Equilibrium and synthetic studies of methylene blue dye removal using ash of walnut shell

Background and Aims: Wastewater treatment and color removal is always one of the most important measures to control pollution from industrial effluents especially in the textile and dyeing industry. This industry is one of the largest producers of organic compounds and color. For this reason, their treatment conditions are complicated and difficult. This study investigates the efficacy of ash produced from walnut shell as a natural adsorbent in color removal of methylene blue (MB) from aqueous solutions in the experimental condition.Materials and Methods: At present study, effect of various operating parameters such as pH (2-13), reaction time (30-250 min), amount of adsorbent dosage (0.2-5 g/l) and initial concentration of dye (25-250 mg/l) on color removal from synthetic wastewater were studied. Also the adsorption behavior of dyes by isotherms of Freundlich and Langmuir and synthetic of adsorption were conducted using excel program and regression coefficient.Results: Maximum removal efficiency of methylene blue (93.25%) were achieved at optimal pH 10, reaction time 150 min, adsorbent dosage 3 g/l and initial dye concentration 100 mg/l. Data of this study was fitted with Langmuir and Freundlich isotherms and more fitted with Freundlich (R=0.8500). Also, kinetic adsorption study showed that for initial dye concentrations 100, 150 and 200 mg/l, pseudo-second order kinetic is more favorable (R2=0.9900).Conclusion: More than 90% removal efficiency for MB dye showed that this adsorbent is an effective natural compound and also inexpensive for treatment processes. Hence, using this technique and process was recommended for dye pollutants removal from aqueous environments.Key words: Walnut, methylene blue dye, adsorption kinetics, equilibrium isother