Abstract
Abstract : Water is the most vital substance for all life on earth and a valuable resource for human civilization. Access to clean and affordable water is the most basic goal for human beings and it is a major global challenge especially in developing countries such as South Africa. It is fundamentally important to implement basic water treatment methods in developing countries where water infrastructure is very poor or even of nonexistence. The increasingly stringent water quality standards compounded by emerging contaminants have brought new scrutiny to the existing water treatment and distribution systems widely established in developing countries. Current water purification technologies and infrastructure are now in their demanding stage to provide enough water of highest quality to satisfy human and environmental needs. Common analytical techniques for determination of organic pollutants in water system include high performance liquid chromatography and gas chromatography both coupled with different detectors. However, the analytes are normally incorporated in complex matrices which makes it difficult detected them directly. Therefore, the aim of this study was to develop sample preparation methodologies for preconcentration of selected emerging pollutants in wastewater samples prior chromatographic determination. Firstly, MgO-ZnO@CNFs and Al2O3-Fe3O4@CNFs nanocomposites were both synthesised by simple solution mixing-evaporation method. The structural and morphological properties of the material were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope/energy-dispersive spectroscopy (SEM/EDS), transmission electron microscope (TEM) and Brunauer–Emmett–Teller (BET). Secondly, Fe3O4-Al2O3@CNFs and Al2O3-Fe3O4@CNFs nanocomposites were used as adsorbents in ultrasound assisted dispersive magnetic solid phase microextraction (UA-UADMSPME) and ultrasound assisted dispersive solid phase microextraction (UA-DSPME) methods. These methods were used for preconcentration of 17-beta estradiol (E2) and carbamazepine (CBZ) from wastewater. The analytes of interest were quantified using high performance liquid chromatography with a diode array detector (HPLC-DAD). Several parameters such as pH, mass of adsorbent, extraction time and eluent volume were first screened out by using fractional factorial design approach then further optimised was conducted using by using Box-Behnken and central composite design. Under optimized conditions, the linear dynamic ranges were LOQ-1000 ng mL−1 and LOQ-800 ng mL−1 with correlation coefficients 0.9922-0.9951 for UA-DMSPME and UAv DSPME methods, respectively. For UA-DMSPME/HPLC-DAD procedure (determination of E2), the preconcentration factor (PF), limit of detection (LOD) and limit of quantification (LOQ) were found to be 334, 0.25 μg L−1 and 0.83 μg L−1, respectively. While for UADSPME/ HPLC-DAD method (quantification of CBZ), the PF, LOD and LOQ 490, 0.08 μg L−1 and 0.29 μg L−1, respectively. The developed methods were successfully applied for the determination and quantification of E2 and CBZ in spiked wastewater samples and the recoveries ranged from 97.8-102% respectively. These findings indicated that both methods were efficient in the extraction, preconcetration and quantification of E2 and CBZ from complex matrices
M.Sc. (Chemistry)