TY  - JOUR
AU  - Rennert, T.
AU  - Pohlmeier, A.
AU  - Mansfeld, T.
TI  - Oxidation of Ferrocyanide by Birnessite
JO  - Environmental Science & Technology
VL  - 39
SN  - 0013-936X
CY  - Columbus, Ohio
PB  - American Chemical Society
M1  - PreJuSER-53450
SP  - 821 - 825
PY  - 2005
N1  - Record converted from VDB: 12.11.2012
AB  - The Fe-CN complexes ferrocyanide, [Fe-II(CN)(6)](4-), and ferricyanide, [Fe-III(CN)(6)](3-), which are contaminants in soil and groundwater, form a redox couple, [Fe-II(CN)(6)](4-) reversible arrow [Fe-III(CN)(6)](3-) + e(-), E-H = 356 mV. We studied the oxidation of [Fe-II(CN)(6)](4-) by birnessite, delta-(MnO2)-O-IV, in batch experiments as influenced by [Fe-II(CN)(6)](4-) concentration, pH, and reaction time. Additionally, stopped-flow experiments were carried out at five temperatures (10-30 degreesC) and four pH values (pH 4.1-5.3). In the batch experiments, [Fe-II(CN)(6)](4-) was completely oxidized to [Fe-III(CN)(6)](3-), and oxidation did neither depend on time for t > 2 min, nor on concentration (0.12-0.47 mM), nor on pH (pH 3.3-9.9). Lasting adsorption of Fe-CN complexes on the birnessite surface or precipitation of manganese ferricyanide were not detected. Manganous ions resulting from the reductive dissolution of birnessite did not precipitate as manganese oxide because an identical decrease of Mn solution concentrations was observed under air and under a N-2 atmosphere. Two processes were detected by the stopped-flow experiments. The first rapid one with an activation energy of approximately 60 kJ mol(-1) was attributed to short-term adsorption and simultaneous oxidation of [Fe-II(CN)(6)](4-) on the birnessite surface. The second slower process with an activation energy of approximately 20 kJ mol(-1) was attributed most probably to diffusion of the reaction product Mn2+ into the interior of the birnessite, which creates fresh reaction sites at the outer surface.
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000226712600030
DO  - DOI:10.1021/es040069x
UR  - https://juser.fz-juelich.de/record/53450
ER  -