presentation on adsorbtion

1. SAMER AZIZ
DE-068
PHYSICAL PHARMACY

2.  ADSORPTION: Adsorbtion is a process that occurs
when a gas or liquid solute accumulates on the surface
of solid and liquid.
 ADSORBENT: (also called substrate). The solid
particle that provide space for adsorption.
 ADSORBATE: The gas or a liquid substance that are
to be adsorben on the surface.

4.  The amount of heat evolved when one mole of the
adsorbate is adsorbed on the adsorbent surface is called
enthalpy of adsorption
 Adsorption is always an exothermic process and
enthalpy change of adsorption is always negative
 When adsorbate molecule are adsorbed on the surface
of an adsorbent their freedom of movement becomes
restricted and hence entropy decrease
 Adsorption is spontaneous therefore at constant
temperature and pressure Gibbs free energy decreases

6.  PHYSICAL ADSORPTION
It’s also called physiosorption “that type of adsorption
in which the adsorbent species are held tighter by
vender Waalsforces” . It has low enthalpy of
adsorption i.e. ΔH adsorption is 20-40KJ/mol
 CHEMICAL ADSORPTION
It’s also calls chemisorption “that type of adsorption in
which adsorbate and adsorbent held together by
chemical bonding with each other”

7.  SOLUTE CONCENTRATION: there is increase in the
amount of adsorption with increase in concentration of
solute
 SURFACE AREA: the amount of solute adsorbed
depend upon the surface area available. thus reduction
in particle size of adsorbent will result in an increase in
surface area and hence increase in adsorption
 TEMPERATURE :most of the adsorption processes
being exothermic an increase in temperature will
decrease in the amount of adsorption

8.  REMOVAL OF ADSORBED IMPURITIES: adsorbed
impurities (gas or moisture) on the surface of solid
adsorbent decrease its the efficiency. Generally heating
at high temperature (at 110 degree for 1 hr) remove
these impurities to activate the adsorbent and the
efficiency is increased
 PH OF THE MEDIUM: the adsorption would increase
or decrease with a change in PH

9.  There are 3 type They can be divided into
three main classes.
 • Low energy electron diffraction.(LEED)
 • Photo electron spectroscopy.(PES)
 • Scanning tunnelling microscopy.(STM)