Removal of noxious Cr (VI) ions using single-walled carbon nanotubes and multi-walled carbon nanotubes

The adsorption capacity of two efficient adsorbents namely MWCNTs and SWCNTs for the rapid removal of noxious Cr (VI) ion from the polluted aqueous source was well studied and investigated. The impact of several influential parameters such as contact time, initial pH, initial Cr (VI) ion concentrations and the adsorption capacity of the adsorbent in the presence of competing anion was well elucidated and optimized. It was observed that the removal of efficiency of Cr (VI) ion depends on the pH of solution and the maximum efficiency was noticed at pH 2.5. Furthermore, the uptake of Cr (VI) ion was hindered in the presence of the competing anion, SO₄^2-. Experimental equilibrium data were fitted to four different isotherm models by linear regression method, however, the adsorption equilibrium data were well interpreted by the Langmuir model. The maximum adsorption capacity of Cr (VI) ion by MWCNTs and SWCNTs was 1.26 and 2.35mg/g respectively, which is calculated by the Langmuir isotherm model. Kinetic studies are well suited and found in good agreement with pseudo-second order. The results evidently indicated that MWCNTs and SWCNTs would be suitable adsorbents for Cr (VI) ion in wastewater under specific conditions.