Adsorption of Blue Cationic Thiazine Dye from Synthetic Wastewater by Natural Iraqi Bentonite Using Response Surface Methodology: Isotherm, Kinetic, and Thermodynamic Studies

Dyes are poisonous and carcinogenic substances that are harmful to human health. Therefore, this study demonstrates using bentonite as a natural absorbent to remove methylene blue (MB), blue cationic thiazine dye, by studying the effects of different adsorbed doses, contact times, initial concentrations, pH, and temperatures on the removal efficiency. According to the kinetics and thermodynamics results, the process was represented by a pseudo-2nd-order equation and found exothermic and spontaneous. The experimental equilibrium adsorption capacity was 56.90 mg/g while the maximum one was 93.55 mg/g by the Langmuir isotherm. The optimum conditions are 40.7 mg/L, 0.55 g, pH 8, and 30 min with the removal of 99.5% while ANOVA was utilized to find correlations describing the MB removal.