Determination of Thermodynamic Parameters of Phenol Adsorption onto Sewage Sludge based Adsorbent by different Methods

The aim of this study is the determination of thermodynamic parameters of the adsorption of phenol onto sewage sludge based adsorbent (SSBA) by different methods. Thermodynamic parameters are calculated from three equilibrium constants (Kc) that were derived from the isotherm constants of Langmuir (KL), the distribution coefficient (Kd) and Freundlich isotherm exponent (n). For this, removal of phenol from aqueous solutions by adsorption under batch equilibrium experimental conditions at 293, 303 and 328 K was investigated. All values obtained for ΔG° are negatives this indicated that the adsorption process of phenol on the SSBA is spontaneous and thermodynamically feasible process. We also note that as the temperature increases, the absolute value of ΔG° decreases, it shows that the adsorption is more spontaneous at low temperatures. All values of the standard enthalpy ΔH° are negative and less than 35 kJ.mol-1 which confirm that the process is an exothermic physisorption. The negative values of the standard entropy ΔS° clearly show that the arrangement of phenol molecules is more preferred on the surface of the adsorbent.