Effect of pressure on adsorption :
At constant temperature, the extent of adsorption of a gas (x/m)
in a solid increases with pressure. A graph between x/m
and the pressure P
of a gas at constant temperature is called adsorption isotherm.
Freundlich adsorption isotherm
a.
At lower range of pressure (x/m)
is directly proportional to the applied presure.
x
m
∝P1
ltbr. b
. At high pressure range, the extent of adsorption of a gas (x/m)
is independent of the applied pressure.
x
m
∝P∘
c.
At intermediate pressure range the value of x/m
is proportional to a fractional power of pressure, i.e.,
x
m
∝P1/n
log(
x
m
)=logK+
1
n
logP
Effect of temperature on adsorption :
Adsoption is generally temerature dependent.Mostly adsorption processes are exothermic and hence adsorption decreases with increasing temperature. However, for an endothermic adsorption process, adsorption increases with increase in temperature.
