Natural mordenite-rich tuff as an alternative for removing textile dyes (Asucryl red): adsorption properties, kinetic and equilibrium studies

This work examines a tuff from the Tinebdar deposit located in Sidi Aich (east Algeria) for possible use as an alternative material for the adsorption of Asucryl red (a textile dye). Natural tuff represents an economic and environmentally friendly alternative compared to synthetic zeolites. The starting materials were characterized by means of powder X-ray diffraction, Brunauer-Emmett-Teller-specific surface area and pore diameter analysis. Batch experiments were performed and various parameters that have an effect on the adsorption process (i.e. pH, clay amount, contact time and initial concentration) were investigated. The <125 mu m grain-size fraction of the tuff contains 45 wt.% mordenite. The adsorption equilibrium was established in 10 min and the adsorption kinetics were better described by the secondorder kinetic model. The adsorption isotherm of the results obtained fits better to the Langmuir and Timkin models. The adsorption capacity q(t) varies from 60 to 70 mg g(-1) with temperature increasing from 293 to 333 K. The thermodynamic nature of the adsorption process was determined by calculating Delta H degrees, Delta S degrees and Delta G degrees values. The positive value for Delta H degrees confirms that the adsorption is endothermic.