Studies on copper(II)- and zinc(II)-mixed ligand complexes of humic acid

Prado, Alexandre G.S.; Torres, Jocilene D.; Martins, Paolla Carminatti; Pertusatti, Jonas; Bolzon, Lucas B.; Faria, Elaine A.

doi:10.1016/j.jhazmat.2005.12.035

Cited by 58 publications

(34 citation statements)

References 16 publications

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“…They correspond to the great amount of organic matter in environment and are generated from natural degradation of biomatter through uncertain routes. [1][2][3][4][5][6] This fact creates chemically heterogeneous compounds, but with some common features as the huge concentration of carboxyl and phenolic groups, which give them the weak acid behavior. HA perform a very important role on environment such as on germination of seeds and plants growth, transport and sorption of hydrophobic compounds, structural aggregation of soil, bioavailability and complexation of metal ions and present buffering capacity on natural environments.…”

Section: Introductionmentioning

confidence: 99%

“…HA perform a very important role on environment such as on germination of seeds and plants growth, transport and sorption of hydrophobic compounds, structural aggregation of soil, bioavailability and complexation of metal ions and present buffering capacity on natural environments. [1][2][3]7 The reactivity of HA on buffering capacity of soils, bioavailability, motion and transport of micro and macronutrients, toxic metal, xenobiotic organic cations in soils and surface waters is strongly influenced by acid-base properties of humic acids. 7,8 These interactions concern to protonation and deprotonation of HA surface acid groups and they are directly related to the structural conformation of HA.…”

Section: Introductionmentioning

confidence: 99%

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Aspects of protonation and deprotonation of humic scid durface on molecular conformation

Prado¹,

Pertusatti²,

Nunes³

2011

J. Braz. Chem. Soc.

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As densidades superficiais de carga de ácidos húmicos foram determinadas por titulação potenciométrica e condutimétrica simultâneas. Também foi observada a influência do pH na conformação molecular através de espectroscopia de UV-Vis e microscopia eletrônica de varredura (MEV). A densidade de carga superficial para todas as amostras de ácido húmico é aproximadamente zero na faixa de pH 3,5-6,0. A influência do pH na condensação molecular foi observada pela determinação do índice b na equação de Doty e Steiner. Os altos valores de b foram obtidos na região ácida, indicando uma conformação condensada, devido à fraca interação atrativa. Além disso, na região alcalina, a densidade de carga na superfície da molécula é mais negativa, o que favorece o aumento da repulsão e dispersão das partículas, levando à formação de estruturas micelares como consequência da característica anfifílica dos ácidos húmicos.The surface charge densities for humic acids (HAs) were determined by simultaneous potentiometric and conductimetric titrations. It was also observed the pH influence on molecular conformation by UV-Vis spectroscopy measurements and scanning electron microscopy (SEM) images. The surface charge densities are approximately zero at the pH range 3.5 to 6.0 for all samples. The pH influence on molecular condensation level was observed by the determination of the b index from Doty and Steiner equation. High values of b were obtained at acid region indicating a condensed conformation due to weak attractive interactions whereas around the neutral region the repulsive intramolecular forces take place leading to an extended conformation of humic molecules. Moreover, at very alkaline region, the charge density on molecule surface is more negative, increasing repulsion and dispersion of the particles and also takes place formation of micelle-like structure because of the amphyphylic feature of HA samples.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aspects of protonation and deprotonation of humic scid durface on molecular conformation

Prado¹,

Pertusatti²,

Nunes³

2011

J. Braz. Chem. Soc.

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“…The interaction of humic matter with the different metal ions changes the biogeochemical cycle of these trace metals and also influences their bioavailability (Plavsic et al 2006). The complexation of trace metal ions with humic acids may lead to decrease in metal toxicity or to increase in solubility (as for iron), thus making the metal ion more available for plant uptake (Prado et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Complexation Study of Humic Acids Extracted from Forest and Sahara Soils with Zinc (II) and Cadmium (II) by Differential Pulse Anodic Stripping Voltammetry (DPASV) and Conductimetric Methods

Terbouche

Djebbar

Benali-Baïtich

et al. 2010

Water Air Soil Pollut

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The complexation of heavy metals, present in their dissolved state at relevant trace levels, with new humic acids (HAs) isolated from Yakouren forest (YHA) and Sahara (Tamenrasset: THA) soils has been studied by differential pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode and conductimetry methods. After extraction and purification, humic acids were characterized by elemental analyses, atomic absorption spectroscopy, FT-IR, and solution state 13 C-NMR. Taking Zn(II) and Cd(II) as examples, the aim of this study was to gain direct information on the general level of importance of humic acids for the speciation of certain heavy metals in soil to determine the complexing capacities of AHs and stability constant of the complexes formed with these metal ions and to compare the complexation capacity of forest and Sahara soils with the commercial humic acid and other published AHs. The results determined by conductimetry method are interpreted using an excess function (Δk) which related the conductivity of the mixture and of the separated components. A positive value of this function is obtained. It indicates the complexation of humic acids with metallic ions. The DPASV method was used for determining metal ion complexing capacities and stability constants of metal ion complexes of HAs in solution at pH 7. In both types of soils, the commercial humic acid (CHA) is less efficient in complexing Zn(II) and Cd(II) than THA and YHA and the complexing capacity (CC M ) decreases in the order: THA > YHA > CHA. In general, the results of complexing capacity for all humic acids and stability constants of Zn(II) and Cd(II) complexes found by DPASV method showed good correlation with those of conductimetry method. CC M of THA and YHA calculated by DPASV were higher than those of CHA and the other natural HAs published in the literature at pH 7 basing on these results.

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“…In particular, the back titration method is applied for qualitative and quantitative analysis of the dependence of variable surface charge (Q) on pH, as well as for evaluation of the distribution functions of apparent surface dissociation constants and the amount of particular functional groups (Campitelli et al, 2006;Gondar et al, 2005;Janos et al, 2008). Electrochemical measurements can be also used to perform the analysis of buffer properties of soils and soil components (Lavelle and Spain, 2002;Garcia-Gil et al, 2004;Pertusatti and Prado, 2007;Prado et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Influence of phosphate ions on buffer capacity of soil humic acids

Boguta¹,

Sokołowska²

2012

International Agrophysics

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Influence of phosphate ions on buffer capacity of soil humic acidsThe object of this study was to determine change of natural buffer capacity of humic acids by strong buffering agents, which were phosphate ions. Studies were carried out on the humic acids extracted from peat soils. Additional information was obtained by determination of water holding capacity, density, ash and pH for peats and optical parameter Q4/6for humic acids. Humic acid suspensions exhibited the highest buffer properties at low pH and reached maximum at pH ~ 4. Phosphates possessed buffer properties in the pH range from 4.5 to 8.0. The maximum of buffering was at pH~6.8 and increased proportionally with an increase in the concentration of phosphate ions. The study indicated that the presence of phosphate ions may strongly change natural buffer capacity of humic acids by shifting buffering maximum toward higher pH values. Significant correlations were found for the degree of the secondary transformation with both the buffer capacity and the titrant volume used during titration.

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Studies on copper(II)- and zinc(II)-mixed ligand complexes of humic acid

Cited by 58 publications

References 16 publications

Aspects of protonation and deprotonation of humic scid durface on molecular conformation

Aspects of protonation and deprotonation of humic scid durface on molecular conformation

Complexation Study of Humic Acids Extracted from Forest and Sahara Soils with Zinc (II) and Cadmium (II) by Differential Pulse Anodic Stripping Voltammetry (DPASV) and Conductimetric Methods

Influence of phosphate ions on buffer capacity of soil humic acids

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