Formation Of Ferric Ions Research Articles

Solar-driven, self-sustainable electrolysis for treating eutrophic river water: Intensified nutrient removal and reshaped microbial communities

River ecosystems are the most important resource of surface freshwater, but they have frequently been contaminated by excessive nutrient input of nitrogen (N) and phosphorus (P) in particular. An efficient and economic river water treatment technology that possesses the capacity of simultaneous N and P removal is urgently required. In this study, a solar-driven, self-sustainable electrolytic treatment was conducted in situ to intensify N and P removal from eutrophic river water. Solar panel was applied to provide the electrolysis setups with energy (voltage 10 ± 0.5 V), and the current density was controlled to be 0.06 ± 0.02 mA cm−2. Results indicated that the average removal efficiencies of total N (TN) and total P (TP) under electrolysis conditions reached 72.4 ± 11.7 and 13.8 ± 5.3 mg m−2 d−1, which were 3.7- and 4.7-fold higher compared to untreated conditions. Enhanced TN removal mainly reflected the abatement of nitrate N (NO3−-N) (80.6 ± 4.1%). The formation of ferric ions through the electro-dissolution of the sacrificial iron anode improved TP removal by coprecipitation with SPS. Combined high-throughput sequencing and statistical analyses revealed that electrolysis significantly reshaped the microbial communities in both the sediment-water interface and suspended sediment (SPS), and hydrogenotrophic denitrifiers (e.g., Hydrogenophaga) were highly enriched under electrolysis conditions. These findings indicated that in situ electrolysis is a feasible and effective technology for intensified nutrient removal from river water.

A novel method for synthesis of polyaniline and its application for catalytic degradation of atrazine in a Fenton-like system

Recently, polyaniline (PANI) has received widespread attention for the free volume, optical transmittance and electrical conductivity. In this study, a chemical vapor deposition method was developed to synthesize the conductive PANI-clay composite catalyzed by Fe(III)-saturated attapulgite (Fe(III)-ATTP). The reaction is initiated by the electron transfer from aniline (ANI) to Fe(III), subsequently generating ANI radical cation. The radical could further polymerize and form PANI in the constrained micropore structure of ATTP. The Raman, Fourier transform infrared and X-ray photoelectron spectra confirmed the formation of PANI on Fe(III)-ATTP surface by comparison with the PANI standard. The newly synthesized Fe(III)-ATTP-PANI composite exhibited superior reactivity as indicated by the efficient dissipation of atrazine in the presence of hydrogen peroxide (H2O2), and the degradation rate increased up to almost 150 times compared to Fe(III)-ATTP. The higher reactivity of Fe(III)-ATTP-PANI/H2O2 system was attributed to the accelerated electron transfer, the formation of ferrous ions, and the enhanced adsorption of atrazine onto attapulgite. Furthermore, our experimental results demonstrated that Fe(III)-ATTP-PANI showed good stability and it could be reused for several reaction cycles with high reactivity. This new material could act as an environmental-friendly catalyst in Fenton-like reaction system and show promising potential to effectively eliminate many persistent organic contaminants.

A New Colorimetric Sensor for Cysteine Determination Based on Dual Reacting‐mediated Strategy

Rapid and simple determination of cysteine is a key requirement for both diagnosis and treatment of diseases. A novel concept is proposed for combining dual reacting‐mediated process into the construction of a simple yet effective colorimetric strategy for cysteine detecting, which is based on the analyte‐induced formation of ferrous ion and graphene oxide‐supported ionic recognition through selective coordination process between phenanthroline molecule and ferrous ion. In colorimetric analysis, the simple principle of ferrous ion that cysteine‐induced can be recognized by phenanthroline indicator due to their good binding affinity and therefore provided a sensitive optical readout for conveniently detecting cysteine. Proof‐concept experiments demonstrate that the proposed colorimetric system shows rapid response toward cysteine determination as well as with a satisfying detection limit of 4.8 μM only by using simple UV–Vis spectroscopy and 15 μM with the naked eye.

Studying Equilibrium in the Chemical Reaction between Ferric and Iodide Ions in Solution Using a Simple and Inexpensive Approach

A laboratory experiment on the study of the chemical equilibrium based on the reaction between ferric and iodide ions in solution with the formation of ferrous ions, free iodine, and triiodide ions is developed. The total concentration of iodide and triiodide ions in the reaction mixture during the reaction is determined by the argentometric titration; the concentrations of the other reagents and products are calculated using the material balance equations. The dependence of the equilibrium constant on temperature is also considered. The average values of Kc are 2.5 × 104 M–1 (35 °C) and 4.5 × 104 M–1 (45 °C). The experiment uses common reagents and simple equipment and can be performed in any educational laboratory. The basic procedure of processing the experimental data is quite simple and can be easily performed even by first-year students; however, the experiment can be extended in several ways to be suitable for advanced laboratory courses for upper-year undergraduates. Possible extensions are discus...

Utilization of co-existing iron in arsenic removal from groundwater by oxidation-coagulation at optimized pH

Oxidation-coagulation at optimized pH (OCOP) using NaHCO3, KMnO4 and FeCl3 is an efficient and low-cost arsenic removal method for domestic to large community scale applications. In this method, a high dose of the oxidant is used when the groundwater contains high concentration of coexisting iron for oxidising all ferrous and arsenate ions. A fixed dose of 25mg/L of FeCl3 is also employed as coagulant despite the formation of ferric ions from the coexisting ferrous ions. The present study aimed at utilization of the coexisting iron for the coagulation purpose and reducing the coagulant dose. Response Surface Methodology was employed to optimize the doses of the oxidant and the pH conditioner. A field trial at various arsenic affected rural habitations has shown that the present modified OCOP method to be more efficient and economical than the OCOP method reducing both arsenic and coexisting iron concentrations to less than 2μg/L and 0.1mg/L, respectively, at a lower cost. The modified OCOP method is useful especially with high concentration of coexisting iron.

The role of iron anode oxidation on transformation of chromium by electrolysis

The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in a separated electrode system. Oxidation of iron electrodes produces ferrous ions, causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron–chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5mAL−1 in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe15Cr5(OH)60 precipitate.

The importance of reductive mechanisms for intestinal uptake of iron from ferric maltol and ferric nitrilotriacetic acid (NTA)

Intestinal iron absorption is thought to proceed with iron mainly in the ferrous form, yet the novel iron complex, ferric maltol is an effective oral preparation. Although possessing a high oil: water partition coefficient, ferric maltol does not diffuse across the intestine but donates its iron to the endogenous uptake system. Reduction of the ferric iron in the gut lumen appears to precede iron uptake both from ferric maltol and from ferric nitrilotriacetic acid (NTA) which is a non-penetrating iron ligand. Uptake of radiolabelled iron (59Fe) into isolated fragments of rat small intestine was inhibited by the ferrous chelator, bathophenanthroline sulphonate (BPS) and enhanced at low concentrations by the reducing agent ascorbic acid. Spectrophotometric evidence was obtained that ferrous ions are generated from these ferric complexes in the presence of ascorbic acid and other reducing agents. The rate of ferrous ion formation was independent of ferric maltol concentration at low ascorbic acid levels and decreased with increasing ferric maltol concentration at higher levels of ascorbate. Maltol has a high affinity for ferric ions and may delay reduction at higher concentrations. By contrast, a higher rate of ferrous ion generation was seen with ferric NTA and this increased with iron ligand concentration. Washings from the intestinal lumen also brought about ferrous ion formation from these ferric ligands. Gel filtration revealed these reducing factors to be of low molecular weight. The washings, however, interfered with 59Fe uptake into the isolated fragments, but when reducing fractions only from the filtered washings were used, enhanced iron uptake was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization by electrochemical impedance spectroscopy of magnetite nanoparticles supported on carbon paste electrode

Magnetite nanoparticles were supported on carbon paste electrode and characterized by low scan rate voltammetry and electrochemical impedance spectroscopy (EIS) to obtain mechanistic information related to its oxidation and reduction in acid media. The voltammograms showed only one reduction and one oxidation peak for the supported magnetite, which were attributed to formation of ferrous ion and ferric oxide, respectively. Both peaks are fairly wide, indicating complex mechanisms. Using EIS, a mechanism showing up to three time constants, capacitive all of them, was evidenced, both in anodic and cathodic domain. These were attributed to charge transfer at the highest frequencies, adsorption of generated species at intermediate frequencies, and proton adsorption at low frequencies. Discussion about the nature of the adsorbed species and the concerned mechanism for each domain is developed.

Observation of Transient Iron(II) Formation in Dye-Sensitized Iron Oxide Nanoparticles by Time-Resolved X-ray Spectroscopy

The reduction of ferric iron in solid phase minerals leads to the mobilization of ferrous iron in the environment and is thus a crucial component of the global iron cycle. Despite the importance of this process, a mechanistic understanding of the structural and chemical changes that are caused by this electron transfer reaction is not established because the speed of the fundamental chemical steps renders them inaccessible to conventional study. Ultrafast time-resolved X-ray spectroscopy is a technique that can overcome this limitation and measure changes in oxidation state and structure occurring during chemical reactions that can be initiated by a fast laser pulse. We use this approach with ∼100 ps resolution to monitor the speciation of Fe atoms in iron oxide nanoparticles following photoinduced electron transfer from a surface-bound photoactive dye molecule. These data represent the first direct real-time observation of the dynamics of ferrous ion formation and subsequent reoxidation in iron oxide.

Effect of Gamma Irradiation on the Structure Diffusion Coefficient of Co-Zn Doped Ferrite

A series of the ferrite system Co0.6Zn0.4MnxFe2-xO4 with (x = 0.7, 0.8, 0.9 and 1) were prepared by general ceramic method. The X-ray diffraction patterns confirmed the formation of the cubic single phase structure. The lattice parameter and the crystal size increased after irradiation which was attributed to the formation of ferrous ions of larger radius than that of ferrous ions in unirradiated samples. A small shift was observed in the diffraction peak position. This indicated the slight distortion of the cubic structure. The diffusion coefficient of electrons was found to be increased for the irradiated samples. The concentration of electrons was estimated and was found to be increased after ?-irradiation.

Effect of gamma irradiation on the structural properties and diffusion coefficient in Co–Zn ferrite

A series of samples of Co 1− x Zn x Fe 2O 4 were prepared by the usual ceramic technique where x=0.3,0.5,0.6, and 0.8. The samples were irradiated by Co 60 gamma source with a high dose equal to 10 6 rad/h. The diffusion coefficient of oxygen vacancies was estimated from DC conductivity measurements. It was noticed that the diffusion coefficient increased after gamma irradiation for all Zn 2+ concentrations. This could be explained on the basis of displacement of metal ions from its original sites under the effect of irradiation leaving behind it lattice vacancies which increase the diffusion coefficient. The concentration of lattice vacancies increased, whereas the activation energy of diffusion process decreased after irradiation. The lattice parameter of the studied samples increased due to the formation of ferrous ions under the ionizing effect of gamma radiation. These changes in some physical properties of the studied samples are useful for the detection of nuclear contamination of environmental atmosphere.

Role of hydrogen peroxide and hydroxyl radical in producing the residual effect of ultraviolet radiation.

Residual effect of UV radiation on Microcystis aeruginosa and Escherichia coli K12 A/lambda (F+) was studied under various conditions to examine if the formation of hydrogen peroxide (H2O2) and hydroxyl radical (OH.) can explain the residual biocidal action of UV radiation. Survival of test organisms, that is, M. aeruginosa and E. coli K12 A/lambda (F+), in UV-irradiated synthetic water was monitored to assess the residual effect after the UV radiation. Synthetic water with various compositions was used to understand the role of transition metals and photosensitizing organic molecules in producing the residual biocidal action. Ultraviolet-irradiated synthetic water containing a photosensitizing element and ferric ion (Fe3+) showed residual biocidal effect for more than 7 days. No residual effect was observed in the absence of any photosensitizing element. A close relationship was observed between the residual effect and the formation of hydrogen peroxide in the UV-irradiated water. Scavenging of hydrogen peroxide and hydroxyl radical from the UV-irradiated water significantly reduced the residual biocidal action. Ultraviolet-irradiation of synthetic water containing ferric ion was found to promote the formation of ferrous ion (Fe2+). Because ferrous ion can produce reactive species in the presence of hydrogen peroxide, transition metals and hydrogen peroxide are believed to play a key role in producing the residual effect of UV radiation through the formation of reactive species, for example, hydroxyl radical.

Influence of the measurement frequency on the magnetic disaccommodation spectra of YIG samples

Abstract Magnetic aftereffect phenomena in yttrium iron garnets and their relationship to the dynamics of domain walls are analyzed by means of the magnetic disaccommodation (DA) technique. The samples have been prepared using a standard ceramic technique in CO 2 atmosphere in order to enhance the formation of ferrous ions in the lattice. The results reveal the presence of the well-known process II around 130 K and a process at higher temperatures (187 K). Furthermore, accommodation (or negative DA) processes have been detected at temperatures just below process II. The features of these phenomena are strongly related to the measurement frequency and, hence, they are more noticeable as this frequency is increased. Such behavior is associated with the resonance of the domain wall motion at frequencies around the measurement frequency. The characteristic parameters that define this resonance depends upon time due to the presence of an induced anisotropy relaxation process that occurs after demagnetization.

Degradation of the dye X-3B by UV/Fe(III)-generated hydroxyl radicals in aqueous solution

Bleaching of the dye, Reactive Brilliant Red X-3B, by irradiation with light at λ≥320nm in an air-saturated aqueous solution of Fe(III) species was investigated under various conditions. It was observed that the dye, quite stable to the UV light, could be degraded efficiently when it was irradiated in the ferric solution. The initial rate degradation was almost independent of the initial [X-3B], but was greatly influenced by the initial [Fe(III)], pH, light intensity, and the anions of chloride or sulfate added to the solution. A further analysis showed that the degradation began with a simultaneous formation of ferrous ions. When all the ferric ions were transferred into Fe(II), the dye disappearance terminated no matter how much of the dye was left in the solution. The molar ratio of the Fe(II) formed to the X-3B disappeared was evaluated to be over 3, depending on the yield of the dye degradation. The result suggests that the process is initiated by the photolysis of Fe(III)-hydroxy species, from which the hydroxyl radicals are generated to oxidize the dye substrate subsequently.

Electrogenerative formation of ferric ions in a sulfur dioxide-sulfuric acid solution; Graphite catalysed sulfur dioxide oxidation

The electrogenerative oxidation of ferrous ions in 3m sulfuric acid, containing sulfur dioxide and subsequent sulfur dioxide oxidation, were studied in connection with potential regenerable sulfur dioxide remediation processes. The presence of sulfur dioxide in the feed stream did not affect cell performance. Oxidation of sulfur dioxide in the electrogenerative reactor took place when high ferrous to ferric ion conversions were obtained. Low cost graphite and iron ions served as an effective mediating system for promoting electron transfer to sulfur dioxide in strong acid solutions. In contrast, the homogenous reaction between iron(iii) and sulfur dioxide is relatively slow. In a separate batch reactor, the heterogeneous iron(iii) and sulfur dioxide reaction was found to be graphite catalysed, accounting for sulfur dioxide conversion observed in the electrogenerative reactor. Ferrous ion presence should be minimized, because it inhibits the desired catalysed reaction.

Preparation and Transport Properties of Composite Membranes Composed of Cation Exchange Membranes and Polypyrrole

Composite membranes composed of cation exchange membranes and polypyrrole, in which polypyrrole existed on one surface of the membrane as a thin layer, were prepared with ferric ion form cation exchange membranes and an aqueous pyrrole solution. After confirming the existence of the polypyrrole layer on the membrane surface (EPMA, conductivity, and micrograph), the following electrodialytic transport properties of the membrane were evaluated: the electrical resistance of the membrane, the relative transport number between the alkali earth metal cations and sodium ions, the current efficiency, and voltage drop at the membrane. The permeation of calcium ions was markedly decreased by the formation of a polypyrrole layer on the cation exchange membranes in both cases where the layer faced the anode and the cathode compartments. It was confirmed by a decrease in the current efficiency during electrodialysis in the layer facing the cathode compartment that the polypyrrole layer has a cationic charge. The permeability coefficient of the neutral molecules through the membrane was markedly decreased by the formation of a layer on the cation exchange membrane. From these results, a decrease in the permeation of the alkali earth metal cations versus sodium ions was observed based on the synergistic effect of the sieving of divalent cations by a tight and rigid polypyrrole layer and the difference in the electrostatic repulsion force between the divalent cations and the sodium ions.

Ferrous ion formation by ferrioxamine prepared from aged desferrioxamine: A potential prooxidant property

The siderophore desferrioxamine (DEFOM) binds ferric ions in a 1:1 ratio resulting in a ferrioxamine (FOM) complex. When DEFOM is stored or heat degraded, the resulting FOMD undergoes an autoreduction with the transfer of electrons to the bound ferric ions forming ferrous ions, which react with Ferrozine to yield a pink-coloured complex absorbing at 562 nm. Heat-aged DEFOM forms a FOND complex with an absorption maxima changing from 432 nm to 441 nm. When the autoreduced FOMD complex is placed in a phosphate buffer at pH 7.4, ferrous ions autoxidase transferring electrons to molecular oxygen to form superoxide and hydrogen peroxide. Fenton chemistry leading to the formation of hydroxyl radicals can then occur. Studies with a variety of reactive oxygen scavengers support a role for the hydroxyl radical in damage to the detector molecule deoxyribose. However, when EDTA is present, damage to deoxyribose is decreased and the radicals causing deoxyribose degradation no longer appear to be characteristic of the hydroxyl radical.

Kinetics of ferric ion promoted photodecomposition of 2-chlorophenol

The photodecomposition of 2-chlorophenol in ferric solutions at pH:3.0 was investigated using monochromatic light(313 nm). The concentrations of 2-chlorophenol were in the range of 5.0×10 −6 to 1.5×10 −4 mol·l −1. Above 5.0×10 −5 mol·l −1 of 2-chlorophenol concentration, it decreased linearly with irradiation time and the rates of photodecomposition were independent of the initial concentrations. Below 3.0×10 −5 mol·l −1 of 2-chlorophenol concentration, the initial rates of photodecomposition decreased with lowering the initial concentration of 2-chlorophenol. The results were in good agreement with the kinetic model that assumed the steady-state concentration of hydroxyl radical formed by photo-dissociation of Fe(III)-hydroxy complex. The rates of ferrous ion formation in the presence of 2-chlorophenol were larger than that in the absence of 2-chlorophenol.

Properties of composite membranes prepared from ion exchange membranes and conducting polymers. II. Electrical potential generation from cell composed of a cation exchange membrane-polypyrrole composite membrane and a ferric ion form cation exchange membrane

When a ferric ion form cation exchange membrane was immersed in an aqueous pyrrole solution, polypyrrole was formed on the membrane surfaces and ferric ions in the membrane were reduced to ferrous ions. Polypyrrole layers penetrated into the membrane matrix with increasing immersion period in the pyrrole solution. An electrical potential was observed by clamping the obtained composite membrane and the ferric ion form cation exchange membrane between two platinum plates and immersing the assembly into pure water. The potential was measured in relation to polymerization period. Before homogeneous distribution of polypyrrole in the membrane (4 hr), which was confirmed by conductivity measurement, an initial potential in discharge decreased and durability of the potential increased with increasing polymerization period. Beyond 4 hr of polymerization in the synthesis of the composite membrane, the initial potential on discharge attained almost a constant value and its durability decreased with increasing polymerization period in spite of increase in electron conductivity and the amount of ferrous ions in the composite membrane. It is thought that migration of ferrous ions in the composite membrane would be restricted because of a development of a tight and rigid polypyrrole structure in the cation exchange membrane.

Properties of ion exchange membranes combined with conducting polymers anisotropically—I. emf generation by redox reactions across composite membrane

In order to produce a new functional material composed of a cation exchange membrane and conducting polymers, pyrrole or aniline was polymerized in the cation exchange membrane phase anisotropically by chemical polymerization. When one side of the cation exchange membrane of ferric ion form was contacted with an aqueous pyrrole solution for a suitable period, a bilayer membrane, composed of a cation exchange membrane layer and a polypyrrole-impregnated-cation exchange membrane layer, was obtained. This is because a thin and tight layer is formed on the membrane surface which pyrrole molecules cannot permeate easily. This bilayer membrane produced emf which was dependent on relative humidity when the composite membrane was held tightly between two platinum plates. The observed maximum emf was 217 mV with a 2 Mω load. Analysis of ferric and ferrous ions in a polypyrrole-impregnated-cation exchange membrane showed that the membrane contained ferrous ions more than 98% to total iron ions. Thus, the emf of the composite membrane results from Fe2+-Fe3+ redox cell.