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Molecular adsorption & molecular encapsulation
Transcript of Molecular adsorption & molecular encapsulation
: is a physical or chemical process whereby atoms, ions or molecules are trapped or retained on the
of a material.
: is a physical or chemical process whereby atoms, ions or molecules pass from a first phase to another, by joining at the
of the second phase.
attraction between the molecules present on the surface of an adsorbent solid and a fluid mixture.
solid on which the transferable component of the liquid phase is retained
is the component transferred from the fluid phase to the surface of the adsorbent
- Big especific surface
(wich means high porosity)
- Good capacity of regeneration (desorption)
generic term that describes a family of highly crystalline carbonaceous adsorbents and with a highly developed internal porosity.
Adsorption types according to the interaction
electrostatic attraction on charged sites of the surface
- by Van der Waals forces
- the adsorbed specie retains its chemical nature
- is not fixed at a specific location of the surface
- by covalent bonds
- the adsorbed specie suffers a transformation to form a distinct specie
- the adsorbate forms strong bonds in the active centers of the adsorbent
Physisorption - multilayers
Chemisorption - monolayer
- adsorption distance: where the energy of the system with respect to the molecule to be adsorbed is minimal
d(physisorption) < d(chemisorption)
- temperatures occurrence:
T(physisorption) < T(chemisorption)
because chemisorption needs an activation energy
Molecular potential energy evolution approaching at a surface.
- adsorption is favored:
- adsorption is an exotermic process:
G= H-T S
Pore types and methods of characterization of porous solids
- closed / opened
- cylindrical, slit, hollow, funnel, ink-bottle shaped...
- radiation scattering
- fluid flow
- calorimetric methods
adsorbent - nanopores (activate centers)
admit that molecules of different nature are installed
e.g.: equilibums of adsorbent solids and gas mixture
- Adsorption isotherms - amount of gas adsorbed at the monopores on depending external gas pressure
the types depend on the porosity of the material, the adsorbate-adsorbent interaction...
Adsorption is used to remove individually the
components of a gaseous or liquid mixture
The removed component can be the desired product but also an impurity
e.g.: cleaning of waste gases
- to remove humidity from compressed air
- to remove odors, flavors or colors unwanted (oils, sugar syrups...)
- gasoline dehumidification
- to obtain nitrogen
new nanopores materials with better gas adsorption properties...
DEFINITION: guest molecule captured in the cavity of a host molecule
One of the first examples of encapsulation was made by Cram and his coworkers
- carcerand molecule
-glass, polymer, ceramic
EXAMPLES OF CAPSULES USED FOR ENCAPSULATION
APPLICATION: DRUG DELIVERY
Advantages of encapsulation in drug delivery:
-Smaller effective doses of ingested drugs
-Reduced number of secondary effects
Examples of special drug delivery mechanisms:
Targeted drug delivery
: Increases the concentration of the medication in some parts of the body relative to other
Thin-film drug delivery
: Hydrophilic polymer film that rapidly dissolves on the tongue
Small particles surrounded by coating to create microcapsules, used to incorporate food ingredients, enzymes, etc. on a
-Microcapsules that break easily when rubbed and release an aroma
-Perfume samples, scented stickers
-Detect anosmia (inability to perceive odor)
-Educate on methane gas leak
-diameters from 1µm to 1mm
APPLICATIONS OF ENCAPSULATION
-Perfume samples in magazines
-Fabrics with new functionality
-Hydrophobic and self-cleaning fabrics
-Coloration of fabrics
-Improve performance of aromas, vitamins, etc.
-Hide bad taste in food products
-Skin care products