Kinetics and Mechanisms Study of Congo red, Eosin B and Neutral red Adsorption from Aqueous Solutions on Kaolin

Abstract

In this study, kaolin clay was used as the adsorbent for the removal of congo red,
eosin B and neutral red from aqueous solutions. The effect of contact time was
investigated and found that the adsorption process of dyes on kaolin surface was reached
complete equilibrium within 60 min
The maximum uptake of congo red, eosin B and neutral red by kaolin clay were
found to be 65.7%, 89.7% and 97.9%, respectively.
The kinetic data were well fitted to the lagergren, pseudo-second order models.
The results obtained show that the second order rate constants of eosin – kaolin and
neutral red – kaolin systems are much higher than that of congo red – kaolin system. This
behavior was discussed depending on the chemical structure of dyes and kaolin surface.
The kinetics of dyes adsorption was also studied in terms of intraparticle
diffusion model. The results indicated that intraparticle diffusion plays a significant role
in the adsorption mechanism.