REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTIONS USING YEMEN BENTONITE

Abstract

Removal of Methylene Blue (MB) from aqueous solutions using Yemen bentonite as low-cost adsorbent have been studied as a function of temperature, particle size and solution pH .  The adsorption capacity increased with increasing temperature (15 to 45˚C ) and solution pH value  (2 to 12) and decreasing particle size (500-710 to 80-125). The maximum adsorption capacity was 500.0 (mg.g^-1) at T = 25˚C, dp = 250-355 μm and pH = 12. The experimental data were analyzed by Langmuir, Freundlich, Temkin and Redlich-Peterson isotherms, and found that the Redlich-Peterson isotherm best fit the experimental data over the whole concentration range with R² values lie between 0.9986 and 0.9999. Thermodynamic parameters such as standard Gibbs free energy (ΔG˚), standard enthalpy (ΔH˚), and standard entropy (ΔS˚) were calculated. The thermodynamic parameters of MB/clay system indicated spontaneous and endothermic nature of the adsorption process. The results demonstrate that Yemen bentonite is effective in the removal of MB from aqueous solutions and can be used as alternative of high cost commercial adsorbents.