Abstract
M.Sc. (Applied Chemistry)
Trace toxic metals have adverse effects on human health and the environment. Their
concentrations should be monitored so that their levels do not surpass the levels put in
place by the regulation committees for safety and health purposes. However, the
determination and removal of these toxic metals from the environment is challenging
because of the complexity of the real samples and low concentrations. Even with the
sophisticated analytical techniques such as inductively coupled plasma optical emission
spectrometry and inductively coupled plasma mass spectrometry, direct determination of
trace metals in complex matrices is difficult. Therefore, simple, affordable and efficient
methods are required for preconcentration of trace metals. In addition, multipurpose
adsorbents that are reusable are needed for both removal and preconcentration processes.
Therefore, the main aim of this work was to prepare or synthesise magnetic
nanomaterials for the removal and preconcentration of toxic trace metals from
environmental samples. In this study, different magnetic adsorbents were synthesized for
the removal preconcentration of copper, manganese, nickel, arsenic, cadmium and for the
lead and thallium. For the preconcentration of trace metals, solid phase extraction was the
method of choice because it presented attractive advantages such as its simplicity,
rapidness, efficiency, and cost-effectiveness. It can also be tuned for selectivity and
specificity by incorporating specific functional groups. The structural and morphological
properties of the adsorbent were investigated using X-ray powder diffraction (XRD),
scanning electron microscopy/ energy dispersion x-ray (SEM/EDX) Fourier transform
infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The
quantification of the metal was achieved using inductively coupled plasma optical
emission spectrometry.
The first objective was to synthesize Fe3O4-ZrO2 nanocomposite functionalized with 3-
aminopropyltriethoxysilane as a magnetic nanoadsorbent for removal of Cd(II), Cu(II), Mn
(II) and Ni(II) ions from aqueous solutions, acid mine drainage effluents, wastewater and
river water samples collected from different areas in Gauteng, South Africa. The
adsorption data was assessed using different adsorption isotherms and adsorption kinetics.
The data best fitted Langmuir isotherm and pseudo- second order kinetic models. The good
feature about this adsorbent was that it was not highly affected by the sample matrix and
could be reused up six cycles. It also displayed relatively high adsorption capacities for the...