Ability of a montmorillonitic clay to interact with cationic and anionic dyes in aqueous solutions

A montmorillonitic clay in raw and treated forms (size-fractionated, organoclay, Al pillared) was evaluated as adsorbent for cationic (toluidine blue TB and malachite green - MG) and anionic (Congo red - CR) dyes. A thorough characterization using XRD, SEM-EDS, N-2 adsorption, and FTIR of the considered samples was realized, all highlighting the structural changes after various treatments. UV-VIS analysis demonstrated the interaction between dyes and the adsorbent surface. The investigation of the effects of various experimental parameters using a batch adsorption technique showed that ON has a high adsorption potential for cationic dyes (33 and 39 mg/g in case of TB and MG, respectively). The kinetic study indicated that the adsorption process followed the pseudo-second-order model, while Freundlich isotherm showed a favorable adsorption. The calculated values of Gibbs free energy suggested also that the adsorption is spontaneous and is more favorable at higher temperatures. (c) 2017 Elsevier B.V. All rights reserved.