Abstract
M.Sc. (Nanoscience)
Trace elements analysis is globally of interest owing to their influence on the quality of
water systems which affects both aquatic and terrestrial organisms. Most, if not all trace
element exist naturally within the water systems at low concentrations, however,
anthropogenic activities such as industrial, mining and agricultural activities elevates these
concentrations which compromise the safety and cleanliness of drinking water. Most of the
industries, mines and agricultural farms and lands are located outside the central business
district areas towards rural based settlement areas. Thus, the discharges of wastes from
industrial, mining and agricultural processes affects mostly people staying in the rural
areas since most of these areas lack municipal water and people living in and around these
areas depend on river, stream and dam water for survival. This study therefore examines
the effects and impacts of some industries located in the outskirts of rural areas around
Thohoyandou town in terms of the concentration and speciation of selected trace elements
in river water.
In this study, the nanometer-sized ferrous-ferric oxide magnetic nanocomposite
(Fe3O4@MnO2@Al2O3@Au) was successfully synthesized using co-precipitation and sol
gel methods. The structural, morphological and magnetic properties of the nanocomposite
material were characterized by Fourier transform infrared spectroscopy (FTIR), Nitrogen
adsorption-Brunauer Emmett Teller (BET), X-ray diffraction spectroscopy (XRD),
Scanning electron microscopy/Energy dispersive x-ray spectroscopy (SEM/EDS),
Transmission electron microscopy (TEM), Vibrating sample magnetometer (VSM) and
Zeta-potential measurements. The results from TEM and XRD confirm the rhombohedral
shape of the nanocomposite with an average particle size of 15 nm and 17 nm,
respectively. The SEM results show a variety of shapes of the nanocomposite; however,
rhombohedral shaped particles were more dominant. EDS confirms the formation of a pure
Fe3O4@MnO2@Al2O3@Au nanocomposite with no impurities. The FTIR also supported
the formation of the nanocomposite structure. The nanocomposite was applied as a sorbent
for preconcentration of As via ultrasound assisted magnetic solid phase extraction (UAMSPE).
The preconcentrated arsenic was quantified using ICP-MS. A 25-1 fractional
factorial design was used as a tool for optimizing the developed analytical methodologies.
Under optimized conditions, the limit of detection and quantification were 8.6 and 28.5 ng
L-1, respectively. The precision of the developed UA-MSPE method estimated in terms of...