Removal properties of methylene blue from aqueous solutions by organomodified montmorillonite: Isotherm, thermodynamics and kinetic studies

Abstract

Adsorption of Methylene Blue (MB) from water via batch adsorption experiments onto montmorillonite (MMT) and organomodified montmorillonite (OMMT) was investigated. The organomodified montmorillonite was synthesized by montmorillonite and n-hexadecyltrimethylammonium chloride. The organomodified montmorillonite was characterized by FT-IR, XRD, ATG, SEM, and Nitrogen adsorption measurements (BET). Studie concerning the factors influencing the adsorption capacitie of montmorillonite and organomodified montmorillonite, such as the contact time, adsorbent dosage, initial dye concentration, pH, and temperature were systematically investigated and discussed. The experimental results show that the percentage of dye removal increases with the increasing the amount of sorbent. Adsorption was pH dependent. The results revealed that organomodified montmorillonite demonstrated high adsorption capacities toward basic dyes, while montmorillonite exhibited sorption capacities lower than organomodified montmorillonite.The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model. The kinetics data were analyzed using pseudo-first and pseudo-second-order models. It was best described by the pseudo-second-order model. Thermodynamic parameters ΔG°, ΔH° and ΔS° were calculated for the adsorption of Methylene Blue on montmorillonite and organomodified montmorillonite; the value of ΔG° showed the spontaneous nature of adsorption for both sorbents and the process was endothermic.