Process optimization of thermal regeneration of spent coal based activated carbon using steam and application to methylene blue dye adsorption

Spent coal based activated carbon from the silicon industry has been regenerated using thermal regeneration technique with steam as activating agent. The response surface methodology (RSM) technique is applied to optimize the regeneration process. The optimization is performed for maximizing the carbon yield and the iodine adsorption capacity. The optimized conditions are observed to be a regeneration temperature of 983°C, regeneration time of 135min and steam flow rate of 2g/min, while the corresponding yield and iodine number are 61% and 1053mg/g respectively. The BET surface area corresponds to 1233m²/g, with pore volume of 0.82cm³/g. The regenerated carbon is heteroporous with the micropore volume contributing to 64.86%. The regenerated carbon is tested with methylene blue dye adsorption to assess its potential to liquid phase adsorption. The equilibrium adsorption capacity for methylene blue was estimated to be 375.93mg/g, with the adsorption isotherm following the Langmuir isotherm model. The adsorption kinetic is 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, typically for color removal in waste water streams.