
104 Green Chemical Engineering
the nal equilibrium stage for which the intra-particle diffusion starts to slow down due
to the extremely low residual adsorbate concentration in the solution (Suresh et al., 2011e).
The deviation of straight lines from the origin indicates that the pore diffusion is not the
sole rate-controlling step. Therefore, the adsorption proceeds via a complex mechanism
consisting of both surface adsorption and intra-particle transport within the pores of syn-
thesised and commercial zeolite.
It can be inferred from Figure A.6 that the diffusion of methyl orange, methyl blue and
safranine T from the bulk phase to the exter ...