The development and application of imprinted membrane-passive samplers (IMPS) for the monitoring of polychlorinated biphenyls (PCBS) in aquatic systems of South Africa

Abstract: Polychlorinated biphenyls (PCBs) are persistent organic pollutants listed in the Stockholm Convention. Therefore, South Africa as a signatory to this convention has an obligation to undertake appropriate monitoring and research regarding the presence of PCBs in the environment. To this end a passive sampling device for PCBs in water, based on molecularly imprinted membranes (MIMs), was developed and tested. The MIM-based sampler was designed to have high sampling rates and enhanced detection for PCBs, which is crucial as PCBs tend to occur at ultra-trace levels in water. MIMs were prepared from molecularly imprinted polymers (MIPs), with molecular recognition capabilities towards PCBs. The sampler was developed through the synthesis of MIPs, followed by characterisation and comparison to non-imprinted polymers (NIPs) to evaluate the effects of molecular imprinting. The physical properties of the MIPs and NIPs were studied through Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The performance of the MIPs was evaluated through rebinding studies using water spiked with known concentrations of PCBs. Furthermore, selectivity studies using water spiked with known concentrations of PCBs, anthracene and dichlorodiphenyltrichloroethane (p,p’-DDT) were used to evaluate polymer performance. The NIPs had a lower surface area and binding capacity towards PCBs, in comparison to MIPs demonstrating the effectiveness of molecular imprinting. The MIPs had a greater selectivity towards PCBs compared to structurally similar anthracene and DDT. The MIMs were prepared through the phase-inversion technique, characterised through FTIR spectroscopy, cross-sectional, and surface SEM analysis, atomic force microscopy (AFM) to predict fouling behaviour, and contact angle studies to evaluate the hydrophobic properties of the MIMs. In addition, MIM performance was evaluated through PCB enrichment studies using a dead-end filtration cell. As with the MIP, the MIMs showed greater selectivity towards PCBs in comparison to DDT and anthracene. Furthermore, the MIMs possessed good water permeation, which was crucial for water applications. The MIM-based passive samplers were fabricated and loaded with performance reference compounds (PRCs) prior to exposure to known concentrations of PCBs in a continuous-flow simulation tank. The effects of environmental conditions including temperature and water turbulence, on the effects of PCB uptake, were investigated and corrected with PRCs. The...Ph.D. (Chemistry