Removal of internal caps during hydrothermal treatment of bamboo-like carbon nanotubes and application of tubes in phenol adsorption

► With the rise in burn-off, a progressive rise in nanotube surface polarity occurs. ► The removal of internal caps takes place mainly at higher burn-offs. ► Differential enthalpies of phenol adsorption on tubes are in the range of those determined for adsorption on graphite. ► The state of phenol in first adsorbed layer is close to solid for adsorption on closed tubes. ► This state progressively approaches the state of supercooled liquid after tube opening and with the rise in burn-off.