Three types of carbon materials were used in this work: activated carbon, polymer based carbon xerogel, and carbon nanotubes. The commercial activated carbon was NORIT C-GRAN NC01-125 (sample AC) that is a granular activated carbon with a particle size from 0.5 to 2 mm, prepared from wood, using a chemical activation process with phosphoric acid. A carbon xerogel was synthesized by the polycondensation of resorcinol and formaldehyde [32,33], at pH 6.5 (sample CX). The gelling and curing step was carried out during 1 week in an oven, starting at 65 ◦C, for 1 day, and increasing ∼20 ◦C each day, until 150 ◦C, and then maintaining at that temperature for 3 days. The red brown opaque solid gel was then cut and chopped. Carbonization of the gel powder was carried out in a flow of N2 atmosphere (100 cm3 min−1) by heating to 800 ◦C with a rate of 10 ◦C min−1, stepwise, and keeping it isothermally for 6 h. Multi-walled carbon nanotubes were prepared from ethylene by fluidized bed-catalytic chemical vapor deposition on alumina supported iron catalyst powders, as described elsewhere.