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Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater.

Furukawa Y, Watkins JL, Kim J, Curry KJ, Bennett RH - Geochem. Trans. (2009)

Bottom Line: When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited.These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems.It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans.

View Article: PubMed Central - HTML - PubMed

Affiliation: Naval Research Laboratory, Seafloor Sciences Branch, Stennis Space Center, Mississippi, USA. yoko.furukawa@nrlssc.navy.mil

ABSTRACT

Background: The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 - 7.2 psu).

Results: The montmorillonite-only system increased the degree of aggregation with salinity increase, as would be expected for suspended colloids whose dispersion-aggregation behavior is largely controlled by the surface electrostatic properties and van der Waals forces. When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited. The surface interaction energy model calculations reveal that the steric repulsion, rather than the increase in electronegativity, is the primary cause for the inhibition of aggregation by the addition of humic acid or chitin.

Conclusion: These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems. It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans.

No MeSH data available.


Related in: MedlinePlus

The ζ-potential of humic acid (HA), chitin and montmorillonite suspensions at circumneutral pH (7 < pH < 7.5) as a function of salinity. Note that the value for montmorillonite are averages over different surfaces including permanently negative face surfaces and less negative (and neutral or even positive in low pH) edge surfaces.
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Figure 10: The ζ-potential of humic acid (HA), chitin and montmorillonite suspensions at circumneutral pH (7 < pH < 7.5) as a function of salinity. Note that the value for montmorillonite are averages over different surfaces including permanently negative face surfaces and less negative (and neutral or even positive in low pH) edge surfaces.

Mentions: The ζ-potential values of pure montmorillonite, HA, and chitin suspensions as a function of salinity (Figure 10) reveal that the ζ-potential is a very strong function of salinity in very low salinity suspensions (S ≈ 0 – 2 psu) with less salinity dependency at higher salinity (S > 2 psu).


Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater.

Furukawa Y, Watkins JL, Kim J, Curry KJ, Bennett RH - Geochem. Trans. (2009)

The ζ-potential of humic acid (HA), chitin and montmorillonite suspensions at circumneutral pH (7 < pH < 7.5) as a function of salinity. Note that the value for montmorillonite are averages over different surfaces including permanently negative face surfaces and less negative (and neutral or even positive in low pH) edge surfaces.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2654465&req=5

Figure 10: The ζ-potential of humic acid (HA), chitin and montmorillonite suspensions at circumneutral pH (7 < pH < 7.5) as a function of salinity. Note that the value for montmorillonite are averages over different surfaces including permanently negative face surfaces and less negative (and neutral or even positive in low pH) edge surfaces.
Mentions: The ζ-potential values of pure montmorillonite, HA, and chitin suspensions as a function of salinity (Figure 10) reveal that the ζ-potential is a very strong function of salinity in very low salinity suspensions (S ≈ 0 – 2 psu) with less salinity dependency at higher salinity (S > 2 psu).

Bottom Line: When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited.These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems.It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans.

View Article: PubMed Central - HTML - PubMed

Affiliation: Naval Research Laboratory, Seafloor Sciences Branch, Stennis Space Center, Mississippi, USA. yoko.furukawa@nrlssc.navy.mil

ABSTRACT

Background: The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 - 7.2 psu).

Results: The montmorillonite-only system increased the degree of aggregation with salinity increase, as would be expected for suspended colloids whose dispersion-aggregation behavior is largely controlled by the surface electrostatic properties and van der Waals forces. When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited. The surface interaction energy model calculations reveal that the steric repulsion, rather than the increase in electronegativity, is the primary cause for the inhibition of aggregation by the addition of humic acid or chitin.

Conclusion: These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems. It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans.

No MeSH data available.


Related in: MedlinePlus