Iodide Ion Concentration Research Articles

Electrophoretic deposition of ceramic coatings from modified suspensions of microsized powders of doped BaCeO3 and BaCeO3–BaZrO3 proton-conducting electrolytes

This work investigates the influence of molecular iodine introduced as a charging agent into the suspensions based on the BaCe0.8Sm0.19Cu0·01O3 (BCSCuO), BaCe0·5Zr0·3Y0.1Yb0.1O3-δ (BCZYYbO) and BaCe0.89Gd0.1Cu0·01O3-δ (BCGCuO) proton-conducting electrolytes at concentrations up to 1.0 g/L on their electrokinetic properties. The peculiarities of changes in zeta potential, pH, conductivity of the suspensions, the thickness and morphology of the coatings depending on the amount of iodine added are determined. It has been established that when the iodine concentration increases to 1 g/L, the electrical charge of the particles and the sign of the zeta potential undergo a reversal. Additionally, there is a natural decrease in the pH value towards the acidic side and a corresponding increase in the suspension conductivity. The research has demonstrated that in the suspension with a high iodine content (1 g/L), cathodic and anodic deposition can occur simultaneously under electrophoretic deposition (EPD) conditions at low voltage values (below 8 V). However, as the voltage increases, only cathodic deposition occurs. Therefore, the impact of altering the type of the EPD is threshold in nature relative to the magnitude of the EPD voltage. It has been shown that in order to practically implement EPD of ceramic coatings from modified suspensions of microsized powders of doped BaCeO3 and BaCeO3–BaZrO3 proton-conducting electrolytes, it is necessary to select a small amount of added iodine (0.1–0.2 g/L) to initiate a stable deposition process and to ensure continuity and uniformity of the coatings. This article discusses possible mechanisms of zeta potential inversion, electrophoretic mobility, and the EPD nature under conditions of high concentrations of iodide ions in the suspension bulk. The experiments have demonstrated the viability of the EPD process for the formation of a uniform BCSCuO coating (∼10 μm) on a supporting NiO–BCSCuO anode substrate using an iodine-modified suspension. This coating was subsequently sintered into a dense ceramic film at 1450 °C. In addition to the fundamental significance, the study results have implications for the practical use to improve and simplify the thin-film SOFC technology.

Evaluation and strategy for improving the quality of desalinated water.

Seawater desalination is practiced in many coastal countries, which is accepted as clean water by the general populations. The untreated seawater reported high concentrations of bromide (50,000 - 80,000µg/L) and iodide (21 - 60µg/L) ions, which are reduced to non-detectable levels during thermal desalination while the concentrations of bromide and iodide ions were reduced to 250-600µg/L and < 4-16µg/L, respectively during reverse osmosis processes. During the treatment and/or disinfection, many brominated and iodinated disinfection byproducts (Br-DBPs and I-DBPs) are formed in desalinated water, some of which are genotoxic and cytotoxic to the mammalian cells and possible/probable human carcinogens. In this paper, DBPs' formation in desalinated and blended water from source to tap, toxicity to the mammalian cells, their risks to humans and the strategies to control DBPs were investigated. The lifetime excess cancer risks from groundwater, and desalinated and blended water sourced DBPs were 4.15 × 10-6 (4.72 × 10-7 - 1.30 × 10-5), 1.75 × 10-5 (2.58 × 10-6 - 5.25 × 10-5) and 2.59 × 10-5 (4.02 × 10-6 - 8.35 × 10-5) respectively, indicating higher risks from desalinated and blended water (2.56 and 4.51 times respectively) than groundwater systems. Few emerging DBPs in desalinated/blended water showed higher cyto- and genotoxicity in the mammalian cells. The findings were compared with safe drinking water standards and strategies to produce cleaner desalinated water were demonstrated.

ИСПОЛЬЗОВАНИЕ СЕРЕБРОСОДЕРЖАЩИХ НАНОКОМПОЗИТОВ ДЛЯ ОПРЕДЕЛЕНИЯ ЙОДИД-ИОНОВ

At present, the interest of analytical chemists in metal-containing nanocomposites has increased significantly. This is primarily due to the possibility of their application as optical sensors. The operation of such sensors is based on the phenomenon of surface plasmon resonance (SPR). The result of this study is the development of a new sensitive method for the determination of iodide ions based on the use of paper modified with silver nanoparticles (NPs). Iodides, oxidized under the action of special reagents, form molecular iodine, which is extracted by an air flow and transferred to a sensitive paper layer containing NPs. The interaction of NPs with iodine leads to traceable optical changes. The limit of detection (0.01 mg/L) and the range of determined concentrations (0.03–0.3 mg/L) of iodide ions were determined.

Use of ionic liquids for extraction separation and concentration of iodide ions in brine samples.

Iodine in natural salt waters such as iodine-rich underground brine generally exists as iodide ions, and to extract iodide ions, it is necessary to oxidize them to nonpolar iodine molecules. In this study, we report that iodide ions in natural brine containing high concentrations of chloride ions can be quantitatively extracted without oxidation by extraction using ionic liquids. Extraction with the ionic liquids trihexyltetradecylphosphonium chloride and trioctyl ammonium chloride was found to be able to enrich trace amounts of iodide in brine samples up to 40- and 100-fold, respectively. The selectivity coefficients for I- over Cl- determined in this study clearly show that the ionic liquids have much higher I-/Cl- selectivity than typical strongly basic anion exchangers. Extraction with trihexyltetradecylphosphonium chloride was applicable as a preconcentration method for iodine determination by XRF analysis. Iodide ions extracted with trioctyl ammonium chloride were quantitatively stripped with an aqueous alkaline solution. These results indicate that ionic liquid extraction is useful for the separation and concentration of iodide from brines.

Adsorption of iodide ions at the Bi(1 1 1) | propylene carbonate + dimethyl carbonate interface

• The interface Bi | PC + DMC was studied by impedance measurements. • Adsorption of I - anions was studied at the Bi(1 1 1)| PC + DMC interface. • The adsorption parameters of I - anions have been calculated. • Adsorption of anions is stronger from pure carbonates than from solvent mixtures. The adsorption of I - anions on the Bi(1 1 1) single crystal plane from mixed solutions of propylene carbonate and dimethyl carbonate (1:1) has been investigated with impedance measurements. Both electrode charge and electrode potential were applied as the independent electrical variables in the calculations of the ionic charge due to the specific adsorption following the mixed-electrolyte method. The Gibbs energy of I - anions adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions, the standard Gibbs energy values obtained at constant electrode potential and at constant electrode charge, are coincident and the Gibbs energy of I - anion adsorption in the mixture is only slightly lower than in the pure propylene carbonate or ethylene carbonate solutions. However, at higher concentrations of iodide ions, the specific adsorption charge values in the mixture are remarkably lower than in pure propylene carbonate caused by different lateral repulsion values of iodide ions on the electrode surface in different systems. The electrosorption valency values have been calculated and it was found that this parameter is higher in the mixture than in pure propylene carbonate or in other organic carbonate solvents.

Effects of seawater intrusion on the formation of disinfection byproducts in drinking water

Seawater contains high levels of halides, which can increase the concentrations of bromide and iodide ions in coastal groundwater and surface water sources. Intrusion of seawater alters the chemistry of fresh water leading to the formation of additional brominated and iodinated disinfection byproducts (DBPs), many of which are cyto- and genotoxic to the mammalian cells, and have cancer risks to humans. In this study, effects of seawater intrusion on the formation of trihalomethanes (THMs), and haloacetic acids (HAAs) were investigated by spiking groundwater using 0.0–2.0% seawater (by volume) and liquid chlorine as disinfectant. The concentrations of bromide and iodide ions in groundwater (0.0% seawater) were 42.5 and non-detected (ND) μg/L respectively, which were increased up to 1100 and 2.1 μg/L respectively, following mixing with 2.0% seawater. The regulated THMs (THM4) were increased from 30.4 to 106.3 μg/L while iodinated THMs (I-THMs) were increased from 0.13 to 1.6 μg/L respectively due possibly to molecular substitution and additional pathways of THMs formation. Bromoform was increased from 0.5 to 94.3 μg/L while iodoform was increased from ND to 1.02 μg/L. HAAs were increased from 27.9 to 72.9 μg/L where tribromoacetic acid was increased from 2.0 to 43.7 μg/L. In 0.0% seawater, bromine incorporation factor (BIF) for THM4 and HAAs were 0.077 and 0.050 respectively, which were increased to 0.942 and 0.38 at 2% seawater respectively. For dihalogenated HAAs (X2AA) and trihalogenated HAAs (X3AA), BIF in 0.0% seawater were 0.098 and 0.14 respectively, which were increased to 0.863 and 0.924 for 2.0% seawater respectively. Mixing of 2.0 seawater increased the toxicity of THM4, HAAs and I-THMs by 4.2, 5.9 and 201.8 folds, respectively indicating the importance of reducing seawater intrusion into the freshwater sources. Further, alteration of water sources and/or adaptation of advanced treatment can assist in lowering the risks.

Schiff base complexes of Cu(II) and Ni(II) derived from N,N'-bis(salicylidene)-o-phenylenediamine as potential ionophores in the construction of PVC membrane iodide sensors

Two Schiff base compl exes of Cu(II) and Ni(II),designated as M1 and M2, respectively were synthesized from N,N'-bis(salicylidene)-o-phenylenediamine and characterized by IR and NMR spectroscopy. The results of conductometric and stability constant revealed that these complexes with several anions created the possibility of their use as potential ionophores in the development of iodide selective sensors. Poly(vinyl chloride)(PVC) membrane sensors of these complexes using several plasticizers (o-NPOE, CN, TBP, DOP and DBP) and cationic additive (CTAB) were fabricated as well as examined for the detection of iodide ions in aqueous solution. The performance characteristics of the various sensors of these ionophores exhibited that sensors having membrane composition as M1(4 mg):PVC(34 mg):TBP(62 mg):CTAB(7 mg) and M2(4 mg):PVC(34 mg):TBP(62 mg):CTAB(5 mg) showed best characteristics regarding Nernstian slope (59.4 and 59.2 mV decade−1 of [I-]), linear working range (6.3 ×10−8-3.2 ×10−2 mol L−1 and 7.9 ×10−8-1.0 ×10−2 mol L−1), detection limit (3.8 ×10−8 mol L−1 and 5.6 ×10−8 mol L−1) and response time of 7 and 9 s, respectively. These sensors performed well in the pH range of (4.0–9.0) and showed adequate shelf lives with 20% (v/v) non-aqueous tolerance. The proposed sensors served as indicator electrodes in the potentiometric titration of iodide ions against silver nitrate solution and in the determination of iodide ion concentration in mouthwash and river water samples.

Role of the injected water salinity and ion concentrations on the oil recovery in carbonate reservoirs

Low salinity water flooding (LSWF) was initially considered using water with a low concentration of dissolved salts and was later extended to include modifying the ionic content of injected brines. This work investigates the effects of changing water salinity and composition along with the concentration of sulfate and iodide ions on oil recovery in carbonate reservoirs during the tertiary recovery stage. An experimental study was carried out using crude oil of 29°API, 8 core samples extracted from the Eocene carbonate reservoir (Egypt), and 6 different water salinities.The results showed additional oil recovery up to 5% of the original oil in place (OOIP) in the tertiary recovery stage with changing water salinity and water composition. Injection of high salinity (HS) and low salinity (LS) brines with high sulfate concentrations increased the incremental oil recovery by a value ranging from 1.7 to 3.8% of the OOIP. On the contrary, injection of HS and LS brines with low sulfate concentrations showed insignificant incremental oil recovery (less than 1% of the OOIP). Furthermore, injection of water with potassium iodide (KI) after injection of water with high sulfate brines showed additional oil recovery of about 1.7% of the OOIP. On the other hand, injection of water with KI after injection of water with low sulfate concentration showed insignificant incremental oil recovery (less than 0.4% of the OOIP).The concentration of sulfate in the injected water appeared to be key parameter to achieve effective waterflooding (WF) projects in carbonate reservoirs. Moreover, the results revealed that the multi-component ion exchange (MIE) mechanism seems to be the primary recovery mechanism for LSWF in carbonate reservoirs. The results and conclusions of this study can be used to develop guidelines for designing waterflooding projects in carbonate reservoirs with optimum salinity.

Eco-friendly and reagent recyclable gold extraction by iodination leaching-electrodeposition recovery

Although iodination gold leaching is a clean, non-toxic and efficient non-cyanide gold leaching process, it still has the problems of high reagents cost and difficult leaching solution treatment. To solve these problems, a process of iodination leaching-electrodeposition recovery was proposed. Thermodynamic analysis confirmed the feasibility of iodination gold leaching, and the influence of different factors on gold leaching was studied. The result shows that roasting could effectively improve the gold leaching effect, the concentration of initial iodine and initial iodide ion had a significant effect on the gold leaching, and the gold leaching could be achieved under normal temperature and neutral conditions. The kinetic analysis shows that the gold leaching process conforms to the shrinkage kinetics model, and the control step was the solid film diffusion control. The apparent activation energy of this reaction was 8.642 kJ/mol, and the reaction order of initial iodine concentration and initial iodide ion concentration were 0.72 and 0.52, respectively. Gold was recovered from the leaching solution by electrodeposition with a recovery percentage of more than 99%. More importantly, the iodine was formed in the anode area, in other words, the reagents used for gold leaching were enriched in the anode area during the gold recovery process. The recovery percentage of iodine in the anode area reached 83%, and the anolyte could be recycled. This process fundamentally solves the problem of high cost of iodination leaching.

CsPbBr3 Perovskite–Coated Paper Substrate for the Cost‐Effective Detection of Fluoride, Chloride, and Iodide Ions in Water

Developing a simple and cost‐effective substrate for the detection of the halide ions present in water is extremely important due to their adverse effects at higher concentrations. A good substrate should behave differently in the presence of different halide ions. Herein, a CsPbBr3‐coated paper substrate is used for the detection of fluoride, chloride, and iodide ions. As a result of the fast anion exchange reactions, in the presence of each halide ion, the CsPbBr3‐coated paper shows different emission behaviors. The presence of chloride and iodide ions results in blueshifted and redshifted absorption and emission, respectively. In the presence of fluoride ions, anion exchange followed by decomposition of the perovskite nanocrystal is observed. The anion exchange reactions of CsPbBr3 perovskites are faster than the moisture‐induced decomposition, which enables the detection of micromolar concentrations of fluoride, chloride, and iodide ions in water.

Kinetic study of carbonylation of ethanol to propionic acid using homogeneous rhodium complex catalyst in the presence of diphosphine ligand

Carbonylation of ethanol is a potentially attractive route for propionic acid production, while its industrial practice is greatly hampered by the low space-time yield. To improve the reaction rate of ethanol carbonylation, a series of diphosphine ligands were investigated in the homogeneous rhodium complex catalyst system. The catalyst activity and stability were enhanced by using bis(diphenylphosphino)methane monosulfide (dppmS) as hemilabile diphosphine ligand and the space-time yield of propionic acid was increased significantly. In the presence of dppmS, not only the effect of ligand addition, the content of ethyl iodide, lithium iodide, and rhodium catalyst on catalytic performance were carried out, but also the reaction conditions were systematically investigated in a titanium alloy autoclave reactor. Consequently, the carbonyl space-time yield reached 6.21 mol·L−1·h−1 under the optimal reaction conditions. Additionally, the corresponding mechanism of ethanol carbonylation with addition of dppmS was proposed. A kinetic model of the reaction was established in the temperature range of 433–473 K. The reaction orders of catalyst, ethyl iodide, and iodide ion concentrations were determined to be 0.86, 0.36, and 0.20, respectively. The activation energy was found to be 25.23 kJ·mol−1. Residual error distribution n and a statistical test showed that the kinetic model is reasonable and acceptable.

Ionic chromatographic determination of iodides, nitrites and bivalent iron in water with amperometric detector

Introduction. The majority of ionic chromatographic methods approved in our country for assessing the quality and chemical safety of water for the content of controlled anions and cations are developed using conductometry. However, quantitative determination of micro concentrations of cations and anions in drinking water and other water bodies against the background of macro concentrations of other components due to their interfering influence by the method of conductometric ion-chromatographic analysis is not possible. Material and methods. The tap water in Nothern East Administrative district of Moscow was used. The “Stayer” ion chromatograph with amperometric and conductometric detectors and separating columns was used. The column Phenomenex Star Ion A-300 100/4.6 was used for the determination of iodide. The column Shodex IC SI-52 4E 250/4, 6 was used for the determination of nitrite. The column Shodex IC YS-50 150/4.6 was used for the determination of bivalent iron. Results. Chromatograms of ion chromatographic analysis with amperometric and conductometric detections of tap water with different contents of target ions are presented. It is shown that it is impossible to determine the target components using the standard method with conductometric detection. The content of accompanying ions (chlorides, nitrates, and sulfates), exceeding the concentration of nitrite and iodide by tens of thousands of times, was not prevented by the determination. Discussion. The high efficiency of the proposed method for determining iodides, nitrites, and bivalent iron is provided due to their anode discharge in the electrochemical cell of the detector. Interfering components (chloride, nitrate, phosphate, and sulfate) neither participate in the anodic oxidation process and nor generate an electrical signal; that allows determining micro concentration of nitrite and iodide ions and bivalent iron in virtually any aqueous system containing an excess of chlorides, nitrates, sulfates. Conclusion. Authors proposed a highly sensitive ion - chromatographic amperometric determination of iodide, nitrite ions and bivalent iron in water and other water bodies. It allows eliminating the interfering influence of macro concentrations of accompanying components. The determination is performed by direct insertion of the sample into the chromatographic system.

Influence Factors on Photochemical Production of Methyl Iodide in Seawater

Methyl iodide (CH3I) is an important trace greenhouse gas in the atmosphere and an ozone-depleting substance. The influence of different environmental factors, such as the duration of illumination; the strength of illumination; the concentrations of humic acid, ferric ion (Fe3+), and iodide ion (I−); and pH, on the photochemical production of CH3I in artificial seawater (ASW) were tested by simulated solar irradiation. In addition, Yangtze River Estuary waters from inshore to offshore were used to explore the relationship between the photochemical production of CH3I and different sources of dissolved organic matter (DOM) in natural sea-water (NSW). The results revealed that higher concentrations of humic acid and I−, as well as higher strengths of illumination and longer illumination durations, promoted the photochemical formation of CH3I in ASW. The addition of Fe3+ accelerated the photochemical production of CH3I, but high concentrations of Fe3+ inhibited the formation of CH3I. Experiments on NSW obtained from the Yangtze River estuary spiked when concentrations of DOM were high, confirming that DOM plays an important role in facilitating the photochemical production of CH3I within the Yangtze River Estuary. The photochemical production of CH3I in the seawater was significantly higher under light conditions relative to dark conditions, indicating that illumination accelerated the production of CH3I.

Use of silver\u2013bentonite in sorption of chloride and iodide ions

Ag–bentonite was prepared by ion exchange process to sorb iodide and chloride ions in batch experiments. The modified bentonite was examined with XRF and XRD. 75% of the cation exchange capacity was exchanged by silver ions. It was found that the sorption of chloride ions is an exothermic precipitation process because the solubility decreases with increasing temperature. In the case of iodide sorption, the dissolution of AgI was observed under high concentration of non-radioactive iodide ions, which is well known in analytical chemistry. The phenomenon occurs not only in the bulk aqueous phase but also in the interlayer space of montmorillonite.

Superior Resonant Nanocavities Engineering on the Photonic Crystal-Coupled Emission Platform for the Detection of Femtomolar Iodide and Zeptomolar Cortisol.

Although luminescence spectroscopy has been a promising sensing technology with widespread applications in point-of-care diagnostics and chem-bio detection, it fundamentally suffers from low signal collection efficiency, considerable background noise, poor photostability, and intrinsic omnidirectional emission properties. In this regard, surface plasmon-coupled emission, a versatile plasmon-enhanced detection platform with >50% signal collection efficiency, high directionality, and polarization has previously been explored to amplify the limit of detection of desired analytes. However, high Ohmic loss in metal-dependent plasmonic platforms has remained an inevitable challenge. Here, we develop a hybrid nanocavity interface on a template-free and loss-less photonic crystal-coupled emission (PCCE) platform by the quintessential integration of high refractive index dielectric Nd2O3 "Huygens sources" and sharp-edged silver nanoprisms (NPrs). While efficient forward light scattering characteristics of Nd2O3 nanorods (NRs) present 460-fold emission enhancements in PCCE, the tunable localized plasmon resonances of NPrs display high electromagnetic field confinement at sharp nanotips and protrusions, boosting the enhancements 947-fold. The judicious use of silver NPr (AgNPr) metal-Nd2O3 dielectric hybrid resonances in conjugation with surface-trapped Bloch surface waves of the one-dimensional photonic crystal (1DPhC) displayed unprecedented >1300-fold enhancements. The experimental results are validated by excellent correlations with numerical calculations. The multifold hotspots generated by zero and nonzero nanogaps between the coassembly of NPrs, NRs, and 1DPhCs are used for (i) determination of hyper and hypothyroidism levels through monitoring the concentration of iodide (I-) ions and (ii) single-molecule detection (zeptomolar) of the stress hormone, cortisol, through the synthesized cortisol-rhodamine B conjugate obtained using a simple esterification reaction.

A developed cloud point extraction method for Tl(III) determination by flame atomic absorption spectrometry

ABSTRACT Tl(III) was extracted and preconcentrated using cloud point extraction (CPE) for its determination in water samples using flame atomic absorption spectrometry (FAAS). The CPE procedure was performed using a non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) as an extractant at room temperature in the presence Br− or I−. Tl(I) was oxidized in presence of bromine water to T(III) to form Tl(Br)3 complex which then was extracted into the surfactant-rich phase. The factors influencing the CPE such as sample pH, concentrations of bromide and iodide ions and Triton X-114 were studied. After optimisation of CPE conditions, the preconcentration factors were found 74 for Br2 and 68 for KI, the limits of detection (3 s) were 5.7 and 8 ng mL−1 for Br2 and KI, respectively. The relative standard deviation (RSD) was 3.7% for Br2 and 2.6% for KI. The results showed that the proposed method was free from interference. The CPE method was successfully used for Tl(III) determination in real samples.

Kinetic study on the carbonylation of ethanol to propionic acid using homogeneous Rh complex catalyst at low water content

The catalytic system for ethanol carbonylation consists of rhodium with hydroiodic acid, ethyl iodide and lithium iodide as promoters exhibited an attractive catalytic activity at low water content (< 4.6 wt%). The effects of catalyst components and process conditions on the reaction were studied by comparing the products selectivity and the carbonyl space–time yield (STY) of the catalytic systems. The results demonstrated that the optimum catalyst system was composed of 10 wt% ethyl iodide, 1400 ppm rhodium iodide and 10 wt% lithium iodide with an appropriate reaction temperature of 453 K and pressure as 3.0 MPa, achieving an almost 100% conversion of ethanol, 96% selectivity of propionic acid and the STY as 2.20 mol L−1 h−1. The mechanism of ethanol carbonylation in the presence of lithium iodide was proposed and the macroscopic kinetic model of the reaction was established in the temperature range of 443–463 K. The reaction orders with respect to CO pressure (≥ 2.2 MPa), catalyst, ethyl iodide and iodide ion concentrations were found to be 0, 1.00, 0.81 and 0.18. The activation energy was found to be 34.01 kJ mol−1. The results of significance test and residual analysis showed that the kinetic equation is suitable.

ON THE TECHNOLOGY FOR PRODUCING IODINE FROM OILFIELD PRODUCED WATER OF OIL-AND-GAS CONDENSATE FIELDS AND ENVIRONMENTAL SAFETY

The study of the ozonation reaction of iodide ions in mineralized waters with bromine, iron ions has established patterns of change in the degree of iodine formation from acidity, water mineralization, changes in the concentration of these ions, ozonation time, and molar-ion ratio of the reactants. In the above privacy, with increasing ozonation time, the degree of iodine formation first increases, reaches a maximum value under the given conditions, and then decreases. Similar patterns are observed with a decrease in the acidity of the medium, a change in the concentration of iodide ions, and an increase in the molar-ion ratio. It was found that with an increase in the contact surface of the phases, the degree of formation of iodine increases, which indicates mass transfer as a limiting stage of the ozonation process. Based on the experimentally found changes in the reagent concentration, the ozonation rate was estimated. The results of the study can be used to create a more environmentally friendly technology for the extraction of iodine from oilfield produced water of oil-and-gas condensate fields. A simplified scheme for producing iodine is proposed.

Kinetic Approach to the Reduction of Ethylenediaminetetraacetatoferrate(III) Complex by Iodide Ion in Aqueous Acidic Medium

The kinetic approach to the reduction of ethylenediaminetetraacetatoferrate(III) complex (hereafter [Fe(III)EDTA]-) by iodide ion has been studied spectrophotometrically in an aqueous acidic medium. The study was carried out under pseudo-first order conditions of an excess of iodide ion concentration at 28 ± 1, ionic strength (I) = 0.43 coulomb2 mol dm-3 (KNO3) and [H+] = 5.0 10-2 mol dm-3. The [Fe(III)EDTA]- complex was reduced according to the reaction;&#x0D; 2[Fe(III)EDTA]- + 2I- → 2[Fe(II)EDTA]2- + I2&#x0D; The rate law is - d[Fe(III)EDTA-]/dt = (a + b[H+])[Fe(III)EDTA-][I-]&#x0D; The rate of the reaction is first order in oxidant and reductant concentrations, and displayed positive Brønsted-Debye salt effect. On the basis of catalysis by added cation, Michaelis-Menten plots and the absence of intermediates, the outer-sphere electron transfer mechanism is proposed for the reaction.

Influence of iodide ions on corrosion of dual‐phase steel in sulfuric acid solution

Potassium iodide was studied for its corrosion inhibition property on the corrosion of dual‐phase steel in 0.5 M sulfuric acid at 25°C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy was used to characterize the steel surface. The inhibition efficiency increases with the concentration of iodide ions. The thermodynamic parameters Kads and ΔG0ads are calculated and discussed. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.