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.
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
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