Is my statement or understanding correct?
Physisorption includes physical adsorption mechanism in which surface area plays important role. However for chemisorption, the mechanism involve are electrostatic interaction or ion exchange. By which, surface charges / functional groups plays important role in chemisorption but not for physisorption.
Not quite. Although chemisorption is perhaps typically more reliant on the surface chemistry than physisorption this is not the real difference. Chemisorption involves a chemical reaction between the surface and the adsorbate, i.e. chemical bonds are generated at the surface. Physisorption differs from this as adsorption processes are defined by physical attraction (London forces) between the surface and the adsorbate.
An example pertinent to your proposed distinction:
Physisorption can be influenced by surface functional groups. For example, polar functional groups on porous carbon materials (e.g. heterogeneous activated carbon) can influence the adsorption of N2 in a typical so-called BET experiment. This is because N2 has a fairly large quadruople moment and will have a greater attraction for the polar moieties than the rest of the carbon surface. This is actually a bit of an issue in these experiments, as it means that the cross-sectional area of N2 differs dependent upon where it is adsorbed - this will result in errors in the calculated BET surface area. Nonetheless, at no point did N2 chemically bond with the carbon surface, so this is not chemisorption.
The type of interactions between the adsorbate molecules and the surface are important. The surface area does not matter here.
- Badges
- Science topic
- Similar topics
- Engineering
- Petroleum Engineering
- Gas