RL=
1
1 + kLC0
(16)
where KL (L mg−1
) is the Langmuir constant and C0 (mg L
−1
) is
the initial concentration of MB in solution. The value of RL indi-cates if the adsorption process is irreversible (RL= 0), favorable
(0 < RL< 1), linear (RL= 1) or unfavorable (RL> 1). RL values related
to MB adsorption on keratin nanofibre membranes were less than
1 and greater than 0 for all initial MB concentration considered
(Fig. 7) indicating a favorable adsorption.
Moreover, the mean free energy evaluated using the D–R model
is of about 16 kJ mol−1
, indicating that the adsorption of MB on
keratin nanofibre membranes was a chemisorptions process which
occurred by ion exchange reactions