Abstract
The objective of this study was to investigate the effect of chloride ions (Cl−) on Cu2+ adsorption to carbon nanotubes (CNT). The isotherms showed a significant decrease in adsorption capacity on F-400, pristine, and acid-functionalized CNT in the presence of Cl−, but had little effect on alcohol-functionalized CNT. Several inductively coupled plasma (ICP) analyses measured the impurities concentration of (1) aqueous-phase isotherm solute, (2) as-received, and (3) acid-washed CNT solutions. Chemical-equilibrium-modeling software MINEQL+ calculations were applied to compare ICP results to complexes formation. The model suggested that some solid-phase residual-catalytic metals, such as Cr2+, after released in water from as-received CNT, formed aqueous-phase complexes and were readsorbed. The 18-metal ICP results were more than two orders of magnitude lower ( 5.1, when less Cu2+ ions are present in solution. scanning electron microscopy–energy dispersive X-ray spectroscopy analysis showed impurities on as-received F-400 and positively charged surface at pH 5.1 (pHpzc 7.1) explaining possible electrostatic attraction of Cl− ions, blocking adsorptive sites, reducing its adsorptive capacity for Cu2+.
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