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Simple modelling of the sorption of iron‐cyanide complexes on ferrihydrite
Author(s) -
Rennert Thilo,
Mansfeldt Tim
Publication year - 2001
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200112)164:6<651::aid-jpln651>3.0.co;2-6
Subject(s) - sorption , ferrihydrite , ferricyanide , ferrocyanide , chemistry , ionic strength , cyanide , inorganic chemistry , adsorption , nuclear chemistry , aqueous solution , organic chemistry , electrode
The sorption of the iron‐cyanide complexes ferricyanide, [Fe(CN) 6 ] 3— , and ferrocyanide, [Fe(CN) 6 ] 4— , on ferrihydrite was investigated in batch experiments including the effects of pH (pH 3.5 to 8) and ionic strength (0.001 to 0.1 M). The pH‐dependent sorption data were evaluated with a model approach by Barrow (1999): c = a exp(bS)S/(S max ‐S), where c is the solution concentration; S is the sorbed amount; S max is maximum sorption; b is a parameter; and a is a parameter at constant pH. Ferricyanide sorption was negatively affected by increasing ionic strength, ferrocyanide sorption not at all. More ferricyanide than ferrocyanide was sorbed in the acidic range. In the neutral range the opposite was true. Fitting the pH‐dependent sorption to the model resulted in a strong correlation for both iron‐cyanide complexes with a common sorption maximum of 1.6 μmol m —2 . Only little negative charge was conveyed to the ferrihydrite surface by sorption of iron‐cyanide complexes. The sorption of iron‐cyanide complexes on ferrihydrite is weaker than that on goethite, as a comparison of the model calculations shows. This may be caused by the lower relative amount of high‐affinity sites present on the ferrihydrite surface.