Breakdown of PFOA in a hydrodynamic cavitation-activated persulfate system: Comparative roles of sulfate and hydroxyl radicals in degradation process and mechanistic insights

• Published in: Journal of environmental chemical engineering 2024-10, Vol.12 (5), p.113376, Article 113376
• Main Authors: Wang, Xu, Wang, Mingran, Yu, Guoqing, Wang, Wenqiang, Liu, Haijun, Chen, Zhongbing, Chen, Huilun
• Format: Article
• Language: English
• Subjects: Degradation mechanism; Hydrodynamic cavitation; Influencing factors; Perfluorooctanoic acid; Persulfate
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.113376

Perfluorooctanoic acid (PFOA) remains a persistent organic pollutant within aquatic ecosystems. Activated persulfate (PS) technology has been widely used because it can effectively destroy the stable structure of PFOA. However, this technology still has some restrictive problems, such as the large amount of PS required for the reaction and the high SO42- concentration in the wastewater after the reaction. In this study, we used the advantages of hydrodynamic cavitation to activate PS, such as promoting mass transfer and oxidant utilization. After 3 hours of treatment, the HC/PS system showed outstanding performance in that 93.6% of PFOA was degraded, and 31.09% of PFOA was defluorinated under optimal conditions with smaller PS dosage and lesser SO42- generation. The different inhibitory effects of coexisting substances (Cl-, CO32-, F-, NO3-, SO42-, HA) on the system were emphasized. The contribution rates of sulfate radicals (SO4•-, 84.4%) and hydroxyl radicals (·OH, 10.9%), which are the main active substances in the HC/PS system, were calculated during the degradation of PFOA. The potential degradation pathways of PFOA were proposed based on the intermediates identified through LC-MS/MS. PFOA gradually lost CF2 units, forming shorter-chain intermediates (PFHpA, PFHxA, PFPeA, PFBA) and F-, ultimately converting to H2O and CO2. Above all, this study provides valuable insights into the future wastewater treatment process for PFOA pollution and has important guiding significance for practical engineering applications. •The HC/PS system can efficiently degrade PFOA (93.6%) at low PS dosage.•Six coexisting substances have different inhibitory effects on the degradation.•Concentration of SO42- from the reaction meets emission standards.•The contributions of ·OH(10.9%) and SO4•-(84.4%) for PFOA removal were determined.•PFOA is degraded into short-chain intermediates by stepwise removal of CF2.