Removal of nickel(II) from aqueous solution by carbon nanotubes

Abstract

Single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) were oxidized by NaClO solutions and were employed as sorbents to study sorption characteristics of nickel(II) from aqueous solution. The surface properties of CNTs such as functional groups, total acidic sites and negatively charged carbons were greatly improved after oxidation, which made CNTs become more hydrophilic and resulted in sorption of more Ni2+. The amount of Ni2+ sorbed onto oxidized CNTs increased with a rise in agitation speed, initial Ni2+ concentration and solution pH in the range 1-8, but decreased with a rise in CNT mass and solution ionic strength. The sorption mechanisms are complicated and appear attributable to electrostatic forces and chemical interactions between the Ni2+ and the surface functional groups of the CNTs. The oxidized SWCNTs and MWCNTs have shorter equilibrium time and better Ni2+ sorption performance than the oxidized granular activated carbon, suggesting that both NaClO oxidized CNTs are efficient Ni2+ sorbents and that they possess good potential applications in water treatment. (c) 2006 Society of Chemical Industr

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.…”

“…The lead sorption capacity on NPC is significantly higher (2000 μeq/g) than on these CNTs. Lu and Liu [19] and Lu and Chiu [7] reported nickel and zinc sorption capacity on CNTs as 1630 μeq/g and 1335 μeq/g, respectively, at pH 7 over the equilibrium concentration of 200-2200 μeq/L which is comparable to that observed in this study for NPC (1428 and 2000 μeq/g, respectively). It is thus established that, by virtue of its unique morphology, NPC has a significant sorption potential for heavy metals which is superior or comparable to the literature reported values for CNTs.…”

“…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+ .…”