PhD Student in Chemical and Environmental Engineering
University of California, Riverside
Zekun Liu is currently the 3rd year PhD student in Chemical and Environmental Engineering Department in the University of California, Riverside. His research mainly focuses on understanding the PFAS structural reactivity relationships and the development of PFAS degradation technologies, with the goal to cleave all C-F bonds from PFAS molecules.
Near-Quantitative Defluorination of Perfluorinated and Fluorotelomer Carboxylates and Sulfonates with Integrated Oxidation and Reduction
The UV/Sulfite reductive process is a promising defluorination technology for perfluorocarboxylates (PFCAs, CnF2n+1COO–) through hydrated electrons (eaq–). However, due to the C–H bonds formed in degradation products, the residual C–F bonds strengthed and consequently prevented complete defluorination. Reductive treatment of fluorotelomer carboxylates (FTCAs, CnF2n+1–CH2CH2–COO–) and sulfonates (FTSAs, CnF2n+1–CH2CH2–SO3–) are also sluggish because the ethylene linker separates the fluoroalkyl chain from the end functional groups. In this work, we used oxidation with hydroxyl radicals (HO•) to convert FTCAs and FTSAs to a mixture of PFCAs. This process also cleaved 35–95% of C–F bonds. For the generated PFCAs mixture, the subsequent UV/Sulfite treatment achieved deep defluorination up to 90%. The following use of HO• to oxidize the H-rich residues cleaved remaining C–F bonds. The results will fill major knowledge gaps in the mechanistic understanding and advance remediation technologies to achieve thorough PFAS destruction.