Isotherms, Kinetics and Thermodynamics of Methylene Blue Adsorption on Active Carbon from Polyfurfuryl Alcohol

Abstract

This study investigates the isotherm and kinetics of adsorption of methylene blue (MB) from aqueous system on polyfurfuryl alcohol carbon (PFAC). Experimental parameters like initial concentration of MB (1-3 mg/50 mL), reaction time (0-60 min.) and temperature (302-328 K) were studied for the adsorption process using isotherms, adsorption kinetics and thermodynamics. The results obtained show that adsorption of MB on PFAC fits both the Langmuir and Freundlich isotherms well but the Langmuir model explains the adsorption equilibrium data better. The experimental adsorption capacity of this active carbon for MB was 23.80 mg/g, equivalent to specific surface area 88.34 m²/g. The calculated thermodynamic values:  (– 9.0 kJ/mol.),  (– 19.20 J/mol.) and  (– 3.60 J/mol.), indicate exothermic and physical nature of adsorption as well as decreased randomness at the adsorbate-adsorbent interface. The sticking probability ( ) value (0.55) show that the probability of MB molecules to stick on the surface of this active carbon is high. The negative  values (– 5.78 to – 6.28 kJ/mol.K) at 302–328 K, confirms a spontaneous adsorption process dominated by physisorption. Adsorption of MB on PFAC was predominantly governed by pseudo-second order kinetics. This active carbon from polyfurfuryl alcohol shows potential for the removal of organic pollutants like MB from aqueous systems.