Role Of Chromium Research Articles

Assessing the effect of heavy metals on maize (Zea maysL.) growth and soil characteristics: plants-implications for phytoremediation

BackgroundHeavy metal pollution has become a global environmental issue. Heavy metals are contaminating the agro-soils, growing crops, and vegetables through different agricultural practices. In this study, besides the phytoremediation potential of maize, the role of chromium (Cr) and lead (Pb) on crop and soil health has been investigated.MethodsTwo maize varieties, Pak-Afgoi and Neelem, were grown under varying concentrations of Cr (50–300 ppm) and Pb (30–300 ppm) and different growth parametersi.e., seed germination, leaf size/number, stem girth, plant height, biomass, chlorophyll content, relative growth rate (RGR), and net assimilation rate (NAR) were studied under Cr and Pb stress. Likewise, the effect of metals was also assessed on different soil characteristics including soil texture, pH, EC, soil organic matter, urease activity and nutrients.ResultsStudied plant attributes were adversely affected by heavy metals toxicity. Affected values of RGR and NAR showed a linear correlation with affected growth and dry matter yield of maize. Heavy metals impacted different soil parameters including soil microbial performance and revealed a declining trend as compared to control soil. Maize varieties showed a significant phytoremediation potentiali.e., uptake of Cr and Pb was 33% and 22% in Pak-Afgoi, while Neelem showed 38% and 24% at 300 ppm, respectively. Data regarding metal translocation factor (TF), bioaccumulation factor (ACF), and biomagnification ratio (BMR) significantly revealed the potential of maize varieties in the removal of Cr and Pb metals from affected soils. However, Cr-accumulation was higher in shoots, and Pb accumulated in plant roots showed a differential behavior of metal translocation and affinity with the varieties. These maize varieties may be recommended for general cultivation in the Cr and Pb-contaminated areas.

The role of chromium on the structural, electronic and photoluminescence properties of alumina: Theoretical and experimental study

The role of chromium on the structural, electronic and photoluminescence properties of alumina: Theoretical and experimental study

Determination of trace metals in vegetables using ICP-MS

Determination of trace metals in vegetables using ICP-MS

Role of Chromium in Anomalous Behavior of the Passive Layer in Ni-Cr-Mo Alloys in 1 M HCl Solution

This work seeks to understand the underlying mechanism involved in the passivity of Ni-Cr-Mo alloys in a less concentrated HCl solution (1 M) by systematically varying contents of Cr and Mo solutes in model Ni-Cr-Mo alloys. Corrosion behavior was evaluated based on potentiodynamic polarization tests performed in conjunction with electrochemical impedance and x-ray photoelectron spectroscopies of passive films that formed on alloys during their exposure to the HCl solution. Results have shown that an increase in Mo alone is not sufficient to improve the corrosion resistance of the alloys at lower concentrations of HCl. Optimum concentrations of Cr and Mo solutes have been found to be in the vicinity of ∼17 wt% Cr and ∼19 wt% Mo for superior corrosion resistance of the alloys. This was attributed to the protection of the Cr2O3 layer as a consequence of the enrichment of Mo6+ ions in the passive film in 1 M HCl solution.

The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions

Chromium promotion of iron oxide based water-gas shift (WGS) catalysts prepared via co-precipitation/calcination was investigated. Mössbauer spectroscopy and XRD evidence that chromium is incorporated in the calcined hematite (α-Fe2O3) precursor irrespective of the doping level (0−12 wt.%). CO-TPR shows chromium delays the reduction of hematite and the active magnetite (Fe3O4) phase. WGS activity was evaluated under realistic conditions for 4 days. Enhanced CO conversion was observed with increased chromium doping. Mössbauer spectra indicate that chromium incorporates into octahedral sites of magnetite and prevents reduction of Fe3+ to Fe2+ during formation of the active phase, leading to an increased Fe3+/Fe2+ ratio in octahedral sites. The higher Fe3+/Fe2+ ratio did not affect the high CO conversion associated with the structural stabilization mechanism of Cr-doping. Interpretation of the Mössbauer spectra was supported by computational modelling of various chromium and vacancy-doped magnetite structures. The bulk structure of an in situ prepared chromium-doped high-temperature WGS catalyst is best described as a partially oxidized chromium-doped magnetite phase. No surface effects of Cr-doping were found.

Role of chromium in Cr–Fe oxide catalysts for high temperature water-gas shift reaction – A DFT study

Carcinogenic hexavalent Cr in the current iron oxide-based catalysts of high temperature water-gas shift (HT-WGS) reaction is great environmental concern. Interpreting the role of the Cr in this important industrial catalyst system is required. In the present study, we investigated substitution of Cr atoms into the most stable termination of Fe3O4 (111) slab surface by spin-polarized periodic DFT approach to comprehend the role of Cr. We applied the projector augmented-wave (PAW) method within the Perdew-Wang 1991 (PW91) form of the generalized gradient approximation (GGA) on the Vienna Ab-initio Simulation Package (VASP). The calculations point out that Cr atoms choose being below the surface FeO6 sites. Cr slightly affects the dissociative H2O adsorption. There is no effect on the CO adsorption. Oxygen vacancy is favored to form on the topmost layer with less vacancy formation energy. Substitution of Cr into the structure increases the oxygen vacancy formation energy. This indicates that Cr does not act as a chemical promoter and does not affect the catalytic activity positively, which is experimentally confirmed by the previous studies.

The Use of Chromium and Chromium (III) Oxide PVD Coatings to Resist the Corrosion Driven Coating Delamination of Organically Coated Packaging Steel

This paper describes a systematic study into the role of chromium and chromium (III) oxide thickness in preventing corrosion driven coating disbondment of organically coated packaging steel. A graded wedge of chromium and chromium (III) oxide is applied to steel using physical vapour deposition (PVD). A polyvinyl butyral (PVB) overcoat is applied and corrosion is initiated from an artificial defect using NaCl. Scanning Kelvin probe (SKP) potentiometry is used to monitor coating delamination. Wedge thickness variation allows for high throughput investigations into the effect of both metallic chromium and chromium (III) oxide thickness, on coating disbondment rate. A linear reciprocal relationship is observed between chromium metal thickness and disbondment rate. Increasing chromium (III) oxide thickness (applied over chromium metal) results in a decrease in delamination rate. This work highlights the ability of PVD to produce chromium/chromium (III) oxide corrosion resistant coatings to use as alternatives to hexavalent chromium-based systems.

The range of possible chromium III applications in medicine - the short review

Introduction: The key importance of chromium III in many physiological processes of human body, its influence on insulin regulation and glucose metabolism became an indicator to make an attempt to apply chromium III supplementation in disorders treatment. Mostly because diseases such as Alzheimer’s diseases, type 2 diabetes or polycystic ovary syndrome are caused by disorders of this process. Objective: The aim of this review was to present currently available knowledge on online database PubMed about an application, effectivity and the range of possible chromium III supplementation in medicine.Abbreviated description of the state of knowledge: Knowledge on the subject of the function of chromium III is constantly widening. Up to the year 2014 chromium was thought to be the very necessary root responsible for appropriate functioning of human body. Nowadays, the essential role of chromium III is questionated. It is the result of the lack of sufficient manifestation of chromium deficiency in humans and animals. The recent clinical trials have been distinctly indicated that the impact of chromium III should be considered rather as a pharmacological activity than an essential trace element for humans. Conclusions: The possible ways of chromium III supplementation in treatment of many marjory society diseases are still being searched. The recent clinical trials provided evidence both in favor and against the effectiveness and validity of chromium III supplementation. Studies finished with success are very promising but there is still a need for more updated researches.

The role of chromium in the corrosion performance of cobalt- and cobalt-nickel based hardmetal binders: A study centred on X-ray absorption microspectroscopy

The corrosion control of WC-Co type hardmetals is steadily gaining momentum for novel crucial applications in the Oil & Gas and food industries. The corrosion rate of the Co-based binder, and the extent to which coupling to WC speeds it up, are strongly influenced by alloying. In this paper, we investigate the impact of Cr on the corrosion-product film formation of Co- and CoNi based hardmetal binders in acidic, neutral and alkaline aqueous solutions. We centred our study on the role of Cr in driving the distribution of oxidized Co and Ni at the micrometre scale, thanks to synchrotron-based soft-X ray microspectroscopy. We have investigated morphochemical distributions for the following grades: Co96Cr4, Co48Ni48Cr4, Co50Cr50. Chemical-state mapping has been complemented by electrochemical measurements and metallographic observations. Amounts of Cr and Ni of ca. 50% notably increase the corrosion resistance in all ambients, with a stronger beneficial effect of the former element. 4% addition of Cr results in slight positive effects, with the exception of the CoNi system in alkaline ambient, that, together with Co50Cr50, outperforms the other grades. In all investigated alloy-ambient combinations, a continuous oxidized metal film grows, onto which micrometric island form of shape and dimensions that depend on the specific grade and aggressive conditions. Quantitative descriptors of chemical-state maps and their theoretical interpretation in terms of electrochemical phase-formation by oxy-hydroxide precipitation, allow to correlate the island patterns with the degree of pseudopassivation.

Assessment of health status in fiber glass workers: Role of chromium with biological antioxidants.

Objectives: The aim of study is to find out the role of chromium with biological antioxidant and how these can relate with the health of fiber glass workers. Study Design: Cross Sectional Study. Setting: Fiber glass industry Lahore. Period: July 2018 to Feb 2019. Material & Methods: Study was included the fifty workers of fiber glass industry with 4-5 years experience or time of exposure. A questionnaire was filled by each participant. Twenty individuals were taken as controls. Their blood sample was drawn to estimate the level of chromium and of biological antioxidants that include serum Catalase, Superoxide Dismutase, Glutathione and Malondialdehye. Results: Mean age of workers was 35 year with BMI 23.80 kg/m2. Their work duration in Fiber glass factory was 6-7 years. Levels of serum chromium and the biological antioxident was significantly high (P<0.001) in fiber glass workers as compared to the levels of these parameters of control. A positive weak correlation was observed between serum chromium and antioxidants MDA, SOD and catalase. On the other hand a moderate inverse correlation was observed between serum chromium and antioxidant GSH. Conclusion: It is concluded that high level of chromium in workers of fiber glass factory is responsible for increased levels of antioxidants in their body, which in long run may develop the diseases especially of respiratory tract.

Chromium (III) and chromium (VI) as important players in the induction of genotoxicity - current view.

Genotoxicity of chemical compounds is primarily associated with the interaction with DNA, formation of mutations, damage to chromosomes and initiating carcinogenesis processes. Currently, many compounds found in the environment are considered to be genotoxic agents, among them chromium: trivalent (III) and hexavalent (VI). The genotoxicity of hexavalent (VI) chromium has been proven in numerous epidemiological, in vitro and in vivo studies. The main source of Cr (VI) is environmental pollution associated with its use in various industries. On the other hand, the role of chromium (III) as a microelement is widely discussed. Due to its beneficial properties, associated with maintaining adequate blood glucose levels and supporting weight loss, it is widely used in the form of dietary supplements, often in doses exceeding the daily requirement. However, the safety of chromium compounds is disputable. Data about the mechanism of genotoxic effects are still incomplete. The aim of this review is to present the current knowledge about the induction of genotoxicity from two forms of chromium: trivalent (III) and hexavalent (VI). Chromium (VI) is a carcinogen with proven mutagenic and genotoxic effects, but this issue is still being investigated by scientists. In recent years, numerous studies have also been conducted on the genotoxic effect of chromium (III). Due to the still unexplained mechanism of the genotoxic action and incomplete knowledge about the transformation of chromium in the body, further research is needed, especially due to the growing popularity of Cr (III) compounds and their consumption in the form of dietary supplements and doubts as to the safety of its use, as well as environmental exposure to Cr (VI).

A joint experimental and theoretical study on the structural, electronic and optical properties of malayaite and Chromium‐doped malayaite structures as pigments

Ceramic pigments due to their properties of thermal stability and suitable optical characteristics are widely used in industries. Hence, the theoretical study of pigments based on density functional theory (DFT) is valuable to predict the structural, electronic, optical and especially colorimetric properties of them. We have synthesized the malayaite (CaSnSiO5) and chromium-doped malayaite with variable chromium concentration by the conventional ceramic route. Also, we have modeled these structures and performed DFT/TDDFT calculations by using the Quantum ESPRESSO package and YAMBO code. We studied the structural, electronic and optical properties of the structures. The role of chromium in the malayaite structure is determined by Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy methods. For the Cr-doped samples, it is shown that main XRD and Raman peaks have been shifted and it has explained the reason for the resonance-enhancement of vibrational modes of the samples. In the electronic property calculations, it is indicated that the gap and Fermi energies of the theoretical samples with increasing the doping concentration are decreased. In the optical properties section, UV–Vis spectroscopy and CIE L*a*b* colorimetry methods are used and the correspondence of the absorption spectra and colorimetric results for all samples is shown. Also, the gap energy of the experimental samples is compared to the theoretical samples. The results indicate the advantage of the DFT method for ceramic pigments.

The role of chromium during austempering of ductile iron

The present work analyzes the effect of small additions of chromium in the final structure of a commercial Austempered Ductile Iron (ADI). The study is made with emphasis on the effect of this element on the processing window. The results indicate that chromium addition decreases the stability of austenite promoting the martensitic transformation during cooling which increases the hardness and reduces the elongation. Likewise the increase in chromium addition delays the rate of transformation to ausferrite (stage I) and accelerates the stage II reaction promoting the bainite formation narrowing the optimal processing window. However, this effect is markedly reduced when the material is subjected to a long process of homogenization, prior to austempering process. The results of this work are discussed in terms of the degree of chromium segregation during solidification.

Design of alumina-forming austenitic stainless steel using genetic algorithms

Alumina-forming austenitic stainless steels (AFA-SSs) are candidates for high temperature applications to replace conventional stainless steels that form unstable chromium-oxide. In this work, a new AFA-SS composition was designed, through thermodynamic considerations, oxidation model calculations, and Genetic Algorithm-based optimization, which is expected to form alumina scale with only few number of alloying additions. The model incorporates thermodynamic stability of alumina with the kinetics of diffusion of aluminum and oxygen, and then considers the role of chromium as the third element, to predict alumina scale formability. In the present study, this model was utilized to design a new AFA-SS with minimum number of alloying additions. In addition, the oxidation behavior of the designed alloy was investigated at 800 °C to demonstrate its alumina forming capability and compared with a well-known alumina-forming steel. The cross-sections of the scales were studied using scanning electron microscopy and energy dispersive spectroscopy. The results confirmed the formation of the alumina layer in the designed alloy and validated the utility of the model and Genetic Algorithm-based optimization.

A meta-analysis of the effect of chromium supplementation on anthropometric indices of subjects with overweight or obesity.

The role of chromium as a weight loss agent remains questionable, and although previous meta-analyses findings have reported small reductions in body weight in individuals with overweight/obesity following chromium supplementation, there have been significant limitations with these findings. The objective of this meta-analysis was to evaluate the current evidence for the efficacy of oral chromium supplementation in individuals with overweight/obesity from randomized controlled trials. Studies were identified by a search of electronic databases from inception to November 2018 and combined and stratified analyses were used. Twenty-one trials from 19 studies were identified which met all inclusion criteria which were suitable for statistical pooling, and data from 1316 participants were included. Pooled analysis showed significant reductions in anthropometric indices associated with body composition; for weight loss (weighted mean difference [WMD]: -0.75 kg, 95% confidence interval [CI], -1.04, -0.45, P < 0.001), body mass index (WMD: -0.40, 95% CI, -0.66, -0.13, P = 0.003 and body fat percentage (WMD: -0.68%, 95% CI, -1.32, -0.03, P = 0.04) in individuals with overweight/obesity. No changes were detected in controls. Subgroup analysis showed significant improvements in weight loss and body fat percentage, particularly for study durations ≤12 weeks and doses ≤400 μg/d. Chromium supplementation was associated with some improvements in body composition in subjects with obesity/overweight. The effect size was medium and the clinical relevance of chromium as a weight loss aid remains uncertain. Further investigation from larger and well-designed randomized controlled studies, especially in patients with diabetes, is warranted.

The role of chromium and nickel on the thermal and mechanical properties of FeNiCr austenitic stainless steels under high pressure and temperature: a molecular dynamics study

ABSTRACTThe effect of Cr and Ni content on thermo-mechanical properties of FeNiCr austenitic stainless steel under ambient and high pressure and temperature were investigated by MD simulations. The FCC structure was selected as optimum structure for FeNiCr system based on obtained MD results from Bonny EAM potential and valid experimental results. The structural and mechanical properties of pure Fe, Ni, and Cr were also estimated based on this potential, indicating good agreement with experimental results. These properties were computed for four experimental case studies which showed less than 10% error. Moreover, the elastic constants of the Fe–(8–18)Ni–(18–25)Cr systems were estimated. Results showed that bulk modulus increases by increasing the Ni and Cr contents, which can be connected to the changes in bonding electrons. The thermal properties of FeNiCr were calculated in ambient and high pressure. Although thermo-mechanical properties confirm good agreement with experimental results at the ambient condition, however, they indicate that FeNiCr Bonny potential is not applicable at high pressure. In order to tackle this issue, a hybrid potential was used at high Pressure/Temperature. The results illustrate enhanced mechanical properties, increase of melting point and reduction of LTE in high pressure and deteriorated mechanical properties at high temperature.

On the Role of Chromium in Dynamic Transformation of Austenite

The effect of Chromium (Cr) on the dynamic transformation (DT) of austenite to ferrite at temperatures up to 430 °C above Ae3 was studied in a medium-carbon low-alloy steel. Hot compression tests were performed using Gleeble 3800® thermomechanical simulator followed by microstructural examinations using electron microscopy (FESEM-EBSD). Driving force calculation using austenite flow stress and ferrite yield stress on an inverse absolute temperature graph indicated that Cr increases the driving force for the transformation of austenite to ferrite; however, when the influence of stress and thermodynamic analysis are taken into account, it was observed that Cr increases the barrier energy and therefore, emerges as a barrier to the transformation. An analysis, based on lattice and pipe diffusion theories is presented that quantifies the role of stress on the diffusivity of Cr and is compared with other the main alloying elements such as C, Si and Mn and its impact, positive or negative, on the DT barrier energy. Finally, a comparison is made on the differential effects of temperature and stress on the initiation of DT in medium-carbon low-alloy steels.

Role of chromium in tungsten oxide (WO3) by microwave irradiation technique for sensor applications

Hydrated tungsten oxide (WO3·H2O)-based nanoparticles were synthesized using a simple and inexpensive facile microwave irradiation process, by doping chromium (2 wt%, 3 wt%, 5 wt% and 7 wt%) at 2.45 GHz with the power of 180 W for 10 min for gas sensor application. The resultant products were annealed at 600 °C at the ambient atmosphere in order to improve the crystallinity and to remove the impurities. The products were characterized by using powder XRD which confirmed the formation of orthorhombic and monoclinic structure of both as-prepared and annealed samples, respectively. Atomic force microscope shows the role of chromium in determining the surface morphology of the resultant products at microscopic level, Fourier transform infrared spectroscopic analysis confirmed the presence of essential functional groups formed through chemical bonds of the end products, room temperature UV–VIS DRS studies showed the optical behavior of the samples through emissions and band gap energy of the respective materials. Cyclic voltammetry study confirmed the suitability of the prepared chromium-doped tungsten oxide (WO3) materials through electrochemical property for photocatalytic and sensor applications.

Role of Chromium in the Formation of Phases in Mechanically Synthesized Alloys of Cementite Composition Alloyed with Chromium and Nickel

Phase transformations and aspects of alloying the phases of alloys of cementite composition, alloyed with chromium and nickel in the state immediately after mechanical synthesis and subsequent annealing, are studied. It is shown that cementite after mechanical synthesis is basically alloyed with chromium, while the amorphous phase is alloyed with chromium and nickel. Cementite produced upon the crystallization of the amorphous phase at Tann = 300°C is enriched with nickel. At medium temperatures of annealing, the cementite regions with the highest nickel content decompose to form para- or ferromagnetic austenite.

Revealing Molecular Level Indicators of Collagen Stability: Minimizing Chrome Usage in Leather Processing

Chromium(III) sulfate is extensively used in leather processing to stabilize the collagen molecules in hides and skins. Although its excess usage causes severe environmental pollution and health concerns, the role of chromium in stabilizing collagen still remains poorly understood. For the first time, by integrating a number of techniques, including real-time small-angle X-ray scattering, differential scanning calorimetry and natural cross-link analysis, we reveal crucial molecular-level indicators of collagen stability. The results indicate that collagen molecules achieve maximum molecular stability at concentrations as low as 1.8 wt % even if excess chromium (>3.7%) is introduced into the collagen matrix. At low concentrations (1.8% to 3.7%), the active amino acid residues are saturated via covalent bonding with chromium. Any excess chromium interacts purely non-covalently with the collagen molecule and, we propose, can be substituted by environment-friendly alternatives. Further, important natural cros...