Conductometric analysis of polyelectrolytes in solution

Leeuwen, Herman P. van; Cleven, R.F.M.J.; Valenta, P.

doi:10.1351/pac199163091251

Cited by 37 publications

(18 citation statements)

References 30 publications

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“…The complexation of humic acids with metal ions is confirmed when the positive value of this function is obtained (Van Leeuwen et al 1991). The association degree of metal ions and the humic acids is related to the slope values of the conductivity excess (Δk) versus metal ion concentrations.…”

Section: Conductimetry Investigationmentioning

confidence: 77%

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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Section: Conductimetry Investigationmentioning

confidence: 77%

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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“…A positive value of this function is usually obtained. It indicates the complexation of humic substances with metallic ions [15]. Here, the slope value of the ∆k versus metal ion concentration indicates the association degree of the metal ions with humic acids.…”

Section: Resultsmentioning

confidence: 99%

Conductimetric behaviour of humic acids with Cu(II) ions

Kaemmerer¹,

Guiresse²,

Revel³

et al. 1999

Analusis

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Humic substances play an important role in the behaviour of heavy metals in natural environments, due to the formation of complexes which can modify the mobility of these ions [1][2][3]. The complexation process depends on the nature of the heavy metal and on the humic substance (humic or fulvic acid). Thermodynamic, kinetic and structural studies using of different experimental techniques are needed to gain relevant information on global processes [4].Because relevant conclusions are reached using experimental conditions which are similar to those of natural ecosystems, in particular without the addition of species which could disturb the free equilibria, conductimetric techniques have been used to study the behaviour of humic substances both in absence and presence of complexating heavy metals [5][6][7][8][9]. On the other hand, theoretical work has been done to build mathematical equations which could be used to explain the experimental results [10]. Nevertheless, as far as we know, there are no studies of the influence of humic substances on the conductimetric behaviour of heavy metal/humic substance solutions. Here, we report the conductivity analysis of mixtures of a coal humic acid and Cu(II) ions. ExperimentalAll reagents were purchased at analytical grade and were used without further purification. We used deionised water with resistivity ≥ 14 MΩ cm.The sample of humic acid was extracted from a lignite coal from Candiota mines (Rio Grande do Sul, Brazil) using Tyurin´s procedure as described by Kononova [11]. 150 mL of NaOH 0.1 M were added to 10 g of coal sample, shaked in a closed flask during 24 hours and centrifuged (3000 rpm) during 30 min. The solid phase was discarded. The supernatant was acidified with H 2 SO 4 (pH ~ 2) then centrifuged 30 min at 8000 rpm. The precipitate (humic acids) was separated from fulvic acids by filtration, dissolved in 0.1 M NaOH then dialysed against water (pore diameter 20 Å). The final humic acid solution was then freeze-dried to obtain a brown powder.Cu(II) and NaOH stock solutions were prepared by dissolving solid CuSO 4. 5H 2 O and NaOH respectively in free-CO 2 water. Humic acid solutions were obtained by dissolving the appropriate amount of solid in water then stored under N 2 atmosphere.A Metrohm 660 conductometer, equipped with a platinum cell (nominal constant 0.7) and calibrated with 0.1000 M KCl solution, was used to measure the conductivity of Cu(II)/humic acid solutions. pH was measured with a Metrohm 6.0216.100 electrode fitted to a Methrom 654 pHmeter and calibrated by strong acid/strong base titration [12].All experiments were performed with a Methrom doublewalled glass cell at constant temperature (298.0 ± 0.2K) with water from a Landa refrigerated circulator bath. For each titration, 50 mL of a mixture of humic acid (20, 40, 60, and 80 mg L -1 ) and Cu(II) solution (0 to 1.9 10 -4 M) were equilibrated during 12 hours, transferred in to the cell then, after thermal equilibrium was reached, titrated with 0.011 M NaOH solution (Methrom 665 Dosimat...

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“…For the chosen ionic strengths of 10 and 100 mol m À3 , the HA charge density gives rise to Donnan potentials c D of ca. 48 In line with that, the two-state CC-Donnan model for electrostatic ion binding was applied to ion-selective electrode measurements of Ca 2+ binding by a forest soil HA at pH 6 in 1-1 electrolyte at I = 10 and 100 mol m À3 (r p ca. The ensuing Boltzmann factors for equilibrium partitioning of the free metal ion between the bulk medium and the intraparticulate zones were computed using eqn (8).…”

Section: Electrostatic Contribution To the Bindingmentioning

confidence: 99%

Intraparticulate speciation analysis of soft nanoparticulate metal complexes. The impact of electric condensation on the binding of Cd²⁺/Pb²⁺/Cu²⁺by humic acids

Town

Leeuwen

2016

Phys. Chem. Chem. Phys.

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In aqueous dispersions of soft, charged nanoparticles, the physicochemical conditions prevailing within the particle body generally differ substantially from those in the bulk medium. Accordingly it is necessary to define intrinsic descriptors that appropriately reflect the chemical speciation inside the particle's microenvironment. Herein the speciation of divalent metal ions within the body of negatively charged soft nanoparticulate complexants is elaborated for the example case of humic acid association with Cd(ii), Pb(ii) and Cu(ii). The electrostatic effects are described by a two-state model that accounts for counterion condensation in the intraparticulate double layer shell at the particle/medium interface and Donnan partitioning within the bulk of the particle body. Inner-sphere complex formation is defined by an intrinsic binding constant expressed in terms of local reactant concentrations as controlled by the pertinent electrostatic conditions. For the high particle charge density case (Debye length smaller than charged site separation), three distinct intraparticulate metal species are identified, namely free hydrated ions, electrostatically condensed ions, and inner-sphere metal-humic complexes. For all metal ions studied, the electrostatic contribution to the association of the metal ion with the oppositely charged particle is found to account for a substantial fraction of the total metal bound.

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Conductometric analysis of polyelectrolytes in solution

Abstract: Abstract

Cited by 37 publications

References 30 publications

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

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

Conductimetric behaviour of humic acids with Cu(II) ions

Intraparticulate speciation analysis of soft nanoparticulate metal complexes. The impact of electric condensation on the binding of Cd²⁺/Pb²⁺/Cu²⁺by humic acids

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Conductometric analysis of polyelectrolytes in solution

Abstract: Abstract

Cited by 37 publications

References 30 publications

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

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

Conductimetric behaviour of humic acids with Cu(II) ions

Intraparticulate speciation analysis of soft nanoparticulate metal complexes. The impact of electric condensation on the binding of Cd2+/Pb2+/Cu2+by humic acids

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Intraparticulate speciation analysis of soft nanoparticulate metal complexes. The impact of electric condensation on the binding of Cd²⁺/Pb²⁺/Cu²⁺by humic acids