Adsorption of acid dyes onto bentonite modified with polycations: Kinetics study and process design to minimize the contact time

The adsorption kinetics of two acid dyes, Acid Scarlet GR and Acid Dark Blue 2G, onto a bentonite modified with poly-epichlorohydrin-dimethylamine (EPI-DMA) was studied. The pseudo second-order model showed a high degree of correlation with the experimental data for the whole adsorption process, whereas the intraparticle diffusion model presented two steps with two different diffusion rate constants indicating that the intraparticle diffusion may be involved in the adsorption process during the first 15 min. A two-stage batch adsorber was designed based on the second-order kinetics and was optimized to minimize the total contact time.