Agadir Clay Materials as a New Adsorbent to Remove Cationic and Anionic Dyes from Aqueous Solutions

This study investigated the potential use of clay minerals originated from barrage situated in Agadir (Morocco), as a low-cost, natural, eco-friendly and alternative adsorbent for removal of Methylene Blue (MB) and Congo Red (CR), respectively a basic and an acid dye, from aqueous solution within a batch process. The adsorbent was characterized by X-ray diffraction, BET surface area, scanning electron microscopy (SEM) and dispersive energy of spectroscopy (EDS). The effects of various experimental parameters were examined such as contact time, initial dye concentration, adsorbent concentration, solution pH, and temperature. In order to determine the best-fit-isotherm, the experimental data were analyzed by the Freundlich and Langmuir equations. The adsorption equilibrium was well described by the Langmuir isotherm model with maximum adsorption capacity of 125mg.g−1 for MB and 91mg.g−1 for CR, at room temperature. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order models. The pH heavily affects the adsorption capacity, the removal percentage reached 99.22% for MB at pH=10, and 98.97% for CR at pH=2. The values of activation parameters such as free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were also determined. However, the results pointed to the effectiveness of this Agadir Clay (AC) as an interesting alternative material with respect to more costly adsorbent used, for removing basic and acid dyes from aqueous solutions.