Adsorption of methylene blue dye onto bentonite clay: Characterization, adsorption isotherms, and thermodynamics s tudy by using UV-Vis technique

Abstract

This study uses the UV-Vis technique to describe the elimination of methylene blue dye from an aqueous solution by adsorption on an Iraqi bentonite clay surface. The batch approach was used to conduct adsorption studies carried out to evaluate the influence of factors of experimental like contact time (0–90 min), clay dose (0.1–0.35 g), and initial dye concentration (10–125 mg L-1) at the range of temperatures (25-40oC). The Langmuir and the Freundlich isotherms were used to analyze the data; the Langmuir isotherm (R2 = 0.998) proved more appropriate for the equilibrium data. The thermodynamic properties of the adsorption process, including Gibbs free energy (ΔGO), entropy(ΔSO), and enthalpy (ΔHO), were also studied. Since the (ΔGO) and (ΔHO) values were negative, it was clear that the adsorption process constituted an exothermic, spontaneous reaction. This investigation revealed that Iraqi bentonite clay effectively removed the dye methylene blue because of its high surface area. Methylene blue may be removed with an adsorption efficiency of up to 99.39 % at 25oC. By employing bentonite clay as an adsorbent surface, this research offers practical adsorption technology that is affordable and effective for treating wastewater.