Showing papers on "Ferric published in 1996"
TL;DR: In this article, a comparison of coagulation and adsorption experiments and of experimental results with predictions based on surface complexation modeling was made, and it was shown that adsorization is an important (though not the sole) mechanism governing arsenic removal during coagulations.
Abstract: Bench-scale studies were conducted in model freshwater systems to investigate how various parameters affected arsenic removal during coagulation with ferric chloride and arsenic adsorption onto preformed hydrous ferric oxide. Parameters included arsenic oxidation state and initial concentration, coagulant dosage or adsorbent concentration, pH, and the presence of co-occurring inorganic solutes. Comparison of coagulation and adsorption experiments and of experimental results with predictions based on surface complexation modeling demonstrated that adsorption is an important (though not the sole) mechanism governing arsenic removal during coagulation. Under comparable conditions, better removal was observed with arsenic(V) [As(V)] than with arsenic(III) [As(III)] in both coagulation and adsorption experiments. Below neutral pH values, As(III) removal-adsorption was significantly decreased in the presence of sulfate, whereas only a slight decrease in As(V) removal-adsorption was observed. At high pH, removal-adsorption of As(V) was increased in the presence of calcium. Removal of As(V) during coagulation with ferric chloride is both more efficient and less sensitive than that of As(III) to variations in source water composition.
395 citations
TL;DR: In this article, the effects of metal coagulant concentration, effluent dilution and pH on the removal of total carbon, colour and turbidity from a combined bleached chemithermomechanical/thermOMEchanical (BCTMP/TMP) effluent were examined.
295 citations
TL;DR: Marschner et al. as discussed by the authors used a mathematical model to assess whether organic acid-mediated Fe dissolution could play a significant role in elevating the concentration of Fe-complexes in the rhizosphere, and further, whether this could satisfy the Fe demands of a plant utilizing ferric reduction to acquire Fe.
Abstract: Both experimental extractions and theoretical calculations were undertaken to assess whether organic acid-mediated Fe dissolution could play a significant role in elevating the concentration of Fe-complexes in the rhizosphere, and further, whether this could satisfy the Fe demands of a plant utilizing ferric reduction to acquire Fe. Using a mathematical computer model, it was predicted that organic acids released from and diffusing away from the root would result in a solution organic acid concentration at the root surface of between 1 to 50 μM. Over 99% of the organic acids lost by the root were predicted to remain within 1 mm of the root surface. The experimental results indicated that citrate-mediated Fe dissolution of amorphous Fe(OH)3, was rapid in comparison with citrate dissolution of the Fe-oxides, Fe2O3 and Fe3O4. The rate of citrate and malate mediated Fe-dissolution was dependent on many factors such as pH, metal cations and phosphate saturation of the Fe(OH)3 surface. At pH values ≤6.8, citrate formed stable complexes with Fe and dissolution proceeded rapidly. Under optimal growth conditions for a plant utilizing a reductive-bound mechanism of Fe acquisition (dicots and non-grass monocots), it can be expected that citrate and malate may be able to satisfy a significant proportion of the plant's Fe demand through the formation of plant-available organic-Fe3+ complexes in the rhizosphere. In high pH soils (pH≥7.0), the plant must rely on other sources of Fe, as citrate-mediated Fe dissolution is slow and Fe-citrate complexes are unstable. Alternatively, the root acidification of the rhizosphere could allow the formation of stable Fe-organic complexes. ei]H Marschner
287 citations
TL;DR: Experimental studies demonstrate that structural Fe(II) in magnetite and ilmenite heterogeneously reduce aqueous ferric, cupric, vanadate, and chromate ions at the oxide surfaces over a pH range of 1-7 at 25°C.
256 citations
TL;DR: In this article, a model for the purple form of the DOPA-containing Mytilus edulis adhesive protein (Mefp1) involving bis(catecholato) coordination of ferric ions with most of the iron(III) complexed as EPR-silent μ-oxo- or μ-hydroxo-bridged binuclear clusters is suggested.
Abstract: Iron(III) binding to the DOPA-containing Mytilus edulis adhesive protein (Mefp1) has been studied by spectrophotometric titrations, electron paramagnetic resonance (EPR), and resonance Raman spectroscopies. At pH 7.0, two different forms of the iron−protein complex exist: one purple (λmax = 548 nm) and one pink (λmax = 500 nm). The pink form is favored at high DOPA:Fe ratios and the purple at low DOPA:Fe ratios. Resonance Raman spectroscopy of both forms demonstrates that the chromophores are ferric catecholate complexes. EPR spectra of both forms of the protein measured at the same iron concentration reveal a g ≈ 4.3 resonance of approximately 4 times the intensity in the spectrum of the pink complex compared with that of the purple form. On the basis of the collective evidence obtained here, a model for the purple form of the ferric Mefp1 involving bis(catecholato) coordination of ferric ions with most of the iron(III) complexed as EPR-silent μ-oxo- or μ-hydroxo-bridged binuclear clusters is suggested....
237 citations
TL;DR: The spectrophotometric method, as revised by us, provides an easy, rapid, sensitive, and complete measure of hydroperoxidation of lipids.
237 citations
TL;DR: The observed pseudo-first order rate constant for the reaction between a horseradish peroxidase (HRP) variant (R38L)HRPC and hydrogen peroxide saturates at high peroxide concentrations is consistent with a two-step mechanism involving the formation of an HRP-HO intermediate, and Spectrophotometric titrations show that arginine 38 modulates the reactivity of HRP compound I.
183 citations
TL;DR: In this article, the water-gas shift reaction (WGSR) was studied on Auα-Fe2O3 catalyst and the results obtained can be explained on the basis of the associative mechanism of the WGSR.
Abstract: The water-gas shift reaction (WGSR) has been studied on Auα-Fe2O3 catalyst. The structure of the samples has been investigated by chemical and physical methods—TEM, X-ray, DTA, FTIR. A high dispersion degree of the gold particles and an increased concentration of the hydroxyl groups on Auα-Fe2O3 has been established in comparison to the pure α-Fe2O3. The results obtained can be explained on the basis of the associative mechanism of the WGSR. The essential aspects are the dissociative adsorption of water on ultrafine gold particles, followed by spillover of active hydroxyl groups onto adjacent sites of the ferric oxide. The formation and decomposition of intermediate species is accompanied by redox transfer Fe3+ Fe2+ in Fe3O4.
181 citations
TL;DR: In this article, a new preparation of sulphate containing green rust, GR2(SO4−−), is shown to reach its chemical formula at stoichiometry, which consists of mixing FeCl2 · 4H2O and NaOH to precipitate Fe(OH)2 before adding immediately Na2SO4.
160 citations
TL;DR: It is postulate that reduced siderophore-mediated iron uptake, especially that by pyoverdin, may be one possible mechanism contributing to such effect and SOD and catalase activities in P. aeruginosa are affected.
Abstract: Pseudomonas aeruginosa is considered a strict aerobe that possesses several enzymes important in the disposal of toxic oxygen reduction products including iron- and manganese-cofactored superoxide dismutase and catalase. At present, the nature of the regulation of these enzymes in P. aeruginosa Is not understood. To address these issues, we used two mutants called A4 and C6 which express altered Fur (named for ferric uptake regulation) proteins and constitutively produce the siderophores pyochelin and pyoverdin. Both mutants required a significant lag phase prior to log-phase aerobic growth, but this lag was not as apparent when the organisms were grown under microaerobic conditions. The addition of iron salts to mutant A4 and, to a greater extent, C6 cultures allowed for an increased growth rate under both conditions relative to that of bacteria without added iron. Increased manganese superoxide dismutase (Mn-SOD) and decreased catalase activities were also apparent in the mutants, although the second catalase, KatB, was detected in cell extracts of each fur mutant. Iron deprivation by the addition of the iron chelator 2,2'-dipyridyl to wild-type bacteria produced an increase in Mn-SOD activity and a decrease in total catalase activity, similar to the fur mutant phenotype. Purified wild-type Fur bound more avidly than mutant Fur to a PCR product containing two palindromic 19-bp "iron box" regions controlling expression of an operon containing the sodA gene that encodes Mn-SOD. All mutants were defective in both ferripyochelin- and ferripyoverdin-mediated iron uptake. Two mutants of strain PAO1, defective in pyoverdin but not pyochelin biosynthesis, produced increased Mn-SOD activity. Sensitivity to both the redox-cycling agent paraquat and hydrogen peroxide was greater in each mutant than in the wild-type strain. In summary, the results indicate that mutations in the P. aeruginosa fur locus affect aerobic growth and SOD and catalase activities in P. aeruginosa. We postulate that reduced siderophore-mediated iron uptake, especially that by pyoverdin, may be one possible mechanism contributing to such effect.
154 citations
TL;DR: In this paper, the authors present direct in situ X-ray absorption fine structure (XAFS) evidence for the presence of hexavalent chromium(III) at the surface of synthetic magnetite at near neutral pH.
TL;DR: In this article, the chemistry of the fixation process used in the field is poorly understood and the intent of the first step is to form insoluble Fe arsenate, the second to bind the soil.
TL;DR: In this article, an iron-III-loaded chelating resin resin (Fe-LDA) with lysine-N α, N α -diacetic acid functional groups has been prepared and its adsorption characteristics for arsenic(III) and arsenic(V) have been examined.
Abstract: An iron(III)-loaded chelating resin (Fe-LDA) with lysine-N α ,N α -diacetic acid functional groups has been prepared and its adsorption characteristics for arsenic(III) and arsenic(V) have been examined. Arsenic(V) was strongly adsorbed to the resin in the pH range from 2 to 4, while arsenic(III) was moderately adsorbed between pH 8 and 10. The isotherm data for arsenic(V) at pH 3.5 fitted well to a Langmuir equation with a very large binding constant of 7.2 × 10 4 dm 3 mol −1 and a capacity constant of 0.74 mmol g −1 The data for arsenic(III) at pH 9 also fitted to a Langmuir equation, with a binding constant of 190 dm 3 mol −1 and a capacity constant of 0.84 mmol g −1 . Regeneration of the resin was successfully carried out with 0.1 mol dm −3 sodium hydroxide solution. Both arsenic compounds can be almost quantitatively recovered from the resin under these conditions. Only a small amount of ferric ions (less than 0.1 %) was observed to come off the resin during the regeneration with alkaline solutions. Since the Fe-LDA resin showed little affinity for arsenic(III) in acidic media, the present adsorption system can provide satisfactory separation of arsenic(V) from arsenic(III). Arsenic(V) was successfully concentrated in the column packed with Fe-LDA resin from its dilute solution.
01 Mar 1996
TL;DR: In this article, the adsorption of selenite (SeO2−3) on different polymorphic forms of iron oxyhydroxides and amorphous ferrihydrite was studied as a function of time, temperature, pH, and concentration of adsorbate(s) and adsorbent(s).
Abstract: Adsorption of selenite (SeO2−3) on different polymorphic forms of iron oxyhydroxides and amorphous ferrihydrite was studied as a function of time, temperature, pH, and concentration of adsorbate(s) and adsorbent(s). Analysis of adsorption data indicates that the surfaces of all the forms of oxyhydroxides and ferrihydrite are heterogeneous in nature and that adsorption fits into a heterogeneous site binding model. The adsorption capacity of oxyhydroxides for SeO2−3follows the order β-FeOOH < α-FeOOH < γ-FeOOH < δ-FeOOH < ferrihydrite.
TL;DR: The corrosion of α-iron in 0.1 mol 1−1 NaHCO3 solutions, with or without additional NaCl, leads to the formation of a deep green homogeneous layer which covers the metallic surface as discussed by the authors.
TL;DR: In this article, the reaction of ferric chloride and β-diketones in alkaline methanol solution represents a good synthetic route to hexairon(III) clusters [MFe6-(OCH3)12(L)6]+ (M = Na, Li), which exhibit an unusual sixfold molecular symmetry.
Abstract: The reaction of ferric chloride and β-diketones (HL) in alkaline methanol solution represents a good synthetic route to hexairon(III) clusters [MFe6-(OCH3)12(L)6]+ (M = Na, Li), which exhibit an unusual sixfold molecular symmetry. Single-crystal X-ray diffraction showed that the six octahedrally coordinated iron(III) ions define a ring and are linked by twelve bridging methoxide ligands. The resulting [Fe6(OCH3)12] skeleton has the remarkable property of acting as a host for an alkali-metal ion both in the solid state and in organic solution, as demonstrated by 23Na and 7Li NMR experiments. The magnetic behavior of these systems is consistent with the presence of a nonmagnetic S = 0 ground state and of antiferromagnetic exchange interactions between the high-spin ferric ions. The energy of the excited states was studied in detail by high-field DC and pulsed-field differential magnetization experiments at 0.7 and 1.5 K. Single-crystal susceptibility measurements at variable temperature revealed a sizeable magnetic anisotropy, which has been successfully analyzed in terms of single-ion and dipolar contributions. The results are relevant to research into the origin of superparamagnetic-type behavior in transition-metal clusters.
TL;DR: Purification of recombinant rat tyrosine hydroxylase containing 0.5-0.7 iron atoms/subunit and lacking bound catecholamine has permitted studies of the redox states of the resting enzyme and the enzyme during catalysis, which reveals a fraction of the enzyme is oxidized during turnover.
TL;DR: Mössbauer spectroscopy found no difference in the total amount of iron in SN between PD and control brains, andMeasurements performed on fresh‐frozen, formalin‐fixed, and lyophilized samples demonstrated the presence of ferric (Fe3+) iron only, both inPD and control SN.
Abstract: We used Mossbauer spectroscopy to study the iron content, the redox state, and the binding site of iron in substantia nigra (SN) from parkinsonian (PD) and control brains. Measurements performed on fresh-frozen, formalin-fixed, and lyophilized samples demonstrated the presence of ferric (Fe3+) iron only, both in PD and control SN. Ferrous iron, if present at all, may represent at most 5% of the total iron. We found no difference in the total amount of iron in SN between PD and control brains. The Mossbauer spectra observed at 4.1 K in fresh (frozen or lyophilized) samples were different from those obtained in formalin-fixed (frozen or lyophilized) samples. In the fresh samples, only ferritin-like iron was observed, whereas in the samples frozen or lyophilized from formalin, non-ferritin iron was detected.
TL;DR: It is concluded that the catalytic conversion of ferric α-hydroxyheme to verdoheme by heme oxygenase requires molecular oxygen and one reducing equivalent.
TL;DR: Determination of the diffusion coefficient by irradiating the lower section of a cylinder of gel, which was then imaged repeatedly over time with a clinical magnetic resonance imager, is described and a method of reducing ferric ion diffusion by adding a chelator and the cross linkage agent formaldehyde is suggested.
Abstract: Ferrous‐sulfate‐doped gelatin gel dosimeters are useful tools for the measurement of three‐dimensional absorbed radiation dose distributions. The diffusion of ferric ions through these gels causes degradation with time of the dose distribution image. It would be useful to reduce ferric ion diffusion without decreasing gel sensitivity. The amount of ferric ion diffusion is a function of the time delay after radiation, the gel temperature, and the gel concentration. These effects can be quantified by measuring the ferric ion diffusion coefficient. Determination of the diffusion coefficient by irradiating the lower section of a cylinder of gel, which was then imaged repeatedly over time with a clinical magnetic resonanceimager, is described. Analysis of the edge spread function formed at each of several times after irradiation by drawing a profile over the imaged junction between the irradiated and unirradiated halves of the cylinder, gave estimates of the variance of the edge spread function. These variances were used to obtain an estimate of the ferric ion diffusion coefficient for the gel. A method of reducing ferric ion diffusion by adding a chelator and the cross linkage agent formaldehyde is suggested. The chelators investigated were 1,10 phenanthroline, xylenol orange, and bathophenanthroline disulfonic acid. These reduced diffusion to varying extents, and influenced the gel sensitivity. The diffusion coefficient in gels containing xylenol orange was found to be 0.44 mm2h−1. The gel sensitivity was 0.0093 s−1Gy−1. This compared with a diffusion coefficient of 0.82 mm2h−1 for the base line gel that did not contain formaldehyde or chelators. The sensitivity of this base line gel was 0.0129 s−1Gy−1. The addition of xylenol orange produced the most improved gel dosimeter of the gels studied. This gel had a decreased ferric ion diffusion coefficient and a decreased sensitivity. It was still sensitive enough to be useful.
TL;DR: The concept of active iron-transport-mediated drug delivery can now be extended to drug conjugates that can enter the cell through multiple outer membrane receptors, which would allow active drug delivery by multiple iron receptor recognition and transport processes.
TL;DR: In this article, a pretreatment method, ferrous ion-peroxide oxidation combined with coagulation, has been studied and the results have shown that the optimum pH value is below 4 and the suitable ion dosage is 200 mg/l, while the residue have proved biodegradable when hydrogen peroxide dosage is 30 g/l.
TL;DR: It is suggested that reduction of Fe(III) to ferrous [Fe(II)] plays a role in the movement of iron into soybean symbiosomes.
Abstract: To identify possible iron sources for bacteroids in planta, soybean (Glycine max L. Merr.) symbiosomes (consisting of the bacteroid-containing peribacteroid space enclosed by the peribacteroid membrane [PBM]) and bacteroids were assayed for the ability to transport iron supplied as various ferric [Fe(III)]-chelates. Iron presented as a number of Fe(III)-chelates was transported at much higher rates across the PBM than across the bacteroid membranes, suggesting the presence of an iron storage pool in the peribacteroid space. Pulse-chase experiments confirmed the presence of such an iron storage pool. Because the PBM is derived from the plant plasma membrane, we reasoned that it may possess a ferric-chelate reductase activity similar to that present in plant plasma membrane. We detected ferric-chelate reductase activity associated with the PBM and suggest that reduction of Fe(III) to ferrous [Fe(II)] plays a role in the movement of iron into soybean symbiosomes.
Patent•
22 Mar 1996
TL;DR: In this article, a method of processing a sulphide mineral composition which at least partly comprises an iron containing mineral is described, the method comprising the steps of: (a) milling said composition to a particle size P80 of 20 microns or less; (b) leaching said composition with a solution comprising sulphuric acid and ferric ions at ambient pressure whilst sparging with an oxygen containing gas in an open tank reactor at a temperature of up to about the boiling point of the solution; (c) precipitating excess iron and separating said iron together with
Abstract: The present invention relates to a method of processing a sulphide mineral composition which at least partly comprises an iron containing mineral, the method comprising the steps of: (a) milling said composition to a particle size P80 of 20 microns or less; (b) leaching said composition with a solution comprising sulphuric acid and ferric ions at ambient pressure whilst sparging with an oxygen containing gas in an open tank reactor at a temperature of up to about the boiling point of the solution, whereby at least some of the acid and at least some of the ferric ions are obtained from dissolution of the iron containing mineral, and ferrous ions generated by the leaching reaction are substantially re-oxidised to ferric ions in the leaching solution; (c) precipitating excess iron and separating said iron together with any solid materials from the leaching solution; (d) extracting desired metal ions from the leaching solution by solvent extraction with an organic solvent, such that the raffinate comprises sulphuric acid and ferric ions; (e) returning the raffinate to the leaching tank and blending with further milled composition; (f) separating the metals from the organic phase obtained in step (c) by stripping with electrolyte and electrowinning.
TL;DR: In this paper, the electron transfer reactivity of microperoxidase-8 (MP8) has been studied by nanosecond flash photolysis methods and it was shown that the ferryl species is generated by intramolecular electron transfer within a ferric cation-radical porphyrin.
Abstract: The electron-transfer reactivity of microperoxidase-8 (MP8), the heme octapeptide derived from enzymatic cleavage of cytochrome c, has been studied by nanosecond flash photolysis methods. Ferric MP8 is rapidly oxidized by photogenerated Ru(bpy)33+ in acidic solutions to a ferric cation-radical porphyrin (k ∼ 5.6 × 109 M-1 s-1); the oxidation product in alkaline solutions is ferryl MP8 (k ∼ 2.2 × 109 M-1 s-1). Numerical simulations of the kinetics for the direct oxidation of ferric to ferryl MP8 predict a marked pH effect on the rate of reaction in alkaline solutions; however, only a very weak pH dependence is observed in the range 7−8.5, indicating that the ferryl species is generated by intramolecular electron transfer within a ferric cation-radical porphyrin. Transient spectra taken between pH 6 and 8.5 show increasing ferryl absorption as the pH is increased, demonstrating a pH-dependent equilibrium between the two oxidized forms of MP8.
TL;DR: In this article, a systematic study of the properties and reactivities of iron(III) porphyrin peroxo complexes containing ligands with different electronic properties has been undertaken, while the spectral propert
Abstract: A systematic study of the properties and reactivities of iron(III) porphyrin peroxo complexes containing ligands with different electronic properties has been undertaken. While the spectral propert...
Patent•
22 Jul 1996
TL;DR: In this article, the use of a defined class of gelling agents for hydrocarbons which provide excellent results in such fracturing is discussed. But this is restricted to improved hydrocarbon gels which find use in the fracturing of petroleum producing formations.
Abstract: This invention relates to improved hydrocarbon gels which find use in the fracturing of petroleum producing formations. In particular it relates to the use of a defined class of gelling agents for hydrocarbons which provide excellent results in such fracturing. The gelling agents comprise combinations of selected orthophosphate esters and ferric ammonium citrate or lower alkyl amine derivative thereof. The lower alkyl amine derivatives are referred to as ferric alkylamine citrates.
TL;DR: Anhydrous FeCl 3 in CH 2 Cl 2 at room temperature and 0 °C has been used to debenzylate monosaccharides and oligosacchides in yields generally greater than 70% as discussed by the authors.
TL;DR: Results indicate that iron is capable of inducing multiple changes in renal tubular epithelial function, and that iron to impair wound healing may be related to diminished expression of the beta 1 integrin subunit and perhaps to impaired proliferation.