Ferric Nitrate Solution Research Articles

Application of Fe/Activated Carbon Catalysts in the Hydroxylation of Phenol to Dihydroxybenzenes

A series of Fe/activated carbon catalysts were prepared by impregnation of activated carbon with aqueous solution of ferric nitrate and employed in phenol hydroxylation to dihydroxybenzenes using hydrogen peroxide as oxidant. The samples were characterized by thermal analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), N2-adsorption, temperature-programmed oxidation mass spectrometry (TPO-MS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Part of the ferric (Fe(III)) species was reduced to ferrous (Fe(II)) species forming Fe3O4 when the Fe/activated carbon catalyst was heated at 400 °C for 3 h in air. Fe3O4 highly dispersed on activated carbon was found to be the active phase for the target reaction. The appearance of ferrous (Fe(II)) species greatly improved the catalytic activity. A phenol conversion of 41.3% and a yield of 36.0% to dihydroxybenzenes were obtained under the following optimal reaction conditions: catalyst ...

Preparation of hybrids consisting of expanded graphite and carbon nanotubes as conductive fillers of polybutylene terephthalate

Expanded graphite (EG) was loaded with iron by impregnating with ammonium carbonate and ferric nitrate solution. Carbon nanotubes (CNTs) were grown on the EG by iron-catalyzed chemical vapor deposition, using acetylene as a carbon source to form hybrids that were used as a conductive filler to produce conducting polybutylene terephthalate (PBT) composites by an extrusion method. It is found that the CNTs are not entangled and are easy to disperse. The CNT average diameters are 40, 20 and 40 nm, and their lengths are 2, 3.7 and 2.6 μ m for iron loadings of 1.13, 0.75 and 0.57 mass%, respectively. The thickness of the EG is reduced to 10–30 nm as a result of CNT insertion into the graphene layers of the EG. The content of CNTs in the hybrids increases from 50 to 85 mass% with the increasing iron content. The conductive PBT modified by the hybrids (5 mass%) derived from EG loaded with 0.75 w% iron has a surface resistance of 1.55 × 10 4 Ω / cm 2 , significantly lower than that ( 1.55 × 10 10 Ω / cm 2 ) of the PBT modified by CNTs with the same amount of filler added. [New Carbon Materials 2013, 28(6): 480–483]

Shape effects of goethite particles on their photocatalytic activity in the decomposition of acetaldehyde

The relationship between the photocatalytic activity of goethite (α-FeOOH) and the shape of its particles was investigated. Goethite particles with various morphologies (rod-like, array-like, and pancake-like) were synthesized through the hydrolysis of a ferric nitrate solution or the oxidation of Fe(OH)2. All the particles synthesized consisted of {110} and {021} facets. The photocatalytic activities of the different samples were examined for the decomposition of acetaldehyde under irradiation. It was found that the photocatalytic activity of goethite is affected by both the shape and the specific surface area of its particles. Further investigation of the effects of the particle shape indicated that the photocatalytic activity of the {021} facets is higher than that of the {110} facets of goethite. The goethite particles (short rod-like and pancake-like particles), therefore, exhibited higher photocatalytic activities than other particle types (long rod-like and array-like particles) owing to the greater {021} facets.

Preparation of Liquid Ferrate and the Optimization of Process Parameters

Ferrate is a powerful oxidant and disinfectant that has been proposed for use in drinking water treatment for more than a decade. The main obstacles in the application are costs and stability. In water treatment, using wet oxidation method to prepare liquid ferrate can save production costs. Saturated ferric nitrate solution can get higher efficiency and productivity to generate ferrate. Water quality has no obvious effect on the productivity of ferrate. The optimum alkaline concentration is 10-13 mol/L. The reaction time and temperature affect the quality of liquid ferrate product. The larger the mole ratio of sodium hypochlorite to ferric nitrate is, the greater the productivity of ferrate is. The proportion of sodium hypochlorite to ferric nitrate should be adjusted appropriately.

In Situ Structural Characterization of Ferric Iron Dimers in Aqueous Solutions: Identification of μ-Oxo Species

The structure of ferric iron (Fe(3+)) dimers in aqueous solutions has long been debated. In this work, we have determined the dimer structure in situ in aqueous solutions using extended X-ray absorption fine structure (EXAFS) spectroscopy. An Fe K-edge EXAFS analysis of 0.2 M ferric nitrate solutions at pH 1.28-1.81 identified a Fe-Fe distance at ∼3.6 Å, strongly indicating that the dimers take the μ-oxo form. The EXAFS analysis also indicates two short Fe-O bonds at ∼1.80 Å and ten long Fe-O bonds at ∼2.08 Å, consistent with the μ-oxo dimer structure. The scattering from the Fe-Fe paths interferes destructively with that from paths belonging to Fe(OH2)6(3+) monomers that coexist with the dimers, leading to a less apparent Fe shell in the EXAFS Fourier transform. This might be a reason why the characteristic Fe-Fe distance was not detected in previous EXAFS studies. The existence of μ-oxo dimers is further confirmed by Mössbauer analyses of analogous quick frozen solutions. This work also explores the electronic structure and the relative stability of the μ-oxo dimer in a comparison to the dihydroxo dimer using density function theory (DFT) calculations. The identification of such dimers in aqueous solutions has important implications for iron (bio)inorganic chemistry and geochemistry, such as understanding the formation mechanisms of Fe oxyhydroxides at molecular scale.

Watermelon used as a novel carbon source to improve the rate performance of iron oxide electrodes for lithium ion batteries

The pulp of a watermelon consists of watermelon juice and flesh wall. After a hydrothermal process at 160°C, the pulp turns into a carbon-based composite powder composed of micrometer particles and nanosheets (CPs–CSs). Through a similar hydrothermal process with the mixture of watermelon pulp and an ethanolic solution of ferric nitrate as the precursors, a powder of iron oxide–CPs–CSs composite is also synthesized. X-ray diffraction, scanning and transmission electron microscopies and BET surface area measurement are employed to study the compositions and structures of these composite powders. Their electrochemical properties as potential anode materials of lithium ion batteries are also investigated. It is found that after a heat treatment at 700°C and 800°C, the CPs–CSs composites are mesoporous carbon materials with a specific surface area of 898m2g−1 and 452m2g−1, respectively. The iron oxide–CPs–CSs composites after a heat treatment at 700°C and 800°C are all Fe3O4–CPs–CSs. When used as anode materials, both CPs–CSs and Fe3O4–CPs–CSs show very good rate performance. Thanks to the higher surface area of the carbon component, the 700°C-treated Fe3O4–CPs–CSs is superior to others in rate capability. It can deliver a discharge capacity of 350mAhg−1 even at a high current density of 2500mAg−1.

水热/超声法合成γ-Fe<sub>2</sub>O<sub>3</sub>纳米空心球及磁性

Combine the advantages of hydrothermal approach and ultrasonic method, Fe₃O₄ solid nanospheres with grain sizes of ~15 nm are prepared by hydrothermal approach. Then treat these Fe₃O₄ solid nanospheres with acid and finally sonicate in ferric nitrate solution, γ-Fe₂O₃ hollow nanospheres with grain size of ~5 nm are obtained. X-ray diffraction (XRD) and energy dispersive spectrometer (EDS), scanning electron/transmission electron microscopy (SEM/TEM), nitrogen adsorption and pore size distribution (BJH) prove that the sample is high purity γ-Fe₂O₃ hollow nanospheres with pore structure. Superconducting quantum interference device and stability experiment demonstrate that γ-Fe₂O₃ hollow nanospheres are superparamagnetism with a high saturation magnetization and chemical stability at room temperature.

Enhanced Microwave Absorption by Incorporating Fe3O4 Nanoparticles into Ordered Mesoporous Carbon

Novel Fe3O4/ordered mesoporous carbon (OMC) composite powders have been prepared by impregnation and reduction methods for the microwave absorbing application purpose. The Fe3O4nanoparticles were encapsulated in the mesopores of OMCs, and Fe3O4contents in the composite could be easily controlled by changing the concentration of ferric nitrate solution during the preparation. The Fe3O4/OMC composites show very excellent microwave absorbing properties with respect to pure OMC samples, in a frequency ranging of 8.2-12.4 GHz. A minimum reflection loss (RL) value of -32 dB at 11.35 GHz and a broader absorption band with the RL values under -10 dB are obtained when the thickness of samples is 1.6 mm. The enhanced microwave absorption of the Fe3O4/OMC nanocomposites is contributed to the better impedance match between dielectric loss and magnetic loss, which originates from the incorporation of magnetic species into OMC.

Toward quantifying the composition of soft tissues by spectral CT with Medipix3

To determine the potential of spectral computed tomography (CT) with Medipix3 for quantifying fat, calcium, and iron in soft tissues within small animal models and surgical specimens of diseases such as fatty liver (metabolic syndrome) and unstable atherosclerosis. The spectroscopic method was applied to tomographic data acquired using a micro-CT system incorporating a Medipix3 detector array with silicon sensor layer and microfocus x-ray tube operating at 50 kVp. A 10 mm diameter perspex phantom containing a fat surrogate (sunflower oil) and aqueous solutions of ferric nitrate, calcium chloride, and iodine was imaged with multiple energy bins. The authors used the spectroscopic characteristics of the CT number to establish a basis for the decomposition of soft tissue components. The potential of the method of constrained least squares for quantifying different sets of materials was evaluated in terms of information entropy and degrees of freedom, with and without the use of a volume conservation constraint. The measurement performance was evaluated quantitatively using atheroma and mouse equivalent phantoms. Finally the decomposition method was assessed qualitatively using a euthanized mouse and an excised human atherosclerotic plaque. Spectral CT measurements of a phantom containing tissue surrogates confirmed the ability to distinguish these materials by the spectroscopic characteristics of their CT number. The assessment of performance potential in terms of information entropy and degrees of freedom indicated that certain sets of up to three materials could be decomposed by the method of constrained least squares. However, there was insufficient information within the data set to distinguish calcium from iron within soft tissues. The quantification of calcium concentration and fat mass fraction within atheroma and mouse equivalent phantoms by spectral CT correlated well with the nominal values (R(2) = 0.990 and R(2) = 0.985, respectively). In the euthanized mouse and excised human atherosclerotic plaque, regions of calcium and fat were appropriately decomposed according to their spectroscopic characteristics. Spectral CT, using the Medipix3 detector and silicon sensor layer, can quantify certain sets of up to three materials using the proposed method of constrained least squares. The system has some ability to independently distinguish calcium, fat, and water, and these have been quantified within phantom equivalents of fatty liver and atheroma. In this configuration, spectral CT cannot distinguish iron from calcium within soft tissues.

Simple fabrication of a Fe2O3/carbon composite for use in a high-performance lithium ion battery

A simple approach was developed for the fabrication of a Fe2O3/carbon composite by impregnating activated carbon with a ferric nitrate solution and calcinating it. The composite contains graphitic layers and 10wt.% Fe2O3 particles of 20–50nm in diameter. The composite has a high specific surface area of ∼828m2g−1 and when used as the anode in a lithium ion battery (LIB), it showed a reversible capacity of 623mAhg−1 for the first 100 cycles at 50mAg−1. A discharge capacity higher than 450mAhg−1 at 1000mAg−1 was recorded in rate performance testing. This highly improved reversible capacity and rate performance is attributed to the combination of (i) the formation of graphitic layers in the composite, which possibly improves the matrix electrical conductivity, (ii) the interconnected porous channels whose diameters ranges from the macro- to meso- pore, which increases lithium-ion mobility, and (iii) the Fe2O3 nanoparticles that facilitate the transport of electrons and shorten the distance for Li+ diffusion. This study provides a cost-effective, highly efficient means to fabricate materials which combine conducting carbon with nanoparticles of metal or metal oxide for the development of a high-performance LIB.

New approaches to reprocessing of oxide nuclear fuel.

Dissolution of UO2, U3O8, and solid solutions of actinides in UO2 in subacid aqueous solutions (pH 0.9–1.4) of Fe(III) nitrate was studied. Complete dissolution of the oxides is attained at a molar ratio of ferric nitrate to uranium of 1.6. During this process actinides pass into the solution in the form of U(VI), Np(V), Pu(III), and Am(III). In the solutions obtained U(VI) is stable both at room temperature and at elevated temperatures (60 °C), and at high U concentrations (up to 300 mg mL−1). Behavior of fission products corresponding to spent nuclear fuel of a WWER-1000 reactor in the process of dissolution the simulated spent nuclear fuel in ferric nitrate solutions was studied. Cs, Sr, Ba, Y, La, and Ce together with U pass quantitatively from the fuel into the solution, whereas Mo, Tc, and Ru remain in the resulting insoluble precipitate of basic Fe salt and do not pass into the solution. Nd, Zr, and Pd pass into the solution by approximately 50 %. The recovery of U or jointly U + Pu from the dissolution solution of the oxide nuclear fuel is performed by precipitation of their peroxides, which allows efficient separation of actinides from residues of fission products and iron.

Adsorption of heavy metal ions on mesoporous silica-modified montmorillonite containing a grafted chelate ligand

The objective of this work is development of a new adsorbent on the base of an organoclay with a chelating ligand covalently attached to the clay mineral surface. The presence of a chelating ligand in the clay structure significantly improves its ability to immobilize heavy metal ions from contaminated sludge of wastewater. Montmorillonite and kaolinite were chosen as typical examples of expandable and non-expandable clay minerals. A two-step modification procedure comprised of sequential modification with oxides and grafting of a chelating agent to the modified clay minerals was used. Modifications with silica and ferric oxide were conducted by reacting the dispersed raw clay minerals with tetraethoxysilane and ferric nitrate solution. A chelating ligand, N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, was introduced into interlayer space of raw and modified clay minerals in aqueous solutions. Laboratory tests of the organoclay efficiency for purification of wastewater were conducted with the most promising sample, i.e., organoclay with the highest specific loading of chelating agent. Experiments were conducted with model wastewater containing either individual or mixed heavy metal ions. The modified organoclay displayed high adsorption capacity for heavy metal cations even in acidic media. The method of modification presented in this work can be used for synthesis of efficient adsorbents for applications in contaminated areas.

Polytypic transformations of aluminum hydroxide: A mechanistic investigation

The diffusion of ammonia vapors into a solution of aluminum nitrate or ferric nitrate results in the precipitation of their respective hydroxides and oxyhydroxides. Polymorphic phase formation of aluminum hydroxide is controlled by the rate of crystallization. The PXRD patterns of products obtained via vapor phase diffusion revealed that poorly ordered aluminum hydroxide is formed during the initial stages of crystallization. After 8 days, the formation of the bayerite phase of aluminum hydroxide was observed. Upon prolonged exposure to ammonia vapors, bayerite was transformed into gibbsite. The infrared spectrum of the product confirmed the presence of different polytypic phases of aluminum hydroxide. The results demonstrated that the crystal structure of metal hydroxides is controlled by the rate of crystallization, nature of the metal ion, site selectivity and specificity and preparative conditions.

Dialysis of aqueous solutions of nitric acid and ferric nitrate

The separation of an HNO 3 + Fe(NO 3) 3 mixture using an anion-exchange membrane Neosepta-AFN has been investigated in a two-compartment dialysis cell with stirrers. The experiments have proved that this membrane is a very good separator for this mixture, because nitric acid permeates well through the membrane and ferric nitrate is efficiently rejected. The separation is very efficient at high acid concentrations or low content of the salt in the mixture to be dialyzed.

New Method for H2S Removal in Acid Solutions

Several different technologies are available for H(2)S removal from the gas stream of medium capacity. Among them, the most widely used is Locat with more than 120 plants worldwide. In the last decade, many new processes, such as Sulfatreat-DO, Crystasulf, Caltech, and UCSR, were proposed to overcome the drawbacks of the state-of-the-art processes (low sulfur purity, chemical degradation, thiosulfate formation). We have developed a new H(2)S conversion method based on acid ferric nitrate solution, co-catalyzed by a heteropolyacid. H(2)S was converted to pure sulfur (>99.9 %), with no traces of organic compounds. Due to the acid pH of the solution, no chelant or surfactant was needed and iron content in the solution could reach very high levels. Keggin heteropolyacid (H(6)PW(9)V(3)O(40)) catalyzed the reoxidation of reduced ferrous solution with air at mild temperature and at very high reaction rate. The undesired side reaction (NO(x) formation) could be avoided by simply increasing the oxygen partial pressure.

Effect of citrate on the local Fe coordination in ferrihydrite, arsenate binding, and ternary arsenate complex formation

In oxic environments contaminated with arsenate (As(V)), small polyhydroxycarboxylates such as citrate may impact the structure of precipitating ferrihydrite (Fh) and thus the surface speciation of As(V). In this study, ‘2-line’ Fh was precipitated from ferric nitrate solutions that were neutralized to pH 6.5 in the presence of increasing citrate concentrations and in the absence or presence of As(V). The initial citrate/Fe and As/Fe ratios were 0–50 mol% and 5 mol%, respectively. The reaction products, enriched with up to 0.32 mol citrate per mole Fe, were characterized by X-ray diffraction, transmission electron microscopy, and Fe and As K-edge X-ray absorption spectroscopy. Citrate decreased the particle size of Fh by impairing the polymerization of Fe(O,OH) 6 octahedra via edge and corner linkages. In the presence of citrate and As(V), coordination numbers of Fe decreased by up to 28% relative to pure Fh. Citrate significantly reduced the static disorder of Fe–O bonds, implying a decreased octahedral distortion in Fh. Mean bond distances in Fh were not affected by citrate and remained constant within error at 1.98 Å for Fe–O, 3.03 Å for Fe–Fe1, and 3.45 Å for Fe–Fe2. Likewise, citrate had no effect on the As–Fe (3.31 Å) bond distance in As(V) coprecipitated with Fh. The As K-edge EXAFS data comply with the formation of (i) only monodentate binuclear ( 2C) As(V) surface complexes and (ii) combinations of 2C, monodentate mononuclear ( 1V), and outersphere As(V) surface complexes. Our results suggest that increasing citrate concentrations led to a decreasing 1V/ 2C ratio and/or that citrate increasingly impaired the formation of outersphere As(V) complexes. Moreover, citrate stabilized colloidal suspensions of Fh (pH 4.3–6.6, I ∼0.45 M) and reduced Fh formation at the expense of soluble Fe(III)-citrate complexes. At initial citrate/Fe ratios ⩾25 mol%, between 8% and 41% of total Fe was bound in Fe(III)-citrate complexes after Fh formation. Polynuclear Fe(III)-citrate species were found to bind As(V) via surface complexes indistinguishable by EXAFS from those of As(V) adsorbed to or coprecipitated with Fh. Our study implies that low molecular weight polyhydroxycarboxylates may enhance the mobility of As(V) in aqueous systems of high ionic strength (e.g., neutralizing acid mine drainage) by colloidal stabilization of suspended Fh particles and the formation of ternary As(V) complexes.

Removal of less biodegradable dissolved organic matters in water by superconducting magnetic separation with magnetic mesoporous carbon

Less biodegradable dissolved organic matters in water as typified by humic substances are known as precursors of carcinogenic trihalomethanes, and are removed about 60% by current advanced water treatments. However, further increase of the removal ratio is demand. In this study, magnetic mesoporous carbon (MMPC), which can adsorb the substances physically and be efficiently collected by using superconducting high gradient magnetic separation (HGMS), has been synthesized with coconut-shell-based activated carbon and ferric nitrate solution by the gas activation method. The MMPC has the maximum magnetization value of 30.7emu/g and an adsorption ability of 87% to 10mg/L humic acid in a short time. The standard MMPC having a magnetization of 6.43emu/g was able to be separated at magnetic field of 2T. Used MMPC regained the adsorption ability to 93.1% by N2 reactivation heat treatment. These results show promise for application of current water treatments by superconducting HGMS, which is suitable for high-speed water treatment without secondary wastes.

Synthesis of Fe/MgO nano-crystal catalysts by sol–gel method for hydrogen sulfide removal

The Fe/MgO nano-crystal catalysts were synthesized for removal of hydrogen sulfide (H 2S) in a biogas. The nano-crystalline catalyst supporting powders, magnesium oxide (MgO), were obtained by sol–gel method. Ferric ion from ferric nitrate solution was supported on the MgO nano-crystal powders to give 17.5 nm Fe/MgO crystal size by wet impregnation and calcinations. Catalytic activity for H 2S oxidation was carried out in a semi-batch reactor. Fe/MgO nano-crystal catalysts were held in an aqueous suspension with simulated H 2S gas bubbling for catalytic oxidation and regeneration. The catalysts showed marked catalytic properties such that elemental sulfur was produced during the regeneration with air. Fresh and spent catalysts were characterized by XRD, EDX, FTIR, TEM, and CHNS techniques. The performance of the synthesized Fe/MgO catalysts on H 2S oxidation from a biogas was examined using a packed column scrubber. The results show that the H 2S was specifically absorbed and oxidized by the Fe/MgO catalysts suspension at room temperature. The scrubbing process performed with no absorbing or reaction of CH 4 and CO 2 from the biogas.

Synthesis and gas sensing properties of biomorphic LaFeO 3 hollow fibers templated from cotton

Biomorphic LaFeO 3 hollow fibers with porous walls have been fabricated using cotton as biotemplates. Cotton fibers are infiltrated with lanthanum nitrate and ferric nitrate solution and subsequently sintered in air at high temperatures to produce the final LaFeO 3 hollow fibers. The samples have further distinctions in structure, morphology and crystallite size of the nanocrystallites, BET surface area, and the pore size distribution. Growth mechanism of LaFeO 3 hollow fibers was proposed. Furthermore, gas sensors were fabricated and an investigation of CO sensing properties has been conducted. Compared with LaFeO 3 particles, the hollow fibers display much better CO sensing properties, which is mainly due to the increasing of active surface area and gas diffusion.

Synthesis of α-Fe2O3 nano powder by simple chemical method

A simple chemical method has been developed for the preparation of single phase α-Fe2O3 nanocrystalline powder with crystallite size ∼20 nm. Precursor powder was synthesised by reacting aqueous solutions of ferric nitrate and oxalic acid and then evaporating the resulting solution to dryness. The precursor was subsequently calcined in air for 2·30 h at different temperatures ranging from 250 to 450°C to obtain nanostructured α-Fe2O3 powder. The synthesised powder was characterised using thermogravimetric and differential scanning calorimetric analysis, X-ray diffraction, TEM, BET surface area measurement and SEM. DC electrical resistivity of the synthesised material was measured by the two probe method. The synthetic route described here provides a simple and cost effective method to produce single phase, α-Fe2O3 nanopowder at a comparatively low temperature of 450°C.