Thermodynamic investigation of the removal of Azure A dye from aqueous solution

In this study, rice husk was used as sorbent to remove Azure A from aqueous solution by batch sorption technique. It was seen that the removal of thionine increased with increasing initial dye concentration (from 5 to 25 mg/l), solution pH (from 2 to 7), solution temperature (from 10 to 55 °C) and sorbent dose (from 0.1 to 0.50 g/50 ml). The maximum dye removal was reached at 60 min. Sorption isotherms were analyzed by Langmuir, Freundlich and Temkin models at different temperatures of 10, 15, 20, 25, 35, 45 and 50 °C. Moreover, the thermodynamics of sorption were also studied. It was found that the values of standard free energy (DGo ) were negative for rice husk. The values of standard enthalpy (DHo ) and entropy (DSo ) were found to be positive, and the obtained results were interpreted in detail. Thermodynamic studies suggested the spontaneous and endothermic nature of adsorption of Azure A by treated rice husk.

Keywords:

Rice husk , Azure A , Sorption potential , Thermodynamic