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Copper(II) Complexation by Fulvic Acid Extracted From Sewage Sludge as Influenced by Nitrate Versus Perchlorate Background Ionic Media
Author(s) -
Sposito Garrison,
Holtzclaw Kenneth M.
Publication year - 1979
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1979.03615995004300010008x
Subject(s) - chemistry , potentiometric titration , perchlorate , titration , stability constants of complexes , inorganic chemistry , copper , ionic bonding , ion , sewage sludge , nitrate , potassium nitrate , nuclear chemistry , sewage , potassium , organic chemistry , engineering , waste management
The possible adverse effect of CuNO 3 + ion pairs on studies of the complexes formed between Cu(II) and fulvic acid extracted from sewage sludge was investigated by potentiometric titration of 2 × 10 −3 M K/H fulvate with Cu(NO 3 ) 2 and Cu(C10 4 ) 2 , at pH 5 and 25°C, in ionic media of 0.1 M KNO 3 or KC10 4 , respectively. It was shown that the degree of complexation of Cu 2+ in the NO 3 medium was always significantly greater than that in the C10 4 medium for total Cu concentrations in the range 10 −4 M to 10 −2 M . This result was interpreted as evidence for significant concentrations of CuNO 3 + ion pairs and mixed CuNO 3 ‐fulvate complexes in the NO 3 medium. Further support for the existence of CuNO 3 + in the NO 3 medium was obtained through a successful calculation of the thermodynamic stability constant for this ion pair that employed data from blank titrations with Cu(NO 3 ) 2 and Cu(ClO 4 ) 2 . It was concluded that ClO 4 ionic media should be used instead of NO 3 ionic media in studies of Cu(II) complexation with the functional groups of fulvic acid.