Binding of calcium by humic acid

Choppin, Gregory R.; Shanbhag, P.M.

doi:10.1016/0022-1902(81)80150-9

Cited by 31 publications

(6 citation statements)

References 6 publications

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“…Table 6 presents the Ca 2+ -humic stability constants from the literature, with the log β values at 0.10 m (NaCl) from this work. The latter are in good agreement with the log β values from references [29][30][31]. Higgo et al [32] reported a value at I = 0.01 M (NaCl) of 2.15 ± 0.02; however, their stability constant is expressed in l/g.…”

Section: Resultssupporting

confidence: 86%

Interaction study between Ca²⁺ and humic acids in brine media

Laszak¹,

Choppin²

2001

Radiochimica Acta

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Section: Resultssupporting

confidence: 86%

Interaction study between Ca²⁺ and humic acids in brine media

Laszak¹,

Choppin²

2001

Radiochimica Acta

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“…Considering the hydrophobic character of aliphatic carbons [29], the enrichment of aliphatic carbons in the aggregates is reasonable because hydrophobic colloids can aggregate more readily than hydrophilic colloids, as a result of both hydrophobic interactions and hydrophilic repulsion effects [29]. We inferred that larger molecular size fractions of HA are enriched in aliphatic moieties [15,31,32] In the moderate pH condition, the 1:1 binding constant (K) of HA with metal ion is increased in the order of Ca 2+ (log K ≃ 3.0 for Aldrich HA [33]) < Ag + (log K ≃ 4.0 for lignite HA [34]) < Eu 3+ (log K ≃ 6.0 for Aldrich HA [16]). The affinity of Na(I)…”

Section: Msd-dependent Aggregationmentioning

confidence: 99%

Molecular-size-distribution-dependent aggregation of humic substances by Na(I), Ag(I), Ca(II), and Eu(III)

Tamamura

Ohashi

Nagao

et al. 2013

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Highlights >Molecular-size-distribution (MSD)-dependent aggregation of humics was investigated.>Larger molecular size fractions selectively coagulated by Na and Ca.>The MSD dependence was attributed to non-specific binding of Na and Ca to humics. >Large and small molecular size fractions concurrently coagulated by Ag and Eu.>The reduced MSD dependence was caused by specific binding of Ag and Eu to humics. 3 Graphical Abstract 4 ABSTRACT Molecular-size-distribution (MSD)-dependent aggregation of Fluka and InternationalHumic Substance Society humic acids (HAs) in the presence of Na(I), Ca(II), Ag(I), and Eu(III) were studied using high-performance size-exclusion chromatography. Larger molecular size fractions (>8000 Da) rich in aliphatic carbons were observed to aggregate in the presence of Na(I) and Ca(II), whereas both large and small molecular size fractions concurrently aggregated in the presence of Ag(I) and Eu(III). In view of the non-specific binding of Na(I) and Ca(II) with HAs, the electric-field screening effect is probably the main cause of HA aggregation by Na(I) and Ca (

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“…This approach provided us with the best chance to achieve our goal of improving conceptual models of NOM effects on U(VI) sorption kinetics. However, more complex and natural systems should be investigated in the future, with a particular focus on the role of competing ions, such as calcium, magnesium and sulfate, which may limit the impacts of NOM on radionuclide mobility. − …”

Section: Introductionmentioning

confidence: 99%

Effects of Fulvic Acid on Uranium(VI) Sorption Kinetics

Tinnacher

Nico

Davis

et al. 2013

Environ. Sci. Technol.

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This study focuses on the effects of fulvic acid (FA) on uranium(VI) sorption kinetics to a silica sand. Using a tritium-labeled FA in batch experiments made it possible to investigate sorption rates over a wide range of environmentally relevant FA concentrations (0.37-23 mg L(-1) TOC). Equilibrium speciation calculations were coupled with an evaluation of U(VI) and FA sorption rates based on characteristic times. This allowed us to suggest plausible sorption mechanisms as a function of solution conditions (e.g., pH, U(VI)/FA/surface site ratios). Our results indicate that U(VI) sorption onto silica sand can be either slower or faster in the presence of FA compared to a ligand-free system. This suggests a shift in the underlying mechanisms of FA effects on U(VI) sorption, from competitive sorption to influences of U(VI)-FA complexes, in the same system. Changes in metal sorption rates depend on the relative concentrations of metals, organic ligands, and mineral surface sites. Hence, these results elucidate the sometimes conflicting information in the literature about the influence of organic matter on metal sorption rates. Furthermore, they provide guidance for the selection of appropriate sorption equilibration times for experiments that are designed to determine metal distribution coefficients (Kd values) under equilibrium conditions.

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Binding of calcium by humic acid

Cited by 31 publications

References 6 publications

Interaction study between Ca²⁺ and humic acids in brine media

Interaction study between Ca²⁺ and humic acids in brine media

Molecular-size-distribution-dependent aggregation of humic substances by Na(I), Ag(I), Ca(II), and Eu(III)

Effects of Fulvic Acid on Uranium(VI) Sorption Kinetics

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Binding of calcium by humic acid

Cited by 31 publications

References 6 publications

Interaction study between Ca2+ and humic acids in brine media

Interaction study between Ca2+ and humic acids in brine media

Molecular-size-distribution-dependent aggregation of humic substances by Na(I), Ag(I), Ca(II), and Eu(III)

Effects of Fulvic Acid on Uranium(VI) Sorption Kinetics

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Interaction study between Ca²⁺ and humic acids in brine media

Interaction study between Ca²⁺ and humic acids in brine media