Adsorption of dyes Basic blue 9 and Congo red onto thermal power plant waste: Kinetic, equilibrium and Thermodynamics parameters

The adsorption of congo red (CR) and basic blue 9 (BB9), onto thermal power plant waste at temperatures 308, 313 and 318K has been studied. Batch adsorption studies were conducted to evaluate the different parameters such as effect of contact time, initial concentration and adsorbent dose. The monolayer saturation capacity was found to be 2.11 and 4.88 mg/g for BB9 and CR. Adsorption kinetic of dyes followed pseudo second order kinetics. The Langmuir, Freundlich, Temkin, D-R and Generalized isotherms were applied to describe the equilibrium isotherm and the values of various constants so obtained increase with increase in the temperature insinuated that adsorption process is countenanced at high temperature. Values of the change in entropy (Lambda S) and heat of adsorption (Lambda H) for BB9 and CR adsorption on fly ash(FA) were positive suggesting the adsorption process to be endothermic. The high negative value of change in Gibbs free energy (Delta G) indicates the feasible and spontaneous adsorption of these dyes.