Adsorption and advanced oxidation/reduction process for elimination of per- and polyfluoroalkyl substances and pharmaceutical pollutants in water

Emerging contaminants, such as pharmaceuticals and personal care products (PPCPs) and per- and polyfluoroalkyl substances (PFAS), have attracted increasing concern due to their widespread contamination and harmful effect on the ecosystem. Furthermore, some PFAS are recognized as persistent organic pollutants and their production is regulated. Nevertheless, various PPCPs and PFAS have been globally detected in surface water, groundwater, and wastewater in recent decades. Moreover, conventional water and wastewater treatment plants have shown limited efficiencies in removing these contaminants. Therefore, it is necessary to develop cost-effective methods to achieve the elimination of PPCPs and PFAS from water.
This thesis work developed a cobalt-doped, carbon-based catalyst for PPCP degradation by an advanced oxidation process. Ibuprofen (IBU) was chosen as the target PPCP. The catalyst prepared at the highest temperature (850 °C) efficiently degraded 100% IBU (C0 = 10 mg/L) within 60 min. Co-existing ions such as PO43- (10 mM), NO3- (10 mM), and HCO3- (2 mM) showed little impact on IBU degradation, whereas Cl- (2-10 mM) significantly inhibited it. SO4·-, ·OH, and O2·− radicals contributed to the efficient degradation of IBU.
A combined sorption/desorption approach coupled with the UV/sulfite degradation method proved to be successful in the elimination of five PFAS. Twelve degradation intermediates of perfluorooctanoic acid (PFOA) were confirmed. A novel biosorbent (PG-PB) was developed with excellent adsorption capacity for PFOA, namely 456.0 mg/g at pH 3.3 and 258.0 mg/g at pH 7 (C0 = 200 mg/L). The spent PG-PB was efficiently regenerated by 0.05% NaOH + 20% methanol, and the final PFOA degradation and defluorination efficiency in the desorption effluents reached 100% and 83.1% in 24 h. In addition, a commercial anion exchange resin, Purolite A860, was highly efficient for the sorption of five individual PFAS from water. The 0.025% NaOH, 5% NaCl, and 5% NH4Cl solution were effective desorption solutions for most PFAS. Although desorption of perfluorooctanesulfonic acid (PFOS) was challenging, the desorption of PFOS in 5% NaCl solution in a high-speed stirring system was attained. Direct treatment of the desorption effluents by UV/sulfite achieved 97.6-100% degradation and 46.6-86.1% defluorination in 24 h.