Bio-waste derived adsorbent materials for waste water treatment

Corn cobs were used as a source to prepare activated carbon by physical and\ud chemical activation methods. The physical activation was employed with CO2 and\ud steam at high temperature of 1,173K while chemical activation with nitric acid and\ud hydrogen peroxide at ambient temperature. The adsorption studies of a basic dye,\ud methylene blue, on the activated carbon were investigated. The effects of various\ud experimental parameters like contact time, adsorbent dosage, MB concentration,\ud temperature and pH were studied using batch adsorption experiments. The\ud characterization of the activated carbon was accomplished by using BET-N2\ud adsorption, Temperature programmed decomposition (TPD) and Thermogravimetric\ud analysis (TGA). The results obtained from adsorption studies follow Langmuir\ud adsorption isotherm with maximum monolayer capacity of 94.33 mg/g for CCC,\ud 64.93 mg/g for SCC, 7.02 mg/g for NCC and 4.04 mg/g for PCC. The kinetics of\ud adsorption was analyzed by different kinetic models like pseudo first order, pseudo\ud second order, intraparticle diffusion and Evolich. Among these, pseudo second order\ud was found to be the most appropriate to study the adsorption of MB on physically\ud activated carbon. The process was found to be endothermic with enthalpy change,\ud ΔH (kJ mol-1) of 43.27 (CCC), 38.45 (SCC), 151.63 (NCC) & 72.29 (PCC) and\ud entropy change, ΔS (kJ mol-1) of 1.57 (CCC), 1.33 (SCC), 5.09 (NCC) and 2.41\ud (PCC) for a temperature change of 300-330 K. The negative value of ΔG (kJ mol-1),\ud of -29.92 (CCC), -11.14 (SCC), -7.09 (NCC) and -2.14 (PCC), suggests the\ud spontaneous adsorption of MB on activated carbon