(749f) Adsorption of Aniline, Phenol, 4-Chlorophenol and 4-Nitrophenol Onto Granular Activated Carbon: Isotherm, Thermodynamics and Relationship with Solvatochromic Parameters

The present paper deals with the equilibrium adsorption of aniline (AN), phenol (P), 4-chlorophenol (4CP) and 4-nitrophenol (4NP) from aqueous solution onto granular activated carbon (GAC). Redlich–Peterson isotherm model represented the equilibrium data for AN and 4NP; and Temkin model was found to be the best for P and 4CP. The change in entropy, heat of adsorption and Gibb’s free energy (ΔG₀)  for adsorption have been determined. The high negative value of change in ΔG₀ indicated the feasible and spontaneous adsorption of AN, P, 4CP and 4NP adsorption onto GAC. Adsorption process was found to be endothermic for all the adsorbates. The linear solvation energy relationships (LSER) models based on solvatochromic parameters have been used to predict the values of the adsorption coefficient (K_D) of all the adsorbates onto GAC. The adsorption behavior of AN, P, 4CP and 4NP strongly depended upon the intrinsic molar volume (V_i). Also, hydrogen bonding between the adsorbates and the GAC was found to have significant role in the adsorption behavior.