α-FeOOH Particles Research Articles

Effective inactivation of Escherichia coli in aqueous solution by activated carbon-supported α-FeOOH as heterogeneous Fenton catalyst with high stability and reusability

Activated carbon-supported goethite (α-FeOOH@AC) was prepared by a simple impregnation method to catalyze hydrogen peroxide (H2O2) for effective inactivation of Escherichia coli (E. coli) with α-FeOOH and AC as controls. As expected, α-FeOOH particles were uniformly distributed on AC surfaces and surface-bound Fe(III) was partially converted to Fe(II) by structural hydroxyl groups of AC. The resultant Fe(II) catalyzed H2O2 to generate hydroxyl radicals (·OH) for effective E. coli inactivation by destroying its membrane and intracellular substances. The α-FeOOH@AC-H2O2 system therefore achieved an effective inactivation efficiency of 4.5 log, which was much higher than 1.6 log of the α-FeOOH-H2O2 system and 1.9 log of the AC-H2O2 system. Besides, due to the cycle of Fe(III)/Fe(II) redox on AC surface during reaction, high inactivation efficiency and low leaching iron concentration of 0.29 mg/L could be achieved at neutral condition. In addition, the α-FeOOH@AC showed excellent stability and reusability, and the used α-FeOOH@AC could be refreshed by eluting surface-bound iron oxides and reloading α-FeOOH particles with the above impregnation method. Our study demonstrated that α-FeOOH@AC is an effective and stable heterogeneous Fenton catalyst for the inactivation of E. coli in surface water treatment.

Electrorheology and shear dependent reversible gelation of elongated α-FeOOH suspensions

We study the effect of applying an external electric field (E) on the rheology and microstructure of α-FeOOH, length (L) = 488 ± 20 nm and an aspect ratio of (5 ± 0.8) – in – silicone oil suspensions (α-FeOOH/silicone oil). The α-FeOOH/silicone oil suspensions show Newtonian response up to α-FeOOH particle volume fraction of 0.039 when no E is applied. The suspensions exhibit τy ~ E2 and E1.5 scaling in the low and high E regimes respectively and the normalized τy versus E data of the suspensions collapses onto single master curve, irrespective of the particle loading and applied E. The solid-like behavior of the suspensions is also evident from the frequency-independent storage modulus, and the plateau in relaxation modulus with applied E. The optical microscopy reveals the E driven irreversible network formation of α-FeOOH particles, which does not relax to a uniform dispersion of α-FeOOH particles when the E is switched off. The suspensions demonstrate a reversible ER response once they are sheared at constant shear rate of 10 s−1.

Effect of trichloroacetic acid on iron oxidation: Implications on the control of DBPs and deposits in drinking water

In drinking water distribution system (DWDS), disinfection byproducts (DBPs) have a large possibility of participating in iron oxidation by dissolved oxygen (DO), which may induce particle structure transformations and increase unknown risks. In this work, the influence of trichloroacetic acid (TCAA, one of the most typical DBPs) on iron oxidation processes was studied, and the potential effects of the resulting α-FeOOH particles were evaluated through two aspects: (i) influence on the bacterial community and (ii) toxicity to human cells. TCAA promoted iron oxidation process through an Fe−O−C linkage, which led to a sharper surface of the particles (TCAA-mediated Fe oxide particles, TFOP) than that without TCAA (Fe oxide particles, FOP). Interestingly, the influence of particles on the richness of bacterial community of drinking water was different under anaerobic and aerobic conditions: under anaerobic conditions, the richness of bacterial community increased with the addition of particles, while under aerobic conditions, the richness of bacterial community decreased. The higher affinity of TFOP for electron-accepting DO than FOP indicated the role of DO on TFOP under aerobic conditions. TFOP exhibited the strongest cytotoxicity among FOP and the actual deposits. DFT calculations confirmed that TCAA in iron particles promoted the adsorption and dissociation of H2O2 to generate more •OH with an obvious decrease in the energy barrier from 1.51 to 0.80 eV. This study indicates the high potential of adverse effects of DBPs on loose deposits in DWDS and gives implications for the control of DBPs and deposits in drinking water.

Bioinspired Anti-Oil-Fouling Hierarchical Structured Membranes Decorated with Urchin-Like α-FeOOH Particles for Efficient Oil/Water Mixture and Crude Oil-in-Water Emulsion Separation.

Designing and constructing a stable water-retention layer acting as the isolation between the oil and membrane surface holds great significance for solving the membrane fouling problems in oil/water separation, including common layered oil/water mixtures, immiscible oil-in-water emulsions, and even high-viscosity crude oil-in-water emulsions. Inspired by the self-cleaning property of sea urchin thorns, a bioinspired anti-oil-fouling hierarchically structured membranes decorated with urchin-like α-FeOOH particles was successfully prepared via the layer-by-layer (LBL) self-assembly method, maintaining numerous effective micro-nanopores. The hierarchical structured membrane exhibited superior superhydrophilicity/underwater superoleophobicity, high water-retention ability, and preferable anti-oil-fouling properties. Furthermore, the biomimetic membrane with controllable pore sizes could not only separate common layered oil/water mixtures but also effectively separate immiscible surfactant-stabilized oil-in-water emulsions of both low-viscosity crude oil and high-viscosity crude oil with an ultrahigh water flux up to 2598.4 L m-2 h-1 and an outstanding separation efficiency of 98.5%, revealing its promising prospect in oily wastewater treatment.

Fabrication of arrayed needle-like Fe-particle composite films under an applied magnetic field, and their angularly dependent transmittances

Needle-like Fe particles were synthesized by heat-treatment of needle-like α-FeOOH particles in an H2 atmosphere. The obtained needle-like particles and a UV-curable liquid urethane resin were mixed with 0.05 vol% of Fe particles, and the resulting slurry was formed into a film with a thickness of 150 μm. The needle-like Fe particles were arrayed normally to the film surface under a 10 mT magnetic field; subsequently, the urethane resin was cured by UV irradiation. The transmittance of the film was changed from 55.7% to 38.3% by adjusting the light irradiation angle from 0° to 60°. Next, a composite film containing needle-like Fe particles tilted at 30° from the film surface normal was prepared by rearranging the applied magnetic field. The angular dependence of the resulting film was much larger than that of the composite film with the needle-like particles arrayed normal to the film surface.

Plasma-deposition of α-FeOOH particles on biochar using a gliding arc discharge in humid air: a green and sustainable route for producing oxidation catalysts.

Non-thermal atmospheric plasma of the gliding arc type was used as a tool for goethite-on-biochar hybrid material preparation. Biochars were first prepared by carbonizing raffia bamboo (the leafstalk of raffia palm) pith at 300 °C (BC3), 500 °C (BC5) and 700 °C (BC7). A suspension of each biochar in Fe2+ aqueous solution was then exposed to a plasma discharge burning in humid air. α-FeOOH particles were thus formed and spontaneously deposited on the biochar surface. In order to investigate the effect of plasma species on the support during goethite deposition, biochars were also treated with plasma in the absence of Fe2+ ions and then characterized. Results revealed a substantial hydroxylation and slight N-doping of biochar after plasma treatment. The prepared composite materials were tested in oxidative degradation of nitroresorcinol. The catalytic performances were in the order Fe-BC3 < Fe-BC7 < Fe-BC5 according to the abatement efficiency and half-time values obtained for each catalyst. This study establishes that waste biomass and atmospheric air can be simultaneously valorised for green production of heterogeneous catalysts.

Influence of Ni(II), Cu(II) and Cr(III) on the formation, morphology and molecular adsorption properties of α-FeOOH rust particles prepared by aerial oxidation of neutral Fe(II) solutions

To elucidate the role of alloying metals such as Ni, Cu and Cr in weathering steels on the formation of α-FeOOH rust by atmospheric corrosion of the steels in industrial and urban districts, influence of alloying metal ions on the formation, morphology and adsorption properties of α-FeOOH particles synthesized by aerial oxidation of neutral FeSO4 solution was examined. The addition of Cu(II) and Cr(III) dramatically suppresses the crystal growth of α-FeOOH and turns the rod-shaped α-FeOOH particles into nano-sized irregular ones. Besides, increase of amount of added Cr(III) forms the iron oxyhydroxysulfate named as Schwertmannite (Fe8O8(SO4)(OH)6). Whereas, the Ni(II) addition shows no noticeable influence on the growth of α-FeOOH crystal and particles. These results imply that the inhibitory effect of crystal and particle growth of α-FeOOH is in order of Cr(III) > Cu(II) >> Ni(II). The adsorption of CO2 gas on the α-FeOOH particles is impeded by adding Cu(II) and Cr(III). Whereas, the formation of Schwertmannite by adding Cr(III) enhances the CO2 and SO2 adsorption. These results suggest that alloying Cu and Cr in weathering steels inhibit the crystal and particle growth of α-FeOOH to accelerate the formation of protective rust layer composed of fine α-FeOOH and/or Schwertmannite rust particles on the steels in urban and industrial atmosphere.

Fabrication of textured CoFe2O4 ceramics by a novel RTGG method using rod-like α-FeOOH particles as templates

A textured CoFe2O4 ceramic was fabricated by reactive template grain growth (RTGG) method using rod-like α-FeOOH particles as templates. The template particles were synthesized by hydrothermal method, the particles showed good crystallization and rod-like shape with a diameter of 0.1–0.2 μm and an aspect ratio of 20–50. {ll0} oriented CoFe2O4 ceramic was obtained after a sintering process. The ceramic sintered at 1150 °C for 4 h showed dense and oriented structure with orientation degree of 0.89. Different magnetic hysteresis loops were observed along the in-plane and out-of-plane direction of the textured CoFe2O4, which was due to anisotropy properties of the sample. The textured ceramic exhibited an in-plane Ms enhancement (355 emu/cm3) compared to that of the non-textured ceramics (320 emu/cm3) in the same sintering conditions.

Water bath synthesis and enhanced photocatalytic performances of urchin-like micro/nanostructured α-FeOOH

Abstract

Synthesis of Goethite α-FeOOH Particles by Air Oxidation of Ferrous Hydroxide Fe(OH)2 Suspensions: Insight on the Formation Mechanism

Iron oxide and iron oxyhydroxide particles, particularly, the goethite α-FeOOH phase, are environmentally friendly materials and are used in various technological applications as adsorbents, precursors of Fe powders for magnetic recording media, and pigments. In this work, the formation process of α-FeOOH by air oxidation of Fe(OH)2 suspensions has been studied. The effects of the air flow rate, as well as of the reactant concentration ratio, R (=[(OH)−]/[Fe(II)]), on the reaction product were analyzed. It has been found that the morphology and the size of the α-FeOOH particles can be modified by means of the air flow rate. Furthermore, by performing a detailed microscopic analysis of the morphology of the initial, intermediate, and final reaction products, we have obtained evidence of epitaxial growth of α-FeOOH on the Fe(OH)2 substrate. It is suggested that the similarity between the anion arrangements in both phases facilitates this process. Based on these results, a pathway for the formation of α-FeOO...

Removal of Heavy Metal Ions by Photoelectrodeposition in Aqueous Solutions

In order to remove hazardous heavy metal ions dissolved in an aqueous environment, the photoelectrodeposition effect on the removal of Pb(II), Cu(II), Cd(II), and Zn(II) ions has been investigated for the (CeO2)1-X(Ln2O3)X (Ln = La, Sm, Gd) photocatalyst oxide particles combined with fine α-FeOOH particles. This effect is also compared with titanium-based oxides. The mixture of 1 mol%α-FeOOH and these photocatalyst oxides showed a high photoelectrodeposition ability particularly for Pb(II) ions under photo irradiation. The removal efficiency of Pb(II) ions was high under the UV irradiation and it decrased with increasing the wavelength of light toward the visible region. This result indicates that the coexistence of fine α-FeOOH particles with (CeO2)1-X(Ln2O3)X particles contributes to an efficient separation of holes and electrons generated by the photo irradiation. The high-resolution scanning electron microscopic observation of the samples revaled that fine α-FeOOH particles supported on the surface of the photocatalyst oxide particles are effective for the charge separation between holes and electrons. This effect is caused by the redox reaction occurring for the transfer of electrons to the surface of α-FeOOH-(CeO2)1-X(Ln2O3)X particles. These composite particles were also found to be effective for the removal of other heavy ions at low concentrations. The removal efficiency of the heavy metal ions is determined by the standard electrode potential of elements involved.

Manganese doped goethite: Structural, optical and adsorption properties

Pure and manganese doped (0.22–1.87wt.%) goethite (α-FeOOH) samples were prepared by co-precipitation method. The structural properties of the samples were studied using XRD, Raman, TG-DTA, UV–vis and TEM techniques. The XRD patterns of all the samples confirmed goethite to be the only crystalline phase. The lattice parameters ‘a’ and ‘c’ steadily decreased, whereas ‘b’ increased with the increase of Mn(II) content due to Jahn Teller effect. Raman spectra showed a strong peak at 399cm−1 with other prominent peaks at 242, 292, 479, and a very small broad peak 550cm−1 for the pure goethite sample. The observed blue and red shifts of peak positions after Mn(II) doping in Raman spectra have been attributed to phonon confinement, strain, defects and distortion in crystal structure. The DTA peak corresponding to decomposition of goethite to hematite shifted to higher temperature (320–335°C) due to Mn(II) doping. Distinct changes in the size and geometrical shape of Mn-substituted α-FeOOH particles were observed in SEM micrographs. The TEM image of pure goethite revealed the acicular particles to be nano range. Depending on Mn(II) concentration in goethite matrix, red shifts were observed in the UV–vis spectra. The indirect bandgaps for all the samples were at relatively lower energy levels than the direct bandgaps. Adsorption capacities of Pb(II), Cd(II), Cu(II) and Zn(II) on Mn doped sample (0.43% Mn) showed two- to three-fold increase when compared to undoped goethite.

Synthesis and Morphology of Platelet α-FeOOH and γ-Fe2O3 Nanoparticles for Cancer Therapy Using Hysteresis-Loss Heating

The morphology of platelet α-FeOOH, a precursor for synthesizing γ-Fe2O3 particles for use in cancer therapy by hysteresis-loss heating, was investigated with the aim of reducing the size of γ-Fe2O3 particles. The α-FeOOH particles were synthesized by the precipitation of ferric ions in alkaline solution containing ethanolamine, and crystals were grown via hydrothermal treatment. The particle length of α-FeOOH was reduced on lowering the precipitation temperature and maintaining it in the range from −3°C to 6°C, whereas the ratio of the long and short axes was maintained. The axial ratio of the α-FeOOH particles was remarkably affected by the precipitant's aging temperature in the range of 4–60°C, and became smaller when the aging temperature was lowered. The addition of Si was effective for reduction of the particle length of α-FeOOH. Platelet α-FeOOH particles with a particle length of ~40 nm and an axial ratio of ~1.5 were obtained by using Si as an addictive and employing precipitation, aging, and hydrothermal treatment temperatures of −3.5°C, 4°C, and 150°C, respectively.

Magnetic properties in oriented platelet Fe3O4 particles prepared by the polyol method using α-FeOOH as precursors

Magnetic properties of platelet Fe3O4 particles were studied to apply them to magnetic hyperthermia or thermoablation using hysteresis-loss heating. As precursor materials, platelet α-FeOOH particles were synthesized by a hydrothermal treatment of the precipitated Fe3+ ions in an alkaline solution of ethanolamine. Spinel-structured iron oxide particles were obtained from the platelet α-FeOOH particles by a liquid-phase reduction process using tetra-ethylene glycol as the reducing agent and were recognized as platelet particles with size 30–100nm by transmission electron microscopy. Their chemical composition and crystal structure were confirmed to be that of Fe3O4 by X-ray diffraction and Mössbauer analyses. The coercive force and saturation magnetization of the Fe3O4 particles were 11.9kA/m and 77.9Am2/kg, respectively. A tape was prepared by orientating the platelet Fe3O4 particles in such a way that the particle planes were parallel to the tape plane. The calculated magnetic anisotropy field of the Fe3O4 particles was about two times larger than the in-plane coercive force of 12.6kA/m of the oriented tape. The saturation field in direction perpendicular to the oriented tape was 390kA/m, which is close to the demagnetizing field in the platelet Fe3O4 particles.

Formation of magnetite rust particles by reacting iron powder with artificial α-, β- and γ-FeOOH in aqueous media

To simulate the atmospheric corrosion of steels, magnetite (Fe3O4) rust particles were prepared in aqueous media containing iron powder (α-Fe) and artificial α-, β- and γ-FeOOH particles at pH=6.0 and 50°C for 24h. The Fe3O4 formation was not recognized by treating the iron powder with α-FeOOH. When the iron powder treated with β- and γ-FeOOH, these materials were dissolved to generate Fe3O4 and α-FeOOH particles. The amount of formed Fe3O4 particles was in the order of β-FeOOH>γ-FeOOH≫α-FeOOH, which was strongly related to the density and solubility of FeOOH.

Preparation and photocatalytic activity of rutile TiO2 and goethite composite photocatalysts

Rutile TiO 2 and goethite (α-FeOOH) composite photocatalysts were fabricated by hydrolysis and precipitation using titanium tetrachloride as a precursor and α-FeOOH as a support. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results show that at lower temperature, rutile TiO 2 particles coat on the surface of α-FeOOH particles to form rutile TiO 2 -α-FeOOH composite photocatalyst. At higher temperature, iron ions are doped into the rutile TiO 2 lattice to form iron-doped rutile TiO 2 tubes; at medium temperature, the sample is a mixture with both composite and iron-doped structures. The photocatalytic activity of the samples is estimated by their ability to degrade methyl orange under irradiation with ultraviolet-visible light (200–800 nm) at ambient temperature. The photocatalytic activities of the samples are improved compared with that of pure rutile TiO 2 and α-FeOOH. The sample containing a mixture of composite and iron-doped structures shows the highest photocatalytic activity of that investigated. As a result, the photocatalytic activity of Ti 2 O could be improved effectively by combining with α-FeOOH or doping iron. 以四氯化钛为钛源, 针铁矿(帽-FeOOH)为载体, 采用水解沉淀法制备了金红石相二氧化钛(Ti 2 O)与帽-FeOOH的复合光催化材料, 并采用X射线衍射/扫描电子显微镜/透射电子显微镜/X射线能量散射谱和X射线光电子能谱对样品进行了表征. 结果表明, 低温下, 金红石相Ti 2 O包覆于帽-FeOOH表面, 并形成复合结构; 较高温下, 铁离子进入金红石相Ti 2 O晶格, 并形成铁掺杂金红石相Ti 2 O纳米管; 中温下, 样品兼有复合和掺杂两者特征. 在室温下以甲基橙为降解对象, 采用钨灯+氘灯(波长200–800 nm)为光源, 对样品的光催化活性进行了测试. 结果表明, 样品对甲基橙的光催化降解效果良好; 与纯帽-FeOOH和金红石相Ti 2 O相比, 不同结构样品的光催化活性均有所提高, 其中, 复合兼掺杂型样品的光催化活性最高. 由此可见, 与帽-FeOOH复合和铁掺杂是提高Ti 2 O光催化活性的有效途径. The structure of rutile TiO 2 and α-FeOOH composite photocatalysts can be controlled by adjusting reaction temperature, and their photocatalytic activity is maximized when they possess a core-shell structure with Fe 3+ doping.

Formation of AgFeO2, α-FeOOH, and Ag2O from mixed Fe(NO3)3–AgNO3 solutions at high pH

Precipitation of ternary oxide silver ferrite (AgFeO2), iron oxyhydroxide goethite (α-FeOOH) and silver(I) oxide (Ag2O) from mixed Fe(NO3)3–AgNO3 solutions in a whole [Ag+]:[Fe3+] concentration ratio range at high pH was investigated using X-ray powder diffraction (XRD), 57Fe Mössbauer, FT-IR and UV–Vis–NIR spectroscopies and field emission scanning electron microscopy (FE-SEM). Strong alkalis organic tetramethylammonium hydroxide (TMAH) or inorganic NaOH were used as precipitating agents. Monodispersed lath-like α-FeOOH particles were formed from a pure Fe(NO3)3 solution. The presence of Ag+ ions influenced the formation of the delafossite-type ternary oxide AgFeO2 beside α-FeOOH. The positions of XRD and Mössbauer lines did not suggest any significant incorporation of Ag+ ions into the α-FeOOH structure. AgFeO2 was formed in the precipitation system with the equimolar initial [Ag+]:[Fe3+] concentration ratio. The size and shape of AgFeO2 particles, as well as their structural polytype (2H or 3R), were dependent on reaction temperature, aging time and alkali used. In systems with an excess of Ag+ ions mixtures of AgFeO2 and Ag2O were formed. Single phase Ag2O precipitated from a pure AgNO3 solution.

Effect of Cu(II) on the formation, morphology and molecular adsorption properties of α-FeOOH rust particles prepared from acidic Fe(III) solutions

To simulate the atmospheric corrosion of weathering steels, α-FeOOH rust particles were synthesized from acidic Fe(NO3)3 solutions in the presence of Cu(II) at 50°C. No remarkable change of crystallinity of α-FeOOH was observed by adding Cu(II). Increasing the added Cu(II) formed the nano-sized ferrihydrite particles and reduced the size of α-FeOOH particles, leading to the increase of specific surface area. The Cu(II) added in the starting solution was less easily incorporated in the particles than Fe(III). The adsorption of corrosive gasses such as H2O, CO2 and SO2 on the rust particles was inhibited by the addition of Cu(II).

The effect of iridium(III) ions on the formation of iron oxides in a highly alkaline medium

The effect of the presence of Ir 3+ ions on the formation of iron oxides in a highly alkaline precipitation system was investigated using X-ray powder diffraction (XRD), 57Fe Mössbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Monodispersed lath-like α-FeOOH (goethite) particles precipitated by hydrothermal treatment in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as reference material. The presence of Ir 3+ ions in the precipitation system strongly influenced the phase composition, magnetic, structural and morphological properties of obtained samples. The formation of α-Fe 2O 3 (hematite) along with α-FeOOH in the first stage of hydrothermal treatment and the transformation of α-FeOOH and α-Fe 2O 3 to Fe 3O 4 (magnetite) by a longer hydrothermal treatment was caused by the presence of Ir 3+ ions. Ir 3+ for Fe 3+ substitution in the structure of α-FeOOH brought about changes in unit-cell dimensions, crystallinity, particle size and shape, hyperfine magnetic field and infrared bands positions. Ir 3+ for Fe 3+ substitution in the structure of α-Fe 2O 3 led to an increase in the temperature of the Morin transition; Mössbauer spectroscopy showed the presence of α-Fe 2O 3 in the antiferromagnetically ordered state at 293 K.

Synthesis and magnetic properties of platelet γ-Fe2O3 particles for medical applications using hysteresis-loss heating

Platelet γ-Fe2O3 particles of particle size less than 100nm were prepared for medical applications that use the hysteresis-loss heating of ferromagnetic particles. The γ-Fe2O3 particles were obtained through the dehydration, reduction, and oxidation of platelet α-FeOOH particles, which were synthesized by the precipitation of ferric ions in an alkaline solution containing ethanolamine, and the crystals grown using a hydrothermal treatment. The γ-Fe2O3 particles contained dimples formed by the dehydration of α-FeOOH particles. The coercive force and the saturation magnetization of the γ-Fe2O3 particles were in the ranges 11.9 to 12.7kA/m (150 to 160Oe), and 70 to 72Am2/kg (70 to 72emu/g), respectively. The specific loss power of the γ-Fe2O3 particles, estimated from their temperature-raising property measured under a peak magnetic field of 50.9kA/m (640Oe) and at a frequency of 117kHz, was 590W/g. This value is higher than that of spherical cobalt-containing iron oxide particles having equivalent coercive force and saturation magnetization, reflecting the larger area of the minor hysteresis loop measured under a peak magnetic field of 50.9kA/m (640Oe).