Preparation of high surface area mesoporous activated carbon: kinetics and equilibrium isotherm

Activated carbon prepared from palm shell by phosphoric acid impregnation, at significantly favorable experimental conditions is characterized for the porous nature and adsorption of methylene blue dye molecules. The activation is carried out using a 2-stage activation process with the activation in a self-generated atmosphere. An activation temperature of 500 degrees C, with an activation time of 75 minutes using a phosphoric acid impregnation ratio of 3 has yielded an activated carbon having unique characteristics. An activated carbon with a yield of 48 , total pore volume of 1.9 cm(3)/g, surface area of 1956 m(2)/g, an average pore diameter of 3.8 nm, with the ratio of the mesopore to the total surface area in excess of 75 has been prepared. The activated carbon exhibits a high methylene blue equilibrium adsorption capacity of 438 mg/g with the adsorption isotherm increasing with an increase in the adsorption temperature. Among the various adsorption isotherm models, the Langmuir model is able to explain the adsorption process well, evidenced by the proximity of the model with the experimental data. Among the different kinetic models tested with the experimental kinetic data, a pseudo-second-order model is found to fit the experimental data with close proximity.