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Kinetic speciation of mercury–humate complexes in aqueous solutions by using competing ligand exchange method
DRS at CSIR-National Institute of Oceanography
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| Title |
Kinetic speciation of mercury–humate complexes in aqueous solutions by using competing ligand exchange method
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| Creator |
Vudamala, K.
Chakraborty, P. |
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| Subject |
AQUATIC POLLUTION
CHEMISTRY AND BIOGEOCHEMISTRY CHEMISTRY AND BIOGEOCHEMISTRY |
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| Description |
Competing ligand exchange method (CLEM) in conjunction with direct mercury analyzer (DMA) was found to be a useful method for kinetic speciation study of (mercury–humic acid) Hg–HA complexes in aqueous systems. Ambersep GT74 (containing a thiol functional group) was used as a suitable competing ligand for this study. The CLEM/DMA was used to estimate lability and dissociation rate constant of Hg–HA complexes in aquatic systems. Influences of pH, metal loading and varying major cation (Ca2+) concentrations on Hg–HA complexes were investigated. Concentration of dynamic Hg–HA complexes gradually increased with increasing Hg loading in the system. The dissociation rate constant (kd1) of labile Hg–HA complexes were found to vary from 4.3 × 10-3 s-1 to 9.2 × 10s-3 s-1 with increasing Hg loading from 1.0 × 10-8 M to 1.42 × 10-7 M. The concentrations of Hg–HA complexes with low thermodynamic stability were found to be similar at pH 4 and 5 (~ 59% and 58% of the total Hg with kd1 values of ~2 × 10-1 and 1.7 × 10-3 s-1, respectively). The complexation of Hg with HA was found to increase with increasing pH from 4 to 7. The concentration of inert complexes (c2) with dissociation rate constant (kd2) gradually increased with increasing pH. Increasing concentration of Ca2+ in the model solutions increased the concentrations of Hg–HA dynamic complexes in the system. This finding suggests that the Hg–HA bond is predominantly ionic in nature. It suggests that Ca2+ ions screen out Hg2+ ions from undergoing complexation reaction with HA.
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| Date |
2016-03-09T09:32:06Z
2016-03-09T09:32:06Z 2016 |
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| Type |
Journal Article
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| Identifier |
Microchemical Journal, vol.126; 2016; 551-557
no http://drs.nio.org/drs/handle/2264/4924 |
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| Language |
en
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| Relation |
Microchem_J_126_551.jpg
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| Rights |
An edited version of this paper was published by Elsevier. Copyright [2016] Elsevier
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| Publisher |
Elsevier
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