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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 chitin suspension as a function of pH at three discrete salinity values. At zero salinity, z-potential is a function of pH, with the point of zero charge at approximately pHpzc = 5.5. However, when a small amount of electrolyte is present in the system, ζ-potential immediately becomes insensitive to pH, with its value very close to zero.
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Figure 8: The ζ-potential of chitin suspension as a function of pH at three discrete salinity values. At zero salinity, z-potential is a function of pH, with the point of zero charge at approximately pHpzc = 5.5. However, when a small amount of electrolyte is present in the system, ζ-potential immediately becomes insensitive to pH, with its value very close to zero.

Mentions: The ζ-potential of chitin as a function of pH at low salinity values (S ≈ 1.1 – 2.1) characterizes suspended chitin as particles with little electrostatic charges (Figure 8). This characterization comes from the near-zero ζ-potential values that are virtually independent of pH in aqueous solutions. The data in Figure 8 also reveal the pH-dependent surface charge in the zero salinity chitin suspension. This charge is derived from the protonation of the amino group at low pH and deprotonation of the hydroxyl group at high pH.


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 chitin suspension as a function of pH at three discrete salinity values. At zero salinity, z-potential is a function of pH, with the point of zero charge at approximately pHpzc = 5.5. However, when a small amount of electrolyte is present in the system, ζ-potential immediately becomes insensitive to pH, with its value very close to zero.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: The ζ-potential of chitin suspension as a function of pH at three discrete salinity values. At zero salinity, z-potential is a function of pH, with the point of zero charge at approximately pHpzc = 5.5. However, when a small amount of electrolyte is present in the system, ζ-potential immediately becomes insensitive to pH, with its value very close to zero.
Mentions: The ζ-potential of chitin as a function of pH at low salinity values (S ≈ 1.1 – 2.1) characterizes suspended chitin as particles with little electrostatic charges (Figure 8). This characterization comes from the near-zero ζ-potential values that are virtually independent of pH in aqueous solutions. The data in Figure 8 also reveal the pH-dependent surface charge in the zero salinity chitin suspension. This charge is derived from the protonation of the amino group at low pH and deprotonation of the hydroxyl group at high pH.

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