Isotherm, Kinetics and Thermodynamic Studies of Congo Red Dye Adsorption onto Zeolite/Activated Carbon Hybrid Adsorbent

Abstract

The rapid growth of industrial activities has significantly increased the volume of wastewater discharged into natural water bodies, creating serious environmental and public health challenges worldwide. This study focused on the application of Zeolite Y/Coconut Shell Activated Carbon (CSAC) hybrid adsorbent for the removal of Congo Red Dye from textile wastewater. Activated carbon was produced from coconut shell through phosphoric acid activation and subsequently combined with zeolite at different proportions to produce hybrid adsorbents, through mechanical mixing and wet impregnation method. Batch experiment was carried out to study the effect of process variables (adsorbent dosage, contact time, solution pH, and temperature) on adsorption of Congo Red Dye onto the hybrid adsorbents. Adsorption isotherm, kinetics and thermodynamic models were employed to analyse the experimental data obtained from the batch adsorption study. The study revealed that the adsorbents effectively removed the investigated dye from aqueous solution, recording removal efficiency of 91.36 % at adsorbent dosage of 0.8 g/50 mL, pH of 4, contact time of 60 mins and temperature of 25 ^oC and a monolayer adsorption capacity of 30.2 mg/g. The adsorption process was found to follow Langmuir isotherm and Pseudo-second-order kinetic models. Thermodynamic studies revealed exothermic and non-spontaneous behaviour; however, the reaction was found to be feasible at low temperature.