EPR spectra of impurity ions of Mn.sup.2+ (S = 5/2), Gd.sup.3+ (S = 7/2), and Cu.sup.2+ (S = 1/2) were found and investigated in addition to the intensive signals of axial centers of Cr.sup.4+ in the ...Li.sub.2CaSiO.sub.4 crystal. Manganese and gadolinium ions show spectra of tetragonal symmetry; copper ions show both spectra of axial and triclinic symmetry. Parameters of the spin Hamiltonians for the tetragonal centers were determined. Ions of Mn.sup.2+ and Gd.sup.3+ were shown to replace calcium ions with octahedral oxygen environment; copper ions are localized on lithium positions having tetrahedral environment. The reasons for appearing of triclinic Cu.sup.2+ centers are discussed.
In a Li.sub.2CaSiO.sub.4 crystal, tetragonal Cr.sup.4+ centers (electron configuration 3d.sup.2, spin S = 1) are identified and investigated by the ESR method at different frequencies. The magnitude ...of zero-field splitting is determined. An additional signal with a reverse phase is observed in the region, in which the positions of the two transitions of Cr.sup.4+ coincide. For an uncontrolled impurity of Mn.sup.2+ ions (S = I = 5/2), the parameters and localization of the spin Hamiltonian are determined.
Hexavalent chromium is a well-known highly toxic metal, considered a priority pollutant. Industrial sources of Cr(VI) include leather tanning, cooling tower blowdown, plating, electroplating, ...anodizing baths, rinse waters, etc. The most common method applied for chromate control is reduction of Cr(VI) to its trivalent form in acid (pH
∼
2.0) and subsequent hydroxide precipitation of Cr(III) by increasing the pH to ∼9.0–10.0 using lime. Existing overviews of chromium removal only cover selected technologies that have traditionally been used in chromium removal. Far less attention has been paid to adsorption. Herein, we provide the first review article that provides readers an overview of the sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation.
After an overview of chromium contamination is provided, more than 300 papers on chromium remediation using adsorption are discussed to provide recent information about the most widely used adsorbents applied for chromium remediation. Efforts to establish the adsorption mechanisms of Cr(III) and Cr(VI) on various adsorbents are reviewed. Chromium's impact environmental quality, sources of chromium pollution and toxicological/health effects is also briefly introduced. Interpretations of the surface interactions are offered. Particular attention is paid to comparing the sorption efficiency and capacities of commercially available activated carbons to other low cost alternatives, including an extensive table.
Chromium (Cr) contamination in soil is a growing concern in sustainable agricultural production and food safety. Remediation of Cr from contaminated soils is a challenging task which may not only ...help in sustaining agriculture but also in minimizing adverse environmental impacts. Pot culture experiments were performed with the application of varied concentration of Cr+6 to assess the Chromium accumulation potential of Lemongrass and to study the impact of toxic concentration of Cr+6 on morphological, physiological and biochemical parameters of the plant. The results showed an increasing accumulation trend of Chromium with increasing Chromium concentrations in both root and shoot of 60 days old Lemongrass plants, while the protein and chlorophyll contents decreased. Similarly, accumulation of Cr increased the levels of proline and antioxidant enzymes indicating the enhanced damage control activity. The potentiality of the plant with the capacity to accumulate and stabilize Cr compound in Cr contaminated soil by phytoremediation process has been explored in the present investigation.
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•The degree of toxicity using varying concentrations of Cr+6 on growing Lemongrass.•Phytoaccumulation ability of Lemongrass with reference to tolerance indices.•Severity of Chromium toxicity stress on morphological, physiological and biochemical lesions.•Chromium bioavailability in plants.
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•WGS of strain ISTPL4 reveals presence of Cr reductase and other candidate of genes.•Freundlich and IPD isotherm model suggests no monolayer formation till 500 ppm of Cr.•Immobilized ...enzyme on activated biochar with calcite showed 99% removal of the Cr.•Toxicity of Cr (VI) was evaluated by MTT assay on HepG2 cell line.
The current study presents a comprehensive analysis of the potential of actinobacterium Zhihengliuella sp. ISTPL4 and different composite materials for the removal of hexavalent chromium Cr (VI). Genome analysis of strain indicated the presence of several oxidoreductases which includes chromate reductase, nitrate reductase, thioredoxin, superoxide dismutase and hydrogenase are other major candidate genes. Catalytic calcite-based bio-composite material was absorbed on biochar had highest Cr removal efficiency. The main mechanism involved in Cr biosorption by this strain was explained by the Langmuir isotherm model; under equilibrium conditions the maximum adsorption was observed 49 ± 0.3 mgg−1. Kinetic studies showed that biosorption of Cr (VI) by this strain was a rate-limiting step and followed a pseudo-second-order kinetics (R2 = 0.99). SEM analysis is in line with EDX result indicating highest Cr removal by calcined biochar. MTT assay shown that the bacteria successfully convert toxic Cr (VI) to comparatively less toxic form such as Cr (III).
Invited for the cover of this issue is the group of Peter Coburger at the Technical University of Munich. The image, painted by Dr. Christoph Selg, depicts the bonding relationships in a biradicaloid ...chromium complex as a staircase, with the people symbolizing the two‐way flow of electrons between the ligand and the metal. Read the full text of the article at 10.1002/chem.202302970.
“We were delighted to successfully obtain the phosphonium‐substituted diphosphaindenylide PPI, which demonstrated excellent π‐acceptor behavior.” This and more about the story behind the front cover can be found in the article at 10.1002/chem.202302970).
Although recent studies have shown that chromium (as the trivalent ion) is not an essential trace element, it has been demonstrated to generate beneficial effects at pharmacologically relevant doses ...on insulin sensitivity and cholesterol levels of rodent models of insulin insensitivity, including models of type 2 diabetes. The mode of action of Cr(III) at a molecular level is still an area of active debate; however, the movement of Cr(III) in the body, particularly in response to changes in insulin concentration, suggests that Cr(III) could act as a second messenger, amplifying insulin signaling. The evidence for the pharmacological mechanism of Cr(III)’s ability to increase insulin sensitivity by acting as a second messenger is reviewed, and proposals for testing this hypothesis are described.
In this study, the toxicity of hexavalent chromium Cr(VI) reduced by citric acid in ice was measured using representative aquatic model invertebrates (i.e., rotifer, water flea, amphipod, and ...polychaete) and a vertebrate (zebrafish) by analyzing short- and/or long-term endpoints that are frequently applied to each animal. Cr(VI) reduction in the presence of citric acid was markedly enhanced in the ice phase compared to that in an aqueous solution through the freeze concentration effect. The highly concentrated Cr(VI) and citric acid in ice grain boundaries were also confirmed using in situ cryogenic confocal Raman spectroscopy. Overall, exposure to Cr(VI) resulted in higher acute and/or chronic effects on aquatic animals, such as drastic mortality, growth inhibition, and decrease in offspring number, whereas the animals were increasingly tolerant to Cr(VI) that was reduced in the ice phase. Sublethal concentrations of Cr(VI) significantly decreased the antioxidant capacity in the aquatic animals. However, when the same concentrations of Cr(VI) were reduced in ice, these treatments showed no modulation or increase in the antioxidant defense system. Taken together, our results suggest that Cr(VI) reduction into Cr(III) was successfully achieved in ice and that this methodology can decrease the actual toxicity of Cr(VI) in aquatic animals.
Summary
The history of chromium as an allergen goes back more than a century, and includes an interventional success with national legislation that led to significant changes in the epidemiology of ...chromium allergy in construction workers. The 2015 EU Leather Regulation once again put a focus on chromium allergy, emphasizing that the investigation of chromium allergy is still far from complete. Our review article on chromium focuses on the allergen's chemical properties, its potential exposure sources, and the allergen's interaction with the skin, and also provides an overview of the regulations, and analyses the epidemiological pattern between nations and across continents. We provide an update on the allergen from a dermatological point of view, and conclude that much still remains to be discovered about the allergen, and that continued surveillance of exposure sources and prevalence rates is necessary.
