Transcript Novel Cofactor - McMaster University

Chen Lu
McMaster Centre for Pulp and Paper Research
Department of Chemical Engineering, McMaster University
Hamilton, CA
[email protected]
http://papersci. 905 525 9140
mcmaster.ca
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Content
 Why
polymer adsorption
 General features of polymer
adsorption
 Neutral polymer adsorption
 Polyelectrolyte adsorption
 Conclusion
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Why Polymer Adsorption


A topic of fundamental importance
– Stabilization of colloidal dispersions
– Controlled flocculation
– Adhesion
– Lubrication
Example: the first step of bridging flocculation (waste water
treatment)
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General Features

Driving Force
– Hydrophobic force
– Electrostatic force
– Special bonding (hydrogen bonding)
– Large entropy change
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General Features

Polymer morphology
Loo
p
Tail
Polymer spreads out and
lies flat
Train
There is no polymer desorption once
adsorbed
Polymer forms mono-layer on the surface
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Neutral Polymer Adsorption

Poly(ethylene oxide) (PEO) adsorbs at
negatively charged polystyrene surface
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
Hydrophobic
attraction

Adsorption amount
decreases with
increasing surface
charge density
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Neutral Polymer Adsorption


OH
C
O

C
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PEO adsorbs at poly(pvinyl phenol) (PVPh)
surface
Hydrogen bonding
(stronger than
hydrophobic force)
quenches PEO spreading
on PVPh surface
Larger PEO adsorption
capacity for PVPh surface
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Polyelectrolyte Adsorption

Poly(styrene sulphonate) (PSS) adsorps onto
uncharged surface



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Driving force is mainly
hydrophobic force.
Electrostatic force
prevents polymers from
accumulating on the
surface
Increasing salt
concentration can increase
adsorption amount due to
charge screening.
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Polyelectrolyte Adsorption

Cationic polyacrylamide adsorbs at negatively
charged silica surface
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
Driving force is mainly
electrostatic force.

Adsorption amount will
decrease with increasing
salt concentration due to
charge screening.
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Polyelectrolyte Adsorption




Cationic polyacrylamide adsorbs at negatively
charged montmorillonite clay.
Driving forces are both electrostatic force and
hydrophobic force.
For high polymer charge density, salt promotes
adsorption.
For low polymer charge density, salt opposes adsorption.
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Polyelectrolyte Adsorption

Anionic poly(methacrylic acid) adsorbs onto
negatively charged AgI surface.



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No adsorption at low salt
concentration
Increasing salt
concentration can
promote adsorption.
Driving force is
hydrophobic force when
charge is screened by
salt.
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Conclusion
 Polymer
adsorption is widely
applied in industry.
 Different polymer can adsorb
onto different kind of surface
due to different driving force.
 The mechanism of adsorption is
a complicated topic.
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http://www.papersci.mcmaster.ca
That’s It!
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