Adsorption of zinc(II) from water with purified carbon nanotubes

Potential of carbon nanomaterials for removal of heavy metals from water

“…This transition to hydrophilic surfaces is possibly due to the introduction of acidic oxygen containing functional groups. Similar observations were reported by various researchers [7,19,21,25] for oxidation of CNTs with HNO 3 . These surface modifications are also reported to enhance the sorption of metal (M 2+ ) ions.…”

“…4 for lead sorption. Similar time scale, i.e., 1 h equilibration time, for sorption of metal ions on CNTs has been reported by various researchers [7,19] although longer time periods have also been reported [21,22] for lead, copper and cadmium sorption on CNTs.…”

“…CNTs were found to be superior sorbents for inorganic pollutants such as fluoride [18], and several divalent metal ions [7,8,[19][20][21][22][23][24][25]. Li et al [24] reported that CNTs with more defects and poor quality possess higher surface area and exhibit better lead sorption capacity compared to aligned CNTs.…”

“…Maximum sorption capacity for heavy metals determined based on Langmuir model varies based on the type of metal. The maximum sorption capacity for cadmium, lead, nickel and zinc is reported to be in the range of 10-11 mg/g [21], 49-97 mg/g [20,22,24], 9-47 mg/g [19,25] and 11-43 mg/g [7,8], respectively. Hence, with CNTs as sorbent, metal ion uptake followed the order Pb 2+ > Ni 2+ > Zn 2+ > Cd 2+ .…”

“…Moreover, it may cause extreme weakness, dermatitis, headache, dizziness and respiratory distress [6]. Zinc toxicity from excessive ingestion is less common, however, it may cause damage to various systems in the human body [7,8].…”