Reduction Of Persulfate Research Articles

Electrochemical Detection of Persulfate at the Modified Glassy Carbon Electrode with Nanocomposite Containing Nano‐Ruthenium Oxide/Thionine and Nano‐Ruthenium Oxide/Celestine Blue

AbstractThe present study describes the fabrication of a sensitive amperometric sensor for the determination of persulfate. The immobilization surface was prepared by modifying a glassy carbon (GC) electrode with a nanocomposite containing ruthenium oxide (RuOx) nanoparticles and thionine (TH) or celestin blue (CB). The modified electrodes indicated excellent electrocatalytic activity toward persulfate reduction at a potential of +0.1 V. The proposed sensor showed detection limits of 1.46 µM for the GC/RuOx/TH modified electrode and 2.64 µM for the GC/RuOx/CB modified electrode. The sensitivities were obtained as 3 nA µM−1 at a concentration range of 10 µM to 11 mM for the GC/RuOx/TH modified electrode and 1 nA µM−1 at a concentration range of 10 µM to 6 mM for the GC/RuOx/CB modified electrodes.

Mechanism of Persulfate Activation by Phenols

The activation of persulfate by phenols was investigated to further the understanding of persulfate chemistry for in situ chemical oxidation (ISCO). Phenol (pKa = 10.0) activated persulfate at pH 12 but not at pH 8, suggesting activation occurred only via the phenoxide form. Evaluation of the phenoxide activation mechanism was complicated by the concurrent activation of persulfate by hydroperoxide anion, which is generated by the base catalyzed hydrolysis of persulfate. Therefore, phenoxide activation was investigated using pentachlorophenoxide at pH 8.3, midway between the pKa of pentachlorophenol (pKa = 4.8) and that of hydrogen peroxide (pKa = 11.8). Of the two possible mechanisms for phenoxide activation of persulfate (reduction or nucleophilic attack) the results were consistent with reduction of persulfate by phenoxide with oxidation of the phenoxide. The concentration of phenoxide required for maximum persulfate activation was low (1 mM). The results of this research document that phenoxides activate persulfate via reduction; phenolic moieties ubiquitous to soil organic matter in the subsurface may have a significant role in the activation of persulfate during its injection into the subsurface for ISCO. Furthermore, the results provide the foundation for activation of persulfate by other organic anions without the toxicity of phenols, such as keto acids.

Electroanalysis in Russia and Belorussia

The aim of this topical cluster is to draw attention of electroanalytical audience to Russian and Belorussian electroanalytical schools. Some of these schools are known due to their publications in international journals, some are less known. Unfortunately, even the call for a special issue did not raise significant submission activity. Soviet electrochemistry school is known internationally; the main contributions were made by A. N. Frumkin and V(B).G. Levich. A. N. Frumkin, recognized as a founder of soviet electrochemical school, also founded both the chair of electrochemistry in M. V. Lomonosov Moscow State University and the Institute of Electrochemistry. The latter recently joined to Institute of Physical Chemistry. A. N. Frumkin’s impact to electrochemistry is due to both theoretical and experimental achievements. It’s not surprising that one of the most prestigious awards of the International Society of Electrochemistry (ISE) is the Frumkin Memorial Medal. V(B).G. Levich contributed to electrochemistry with his hydrodynamic theory inventing the rotating disk electrode as a hydrodynamic tool for investigation of electrode kinetics. Electroanalysis was growing in a close relation to fundamental electrochemistry. For instance, the background of the famous Frumkin theory on persulfate reduction was the requirement to detect this anion. As everywhere, electroanalysis in USSR was developed due to detection of transition metals by stripping voltammetry (Moscow, Ekaterinburg, Tomsk, Kazan) and potentiometry (Minsk). More recently, an “electronic tongue” on the basis of a set of potentiometric sensors was elaborated (St. Petersburg). A significant contribution to both fundamental and analytical electrochemistry was the discovery of the direct bioelectrocatalysis operating according to the direct (mediator-free) electron exchange between the electrode and the active site of the immobilized enzyme (Moscow). I believe that the present topical cluster will raise attention of Russian electrochemists to Electroanalysis and further involve them in electroanalytical audience. 1 Arkardy A. Karyakin

Competitive emission processes due to band-band and donor-acceptor transitions at the n-silicon carbide/electrolyte interface

Electroluminescence (EL) due to band-band (423 nm) as well as donor-acceptor (565 nm) transitions was observed at n-SiC electrodes during the reduction of persulfate under pulsed cathodic polarization. The EL peak at 423 nm was obtained only when pulsed at cathodic potentials greater than the band gap of the semiconductor (E g ∼3.0 eV) but not under steady-state polarization. The EL decay characteristics, monitored at these two emission bands, indicate the competitive recombination processes during the hole injection of persulfate radicals into the valence band of the semiconductor. It was considered that the band-band emission comes from the bulk of the semiconductor

ChemInform Abstract: Influence of the Alkali Metal Cation in Solution on the Electroluminescence of a ZnO Electrode During Persulfate Reduction.

AbstractThe electroluminescence (EL) intensity of a ZnO electrode in an aqueous electrolyte during the pulsed reduction of 820%′ depends strongly on the alkali metal countercation (Li+, Na+, K+, NHI ).

Influence of the alkali metal cation in solution on the electroluminescence of a zinc oxide electrode during persulfate reduction

L'intensite de l'electroluminescence d'une eletrode d'oxyde de zinc, dans un electrolyte aqueux, au cours d'une reduction pulsee des anions de S 2 O 8 2− , depend fortement de l'ion antagoniste alcalin monovalent M + (Li + , Na + , K + et NH 4 + ) en solution

Electroluminescence Transients at ZnO‐Electrodes by Hole Injection during Persulfate Reduction

AbstractElectroluminescence transients at the ZnO‐electrolyte interface have been studied during pulsed reduction of persulfate. The spectral distribution of the emitted light centers around the band gap energy and indicates hole injection from the intermediately formed SO4‐ radicals and consecutive radiative recombination with electrons. The decay in the photon emission during a cathodic current pulse is attributed to the formation of recombination centers by hydrogen evolution and cathodic crystal decomposition. Such centers can be structural defects, Zn‐atoms on the ZnO surface or H‐atoms adsorbed on the surface and possibly also incorporated into the crystal lattice.