Natural organic matter at oxide/water interfaces: complexation and conformation

Au, Kwok-Keung; Penisson, Adrian C.; Yang, Shuolin; O’Melia, Charles R.

doi:10.1016/s0016-7037(99)00268-9

Cited by 109 publications

(90 citation statements)

References 30 publications

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“…The data show little salt dependency but the adsorption is strongly pH dependent. This type of sorption behavior is commonly found for FA and other fractions of NOM (Tipping, 1981;Becket and Le, 1990;Wang et al, 1997;Au et al, 1999). The lines in Fig.…”

Section: Basic Charging Behavior and Fa Adsorptionsupporting

confidence: 71%

Modeling the binding of fulvic acid by goethite: the speciation of adsorbed FA molecules

Filius

Meeussen²,

Lumsdon³

et al. 2003

Geochimica et Cosmochimica Acta

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Section: Basic Charging Behavior and Fa Adsorptionsupporting

confidence: 71%

Modeling the binding of fulvic acid by goethite: the speciation of adsorbed FA molecules

Filius

Meeussen²,

Lumsdon³

et al. 2003

Geochimica et Cosmochimica Acta

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“…4,5 NOM can also easily adsorb onto mineral surfaces, forming an organic coating which significantly alters the electrostatic properties of the surface and strongly affects the transport and availability of toxic species. [6][7][8][9][10][11] The formation of NOM coatings is also a significant factor controlling the stability of viruses in aquatic systems 12 and the performance characteristics of inorganic and polymeric nanofiltration membranes. 13,14 Common cations such as Na + , Mg 2+ , and Ca 2+ are thought to play an important role in the supramolecular aggregation of NOM molecules into colloidal particles, 2,3,[15][16][17][18][19][20] the formation of NOM surface coatings, [10][11][12][13] and the aggregation of mineral particles.…”

Section: Introductionmentioning

confidence: 99%

Metal Cation Complexation with Natural Organic Matter in Aqueous Solutions: Molecular Dynamics Simulations and Potentials of Mean Force

Iskrenova-Tchoukova¹,

Kalinichev²,

2010

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Natural organic matter (NOM, or humic substance) has a known tendency to form colloidal aggregates in aqueous environments, with the composition and concentration of cationic species in solution, pH, temperature, and the composition of the NOM itself playing important roles. Strong interaction of carboxylic groups of NOM with dissolved metal cations is thought to be the leading chemical interaction in NOM supramolecular aggregation.Computational molecular dynamics (MD) study of the interactions of Na + , Mg 2+ , and Ca 2+ with the carboxylic groups of a model NOM fragment and acetate anions in aqueous solutions provides new quantitative insight into the structure, energetics, and dynamics of the interactions of carboxylic groups with metal cations, their association and the effects of cations on the colloidal aggregation of NOM molecules. Potentials of mean force and the equilibrium constants describing overall ion association and the distribution of metal cations between contact ion pairs and solvent separated ions pairs were computed from free MD simulations and restrained umbrella sampling calculations. The results provide insight into the local structural environments of metal-carboxylate association and the dynamics of exchange among these sites. All three cations prefer contact ion pair to solvent separated ion pair coordination, and Na + and Ca 2+ show a strong preference for bidentate contact ion pair formation. The average residence time of a Ca 2+ ion in a contact ion pair with the carboxylic groups is of the order of 0.5 ns, whereas the corresponding residence time of a Na + ion is only between 0.02 and 0.05 ns. The average residence times of a Ca 2+ ion in a bidentate coordinated contact ion pair vs. a monodentate coordinated contact ion pair are about 0.5 ns and about 0.08 ns, respectively. On the 10-ns time scale of our simulations, aggregation of the NOM molecules occurs in the presence of Ca 2+ but not Na + or Mg 2+ . These results agree with previous experimental observations and are explained 3 by both Ca 2+ ion-bridging between NOM molecules and decreased repulsion between the NOM molecules due to the reduced net charge of the NOM-metal complexes. Simulations on a larger scale are needed to further explore the relative importance of the different aggregation mechanisms and the stability of NOM aggregates.4

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“…Stumm (1992) and Zachara et al (1994) reported that humic substances with high molecular mass are more readily adsorbed at the existing mineral surface in freshwaters than less aromatic and low-weight organic matter. Au et al (1999) verified that the charge of a hematite surface was deeply affected by the adsorption of humic acid (HA). The hematite-HA surface had an overall negative charge at all pH values examined indicating that the adsorption of the humic acid on the hematite caused an exchange on the surface charge of the mineral at pH below 8.1 (pH zpc for hematite), and enhanced the negative charge on the surface at higher pH values.…”

Section: Discussionmentioning

confidence: 96%

Changes in Copper Speciation and Geochemical Fate in Freshwaters Following Sewage Discharges

Sodré

Grassi

2006

Water Air Soil Pollut

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The main factors determining the geochemical fate of copper in urban freshwaters affected by raw sewage discharges were investigated in this work. Water samples from the Iraí and Iguaçu rivers were collected monthly during a 1-year period at two points located upstream and downstream from the city of Curitiba, in Brazil. Results revealed that raw sewage discharges from the heavily urbanized area caused an enhancement of humic-coated suspended solids in the Iguaçu River. In these waters copper is predominantly associated with the humic-coated particles whereas in the Iraí River copper was found primarily in the aqueous phase. The transfer of copper from the aqueous to the solid phase changed its physical speciation along the watercourse. Thus, aspects related to the overall transport of trace metals in watercourses become an important issue to be considered in further studies concerning the effect of sewage discharges on the geochemical speciation and fate of trace metals in urban rivers.

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Natural organic matter at oxide/water interfaces: complexation and conformation

Cited by 109 publications

References 30 publications

Modeling the binding of fulvic acid by goethite: the speciation of adsorbed FA molecules

Modeling the binding of fulvic acid by goethite: the speciation of adsorbed FA molecules

Metal Cation Complexation with Natural Organic Matter in Aqueous Solutions: Molecular Dynamics Simulations and Potentials of Mean Force

Changes in Copper Speciation and Geochemical Fate in Freshwaters Following Sewage Discharges

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