Adsorption of Methylene Blue in Aqueous Phase by Fly Ash, Clay and Walnut Shell as Adsorbents

Methylene Blue (MB) adsorption from aqueous phase was investigated using three types of adsorbents. Granular solid adsorbents were prepared from waste wood fly ash and clay. Experiments were conducted in a batch system for determining sorption equilibria. For continuous process, the adsorbents were packed in a column to remove MB from the synthetic wastewater. The fabricated adsorbents and also pretreated walnut shell were used to compare the performance of the packed adsorbents. The generated wastewater contained 4 mg/l of MB. The wastewater with flow rate of 18 ml/min was continuously pumped through the column using peristaltic pump for removal of dyes from aqueous phase. The effluent samples were collected with respect to time at a time interval of 2 min. The maximum adsorption capacity of clay, fly ash and walnut shell was 7.14, 7.87 and 5.78 mg/g, respectively. Langmuir and Freundlich adsorption isotherms were investigated to interpret the experimental equilibrium data. The obtained results revealed that the sorption data were well described by Freundlich model. Adsorption model represented by Langmuir model also depicted similar results. Results obtained from dynamic study in packed column indicated that the maximum and minimum removal efficiency of 90 and 53% was devoted to walnut shell and clay, respectively.