Kinetic study of the oxidation of hydrogen sulfide by Fe(III)-Tes=trapolyphosphate (TPP) and Fe(II)-TPP by O^sub 2

Tetrapolyphosphate (TPP) forms complex with iron(III) (Fe(III)-TTP), which is a highly stable catalyst for the air/O2 oxidation of HS- in both the buffered and non-buffered solutions. The first step in this process is formation of the Fe(III)(HS-)TPP complex followed by an electron transfer from HS-...

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Published inApplied catalysis. B, Environmental Vol. 218; p. 186
Main Authors Safarzadeh-Amiri, Ali, Zhang, Ying, El-Din, Mohamed Gamal
Format Journal Article
LanguageEnglish
Published Amsterdam Elsevier BV 05.12.2017
Subjects
Buffers
Catalysts
Confidence limits
Electron transfer
Hydrogen sulfide
Iron
Mathematical analysis
Oxidation
Oxygen
pH effects
Reaction mechanisms
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Summary:Tetrapolyphosphate (TPP) forms complex with iron(III) (Fe(III)-TTP), which is a highly stable catalyst for the air/O2 oxidation of HS- in both the buffered and non-buffered solutions. The first step in this process is formation of the Fe(III)(HS-)TPP complex followed by an electron transfer from HS- to Fe(III) and formation of Fe(II)TPP and HS·. The electron transfer process depends on the half-wave potential (E1/2) of the complex. The E1/2 of Fe(III)/(II)TPP was measured electrochemically and it was found to decrease from 0.061 to -0.14 V vs. SHE (standard hydrogen electrode) with increasing solution pH from 4 to 9. The oxidation of Fe(II)TPP by O2 is shown to follow a four-step reaction mechanism, and the reaction kinetic parameters were calculated using experimental data. The second-order rate constant of the reaction between Fe(III)TPP and HS- at pH 9 was found -- within 95% confidence limit -- to be about 30.5 ± 21.0 M-1s-1. This study provided valuable information about the oxidation characteristics of Fe(II)TPP by O2 and the capability of Fe(III)TPP as a catalyst for the air/O2 oxidation of HS-.
ISSN:0926-3373
1873-3883