14302-87-5Relevant academic research and scientific papers
Heterogeneous Catalysis in Solution. Part 25. - Contrasting Behaviour of Reduced and Oxidised Platinum Surfaces in the Catalysis of the Reaction Between Cerium(IV) and Mercury (I)
Garnica Meza, Jose Manuel,Spiro, Michael
, p. 1383 - 1391 (1991)
The kinetics of the reaction between CeIV and Hg2+2 in 1 mol dm-3 HClO4 have been studied at 25 deg C in the presence of a large rotating platinum disc catalyst.When the disc was cathodically preconditioned, the catalytic rate was first order in cerium (IV) and zero order in mercury (I).It was also directly proportional to the square root of the rotation speed and exhibited a low activation energy, which showed that the reaction was mass-transport controlled.There was excellent agreement between the catalytic rate and the limiting current density for CeIV reduction (converted to rate units by Faraday's law), as would be expected from an electrochemical model of the catalysis.Diffusion coefficients of CeIV and Hg2+2 in 1 mol dm-3 HClO4 were determined from the limiting current measurements.Cyclic voltammetric sweeps after the catalytic runs revealed the presence of underpotential-deposited mercury layers on the platinum surface, and the number of mercury monolayers was evaluated.In contrast, when the platinum disc was anodically preconditioned, the catalytic rate was smaller, of fractional order in both reactants, and independent of rotation speed.The catalysis was therefore surface-controlled.Kinetic and cyclic voltammetric experiments pointed to the presence of two types of adsorbed mercury species on the oxidised platinum surface which strongly influenced the catalysis.Exposure of the oxidised disc to a solution of Hg2+2 ions before the addition of CeIV resulted in an increased catalytic rate because the mercury (I) ions had partly reduced the oxidised surface.
Electron-Transfer Quenching of Ruthenium(II) Photosensitizers by Mercury(II) in Aqueous Nitrate Media
Hauenstein, B. L.,Dressick, W. J.,Demas, J. N.,DeGraff, B. A.
, p. 2418 - 2422 (1984)
Excited-state interactions of tris(α-diimine)ruthenium(II) photosensitizers with Hg2+ were studied in aqueous nitrate media by using luminescence qyenching and flash photolysis methods.Quenching proceeds via oxidative electron transfer to yield Ru(III) and a Hg(I) free radical with high effenciency.Regardless of the excited-state reducing power of the photosensitizer, quenching was near but below the Marcus diffusion-controlled limit.Dimerization of the Hg(I) free radical to give Hg22+ competes effectively with the diffusion-limited back-electron-transfer reaction of the free radical with the Ru(III) species.The back-reaction rate of Hg22+ and Ru(III) is much slower and depends on E0(Ru(III/II)).The efficiency of electron-transferred-product separation is sensitive to E0(Ru(III/II)).The mechanism of the oxidation of Hg22+ by Ru(III) is discussed.
A study of mercury dissolution in aqueous solutions of sodium hypochlorite
Sizeneva,Val'tsifer,Strel'nikov
, p. 546 - 548 (2005)
Dissolution of mercury in aqueous solutions of sodium hypochlorite at pH 5.9-8.5, the corresponding reaction order, and the mechanism of this process were studied. The ratio of the rates of mercury oxidation and sodium hypochlorite decomposition was analyzed.
Mechanistic study of quinoliniumdichromate (QDC) oxidation of mercury(I) in aqueous sulfuric acid in the presence of micro amounts of palladium(II) - Autocatalysis in catalysis
Chimatadar,Basavaraj,Nandibewoor
, p. 2976 - 2984 (2006)
The kinetics of oxidation of mercury(I) with quinoliniumdichromate (QDC) in the presence of micro amounts of palladium(II) catalyst in aqueous sulfuric acid medium has been studied under varying conditions. The active species of oxidant, reductant and catalyst in the reaction medium were understood to be HCrO4-, [Hg2(SO4)HSO4]- and PdCl+, respectively. The autocatalysis by one of the products, chromium(III), was observed. A composite scheme and rate law were proposed. Reaction constants involved in the mechanism have been evaluated.
Visible light assisted photodegradation of thimerosal by high performance ZnFe2O4/poly(o-phenylenediamine) composite
Sandoval, Claudio,Ranganathan, Suresh,Ramírez, Eimmy,Mansilla, Héctor D.,Dinamarca, Robinson,Pecchi, Gina,Yá?ez, Jorge
, p. 8 - 15 (2019)
Thimerosal is a mercury-based preservative that is used in pharmaceuticals, vaccines and health-care products. However, thimerosal toxicity has been well explored and hence it should be properly treated for avoiding its occurrence in the environment. Hence, we synthesized visible light active ZnFe2O4/poly(o-phenylenediamine) composite as photocatalyst for degradation of thimerosal. The well characterized ZnFe2O4 and composite effectively degraded thimerosal and subsequently reduced Hg(II) into Hg(0) under visible light irradiation. Thimerosal degradation by-products and generation of Hg(0) were analyzed by high performance liquid chromatography and atomic fluorescence spectroscopy. The composite showed better photocatalytic activity than the pure ZnFe2O4 nanoparticles. Under the optimum conditions, 90.2% degradation of thimerosal was achieved within 6 h of irradiation. An efficient charge separation ability of poly(o-phenylenediamine) contributes to the high photocatalytic performance of the composite. This work provides a new photocatalytic degradation pathway of thimerosal and thus will stimulate further studies in the removal of organometallic contaminants.
Phases of underpotentially deposited Hg on Au(111): An in situ surface X-ray diffraction study
Li, Jun,Abru?a, Héctor D.
, p. 2907 - 2916 (1997)
We report on an in situ surface X-ray diffraction study of the underpotential deposition (UPD) of mercury on Au(111). We have observed three UPD phases present at potentials prior to bulk mercury deposition. These phases consist of two well-ordered intermediate states and what appears to be either a fully discharged two-dimensional liquid Hg layer or a monolayer of an amorphous Hg-Au alloy. Both ordered intermediate phases have hexagonal structures with lattice vectors that are rotated 30° from those of the Au(111) substrate. The first phase (phase I), present at a potential of +0.68 V, was only observed on fresh flame-annealed Au(111) electrodes and appears to be an open incommensurate structure with a lattice constant of 3.86 ± 0.03 A?. This phase appears to be metastable since it changes to a second ordered phase (phase II) after a certain time at +0.68 V or after the potential is moved to more negative values (+0.63 V). The second phase has a more compact lattice with a = 3.34 ± 0.01 A? and appears to be a commensurate 2×2 structure with 2/3 of the Hg atoms at threefold hollow sites and 1/3 on atop sites. Similar to the first one, this phase is also metastable and can be transformed to a final, fully discharged, state of a two-dimensional liquid Hg layer or an amorphous Hg-Au alloy. The entire Hg UPD process, from Hg2+ to the fully discharged metallic Hg layer, agrees well with a multistep mechanism based on previous electrochemical kinetic studies on polycrystalline Au electrodes. Our results also show that the UPD of Hg on Au(111) electrodes is quite different from that of other metals such as Cu, Ag, Tl, and Pb.
Photodisproportionation of Hg22+
Kunkely, Horst,Vogler, Arnd
, p. 375 - 377 (2002)
The photolysis of Hg2+2 in tetrahydrofuran induced by metal-metal σσ* excitation leads to the generation of Hg0 and Hg2+. The quantum yield of this photodisproportionation is ? = 0.03 at λirr = 254 nm
Outstanding performance of CuO/Fe-Ti spinel for Hg0oxidation as a co-benefit of NO abatement: significant promotion of Hg0oxidation by CuO loading
Sun, Pengxiang,Mei, Jian,Wang, Chang,Ding, Zhen,Hong, Qianqian,Yang, Shijian
, p. 2316 - 2326 (2021)
Conversion of gaseous Hg0to soluble Hg2+using selective catalytic reduction (SCR) catalysts with gaseous HCl as an oxidant as a co-benefit of NO abatement is widely used for resolving Hg pollution from coal-burning power plants. Nevertheless, the performances of conventional V2O5-WO3/TiO2for NO abatement and Hg0oxidation are unsatisfactory. In this study, CuO/Fe-Ti spinel was exploited as a novel and high-activity catalyst for the simultaneous removal of NO and Hg0. The outstanding SCR activity and high N2selectivity of Fe-Ti spinel did not distinctly decrease after CuO loading; thus, CuO/Fe-Ti spinel achieved efficient NO reduction. Although Hg0physical adsorption onto Fe-Ti spinel was slightly suppressed after CuO loading, the Cl* radical formation was appreciably promoted as both HCl adsorption and the conversion of adsorbed Cl?to Cl* radicals were promoted. Hence, the Hg0oxidation activity of Fe-Ti spinel was appreciably improved after CuO loading, and the rate of Hg0oxidation for CuO/Fe-Ti spinel reached approximately 6.8-8.7 μg g?1min?1, which was better than those of most other SCR catalysts. In summary, CuO/Fe-Ti spinel shows great promise as an SCR catalyst for Hg0oxidation as a co-benefit of NO abatement from coal-burning flue gas (CFG).
The Oxidation of Mercury(I) by Ozone in Acidic Aqueous Solutions
McElroy, W. John,Munthe, John
, p. 254 - 257 (2007/10/02)
The oxidation of mercury(I) (Hg22+) by ozone (O3) in acidic aqueous solutions has been investigated using stopped-flow techniques.The reaction is essentially second order, and the rate was found to be independent of pH and temperature for the conditions employed (pH 1-3, T = 283-293 K) with a rate coefficient k(Hg22+ + O3) = (9.2 +/- 0.9) * 106 M-1 s-1.A small first-order component is attributed to the dissociation of Hg22+, with k(Hg22+ -> Hg0 + Hg2+) = 4.5 +/- 3.5 s-1 (pH 1, T = 293 K).Elemental mercury is subsequently oxidised by ozone at a rate which appears to approach the diffusion-controlled limit.
Palladium(II) catalysed cerium(IV) oxidation of mercury(I) in aqueous perchloric acid
Tuwar, S. M.,Nandibewoor, S. T.,Raju, J. R.
, p. 235 - 240 (2007/10/02)
Palladium(II) is found to singnificantly catalyse the cerium(IV)-mercury(I) reaction in aqueous perchloric acid and the reaction follows the rate law which fits the two-step mechanism as shown below where a transient Pd(III) species takes part and ka, kb and kc are the rate constants. Ce(IV) + Pd(II) Ce(III) + Pd(III) Pd(III) + Hg(I) Pd(II) + Hg(II)The main active species of oxidant and catalyst are found to be respectively HCe(SO4)3- and PdCl+.The constants ka and kb/kc have been evaluated.
