Complexing Capacity of Different Molecular Weight Fractions of Sedimentary Humic Substances

Antonelli, Michela; Calace, N.; Centioli, Damiano; Petronio, B.M.; Pietroletti, Marco

doi:10.1081/al-100103608

Cited by 13 publications

(10 citation statements)

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“…In particular, metals captured by humic acids, which are not soluble in water, could be definitively subtracted from the environment. [7][8][9][10][11] We found that the sedimentary humic acids in Antarctic marine environment have some peculiar characteristics such as a high nitrogen (4-8%) and oxygen content (35-45%) and a predominance of carboxylated and hydroxylated aliphatic structures respect to those found in sedimentary humic acids in temperate zone of the planet (N and O ranges are 1-3% and 30-40%, respectively). 12,13 These structural features make Antarctic humic acids particularly interesting to study their role in biogeochemical cycles of metals.…”

Section: Introductionmentioning

confidence: 79%

Copper and other trace elements strongly bound to humic acids along sediment cores in the Ross Sea, Antarctica

et al. 2005

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Marine sediment cores sampled in three different areas, during the 1997/98 Italian Antarctic Expedition, were studied. The cores (40 cm) were immediately subdivided into 13 or 14 layers (2-4 cm) in order to obtain a high-depth resolution in the metal content and humic substance analyses. The results obtained for the amount of metals strongly bound to humic acids showed the following order: Cu >> Zn >> Co > As >or= Mn. The fraction of Cu, Zn and As bound to humic acid (microg g(-1) of HA) increases in the first 10-12 cm of cores, then a decrease is observed. This observation could be related both to the presence of a mobile fraction of metals in sediments successively bound to humic acids and to different structural features showed by humic acids along the cores, due to transformation processes. For the other metals a variable pattern along the cores was found.

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Section: Introductionmentioning

confidence: 79%

Copper and other trace elements strongly bound to humic acids along sediment cores in the Ross Sea, Antarctica

et al. 2005

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“…Cu(II) binding capacity was measured by incremental addition of 25-125 µL of standard Cu(II) solution (9.45×10 -3 mol L -1 ) at pH 5.0 to obtain a total Cu(II) concentration in the range 0.0-1.5×10 -4 mol L -1 . The pH was maintained constant by the addition of standard KOH to neutralize protons released in the coordination reaction and those added via acidic Cu(II) solution [11,13].…”

Section: Ion Selective Electrode (Ise) Proceduresmentioning

confidence: 99%

Tangential-flow ultrafiltration: a versatile methodology for determination of complexation parameters in refractory organic matter from Brazilian water and soil samples

et al. 2003

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In this work the copper(II) complexation parameters of aquatic organic matter, aquatic and soil humic substances from Brazilian were determined using a new versatile approach based on a single-stage tangential-flow ultrafiltration (TF-UF) technique (cut-off 1 kDa) and sensitive atomic spectrometry methods. The results regarding the copper(II) complexation capacity and conditional stability constants obtained for humic materials were compared with those obtained using direct potentiometry with a copper-ion-selective electrode. The analytical procedure based on ultrafiltration is a good alternative to determine the complexation parameters in natural organic material from aquatic and soil systems. This approach presents additional advantages such as better sensibility, applicability for multi-element capability, and its possible to be used under natural conditions when compared with the traditional ion-selective electrode.

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“…Humic and fulvic acids were dissolved in Tris buffer solution (pH = 9.61) and then the pH value was adjusted to 7 by HNO 3 . Enthalpy measurements were made at 25 • C. Antonelli et al [21,22] used calorimetry to determine the binding capacity of fractionated humic acids and fulvic acids towards Cu 2+ ions and the heat of reaction in the complexation of copper ions with small molecules containing functional groups similar to fulvic acid. A copper(II) solution was adjusted to pH = 5, and humic and fulvic acids were adjusted to different pH values (between 5 and 9) by NaOH and HNO 3 ; solutions of small molecules had a pH equal to 5 and 7.…”

Section: Introductionmentioning

confidence: 99%

“…A copper(II) solution was adjusted to pH = 5, and humic and fulvic acids were adjusted to different pH values (between 5 and 9) by NaOH and HNO 3 ; solutions of small molecules had a pH equal to 5 and 7. Measurements were carried out at 25 • C [21,22]. Qi et al [23] determined negative values for the change in Gibbs free energy and positive values for enthalpy change and entropy change (revealing that copper sorption was spontaneous) for interactions of Cu 2+ ions with organic matter from the decomposition of rice straw.…”

Section: Introductionmentioning

confidence: 99%

“…Other functional groups can be possible ligands, although they are less prevalent. It is known that dissolved humic substances such as fulvic acids can easily bind metal ions due to their higher content of ionizable functional groups (supporting their solubility) and more accessible binding sites in a water environment [21,42,[47][48][49][50][51][52][53]. On the other hand, metal ions are also able to bind with non-ionizable active centres on the surface of solid humic particles as was shown in [54] and specific metal ions can interact with humic substances in different ways.…”

Section: Introductionmentioning

confidence: 99%

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Physico-Chemical Aspects of Metal–Fulvic Complexation

Klučáková,

Krouská,

Kalina

2024

Processes

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The interactions of metal ions with fulvic acids were investigated from the point of view of the thermodynamic aspects of complexation as well as the size and charge of the formed complexes. Thermodynamic aspects were studied by means of isothermal titration calorimetry. Particle size distribution was determined by the method of dynamic light scattering and charge by the measurement of zeta potential. Complexation resulted in changes in particle size and charge. The particle size distribution was trimodal for fulvic acids and bimodal for fulvic complexes with calcium and magnesium, while copper–fulvic complexes had only one size fraction. The compensation of the negative charge of carboxylic and phenolic functional groups by positively charged metal ions resulted in an increase in zeta potential which became closer to zero in the case of copper–fulvic complexes. However, all metal–humic complexes behaved as colloidally unstable, which resulted in visually observable sedimentation. Calorimetric measurements provided positive values for changes in enthalpy, which indicated endothermic processes. In contrast, quantum chemical calculations as well as experiments with model compounds provided negative values indicating exothermic processes. Changes in Gibbs energy were determined as negative and changes in entropy as positive.

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Complexing Capacity of Different Molecular Weight Fractions of Sedimentary Humic Substances

Cited by 13 publications

References 13 publications

Copper and other trace elements strongly bound to humic acids along sediment cores in the Ross Sea, Antarctica

Copper and other trace elements strongly bound to humic acids along sediment cores in the Ross Sea, Antarctica

Tangential-flow ultrafiltration: a versatile methodology for determination of complexation parameters in refractory organic matter from Brazilian water and soil samples

Physico-Chemical Aspects of Metal–Fulvic Complexation

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