The re-activation was carried out in a horizontal furnace and the samples were heated (5◦C∕min) from room temperature to the Gnal re-activation temperatures (700◦C;800◦C;900◦C and 1000◦C) in nitrogen Aow (30 ml∕min). Samples were kept at the Gnal activation temperature for 2 h. After chemical activation, samples were washed with hot distilled water followed by 0:1 NHC1 solution. Finally, cold distilled water was repeatedly used to remove residual chemicals until the pH of Gltered water was below 7.5. The washed samples were dried at 120◦C for 12 h. The prepared samples were designated as AC, AC700, AC800, AC900 and AC1000 followed by their treated temperatures.