Regeneration of microwave assisted spent activated carbon: Process optimization, adsorption isotherms and kinetics

Microwave assisted regeneration of spent coal based activated carbon from the silicon industry has been attempted using steam as the regenerating agent. The response surface methodology (RSM) technique was utilized to optimize the process conditions and the optimum conditions have been identified to be a regeneration temperature of 950 °C, regeneration time of 60 min and steam flow rate of 2.5 g/min. The optimum conditions result in an activated carbon with iodine number of 1103 mg/g and a yield of 68.5% respectively. The BET surface area corresponds to 1302 m2/g, with the pore volume of 0.86 cm3/g. The activated carbon is heteroporous with a micropore volume of 69.27%. The regenerated carbon is tested for its suitability for adsorption of methylene blue dye molecule. The adsorption isotherms were generated and the maximum adsorption capacity was found to be 385 mg/g, with the isotherm adhering to Langmuir isotherm model. The kinetic of adsorption was found to match pseudo-second-order kinetic model. The results indicate potential application of the regenerated activated carbon for liquid phase adsorption involving high molecular weight compounds.