Another empirical isotherm given by the Freundlich equation
is often used to describe adsorption data. The linear
form of the Freundlich isotherm can be represented in the
following form:
ln qeZln QfC
1
n
ln Ce ð8Þ
where Qf is roughly an indicator of the adsorption capacity and
1/n is the adsorption intensity. Therefore, Qf and 1/n can be
determined from the linear plot of ln qe versus ln Ce. The
magnitude of the exponent 1/n gives an indication of the
favourability of adsorption. Values of nO1 represent favourable
adsorption conditions [18].
In our work, linear forms of the Langmuir and Freundlich
isotherms were used to fit the equilibrium data of lac dye adsorption
on cotton in the presence of 0.5 M sodium chloride
and on cotton pretreated with chitosan compared to untreated
cotton.