Effects of Ca2+ on supramolecular aggregation of natural organic matter in aqueous solutions: A comparison of molecular modeling approaches

Kalinichev, Andrey G.; Iskrenova-Tchoukova, E.; Ahn, Won Young; Clark, Mark M.; Kirkpatrick, R. James

doi:10.1016/j.geoderma.2010.09.002

Cited by 76 publications

(87 citation statements)

References 41 publications

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“…These results evidence the high interactions occurring between Ca 2+ ions and ionized carboxyl groups on both citrate and River humic OM. 30,32,33 Page 14 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 15 Citrate-coated AgNPs aggregation in WW humic-containing solutions was clearly observed at 10 mM Na + with a k 11 of 0.28 nm.min -1 , (Figure 2b and S1d). Furthermore, the aggregation rate constant increased at 20 and 30 mM Na + , indicating reaction limited regime.…”

Section: Aggregation Kinetic Of Citrate-coated Agnps In Om-containingmentioning

confidence: 99%

“…20,30,32,33 Furthermore, CCC in Ca 2+ solutions would occur at a lower ionic strength than in Na + solutions. Nevertheless, due to sample volume constraints it was not possible to exactly determine the critical coagulation concentration to establish an accurate comparison between favorable and unfavorable aggregation in Na + or Ca 2+ solutions.…”

Section: Acs Paragon Plus Environment Langmuirmentioning

confidence: 99%

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Citrate-Coated Silver Nanoparticles Interactions with Effluent Organic Matter: Influence of Capping Agent and Solution Conditions

Gutierrez

Aubry²,

Cornejo

et al. 2015

Langmuir

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Just Accepted "Just Accepted" manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides "Just Accepted" as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. "Just Accepted" manuscripts appear in full in PDF format accompanied by an HTML abstract. "Just Accepted" manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). "Just Accepted" is an optional service offered to authors. Therefore, the "Just Accepted" Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the "Just Accepted" Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these "Just Accepted" manuscripts. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 Abstract: Fate and transport studies of silver nanoparticles (AgNPs) discharged from urban wastewaters containing effluent organic matter (EfOM) into natural waters represent a key knowledge gap. In this study, EfOM interfacial interactions with AgNPs and their aggregation kinetics were investigated by atomic force microscopy (AFM) and time-resolved dynamic light scattering (TR-DLS), respectively. Two well-characterized EfOM isolates, i.e., wastewater humic (WW humic) and wastewater colloids (WW colloids, a complex mixture of polysaccharides-proteins-lipids), and a River humic isolate of different characteristics were selected. Citrate-coated AgNPs were selected as representative capped-AgNPs. Citrate-coated AgNPs showed a considerable stability in Na + solutions. However, Ca 2+ ions induced aggregation by cation bridging between carboxyl groups on citrate. Although the presence of River humic increased the stability of citrate-coated AgNPs in Na + solutions due to electrosteric effects, they aggregated in WW humic-containing solutions, indicating the importance of humics characteristics during interactions. Ca 2+ ions increased citrate-coated AgNPs aggregation rates in both humic solutions, suggesting cation bridging between carboxyl groups on their structures as a dominant interacting mechanism. Aggregation of citrate-coated AgNPs in WW colloids solutions was significantly faster than those in both humic solutions. Control experiments in urea solution indicated hydr...

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Section: Aggregation Kinetic Of Citrate-coated Agnps In Om-containingmentioning

confidence: 99%

Section: Acs Paragon Plus Environment Langmuirmentioning

confidence: 99%

Citrate-Coated Silver Nanoparticles Interactions with Effluent Organic Matter: Influence of Capping Agent and Solution Conditions

Gutierrez

Aubry²,

Cornejo

et al. 2015

Langmuir

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“…We address this issue in more detail elsewhere. 65,94 Thus, the computed K a and K eq values should be considered only as semi-quantitative estimates. To help evaluate the results, it will be important to expand and resolve the discrepancies among the experimental K a values.…”

Section: Potentials Of Mean Force Association and Equilibrium Constamentioning

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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“…In aqueous solution, the residence time of calcium ion coordination to NOM carboxylic groups was found to be 0.5 ns, more than an order of magnitude longer than for sodium ion coordination [107,108]. Aggregation of NOM particles occurred in calcium solutions due to ion bridging, but not in sodium solutions where ion bridging did not occur [107,108]. Ion bridging between NOM particles was also found to predominate near polyethersulfone membrane surfaces, while no evidence of NOM surface complexes was seen [101].…”

Section: Simulations Of Natural Organic Matter (Nom) and Nom-mineral mentioning

confidence: 91%

“…Kalinichev et al have used MD simulation to test ion bridging models of NOM aggregation in aqueous solution [107,108] and at polyethersulfone membrane surfaces [101]. In aqueous solution, the residence time of calcium ion coordination to NOM carboxylic groups was found to be 0.5 ns, more than an order of magnitude longer than for sodium ion coordination [107,108].…”

Section: Simulations Of Natural Organic Matter (Nom) and Nom-mineral mentioning

confidence: 99%

Interaction of Natural Organic Matter with Layered Minerals: Recent Developments in Computational Methods at the Nanoscale

2014

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Abstract:The role of mineral surfaces in the adsorption, transport, formation, and degradation of natural organic matter (NOM) in the biosphere remains an active research area owing to the difficulties in identifying proper working models of both NOM and mineral phases present in the environment. The variety of aqueous chemistries encountered in the subsurface (e.g., oxic vs. anoxic, variable pH) further complicate this field of study. Recently, the advent of nanoscale probes such as X-ray adsorption spectroscopy and surface vibrational spectroscopy applied to study such complicated interfacial systems have enabled new insight into NOM-mineral interfaces. Additionally, due to increasing capabilities in computational chemistry, it is now possible to simulate molecular processes of NOM at multiple scales, from quantum methods for electron transfer to classical methods for folding and adsorption of macroparticles. In this review, we present recent developments in interfacial properties of NOM adsorbed on mineral surfaces from a computational point of view that is informed by recent experiments.

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Effects of Ca2+ on supramolecular aggregation of natural organic matter in aqueous solutions: A comparison of molecular modeling approaches

Abstract: fects of Ca2+ on supramolecular aggregation of natural organic matter in aqueous solutions: A comparison of molecular modeling approaches. Geoderma, Elsevier, 2011, 169, pp.27-32

Cited by 76 publications

References 41 publications

Citrate-Coated Silver Nanoparticles Interactions with Effluent Organic Matter: Influence of Capping Agent and Solution Conditions

Citrate-Coated Silver Nanoparticles Interactions with Effluent Organic Matter: Influence of Capping Agent and Solution Conditions

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

Interaction of Natural Organic Matter with Layered Minerals: Recent Developments in Computational Methods at the Nanoscale

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