Bio-waste derived adsorbent material for methylene blue adsorption

Corn cobs were used as a source to prepare activated carbon by physical activation methods with CO2 and steam at high temperature of 1173 K. The adsorption studies of a basic dye, methylene blue, on the activated carbon were investigated. The effects of various experimental parameters like contact time, adsorbent dosage, MB concentration and temperature were studied using batch adsorption experiments. The characterization of the activated carbon was accomplished by using BET-N-2 adsorption, Temperature programmed decomposition (TPD) and Thermogravimetric analysis (TGA). The results obtained from adsorption studies follow Langmuir adsorption isotherm with maximum monolayer capacity of 100 mg/g for CCC and 75.5 mg/g for SCC. The kinetics of adsorption was analyzed by different kinetic models like pseudo first order, pseudo second order, intraparticle diffusion and Evolich. Among these, pseudo second order was found to be the most appropriate to study the adsorption of MB on physically activated carbon. The process was found to be endothermic with enthalpy change, Delta H (kJ/mol) of 43.27 (CCC), 38.45 (SCC), and entropy change, Delta S (kJ/mol) of 1.57 (CCC), 1.33 (SCC) for a temperature change of 300-330 K. The negative value of Delta G degrees (kJ/mol), of -29.92 (CCC), -11.14 (SCC), -7.09 (NCC) and -2.14 (PCC), suggests the spontaneous adsorption of MB on activated carbon. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.