EPR Spectroscopic Studies on the Formation of Chromium(V) Peroxo Complexes in the Reaction of Chromium(VI) with Hydrogen Peroxide

Zhang, Lianbo; Lay, Peter A.

doi:10.1021/ic971069j

Cited by 59 publications

(47 citation statements)

References 56 publications

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“…The collected signal intensity versus time data show a firstorder decay of the chromium(V) complex. The product chromium(V) species was identified as [Cr V (O 2 ) 4 ] 3-based on its EPR parameters, which were identical with those reported in the literature [27,28]. No EPR signal was registered for the [Cr(pic) 3 ] 0 system under the same experimental conditions.…”

Section: Kinetic Measurementssupporting

confidence: 66%

Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2]− by hydrogen peroxide

et al. 2017

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Biological tests performed using 3T3 fibroblasts indicated low cytotoxicities for the complexes mer- -, where pic = picolinate anion and Cys = cysteine. Oxidation of these complexes by hydrogen peroxide was studied in NaOH and NaHCO 3 media. Electronic (UV-Vis) and EPR spectroscopies were used to monitor the reaction course. 3-anion at pH & 8 was followed by EPR spectroscopy. Based on the obtained kinetic and spectroscopic data, mechanisms for the redox transformations of these chromium(III) complexes are proposed.

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Section: Kinetic Measurementssupporting

confidence: 66%

Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2]− by hydrogen peroxide

et al. 2017

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“…At that point, the signal was stable for at least a few hours and [24,25]: a strong isotropic signal due to chromium isotopes with I = 0 (90.5 %) at g iso = 1.9722 ± 0.0003 and peak-to-peak width, DBpp 9 0.2 mT. A small isotropic satellite signal, split into a quartet due to hyperfine coupling by the less abundant (9.5 %) 53 Cr isotope (I = 3.2), is also observed with a ( 53 Cr) = 18.59 9 10 -4 cm -1 [24,25]. Aquation of the complexes is conveniently monitored by spectral changes in strongly acidic (Fig.…”

Section: Epr Measurementsmentioning

confidence: 97%

Hydrolytic and redox transformations of chromium(III) bis-oxalato complexes with glutaminic acid and glutamine: a kinetic, UV–Vis and EPR, study

Kiersikowska

Kita

et al. 2016

Transition Met Chem

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The title complexes have been synthesized, chromatographically isolated and characterized by their ligands to metal ratio determinations and spectroscopic analyses. The kinetics of the first aquation stage, i.e., the amino acid chelate ring opening via the Cr-N bond cleavage, has been studied spectrophotometrically in acidic and alkaline media. Hydrogen peroxide oxidizes the complexes in alkaline media to CrO 4 2-anion and a relatively stable Cr(V) complex. Consecutive biphasic kinetics through two first-order steps were observed for the base hydrolysis and the oxidation process, whereas the acidcatalyzed aquation obeys a simple first-order pattern. Based on the kinetic and spectroscopic data, mechanisms of the coordinated amino acid liberation and chromium(III) oxidation are discussed.

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“…24 The ESR parameters of Cr(V) and OEC(As(IV)) were operated according to the literatures, respectively. 25,26 The computational model and descriptions were provided in the Supporting Information.…”

Section: • and Omentioning

confidence: 99%

Redox Conversion of Chromium(VI) and Arsenic(III) with the Intermediates of Chromium(V) and Arsenic(IV) via AuPd/CNTs Electrocatalysis in Acid Aqueous Solution

Sun

Zhang

Qin

et al. 2015

Environ. Sci. Technol.

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Simultaneous reduction of Cr(VI) to Cr(III) and oxidation of As(III) to As(V) is a promising pretreatment process for the removal of chromium and arsenic from acid aqueous solution. In this work, the synergistic redox conversion of Cr(VI) and As(III) was efficiently achieved in a three-dimensional electrocatalytic reactor with synthesized AuPd/ CNTs particles as electrocatalysts. The AuPd/CNTs facilitated the exposure of active Pd{111} facets and possessed an approximate two-electrontransfer pathway of oxygen reduction with the highly efficient formation of H 2 O 2 as end product, resulting in the electrocatalytic reduction of 97.2 ± 2.4% of Cr(VI) and oxidation of 95.7 ± 4% of As(III). The electrocatalytic reduction of Cr(VI) was significantly accelerated prior to the electrocatalytic oxidation of As(III), and the effectiveness of Cr(VI)/As(III) conversion was favored at increased currents from 20 to 150 mA, decreased initial pH from 7 to 1 and concentrations of Cr(VI) and As(III) ranging from 50 to 1 mg/L. The crucial intermediates of Cr(V) and As(IV) and active free radicals HO• and O 2 •− were found for the first time, whose roles in the control of Cr(VI)/As(III) redox conversion were proposed. Finally, the potential applicability of AuPd/CNTs was revealed by their stability in electrocatalytic conversion over 10 cycles. ■ INTRODUCTIONThe combined pollution of heavy metals in acid wastewater has become a formidable problem to environmental scientists and engineers for decades. As a consequence of improper treatment, effluents containing abundant heavy metal ions such as lead, nickel, copper, arsenic, or chromium may inflow into surface water or seep into groundwater, which pose great threats to aquatic life and drinking water sources.1,2 Thus, it is urgent to remove the heavy metals prior to their discharge into the environment.Arsenic and chromium, as priority pollutants, are highly toxic and frequently coexist with highly acidic wastewater (e.g., acid mine drainage).3 The valence states of arsenic or chromium have decisive impacts on their environmental fate and toxic effect.4,5 For example, As(III) is the most prevalent form of arsenic in the natural environment, which is more toxic than As(V) to mammals. 6 Additionally, As(III) is also more mobile than As(V), because As(III) is quite easier originated from the oxidative weathering or reductive dissolution of As-containing minerals, suggesting the immobilization of As(III) in acid solution more strictly depends on the redox conditions. 7 Therefore, it is advisible to preoxidize As(III) to As(V), coupled with a following adsorption or coprecipitation of the As(V) by using adsorbents or coagulants, to finally enhance the removal of arsenic species in acid aqueous solution. 8,9 Similarly, Cr(VI) is quite soluble and mobile in acid wastewater, 10 whileCr(III) is less toxic and insoluble, and can be effectively immobilized as the hydroxide in a wide pH range. 11,12 Thus, the prereduction of Cr(VI) to Cr(III) is conducive to the complete removal of ch...

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EPR Spectroscopic Studies on the Formation of Chromium(V) Peroxo Complexes in the Reaction of Chromium(VI) with Hydrogen Peroxide

Cited by 59 publications

References 56 publications

Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2]− by hydrogen peroxide

Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2]− by hydrogen peroxide

Hydrolytic and redox transformations of chromium(III) bis-oxalato complexes with glutaminic acid and glutamine: a kinetic, UV–Vis and EPR, study

Redox Conversion of Chromium(VI) and Arsenic(III) with the Intermediates of Chromium(V) and Arsenic(IV) via AuPd/CNTs Electrocatalysis in Acid Aqueous Solution

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