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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 14, Number 6
BKCSDE 14(6)
June 20, 1993 

Complexation of Cadmium(Ⅱ) with Humic Acids : Effects of pH and Humic Acid Origin
Mee Hae Lee, Se Young Choi, Kun Ho Chung, Hichung Moon*
A comparative study on cadmium(Ⅱ) complexation with three well characterized humic acids (SHA: soil humic acid from the Okchun Metamorphic Belt; AqHA: aquatic humic acid from Gorleben underground aquifer, Germany; CoHA: commercially available humic acid from the Aldrich Co.) was carried out in 0.1 M NaClO4 at different solution pH(5.0, 5.5, and 6.0) using the ultrafiltration technique. The maximum binding ability (MBA) of the humic acids for cadmium(Ⅱ) was observed to vary with their origins and solution pH. The results suggest that 1 : 1 complex predominates within the experimental range, and the conditional stability constants were calculated based on the assumption of cooperative binding, yielding log K values that were quite similar (CoHA: 4.17±0.08; AqHA: 4.14±0.07; SHA: 4.06±0.12 l mol-1 at pH 6.0) irrespective of humic acid origins or pH. By contrast a nonlinear Schatchard plot was obtained, using the cadmium(Ⅱ) ion selective electrode speciation analysis method, which indicated that humic acid may have two or more classes of binding sites, with log K1 and log K2 of 4.73± 0.08 and 3.31±0.14 l mol-1 respectively.
726 - 732
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