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dc.contributor.authorVudamala, K.
dc.contributor.authorChakraborty, P.
dc.date.accessioned2016-03-09T09:32:06Z
dc.date.available2016-03-09T09:32:06Z
dc.date.issued2016
dc.identifier.citationMicrochemical Journal, vol.126; 2016; 551-557
dc.identifier.otherno
dc.identifier.urihttp://drs.nio.org/drs/handle/2264/4924
dc.description.abstractCompeting 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 (Ca<sup>2+</sup>) 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 (k<sub>d1</sub>) of labile Hg–HA complexes were found to vary from 4.3 × 10<sup>-3</sup> s<sup>-1</sup> to 9.2 × 10s<sup>-3</sup> s<sup>-1</sup> with increasing Hg loading from 1.0 × 10<sup>-8</sup> M to 1.42 × 10<sup>-7</sup> 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 k<sub>d1</sub> values of ~2 × 10<sup>-1</sup> and 1.7 × 10<sup>-3</sup> s<sup>-1</sup>, respectively). The complexation of Hg with HA was found to increase with increasing pH from 4 to 7. The concentration of inert complexes (c<sub>2</sub>) with dissociation rate constant (k<sub>d2</sub>) gradually increased with increasing pH. Increasing concentration of Ca<sup>2+</sup> 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 Ca<sup>2+</sup> ions screen out Hg<sup>2+</sup> ions from undergoing complexation reaction with HA.
dc.language.isoen
dc.publisherElsevier
dc.relation.requiresMicrochem_J_126_551.jpg
dc.rightsAn edited version of this paper was published by Elsevier. Copyright [2016] Elsevier
dc.subjectAQUATIC POLLUTION
dc.subjectCHEMISTRY AND BIOGEOCHEMISTRY
dc.subjectCHEMISTRY AND BIOGEOCHEMISTRY
dc.titleKinetic speciation of mercury–humate complexes in aqueous solutions by using competing ligand exchange method
dc.typeJournal Article


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