Showing papers on "Ferric published in 2007"

Synthesis of Fe3O4 nanoparticles with various sizes and magnetic properties by controlled hydrolysis.

Abstract: Nanoparticles of Fe(3)O(4) were synthesized by hydrolysis in an aqueous solution containing ferrous and ferric salts at various ratios with 1,6-hexanediamine as a base. It was found that the ferrous to ferric ratio influences the reaction mechanism for the formation of Fe(3)O(4). When the ratio of ferrous to ferric ions was increased, the formation of large hydroxide particles as a precursor of Fe(3)O(4) was promoted, which resulted in an increase in the size of Fe(3)O(4) nanoparticles. As a result, the mean diameter of Fe(3)O(4) nanoparticles increased from approximately 9 to approximately 37 nm as the molar percentage of ferrous ions with respect to the total iron ions was increased from 33 to 100%. Furthermore, it was demonstrated that magnetic properties of Fe(3)O(4) nanoparticles can be controlled by adjusting the molar ratio of ferrous to ferric ions as well as the particle diameter.

Fatty acid salts as stabilizers in size- and shape-controlled nanocrystal synthesis: the case of inverse spinel iron oxide.

Abstract: Various oleic acid salts are demonstrated to act as stabilizers for high-quality iron oxide nanocrystals, synthesized by thermal decomposition of ferric oleate. Changing the cation species in oleic acid salts allows different degrees of dissociation at high temperatures to be obtained, resulting in various stabilizer performances: Sodium oleate as stabilizer results in monodisperse iron oxide nanocrystals of cubic shape with precisely adjustable edge lengths between 7 and 23 nm. Dibutylammonium oleate and oleic acid, in contrast, induce growth of spherical nanocrystals in the same size range. Further adjustment of the growth conditions leads to {100}-bound bipyramidal nanocrystals with a single, (111) oriented twin plane. While the nanocrystal size is related to their superparamagnetic blocking temperature, the shape influences their magnetization hysteresis properties observed at low temperatures.

Short Communication Colour removal from landfill leachate by coagulation and flocculation processes

Abstract: A study was conducted to investigate the efficiency of coagulation and flocculation processes for removing colour from a semi-aerobic landfill leachate from one of the landfill sites in Malaysia. Four types of coagulant namely aluminium (III) sulphate (alum), ferric (III) chloride, ferrous (II) sulphate and ferric (III) sulphate were studied using standard jar test apparatus. Results indicated that ferric chloride was superior to the other coagulants and removed 94% of colour at an optimum dose of 800 mg/l at pH 4. The effect of coagulant dosages on colour removal showed similar trend as for COD, turbidity and suspended solids. This suggested that colour in landfill leachate was mainly contributed by organic matters with some insoluble forms that exhibited turbidity and suspended solids readings. The results from this study suggested that ferric chloride could be a viable coagulant in managing colour problems associated with landfill leachate.

The mechanisms of iron isotope fractionation produced during dissimilatory Fe(III) reduction by Shewanella putrefaciens and Geobacter sulfurreducens

Abstract: Microbial dissimilatory iron reduction (DIR) is widespread in anaerobic sediments and is a key producer of aqueous Fe(II) in suboxic sediments that contain reactive ferric oxides. Previous studies have shown that DIR produces some of the largest natural fractionations of stable Fe isotopes, although the mechanism of this isotopic fractionation is not yet well understood. Here we compare Fe isotope fractionations produced by similar cultures of Geobacter sulfurreducens strain PCA and Shewanella putrefaciens strain CN32 during reduction of hematite and goethite. Both species produce aqueous Fe(II) that is depleted in the heavy Fe isotopes, as expressed by a decrease in 56 Fe/ 54 Fe ratios or δ 56 Fe values. The low δ 56 Fe values for aqueous Fe(II) produced by DIR reflect isotopic exchange among three Fe inventories: aqueous Fe(II) (Fe(II) aq ), sorbed Fe(II) (Fe(II) sorb ), and a reactive Fe(III) component on the ferric oxide surface (Fe(III) reac ). The fractionation in 56 Fe/ 54 Fe ratios between Fe(II) aq and Fe(III) reac was ‐2.95‰, and this remained constant over the timescales of the experiments (280 d). The Fe(II) aq ‐ Fe(III) reac fractionation was independent of the ferric Fe substrate (hematite or goethite) and bacterial species, indicating a common mechanism for Fe isotope fractionation during DIR. Moreover, the Fe(II) aq ‐ Fe(III) reac fractionation in 56 Fe/ 54 Fe ratios during DIR is identical within error of the equilibrium Fe(II) aq ‐ ferric

Review of the hydrolysis of iron(III) and the crystallization of amorphous iron(III) hydroxide hydrate

Abstract: Hydrolysis of ferric solutions leads initially to mono- and dinuclear species which interact to produce further species of higher nuclearity. These polynuclear species age eventually to either crystalline compounds or to an amorphous precipitate (amorphous iron(III) hydroxide hydrate). Amorphous iron(III) hydroxide hydrate is thermodynamically unstable and gradually transforms to α-FeO(OH) and α-Fe2O3. These crystalline products form by competing mechanisms and the proportion of each in the final product depends on the relative rates of formation. The master variable governing the rates at which these compounds form is pH. Other important factors are temperature and the presence of additives. Most additives retard the transformation and by suppressing formation of α-FeO(OH) lead to an increase in the amount of α-Fe2O3 in the product; some additives also directly promote formation of the latter compound. Metal ions can oftxen replace a proportion of Fe in the α-FeO(OH) and α-Fe2O3 lattices. At high enough concentrations they can induce formation of additional phases. Additives may also modify the morphology of the crystalline products.

Molecular mechanisms involved in intestinal iron absorption.

Abstract: Iron is an essential trace metal in the human diet due to its obligate role in a number of metabolic processes. In the diet, iron is present in a number of different forms, generally described as haem (from haemoglobin and myoglobin in animal tissue) and non-haem iron (including ferric oxides and salts, ferritin and lactoferrin). This review describes the molecular mechanisms that co-ordinate the absorption of iron from the diet and its release into the circulation. While many components of the iron transport pathway have been elucidated, a number of key issues still remain to be resolved. Future work in this area will provide a clearer picture regarding the transcellular flux of iron and its regulation by dietary and humoral factors.

A new spectrophotometric method for the determination of ferrous iron in the presence of ferric iron

Abstract: A new spectrophotometric method for the determination of ferrous iron concentration in samples containing ferric iron is presented. This new method is a modification of the Muir o-phenanthroline ferrous iron determination method. The new method consists of the quantitative spectrophotometric determination of Fe(II) by o-phenanthroline, but in which the ferric iron is complexed with sodium fluoride to eliminate interferences. A critical experimental comparison between the Muir spectrophotometric method, the Kolthoff titrametric method and the new proposed method is presented. Whenever Fe(III) accounts for more than 50% of the total iron in a sample, the method of Muir overestimates Fe(II). The proposed method has a range of 1–10 μg ferrous iron. It is as insensitive to other metal ions as the original method of Muir and is insensitive to Fe(III) up to a point where Fe(III) might be as high as 95% total iron. The proposed method is suitable for Fe(II) determination in bacterial leaching systems, where Fe(II) might be as low as 1% of total iron.

Fe@Fe2O3 Core−Shell Nanowires as Iron Reagent. 1. Efficient Degradation of Rhodamine B by a Novel Sono-Fenton Process

Abstract: In this study, Fe@Fe2O3 core−shell nanowires were first used as a novel Fenton iron reagent. The nanowires were synthesized through the reduction of ferric chloride aqueous solution by sodium borohydride at ambient atmosphere, without protection of inert gases or vacuum. Rhodamine B (RhB) could be efficiently degraded in aqueous media by a novel sonochemical-assisted Fenton (sono-Fenton) system based on these Fe@Fe2O3 core−shell nanowires. The RhB degradation processes were monitored by UV−vis spectroscopy and total organic carbon (TOC) analysis. Fe@Fe2O3 core−shell nanowires showed much higher activity in the sono-Fenton system than other iron reagents such as commercial zerovalent iron powders (Fe0), ferrous ions (Fe2+), and ferric ions (Fe3+). It was found that near 100% decoloration and over 60% TOC removal of RhB (5 mg·L-1) could be achieved in 60 min by this novel sono-Fenton system with 0.018 mol·L-1 Fe@Fe2O3 core−shell nanowires. This new iron reagents before and after the sono-Fenton reaction wer...

Iron acquisition in Vibrio cholerae

Abstract: Vibrio cholerae, the causative agent of cholera, has an absolute requirement for iron and must obtain this element in the human host as well as in its varied environmental niches. It has multiple systems for iron acquisition, including the TonB-dependent transport of heme, the endogenous siderophore vibriobactin and several siderophores that are produced by other microorganisms. There is also a Feo system for the transport of ferrous iron and an ABC transporter, Fbp, which transports ferric iron. There appears to be at least one additional high affinity iron transport system that has not yet been identified. In iron replete conditions, iron acquisition genes are repressed by Fur. Fur also represses the synthesis of a small, regulatory RNA, RyhB, which negatively regulates genes for iron-containing proteins involved in the tricarboxylic acid cycle and respiration as well as genes for motility and chemotaxis. The redundancy in iron transport systems has made it more difficult to determine the role of individual systems in vivo and in vitro, but it may reflect the overall importance of iron in the growth and survival of V. cholerae.

Cryoradiolytic reduction of crystalline heme proteins: analysis by UV-Vis spectroscopy and X-ray crystallography.

Abstract: The X-ray crystallographic analysis of redox-active systems may be complicated by photoreduction. Although radiolytic reduction by the probing X-ray beam may be exploited to generate otherwise short-lived reaction intermediates of metalloproteins, it is generally an undesired feature. Here, the X-ray-induced reduction of the three heme proteins myoglobin, cytochrome P450cam and chloroperoxidase has been followed by on-line UV-Vis absorption spectroscopy. All three systems showed a very rapid reduction of the heme iron. In chloroperoxidase the change of the ionization state from ferric to ferrous heme is associated with a movement of the heme-coordinating water molecule. The influence of the energy of the incident X-ray photons and of the presence of scavengers on the apparent reduction rate of ferric myoglobin crystals was analyzed.

Spectroscopic investigation of ciprofloxacin speciation at the goethite-water interface.

Abstract: We investigated ciprofloxacin (a fluoroquinolone antibiotic) speciation as a function of pH in aqueous solution and in the presence of dissolved ferric ions and goethite using ATR-FTIR and UV−vis spectroscopy. The presence of dissolved and surface bound ferric species induced the deprotonation of the ciprofloxacin carboxylic acid group at pH < pKa1. The resultant ciprofloxacin zwitterions appeared to interact via both carboxylate oxygens to form bidentate chelate and bridging bidentate complexes within colloidal iron oxide−ciprofloxacin precipitates and bidentate chelates on the goethite surface. However, the structure of the aqueous ferric−ciprofloxacin complexes remains unclear. Our evidence for bidentate chelates (involving only the carboxylate oxygens) on the goethite surface was distinct from previous IR studies of fluoroquinolone sorption to metal oxides that have proposed surface complexes involving both the keto and the carboxylate groups. We find that the distinct ciprofloxacin surface complex pr...

Synthesis of Nanosize‐Necked Structure α‐ and γ‐Fe2O3 and its Photocatalytic Activity

Abstract: Highly dispersed nanometer-sized α-Fe2O3 (hematite) and γ-Fe2O3 (maghemite) iron oxide particles were synthesized by the combustion method. Ferric nitrate was used as a precursor. X-ray diffractometer study revealed the phase purity of α- and γ-Fe2O3. Both the products were characterized using field emission scanning electron microscope and transmission electron microscope for particle size and morphology. Necked structure particle morphology was observed for the first time in both the iron oxides. The particle size was observed in the range of 25–55 nm. Photodecomposition of H2S for hydrogen generation was performed using α- and γ-Fe2O3. Good photocatalytic activity was obtained using α- and γ-Fe2O3 as photocatalysts under visible light irradiation.

Synthesis, Characterization, and Bioavailability in Rats of Ferric Phosphate Nanoparticles

Abstract: Particle size is a determinant of iron (Fe) absorption from poorly soluble Fe compounds. Decreasing the particle size of metallic Fe and ferric pyrophosphate added to foods increases Fe absorption. The aim of this study was to develop and characterize nanoparticles of FePO(4) and determine their bioavailability and potential toxicity in rats. Amorphous FePO(4) nanopowders with spherical structure were synthesized by flame spray pyrolysis (FSP). The nanopowders were characterized and compared with commercially available FePO(4) and FeSO(4), including measurements of specific surface area (SSA), structure by transmission electron microscopy, in vitro solubility at pH 1 and 2, and relative bioavailability value (RBV) to FeSO(4) in rats using the hemoglobin repletion method. In the latter, the potential toxicity after Fe repletion was assessed by histological examination and measurement of thiobarbituric acid reactive substances (TBARS). The commercial FePO(4) and the 2 FePO(4) produced by FSP (mean particle sizes, 30.5 and 10.7 nm) had the following characteristics: SSA: 32.6, 68.6, 194.7 m(2)/g; in vitro solubility after 30 min at pH 1: 73, 79, and 85% of FeSO(4); and RBV: 61, 70, and 96%, respectively. In the histological examinations and TBARS analysis, there were no indications of toxicity. In conclusion, nanoparticles of FePO(4) have a solubility and RBV not significantly different from FeSO(4). Reducing poorly soluble Fe compounds to nanoscale may increase their value for human nutrition.

Synthesis of Iron Nanoparticles via Chemical Reduction with Palladium Ion Seeds

Abstract: We report on the synthesis of highly monodisperse iron nanoparticles, using a chemical reduction method Iron nanoparticles with an average diameter of 6 nm and a geometric standard deviation of 13 were synthesized at a pH of 950 from ferric chloride precursor with sodium borohydride as the reducing agent, polyacrylic acid as the dispersing agent, and palladium ions as seeds for iron nanoparticle nucleation The resulting nanoparticles were ferromagnetic at 5 K and superparamagnetic at 350 K The dispersing agent polyacrylic acid (PAA) was shown to prevent iron nanoparticles and possibly palladium clusters from aggregating; in the absence of PAA, only aggregated iron nanoparticles were obtained The addition of palladium ions decreased the diameter of iron nanoparticles presumably by providing sites for heterogeneous nucleation onto palladium clusters In the absence of palladium ions, the mean diameter of iron nanoparticles was approximately 110 nm and the standard deviation increased to 20 The pH of the solution also was found to have a significant effect on the particle diameter, likely by affecting PAA ionization and altering the conformation of the polymer chains At lower pH (875), the PAA is less ionized and its ability to disperse palladium clusters is reduced, so the number of palladium seeds decreases Therefore, the resulting iron nanoparticles were larger, 59 nm in diameter, versus 6 nm for nanoparticles formed at a pH of 950

Steap proteins: implications for iron and copper metabolism.

Abstract: Erythroid cells of the bone marrow, the most avid consumers of iron in the body, acquire ferric (Fe3+) iron exclusively via the transferrin cycling pathway. A long-standing fundamental molecular question of how ferric iron is handled in this pathway has been recently resolved by the identification of Steap3 (six-transmembrane epithelial antigen of the prostate 3) as an endosomal ferrireductase needed for efficient utilization of transferrin-delivered iron. Further characterization of Steap3 and other Steap proteins reveals a possible greater role of Steap proteins in iron and copper metabolism.