Perfluorooctane acid (PFOA) and perfluorooctane sulfonate (PFOS) in the Plankenburg (Stellenbosch) and Diep (Milnerton) Rivers, and potential remediation using vitis vinifera leaf litter
Fagbayigbo, Bamidele Oladapo
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This study represents the first monitoring campaign to assess the seasonal trend of nine perfluorinated compounds (PFCs) in surface water and sediment from the Plankenburg and Diep Rivers in the Western Cape, South Africa. An analytical protocol was developed and validated for qualitative and quantitative routine determination of nine perfluorinated compounds (PFCs), in water and sediment samples using Ultra performance liquid chromatography-mass spectrometry quadrupole time of flight (UPLC-QTOF-MS). This method was applied to determine levels of PFOA and PFOS in environmental samples. Samples were collected along the Diep (Milnerton) and Plankenburg (Stellenbosch) Rivers respectively. Samples were pre-treated, cleaned-up and extracted using solid-phase extraction (SPE) procedures with hydrophilic-lipophilic balance (HLB) C-18 cartridges. Seasonal variation and distribution of PFCs in surface water and sediment was also investigated. Levels of PFCs were monitored in four seasons (summer, autumn, winter and spring) to establish their trend in the environment. The removal of PFOA and PFOS from aqueous solutions using agro-waste biomass of Vitis vinifera (grape) leaf litter was also studied. Activated carbons were produced from the biomass and chemical activation achieved with phosphoric acid (H3PO4) and potassium hydroxide (KOH) for the modification of the carbons’ (AC-H3PO4 and AC-KOH respectively). Activated carbons were characterized using Fourier Transform infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Brunauer- Emmett-Teller (BET) in order to understand the removal mechanisms of the contaminants by activated carbons. The effects of solution concentration, pH, adsorbent dosage, contact time, and the temperature were optimized for evaluation of the removal efficiency of the activated carbons. Adsorption isotherm models were used to analyze the equilibrium data obtained and kinetic models were applied to study sorption mechanisms. A fixed bed column study was conducted using: AC-H3PO4 adsorbent. Experimental parameters such as initial concentration of the solution, column bed height, flow rate and initial concentrations of the influent were optimized to establish the best adsorption efficiency parameters of the column system. Breakthrough curve and exhaustion time were predicted using Adam-Bohart, Yoon-Nelson, and Thomas models for the fixed bed column under varying experimental conditions.