Performance of Libyan Bentonite as Adsorbent for Methylene Blue Dye: Isotherms, Kinetics and Thermodynamic Studies

Abstract

This study provides an overview of natural and activated of Umm-Al- Razam, Libyan bentonite clay (north east of Libya region), as an offered adsorbent of anionic dye, methylene blue (MB) dye from aqueous solution; where the adsorption isotherms applied experimentally to investigate the effect of adsorbent dosage in a batch mode range from (0.1-1.2g), pH (1,3,5,7,9 and11), initial MB concentration (5,10,20,30,40 and 50ppm), temperature (25,35,45 and 55oC) and contact time range from (5 - 120min).The Characterization of natural Libyan bentonite (NLBn) and activated Libyan bentonite (ALBn)) was carried out firstly by infrared spectroscopy (FT-IR), electronic scanning microscopy(SEM) and X-ray diffraction (XRD) technique. The data analyzed by different models (Langmuir, Freundlich and Temkin) to describe the equilibrium isotherms and thermodynamic parameters such as Gibbs free energy change (ΔG) The data analyzed by different models (Langmuir, Freundlich and Temkin) to describe the equilibrium isotherms and thermodynamic parameters such as Gibbs free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) of the system were calculated. The results showed the equilibrium adsorption data of (NLBn) was fit better the Langmuir adsorption model but for (ALBn) was fit better to Temkin. The adsorption capacity for the removal of MB was 4.3 mg/g and 4.9 mg/g at different concentration on (NLBn) and (ALBn) respectively. Kinetics of dye removal was investigated and found to follow pseudo second order rate constant. The sorption and desorption capacity of MB was found to be 95% and 99% by both (NLBn and ALBn) respectively.