Reduction of antimony by nano-particulate magnetite and mackinawite

AbstractThe speciation of antimony is strongly influenced by its oxidation state (V, III, 0, —III). Redox processes under anaerobic groundwater conditions may therefore greatly alter the environmental behaviour of Sb. Employing X-ray absorption and photoelectron spectroscopy, we show here that Sb(V) is reduced to Sb(III) by magnetite and mackinawite, two ubiquitous Fe(II)-containing minerals, while Sb(III) is not reduced further. At the surface of magnetite, Sb(III) forms a highly symmetrical sorption complex at the position otherwise occupied by tetrahedral Fe(III). The Sb(V) reduction increases with pH, and at pH values >6.5 Sb(V) is completely reduced to Sb(III) within 30 days. In contrast, at the mackinawite surface, Sb(V) is completely reduced across a wide pH range and within 1 h. The Sb(V) reduction proceeds solely by oxidation of surface Fe(II), while the oxidation state of sulphide is conserved. Independent of whether Sb(V) or Sb(III) was added, an amorphous or nano-particulate SbS3-like solid formed.

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Synthesis of 1-(2-Hydroxyphenyl) Dec-2-en-1-One Oxime and Its Flotation and Adsorption Behavior for Malachite

Frontiers in Chemistry ◽

10.3389/fchem.2020.592771 ◽

2020 ◽

Vol 8 ◽

Author(s):

Liqing Li ◽

Lin Yang ◽

Fangxu Li

Keyword(s):

Photoelectron Spectroscopy ◽

Adsorption Behavior ◽

Xps Analysis ◽

X Ray ◽

Benzohydroxamic Acid ◽

Wide Ph Range ◽

Flotation Performance ◽

Ph Range

A novel collector of 1-(2-hydroxyphenyl) dec-2-en-1-one oxime (HPDO) was synthesized from 2-hydroxy acetophenone and octanal, and its flotation and adsorption behavior for malachite were studied by flotation tests and x-ray photoelectron spectroscopy (XPS) analysis. The flotation results of a single mineral show HPDO is a special collector for malachite. Compared with benzohydroxamic acid (BHA), isobutyl xanthate (SIBX), and dodecylamine (DA), HPDO exhibits excellent flotation performance for malachite and satisfied selectivity against quartz and calcite over a wide pH range. The HPDO with a concentration of 200 mg/L can float 94% malachite at pH 8, while only recovering 7.8% quartz and 28% calcite. XPS data give clear evidence for the formation of a Cu-oxime complex on malachite surfaces after HPDO adsorption.

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Adsorption of As(V) by the Novel and Efficient Adsorbent Cerium-Manganese Modified Biochar

Water ◽

10.3390/w12102720 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2720

Author(s):

Ting Liang ◽

Lianfang Li ◽

Changxiong Zhu ◽

Xue Liu ◽

Hongna Li ◽

...

Keyword(s):

Manganese Oxide ◽

Photoelectron Spectroscopy ◽

Water Environment ◽

Polluted Water ◽

X Ray ◽

Modified Biochar ◽

Wide Ph Range ◽

Infrared Spectrometer ◽

Pseudo Second Order ◽

Ph Range

Arsenic has become a global concern in water environment, and it is essential to develop efficient remediation methods. In this study, a novel adsorbent by loading cerium and manganese oxide onto wheat straw-modified biochar (MBC) was manufactured successfully aiming to remove arsenic from polluted water. Through scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FT-IR), and other techniques, it was found the loading of cerium and manganese oxide on MBC played a significant role in As(V) adsorption. The results of the batch test showed that the adsorption of MBC followed the pseudo-second order kinetics and Langmuir equation. The adsorption capacity of MBC was 108.88 mg As(V)/g at pH = 5.0 (C0 = 100 mg/L, dosage = 0.5 g/L, T = 298 K) with considerable improvement compared to the original biochar. Moreover, MBC exhibited excellent performance over a wide pH range (2.0~11.0). Thermodynamics of the sorption reaction showed that the entropy (ΔS), changes of enthalpy (ΔH) and Gibbs free energy (ΔG), respectively, were 85.88 J/(moL·K), 22.54 kJ/mol and −1.33 to −5.20 kJ/mol at T = 278~323 K. During the adsorption, the formation of multiple complexes under the influence of its abundant surface M-OH (M represents the Ce/Mn) groups involving multiple mechanisms that included electrostatic interaction forces, surface adsorption, redox reaction, and surface complexation. This study indicated that MBC is a promising adsorbent to remove As(V) from polluted water and has great potential in remediating of arsenic contaminated environment.

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Changes in u(VI) SPeciation Upon Sorption onto Montmorillonite from Aqueous and Organic Solutions

MRS Proceedings ◽

10.1557/proc-257-315 ◽

1991 ◽

Vol 257 ◽

Cited By ~ 3

Author(s):

Catherine Chisholm-Brause ◽

Steven D. Conradson ◽

P. Gary Eller ◽

David E. Morris

Keyword(s):

Oxidation State ◽

Aqueous Systems ◽

X Ray ◽

Ph Values ◽

Uranium Oxidation ◽

Organic Solutions ◽

X Ray Absorption ◽

Hydrolysis Of ◽

Uranium Species ◽

Lines Of Evidence

ABSTRACTThe speciation of UO22+ and UO22+/ TBP mixtures has been investigated in solution and intercalated with the reference smectite clay SAz-1 using x-ray absorption, Raman, andluminescence spectroscopies. Neither aquated UO22+ nor its TBP complex undergoes any detectable changes in uranium oxidation state on intercalation. Further, at the pH values employed in this work, there is no evidence for hydrolysis of the uranium species to generate dimeric or higher order uranium oligomers. However, we do find indications that the structures of the solution complexes are altered on intercalation, particularly for the UO22+TBP system and for more dilute UO22+/aqueous systems. In addition, several lines of evidence suggest that, at the loading levels used in this study, the uranyl species is interacting with two or more spectroscopically distinguishable sites on SAz-1.

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Preparation and Structural Characterization of Methylmercury(II) Complexes of 5-Aza- and 6-Azauracil Derivatives

Zeitschrift für Naturforschung B ◽

10.1515/znb-1987-1212 ◽

1987 ◽

Vol 42 (12) ◽

pp. 1556-1562 ◽

Cited By ~ 7

Author(s):

W. S. Sheldrick ◽

S. Heeb

Keyword(s):

Structural Analysis ◽

Binding Sites ◽

Ionic Complex ◽

X Ray ◽

H Nmr ◽

Ph Values ◽

Nmr Data ◽

Wide Ph Range ◽

Ph Range

Abstract1:1 Methylmercury(II) complexes of the anti-tumour agent 6-azauracil (6AUH2) and its derivatives 6-azathymine (6ATH2). 1-methyl-6-azauracil (6AMUH) and 1-methyl-6-azathymine (6AMTH) have been isolated from aqueous solutions of CH3HgOH and the respective base. N3-Coordination was established by X-ray structural analysis for both [(CH3Hg)6 AUH] (1) (pH 6-8) and [(CH3Hg)6 AMT] (5) (pH 4-12); in addition 1H NMR data are in accordance with an identical binding site in the complexes [(CH3Hg)6AMU] (3) and [(CH3Hg)6 ATH] (4). Using an excess of CH3HgOH. 2:1 complexes with N1, N3-coordination may be prepared for both 6 AUH: and 5 AUH2 in a wide pH range (4-12 and 6-12 respectively). At pH values of 3-4 a 3:1 complex [(CH3Hg)35 AU]NO3 (7), with N1, N3, N5-coordination may be isolated: the binding sites were confirmed by X-ray structural analysis. In no case could an ionic complex with N6- coordination be isolated for a 6-azapyrimidine derivative. The binding preferences of the bases are discussed in the light of MNDO calculations.

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Mn Oxidation States in Bax CsyMnzTi8-zO16

MRS Proceedings ◽

10.1557/proc-824-cc4.6 ◽

2004 ◽

Vol 824 ◽

Cited By ~ 7

Author(s):

M.L. Carter ◽

E.R. Vance ◽

D. R. G. Mitchell ◽

Z. Zhang

Keyword(s):

Energy Loss ◽

Absorption Spectra ◽

Electron Energy ◽

Oxidation State ◽

Electron Energy Loss Spectroscopy ◽

Photoelectron Spectroscopy ◽

Oxidation States ◽

X Ray ◽

Electron Energy Loss ◽

X Ray Absorption

AbstractTwo Bax CsyMnzTi8-zO16 hollandite samples, containing excess rutile, have been prepared, targeting the Mn valence as 3+ by sintering at 1300oC in air (z = 2x +y) and as 2+ (z = x + y/2) in argon. SEM showed the sample sintered in air to contain major hollandite and minor Mn titanate and rutile. The sample sintered in argon contain major hollandite, and minor Ba titanate and rutile. X-ray absorption near edge spectroscopy (XANES), electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) were used to determine the oxidation state of the Mn in the samples. Transmission manganese K-edge X-ray absorption spectra of the samples were similar but the precise ratio of oxidation states could not be calculated from these spectra.

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Facile Production of a Fenton-Like Photocatalyst by Two-Step Calcination with a Broad pH Adaptability

Nanomaterials ◽

10.3390/nano10040676 ◽

2020 ◽

Vol 10 (4) ◽

pp. 676

Author(s):

Siyang Ji ◽

Yanling Yang ◽

Xing Li ◽

Hang Liu ◽

Zhiwei Zhou

Keyword(s):

Rhodamine B ◽

Photoelectron Spectroscopy ◽

Active Oxygen Species ◽

Oxygen Species ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Wide Ph Range ◽

Calcination Method ◽

Ph Range

A novel heterogeneous Fenton-like photocatalyst, Fe-doped graphitic carbon nitride (Fe-g-C3N4), was produced by facile two-step calcination method. This Fe–g–C3N4 catalyzed rhodamine B degradation in the presence of H2O2 accompanied with visible light irradiation. transmission electron microscopy(TEM), x-ray diffraction (XRD), FT-IR, x-ray photoelectron spectroscopy (XPS), and photoluminescence fluorescent spectrometer (PL) characterization analysis methods were adopted to evaluate the physicochemical property of samples. It can be observed that the Fe-g-C3N4 exhibited excellent photocatalytic Fenton-like activity at a wide pH range of 3–9, with rhodamine B(RhB) degradation efficiency up to 95.5% after irradiation for 45 min in the presence of 1.0 mM H2O2. Its high activity was ascribed to the formation of Fe–N ligands in the triazine rings that accelerated electron movement driving the Fe(III)/Fe(II) redox cycle, and inhibited photo-generated electron hole re-combinations for continuous generation of reactive oxygen species by reactions between Fe(II) and H2O2. The main active oxygen species were hydroxyl radicals, followed by superoxide radicals and hole electrons. This produced catalyst of Fe–g–C3N4 shows excellent reusability and stability, and can be a promising candidate for decontamination of wastewater.

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A Mechanism for the Adsorption of 2-(Hexadecanoylamino)Acetic Acid by Smithsonite: Surface Spectroscopy and Microflotation Experiments

Minerals ◽

10.3390/min9010015 ◽

2018 ◽

Vol 9 (1) ◽

pp. 15 ◽

Cited By ~ 1

Author(s):

Bin Luo ◽

Junbo Liu ◽

Quanjun Liu ◽

Chao Song ◽

Li Yu ◽

...

Keyword(s):

Acetic Acid ◽

Zeta Potential ◽

Photoelectron Spectroscopy ◽

Sulfide Mineral ◽

X Ray ◽

Surface Spectroscopy ◽

Wide Ph Range ◽

Flotation Performance ◽

Ph Range ◽

Important Objective

Zinc is mostly extracted from oxidized zinc and zinc sulfide minerals, and this process involves flotation as a key step. While it is easier to float the sulfide mineral, its consumption and depletion has led to an increased reliance on oxidized zinc minerals, including smithsonite. Hence, the development of efficient ways of collecting smithsonite by flotation is an important objective. Herein, we describe the use of 2-(hexadecanoylamino)acetic acid (HAA), a novel surfactant, as a collector during smithsonite flotation. The mechanism and flotation performance of HAA during smithsonite flotation was investigated by total organic carbon (TOC) content studies, zeta potential measurements, Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses, combined with microflotation experiments. The flotation results revealed that HAA was an excellent collector in pulp over a wide pH range (9–12) and at a relatively low concentration (2 × 10−4 mol/L), at which a recovery of close to 90% of the smithsonite mineral was obtained. TOC content studies revealed that the good flotation recovery was ascribable to large amounts of collector molecule adsorbed on the smithsonite surface, while zeta potential measurements showed that the HAA was chemically adsorbed onto the smithsonite. FTIR and XPS analyses revealed that the HAA collector molecules adsorbed onto the smithsonite surface as zinc–HAA complexes involving carboxylate moieties and Zn sites on the smithsonite surface in alkaline solution.

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Formation of Hg(II) tetrathiolate complexes with cysteine at neutral pH

Canadian Journal of Chemistry ◽

10.1139/cjc-2015-0375 ◽

2016 ◽

Vol 94 (4) ◽

pp. 373-379 ◽

Cited By ~ 7

Author(s):

Thomas Warner ◽

Farideh Jalilehvand

Keyword(s):

Spectroscopic Techniques ◽

Amino Groups ◽

Dilute Solutions ◽

Concentrated Solutions ◽

X Ray ◽

Raman Spectroscopic ◽

Ph Values ◽

Lower Charge ◽

Ph Range ◽

X Ray Absorption

Mercury(II) ions precipitate from aqueous cysteine (H2Cys) solutions containing H2Cys/Hg(II) mole ratio ≥ 2.0 as Hg(S-HCys)2. In the absence of additional cysteine, the precipitate dissolves at pH ∼12 with the [Hg(S,N-Cys)2]2– complex dominating. With excess cysteine (H2Cys/Hg(II) mole ratio ≥ 4.0), higher complexes form and the precipitate dissolves at lower pH values. Previously, we found that tetrathiolate [Hg(S-Cys)4]6– complexes form at pH = 11.0; in this work, we extend the investigation to pH values of physiological interest. We examined two series of Hg(II)–cysteine solutions in which CHg(II) varied between 8 and 9 mmol/L and 80 and 100 mmol/L, respectively, with H2Cys/Hg(II) mole ratios from 4 to ∼20. The solutions were prepared in the pH range 7.1–8.8 at the pH at which the initial Hg(S-HCys)2 precipitate dissolved. The variations in the Hg(II) speciation were followed by 199Hg NMR, X-ray absorption, and Raman spectroscopic techniques. Our results show that in the dilute solutions (CHg(II) = 8–9 mmol/L), mixtures of di-, tri- (major), and tetrathiolate complexes exist at moderate cysteine excess (CH2Cys ∼0.16 mol/L) at pH 7.1. In the more concentrated solutions (CHg(II) = 80–100 mmol/L) with high cysteine excess (CH2Cys > 0.9 mol/L), tetrathiolate [Hg(S-cysteinate)4]m−6 (m = 0–4) complexes dominate in the pH range 7.3–7.8, with lower charge than for the [Hg(S-Cys)4]6– complex due to protonation of some (m) of the amino groups of the coordinated cysteine ligands. The results of this investigation could provide a key to the mechanism of biosorption and accumulation of Hg(II) ions in biological/environmental systems.

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