Finally, the influence of phosphate ion on the stability of RNase A and RNase S at pH 7.0 is studied and explained in terms of its binding on the active site of ribonuclease. The analysis enables us to obtain an estimate of the apparent association constant and binding enthalpy also.

Influence of phosphate ion on the fluorescence of 3-fluorotyrosine

3-Fluorotyrosine fluorescence is quenched effectively by phosphate ions not only by a dynamic but also by a static mechanism owing to H-bond complex formation in ground state. 3-Fluorotyrosine pKa values both in the ground and first excited state (8.3 and 4, respectively) are appreciably lower than those of tyrosine, thus promoting 3-fluorotyrosinate ion formation in the excited state. Additional emission owing to 3-fluorotyrosinate ion (near 350 nm) may be taken erroneously for tryptophan fluorescence.

Influence of phosphate ions and alkaline phosphatase activity of cells on survival ofEscherichia coli in seawater

When grown in a minimal medium and suspended for 2 hours in distilled water, seawater, phosphate buffer or a polyphosphate solution,E. coli MC4100 cells with high alkaline phosphatase activity survived in seawater for longer periods than cells with low or no activity. However, mutant cells totally deprived of alkaline phosphatase activity held in phosphate-containing media before transfer to seawater showed survival almost as high as the wild type strain, indicating that alkaline phosphatase activity is not the only factor influencing survival. Alkaline phosphatase activity also increased the protection of cells provided by glycine betaine. Survival was enhanced when cells were preincubated in the presence of phosphate or polyphosphate. Thus, the transfer of cells in wastewater could influence their subsequent survival in seawater.

The influence of phosphate ions on the polarisation behaviour of iron

The polarisation behaviour of pure iron electrodes in weakly acid, deaerated perchlorate solutions with addition of phosphate ions has been investigated, using a rotating disc electrode and recording medium-fast potentiodynamic sweeps. Current transients resulting from potential-steps are also reported. This dissolution of slightly etched iron electrodes was shown to proceed via two reaction paths, with inherently different characteristics, one at low and the other at high anodic potentials. At low concentrations of phosphate ions both reactions show a positive reaction order with respect to phosphate, while at higher concentrations the process at low potentials show a negative value and the other process a value close to zero. The influence of phosphate ions on a third anodic reaction path, alternative to the reaction at low potentials, as well as on the cathodic reaction is reported.

Kinetics and Mechanism of Extraction of Nickel(II) with 6-(2-Thiazolylazo)naphthol

The kineticsof extraction of nickel()from aqueous solution, using chloroform solution of 6 (2-thiazolylazo)naphthol(TAN), was studied spectrophotometrically in the pH range 5.8. v7.1and at an ionic strength pt=O.1.In a su Lciently high sha: ki: ng speed region, the extraction was co: ntro11ed by a chemical reaction in the aq ueo us phase. The reaction wasof rst-order with respect tonicke1(), s order with respect to TAN and inversely, first-order with respect to hydrogen ion, which indicated that the formation of 1: 1 chelate in aqueous phase was the rate-determining step. The rate constant of this reaction was found to be 2.5 1061, mol-i, sec-i at 2980K.The higher rateof the nicke1() TAN complexation reaction than t: hat of the reaction in similer nicke1()systems, already reported, was discussed in terms of a model in which the loss of the first water molecule, coordinated to nickel in the outer-sphere complex, was the rate-determining step. The influence of phosphate ion, added to the aqueous phase as a buffer agent, on the rate of extraction was expelled.Th6 temperature dependence on the formation rate of the 1: 1 chelate was determined and thermodynamic data have been calculated. These values are E.: 13. O k al/mol, aH: 12.4kcal/mol, dF: 8.5 kcal/mol and AS: 13. O e. u.