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
tities/deg.gif">. 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 
ta.gif" BORDER=0 >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.
tities/deg.gif">. 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 ta.gif" BORDER=0 >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.