Kinetics of armco iron dissolution in an anhydrous methanol and hydrochloric acid solution

The polarization behaviour of Armco iron in anhydrous solutions of CH₃OH+HCl and CH₃OH+HCl+LiCl was studied by the potentiostatic method. The following reaction orders were found for the anodic process: Z_a(Cl^?) = 1.7 –1.82 and Z_a(H⁺) = 0. The following mechanism of dissolution is proposed: Fe+Cl^? ? FeCl^?_ads, FeCl^?_ads+Cl^? → FeCl₂+2e (rate-determining step), FeCl₂?FeP²⁺ + 2Cl^?.     

The Effects of Halide Anions on the Partitioning Behavior of Pertechnetate in Polyethylene Glycolbased Aqueous Biphasic Systems

Abstract

The pertechnetate anion quantitatively partitions to the upper polyethylene glycol (PEG)-rich phase in aqueous biphasic systems (ABS) formed by the addition of aqueous high-molecular-weight PEG solutions to aqueous water-structuring salt solutions. Most metal cations partition to the salt-rich phase in these systems. Other matrix ions, such as those that might be present in real-world waste streams, affect the distribution ratios observed for TcO₄ ^?, however, the effects are not well understood. The halide ions F^?, Cl^?, Br^?, I^? represent a wide range of water-structuring to chaotropic ions. The heavier halide ions have distribution ratios above one and are observed to follow the order D_I > D_Br > D_Cl. These ions depress D_Tc. Fluoride saltsout PEG and thus partitions primarily to the salt-rich phase and fluoride increases D_Tc. These trends can be correlated with the ions' Gibbs free energies of hydration (ΔG_hyd), a measure of their interactions with water. Based upon these results, it is possible to predict which ions will depress, elevate, or not affect D_Tc for a given PEG-ABS based upon the matrix ion's Δ G_hyd.     

The automation of electrode kinetics — III. The dissolution of Mg in Cl−, F− and OH− containing aqueous solutions

The dissolution of Mg in Cl^?, F^?, and OH^? containing aqueous solutions has been investigated over a large potential range, from far into H₂ evolution at ? 3000 mV (sce) to the passive state at ? 1400 mV (sce). The steady state current-potential and the impedance have been measured using a new automatic electrochemical measurement system. An equivalent circuit and a least squares fitting procedure have been used to analyse the data. The resulting C_dl-E, θ-E, σ_Mg-E, R_w,-E, and the primary i-E and Z(ω)-E data are compared for each anion, and reveal details of the electrode kinetics of these complex dissolution reactions.     

Automation of electrode kinetics—V. The dissolution of Al in Cl− and F− containing aqueous solutions

The dissolution of Al in Cl^? and F^? containing aqueous solutions has been investigated over a wide potential range. The steady state current-potential curves and the impedance have been measured using a new electrochemical measurement system. Using an equivalent circuit the C_dl,-E,θ-E, σ_A1-E and R_w-E curves are derived and with the primary i-E and Z(w)-E data are compared for each anion.     

Study of the mechanism of additives on copper dissolution in monoethanolamine-complexed cupric ion solution

The dissolution of copper in monoethanolamine (MEA)-complexed cupric ion solution containing different additives was studied. Bridging ligands, such as F^–, Cl^–, Br^–, I^–, SCN^–, and oxidizers, including S₂O₈ ^2–, Cr₂O₇ ^2–, MnO₄ ^– were added to this nonammoniacal etching solution to increase the copper dissolution rate. Potentiodynamic methods were employed to elucidate the dissolution mechanism and the corrosion potential (E _corr) was found to shift from 10 to 90 mV as opposed to that of the original solution (0.045 M cupric sulfate and 0.225 M MEA) for bridging ligands. In contrast, some conventional oxidizers were also added in the etchant and the E _corr did not shift obviously. Therefore, we proposed that copper dissolution proceeds through an inner-sphere pathway in solution containing bridging ligands. The electron is transferred from the copper surface into the cupric species through the ligands, which greatly influences the copper dissolution rate. The order of effectiveness of these ligands is SCN^– > I^– > Br^– > Cl^– > F^–, which is related to their polarizability.     

The anodic dissolution of nickel—II. Bromide and iodide electrolytes

The kinetics of the anodic dissolution of nickel were studied in acidic bromide and iodide solutions using a potentiostatic sweep technique. The rate of dissolution is almost unaffected by the halide at low concentrations due to the presence of a prepassive film. At higher halide concentrations the prepassive film is removed and active dissolution occurs. The reaction is first order in Br^?, zero order in I^? and independent of pH for pH < 2. The Tafel slope is 82 mV, in accord with earlier work in chloride solutions.     

Electrode reactions of nickel(II) at mercury electrodes in aqueous solutions of pyridine at high ionic strengths

At high ionic strength the ion pair (NiPy²⁺₄, nX^?) or complex (NiPy₄X₂), n = 0, 1, 2; X^? = Cl^?, Br^?, SCN^?, N^?₃, F^?, NO^?₃, ClO^?₄; is adsorbed at the surface of mercury electrode. Under specified conditions in chloride, bromide, and thiocyanates solutions the electroreduction is preceded by a crystallization of a complex on the electrode surface. The inductive role of specifically coadsorbed Cl^? ions is discussed.     

Ion flotation and solvent sublation of cobalt cyanide complexes

An experimental investigation into the batch ion flotation of cobalt complex anions with the cationic surfactant, cetylpyridinium chloride is described. The concentration ratio of cetyl-pyridinium: cobalt in the foam was determined and found to be 2.0–2.7 for CoCl₂ plus KCN solution and 3.0–3.3 for K₃[Co(CN)₆] solution. Spectroscopic measurements of the former anion show that mainly [Co(CN)₅H₂O]²- anions were floated. The [Co(CN)₆]^3- flotation was established in the presence of Cl^?, Br^?, I^?, CN^?, NO₃^? and SO₄^2- anions. The accelerating influence of the ion flotation produced by the presence of Cl^?, Br^?, I^?, CN^?, NO₃^? and SO₄^2- increased as their partial molal volume increased. The solvent sublation of [Co(CN)₆]^3- anions was established in the presence of these anions.     

Pitting of nickel during anodic galvanostatic charging in Na2SO4 solutions

The anodic galvanostatic charging technique has been used to study the pitting of nickel in acid and neutral Na₂SO₄ solutions containing various concentrations of Cl^?. Pit initiation is indicated by a change in potential in the cathodic direction, this potential being substantially higher than that required to sustain pitting. The steady-state pitting potentials are in the passive, rather than the active, potential region, a result which can be explained by the highly localized nature of the pitting process. Increasing the [Cl^?] lowers the potential for pit initiation as well as the steady-state pitting potentials. The influence of anodic charging rate (i^g_a) on pit initiation depends on the [Cl^?] in solution; at high [Cl^?] the charging curves are similar except for the potential shift with i^g_a, while at low [Cl^?] pit initiation is more difficult with higher values of i^g_a. The minimum [Cl^?] required for pit initiation increases with decreasing solution temperature, ie with decreasing solution aggressiveness. The potential for pit initiation tends to be higher at lower solution temperatures and/or at higher pH's [Cl^?], anodic charging rate, solution temperature and pH influence pit initiation by affecting the efficiency of oxide repair at local breakdown sites in the passive oxide film.     

Anodic polarization behaviour of cast iron alloys in deaerated concentrated H3PO4 solutions containing Cl− and F− ions

The anodic behaviour of four cast iron alloys containing up to 16.7% Ni, in deaerated 60 wt% H₃PO₄ with and without 5 × 10^–3 M F^–, Cl^– ions and 1:1 Cl^–/F^– mixture was studied by the potentiostatic technique. Values of E _corr of the alloys are markedly influenced by their composition. The anodic behaviour in the active region is controlled by Fe in the alloys and the dissolution reaction is characterized by Tafel slopes, b _a, between 64 and 88 mV (decade)^–1. A two-electron transfer mechanism for the anodic dissolution is proposed. Passivation of the alloys is due to the formation of oxide layers including Fe₂O₃ and/or Fe₃O₄. Both critical and passive c.d. (I _cc and I _P) are markedly increased in the presence of Cl^– ions, but the presence of F^– ions inhibit the active dissolution of the alloys. The Tafel slope for oxygen evolution reaction (o.e.r.) in the transpassive region, is 240 ± 25 mV. In the proposed mechanism for the o.e.r., the rate determining step is an electron transfer reaction and possible interpretation of the high Tafel slopes is given based on the dual barrier model.     

Etude des phenomenes electrochimiques et des transports de matiere d'un systeme metal electrolytique: cas d'un disque tournant en cuivre dans des solutions aqueuses d'acide chlorhydrique

In the first two areas of the curves I = F(E) corresponding to Cu/CuCl_x^1?x and Cu/CuCl/CuCl_x^1?x redox systems we study the diffusion of Cl^?, Cu⁺ Cu²⁺ and CuCl_x^1?x species: in acidic chloride media (0,1 Ml^?1 ?HCl ? 3 Ml^?1) the diffusion of Cl^? does not exist because the amount of ions consumed is negligible compared to the large quantities contained in the solution, these HCl solutions behave like supporting electrolyte. Cu⁺ and Cu²⁺ does not exist in the diffusion layer on account of the high Cl^? concentration. At all events the diffusion of CuCl_x^1?x complex is the rate determining step. Experimental current is a pure diffusion current because the transference number tCuCl_x^1?x is negligible compared to one and the charge transfer step is very fast. The electrode surface seems to be uniformly reactive although for the Cu/CuCl/CuCl_x^1?x system we can assume there may be a partially blocked electrode surface constituted by independent sites.     

Potentiels biioniques de membranes liquides fortement dissociees

The liquid membranes are solutions in nitrobenzene of alkyl-trimethyl-ammonium salts which, in the concentration range studied, have a dissociation coefficient higher than 0·9. Biionic potentials obtained when opposing Cl^??Br^?, Br^??I^? and Br^??Pi^? are studied. The values of the parameters appearing in the mathematical expression of biionic potentials (ion mobility, standard chemical affinity of transfer from water to nitrobenzene) are determined.     

The enthalpies of formation and of dehydration of some AFm phases with singly charged anions

The enthalpies of formation of some AFm phases of the type Ca₂Al (OH) ₆X.xH₂O (X = Cl^?, Br^?, I^?, NO₃^?, ClO₄^?, ClO₃^?,BrO₃^?and IO₃^?) were determined by measuring the heats of solution in hydrochloric or perchloric acid. From the differences between the heats of solution of the compounds and their dehydration products, the enthalpies of dehydration were established. They increase with increasing enthalpies of hydration of the individual anions X in aqueous solution. However, this relationship is not the same for halide ions as for oxy-anions.     

A chromotropic acid modified SBA-15 as a highly sensitive fluorescent probe for determination of Fe<Superscript>3+</Superscript> and I<Superscript>−</Superscript> ions in water

A novel organic–inorganic hybrid nanomaterial (SBA-15-CA) was prepared by covalent immobilization of chromotropic acid onto the surface of mesoporous silica material SBA-15. Different techniques such as XRD, TEM, FT-IR, N₂ adsorption–desorption and TGA analyses were employed to characterize the grafting process. The data showed that the organic moiety (0.41 mmol g^?1) was successfully grafted to the SBA-15 and the primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. SBA-15-CA has been realized as a highly sensitive and selective fluorescent probe towards Fe³⁺ and I^? ions in aqueous media. SBA-15-CA exhibited a remarkable fluorescent quenching in the presence of Fe³⁺ ion over other competitive cations including Na⁺, Mg²⁺, Al³⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺ as well as I^? ion among a series of anions including F^?, Cl^?, Br^?, CO₃^2?, HCO₃^?, CN^?, NO₃^?, NO₂^?, SCN^?, SO₄^2?, H₂PO₄^?, HPO₄^2?, and CH₃COO^?. A good linear response was observed between the concentration of the quenchers (Fe³⁺ and I^? ions) and fluorescence intensity of SBA-15-CA with detection limits of 1.5?×?10^?7 M for Fe³⁺ and 0.2?×?10^?7 M for I^?. Moreover, the effects of various pH values on the sensing ability of SBA-15-CA were investigated. Finally, the proposed method was successfully utilized for the determination of Fe³⁺ and I^? ions in river water, well water and tap water samples.     

The dissolution of magnesium in Cl− and F− containing aqueous solutions

The rudiments of the corrosion of Mg in aqueous solutions containing Cl^? and F^? are investigated by linear potential sweep, potential pulse and impedance measurements. The changes in a film formed in an F^? containing solution and then placed in a Cl^? containing solution are followed by the impedance.     

Oxidation of iodide ions by means of cyclic voltammetry

From chronovoltammetric and cyclovoltammetric polarization curves three mechanisms of iodide ions have been established: 3I^? = I^?₃ + 2e,2I^?₃ = 3I₂ + 2e and 2I^? = I₂ + 2e under certain conditions of scan rate, concentration of iodide ions and area of electrode in the aqueous solutions KI (background solution 1 N Na₂SO₄) with half-wave potentials of 0.428, 0.489 and 0.507 V by silver/silver chloride electrode.     

The Partition Behavior of Zn(II) using Halide Ions Extractants in Aqueous Peg‐Based Two‐Phase Systems

Abstract

The partition behavior of Zn(II) has been studied in aqueous polyethylene glycol PEG(1550) – (NH₄)₂SO₄ two‐phase system using halide ions (Cl^?, Br^? and I^?) as extracting agents, at two different values of salt stock solution pH. The efficiency of extractants increase in this order: Cl^?>Br^?>I^?. The extracted species were estimated from the distribution coefficients' values determined as a function of halide ions concentration, and the “conditional extraction constants” were calculated. The experimental results suggest that the Zn(II) partition in presence of halide ions in such systems is the result of two competitive processes. The IR spectra of solidified PEG‐rich phases show that the passing of metal species into PEG‐rich phases bring a supplementary water contribution, which makes the extraction process to occurs until it reaches an “equilibrium state”, dependent on the hydrophobicity of these phases and not on the type of extracted metal species.     

Solid-liquid equilibria in concentrated aqueous salt solutions—systems with a common ion

A thermodynamic correlation is presented for solid-liquid equilibria in concentrated aqueous salt systems containing a common ion. It is assumed that no solid solutions are formed, although the solid phase can be a pure salt, a multiple salt or a hydrate. Predictions of solid-liquid equilibria in multicomponent systems are made using parameters calculated from solid-liquid equilibrium data for the constituent binary and ternary systems.Parameters are given for the prediction of solid-liquid equilibria in the aqueous system containing Na⁺, K⁺, Mg⁺⁺, NO^?₃, Cl^?, SO^--₄ from 0–50°C. These parameters correlate the available solid-liquid equilibrium data for ternary systems with an error in liquid-phase composition of less than 2 grams salt/100 grams H₂O. Errors are similar in the estimation of solid-liquid equilibria in four-component systems such as NaNO₃-NaC1-Na₂SO₄-H₂O.     

Cationic Polymerization of Epoxides using Novel Xanthenyl Phosphonium Salts as Thermo-latent Initiator

The present article describes the effect of steric and electronic factors on the efficiency of initiators based on novel xanthenyl phosphonium salts for cationic polymerization of epoxide monomers. 2-substituted (I_H, I_Cl, I_Me, and I_OMe) xanthenyl phosphonium hexafluoroantimonate were synthesized and characterized by NMR (¹H, ¹³C and ³¹P) and IR spectroscopy. The order of initiator activity in polymerization of glycidyl phenyl ether (GPE), was found as I_H> I_Cl>I_Me>I_OMe. To understand the effect of steric factor, the polymerization of cyclohexene oxide (CHO) was performed and the order of activity was found as I_Cl>I_H>I_Me >I_OMe. All the initiators were found to be latent at ambient temperature and initiates polymerization on thermal initiation. The order of initiator activity was influenced by electronic and steric factors in the system. The thermal stability of these salts was measured by Thermo gravimetric analysis (TGA). The solubility of the initiators in various organic solvents and epoxy monomers is also discussed.     

A kinetic model for the adsorption of gold from I2/I− solutions onto a porous polymer membrane

A model for the adsorption of gold from I₂/I^? aqueous solutions onto a cellulose acetate (CA)‐polyaniline (PANI) porous membrane is presented. The adsorption of gold is represented by an ion‐exchange overall reaction in which AuI₂^? ions replace the Cl^? ions at the active sites of the polyaniline matrix. The model incorporates the external mass transfer of AuI₂^? from the bulk solution to the membrane surface, followed by the pore diffusion of AuI₂^? to reach the active sites in the membrane. The overall ion‐exchange reaction was assumed to achieve local instantaneous equilibrium. Verification of the kinetic model with the experimental data showed that the effective diffusivity of AuI₂^? within the membrane is about 8.3 × 10^?6 cm²/s. The potential applications of the present formulation are discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012