Reactivity of Ferric Oxides toward H2S at Low pH
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- 作者：Stefan Peiffer ; Winfried Gade
- 刊名：Environmental Science & Technology
- 出版年：2007
- 出版时间：May 1, 2007
- 年：2007
- 卷：41
- 期：9
- 页码：3159 - 3164
- 全文大小：142K
- 年卷期：v.41,no.9(May 1, 2007)
- ISSN：1520-5851
文摘
Goethite (gt), 2-line (2lfh), 6-line ferrihydrite (6lfh), andschwertmannite (shm) were reacted with H2S under steady-state conditions at pH 2.5-5 using a novel setup thatconsisted of an electrochemical sulfide generator transportingH2S into a suspension of oxides in a fluidized bed-reactor. The reactants were stoichiometrically convertedinto Fe2+ and S
. Sulfate significantly inhibited the rates.Surface area normalized rates increased with pH. Theydepended on the mineral type following the order gt > 2lfh> 6lfh, contrasting previous observations at circumneutralpH with an inverse order. The rate of shm dissolutionwas highest probably due to direct reduction of dissolvedferric iron by H2S. A linear relationship between theobserved rate and the surface species of H2S was derivedfrom a surface complexation approach that allowed forthe estimation of intrinsic rate constants kintr for the variousoxides (38 min-1, 1.4 min-1, 0.29 min-1 for gt, 2lfh, and6lfh, respectively). kint decreased with increasing 
Gf forthe reactions and seems to depend on the reduction potentialof the solution. From this observation we derived thehypothesis that kint is determined by the flat-band potentialof the mineral/solute interface at low pH while beingaffected by surface interactions at higher pH.
. Sulfate significantly inhibited the rates.Surface area normalized rates increased with pH. Theydepended on the mineral type following the order gt > 2lfh> 6lfh, contrasting previous observations at circumneutralpH with an inverse order. The rate of shm dissolutionwas highest probably due to direct reduction of dissolvedferric iron by H2S. A linear relationship between theobserved rate and the surface species of H2S was derivedfrom a surface complexation approach that allowed forthe estimation of intrinsic rate constants kintr for the variousoxides (38 min-1, 1.4 min-1, 0.29 min-1 for gt, 2lfh, and6lfh, respectively). kint decreased with increasing Gf forthe reactions and seems to depend on the reduction potentialof the solution. From this observation we derived thehypothesis that kint is determined by the flat-band potentialof the mineral/solute interface at low pH while beingaffected by surface interactions at higher pH.