Investigation on adsorption and regeneration performances of multi-walled carbon nanotubes by supercritical water technique

In this paper, adsorption and regeneration characteristics of multi-walled carbon nanotubes (MWNTs) used as adsorbent were investigated for the removal of 1, 3-benzenediol (BDO) from water by the supercritical water (SCW) technique. FTIR, XPS, SEM and dispersion stability tests were used to characterize the structure and surface morphology of CNTs. The results showed that CNTs surfaces were slightly activated and strongly etched in supercritical water system. The adsorption capacity of SCW-treated CNTs was higher than that of raw CNTs. The adsorbed amounts for treated CNTs and raw CNTs samples at the same initial concentration of 60 mg/L were ca. 16.42 and 7.30 mg/g, respectively. The BDO adsorption of treated CNTs was due to the physical adsorption. The experimental data fit Freundlich isotherm model better than Langmuir one. The loaded adsorbent could be efficiently desorbed and regenerated by SCW technique. Therefore, SCW is a promising and environmentally friendly technique for the improvement of adsorption and regeneration of CNTs.