METAL-FULVIC ACID CHELATION EQUILIBRIUM IN AQUEOUS NaNO<sub>3</sub> SOLUTION. Hg(II), Cd(II), AND Cu(II) FULVATE COMPLEXES

Cheam, Venghuot; Gamble, Donald S.

doi:10.4141/cjss74-055

Cited by 69 publications

(19 citation statements)

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“…Finally, wetlands typically have very high concentrations of organic matter due to the slow rate of organic matter oxidative degradation occurring in this environment. The organic matter may either act as a sorbent or may provide high concentrations of dissolved ligands that form very strong complexes to Hg(II) (Cleam and Gamble 1974;Wallschlager et al 1998b). …”

Section: Introductionmentioning

confidence: 99%

Mercury Geochemistry in Wetland and its Implications for In Situ Remediation

2002

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The objective of this study was to characterize the nature of Hg sorption on a wetland sediment with the intent of providing guidance for the selection of an appropriate in-situ remediation strategy. Total Hg concentrations in the sediments were as high as 10-mg/kg, whereas associated pore water Hg concentrations were below detection, <0.010-mg/L. Sediment Hg was not in an exchangeable form, and <8% of it was associated with organic matter. The remainder of the Hg was strongly associated with Feoxides and/or with a precipitated phase, presumably a sulfide. Sediment Hg concentrations were significantly correlated (r = 0.94) to Fe-oxide concentrations. Thermodynamic calculations based on field Eh/pH measurements and laboratory results suggest that under present field conditions metacinnabar (HgS) would not be stable due to the relatively low pH (~4.2) and sulfate concentrations (0.14-mM) and high Eh levels at the study site. However, these calculations indicate that meta-cinnabar may have formed when the Hg first entered the wetland at elevated concentrations (~5-mg/L). Given the ecologically sensitive nature of the wetland and the fact that the Hg is strongly bound to the sediment, it was concluded that a monitored natural attenuation approach for site remediation may be appropriate.

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Section: Introductionmentioning

confidence: 99%

Mercury Geochemistry in Wetland and its Implications for In Situ Remediation

2002

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“…The decrease in the stability of complexes of copper ions with the WSOS ligands of the second type was caused by the acidification of solutions at their formation. The stability constants of metal complexes with natural ligands can decrease by orders of magnitude with decreasing pH (Cheam & Gamble, 1974; Saar & Weber, 1979). We assume that the main reason for the decrease in the stability of complexes of copper ions with the WSOS ligands of the second type was the acidification of the solution, because bond formation with protons is easier than that with Cu 2+ ions.…”

Section: Resultsmentioning

confidence: 99%

Contribution of metal‐ion complex formation with organic substances to the acidity of water extracts of polluted soils

Motuzova

Makarychev

Barsova

2012

European J Soil Science

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The formation of complexes of copper ions with organic substances in soil water extracts and the development of acid–base properties of the extracts were examined. Potentiometric titration of water extracts from several soils with copper nitrate solution with a consecutive determination of the activity of protons and copper ions in the extracts was performed. This demonstrated the existence of a functional relationship between the complexing of copper ions with organic substances and the acid–base properties of the water extracts. The parameters of the interrelated processes of formation and dissociation of metal–organic complexes and the protonation‐deprotonation of organic acids, the ligands of which participate in the complexing reactions, were determined. It was found that the formation of the complexes is accompanied by the acidification of the solution from the acid hydrolysis of the copper ions and the displacement of protons from the functional groups of organic acids. The protons released in the course of complexing reactions affected these reactions. Under their impact, the stability of the copper–organic complexes decreased; finally, the formation of the complexes and the release of protons stopped, and the pH of the extracts reached an equilibrium level.

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“…18,20 Dissociation constants of humic acid vary within a broad range and in the acidic region the formation of positively charged amide-and carbamide-sites occurs. 31 Since the pioneering works of SCHNITZER 32,33 and STEVENSON 34-36 on metal humates, and CHOPPIN'S on radionuclides, 19 the complexation of radionuclides with humic substances has usually been modeled as quasiparticle, chemical interactions [8][9][10]12,19,20,24,28,29,[37][38][39][40][41][42][43][44][45][46][47] but electrostatic (Donnan) effects were also applied.6, t o, 11,48-5 t In the present work, the former approach, and also chemisorption in the presence of humificied surfaces, is concisely analyzed. 29,30 It was confirmed that important sites are likely to be phthalate-, salicylate= and also acetylacetone-type sites, but computed binding strengths were consistently less than those obtained by experiment.…”

Section: Introductionmentioning

confidence: 99%

Complexation of radionuclides with natural polyelectrolytes — proteins, polysaccharides and humic substances

Macášek

1999

J Radioanal Nucl Chem

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Various approaches to the modeling of metal and radionuclide interactions with macromolecular ligands, proteins, polysaccharides and humic substances in particular, their chemical and sorption equilibria, and the techniques used for their investigation are concisely compared. To predict radionuclide mobility in the natural and semi-natural aqueous environment, the estimation of the effective interaction constants, related to specific species of polyelectrolytes which are linked with the absorbancy or absorbancy ratio in their electronic absorption spectra, should probably be preferred and developed as standard. For characterization of the binding sites of specific molecular forms of polyelectrolyte ligands, the Scatchard plot analysis at macroconcentrations of the metal and also, though not so effectively, the two-phase distribution at trace concentrations of radionuclide or metal can be applied. 0236-5731/99/USD 17.00 9 1999 Akad~miai Kiadd, Budapest All rights reserved Elsevier Science B, V., Amsterdam Akad~miai Kiada, Budapest

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METAL-FULVIC ACID CHELATION EQUILIBRIUM IN AQUEOUS NaNO₃ SOLUTION. Hg(II), Cd(II), AND Cu(II) FULVATE COMPLEXES

Cited by 69 publications

References 1 publication

Mercury Geochemistry in Wetland and its Implications for In Situ Remediation

Mercury Geochemistry in Wetland and its Implications for In Situ Remediation

Contribution of metal‐ion complex formation with organic substances to the acidity of water extracts of polluted soils

Complexation of radionuclides with natural polyelectrolytes — proteins, polysaccharides and humic substances

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METAL-FULVIC ACID CHELATION EQUILIBRIUM IN AQUEOUS NaNO3 SOLUTION. Hg(II), Cd(II), AND Cu(II) FULVATE COMPLEXES

Cited by 69 publications

References 1 publication

Mercury Geochemistry in Wetland and its Implications for In Situ Remediation

Mercury Geochemistry in Wetland and its Implications for In Situ Remediation

Contribution of metal‐ion complex formation with organic substances to the acidity of water extracts of polluted soils

Complexation of radionuclides with natural polyelectrolytes — proteins, polysaccharides and humic substances

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METAL-FULVIC ACID CHELATION EQUILIBRIUM IN AQUEOUS NaNO₃ SOLUTION. Hg(II), Cd(II), AND Cu(II) FULVATE COMPLEXES