Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6453714 | Applied Catalysis B: Environmental | 2017 | 6 Pages |
â¢Fe(III)-tetrapolyphosphate(TTP) is a highly stable catalyst for the air/O2 oxidation of HSâ in buffered/non-buffered solutions.â¢The complex catalyzes eâ-transfer from HSâ to O2, which depends on the E1/2 (varies from 0.061 to â0.14 V vs. SHE as pH varied from 4-9) of Fe(III)-TPP.â¢The Fe(III)TPP catalytic oxidation of HSâ generates Fe(II)TPP, which is oxidized by O2 according to the well know four-step reaction mechanism.â¢The second-order rate constant of the reaction between Fe(III)TPP and HSâ at pH 9 was found to be about 30.5 ± 21.0 Mâ1 sâ1.â¢This study elucidates the kinetics of Fe(II)TPP oxidation by O2 and the capability of Fe(III)TPP as a catalyst for the air/O2 oxidation of HSâ.
Tetrapolyphosphate (TPP) forms complex with iron(III) (Fe(III)-TTP), which is a highly stable catalyst for the air/O2 oxidation of HSâ in both the buffered and non-buffered solutions. The first step in this process is formation of the Fe(III)(HSâ)TPP complex followed by an electrontransfer from HSâ to Fe(III) and formation of Fe(II)TPP and HSâ¢. 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 â0.14 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 HSâ at pH 9 was found â within 95% confidence limit â to be about 30.5 ± 21.0 Mâ1sâ1. 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 HSâ.
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