Evaluation of the adsorption kinetics of brilliant green dye onto a montmorillonite/alginate composite beads by the shrinking core model.

Montmorillonite/alginate composite beads have been studied for adsorption of brilliant green dye in batch experiments. The geometry and features of this clay/polymer composite, in combination with the strong color of the dye, were very useful to apply and test in a simple way the shrinking core model (SCM). This model is very popular for describing adsorption in porous systems, but not in clay/polymer composite beads. The SCM describes the adsorption as a diffusion process of the adsorbate through a spherical shell. The great advantage of using the clay and the dye is that they allow observing with the naked eye or through digital photographs the progress of the front of adsorption (penetration radius) as the reaction takes place. This was never informed in the literature. The experimental changes in penetration radius and dye concentration with time were compared with SCM predictions at different initial concentrations of brilliant green. There was an excellent agreement between theory and experiments, and thus the kinetics of the process could be thoroughly evaluated. The estimated values of the parameters liquid phase mass transfer coefficient and effective diffusion coefficient in the adsorbent are k_f > 0.00008 m s⁻¹ and D_p = 5 × 10⁻¹⁰ m² s⁻¹ respectively. [ABSTRACT FROM AUTHOR]