The effect of Cobalt on the Kinetics of Oxygen evolution at a Lead Dioxide anode in Sulphuric Acid

1959 ◽  
Vol 12 (2) ◽  
pp. 127 ◽  
Author(s):  
DFA Koch
Keyword(s):  
Sulphuric Acid ◽  
Oxygen Evolution ◽  
Current Density ◽  
Lead Dioxide ◽  
Kinetic Constants ◽  
Kcal Mole ◽  
Lead Dioxide Anode ◽  
Kinetics Of ◽  
Evolution Of Oxygen ◽  
Rate Determining Steps

The overpotential (n)-log current density (log i) curves for the evolution of oxygen at a lead dioxide anode in 2N H2SO4 both in the absence and presence of cobaltous sulphate in solution have been used to determine the electrode kinetic constants α ; i0 for a series of temperatures and also ΔH0*:. At 25 �C in the absence of cobalt α=O.59, i0= 10-11, and ΔH0*= 15 kcal mole-1 When 13 mg/l cobaltous sulphate is added α= 1.0, i0= 10-15, and ΔH0*:=29 kcal mole-1. Possible mechanisms for the reaction are discussed on the basis of these values and the rate determining steps suggested (where M represents the PbO2 surface) are M +H2O =MOH +H+ +e in the absence of cobalt and 2CoOH++ = 2Co++ +H2O + O in its presence.

Effect of various cations on the initial rate of formation of peroxodisulphates

1980 ◽  
Vol 45 (8) ◽  
pp. 2272-2282 ◽  
Author(s):  
Jan Balej ◽  
Martin Kadeřávek
Keyword(s):  
Sulphuric Acid ◽  
Oxygen Evolution ◽  
Anodic Polarization ◽  
Initial Rate ◽  
Degree Of Conversion ◽  
Polarization Curves ◽  
Mixed Solutions ◽  
Low Degree ◽  
Partial Polarization

Preparation of peroxodisulphates by electrolysis of mixed solutions of sulphuric acid and various sulphates was studied at low degree of conversion; the partial polarization curves of peroxodisulphate formation and of oxygen evolution obtained from the overall anodic polarization curves and current yields of the principal anodic processes were examined. The mechanism of the effect of various cations on the rate of anodic formation of peroxodisulfates is discussed.

Kinetics and mechanism of the reaction of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione

1990 ◽  
Vol 55 (8) ◽  
pp. 1984-1990 ◽  
Author(s):  
José M. Hernando ◽  
Olimpio Montero ◽  
Carlos Blanco
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Activation Parameters ◽  
Enol Form ◽  
Kinetics And Mechanism ◽  
Kinetic Constants ◽  
Steric Factors ◽  
Kinetics Of ◽  
Mechanism Of The Reaction

The kinetics of the reactions of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione to form the corresponding monocomplexes have been studied spectrophotometrically in the range 5 °C to 16 °C at I 25 mol l-1 in aqueous solution. In the proposed mechanism for the two complexes, the enol form reacts with the metal ion by parallel acid-independent and inverse-acid paths. The kinetic constants for both pathways have been calculated at five temperatures. Activation parameters have also been calculated. The results are consistent with an associative activation for Fe(H2O)63+ and dissociative activation for Fe(H2O)5(OH)2+. The differences in the results for the complexes of heptanediones studied are interpreted in terms of steric factors.

Comparative investigation on the removal of methyl orange from aqueous solution using three different advanced oxidation processes

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zahia Benredjem ◽  
Karima Barbari ◽  
Imene Chaabna ◽  
Samia Saaidia ◽  
Abdelhak Djemel ◽  
...  
Keyword(s):  
Methyl Orange ◽  
Current Density ◽  
Advanced Oxidation Processes ◽  
Degradation Rate ◽  
Supporting Electrolyte ◽  
Advanced Oxidation ◽  
Comparative Investigation ◽  
Oxidation Processes ◽  
The Comparative Study ◽  
Kinetics Of

Abstract The Advanced Oxidation Processes (AOPs) are promising environmentally friendly technologies for the treatment of wastewater containing organic pollutants in general and particularly dyes. The aim of this work is to determine which of the AOP processes based on the Fenton reaction is more effective in degrading the methyl orange (MO) dye. The comparative study of the Fenton, photo-Fenton (PF) and electro-Fenton (EF) processes has shown that electro-Fenton is the most efficient method for oxidizing Methyl Orange. The evolution of organic matter degradation was followed by absorbance (discoloration) and COD (mineralization) measurements. The kinetics of the MO degradation by the electro-Fenton process is very rapid and the OM degradation rate reached 90.87% after 5 min. The influence of some parameters such as the concentration of the catalyst (Fe (II)), the concentration of MO, the current density, the nature and the concentration of supporting electrolyte was investigated. The results showed that the degradation rate increases with the increase in the applied current density and the concentration of the supporting electrolyte. The study of the concentration effect on the rate degradation revealed optimal values for the concentrations 2.10−5 M and 75 mg L−1 of Fe (II) and MO respectively.

The Lead Dioxide Anode. II. The Kinetics and Participation of the Lead Dioxide Electrode in Electrochemical Oxidation Reactions in Sulfuric Acid

1989 ◽  
Vol 42 (9) ◽  
pp. 1527 ◽  
Author(s):  
TH Randle ◽  
AT Kuhn
Keyword(s):  
Sulfuric Acid ◽  
Electrochemical Oxidation ◽  
Maximum Rate ◽  
Lead Dioxide ◽  
Chemical Oxidation ◽  
Oxidation Reactions ◽  
Electrochemical Regeneration ◽  
Electrode Surfaces ◽  
Lead Dioxide Electrode ◽  
Lead Dioxide Anode

Lead dioxide is a strong oxidizer in sulfuric acid, consequently electrochemical oxidation of solution species at a lead dioxide anode may occur by a two-step, C-E process (chemical oxidation of solution species by PbO2 followed by electrochemical regeneration of the reduced lead dioxide surface). The maximum rate of each step has been determined in sulfuric acid for specified lead dioxide surfaces and compared with the rates observed for the electrochemical oxidation of cerium(III) and manganese(II) on the same electrode surfaces. While the rate of electrochemical oxidation of a partially reduced PbO2 surface may be sufficient to support the observed rates of CeIII and MnII oxidation at the lead dioxide anode, the rate of chemical reaction between PbO2 and the reducing species is not. Hence it is concluded that the lead dioxide electrode functions as a simple, 'inert' electron-transfer agent during the electrochemical oxidation of CellI and MnII in sulfuric acid. In general, it will most probably be the rate of the chemical step which determines the feasibility or otherwise of the C-E mechanism.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

scholarly journals Photosystem II: Thermodynamics and Kinetics of Electron Transport from QA- to QB(QB- ) and Deleterious Effects of Copper(II)

1993 ◽  
Vol 48 (3-4) ◽  
pp. 234-240 ◽  
Author(s):  
G. Renger ◽  
H. M. Gleiter ◽  
E. Haag ◽  
F. Reifarth
Keyword(s):  
Oxygen Evolution ◽  
Manganese Content ◽  
Fluorescence Emission ◽  
Laser Flash ◽  
Fluorescence Induction ◽  
Oxygen Evolving Complex ◽  
Ps Ii ◽  
Thermodynamics And Kinetics ◽  
Redox Active ◽  
Kinetics Of

Studies on thermodynamics and kinetics of electron transfer from QA- to QB(QB-) were performed by monitoring laser flash induced changes of the relative fluorescence emission as a function of temperature (220 K < T < 310 K) in isolated thylakoids and PS II membrane fragments.In addition, effects of bivalent metal ions on PS II were investigated by measuring conventional fluorescence induction curves, oxygen evolution, manganese content and atrazine binding mostly in PS II membrane fragments. It was found: a) the normalized level of the fluorescence remaining 10 s after the actinic flash (Ft/F0) steeply increases at temperatures below -10 to - 20 °C, b) the fast phase of the transient fluorescence change becomes markedly retarded with decreasing temperatures, c) among different cations (Cu2+, Zn2+, Cd2+, Ni2+, Co2+) only Cu2+ exhibits marked effects in the concentration range below 100 μᴍ and d) Cu2+ decreases the normalized variable fluorescence, inhibits oxygen evolution and diminishes the affinity to atrazine binding without affecting the number of binding sites. The content of about four manganeses per functionally competent oxygen evolving complex is not changed by [Cu2+] < 70 μᴍ.Based on these findings it is concluded: i) a temperature dependent equilibrium between an inactive (I) and active (A) state of QA- reoxidation by QB(QB- ) is characterized by standard enthalpies ΔH° of 95 kJ mol-1 and 60 kJ mol-1 and standard entropies ΔS° of 370 kJ K-1 mol-1 and 240 kJ K-1 mol-1 in isolated thylakoids and PS II membrane fragments, respectively, ii) the activation energies of QA- reoxidation by plastoquinone bound to the QB site are about 30 kJ mol-1 (thylakoids) and 40 kJ mol-1 (PS II membrane fragments) in 220 K < T < 300 K, and iii) Cu2+ causes at least a two-fold effect on PS II by modifying the atrazine binding affinity at lower concentrations ( ~ 5 μᴍ) and interference with the redox active tyrosine Yz at slightly higher concentration ( ~ 10 μᴍ) leading to blockage of oxygen evolution.

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