Presence Of Ferric Ions Research Articles

Goethite as a more effective iron dosage source for mineralization of organic pollutants by electro-Fenton process

The electro-Fenton process is an electrochemical method for wastewater treatment based on the production of hydroxyl radicals via H 2O 2 generation in the presence of ferrous ions. The aim of this work is to show the use of a new mineral iron dosage source (goethite, α-FeOOH) for electro-Fenton process that achieves a more efficient mineralization treatment. Our new proposed Goethite catalyzed electro-Fenton (GEF) process yields 95% of mineralization for an organic model pollutant such as aniline under optimum standard electro-Fenton (SEF) conditions. For that, GEF process uses only 2 ppm of soluble iron, compared with the 55 ppm of soluble iron used by SEF process. In order to show the potential scope of GEF process, the effect of goethite concentration, solution conductivity, solution pH, temperature, and applied current density are studied in detail.

Design, synthesis and redox properties of two ferrocene-containing iron chelators

Two ferrocene-containing iron(III) chelators were synthesized from desferrioxamine B and kojic acid and their electronic absorption and electrochemical properties were studied in acetonitrile in the absence and presence of ferric ions. The results show a complex behavior arising from the occurrence of competing redox and complexation processes. Such systems are a first step toward the generation of chemosensors for the electrochemical detection of iron(III) in a solution.

Effects of ferrous ions on the reductive dechlorination of trichloroethylene by zero-valent iron

The surface characteristics of zero-valent iron (ZVI) and the efficiency of reductive dechlorination of trichloroethylene (TCE) in the presence of ferrous ions were studied. The experimental results indicated that the acid-washing of a metallic iron sample enhanced the efficiency of TCE degradation by ZVI. This occurred because acid-washing changed the conformation of oxides on the surface of iron from maghemite (γ-Fe 2O 3) to the more hydrated goethite (α-FeOOH), as was confirmed by XPS analysis. However, when ferrous ions were simultaneous with TCE in water, the TCE degradation rate decreased as the concentration of ferrous ion increased. This was due to the formation of passive precipitates of ferrous hydroxide, including maghemite and magnetite (Fe 3O 4), that coated on the surface of acid-washed ZVI, which as a result inhibited the electron transfer and catalytic hydrogenation mechanisms. On the other hand, in an Fe 0-TCE system without the acid-washing pretreatment of ZVI, ferrous ions were adsorbed into the maghemite lattice which was then converted to semiconductive magnetite. Thus, the electrons were transferred from the iron surface and passed through the precipitates, allowing for the reductive dechlorination of TCE.

Glow Discharge Induced Hydroxyl Radical Degradation of 2-Naphthylamine

In an aqueous solution, normal electrolysis at high voltages switches over spontaneously to glow discharge electrolysis and gives rise to hydroxyl radical, hydrogen peroxide, and aqueous electron, as well as several other active species. Hydroxyl radical directly attacks organic contaminants to make them oxidized. In the present paper, 2-naphthylamine is eventually degraded into hydrogen carbonate and carbon dioxide. The degradation process is analyzed by using an Ultraviolet (UV) absorption spectrum, high-performance liquid chromatography (HPLC) and chemical oxygen demand (COD). It is demonstrated that 2-naphthylamine (c0 =30 mg·l-1) is completely converted within 2h at 30°C and 600 V by glow discharge electrolysis, and the degradation is strongly dependent upon the presence of ferrous ions. COD is ascended in the absence of ferrous ions and descended in the presence of them.

Electrodeposition, characterisation and mathematical model of nickel–iron film in a parallel plate flow system

Nickel–Iron alloy films were electrodeposited in a parallel plate flow system. The volumetric flow rate of electrolyte was fixed at 12 dm3 min−1 through the 1 cm thick and 9 cm wide slit parallel plate. Fluid velocity was ca 0.22 m s−1 under fully turbulent convective flow. Alloy films with iron content varying from 7·5 to 40 wt-% were deposited as a function of solution pH, temperature, bath ingredient concentration and applied current density. It is shown that the magnetic property is strongly correlated to the alloy content: the saturation moment, Bs, increases with the iron composition, while the coercivity, Hc, increases with nickel content. Current efficiency increases with pH and applied current density. The nickel deposition rate is inhibited in the presence of ferrous ion in the plating bath. The microhardness of the deposit is increased as the iron content is increased over the range studied. A mathematical model that considers the convective mass transfer of Fe(II) and Ni(II) species in the diffusion layer, the competition of adsorbed metal species on surface active sites, and Tafel electrochemical kinetics describe the alloy plating system well.

Interactions of Ferric Ions with Olive Oil Phenolic Compounds

The ferric complexing capacity of four phenolic compounds, occurring in olives and virgin olive oil, namely, oleuropein, hydroxytyrosol, 3,4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA), and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA), and their stability in the presence of ferric ions were studied. At pH 3.5, all compounds formed a reversible 1:1 complex with ferric ions, but hydroxytyrosol could also form complexes containing >1 ferric ion per phenol molecule. At pH 5.5, the complexes between ferric ions and 3,4-DHPEA-EA or 3,4-DHPEA-EDA were relatively stable, indicating that the antioxidant activity of 3,4-DHPEA-EA or 3,4-DHPEA-EDA at pH 5.5 is partly due to their metal-chelating activity. At pH 7.4, a complex containing >1 ferric ion per phenol molecule was formed with hydroxytyrosol. Oleuropein, 3,4-DHPEA-EA, and 3,4-DHPEA-EDA also formed insoluble complexes at this pH. There was no evidence for chelation of Fe(II) by hydroxytyrosol or its derivatives. At all pH values tested, hydroxytyrosol was the most stable compound in the absence of Fe(III) but the most sensitive to the presence of Fe(III).

Kinetic and reaction mechanisms of calcium bisulfite catalytic oxidation

In this paper, the oxidation of calcium bisulfite in the presence of ferrous ions as a catalyst is studied in a laboratory scale apparatus at a fixed oxygen partial pressure (21.3 kPa) and at a temperature of 45 °C. The analysis of the experimental results, carried out by using the theory of mass transfer with chemical reaction, indicates that the slow reaction regime has been explored, and the transition from the kinetic to the diffusional subregime identified. A kinetic analysis allows to develop a reaction rate equation, assuming that the bisulfite oxidation in the presence of ferrous ions follows a parallel reaction mechanism; the resulting overall reaction rate has been found to be of first order with respect to ferrous ion concentration and of three halves with respect to bisulfite concentration. Moreover, the catalytic effect of ferrous ions has been compared with that of manganese ions previously studied, showing that ferrous is a catalyst more active than manganese.

Advanced oxidation processes for decolorization of aqueous solution containing acid red G azo dye

Abstract Some investigations concerning the decolorization of Acid Red G azo dye by photooxidation with hydrogen peroxide were performed. The influences of pH, oxidant concentration, and the presence of Fe2+ or other metal ions (Co2+, Cu2+, Ni2+, Mn2+) as potential catalysts, were investigated. The best results were obtained in the presence of ferrous ions in acid and neutral media. The other ions are not as effective as Fe2+ for dye decolorization. Co2+ and Cu2+ ions have a catalytic action, at low concentration, within a wide range of pH. Ni2+ and Mn2+ ions have no catalytic effect in photooxidation with hydrogen peroxide at acid Ni2+ and Mn2+ ions have no catalytic effect in photooxidation with hydrogen peroxide at acid pH values, but show a weak action in alkaline media.

Fluorescence modulation for the multimolecular communicating ensembles with light and ferric ion: photo-control of the intermolecular photoinduced electron transfer

The fluorescence of pyrene can be quenched by spiropyran (SP) due to the intermolecular photoinduced electron transfer (PET). However, the fluorescence of the ensemble solution of pyrene (PY) and SP restores nearly to the initial value of the pure solution of PY after the consecutive actions of Fe(ClO 4) 3 and UV light. This is owing to the fact that the open form of spiropyan can be coordinated to ferric ion, and as a result the reversible photo-control of the intermolecular PET reaction from SP to the excited PY can be realized under light irradiation in the presence of ferric ion.

Biological activity and ferric ion binding of fragments of glycine-extended gastrin.

Nonamidated gastrins such as progastrin and glycine-extended gastrin17 (Ggly) induce cell proliferation and migration in vitro and colonic mucosal proliferation in vivo. Our earlier NMR study defined the structure of Ggly and showed that ferric ions are essential to its biological activity, with the first binding to Glu7 and the second to Glu8 and Glu9 (Pannequin, J. et al. (2002) J. Biol. Chem. 277, 48602-48609). The aims of this study were to define the minimum biologically active fragment of Ggly and to determine whether ferric ions were also required for its activity. Cell-proliferation studies with Ggly fragments containing the five glutamate residues showed that the nonapeptide LE(5)AYG, the octapeptide LE(5)AY, and the heptapeptides E(5)AY and LE(5)A were fully active and that their activity was dependent on the presence of ferric ions. The activity of the hexapeptides LE(5) and E(5)A and the pentapeptide E(5) was reduced and independent of the presence of iron. The stoichiometry of ferric ion binding to LE(5)AYG, LE(5)AY, and E(5)AY, determined by absorption spectroscopy, was 2 mol/mol. NMR spectroscopy showed that the nonapeptide LE(5)AYG and shorter fragments had no defined structure and that the iron-binding sites differed from those in Ggly. We conclude that, in contrast to amidated gastrins where the C-terminal tetrapeptide is the minimum bioactive fragment, the shortest fully active fragments of Ggly are the heptapeptides LE(5)A and E(5)AY. These observations indicate that extensive proteolytic processing may not completely inactivate Ggly and that bioactive forms that are not detected by current radioimmunoassays may be present in tissues and/or plasma.

Influence of pH and oxidation-reduction potential (Eh) on the dissolution of mercury-containing mine wastes from the Sulphur Bank Mercury Mine

This study was undertaken as a part of the development of treatment alternatives for waste materials, primarily waste rock and roaster tailings, from sites contaminated by mercury (Hg) mining wastes. Leaching profiles of waste rock over a range of pH and oxidation-reduction (Eh) conditions were performed. Because iron (Fe) is present in large quantities in mining wastes, the effect of Fe on the leaching of Hg was also determined. Results show that the Hg concentration increased as the pH of the suspension increased until a pH value of 10.65. Thereafter, the Hg concentration decreased sharply. The Hg concentration in the presence of Fe decreased significantly (1/10th to 1/100th). Kinetics results show a relatively slow rate of leaching in the presence of ferric ions. The results obtained from the present study are being used to predict the fate and stability of Hg present in the environment and will, therefore, be useful in dictating the nature and suitability of any remediation treatment.

Improved wet bonding of methyl methacrylate-tri-n-butylborane resin to dentin etched with ten percent phosphoric acid in the presence of ferric ions.

The objective of this study was to determine the influence of dissolved dentinal substances in demineralized dentin on the hybridization of resin for bonding to dentin. It was hypothesized that these substances, including polyelectrolytes, significantly change the substrates, which could then be assessed by the addition of Na(+), Ca(2+), or Fe(3+) in 10% phosphoric acid. Bovine dentin specimens were etched for 10 s with a solution of 10% phosphoric acid (control) or of 22.0 mM dissolved sodium chloride (10P-Na), calcium chloride (10P-Ca), or ferric chloride (10P-Fe). The specimens were then rinsed, blot-dried, and primed three times with 5% 4-methacryloyloxyethyl trimellitate anhydride in acetone for 60 s. Methyl methacrylate-tri-n-butylborane resin was then applied. The tensile bond strength of each of the dumbbell-shaped specimens was then measured. The fractured surfaces and modified cross-sections were examined by scanning electron microscopy. The cross-sections were soaked in 6N HCl for 10 s and then in 1% sodium hypochlorite for 30 min to determine the resin content in the hybridized specimens. Shrinkage of the demineralized dentins upon drying was assessed by atomic force microscopy. The tensile bond strengths were 10.8 +/- 4.5 (control), 15.0 +/- 7.0 (10P-Na), 19.3 +/- 5.5 (10P-Ca), and 27.8 +/- 8.1 (10P-Fe) MPa. The atomic force microscopy studies showed that Fe(3+) minimized the shrinkage by drying for 10 s but Ca(2+) and Na(+) did not decrease the shrinkage the same as the control. The results support the hypothesis that the monomer permeability of wet demineralized dentin is effectively improved by dissolving ferric ions in the phosphoric acid, resulting in a greater bond strength and higher resin content in the hybridized dentin. The dissolved dentinal substances, including the polyelectrolytes, had a significant influence on the characteristics of the demineralized dentin, changing the degree of hybridization and bonding.

Spectrophotometric determination of ornidazole

Three simple, sensitive, selective and economical methods (method A, B and C) for the determination of ornidazole have been described. Method A, B and C are based on the formation of yellow, blood red and blue coloured chromogens when reduced ornidazole in situ reacted with vanillin, 1,10-phenanthroline in presence of ferric ions and Folin-Ciocalteau (FC) reagents exhibiting λ m a x at 426, 508.8 and 648 nm, respectively, which obeyed Beer's law in the concentration range of 5-25, 2-10 and 5-25 μg/ml respectively. The results of analysis for the three methods have been validated statistically and by recovery studies. The results are comparable with those obtained with UV spectrophotometric method in alcohol at 312.8 nm.

Photocontrolled Electron Transfer Reaction between a New Dyad, Tetrathiafulvalene−Photochromic Spiropyran, and Ferric Ion

Photocontrolled electron transfer reaction is important not only for understanding the complicated biological processes such as photosynthesis and respiration but also for the design and studies of molecular electronics. This paper presents the synthesis and spectral and electrochemical studies of a new dyad 1 containing an electroactive unit (tetrathiafulvalene, TTF) and a photochromic unit (spiropyran, SP). Spectral studies showed that the redox states of the TTF unit of dyad 1 in the presence of ferric ions were dependent on the photoswitching process of the spiropyran unit upon UV light irradiation. Electrochemical investigations indicated that the oxidation potential of ferrous ion was largely reduced after coordination with MC (the open form of SP). As a result, the electron-transfer reaction from MC·Fe2+ to TTF+•, which act as electron donor and acceptor, respectively, is thermodynamically favorable. Therefore, the electron-transfer reaction between the TTF unit and ferric ion can be photocontrolled in the presence of the SP unit. The present result shows the possibility to design new electron donor−acceptor supramolecules containing spiropyran units to photoregulate the electron-transfer reaction.

Optical and EPR studies of iron bearing phosphate minerals: satterlyite and gormanite from Yukon Territory, Canada

The iron phosphate minerals satterlyite and gormanite have been investigated by EPR and optical absorption studies. The optical results indicate the presence of ferrous and ferric ions in both minerals. In gormanite the site symmetry of Fe(III) is near octahedral whereas in satterlyite it is tetragonally distorted. On the other hand, the Fe(II) ions are in tetragonally distorted octahedral site in both minerals. In satterlyite the EPR results indicate the presence of the ferric ion in a tetragonally distorted state together with a small percentage of Mn(II). Crystal field (Dq) and interelectronic parameters (B and C) are evaluated.

Dissolution of magnetite using an environmentally friendly chelant: an electrochemical impedance spectroscopy study

Ethylenediaminedisuccinic acid (EDDS), a biodegradable substitute for EDTA, was used as a chelant for dissolving magnetite and magnetite formed on iron metal surface. Dissolution was found to increase in presence of ferrous ions and depend on pH of solution, concentration of ferrous ion, EDDS concentration, applied cathodic potential and temperature. The impedance spectrum for the dissolution of magnetite film formed on iron exhibited two time constants. The first at high frequency range is ascribed to the reductive dissolution of magnetite. It is very crucial to carry out the dissolution process at the appropriate temperature to insure complete removal of oxide layer.

Bench scale evaluation of a chemo-biochemical process for desulphurization of gaseous streams containing hydrogen sulphide

A Chemo-biochemical process for desulphurization of a gaseous stream containing hydrogen sulphide (H2S) with concomitant recovery of elemental sulphur was investigated on bench scale. The process operates in two stages. In the first stage, H2S present in a gas stream is oxidized to elemental sulphur by ferric sulphate. In the second stage, ferrous sulphate produced in the process, after separation of sulphur, is biologically oxidized using the microbial culture of Thiobacillusferrooxidans isolated from the sediment of a river flowing through a coal bed containing high pyritic sulphur. Hydrogen sulphide in the gas stream was oxidized in a packed bed reactor containing Raschig rings of uniform size. The gaseous stream containing a mixture of nitrogen and H2S (7.31% v/v) could be oxidized effectively in the presence of ferric ion. The bench scale unit, operated in a continuous mode, indicated that an optimal load of 0.1755 kmol m-3 d-1 of H2S and 0.386 kmol m-3 d-1 of ferric ion are required to be maintained in order to achieve the H2S removal efficiency of more than 99%.The ferrous sulphate produced in the process could be biologically oxidized to ferric sulphate using Thiobacillus ferrooxidans immobilized ona rotating biological rope contactor (RBRC). A ferrous ion load of 0.01 kmolm-3 d-1, considering the recirculation, could be converted intoferric ions with an efficiency of 99.12% at a hydraulic retention time(HRT) of 0.15 day.

Arsenic removal from drinking water by flocculation and microfiltration

Arsenic removal from drinking water is a major problem in many parts of the world. We have investigated arsenic removal by flocculation and microfiltration. Ferric chloride and ferric sulphate have been used as flocculants. The use of small amounts of cationic polymeric flocculants, as flocculation aids in the presence of ferric ions, has also been investigated. The results obtained here show that flocculation prior to microfiltration leads to significant arsenic removal in the permeate. Further, the addition of small amounts of cationic polymeric flocculants lead to significantly improved permeate fluxes during microfiltration. The residual turbidity, after flocculation and microfiltration, may be used as a guide to the level of arsenic removal. Since energy requirements for microfiltration are low and fluxes high, compared to other membrane processes such as reverse osmosis and nanofiltration, flocculation and microfiltration may be a cost effective method for arsenic removal from drinking water.

Optimal conditions for bio-oxidation of ferrous ions to ferric ions using Thiobacillus ferrooxidans.

A chemo-biochemical process using Thiobacillus ferrooxidans for desulphurization of gaseous fuels and emissions containing hydrogen sulphide (H2S) has been developed. In the first stage, H2S present in fuel gas and emissions is selectively oxidized to elemental sulphur using ferric sulphate. The ferrous sulphate produced in the first stage of the process is oxidized to ferric sulphate using Thiobacillus ferrooxidans for recycle and reuse in the process. The effects of process variables, temperature, pH, total dissolved solids (TDS), elemental sulphur, ferric and magnesium ions on bio-oxidation of ferrous ions to ferric ions were investigated using flask culture experiments. The bio-oxidation of ferrous ions to ferric ions could be achieved efficiently in the temperature range of 20(+/-1)-44(+/-1) degrees C. A pH range of 1.8(+/-0.02)-2.2(+/-0.02) was optimum for the growth of culture and effective bio-oxidation of ferrous ions to ferric ions. The effect of TDS on bio-oxidation of ferrous ions indicated that a preacclimatized culture in a growth medium containing high dissolved solid was required to achieve effective bio-oxidation of ferrous ions. Elemental sulphur ranging from 1000 to 100,000 mg/l did not have any effect on efficiency of ferrous ion oxidation. The efficiency of bio-oxidation of ferrous ions to ferric ions was not affected in the presence of ferric ions up to a concentration of 500 mg/l while 3 mg/l of magnesium ion was optimal for achieving effective bio-oxidation.

Photocatalytic oxidation of arsenite in TiO2 suspension: kinetics and mechanisms.

Arsenite [As(III)] and arsenate [As(V)] are highly toxic aquatic contaminants. Since arsenite is more mobile in natural waters and less efficiently removed in adsorption/coagulation processes than arsenate, the oxidation of arsenite to arsenate is desirable in water treatment. We performed the photocatalytic oxidation of arsenite in aqueous TiO2 suspension and investigated the effects of pH, dissolved oxygen, humic acid (HA), and ferric ions on the kinetics and mechanisms of arsenite oxidation. Arsenite oxidation in UV-illuminated TiO2 suspension was highly efficient in the presence of dissolved oxygen. Homogeneous photooxidation of arsenite in the absence of TiO2 was negligibly slow. Since the addition of excess tert-butyl alcohol (OH radical scavenger) did not reduce the rate of arsenite oxidation, the OH radicals should not be responsible for As(III) oxidation. The addition of HA increased both arsenite oxidation and H2O2 production at pH 3 under illumination, which could be ascribed to the enhanced superoxide generation through sensitization. We propose that the superoxide is the main oxidant of arsenite in the TiO2/UV process. The addition of ferric ions also significantly enhanced the arsenite photooxidation. In this case, the addition of tert-butyl alcohol reduced the arsenite oxidation rate, which implied thatthe OH radical-mediated oxidation path was operative in the presence of ferric ions. Since both Fe3+ and HA that were often found with the arsenic in groundwater were beneficial to the photocatalytic oxidation of arsenite, the TiO2/UV process could be a viable pretreatment method. This can be as simple as exposing the arsenic-polluted water in a TiO2-coated trough to sunlight.