Direct Red 28 Adsorption on Amosil and Avena sativa L.: Mass Transfer and Kinetics Modelling on the Solid/Solution Interface

Abstract

Adsorption kinetics is a key issue for successful sorbent selection and the proper design of batch and fixed-bed adsorption systems. The aim of the present study was to determine the kinetics, mass transfer and diffusion coefficients and to establish the rate-controlling mechanism/s during Direct Red 28 adsorption on Amosil and Avena sativa L. biomass. Five kinetic models (pseudo-second order, Blanchard, Avrami, Ritchie and power function) and and four mass transfer (external diffusion, film diffusion, particle diffusion, intraparticle diffusion) mathematical models were applied to the experimental data. To confirm the best-fitting model(s), error analyses were conducted. The integrative comparative analyses of the values of the predicted model parameters, coefficients and error functions established that the intraparticle diffusion model best represented the experimental results of the dye sorption on dried A. sativa L. biomass, while for the Direct Red 28/Amosil system, the kinetic behavior is the best described by either the pseudo-second or Blanchard’s model. Boyd’s effective intraparticle diffusion coefficient (D i ), characterizing the dye sorption on Amosil, is significantly lower than that for the system Direct Red 28/A. sativa L. biomass. The low values of the Bi number (Bi < 0.5) suggests that the mass transfer resistance, for both systems, is concentrated at the fluid/solid phase surface.