Removal of brilliant green (BG) by activated carbon derived from medlar nucleus (ACMN) - Kinetic, isotherms and thermodynamic aspects of adsorption

Experimental investigations were undertaken to adsorb Brilliant Green (BG) a toxic dye from aqueous medium using activated carbon derived from the medlar nucleus (ACMN). The adsorption was used to remove BG using ACMN as bio-adsorbent to replace activated carbon still expensive. The prepared adsorbent was characterized by the BET surface area measurement, FTIR spectroscopy and X-ray diffraction. Various parameters such as the initial dye concentration (110-200 mg/L), adsorbent dose (1-6 mg/L), initial pH (2-9) and temperature (298-318 K) were studied to observe their effects on the BG adsorption. Batch studies were conducted in order to determine the optimal parameters required to reach the adsorption equilibrium. The maximum adsorption capacity of ACMN for the BG adsorption at 298 K was found to be 833.15 mg/g. The adsorption kinetic data were analyzed by using several kinetic models namely the pseudo-first-order, pseudo-second-order, Elovich equation, intraparticules diffusion model. It was established that the adsorption obeys the pseudo-second-order kinetic model. The evaluation of thermodynamics parameters such as the free energy Delta G degrees (-10.584 to -6.413 kJ/mol), enthalpy Delta H degrees (36.439 kJ/mol) and the change of entropy (0.1438 kJ/mol K) indicated a spontaneous and endothermic nature of the reaction with a chemisorption process. The present adsorbent may be considered as an alternative for the better performance of the BG removal from aqueous medium.