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PdRuO2/PVP nanomaterial was synthesized using a straightforward method and characterized using advanced analytical methods such as TEM, XRD, XPS, elemental mapping and SEM. The synthesized PdRuO2/PVP nanomaterial was used as an ionophore in potentiometric sensor electrodes and successfully adapted to Cr3+ ion detection in a large number of aqueous samples. Several experimental parameters of the PdRuO2/PVP sensor such as potentiometric behavior, selectivity, repeatability, response time, pH, titration, and recovery in real samples were investigated. Potentiometric behavioral characteristics were performed in the concentration range 1 × 10−6–1.0 × 10−1 M. The repeated experiments performed six times showed that there was no deviation in the measurements. The limit of detection of the PdRuO2/PVP potentiometric sensor was very low with a value of 8.6 × 10−8 M. The potentiometric measurements showed that the synthesized PdRuO2/PVP ionophore was highly effective in detecting Cr3+ in a wide pH range of 2.0–8.0 and was found to have a shelf life of over 1 year. As a result, the synthesized PdRuO2/PVP electrode material was found to be highly selective, stable, and applicable for Cr3+ detection. [ABSTRACT FROM AUTHOR]

PdRuO2/PVP nanomaterial was synthesized using a straightforward method and characterized using advanced analytical methods such as TEM, XRD, XPS, elemental mapping and SEM. The synthesized PdRuO2/PVP nanomaterial was used as an ionophore in potentiometric sensor electrodes and successfully adapted to Cr3+ ion detection in a large number of aqueous samples. Several experimental parameters of the PdRuO2/PVP sensor such as potentiometric behavior, selectivity, repeatability, response time, pH, titration, and recovery in real samples were investigated. Potentiometric behavioral characteristics were performed in the concentration range 1 × 10−6–1.0 × 10−1 M. The repeated experiments performed six times showed that there was no deviation in the measurements. The limit of detection of the PdRuO2/PVP potentiometric sensor was very low with a value of 8.6 × 10−8 M. The potentiometric measurements showed that the synthesized PdRuO2/PVP ionophore was highly effective in detecting Cr3+ in a wide pH range of 2.0–8.0 and was found to have a shelf life of over 1 year. As a result, the synthesized PdRuO2/PVP electrode material was found to be highly selective, stable, and applicable for Cr3+ detection. [ABSTRACT FROM AUTHOR]

The reaction of Cr(NO3)3•9H2O with sodium cyclobutane-1,1-dicarboxylate Na2(cbdc) was studied and the conditions for the formation and crystallization of NaI—CrIII carboxylate complexes in various media were found. The synthesis in water followed by the use of EtOH as a crystallization medium enables the isolation of the compound {[Na3Cr(cbdc)3(EtOH)2(H2O)]•H2O}n (1). The 2D polymeric structure of this compound is composed of mononuclear [Cr(cbdc)3]3− units. The similar recrystallization from MeOH leads to the formation of the 2D polymer [CaNa2Cr2(cbdc)4(H2O)4(OMe)2(MeOH)2]n (2) containing binuclear [Cr2(cbdc)4(μ-OMe)2]4− units. A similar reaction in water in the presence of an excess of NaOH followed by the recrystallization from MeOH afforded crystals of the compounds {[Na4Cr2(cbdc)4(H2O)4(OH)(OMe)]•H2O}n (3) and {[Na4Cr2(cbdc)4(H2O)3(MeOH)(OH)(OMe)]•H2O}n (4) having similar 1D-polymeric structures. The reaction of Cr(NO3)3•9 H2O with Na2(cbdc) in MeOH followed by the benzene vapor diffusion into the reaction solution gave crystals of the compound {[Na3Cr(cbdc)3(MeOH)2]•0.5C6H6}n (5) having a 2D polymeric structure similar to that of compound 1. [ABSTRACT FROM AUTHOR]

This study investigated the genotoxic effects of chromium (Cr) in Hsd:ICR mice, considering factors such as oxidative state, apoptosis, exposure pathway, duration, pregnancy, and transplacental exposure. Genotoxicity was assessed using the erythrocytes' micronucleus (MN) assay, while apoptosis was evaluated in nucleated blood cells. The results showed that Cr(III) (CrK(SO4)2 and CrCl3) did not induce any marked genotoxic damage. However, Cr(VI) (CrO3, K2Cr2O7, Na2Cr2O7, and K2CrO4) produced varying degrees of genotoxicity, with CrO3 being the most potent. MN frequencies increased following 24‐h exposure, with a greater effect in male mice. Administering 20 mg/kg of CrO3 via gavage did not lead to significant effects compared to intraperitoneal administration. Short‐term oral treatment with a daily dose of 8.5 mg/kg for 49 days elevated MN levels only on day 14 after treatment. Pregnant female mice exposed to CrO3 on day 15 of pregnancy exhibited reduced genotoxic effects compared to nonpregnant animals. However, significant increases in MN levels were found in their fetuses starting 48 h after exposure. In summary, data indicate the potential genotoxic effects of Cr, with Cr(VI) forms inducing higher genotoxicity than Cr(III). These findings indicate that gender, exposure route, and pregnancy status might influence genotoxic responses to Cr. The study investigated the genotoxic effects of different chromium (Cr) forms in mice, focusing on apoptosis, exposure routes, duration, pregnancy, and transplacental exposure. Cr(III) did not cause genotoxic damage, while Cr(VI) produced varying degrees, CrO3 being the most potent. Male mice showed higher genotoxicity, and oral CrO3 administration had limited impact. Pregnant mice exhibited reduced effects, but their fetuses showed increased genotoxicity. Overall, Cr(VI) was more genotoxic, with responses dependent on gender, exposure route, and pregnancy status. [ABSTRACT FROM AUTHOR]

Background: Ionophores in the composition of potentiometric ion‐selective electrodes interact directly with the analyte ion and enable the determination of ionic species in various samples. Objectives: In this study, a novel ion‐selective electrode based on 5‐bromosalicylaldehyde thiosemicarbazone was developed for the selective determination of Cr3+ ions. Methods: The optimum electrode composition contained ionophore, poly (vinyl chloride) (PVC), bis (2‐ethylhexyl) sebacate (BEHS) and potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) in ratios of 4.0: 61.0: 34.0: 1.0 (mg), respectively. Potential measurements were performed using a computer‐controlled multi‐channel potentiometric measurement system. Results: The developed Cr (III)‐selective electrode exhibited a low detection limit of 3.96 × 10−6 M over a wide concentration range of 1.0 × 10−5 – 1.0 × 10−1 M (R2: 0.9979). The electrode exhibited good selectivity towards Cr3+ ions among metal ions with different charges. The chromium (III)‐selective electrode, which exhibited highly reproducible results in three different concentration ranges, also had a very fast response time of 5 s. Conclusions: The developed Cr (III)‐selective electrode were successfully performed in various beverage samples. As a result, the proposed electrode can be an alternative to other analytical methods in the analysis of Cr3+ ions. [ABSTRACT FROM AUTHOR]

In this study, the adsorption method was used to explore the removal of chromium(III) ion from chrome liquor that remained after chrome tanning in tannery and from the Buriganga River water as well. Both the natural and activated orange peel powder were used as adsorbents owing to its inexpensive and eco-friendly nature. In order to establish the best adsorption conditions, adsorbent concentration 5-40 g/L, pH 2-8 and contact time 30-120 min were investigated for Cr(III) removal from aqueous solutions using both natural orange peel and activated orange peel. Characterization of the adsorbents were done by using thermogravimetric analysis and Fouriertransform infrared spectroscopy analysis. The equations for both the Langmuir and Freundlich models were implemented to analyze the equilibrium data. Furthermore, the pseudo-first and second-order kinetic models were also utilized to evaluate the kinetic data. Both the natural and activated orange peel were found to remove a maximum of 77% and 96% of chromium(III) ion, respectively. [ABSTRACT FROM AUTHOR]

This study reports: a) the content of Ca, Cd, Co, Cr(III), Cr(VI), Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn in wastewater from metal industries and rivers that flow near the metal processing industries; b) the possibility of quantitative determination of Cr(III) and Cr(VI) in the presence of the following cations: Fe3+, Cu2+, Ca2+, Mg2+, Ni2+, Mn2+; and Zn2+ and anions Cl-, NO3-, and SO4 2-; c) speciation of Cr(III) and Cr(VI) on silica gel modified with Nb2O5 . Metals were determined by flame atomic absorption spectrometry, except for Na and K, which were determined by atomic emission spectrometry, and Cr(VI) by ultraviolet-visible spectrophotometry. When the concentration of cations is higher than Mg2+ (>25 mg/L), Ni2+ (>100 mg/L), Fe3+ (>250 mg/L), Zn2+ (>500 mg/L), and Mn2+ (>1000 mg/L), an error greater than 10 % is obtained in the measurement of Cr(III) . Silica gel modified with Nb2O5 can be considered as an effective solid phase extraction adsorbent for speciation of Cr species and simultaneous concentration of Cr(III). The proposed method was successfully applied to the speciation and determination of Cr(III) and Cr(VI) in the analyzed samples. The content of almost all analyzed metals has been below the permitted values for wastewaters. [ABSTRACT FROM AUTHOR]

Citrate-capped gold nanoparticle (GNP) was used as a ligand for chromium chelating, and chromium ions reaction led to GNP aggregation. The color change of GNP by aggregation in the presence of chromium is a simple and rapid colorimetric test for these ions in an aqueous solution. GNP capped citrate was prepared by the citrate method and characterized by TEM, and its particle size was 20 nm. Also, the surface plasmon resonance (SPR) peak was 520 nm. In the presence of chromium ions, the color of GNP at 520 nm was shifted to 650 nm because of aggregation to give a signal as a ratio of A650/520 more than one and proportional with chromium concentration directly. The optimum conditions were studied to obtain the high signal represented by the volume of GNP, reaction kinetic of A650 with time, selectivity, and interferences of Zn(II), Fe(III), Fe(II), Sn(II), Ni(II), Ca(II), Al(III), Sr(II), Cu(II), Mn(II), Co(II), Mg(II), Ag(I), and Pb(II) ions. The calibration curve is linear in the range of 100–500 ppb, and the regression was 0.9951 and applied on tap water chromium ions in the same range in the regression of 0.95. This method was simple, rapid reaction, consumed low volumes of sample, and had low detection limits. It can be recommended as a new method for chromium (III) detection in aqueous solutions.

The kinetics of oxidation of diaquadichloro(1,10‐phenanthroline)chromium(III) complex, [CrIII(phen)(H2O)2Cl2]+, by N‐bromosuccinimide (NBS) is biphasic. The first faster step involves the oxidation of Cr(III) to Cr(IV). The second slower step is due to the oxidation of Cr(IV) to Cr(V). The reaction product is isolated and characterized by electron spin resonance (ESR), IR, and elemental analysis. The chromium(V) product is consistent with the formula [CrV(phen)Cl2(O)]Br. The rate constants kf and ks, for the faster and the slower steps respectively, were obtained using an Origin 9.0 software program. Values of both kf and ks, varied linearly with [NBS] at constant reaction conditions. The effect of pH on the reaction rate is investigated over the pH (4.11–6.01) range at 25.0°C. The rate constants kf and ks increased with increasing pH. This is consistent with hydroxo forms of the chromium species being more reactive than the aqua forms. Chromium(III) complexes, more often than not, are inert. The oxidation of the Cr(III) complex to Cr(IV), most likely, proceeds by an outer sphere mechanism. Since chromium(IV) is labile the mechanism of its oxidation to chromium(V) is not certain. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

New bimetallic BaII-CrIII and trimetallic BaII-LnIII-CrIII coordination polymers have been synthesized and characterized by XRD. Compounds with LnIII = ErIII, YIII were found to demonstrate field-induced slow relaxation of magnetization. According to STA and DSC data, CrIII-containing binuclear building blocks [Cr 2 (OH) 2 (cpdc) 4 ]4− showed higher thermal stability than mononuclear units [Cr(cpdc) 3 ]3−. [Display omitted] The reaction of chromium(III) nitrate with Ba(cpdc) (H 2 cpdc = cyclopropane-1,1-dicarboxylic acid) in a ratio of 1:3 yielded a 1D coordination polymer {[Ba 2 Cr 2 (OH) 2 (cpdc) 4 (H 2 O) 8 ]·5H 2 O} n (1) formed by binuclear units [Cr 2 (OH) 2 (cpdc) 4 ]4− and a 3D polymer [Ba 2 Cr(cpdc) 3 (NO 3)(H 2 O) 6 ] n (2) constructed from tris-chelate blocks [Cr(cpdc) 3 ]3−. The addition of rare-earth metal nitrates (Cr:Ln = 1:2) in this reaction led to the formation of a series of trimetallic 3D coordination polymers {[Ba 3 Ln 2 Cr 4 (cpdc) 12 (H 2 O) 24 ]·8H 2 O} n (3 Ln , Ln = Gd, Tb, Dy, Ho, Er, Yb, Y), in whose structures tris-chelate fragments [Cr(cpdc) 3 ]3− are bound in layers by Ln3+ ions and, further, in a framework due to the coordination of Ba2+ ions. The crystal structures of 1 , 2 , and 3 Gd were determined by single-crystal X-ray diffraction (XRD), and isostructurality of all the compounds in the series 3 Ln was proved by powder X-ray diffraction (PXRD). DC -magnetic susceptibility measurements revealed weak ferromagnetic exchange interactions between Cr3+ ions in compound 1 (J = +0.74 cm−1). According to ac -magnetic susceptibility measurements, complexes 3 Er and 3 Y exhibit field-induced slow relaxation of magnetization. According to the data of simultaneous thermal analysis (STA) and differential scanning calorimetry (DSC) performed under Ar atmosphere, dehydration of the compounds obtained takes place in one (for 1 and 3 Gd) or three stages (for 2). The initial temperature of the organic part degradation process decreases when moving from compound 1 containing dimerized bis-chelate fragments [Cr 2 (OH) 2 (cpdc) 4 ]4− (330 °C) to compounds 2 (276 °C) and 3 Gd (261 °C) based on tris-chelate units [Cr(cpdc) 3 ]3−. [ABSTRACT FROM AUTHOR]

Stevia rebaudiana Bertoni and its glycosides are believed to exhibit several health-promoting properties. Recently, the mechanisms of the anti-diabetic effects of steviol glycosides (SG) have been the subject of intense research. The following study aims to evaluate the results of SG (stevioside (ST) and rebaudioside A (RA)) combined with L-arginine (L-Arg) and chromium(III) (CrIII) supplementation in streptozotocin- (STZ) induced mild type 2 diabetic rats fed a high-fat diet (HFD), with particular emphasis on carbohydrate and lipid metabolisms. The experiment was carried out on 110 male Wistar rats, 100 of which were fed an HFD to induce insulin resistance, followed by an intraperitoneal injection of streptozotocin to induce mild type 2 diabetes. After confirmation of hyperglycemia, the rats were divided into groups. Three groups served as controls: diabetic untreated, diabetic treated with metformin (300 mg/kg BW), and healthy group. Eight groups were fed an HFD enriched with stevioside or rebaudioside A (2500 mg/kg BW) combined with L-arginine (2000 or 4000 mg/kg BW) and Cr(III) (1 or 5 mg/kg BW) for six weeks. The results showed that supplementation with SG (ST and RA) combined with L-arg and Cr(III) could improve blood glucose levels in rats with mild type 2 diabetes. Furthermore, ST was more effective in improving blood glucose levels, insulin resistance indices, and very low-density lipoprotein cholesterol (VLDL-C) concentrations than RA. Although L-arg and Cr(III) supplementation did not independently affect most blood carbohydrate and lipid indices, it further improved some biomarkers when combined, particularly with ST. Notably, the beneficial impact of ST on the homeostatic model assessment–insulin resistance (HOMA-IR) and on the quantitative insulin-sensitivity check index (QUICKI) was strengthened when mixed with a high dose of L-arg, while its impact on antioxidant status was improved when combined with a high dose of Cr(III) in rats with mild type 2 diabetes. In conclusion, these results suggest that supplementary stevioside combined with L-arginine and Cr(III) has therapeutic potential for mild type 2 diabetes. However, further studies are warranted to confirm these effects in other experimental models and humans. [ABSTRACT FROM AUTHOR]

Chromium is recognised as a potent water pollutant by the WHO and thus it becomes pertinent to continuously monitor chromium levels in the waterbodies. Voltammetry, an electroanalytical technique, has been utilised for the detection of hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium in aqueous samples. Carbon Paste Electrode (CPE) modified using Sphingopyxis macrogoltabida SUK2c, an indigenous bacterial strain isolated from the water samples collected from Sukinda Valley, Odisha, India, was used as a working electrode in a typical three-electrode electrochemical cell. The developed biosensors were found to provide about 3.5 fold increase in cathodic peak current compared to the bare CPE for Cr(VI) ions. Using cyclic voltammetry (CV), the Lowest Limit of Detection (LLOD) of 1 × 10−4 M and 1 × 10−2 M for Cr(VI) and Cr(III) ions, respectively, were achieved with the biosensors. The LLOD was further improved to 1 × 10−9 M and 1 × 10−7 M for Cr(VI) and Cr(III) ions, respectively, adopting differential pulse cathodic stripping Vvoltammetry (DPCSV) technique employing the biosensors. The concentrations of Cr(VI) and Cr(III) ions present in water samples collected from Sukinda Valley, Odisha, India, could be determined using the biosensor. The plausible mechanisms involved in the detection of Cr(VI) and Cr(III) ions by the developed electrochemical biosensor are discussed. [ABSTRACT FROM AUTHOR]

In this study, Langmuir and dose-response models for chromium(III) ion biosorption from aqueous environment in a fixed-bed system are presented. Conservation and momentum equations for adsorption of metals ions are solved using computational fluid dynamics method with COMSOL multiphysics software. Simulation results for dose-response model show good agreement with experimental data. Also, a parametric study was conducted to investigate the effects of porosity, bed height, the input flow rate and the concentration of chromium(III) ion. Moreover, individual systems, two-component and three-component chromium, copper, lead and cadmium ions are studied. The results show that cadmium ion has the lowest, and copper ion has the highest penetration curve breakdown. [ABSTRACT FROM AUTHOR]

In this research work, the removal of chromium(III) ion (Cr3+) by raw materials such as zeolite (Z) and chert (CH) was investigated. The batch method was invested, using two concentrations in chromium(III) sulphate at 21.31mg/L and at 22mg/L in nitrate nonahydrate. In order to improve the porous structure, the specific surface area and the adsorbent capacity of these natural materials, a purification technique was undertaken, namely a chemical treatment of the used natural materials (zeolite and cherts) with NaCl was carried out. Thus, the obtained raw and purified materials were characterized through chemical analysis by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and liquid nitrogen adsorption-desorption analyses by measuring the specific surface area (BET method). The results demonstrated that zeolite (Z) and chert (CH) are good adsorbents and that the purified materials have a potential adsorbent to reduce the chromium concentration for a maximum adsorbed amount (Qads) of about 2.72mg/g and 2.85mg/g, respectively for purified zeolite and chert (Z-p and CH-p) in chromium(III) nitrate and about 2.83mg/g and 2.48mg/g, respectively for purified zeolite and chert (Z-p and CH-p) in chromium(III) sulphate. These results revealed that natural zeolite and chert hold great potential to remove cationic heavy metal species from industrial wastewater. The kinetics adsorption was also examined using pseudo-first-order and pseudo-second-order kinetics models. The adsorption kinetics was best described by the pseudo-second-order. [ABSTRACT FROM AUTHOR]

The crystal structure of the title complex, cis-[Cr(NCS)2(cyclam)]Br (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron X-ray data. The asymmetric unit contains one [Cr(NCS)2(cyclam)]+ cation and one bromide anion. The CrIII ion of the complex cation is coordinated by the four N atoms of the cyclam ligand and by two N-coordinating NCS groups in a cis arrangement, displaying a distorted octahedral coordination sphere. The Cr—N(cyclam) bond lengths are in the range 2.075 (3) to 2.081 (3) Å while the average Cr—N(NCS) bond length is 1.996 (16) Å. The macrocyclic cyclam moiety adopts the most stable cis-V conformation. The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N—H groups as donor groups, and the bromide anion and the S atom of one of the NCS ligands as acceptor groups.

In the present study, a new understanding of the application of biosurfactant, saponin, has been explored, over nitric and citric acids, as an electrolyte for the remediation of chromium from tannery sludge using the electrokinetic process. The interaction effects of independent variables [such as electrolyte molarity (M) and applied voltage (V)] and the output responses were studied using the statistical tool, response surface methodology. A significant correlation has been established between responses such as chromium removal, electrolytes consumption and power consumption for the selected independent variables. In terms of total chromium removal, saponin showed maximum effectiveness of 80.01% as compared to 72.37% of citric acid and 67.06% of nitric acid removal efficiency with lowest electrolyte consumption. The proposed mechanistic strategy for maximum removal efficiency with saponin over selected electrolytes can be attributed to the synchronized effects of micelles formation and sequential complexation along with adsorption of chromium ions during electromigration process. Also, the results derived from the sequential extraction analysis revealed that the saponin-treated electrokinetic process successfully increases the transformation rate of labile speciation (i.e., exchangeable and reducible fractions) to stable speciation (i.e., oxidizable and residual fractions) of chromium. This affirmed its lower risk of recontamination during its disposal. Thus, the removal efficiency and transformation of active metal fraction into a non-reactive fraction by saponin have been highly commended. [ABSTRACT FROM AUTHOR]

The cyanide groups of [Cr(CN)6]3−, [Mo(CN)8]3− and [W(CN)8]3− may be used to bridge several mono-nuclear transition metal-salen complexes to form different di-, tri-, tetra- hexa- and poly-nuclear complexes of different molecular architectures. The synthetic strategy of the complexes generally involves the formation of H2salen type ligands by the 1:2 condensation of the appropriate diamine and salicylaldehyde derivatives in appropriate solvent at the beginning, followed by the formation of mononuclear transition metal-salen complexes, which are finally connected by [Cr(CN)6]3−, [Mo(CN)8]3− and [W(CN)8]3− bridges to form poly-nuclear complexes. In some cases, however, transition metal-salen units were not isolated, but they have been used in situ to synthesize cyanide bridged poly-nuclear complexes. The magnetic properties of these complexes are interesting. This review represents an overview on the synthetic strategies, structures, magnetic properties of these complexes. It is noteworthy that only those complexes are considered in this review whose X-ray structures are available.

In the crystal structure of the title compound, (C5H6N)[Cr(NCS)4(C5H5N)2]·C5H5N, the CrIII ions are octahedrally coordinated by four N-bonding thiocyanate anions and two pyridine ligands into discrete negatively charged complexes, with the CrIII ion, as well as the two pyridine ligands, located on crystallographic mirror planes. The mean planes of the two pyridine ligands are rotated with respect to each other by 90°. Charge balance is achieved by one protonated pyridine molecule that is hydrogen bonded to one additional pyridine solvent molecule, with both located on crystallographic mirror planes and again rotated by exactly 90°. The pyridinium H atom was refined as disordered between both pyridine N atoms in a 70:30 ratio, leading to a linear N—H...N hydrogen bond. In the crystal, discrete complexes are linked by weak C—H...S hydrogen bonds into chains that are connected by additional C—H...S hydrogen bonding via the pyridinium cations and solvent molecules into layers and finally into a three-dimensional network.

The efficiency of Aspergillus tamarii (isolated from sludge of a textile industry) was investigated to remediate the synthetic solutions of reactive red 120 (RR120) dye and chromium(III) separately. Also, parallel studies were conducted on the bioremediation of binary system of chromium(III) and RR120 dye in different ratios. The study was conducted to find the potential of the A. tamarii for removing chromium(III) and color from solutions containing only chromium or only RR120 dye or both and the effect of RR120 and chromium on the growth of the strain were observed. Maximum dye removal 81 mg/L was observed from 100 mg/L RR120 dye solution at pH 5 up to 50 hours. Maximum chromium removal 88.3 mg/L was observed from 100 mg/L chromium (III) solution at pH 5 up to 50 hours. In previous studies, A. tamarii was used as a bioremediator for removing different chromium complex dyes. The removal of chromium(III) and color were compared from solutions of synthetic mixtures and chromium complex dyes. The response of bioremediation study was validated using multiple regression analysis.

This paper presents the results of research on a new method of chromium recovery from solid waste generated during the tanning of raw hides. In the first stage, the shredded mixture of useless leather scraps is decomposed through thermal pressure hydrolysis (TPH) in nitric acid in appropriate process conditions. Then, the liquid product of this process (hydrolysate) is fractionated using membrane separation techniques. The microfiltration (MF) process enables the initial purification of the hydrolysate by concentrating the organic matter. On the other hand, the nanofiltration (NF) process enables a three-fold concentration of total chromium in the pre-purified hydrolysate. The total chromium concentrate prepared in the above manner was successfully used in the model tanning processes. These processes were carried out on pickled bovine hides, using a mixture of a commercial chromium tanning agent and chromium concentrate after nanofiltration. The reference sample was bovine hide traditionally tanned with a commercial chromium tanning agent. Based on the results of the physical and chemical analyses, it was found that the properties of hides tanned using chromium recovered from waste are similar to those of hides tanned traditionally using a commercially available chromium tanning agent. The industrial implementation of the developed tannery waste valorisation technology would enable transition from a linear economy to circular economy.

The thermal stability of the oligomers obtained by using 2-chloro-2-propen-1-ol as the monomer has been studied. The oligomers were synthesized using chromium(III) and oxovanadium(IV) complexes as the catalysts after activation by modified methylaluminoxane (MMAO-12). The complexes used as the catalysts were polycarboxylate complex compounds of oxovanadium(IV) and chromium(III). The studies have been conducted by two methods: thermal gravimetry and differential scanning calorimetry. The obtained results allow to determine the glass transition temperatures and thermal stability of the oligomers depending on the central catalyst cation Cr3+ and V4+. [ABSTRACT FROM AUTHOR]

The kinetics of oxidation of [CrIIICl2(phen)(H2O)2]Cl⋅2H2O (phen = 1,10‐phenanthroline) by periodate {I(VII)} have been studied in aqueous acidic solutions. The oxidation product has been isolated and characterized by elemental analysis, IR, and ESR as [CrVCl2(phen)(O)]Cl⋅1.5H2O. Under pseudo–first‐order conditions, the reaction showed first‐order dependence on the initial Cr(III) complex concentration. At fixed reaction conditions, the dependence of kobs on [I(VII)] showed saturation kinetics. The rate constant, kobs, increased with increasing pH, indicating that the hydroxo form of the chromium(III) complex is the most reactive species. A plot of kobs([H+] + K1) versus [H+] is linear with an intercept, indicating that the reaction proceeds via two parallel pathways. One pathway is independent of [H+] and the other on [H+]–1. Since water is known to be a very weak bridging ligand, the pathway involving the aqua form of the complex, almost certainly, is bridged to periodate via the chloro ligand of the chromium(III) complex. The thermodynamic parameters of the processes involved are reported. A one‐step two‐electron transfer via an inner‐sphere mechanism has been assigned to the two pathways based on the form of the rate law [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present study, chromium(III) removal from aqueous solutions by a strong cationic resin (Amberlite IR120) and a weak cationic resin (Amberlite IRC86) was studied in batch experiments. In each case, the chromium exchange was examined by varying resin dosage, solution pH, contact time and initial chromium concentration. The obtained results show that the kinetics of chromium removal in the case of the two resins is rapid and follows the pseudo-second-order model. The chromium diffusion to IR120 resin can be described by either film diffusion or particles diffusion. In the case of IRC86, only film diffusion can be appropriate. At pH < 3.5, IR120 is significantly more efficient for Cr(III) removal than IRC86. The maximum exchange capacities determined by the Langmuir equation are 112 mg/g at pH 3 for IR120 and 22 mg/g at pH 4 for IRC86. [ABSTRACT FROM AUTHOR]

Stevia rebaudiana Bertoni and its glycosides are believed to exhibit several health-promoting properties. Recently, the mechanisms of the anti-diabetic effects of steviol glycosides (SG) have been the subject of intense research. The following study aims to evaluate the results of SG (stevioside (ST) and rebaudioside A (RA)) combined with L-arginine (L-Arg) and chromium(III) (CrIII) supplementation in streptozotocin- (STZ) induced mild type 2 diabetic rats fed a high-fat diet (HFD), with particular emphasis on carbohydrate and lipid metabolisms. The experiment was carried out on 110 male Wistar rats, 100 of which were fed an HFD to induce insulin resistance, followed by an intraperitoneal injection of streptozotocin to induce mild type 2 diabetes. After confirmation of hyperglycemia, the rats were divided into groups. Three groups served as controls: diabetic untreated, diabetic treated with metformin (300 mg/kg BW), and healthy group. Eight groups were fed an HFD enriched with stevioside or rebaudioside A (2500 mg/kg BW) combined with L-arginine (2000 or 4000 mg/kg BW) and Cr(III) (1 or 5 mg/kg BW) for six weeks. The results showed that supplementation with SG (ST and RA) combined with L-arg and Cr(III) could improve blood glucose levels in rats with mild type 2 diabetes. Furthermore, ST was more effective in improving blood glucose levels, insulin resistance indices, and very low-density lipoprotein cholesterol (VLDL-C) concentrations than RA. Although L-arg and Cr(III) supplementation did not independently affect most blood carbohydrate and lipid indices, it further improved some biomarkers when combined, particularly with ST. Notably, the beneficial impact of ST on the homeostatic model assessment–insulin resistance (HOMA-IR) and on the quantitative insulin-sensitivity check index (QUICKI) was strengthened when mixed with a high dose of L-arg, while its impact on antioxidant status was improved when combined with a high dose of Cr(III) in rats with mild type 2 diabetes. In conclusion, these results suggest that supplementary stevioside combined with L-arginine and Cr(III) has therapeutic potential for mild type 2 diabetes. However, further studies are warranted to confirm these effects in other experimental models and humans.

Addition of the potassium dichalcogenidodiphenylphosphinate salts, KE2PPh2 (E=S, Se), to either the THF solvate of vanadium(III) chloride or unsolvated chromium(III) chloride results in rapid ligand substitution and the formation of a series of closely‐related trivalent, neutral mononuclear complexes, M(E2PPh2)3 (M=V, Cr; E=S, Se), isolated in modest to good yield. The metal dichalcogenidophosphinate complexes reported herein were characterized by IR, UV‐vis, and 1H NMR spectroscopies, and their solid‐state molecular structures were determined by single‐crystal X‐ray crystallography. Importantly, the comparative analysis includes the structural and spectroscopic studies of two rare V(III) dithio‐ and diseleno‐phosphinate VE6 cores, as well as, two previously known CrE6 analogues. In the solid‐state the title complexes exhibit trigonal distortion from octahedral with torsion angles ranging from 43(2) to 50.3(6)° and structural parameters consistent with ligation of progressively 'softer' chalcogen‐donors. [ABSTRACT FROM AUTHOR]

The crystal structure of the title complex, cis-[Cr(NCS)2(cyclam)]Br (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron X-ray data. The asymmetric unit contains one [Cr(NCS)2(cyclam)]+ cation and one bromide anion. The CrIII ion of the complex cation is coordinated by the four N atoms of the cyclam ligand and by two N-coordinating NCS groups in a cis arrangement, displaying a distorted octahedral coordination sphere. The Cr--N(cyclam) bond lengths are in the range 2.075 (3) to 2.081 (3) Å while the average Cr--N(NCS) bond length is 1.996 (16) Å. The macrocyclic cyclam moiety adopts the most stable cis-V conformation. The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N--H groups as donor groups, and the bromide anion and the S atom of one of the NCS ligands as acceptor groups. [ABSTRACT FROM AUTHOR]

The reaction of Cr(NO3)3·9H2O with potassium cyclobutane-1,1-dicarboxylate (K2(Cbdc)) in 1 : 3 ratio was studied. It was shown that, depending on the reaction conditions and the solvents used for synthesis and crystallization, compounds of various compositions and structures can be isolated from the reaction system. Conducting the reaction in water followed by recrystallization from ethanol and methanol results in isolation of 2D polymeric complexes [KCr(Cbdc)2(H2O)2]n (I) and {[K4Cr2(OMe)2(Cbdc)4(MeOH)6]· MeOH}n (II), respectively. The addition of excess KOH to the same reaction mixture and recrystallization from alcohols gives rise to the crystals of 3D polymeric compound [K3Cr(Cbdc)3(H2O)2]n (III). Conducting the reaction in methanol followed by slow diffusion of diethyl ether affords complex [K3Cr(Cbdc)3(MeOH)2(H2O)2]n (IV) with a 2D polymeric structure. The crystal structures of compounds I–IV were determined by X-ray diffraction (CIF files CCDC nos. 2006090 (I), 2006109 (II), 2006116 (III), and 2 006 117 (IV)). [ABSTRACT FROM AUTHOR]

Chiral molecules are essential for the development of advanced technological applications in spintronic and photonic. The best systems should produce large circularly polarized luminescence (CPL) as estimated by their dissymmetry factor (glum), which can reach the maximum values of −2 ≤ glum ≤ 2 when either pure right- or left-handed polarized light is emitted after standard excitation. For matching this requirement, theoretical considerations indicate that optical transitions with large magnetic and weak electric transition dipole moments represent the holy grail of CPL. Because of their detrimental strong and allowed electric dipole transitions, popular chiral emissive organic molecules display generally moderate dissymmetry factors (10−5 ≤ glum ≤ 10−3). However, recent efforts in this field show that glum can be significantly enhanced when the chiral organic activators are part of chiral supramolecular assemblies or of liquid crystalline materials. At the other extreme, chiral EuIII- and SmIII-based complexes, which possess intra-shell parity-forbidden electric but allowed magnetic dipole transitions, have yielded the largest dissymmetry factor reported so far with glum ~ 1.38. Consequently, 4f-based metal complexes with strong CPL are currently the best candidates for potential technological applications. They however suffer from the need for highly pure samples and from considerable production costs. In this context, chiral earth-abundant and cheap d-block metal complexes benefit from a renewed interest according that their CPL signal can be optimized despite the larger covalency displayed by d-block cations compared with 4f-block analogs. This essay thus aims at providing a minimum overview of the theoretical aspects rationalizing circularly polarized luminescence and their exploitation for the design of chiral emissive metal complexes with strong CPL. Beyond the corroboration that f–f transitions are ideal candidates for generating large dissymmetry factors, a special attention is focused on the recent attempts to use chiral CrIII-based complexes that reach values of glum up to 0.2. This could pave the way for replacing high-cost rare earths with cheap transition metals for CPL applications.

In this work, a new solid phase extraction method for the determination of chromium species in water samples by electrothermal atomic absorption spectrometry was developed. For selective separation of Cr(III) ions under dynamic conditions, two ion imprinted polymers containing Cr(III)-1,10-phenanthroline complex (Cr(III)-phen) were prepared with the use of one (styrene, ST) or two (styrene and 4-vinylpyridine, ST-4VP) functional monomers. The physicochemical properties of those solid sorbents towards Cr(III) ions were studied and compared. It was found that Cr(III) ions were retained on the Cr(III)-phen-ST and Cr(III)-phen-ST-4VP polymers with high efficiency and repeatability (91.6% and 92.9%, RSD < 2%) from solutions at pH 4.5. The quantitative recovery of the analyte (91.7% and 93.9%, RSD < 4%) was obtained with 0.1 mol/L EDTA solution. The introduction of 4VP, an additional functional monomer, improved selectivity of the Cr(III)-phen-ST-4VP polymer towards Cr(III) ions in the presence of Cu(II), Mn(II) and Fe(III) ions, and slightly decreased the sorption capacity and stability of that polymer. The accuracy of procedures based on both polymeric sorbents was proved by analyzing the standard reference material of surface water SRM 1643e. The method using the Cr(III)-phen-ST polymer was applied for determining of Cr(III) ions in tap water and infusion of a green tea.

This study explored the possibility of using hydroxyapatite and its two modifications as sorbents to remove Cr(III) ions under different experimental conditions. The effect of pH (3-7), chromium concentration (10-100 mg L-1) and time (5-60 min) on adsorption was investigated. The Langmuir, Freundlich and Temkin adsorption models were applied to describe experimental data. Maximum adsorption capacity constituted 78.1 mg g-1 for hydroxyapatite treated with pluronic P123, 79.7 mg g-1 for hydroxyapatite and 134 mg g-1 for hydroxyapatite treated with pluronic F127 surfactant. The pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were used to describe the kinetics of the process. For all sorbents, the experimental data fitted very well the pseudo-second-order and intraparticle diffusion models. The obtained results showed the potential of synthesized sorbents to be used for Cr(III) removal from wastewater. [ABSTRACT FROM AUTHOR]

Regardless of its toxicity, chromium is an element that lives with humans due to its various uses, and while the toxic character of Cr(VI) is of wide knowledge, this element in its (III) oxidation state is also harmful, and this harmfulness increased by the risk of its potential oxidation to the (VI) oxidation state. Thus, there is a constant effort to find technologies that eliminated this Cr(III) from the different effluents in which it is present. In liquid solutions, it seems that adsorption is one of the most popular methods, and also the finding of adsorbents which eliminated Cr(III) most easily, most selectively and with better yields. The recovery of this element from the loaded adsorbent and the recycle of the adsorbent, are also two points that always, but this is not the real situation, must be taking into account. This manuscript reviewed the most recent advances (papers published in the 2019 year) about the use of adsorption, and adsorbents aimed at the recovery of Cr(III) from liquid solutions. [ABSTRACT FROM AUTHOR]

The calcium(II), iron(III) and chromium(III) alkyl-N-iminodiacetate systems have been studied in aqueous solution with respect to stability, acid–base properties and structure. The calcium(II) ion forms only one weak complex with methyl-N-iminodiacetic acid in water, K1 = 12.9 (2) mol–1⋅dm3, while iron(III) and chromium(III) form very stable complexes with alkyl-N-iminodiacetic acids. The calcium(II)–methyl-N-iminodiacetate complex is octahedral in the solid state with most probably water in the remaining positions giving a mean Ca–O bond distance of ca. 2.36 Å. The iron(III) alkyl-N-iminodiacetate complexes have low solubility due to a strong tendency to form polymeric structures. Depending on pH in the solution at their preparation, the degree of hydrolysis in the resulting compound(s) may differ. In the solid state, the polymeric iron(III) alkyl-N-iminodiacetate compounds seem to have the mean composition Fe2O(Cx-IDA)5; the mean Fe–O bond distances to the oxo group and the alkyl-N-iminodiacetate ligands are 1.92 and 2.02 Å, respectively. In these complexes the nitrogen atoms are bound at much longer bond distances, 0.1–0.2 Å, than the carboxylate oxygens. This distribution with short strong Fe–O bonds and much longer and weaker Fe–N bonds is also found in most other structurally characterized iron(III) carboxylated amine/polyamine complexes. The chromium(III) alkyl-N-iminodiacetate complexes are octahedral in both solution and solid state, and the low solubility of the solid compounds indicates a polymeric structure with the ligands bridging chromium(III) ions. Also, chromium(III) binds oxygen atoms in carboxylated amines at significantly shorter distance than the nitrogen stoms. The chromium(III) alkyl-N-iminodiacetate complexes display such slow kinetics at titration with strong base that the back-titration with strong acid shows completely different acid–base properties, thus the acid–base reactions are irreversible. [ABSTRACT FROM AUTHOR]

• Graphene nanosheet/δ-MnO 2 is used in the adsorption of Co(II) and Cr(III) from solution. • Optimum adsorption capacity for Co(II) and Cr(III) are 403.4 and 491.98 mg/g. • The whole adsorption process was investigated systematically. • Co(II) and Cr(III) have high removal abilities and fast kinetics on nanosheet/δ-MnO 2. In this work, graphene nanosheet/δ-MnO 2 (GN-MnO 2) was synthesized via a microwave-assisted method. The adsorption behavior of cobalt (Co(II)) and chromium (Cr(III)) ions onto GN-MnO 2 adsorbent was investigated through batch and column experiment under various conditions. GN-MnO 2 was characterized using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), N 2 adsorption/desorption (BET) and Boehm's titration method. Under static conditions, the effect of parameters like pH level, initial metal ion concentration, temperature, contact time and adsorbent dosage was studied. The optimum batch adsorption capacity of 403.4 mg/g and 491.98 mg/g were obtained at a temperature of 303 K and pH of 6 and 4 for Co(II) and Cr(III), respectively. Additionally, adsorption kinetics, isotherm, and thermodynamic were created. Regarding the column mode operation, the influence of both flow rate and bed height was examined and the data obtained for the total removal for both heavy metals were well described by Thomas and Bed depth service time (BDST) models. The column regeneration experiment was carried out for six cycles of desorption. The graphene nanosheet/δ-MnO 2 was proven to be a highly effective adsorbent and could easily be used for separation purpose. [ABSTRACT FROM AUTHOR]

The resistance of microorganisms to heavy metals in polluted environments is mediated by genetically determined mechanisms. One such mechanism includes the intracellular sequestration of heavy metals in polyphosphate (polyP) inclusions. In Cr(III) contaminated mediums, Ochrobactrum anthropi DE2010 is able to bind and sequester Cr(III) in polyP inclusions. In order to further study the relationship between Cr(III) tolerance and polyP production in O. anthropi DE2010, we carried out whole genomic sequencing, analysis of single nucleotide polymorphisms (SNPs), polyP chemical quantification, and determination of the relative abundance and morphometry of polyP inclusions. In the O. anthropi DE2010 genome, six polyP and pyrophosphate (PPi) metabolic genes were found. Furthermore, genomic analysis via SNPs calling revealed that O. anthropi ATCC49188 and DE2010 strains had average variations of 1.51% in their whole genome sequences and 1.35% variation associated with the principal polyP metabolic gene cluster. In addition, the accumulation of polyP in the DE2010 strain and number of polyP inclusions found were directly correlated with the concentration of Cr(III) in contaminated cultures. The results presented in this study may enhance the understanding of polyP production in response to Cr(III) toxicity in the O. anthropi DE2010 strain. This knowledge may facilitate the successful removal of Cr(III) from the natural environment. [ABSTRACT FROM AUTHOR]

Hydroxamic acids [R(CO)N(OH)R'] are flexible compounds for organic and inorganic analyses due to their frailer structures compared to the carboxylic acid. The syntheses and characterization of benzohydroxamic acid (BHA), its CH3–, OCH3–, Cl– para-substituted derivatives and their Cr(III) complexes are reported herein. The metal complexes were synthesized by reacting the hydroxamic acids with chromium(III) chloride hexahydrate in 2:1 molar ratio. The compounds were characterized via melting point, elemental analysis, FTIR, 1H and 13C NMR, TGA, mass spectrometry, molar conductance and UV–Visible. Data analysis suggests that each complex has the Cr(III) center coordinated to the carbonyl and hydroxy oxygen atoms of the hydroxamic acids in bidentate O,O manner and two water molecules to form octahedral geometry. Non-electrolytic behavior of the complexes was shown through their low molar conductivity. Cytotoxicity study against HCT116 and alpha-glucosidase inhibition test revealed that all complexes have higher activity than their parent ligands. Molecular docking study shows that the docking of active complexes is thermodynamically favorable and the inhibition efficiency may depend on the types and the numbers of molecular interactions established in the corresponding stable conformers. [ABSTRACT FROM AUTHOR]

Featured Application: The paper constitutes a contribution and an advancement in the treatment of wastewater contaminated by chromium. These waters are present in various sectors of the metallurgical industry (pickling liquors and effluents from electroplating processes, among others). The present investigation deals with the adsorption of chromium(III) from alkaline media, as representative of highly-caustic component solutions of nuclear tank wastes, using multiwalled carbon nanotubes. The adsorption of Cr(III) has been studied under various experimental conditions, i.e., stirring speed of the aqueous solution, initial metal and adsorbent concentrations, NaOH concentration in the aqueous solution, and temperature. The rate law indicated that chromium adsorption is well represented by the particle diffusion model, whereas the adsorption process fits with the pseudo-second order kinetic model within an exothermic setting. Equilibrium data fit to the Langmuir type-2 equilibrium isotherm in a spontaneous process. Chromium(III) can be eluted from metal-loaded nanotubes using acidic solutions, from which fine chromium(III) oxide pigment can ultimately be yielded. [ABSTRACT FROM AUTHOR]

In the crystal structure of the title compound, (C5H6N)[Cr(NCS)4(C5H5N)2]·C5H5N, the CrIII ions are octa­hedrally coordinated by four N-bonding thio­cyanate anions and two pyridine ligands into discrete negatively charged complexes, with the CrIII ion, as well as the two pyridine ligands, located on crystallographic mirror planes. The mean planes of the two pyridine ligands are rotated with respect to each other by 90°. Charge balance is achieved by one protonated pyridine mol­ecule that is hydrogen bonded to one additional pyridine solvent mol­ecule, with both located on crystallographic mirror planes and again rotated by exactly 90°. The pyridinium H atom was refined as disordered between both pyridine N atoms in a 70:30 ratio, leading to a linear N—H· · ·N hydrogen bond. In the crystal, discrete complexes are linked by weak C—H· · ·S hydrogen bonds into chains that are connected by additional C—H· · ·S hydrogen bonding via the pyridinium cations and solvent mol­ecules into layers and finally into a three-dimensional network. [ABSTRACT FROM AUTHOR]

The chelating ion exchanger Diaion CR20 was applied for removal of chromium(VI) ions in the pH range from 1.5 to 10 and in the presence of 1 M H2SO4. The speciation analysis was used to predict the reduction process. Reduction of chromium(VI) to chromium(III) was observed during the chromium(VI) ions sorption. The kinetic parameters for the pseudo-first-order and pseudo-second-order, Elovich and intraparticle diffusion models were calculated. The most common three isotherm models: Freundlich, Langmuir and Dubinin-Radushkevich were used to describe chromium(VI) uptake. It was proved that the polyamine groups present in selected ion exchanger are able to sorb both chromium(VI) and (III) ions. The maximal sorption capacity towards chromium(VI) ions was estimated at pH 1.5 - 169.49 mg Cr(VI)/g and 159.31 mg Cr(VI)/g in 1 M H2SO4. Both static and column methods were used in the investigations. [ABSTRACT FROM AUTHOR]

The efficiency of Aspergillus tamarii (isolated from sludge of a textile industry) was investigated to remediate the synthetic solutions of reactive red 120 (RR120) dye and chromium(III) separately. Also, parallel studies were conducted on the bioremediation of binary system of chromium(III) and RR120 dye in different ratios. The study was conducted to find the potential of the A. tamarii for removing chromium(III) and color from solutions containing only chromium or only RR120 dye or both and the effect of RR120 and chromium on the growth of the strain were observed. Maximum dye removal 81 mg/L was observed from 100 mg/L RR120 dye solution at pH 5 up to 50 hours. Maximum chromium removal 88.3 mg/L was observed from 100 mg/L chromium (III) solution at pH 5 up to 50 hours. In previous studies, A. tamarii was used as a bioremediator for removing different chromium complex dyes. The removal of chromium(III) and color were compared from solutions of synthetic mixtures and chromium complex dyes. The response of bioremediation study was validated using multiple regression analysis. [ABSTRACT FROM AUTHOR]

In this paper, the response surface methodology (RSM) was proposed for studying the synergistic extraction of chromium(III) ions by double-carrier supported liquid membrane (DCSLM) with organophosphorus carriers (D2EHPA/Cyanex272). At first, the optimization method of “one-factor-at-a-time” was adopted for determination of the best conditions for Cr(III) extraction by SLM with only one carrier (D2EHPA). The optimum/threshold D2EHPA concentration in the membrane phase increased linearly with initial concentration of Cr(III) ions in the feed phase. After the addition the second carrier (Cyanex272), the synergistic effect was observed. The largest percentage of extraction and the shorter time was obtained. The optimization of the synergistic extraction in DCSLM system by RSM using Box–Behnken design (BBD) for three variables (concentration and proportions of the carriers, initial concentration of Cr(III), and time of the process) was studied. The statistical model was verified with the analysis of variance (ANOVA) for the response surface quadratic model. The reduced quadratic model showed that the predicted values were in agreement with those obtained experimentally, as well as the fact that the concentrations and proportions of the carriers had a significant influence on the response. The developed model was considered to be verified and can be used to predict the optimal condition for the chromium ions extraction.

The kinetics of the reaction of substitution of aqua ligands in Cr(III) complexes by the amino acid l-histidine, in aqueous media and under acidic conditions (pH 3.60–5.79), has been studied with the aid of a spectrophotometric technique (at 530 nm). The rate-time profiles showed an initial acceleration period followed by a deceleration one. A model of three consecutive reactions has been applied, involving two long-lived intermediates (not reactive enough to be in steady state) and three rate constants: k1, k2 and k3, corresponding to the successive decays of the reactant, the first long-lived intermediate and the second, respectively. The three rate constants increased when the medium ionic strength was raised using KNO3 as background electrolyte, whereas the effect of KCl was of minor intensity, and showed base catalysis. The activation parameters for the reactions of Cr(III) with l-histidine, l-histidine methyl ester, l-arginine, l-lysine and 2-picolinic acid were also determined. The UV–Vis spectrum of the first long-lived intermediate was rather close to that of the inorganic reactant, whereas the spectrum of the second long-lived intermediate was somehow in between those corresponding to the inorganic reactant and the reaction product. The spectra of the final reactant mixtures revealed the co-existence of at least two complexes differing in the number of organic ligands, along with the corresponding protonated forms. The proposed mechanism involves the activation of the Cr(III) starting complex by deprotonation, as well as three rate-determining (slow) steps in which the breakage of a Cr(III)-aqua chemical bond takes place, thus leaving a vacant site to which the organic ligand can coordinate. [ABSTRACT FROM AUTHOR]

Chromium(III) used in tanning process is not consumed fully and around 30-40% of Chromium(III) is washed away to the environment causing severe environmental problem especially to the aquatic system. To remove Chromium(III) from wastewater, many different treatment techniques have been developed. This study deals with the ability of electrochemical peroxidation process for the removal of Chromium(III) from tannery wastewater in a batch stirred tank bench scale reactor with hopper bottom of 5 L working volume equipped with two iron electrodes which were investigated. The removal percentage of chromium was determined by varying operating parameters such as pH = 2-8, Fe2+ = 2-5 mg/L, H2O2 = 5-20 mg/L and current density = 10-40 mA/cm² were studied. The results showed that the Chromium(III) removal efficiency of 87% was achieved under optimum condition such as pH = 2, Fe2+ = 2 mg/L H2O2 = 15 mg/L, current density = 30 mA/cm² and contact time was 120 min with an electrical energy consumption of 0.073 kWh/L. The operating costs for the removal of Chromium(III) was found to be 0.4 $/m3 for treated tannery wastewater. The electrochemical peroxidation process proved to be an efficient and appropriate technique for the removal of Chromium(III) from tannery wastewater. [ABSTRACT FROM AUTHOR]

Double complex salts [Ln(C6H5NO2)3(H2O)2][Cr(NCS)6] · 2H2O, Ln = Lu (I), Ce (II), Y (III), have been synthesized by the reaction between aqueous solutions of Ln(NO3)3 (Ln = Lu, Ce, Y), K3[Cr(NCS)6], and nicotinic acid (C5H5NCOO). The salts representing light lilac crystalline powders have been studied by chemical analysis, IR spectroscopy, and single-crystal X-ray diffraction. The salts crystallize in monoclinic system, space group P21/n, Z = 4: a = 9.4969(15) Å, b = 25.606(4) Å, c = 15.541(2) Å, β = 107.126(4)°, V = 3624.34 Å3, ρcalcd = 1.864 g/cm3 for I; a = 9.6559(2) Å, b = 25.8492(5) Å, c = 15.5303(3) Å, β = 106.586(1)°, V = 3715.0(1) Å3, ρcalcd = 1.756 g/cm3 for II; and a = 9.5662(7) Å, b = 25.756(2) Å, c = 15.541(1) Å, β = 107.122(2)°, V = 3659.3(4) Å3, ρcalcd = 1.690 g/cm3 for III. The cations in the crystal structures of complexes I–III have a chain polymer structure, and the coordination polyhedron of chromium(III) represents a slightly distorted octahedron. The steric factor has no appreciable effect on the specific features of the crystal structures in the series of lanthanide hexa(isothiocyanato)chromate(III) complexes with nicotinic acid, and the content of crystallization water molecules is varied alone in their composition. [ABSTRACT FROM AUTHOR]

Chromium supplementation has been proposed to have beneficial effects in farm animals, particularly when under stress. The last two decades, in particular, have seen an emphasis on examining the effects of supplemental chromium on a variety of variables in chicks and chickens. Thus, given the recent approval of a Cr(III) compound for use in chicken feed in the United States and the recent surge in papers on the use of Cr in chicken feed, the need for a systematic review of studies utilizing chickens is extremely urgent and timely. With the exception of studies on cold-stressed laying hens, the results of studies of Cr supplementation of chickens, whether broilers or laying hens, were found to be too inconsistent for any firm conclusions to be drawn other than that Cr supplementation generally leads to accumulation of Cr in tissues. Few potential trends in terms or beneficial or deleterious effects from Cr supplementation were found regardless of strain of chicken, Cr source, Cr dose, duration of supplementation, or variable examined. Hence, in summary, no recommendation for the use of Cr as a supplement for the diet of chickens can be made at this time. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study was to examine the effect of chromium(III), iron(III), molybdenum(III) and nickel(II) and their combinations on pro- and antioxidant activity in mouse embryo fibroblasts and liver cancer cells. The present study shows that chromium(III), iron(III), nickel(II) and molybdenum(III) induce oxidative stress. In the case of chromium(III), nickel(II) and molybdenum(III) the intracellular ROS were dominant. However, in the case of iron(III) MDA was dominant - the end product of lipid peroxidation. Antioxidant activity of superoxide dismutase and catalase increased in low concentration of chromium(III); however, they decreased in higher concentrations. The same enzymes decreased after iron(III), nickel(II) and molybdenum(III) treatment in dose dependent manner. The activity of glutathione peroxidise decreased in dose dependent manner in all used microelements. Additions of Cr(III) at 200 μM plus Fe(III) at 1000 μM showed synergistic effect in ROS production and in lowering antioxidant activity. The same type of interaction in pairs Cr(III) at 1000 μM plus Fe(III) or Ni(II) or Mo(III) at concentration of 200 μM was observed. The protective effects of Cr(III) in antioxidant activity and in lowering intracellular ROS production in pairs of Cr(III) at 200 μM and Ni(II) or Mo(III) at concentration of 1000 μM were observed. Highlights • Cr(III), Fe(III), Ni(II) and Mo(III) induce oxidative stress in normal and cancer cell lines. • Cr(III), Fe (III), Ni(II) and Mo(III) impaired antioxidant activity in normal and cancer cells. • Antioxidant activity plays a crucial role in interactions between Cr(III) and Fe(III) or Ni(II) or Mo(III). [ABSTRACT FROM AUTHOR]