Surface Chemistry

1
Surface Chemistry

• Many phenomena of interest occur at the interface
  of liquids, gases, and solids. These include
• catalysis
• chromatography
• pharmaceutical formulations
• host response to biomaterial implantation

2
The Interphase Region

• Consider 2 homogeneous phases in contact with
  each other.

?
?
3
Surface Tension

• Consider a liquid in equilibrium with its
  vapor

?LV interfacial tension (N/m)
4
Surface Free Energy

• What happens to a soap film being stretched on a
  frame?

L
F
dx
5
Capillary Rise
2r
h
water
6
Example

• Pure ethanol rises 2.48 cm in a capillary at
  30C. The diameter of the capillary is 0.046 cm
  and the density of ethanol at this temperature is
  0.781 g/cm3. What is the surface tension of
  ethanol?

7
Adsorption on Solid Interfaces
physisorption
chemisorption
8
Adsorption Isotherms

• Langmuir isotherm
• Based on the following
• assumptions
• solid has a uniform surface
• adsorbed molecules do not
• interact with each other
• 3) there are specific sites for
• adsorption
• only a monolayer of molecules
• is adsorbed