interfacial tension

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what happens to surface tension of the system with positive adsorption?

reduces
relationship between conc at interface and conc at bulk with positive adsorption

conc interface > con at bulk
what does wetting agent do to the contact angel when dissolved

dec contact angle
which ions are in the tightly bound layer of an electrical double layer

the potential determining ions
which ions are at the diffuse layer

an excess of the counter ions to the ones in the tightly bound layer
what ions are in the electrically neutral layer

there is a balance of determining and counter ions
nerst potential

electrothermodynamic potential: diff in potential btwn solid surface and electroneutral region
zeta potential

electrokinetic potential: diff in potential between shear plane (tightly bound plane) and electroneutral region
what does the zeta potential determine

the degree of repulsion between particles of like charge
if zeta potential falls below a certain value what happens?

particle aggregation - flocculation
2 ways to reduce the surface free energy and make a more thermodynamically stable state
- reduce interfacial tension with a surfactant
- dec the interfacial surface area through flocculation
we don't want flocculation, so use a surfactant
deflocculated particles

they don't aggregate, rather they just settle to the bottom (bigger ones first and then smaller ones) and the smaller ones begin to fill in all the crevices that the bigger ones leave and that forms a hard cake
3 assumptions of sedimentation theory
- use stokes law
- dilute suspension
- distinct boundary between the sediment and surfactant
what is the sedimentation volume

ratio of final volume of sediment to original volume
when will F be greater than 1?

when the network of flocs occupy a greater volume than the original volume

Author

jcu1

215761

Card Set

interfacial tension

Description

DD3 final

Updated

2013-04-25T13:34:28Z

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