Removal of Zinc(II) from Aqueous Solution by Purified Carbon Nanotubes:  Kinetics and Equilibrium Studies

Abstract

Single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) were purified by sodium hypochlorite solutions and were employed as sorbents to study the kinetics and equilibrium of Zn2+ sorption from aqueous solution. The amount of Zn2+ sorbed onto CNTs increased with a rise in temperature. Using the same conditions, the Zn2+ sorption capacity of CNTs was much greater than that of commercially available powdered activated carbon, reflecting that SWCNTs and MWCNTs are effective sorbents. The thermodynamic analysis revealed that the sorption of Zn2+ onto CNTs is endothermic and spontaneous. The sorption/desorption study showed that the Zn2+ ions could be easily removed from the surface site of SWCNTs and MWCNTs by a 0.1 mol/L nitric acid solution and the sorption capacity was maintained after 10 cycles of the sorption/desorption process. This suggests that both CNTs can be reused through many cycles of water treatment and regeneration.

A highly efficient and versatile carbon nanotube/ceramic composite filter

“…This would suggest that the current filter could be used in a faster stream whilst maintaining high efficiency (SI section S6). It would also be possible to have the same complete ion removal at higher injection rates by increasing the length of filter, alternatively increasing the temperature may also improve adsorption efficiency as was previously shown by Lu et al [32] for Zn 2+ .…”

Potential of carbon nanomaterials for removal of heavy metals from water

“…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].…”

“…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.…”

“…Activation causes modification in the surface morphology and surface functional groups and causes removal of amorphous carbon. Activation of CNTs under oxidizing conditions with chemicals such as HNO 3 , KMnO 4 , H 2 O 2 , NaOCl, H 2 SO 4 , KOH, and NaOH have been widely reported [8,21,26,27]. During activation, the metallic impurities and catalyst support materials are dissolved and the surface characteristics are altered due to the introduction of new functional groups [24,26].…”

“…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+ .…”