Removal of Pb2+ from contaminated water using modified multiwalled carbon nanotubes

Abstract

The effects of ethylene diamine (EDA), poly (amidoamine) (PAMAM) dendrimer and polyvinyl alcohols (PVA) modified multi-walled carbon nanotubes (MWCNTs) were investigated for the adsorption of Pb2+ ions in synthetic water and subsequently, in wastewater samples. The prepared MWCNTs nanocomposites were confirmed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The concentration of Pb2+ ions were measured by flame-atomic absorption spectroscopy (F-AAS) and inductively coupled plasma-mass spectroscopy (ICP-MS), respectively. Removal of Pb2+ ions from synthetic solutions was carried out by varying parameters such as pH, initial metal ion concentration, contact time and adsorbent dosage. The maximum removal of Pb2+ ions was achievable at a pH of 6.5. The removal efficiency increased (more than 90%) with metal ion concentration; and reached equilibrium at 40 mg/L Pb2+ ions in all nanocomposites. Equilibrium was reached within the first 30 minutes, (at a low adsorbent dosage of 0.03 g) and remained constant in all nanocomposites. The EDA-MWCNTs nanocomposite yielded more than 90% Pb2+ ions removal from synthetic solutions as compared to both PAMAM dendrimers and polyvinyl alcohols. The analysis of wastewater indicated that the concentration of Pb2+ before treatment was ranging from 4.09 to 35.73 µg/L. The nanocomposite was able to remove 99% of Pb2+ from wastewater. Concentrations of Pb2+ varied from 0.200 - 0.234 µg/L after adsorption, which are below acceptable levels recommended by World Health Organisation (WHO), i.e, 10 µg/L Pb2+ .