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Sorption of iron‐cyanide complexes on goethite investigated in long‐term experiments
Author(s) -
Rennert Thilo,
Kaufhold Stephan,
Mansfeldt Tim
Publication year - 2005
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/jpln.200421602
Subject(s) - ferricyanide , goethite , chemistry , sorption , ferrocyanide , inorganic chemistry , cyanide , desorption , fourier transform infrared spectroscopy , phosphate , inner sphere electron transfer , ferrihydrite , nuclear chemistry , adsorption , organic chemistry , ion , chemical engineering , electrode , engineering
Abstract The iron‐cyanide complexes ferrocyanide, [Fe II (CN) 6 ] 4– , and ferricyanide, [Fe III (CN) 6 ] 3– , are anthropogenic contaminants in soil. We investigated their sorption on goethite, α‐FeOOH, in batch experiments in a time range from 1 d to 1 yr, their desorption by phosphate and chloride as well as their surface complexes on goethite by Fourier‐transform infrared spectroscopy (FTIR). The sorption of both complexes continued over the whole time range. Percent desorption of ferricyanide by phosphate decreased, whereas that of ferrocyanide increased until it amounted to approximately 87% for both complexes. By FTIR spectroscopy inner‐sphere complexation of both complexes on the goethite surface was indicated. With both complexes, a Berlin‐Blue‐like layer (Fe 4 [Fe(CN) 6 ] 3 ) was formed initially on the goethite surface which disappeared with increasing reaction time. After at least 30 d reaction time, ferricyanide was the only sorbed iron‐cyanide complex detected even when ferrocyanide was initially added. This resulted from slow oxidation of ferrocyanide, most probably by dissolved oxygen. Based on all results, we propose that ferricyanide forms monodentate inner‐sphere complexes on the goethite surface.