Loss Of Chromium Research Articles

Strong yet ductile self-passivating W-10Cr alloy by laser powder bed fusion

Compared to pure tungsten, self-passivating tungsten alloys (SPTAs) for the future nuclear fusion armour are expected to offer a major safety guarantee in a loss-of-coolant accident (LOCA) event. Here we used laser powder bed fusion (LPBF) to print a self-passivating W-10Cr system. The main challenges for processing W-10Cr alloys are balling phenomena and chromium loss due to their melting point differences. After laser parameters optimizations, W-10Cr blocks with relatively dense and smooth surface were fabricated. As-built specimens exhibited an inhomogeneous microstructure with W-rich regions and Cr-rich ones. In the Cr-rich region, ultrafine equiaxed grains were obtained in view of Spinodal decomposition. Owing to the co-contribution of Spinodal decomposition and fine-grain structure, the compressive strength, fracture strain and Vickers hardness (HV0.005) of W-10Cr alloy reach 1451 MPa, 21.5% and 9.4 GPa, which are obviously superior to pure tungsten counterparts, with the improvement of 41%, 115% and 43%, respectively. Based on the indentation responses, as-measured indentation hardness followed typical indentation size effect (ISE). A higher contribution from elastically surface work in the early part of indentation is responsible for the hardening mechanism of W-10Cr alloy. Additionally, the strengthening and toughening mechanisms associated with improved properties are also discussed. The mechanistic insights into the deformation behavior have extensive implications for the development of additively manufactured SPTAs with exceptional mechanical properties.

Mapping the Accouterment Effects of Plasma Nitriding on AISI 316L in Biomedical Applications

The present study aimed to critique the corrosion resistance of plasma-nitrided films of AISI 316L stainless steel with regards to their biomedical applications. The plasma nitriding process improves austenitic stainless steel’s micro-hardness and corrosion resistance. Austenitic stainless steel was treated at a temperature of 470 °C for 12, 24, and 36 h, to observe the outcomes of plasma nitriding. The corresponding microstructure, microhardness, depth of the nitrided layer, and electrochemical parameters were systematically characterized. The corrosion resistance of the plasma-nitrided specimens was gauged using the weight loss method in simulated body fluids (Phosphate-buffered saline (PBS), saline water, and ringer solution) by static immersion for 9, 18, and 27 days. Optimization was catalogued using the Taguchi method L27 orthogonal array to determine the optimum combination of plasma nitriding time and immersion time in simulated body fluid. The material characterization showed that the corrosion resistance of the plasma-nitrided specimens improved with longer nitriding times by Tafel polarization curves. Microhardness was observed at 12, 24, and 36 h as 1060, 1150, and 1220 HV0.1. SEM, with an energy-dispersive X-ray analysis (EDS) used to characterize the surface before and after plasma nitriding testing. It was concluded that CrN, which precipitates during processing and contributes to the loss of chromium from the surrounding matrix and the onset of a corrosive environment, is the primary cause of this behaviour.

Process model for manufacturing 400 series stainless steel with purified CO2 as an auxiliary oxidant and realizing carbon cycle

To reduce the CO2 emission in the iron and steel industry, aid carbon neutralization, and promote the application of CO2 in stainless steel production, CO and CO2 in flue gas were separated and purified to recycle for the production. Further, a process model of smelting stainless steel with O2–CO2 mixed injection was established based on the theory of thermodynamics and kinetics. The model validation was conducted in a 70 ton-stainless steel smelting furnace. The model calculation showed that CO2 injection for smelting stainless steel can improve the reaction efficiency of various elements in molten steel and cause a temperature drop. However, the excessive CO partial pressure in the molten pool caused by injecting CO2 aggravated the oxidation loss of chromium and led to a sharp rise in the temperature of molten steel near the end of smelting. According to the guidance of the model, a carbon cycle process concept was designed to realize the internal circulation application of CO2 in stainless steel production, which improves stainless steel smelting efficiency and self-consumption of CO2 produced by smelting.

Loss of Chromium(III) From Mixed Cr(III), Fe(III) Serum Transferrins

Abstract Objectives Transferrin, Tf, the protein that transports iron as Fe(III) from the blood to the tissues via endocytosis, is believed to also transport chromium(III), Cr(III). Under physiological conditions, Tf binds and releases Cr(III) rapidly from Cr(III)2-Tf; however, the major form of Tf in the bloodstream is mono-ferric Tf. Given the low concentration of Cr(III) in the bloodstream, the form of Cr(III)-containing Tf that is transported is probably monochromic, monoferric-Tf (Cr(III), Fe(III)-Tf). Given that Tf has two specific metal-binding sites, one in both its C-terminal and the N-terminal lobe, two forms of Cr(III), Fe(III)-Tf can form. The loss of Cr(III) from both forms of Cr(III), Fe(III)-Tf has been examined for the first time. Methods Cr(III), Fe(III)-Tf with Cr(III) in the C-lobe was prepared by adding CrCl3 to N-lobe monoferric Tf in deionized H2O at pH 7.5 containing ∼20 mM bicarbonate. Cr(III), Fe(III)-Tf with Cr(III) in the N-lobe was prepared by adding 1 equivalent of Fe as ferrous ammonium sulfate to Cr(III)2-Tf in 0.1 M HEPES buffer solution with 25 mM bicarbonate at pH 7.4. To examine the release of Cr(III), the pH of solutions of Cr(III), Fe(III)-Tf were acidified from pH 7.4 to pH 5.5. After time intervals, aliquots were removed and frozen for analysis by electron paramagnetic resonance (EPR) spectroscopy, which can distinguish aquated Cr(III) and Cr(III) bound to each of the two metal binding sites of Tf. Results The acidification of solutions of Cr(III), Fe(III)-Tf's in 100 mM HEPES and 25 mM bicarbonate solution, pH 7.4 to pH 5.5 resulted in a rapid loss of Fe(III) followed by a slower loss of Cr(III). The loss of Cr(III) from the Cr(III), Fe(III)-Tf with Cr(III) in the C-lobe is about 4 times faster than that from the same site in Cr(III)2-Tf. For the other site, the Cr loss is about 28 times faster. Thus, having one site vacant from the loss of Fe(III) leads to faster loss of Cr(III) from both lobes, suggesting Cr(III) loss is cooperative. Conclusions Mixed-metal Cr(III), Fe(III) Tf's loose Cr(III) for both metal binding sites in similar fashions to Cr(III) losses from Cr(III)2-Tf. Cr(III) is probably transported as mixed Cr(III), Fe(III)-Tf's. Funding Sources The University of Alabama Bioinorganic Chemistry of Chromium Research Fund.

Experimental Study on Decarburization and Chromium Retention in Stainless Steel Smelting with CO2 as Alternative to N2

Reusing CO2 as a secondary resource in the steel industry is one of the research hotspots in recent years. Herein, O2–N2 and O2–CO2 are injected into Fe–C–Cr melt at 1823 K to study the effect of CO2 (as an alternative to N2) on decarburization and chromium loss in the argon–oxygen decarburization (AOD) stainless steel smelting process. The results show a higher decarburization rate and lower chromium loss with O2–CO2 injection compared with O2–N2 injection. CO2 injection helps oxidatively remove a part of carbon (C) in the melt. Simultaneously, the increase in CO partial pressure reduces the loss of Cr by CO2 oxidation to a measurable extent. In the middle–late stage of smelting, the corresponding content of C and Cr is relatively consistent with the trend of thermodynamic analysis. From the view of kinetics, CO2 injection increases the gas–metal interface area to improve the Cr formation rate in the melt, improving decarburization and chromium retention with the substitution of CO2 for N2. The research results herein provide a new direction for the development of the AOD process in the future and put forward a way of CO2 resource utilization.

Experimental Investigation of Similar & Dissimilar Joints on Stainless Steel with TIG & MIG Welded

Abstract: Now days, most of the structural fabrications possess welded joints that are produced using suitable welding technique. However, the joining of thick plates in a single pass welding is a cumbersome task to many fabricators. Likewise, the selection of welding technique, filler wire and welding condition for the similar and dissimilar welding of several metals is at the development stage. The similar and dissimilar metal joints of have been emerged as a structural material for various industrial applications which provides good combination of mechanical properties like strength, corrosion resistance with lower cost. Selections of joining process for such a material are difficult because of their physical and chemical properties. The stainless steel of similar and dissimilar material joints are very common structural applications joining of stainless steel is very critical because of carbon precipitation and loss of chromium leads to increase in porosity affects the quality of joint leads deteriorate strength. In the present study, stainless steel of grades 310 and 316 were welded by Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) welding with compound flux of 50 % SiO2 + 50 % TiO2 processes. The mechanical behavior like hardness, tensile strength and bending properties of similar and dissimilar metal joints were investigated. Keywords: Mechanical Properties, ATIG, MIG, SS310, SS316, Micro Structure.

Imipramine Accelerates Nonalcoholic Fatty Liver Disease, Renal Impairment, Diabetic Retinopathy, Insulin Resistance, and Urinary Chromium Loss in Obese Mice.

Imipramine is a tricyclic antidepressant that has been approved for treating depression and anxiety in patients and animals and that has relatively mild side effects. However, the mechanisms of imipramine-associated disruption to metabolism and negative hepatic, renal, and retinal effects are not well defined. In this study, we evaluated C57BL6/J mice subjected to a high-fat diet (HFD) to study imipramine’s influences on obesity, fatty liver scores, glucose homeostasis, hepatic damage, distribution of chromium, and retinal/renal impairments. Obese mice receiving imipramine treatment had higher body, epididymal fat pad, and liver weights; higher serum triglyceride, aspartate and alanine aminotransferase, creatinine, blood urea nitrogen, renal antioxidant enzyme, and hepatic triglyceride levels; higher daily food efficiency; and higher expression levels of a marker of fatty acid regulation in the liver compared with the controls also fed an HFD. Furthermore, the obese mice that received imipramine treatment exhibited insulin resistance, worse glucose intolerance, decreased glucose transporter 4 expression and Akt phosphorylation levels, and increased chromium loss through urine. In addition, the treatment group exhibited considerably greater liver damage and higher fatty liver scores, paralleling the increases in patatin-like phospholipid domain containing protein 3 and the mRNA levels of sterol regulatory element-binding protein 1 and fatty acid-binding protein 4. Retinal injury worsened in imipramine-treated mice; decreases in retinal cell layer organization and retinal thickness and increases in nuclear factor κB and inducible nitric oxide synthase levels were observed. We conclude that administration of imipramine may result in the exacerbation of nonalcoholic fatty liver disease, diabetes, diabetic retinopathy, and kidney injury.

Curcumin Improved Glucose Intolerance, Renal Injury, and Nonalcoholic Fatty Liver Disease and Decreased Chromium Loss through Urine in Obese Mice

Obesity-associated hyperglycemia underlies insulin resistance, glucose intolerance, and related metabolic disorders including type 2 diabetes, renal damage, and nonalcoholic fatty liver disease. Turmeric root is commonly used in Asia, and curcumin, one of its pharmacological components, can play a role in preventing and treating certain chronic physiological disorders. Accordingly, this study examined how high-fat diet (HFD)-induced hyperglycemia and hyperlipidemia are reduced by curcumin through changes in fatty liver scores, chromium distribution, and renal injury in mice. Relative to the control group, also fed an HFD, the curcumin group weighed less and had smaller adipocytes; it also had lower daily food efficiency, blood urea nitrogen and creatinine levels, serum alanine aminotransferase and aspartate aminotransferase levels, serum and hepatic triglyceride levels, and hepatic lipid regulation marker expression. The curcumin-treated obese group exhibited significantly lower fasting blood glucose, was less glucose intolerant, had higher Akt phosphorylation and glucose transporter 4 (GLUT4) expression, and had greater serum insulin levels. Moreover, the group showed renal damage with lower TNF-α expression along with more numerous renal antioxidative enzymes that included superoxide dismutase, glutathione peroxidase, and catalase. The liver histology of the curcumin-treated obese mice showed superior lipid infiltration and fewer FASN and PNPLA3 proteins in comparison with the control mice. Curcumin contributed to creating a positive chromium balance by decreasing the amount of chromium lost through urine, leading to the chromium mobilization needed to mitigate hyperglycemia. Thus, the results suggest that curcumin prevents HFD-induced glucose intolerance, kidney injury, and nonalcoholic fatty liver disease.

Clozapine Worsens Glucose Intolerance, Nonalcoholic Fatty Liver Disease, Kidney Damage, and Retinal Injury and Increases Renal Reactive Oxygen Species Production and Chromium Loss in Obese Mice.

Clozapine is widely employed in the treatment of schizophrenia. Compared with that of atypical first-generation antipsychotics, atypical second-generation antipsychotics such as clozapine have less severe side effects and may positively affect obesity and blood glucose level. However, no systematic study of clozapine’s adverse metabolic effects—such as changes in kidney and liver function, body weight, glucose and triglyceride levels, and retinopathy—was conducted. This research investigated how clozapine affects weight, the bodily distribution of chromium, liver damage, fatty liver scores, glucose homeostasis, renal impairment, and retinopathy in mice fed a high fat diet (HFD). We discovered that obese mice treated with clozapine gained more weight and had greater kidney, liver, and retroperitoneal and epididymal fat pad masses; higher daily food efficiency; higher serum or hepatic triglyceride, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, and creatinine levels; and higher hepatic lipid regulation marker expression than did the HFD-fed control mice. Furthermore, the clozapine group mice exhibited insulin resistance, poorer insulin sensitivity, greater glucose intolerance, and less Akt phosphorylation; their GLUT4 expression was lower, they had renal damage, more reactive oxygen species, and IL-1 expression, and, finally, their levels of antioxidative enzymes (superoxide dismutase, glutathione peroxidase, and catalase) were lower. Moreover, clozapine reduced the thickness of retinal cell layers and increased iNOS and NF-κB expression; a net negative chromium balance occurred because more chromium was excreted through urine, and this influenced chromium mobilization, which did not help overcome the hyperglycemia. Our clozapine group had considerably higher fatty liver scores, which was supported by the findings of lowered adiponectin protein levels and increased FASN protein, PNPLA3 protein, FABP4 mRNA, and SREBP1 mRNA levels. We conclude that clozapine can worsen nonalcoholic fatty liver disease, diabetes, and kidney and retinal injury. Therefore, long-term administration of clozapine warrants higher attention.

Selective Complex Precipitation for Ferro-Chrome Separation From Electroplating Sludge Leaching Solution.

In this paper, aiming at the problem of chrome-iron separation in electroplating sludge, the separation of ferrochrome by complexation and precipitation with benzoic acid as complexing agent is achieved. The optimal conditions consisted of a 1: 3 molar ratio of Fe3+: C6H5COOH, a reaction temperature of 30°C, a final pH of 2.5 and a reaction time of 2 min. The separation rate of the iron was 97.38% and the rate of loss of chromium was only 3.59%. The ferrochromium separation products were analyzed by XRD, fluorescence spectroscopy, infrared spectroscopy and H NMR Spectroscopy in order to study the mechanism of precipitation. The results showed that benzoic acid preferentially forms a complex with iron and iron benzoate precipitates with an increase pH. The iron benzoate crystals have a fine particle size, settle rapidly and are easy to filter. The separation of Cr 3+/Fe3+ was successful using our methodology.

Dephosphorisation of hot metal containing moderate amounts of chromium with CaO–FeO x –Cr2O3–CaF2 slag

ABSTRACT With the extensive use of low-grade Cr-containing ore, the dephosphorisation issue of hot metal containing moderate amounts (0.2%-1%) of chromium is gaining more and more attention. To achieve dephosphorisation and chromium retention, a series of experiments on the dephosphorisation of hot metal containing moderate amounts of chromium were carried out at 1723 K. In the experiments, the crystallisation performance of the slag with various CaO/Fe2O3 ratio and Cr2O3 content, as well as the transfer of phosphorus and chromium between slag and hot metal at 1723 K were investigated. The results show that the dephosphorisation process goes through four stages: melting and precipitation, dissolution of refractory, continual oxidation, and phase transition. With the increase of CaO/Fe2O3 ratio, the chromium loss decreases while the dephosphorisation ratio first increases and then decreases. The addition of Cr2O3 promotes the precipitation of Fe(Cr,Al)2O4, which inhibits the dephosphorisation and chromium loss.

Phase, Composition and Structure Changes of CoCrNi-Based Concentrated Alloys Resulting from High Temperature Oxidation.

In this work, CoCrNi, FeCoCrNi and CoCrFeMnNi concentrated alloys with a Y-Ti oxide particle dispersion were prepared by mechanical alloying and Spark Plasma Sintering. The alloy consists of an FCC Ni-based matrix with a Y-Ti oxide dispersion and additional phases of Cr23C6 and Cr2O3. The effect of Fe, Mn, and Y-Ti oxide particles on the formation of oxide scales and the composition of the adjacent CoCrNi and FeCoCrNi alloys was studied. It was found that alloys without Mn in their composition form a protective Cr2O3 scale. The Cr23C6 particles provide an alternative mechanism for balancing the chromium loss during the oxidation. Y and Ti from the oxide particles participate in the formation of the protective oxide scales. Fe promotes Y and especially Ti diffusion through the Cr2O3 scale, resulting in the formation of Ti-depleted regions in the alloy. The findings will serve for the further development of these new materials.

Mobility of aluminum and mineral elements between aluminum foil and bean cake (Moimoi) mediated by pH and salinity during cooking

The dependence of pH and salinity on the leaching of aluminum and allied metals from aluminum foil into bean cake during cooking was studied. Concentration of metals in the foil samples and prepared bean cake were determined using energy dispersive X-ray fluorescence and atomic absorption spectrophotometers respectively. Analysis of aluminum foil brands sold within the study area showed that they all contained aluminum, magnesium, iron, zinc, manganese, chromium and nickel with mean concentrations ranging between 972.45–977.10 g/kg, 16.21–19.84 g/kg, 2280–5710 mg/kg, 1140–1260 mg/kg, 400–410 mg/kg, 80–90 mg/kg and 480–540 mg/kg respectively. Maximum leaching of aluminum into bean cake wrapped in aluminum foil was observed in the saline bean paste followed by alkaline and acidic pastes. The increase in the concentration of iron and zinc in the bean cake samples indicated that these metals coleached with aluminum into the food during cooking. The loss of magnesium, nickel, manganese and chromium from the bean cakes after cooking suggested that demineralization of this food material occurred simultaneously with the leaching of aluminum, iron and zinc into it. The hazard quotient model indicated that all the metals that leached into the bean cake were at concentrations that could pose serious health risks to consumers.

In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718

In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

Complexation separation for vanadium and chromium by dithiocarbamate and its application in treatment of chromium–vanadium-bearing slag

Abstract A novel method for the separation and reclamation of vanadium and chromium from acidic solution was proposed. The principle for the separation is based on selective complexation. In specific, V(V) can be complexated by dithiocarbamate to form VO(R1R2NCS2)3 precipitate, leaving Cr(III) remained in the acidic solution. Then the reclamation of V and Cr from VO(R1R2NCS2)3 precipitate and Cr(III)-bearing solution can be reached by decomplexation and neutralization, respectively. The kinetics of the complexation reaction was studied. In addition, the precipitation ratio of vanadium reached 97% and the loss of chromium was less than 4% after process optimization. The complexing agent could be regenerated with a high ratio of 99.5%. The method was successfully applied to treating chromium–vanadium-bearing slag produced in conventional vanadium production industry. Vanadium and chromium could be extracted from the slag in the form of calcium vanadate and Cr2O3 product with a purity of over 98%.

Investigation of the bilayer region of metal vapor in a helium tungsten inert gas arc plasma on stainless steel by imaging spectroscopy

A blue bilayer region presents in a helium tungsten inert gas (TIG) arc plasma on stainless steel. The blue region indicates the presence of metal vapor. The spectral intensity distributions of metal vapors, including ions, in a steady state helium TIG arc plasma on stainless steel were experimentally investigated by imaging spectroscopy. The spectral intensity distributions of the ionized metal vapors were clearly observed in the arc plasma. The ionized metal vapor was affected by the electric field, which suggested that it was transported through the inside of the arc plasma to the tungsten cathode by cataphoresis. Chromium vapor was widely distributed in the arc plasma because more was generated and it was more easily ionized than iron vapor. As the arc plasma was cooled by the strong radiation heat loss of chromium, not only the chromium vapor spectral intensity distributions but also iron vapor spectral intensity distributions were observed near the center of the arc plasma. In both the iron and the chromium vapor, the metal atoms were observed at the arc fringe, and the metal ions were observed in the arc. A blue bilayer region was observed in the arc plasma because the temperature ranges in which the metal atoms and the metal ions strongly emit light are different.

Binding of Cr2-transferrin to Transferrin Receptor Enhances the Rate of Chromium Loss and Is Dependent on the Conformation of Transferrin (P24-053-19)

ObjectivesTransferrin, Tf, the protein transports iron from the blood to the tissues via endocytosis, is believed to also transport chromium(III), Cr(III). Recently, the release of Cr(III) from Tf has been postulated to be too slow for appreciable quantities of Cr(III) to be released during the lifetime of an endosome. The objective of this work was to measure the rate of Cr(III) release from human serum Tf as a function of Tf confirmation and as the transferrin-transferrin receptor (TfR) complex. MethodsCr(III) was added to apoTf in a buffered solution at pH 7.4 containing 25 mM bicarbonate at 37 °C. After time intervals, ultraviolet spectra were collected, or aliquots were removed and frozen for analysis by electron paramagnetic resonance (EPR) spectroscopy, which can distinguish free Cr(III) and Cr(III) bound to the two metal binding sites of Tf. To model the acidification of the endosome that triggers release of metal ions from Tf, the Cr(III)2-Tf solutions were acidified by the addition of hydrochloric acid to pH 4.5 or 5.5. At time intervals after acidification, samples were again analyzed by ultraviolet and EPR spectroscopies. Similar studies were performed in the presence of Tf receptor, which binds two equivalents of Cr(III)2-Tf. ResultsThe loss of Cr(III) from the two metal-binding sites of Tf occur at different rates. Different confirmations of the Cr2-Tf complex exist depending on the conditions of Cr2-Tf formation. The conformation that forms rapidly under physiological conditions loses Cr(III) faster than conformations that form over longer periods of time. Binding of Cr(III)2-Tf to TfR facilitates the release of Cr. ConclusionsThe conformation of Cr(III)2-transferrin that forms under physiological conditions when complexed with transferrin receptor can release Cr at physiologically significant rates consistent with transferrin serving as the major Cr(III) transport agent between the blood stream and tissues. Funding SourcesThe University of Alabama College of Arts and Sciences Research Award.

Remediation of the vanadium slag processing residue and recovery of the valuable elements

The vanadium slag processing residue (VSPR), which is a metallurgical waste produced during the vanadium extraction process from the vanadium titano-magnetite, exhibits potential environmental risk due to the toxicity of chromium in this residue. To remediate the VSPR and recover the valuable elements including iron, chromium, vanadium and titanium, a novel process, i.e., “carbothermic reduction”-“magnetic separation”-“sulfuric acid leaching”-“solvent extraction”, is proposed in this work. The transfer of iron, chromium, vanadium and titanium in the novel process was theoretically and experimentally analyzed. The results demonstrate that the iron oxide can be selectively reduced via the carbothermic reduction. To minimize the loss of chromium, vanadium, and titanium in the magnetic separation, the reduction temperature is suggested to be below 1100°C to inhibit the reduction of the chromium, vanadium, and titanium oxides in the spinel of (Fe,Mn)x(V,Cr,Ti)3-xO4. Iron was concentrated in the magnetic phase while chromium, vanadium and titanium were concentrated in the non-magnetic phase after carbothermic reduction and magnetic separation. With perchloric acid as oxidizer, the spinel of (Fe,Mn)x(V,Cr,Ti)3-xO4 in the non-magnetic phase was decomposed through sulfuric acid leaching at 160°C without the generation of hexavalent chromium, and the metal elements were effectively leached. The toxicity test shows that the leaching residue is harmless. Finally, iron, titanium, vanadium, chromium could be preliminarily separated via the solvent extraction by employing D2EHPA as the extraction agent.

Study of the Possibility of Obtaining Non-Decomposing Slag During Low-Carbon Ferrochrome Production

Methods are analyzed for stabilizing self-disintegrating slags in melting low-carbon ferrochrome, and the main reasons for breakdown are considered. Four methods are shown for stabilizing oxide melts of which a promising method for preventing breakdown under contemporary production conditions for chromium ferroalloys by mixing melts is a reduction in the content of dicalcium silicate with a reduction in the CaO/SiO2 ratio in oxide melt to a value of less than 1.4. However a reduction in CaO/SiO2 slag basicity to 1.33 is demonstrated by experiment (during melting low-carbon ferrochrome containing not less than 5% Si). However, according to the specifications of GOST 4757–91 and the international standard ISO 5448-81 the silicon content in low-carbon ferrochrome should not exceed 1.5%, in view of which the silicothermal process for process for preparing ferrochrome by a mixing method should be separated into two stages. The first stage is preparation of siliceous semiproduct (low-carbon ferrochrome containing Si ≈ 5%) and non-disintegrating slag with reduced basicity (CaO/SiO2 = 1.3–1.4). The second stage is refining the semiproduct with respect to silicon with preparation of highly basic slag (CaO/SiO2 = 1.8–1.9) and ferrochrome with the required silicon content (less than 1.5%). The possibility of obtaining a non-disintegrating slag during melting low-carbon ferrochrome with subsequent processing into building rubble will make it possible to improve the ecological situation in the vicinity of ferroalloy enterprises, to reduce slag dump and adjacent territory contamination and dust content, and also to reduce the amount of slag, loss of chromium, and to increase productivity of the process with a reduction in specific consumption of lime and electrical energy.

Assessment of alternative adsorption models and global sensitivity analysis to characterize hexavalent chromium loss from soil to surface runoff

AbstractWe investigate our ability to assess transfer of hexavalent chromium, Cr(VI), from the soil to surface runoff by considering the effect of coupling diverse adsorption models with a two‐layer solute transfer model. Our analyses are grounded on a set of two experiments associated with soils characterized by diverse particle size distributions. Our study is motivated by the observation that Cr(VI) is receiving much attention for the assessment of environmental risks due to its high solubility, mobility, and toxicological significance. Adsorption of Cr(VI) is considered to be at equilibrium in the mixing layer under our experimental conditions. Four adsorption models, that is, the Langmuir, Freundlich, Temkin, and linear models, constitute our set of alternative (competing) mathematical formulations. Experimental results reveal that the soil samples characterized by the finest grain sizes are associated with the highest release of Cr(VI) to runoff. We compare the relative abilities of the four models to interpret experimental results through maximum likelihood model calibration and four model identification criteria (i.e., the Akaike information criteria [AIC and AICC] and the Bayesian and Kashyap information criteria). Our study results enable us to rank the tested models on the basis of a set of posterior weights assigned to each of them. A classical variance‐based global sensitivity analysis is then performed to assess the relative importance of the uncertain parameters associated with each of the models considered, within subregions of the parameter space. In this context, the modelling strategy resulting from coupling the Langmuir isotherm with a two‐layer solute transfer model is then evaluated as the most skilful for the overall interpretation of both sets of experiments. Our results document that (a) the depth of the mixing layer is the most influential factor for all models tested, with the exception of the Freundlich isotherm, and (b) the total sensitivity of the adsorption parameters varies in time, with a trend to increase as time progresses for all of the models. These results suggest that adsorption has a significant effect on the uncertainty associated with the release of Cr(VI) from the soil to the surface runoff component.