Abstract
M.Sc. (Nanoscience)
Lead (Pb (II)) pollution has been persistent for years due to its use in many applications and is thus deposited into water streams/aqueous environments through industrial effluents. It is toxic to humans, terrestrial animals and aquatic species. Exposure results in adverse effects which may cause permanent damage to the functioning of the species. Thus, stringent measures to combat lead pollution have been put in place by the World Health Organisation (WHO). Thus, the requirements for new highly selective and efficient technologies to eradicated Pb (II) contamination from aqueous environments are essential.
Multi-walled carbon nanotubes (MWCNTs) have been viewed as potential adsorbents due to their unique properties. The properties of MWCNTs are tuneable which allows for alteration of the surface chemistry to increase selectivity and affinity of the metal ions for the MWCNTs. Modified multi-walled carbon nanotubes were used as adsorbents for the uptake of Pb (II) ions from aqueous solutions. The multi-wall carbon nanotubes were modified through oxidation and covalent bonding to impart different functional groups onto the surface. The MWCNTs were modified with nitric acid (HNO3) and diphenylcarbazide (dpc).
The surface chemistry and morphology analysis was carried through Fourier transform spectroscopy (FTIR), RAMAN spectroscopy, Brunauer Emmett-Teller (BET), X-Ray diffraction spectroscopy (XRD), Thermal gravimetric analysis (TGA), CHN elemental analyser and Scanning electron microscopy (SEM). The adsorption studies were carried out through batch adsorption studies and the determination of the concentration of Pb (II) was conducted using the Flame atomic absorption spectroscopy (FAAS).
Factors influencing the adsorption such as pH, adsorbent dosage, contact time, initial metal concentration were studied. The adsorption of Pb2+ ions by both adsorbents is pH dependent and optimum adsorption is observed at pH 7. The optimum adsorption efficiencies of Pb2+ ions obtained on coo-MWCNTs and dpc-MWCNTs were 99.3% and 93.8% respectively. The adsorption process may be described by Langmuir, Temkim and Elovich adsorption isotherms which indicate that adsorption process was through both chemisorption and physisorption. The time dependent kinetic model fitted well in the...