Enhancement of sorption of the azoic dye (Azucryl Red) by natural and calcined hyper-aluminous kaolins

Abstract

Purpose. To remove of basic textile dye Azucryl Red (AR) from aqueous solutions using hyper-aluminous kaolins from Charente deposits (France) in natural and calcined states. Methodology. Batch interactive parameter pH, pHpzc contact time, dye concentration, adsorbent loading and temperature are taken to obtain optimums for the AR adsorption process in natural and calcined kaolin named respectively Kca, Kcm, Ckca, and Ckcm. Findings. The adsorption equilibrium was established in 7 min while the second-order kinetic model better described the adsorption kinetics for all kaolins with the chemisorption process. The adsorption isotherm of the results obtained corresponds better to the Langmuir model. The maximum quantity retained was 67.97 and 73.38 mg/g respectively for Kcm and Kca samples. Moreover, in the calcined state, the maximum quantity retained was 76.66 and 75.64 mg/g respectively for the calcined kaolin CKcm and CKca samples for a temperature of 298 K and pH = 6. The thermodynamic nature of the adsorption process was determined by calculating H, S and G° values. The positive value of H° confirms the fact that adsorption is endothermic spontaneous which is enhanced at higher temperatures. Originality. The heat treatments of the different kaolins at 400 °C enhance the adsorption process. Therefore, the results indicate that Ckcm performed with the highest adsorption capacity in the removal of the dye, followed by Ckca. Practical value. Adsorption processes of toxic Azucryl Red dye in the aqueous medium using natural and calcined hyper-aluminous kaolins at 400 °C were investigated. Optimization and modeling of the adsorption parameters with the theories by Langmuir, Freundlich and Elovich allowed us to find the optimal experimental conditions for sorption. Our results therefore indicate that the adsorption process of Azucryl red dye from aqueous solutions was enhanced when calcined kaolin at 400 °C containing organic matters was used.