Efficient anionic dye adsorption on natural untreated clay: Kinetic study and thermodynamic parameters

► Clays generally adsorb cationic dyes but Fouchana natural clay adsorbs anionic dyes. ► The adsorption kinetics of reactive dyes on Fouchana clay was fast. ► The adsorption process was spontaneous, exothermic and physical in nature. ► The main process involved is adsorption on the broken edges of clay particles. ► Fouchana clay is an efficient low cost adsorbent for anionic reactive dyes.