Crystallization Of Iron Research Articles

Organics removal and in-situ granule activated carbon regeneration in FBR-Fenton/GAC process for reverse osmosis concentrate treatment

Fluidized bed reactor Fenton (FBR-Fenton) process was adopted for reverse osmosis concentrate (ROC) treatment with three types of carriers, including sand, zeolite and granular activated carbon (GAC). Adsorption studies demonstrated that GAC achieved the best adsorption performance (maximum COD removal of 78% in 15 h) among the three carriers, and the adsorption of ROC organic matters followed a two-stage adsorption model. Fenton oxidations were carried out in three fluidized beds after column saturation, and FBR-Fenton/GAC process achieved highest COD removal (72%) and most BOD5/COD ratio enhancement (from 0.03 to 0.3) in ROC. Long-term operation data demonstrated good performance stability of GAC as the carrier. In addition, GAC fluidized bed obtained highest total iron removal rate via iron crystallization process. Continuous in-situ GAC regeneration with more than 90% recoveries of surface area, pore volume and adsorption capacity were observed along the ROC treatment with FBR-Fenton/GAC process. Mechanism studies revealed that better COD removal performance in FBR-Fenton/GAC process was attributed to the combining effects of homogenous Fenton reaction, GAC adsorption and GAC/H2O2 catalytic reaction.

Recovery of magnetite from fluidized-bed homogeneous crystallization of iron-containing solution as photocatalyst for Fenton-like degradation of RB5 azo dye under UVA irradiation

Iron recovery from wastewater as magnetite (Fe3O4) pellets was performed in a fluidized-bed homogeneous crystallization (FBHC) process. The catalytic effectiveness of magnetite in the heterogeneous degradation of RB5 azo dye was evaluated. The key parameters of FBHC, including effluent pH, cross-section loading (L, kg/m2.h), initial iron concentration ([Fe(II)], mg/L), and inlet supersaturation (S), were optimized to maximize the total iron removal (TR, %) and crystallization ratio (CR, %) from a fluidized-bed reactor. Under the conditions of pH = 8.5–9.5 and [Fe(II)]in = 100 – 500 mg/L, the TR and CR values reached 99% and 77%, respectively. The magnetization and coercivity of the recovered Fe3O4 pellets were analyzed to confirm the magnetic characteristic. A Fenton-like degradation of RB5 azo dye was activated using the Fe3O4 pellets under UVA irradiation, pH = 2.75 – 3.0, initial peroxide concentration of 10 mM, and catalyst loading of 2 g/L. The efficiencies of decolorization and mineralization reached about 98 – 99% and 60 – 68%, respectively. FBHC method benefited the recovery of high-purity metal oxides and the production of a low quantity of sludge. Magnetic pellets transformed from the dissolved iron in wastewater were promising materials to reuse as a photochemical reactant for organic pollutant degradation.

Phase and dimensional stability of volcanic ash-based phosphate inorganic polymers at elevated temperatures

Phosphate geopolymers are part of chemically bonded phosphate cements obtained from an aluminosilicate and phosphate solution. Their structure consisting of phosphate bonds makes them suitable for use as refractory material. This study deals with the influence of phosphoric acid concentration (6, 8 and 10 mol/L) on the stability of volcanic ash-based phosphate geopolymers exposed to 100, 600 and 1000 °C. The results reveal that the onset of crystallization is about 600 °C with the formation of aluminum phosphate (V) and tridymite, then crystallization of iron (III) phosphate (V) and hematite at 1000 °C. The degree of crystallization of these phases increases with phosphoric acid concentration. The geopolymers obtained with 8 mol/L of phosphoric acid showed the best thermal stability at 1000 °C in terms of compressive strength change. The maximum thermal linear shrinkage recorded was 3%. The major phases of all geopolymers remain stable up to 1000 °C, after which the melting of phases happens.

Aluminium in compacted graphite iron

Compacted graphite was obtained using inmold technology. The effect of aluminium on the crystallization process, microstructure, ferrite microhardness, and hardness of compacted graphite iron was studied. The microscopic and diffraction tests were also performed, and the process of cast iron crystallization was also investigated. Results show that aluminium increases the temperature of the eutectic transformation as well as the transformation temperature in the solid state. It is found that aluminium is a graphite forming element in compacted graphite iron (CGI) at a concentration up to 2.4wt.%. When its concentration is higher than 3.1wt.%, aluminium causes the spheroidization of the carbides in eutectoid mixture. It is also demonstrated that in cast iron with an aluminium content higher than ~8wt.%, AlFe3C0.5 phase crystallizes from the liquid.

Effect of Antimony on Graphite Growth in Ductile Iron

Antimony is used in ductile cast iron melts to avoid graphite degenerations like exploded graphite and chunky graphite. However, the effect of Sb in the melt on the crystallization of ductile cast iron is still unknown, therefore the aim of our investigations. The current study presents thermodynamic calculations showing that at the beginning of the eutectic solidification, Mg3Sb2 is formed. Furthermore, the amount of Sb increases in the austenite and decreases in the remaining melt during solidification. An experiment was conducted, in which a higher amount of Sb than usual was added to a ductile iron melt. In the microstructure of the Sb-containing sample, a higher graphite precipitate count was measured than in the reference sample without Sb. The graphite spheroids of the Sb-containing sample show an almost perfect roundness and a very smooth surface. However, lamellar outgrowths from the graphite spheroids were also observed. Using scanning electron microscopy with energy-dispersive X-ray spectroscopy, it could be shown that Sb-containing phases have been formed, which are located in the pearlitic matrix and also in graphite spheroids. As a result of spectroscopic investigations, it can be assumed that Sb-containing phases act as nucleant for graphite nucleation. Further investigations by Auger electron spectroscopy showed that a thin layer of Sb at the interface between graphite and matrix has been formed. It seems that this layer constricts the diffusion of carbon to the spheroidal graphite and acts as a surfactant favoring a layer-by-layer growth of the graphite spheroids.

Solubility of carbon and nitrogen in a sulfur-bearing iron melt: Constraints for siderophile behavior at upper mantle conditions

Abstract Carbon solubility in a liquid iron alloy containing nitrogen and sulfur has been studied experimentally in a carbon-saturated Fe-C-N-S-B system at pressures of 5.5 and 7.8 GPa, temperatures of 1450 to 1800 °C, and oxygen fugacities from the IW buffer to log fO2 ΔIW-6 (ΔIW is the logarithmic difference between experimental fO2 and that imposed by the coexistence of iron and wüstite). Carbon saturation of Fe-rich melts at 5.5 and 7.8 GPa maintains crystallization of flaky graphite and diamond. Diamond containing 2100–2600 ppm N and 130–150 ppm B crystallizes in equilibrium with BN within the diamond stability field at 7.8 GPa and 1600 to 1800 °C, while graphite forms at other conditions. The solubility of carbon in the C-saturated metal melt free from nitrogen and sulfur is 6.2 wt% C at 7.8 GPa and 1600 °C and decreases markedly with increasing nitrogen. A 1450–1600 °C graphite-saturated iron melt with 6.2–8.8 wt% N can dissolve: 3.6–3.9 and 1.4–2.5 wt% C at 5.5 and 7.8 GPa, respectively. However, the melt equilibrated with boron nitride and containing 1–1.7 wt% sulfur and 500–780 ppm boron dissolves twice less nitrogen while the solubility of carbon remains relatively high (3.8–5.2 wt%). According to our estimates, nitrogen partitions between diamond and the iron melt rich in volatiles at DNDm/Met=0.013−0.024. The pressure increase in the Fe-C-N system affects iron affinity of N and C: it increases in nitrogen but decreases in carbon. The reduction of C solubility in a Fe-rich melt containing nitrogen and sulfur may have had important consequences in the case of imperfect equilibration between the core and the mantle during their separation in the early Earth history. The reduction of C solubility allowed C supersaturation of the liquid iron alloy and crystallization of graphite and diamond. The carbon phases could float in the segregated core liquid and contribute to the carbon budget of the overlying silicate magma ocean. Therefore, the process led to the formation of graphite and diamond, which were the oldest carbon phases in silicate mantle.

Crystallization of single and binary iron‐ and aluminum hydroxides affect phosphorus desorption

AbstractIn acidic soils, phosphorus availability is affected by its strong affinity for mineral surfaces, especially Fe‐ and Al‐hydroxides. Plant roots have developed adaptive strategies to enhance the availability of phosphorus, including producing and exuding low molecular weight organic acids with a high affinity for phosphorus that competes with high molecular weight organic ligands formed during humification and mineralization. The aim of this study was to characterize the kinetics and mechanism of phosphorus desorption from Fe‐ and Al‐hydroxides of variable crystallinity, as well as binary Fe:Al‐hydroxide mixtures. Long‐term desorption experiments (56 days) were conducted with CaCl2, CaSO4, citric acid, and humic acid as competitive sorptives. CaCl2 and CaSO4 were selected as general inorganic sorptives and citric and humic acids were selected as organic ligands produced by organisms in the rhizosphere or following humification. The cumulative phosphorus desorption increased following the order CaCl2 < CaSO4 < humic acid < citric acid. Amorphous ferrihydrite and Fe‐rich Fe:Al‐hydroxides exhibited much less desorption when exposed to inorganic solutions than the crystalline and Al‐rich Fe:Al‐hydroxide mixtures. Models of the desorption data suggest phosphorus desorption with citric acid is diffusion‐controlled for ferrihydrite and Fe‐rich amorphous Fe:Al‐hydroxides. When humic acid was the sorptive, metal‐organic complexes accumulated in the solution. The results suggest organic compounds, especially citric acid, are more important for liberating phosphorus from Fe‐ and Al‐minerals than inorganic ions present in the soil solution.

CALCULATION OF CRYSTALLIZATION INDEX OF IRON AND MANGANESE UNDER TWO DIFFERENT SEDIMENTARY ENVIRONMENTS

In order to study the effect of sedimentary environments on the iron and manganese crystallization indices. Six districts were selected in al-Anbar governorate, including al-Baghdadi, Heet, Abu Tayban, Ramadi, Khalidiya and Falluja district. Two pedons were taken for each region and two different environments, one was for the sedimentary and the other was for desert laid in a vertical direction on Euphrates River. The total iron, manganese, available iron , manganese, Crystalline Free Iron, manganese Oxides, and Amorphous iron, manganese oxides have been measured as well as calculation of crystallization indices for iron and manganese. The Results showed that the over the crystallization of iron and manganese index in desert soils was superior sedimentary soil, as well as the iron crystallization index compared with the manganese crystallization index with a presence in pattern distribution in the desert soil compared to the sedimentary soil affected by the movement and the transfer of clay from the surface horizons to sub horizons. The percentage of organic matter was effected negatively on the percentage of crystallization index in the surface horizon and for all environments .

Influence of Ti and REE on Primary Crystallization and Wear Resistance of Chromium Cast Iron

The article presents the results of primary crystallization, wear resistance and SEM studies of chromium cast iron inoculated with ferrotitanium and rare earth elements as a mischmetal inoculating mixture. Thermal-derivative analysis method was used to conduct studies of primary crystallization in two types of testers, namely ATD-C and ATD-Is, reflecting two different cooling speeds. Wear resistance tests were performed with the use of modified pin-on-disk method on Tribotester 3-POD device, where the samples were moving in circular motion in metal-mineral friction system. Silicon carbide was used as a counter sample. The studies allowed to determine the influence of selected inoculants on the microstructure and wear resistance of the studied samples. All characteristic crystallization temperatures of samples casted into ATD-Is testers increased, as well as wear resistance of each inoculated samples compared to the non-inoculated sample. It was proven that TiC and REE compounds are effective inoculants for chromium carbides and that REE compounds can work as underlay for TiC crystallization.

Compositions Based on Nanosized Powders Carbides of Tungsten and Titanium, Obtained by the Method Self-Propagating High Temperature Synthesis for the Modification of Gray Cast Iron and Steel 110g13L

Iron-based alloys (steel and cast iron) are currently the main structural materials that provide a high level of mechanical and technological properties along with a relatively low cost. Increasing the performance characteristics (tensile strength, hardness, wear resistance, corrosion resistance and, ultimately, service life) of cast irons and steels is an urgent task. The quality of castings made of cast iron and steel depends on many technological parameters that affect the processes of crystallization of the melt (casting temperature, molding mixture, chemical composition, volume of casting, overheating of the metal during smelting, etc.). It is possible to improve the quality of castings without changing the technology of smelting and pouring metal into molds, if you learn how to manage the crystallization process. The laboratories have grown defect – free iron crystals with a tensile strength of more than 1000 kg/m2 (strength of carbon steel-40 kg/m2). Attempts to improve the mechanical properties by creating a single crystal are not justified, so you have to go the opposite way-to influence the crystallization process to get a lot of small crystals (grains), which also allows you to achieve high mechanical properties. The dependence of the strength characteristics on the grain size is well described by the law of Hall-Petch, according to which when the average grain size is reduced by 3...5 times there is an increase in the hardness of the material, with a further decrease in the average grain size by more than 10 times – an increase in plasticity. Influence on the processes of crystallization of iron and steel melts (change the size of metal grains, change the shape, size and distribution of graphite inclusions) can be the introduction of small additives substances (modifiers), not chemically interacting with the matrix. The use of modifiers to increase the rate of crystallization, reduce the structural heterogeneity of castings has good prospects. In addition, unlike doping, modification does not require a large number of expensive additives and, accordingly, slightly increases the final cost of production.

Spontaneous Resolution by Crystallization of an Octanuclear Iron(III) Complex Using Only Racemic Reagents

AbstractThe P and M enantiomers of the octanuclear [Fe8(μ4‐O)4(μ‐4‐Cl‐pz)12Cl4] complex, having T symmetry, were resolved by temporary substitution of chloride ligands by racemic 4‐sBu‐phenolates and subsequent crystallization, where the (S)‐ and (R)‐phenolates coordinate selectively to the M and P complexes, respectively. The complexes were characterized by circular dichroism analysis and X‐ray structure determination. This work constitutes a rare example of enantiomeric recognition resulting in spontaneous resolution upon crystallization.

Spontaneous Resolution by Crystallization of an Octanuclear Iron(III) Complex Using Only Racemic Reagents.

The P and M enantiomers of the octanuclear [Fe8 (μ4 -O)4 (μ-4-Cl-pz)12 Cl4 ] complex, having T symmetry, were resolved by temporary substitution of chloride ligands by racemic 4-s Bu-phenolates and subsequent crystallization, where the (S)- and (R)-phenolates coordinate selectively to the M and P complexes, respectively. The complexes were characterized by circular dichroism analysis and X-ray structure determination. This work constitutes a rare example of enantiomeric recognition resulting in spontaneous resolution upon crystallization.

Fenton oxidation treatment of recalcitrant dye in fluidized bed reactor: Role of SiO2 as carrier and its interaction with fenton's reagent

The role of SiO2 and its interaction with Fenton's reagent in fluidized bed Fenton (FBF) process were investigated in this work. Due to the inherent complexity of fluidized bed process, theoretical and experimental approaches were adopted in the study. Quantum computational approach was employed to predict the thermodynamic feasibilities of the possible interactions in the process. Experiments were conducted to study the effect of carrier loading and its contribution to the pollutant removal. FESEM/EDX and FTIR analyses were used to investigate the changes on the surface of the carriers due to interaction with Fenton's reagent. The results of quantum analysis show that with ΔG = −0.3263052 kcal/mol, complex formation between SiO2 and H2O2 is highly feasible. This is attributed to the siloxane bridge (Si–O–Si) of the SiO2 network. The experimental results revealed that carrier loading has a positive effect on the process and more than 23% of the initial COD can be removed through adsorption. The fluidization process resulted in 20% higher COD removal compared to the conventional Fenton oxidation. The results of both experimental and quantum computation indicated that besides iron crystallization on the carriers, other interactions are also possible in the FBF process. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

The factors on metallic iron crystallization from slag of direct coal liquefaction residue SiO2-Al2O3-Fe2O3-CaO-MgO-TiO2-Na2O-K2O system in the entrained flow gasification condition

The gasification of direct coal liquefaction residue (DCLR) enhances the overall economy of the direct coal liquefaction process. However, the DCLR ash is rich in iron due to pyrite as the catalyst during liquefaction. Coal blending plan with DCLR for gasification should consider the possibility of metallic iron crystallization and agglomeration ahead of suitable viscosity range. In this study, the iron behavior in the DCLR slag in the gasification condition was discussed by the thermodynamic modelling of SiO2-Al2O3-Fe2O3-CaO-MgO-TiO2-Na2O-K2O. Results show that the metallic iron forms only in the dry feed entrained flow gasifier for the high content of reducing gases. The metallic iron crystallizes when Fe2+ of the liquid phase fails to be stabilized by -Si-O. The competition reaction with -Si-O between Ca2+ and Fe2+ and the formation of calcium aluminum-silicate also contribute the metallic iron crystallization. In the gasification condition, the metallic iron crystallization can be inhibited by decreasing the iron content/α value (α = CaO/(SiO2 + Al2O3), mass ratio) or by increasing S/A (S/A = SiO2/Al2O3, mass ratio) of DCLR ash. Finally, the DCLR blends with 3.5 wt% sand/8.0 wt% mullite/50.0 wt% Dalai Nur coal/90.0 wt% Duolun coal is the feasible feedstock for pulverized coal gasifier, because the temperature of iron crystallization is below the tapping temperature of 1350 °C and the viscosity is less than 25 Pa·s.

Removal of iron as oxyhydroxide (FeOOH) from aqueous solution by fluidized-bed homogeneous crystallization

Abstract In this study, iron is removed from aqueous solution using a fluidized-bed crystallizer. Homogeneous oxyhydroxide pellets (FeOOH) were recovered at various value of pH, surface loading (L), and initial ferrous concentration to assess the treatability of iron-containing water. The optimal conditions for treating initial ferrous concentrations of 100–300 mg/L were L = 0.6 kg/m2/h (with 29 m/h of upflow velocity), a bed expansion of 50% and pH = 6.5 yielding the total iron removal (TR) of more than 99% and a corresponding iron crystallization ratio (CR) of 85%. X-ray diffractometry (XRD) revealed that the pellets consisted of a mixture of goethite (α-FeOOH) and lepidocrocite (γ-FeOOH). Scanning electron microscopy (SEM) yielded images of pellets of up to 1 mm in diameter, which were assembled from FeOOH flakes with thicknessess of 0.2–0.4 µm.

Heterogeneous fluidized-bed Fenton process: Factors affecting iron removal and tertiary treatment application

In this research, the factors affecting iron removal were determined for a fluidized-bed Fenton reactor using construction sand as the medium. Most of the particulate iron could be removed by the fluidized-bed Fenton process under optimum conditions. The surface area of the fluidized media available for iron crystallization via heterogeneous nucleation and hydraulic retention time were found to be the key factors controlling the iron removal efficiency. Bed expansion of 50% was sufficient for satisfactory iron removal. Further bed expansion did not provide any significant improvement, and could deteriorate the iron removal performance through scouring effect and increase energy consumption. Formic acid, one of the carboxylic intermediates from organic pollutant oxidation with hydroxyl radicals, remarkably deteriorated the iron removal performance. This is because it not only increased iron solubility through complexation but also hindered heterogeneous nucleation of ferric hydroxide onto the fluidized material. Therefore, in terms of iron removal, the fluidized-bed Fenton process should be applied to treat low-strength wastewater or to serve as a polishing unit to limit the formation of Fe3+-chelating intermediates. As a tertiary treatment unit, the fluidized-bed Fenton reactor could successfully and consistently reduce the COD and color of secondary effluents from pulp and paper mills to below the new and more stringent standards of 120 mg/L and 300 ADMI, respectively. Depending on the water characteristics, total iron removal of 53–81% could be achieved at the optimum retention time.

Microscopic study on the concretion of ceramics in the "Nanhai I" shipwreck of China, Southern Song Dynasty (1,127-1,279 A.D.).

"Nanhai I" shipwreck of China Southern Song Dynasty is the oldest and the most integrally preserved shipwreck in the world. The related conservation and archeological research have caught great attention of different experts all over the world. In this study, different types of concretion covered on the surface of the ceramics in "Nanhai I" shipwreck were analyzed by X-ray diffractometer, micro-Raman spectrometer, and scanning electron microscope equipped with energy dispersive spectroscopy. Based on the analyses, we found that the grey concretion was mainly composed of quartz, aragonite, and calcite while the reddish concretion was mainly composed of pyrite and quartz. Our study indicated that the formation process of the grey concretion probably included the crystallization and transformation of aragonite, while the corrosion of iron implements and crystallization of pyrite were highly involved in the formation of reddish concretion.

Silicon effect on the formation of graphite inclusions in gray cast iron

Using conventional and high-temperature metallography, micro-X-ray spectroscopy and mass spectral analyzes, as well as the petrographic method, the study explores the effect of silicon on the morphology of graphite inclusions in gray cast irons.So far, the role of silicon in the theory of graphite formation during the crystallization of cast irons remains unclear. Therefore, the disclosure of the mechanism of the influence of silicon on the formation of graphite inclusions can help fully control the structure and properties of cast iron castings and develop optimal technological processes for their production.It has been established that the reaction in the silicon interaction with carbon monoxide in iron-carbon alloys, leading to the formation of a surface-active silicon monoxide, is caused by the temperature and physicochemical conditions of the melt. In gray cast iron, the rate and intensity of the course of this reaction have a direct effect on the morphology of lamellar graphite. The study has revealed four morphological forms of primary graphite (rosette, rectilinear-plate, ramiform, and vermicular), formed in various physicochemical conditions of the crystallization of gray cast iron

Influence of Boron on Crystallization and Microstructure of Ductile Cast Iron

AbstractThe objective of the research was to determine the influence of boron on the crystallization process and microstructure of ductile cast iron. In the case of ductile cast iron it is a vital issue because even as little as trace presence of boron changes the properties of ductile cast iron in a significant way. With the use of a new ATD-4 (TDA) tester and CRYSTALDIGRPAH converter it was possible to measure the crystallization process parameters of the same alloy with four different contents of boron in one mould. Four samples with different boron contents were extracted, their microhardness was measured and quantitative analysis of microstructure was conducted. Obtained results allowed to state that with increasing content of boron the amount of graphite precipitates decreases, the amount of pearlite precipitates increases, the shape of graphite precipitates deteriorates and hardness increases. It is also planned to perform additional testings with boron contents between previously tested values.

Alignment of Amorphous Iron Oxide Clusters: A Non-Classical Mechanism for Magnetite Formation.

Despite numerous studies on the nucleation and crystallization of iron (oxyhydr)oxides, the roles of species developing during the early stages, especially primary clusters and intermediate amorphous particles, are still poorly understood. Herein, both ligand-free and ligand-protected amorphous iron oxide (AIO) clusters (<2 nm) were synthesized as precursors for magnetite formation. Thermal annealing can crystallize the clusters into magnetite particles, and AIO bulk phases with domains of pre-aligned clusters are found to be direct precursors to crystals, suggesting a non-classical aggregation-based pathway that differs from the reported oriented attachment or particle accretion mechanisms.