Abstract
In this work, pure multiwalled carbon nanotubes (MWCNTs) were grafted poly acrylic acid to adsorb effectively Cu(II) ions from aqueous solution. The solubility of functionalized MWCNTs was 2500 mg/L in aqueous solution. Identified by FTIR, TGA, and titration, the surface grafted carboxyl groups were 1.25 mmol/g MWCNTs,and weight loss was 13%. The adsorption of Cu(II) onto functionalized MWCNTs was studied as a function of contact time, pH, ionic strength, MWCNT dosage, and temperature. The results show that Cu(II) adsorption onto MWCNT depends strongly on pH and MWCNT dosage. Cu(II) ions can easily adsorb onto MWCNTs prepared in alkaline solution. Kinetic data show that the adsorption process achieved equilibrium within less than 1minutes. The effect of ionic strength indicated that the Cu(II) adsorption onto functionalized MWCNT might include ion exchange. The Cu(II) adsorption capacity of functionalized MWCNTs was 17.62 mg/g, which is greater than that of pure CNTs, 3.4 mg/g. This reflects that functionalized MWCNT are more effective sorbents. The adsorption data fit Langmuir isotherm well. The thermodynamic analysis revealed the adsorption of Cu(II) ions onto functionalized MWCNTs is an endothermic and spontaneous process. Results of desorption study showed that Cu(II) ions could be removed from MWCNTs by 0.5 mol/L nitric acid and 84% sorption capacity of MWCNTs remained after 5 cycles.