Abstract
SEM and TEM micrographs of SWCNTs and MWCNTs. [Display omitted]
•MWCNTs and SWCNTs used as adsorbent for the removal of Cr (VI) ion.•The maximum efficiency of adsorbent was noticed at pH 2.5.•Specific surface area (BET) of SWCNTs and MWCNTs were 700 and 270m2/g respectively.•qm (Maximum adsorption capacity) of MWCNTs and SWCNTs was 1.26 and 2.35mg/g respectively.•Cr (VI) ion removal percentage decreased in the presence SO42− ion.
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, SO42−. 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.