Adsorption of Reactive Black 5 dye from aqueous solutions with a clay halloysite having a nanotubular structure: Interpretation of mechanism, kinetics, isotherm and thermodynamic parameters

In this study, the removal of Reactive Yellow 145 (RB5) dye found in wastewater with halloysite clay mineral (HCM), which is easily available and cheap, was investigated. For the characterization of the adsorbent; SEM, BET, XRD, and Zeta Potential Contact Angle analyses were performed. The effect of parameters such as solution pH, temperature, contact time, initial dye concentration, and adsorbent amount on the adsorption of RB5 dye onto HCM was investigated. It has been determined that the Langmuir isotherm fits the experimental data better than other applied isotherms in mathematically defining the adsorption equilibrium. In the Langmuir isotherm, the adsorption capacity was 24.9 mg/g. To find the most suitable kinetic model for the study using experimental data, Pseudo-First-Order, Pseudo-Second-Order, Elovich, and Intra-Particle Diffusion models were tested, and it was decided that the most suitable model would be the Pseudo-Second Order kinetic model. Again, using experimental data, thermodynamic parameters (ΔG°, ΔH°, ΔS°) were calculated, and it was determined that the adsorption process was spontaneous and endothermic.