Isotherm, Thermodynamics, Desorption, and Disposal Study for the Adsorption of Catechol and Resorcinol onto Granular Activated Carbon

The present paper reports isotherm, thermodynamic, and disposal studies for the adsorption/desorption of catechol (C) and resorcinol (R) from aqueous solution onto/from granular activated carbon (GAC). Isotherm data were generated for C and R solutions having initial concentrations of C and R in the range of (0.18 to 9.08) mmol·L −1 for the GAC dosage of 10 g·L −1 at temperatures of (288, 303, and 318) K. The adsorption of C and R onto GAC was favorably influenced by an increase in temperature. Equilibrium data were well-represented by the Tempkin isotherm model. Values of the change in entropy (Δ S 0 ), heat of adsorption (Δ H 0 ), and Gibbs energy (Δ G 0 ) were determined. The desorption of C and R from GAC was studied by various solvents and a thermal desorption method. NaOH was found to be a better eluant for the desorption of C and R with a maximum desorption efficiency of 10.1 % and 11.4 %, respectively. Thermal desorption at 623 K was found to be better as compared to solvent desorption. GAC worked well for at least five adsorption−desorption cycles, with a continuous decrease in adsorption efficiency after each thermal desorption. Owing to its heating value, spent GAC can be used as a cofuel for the production of heat in boiler furnaces.