{"683028":{"#nid":"683028","#data":{"type":"event","title":"PhD Defense by Xiaoyue Xin","body":[{"value":"\u003Cp\u003E\u003Cem\u003EDefense announced 11 days in advance due to Georgia Tech holiday office closure.\u0026nbsp;\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003ESchool of Civil and Environmental Engineering\u003C\/p\u003E\u003Cp\u003EPh.D. Thesis Defense Announcement\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAdvanced Treatment Processes for Destruction of Per- and Polyfluoroalkyl Substances (PFAS) in Water Treatment\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EBy\u003Cstrong\u003E\u0026nbsp;Xiaoyue Xin\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EAdvisor:\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EDr. Ching-Hua Huang\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003ECommittee Members:\u003Cstrong\u003E\u0026nbsp; Dr. Yongsheng Chen (CEE)\u003C\/strong\u003E,\u003Cstrong\u003E\u0026nbsp;Dr. Sotira Yiacoumi (CEE)\u003C\/strong\u003E,\u003Cstrong\u003E\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Dr. Shane Snyder (CEE)\u003C\/strong\u003E,\u003Cstrong\u003E\u0026nbsp;Dr. Daniel Ashley (Spelman College)\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EDate and Time:\u003Cstrong\u003E\u0026nbsp; July, 18, 2025.\u0026nbsp; 9:00 \u2013 11:00 AM EST\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003ELocation:\u0026nbsp;Ford ES\u0026amp;T 3229\u003C\/p\u003E\u003Cp\u003ETeams Meeting ID: 220 473 631 260 7; Passcode: QQ3DW6wK\u003C\/p\u003E\u003Cp\u003EPer- and polyfluoroalkyl substances (PFAS) are a class of persistent anthropogenic\u003Cbr\u003Econtaminants recognized for their widespread environmental occurrence,\u003Cbr\u003Ebioaccumulation, and significant health implications. Their exceptional resistance\u003Cbr\u003Eto conventional water treatment methods underscores the critical need for\u003Cbr\u003Einnovative remediation technologies. Conventional UV lamps, emitting primarily at\u003Cbr\u003E254 nm or higher wavelengths, are useful in advanced water treatment processes;\u003Cbr\u003Ehowever, these lamps present some limitations, including mercury use, limited\u003Cbr\u003Ephoton energy, and low efficiency in generating reactive species for contaminant\u003Cbr\u003Edegradation. This study investigates novel far-UVC irradiation at 222 nm, a mercuryfree,\u003Cbr\u003Ehigher photon energy UV technology with the potential of enhancing reactive\u003Cbr\u003Especies generation and improving contaminant degradation efficiency. This\u003Cbr\u003E\u003Cbr\u003Eresearch comprehensively evaluates the effectiveness of far-UVC 222 nm as an\u003Cbr\u003Eadvanced treatment strategy for PFAS-contaminated waters through direct\u003Cbr\u003Ephotolysis, advanced reduction processes (ARPs), and advanced oxidation\u003Cbr\u003Eprocesses (AOPs).\u003Cbr\u003EFirst, this study investigated the susceptibility of 19 representative PFAS to direct\u003Cbr\u003Ephotolysis and defluorination under far-UVC 222-nm irradiation. Enhanced\u003Cbr\u003Ephotolysis occurred for perfluorocarboxylic acids (PFCAs), fluorotelomer\u003Cbr\u003Eunsaturated carboxylic acids (FTUCAs) and GenX, compared to that at conventional\u003Cbr\u003E254-nm irradiation on a similar fluence basis. In contrast, other PFAS, including\u003Cbr\u003EPFSAs, 6:2 diPAP, 5:3 FTCA, 6:2 FTS, FOSA and FHxSA, showed minimal decay by\u003Cbr\u003Ephotolysis under UV 222 nm irradiation. For degradable PFAS, up to 81% of parent\u003Cbr\u003Ecompound decay (photolysis rate constant (k222-nm) = 8.19-34.76 L\u00b7Einstein-1;\u003Cbr\u003Equantum yield (\uf046222-nm) = 0.031-0.158) and up to 31% of defluorination were\u003Cbr\u003Eachieved within four hours, and the major transformation products were shorterchain\u003Cbr\u003EPFCAs. Solution pH, dissolved oxygen, carbonate, phosphate, chloride and\u003Cbr\u003Ehumic acids had mild impacts, while nitrate significantly affected PFAS\u003Cbr\u003Ephotolysis\/defluorination at 222 nm. Decarboxylation is a crucial step of photolytic\u003Cbr\u003Edecay. The slower degradation of short-chain PFCAs than long-chain ones are\u003Cbr\u003Erelated to molar absorptivity and may also be influenced by chain-length dependent\u003Cbr\u003Estructural factors, such as differences in pKa, conformation, and perfluoroalkyl\u003Cbr\u003Eradical stability. Meanwhile, the possible transformation pathway of PFCAs was\u003Cbr\u003Eexplored using density functional theory (DFT)-based theoretical calculations.\u003Cbr\u003EThese new findings are among the first to demonstrate the capability of 222-nm\u003Cbr\u003Elight to degrade PFAS and provide the basis for further development of far-UVC\u003Cbr\u003Etechnology for PFAS in water treatment.\u003Cbr\u003ESecond, PFAS degradation by integrating far-UVC irradiation at 222 nm with sulfitebased\u003Cbr\u003Eadvanced reduction processes (ARPs) was investigated. The UV-based ARPs\u003Cbr\u003Ehave emerged as an effective strategy to degrade and defluorinate PFAS\u003Cbr\u003Econtaminants in water. However, current studies have mainly focused on UV 254\u003Cbr\u003Enm irradiation, and the feasibility of treating PFAS with UV222\/ARP remains\u003Cbr\u003Eunknown. Comparative analysis on the fundamental photochemical properties of\u003Cbr\u003EUV222\/sulfite systems and conventional UV254\/sulfite systems revealed that 222-\u003Cbr\u003E\u003Cbr\u003Enm irradiation significantly improves the performance by generation of more\u003Cbr\u003Ehydrated electrons (eaq\u003Cbr\u003E-), the primary reactive species driving PFAS degradation, and\u003Cbr\u003Eexhibits superior energy efficiency, characterized by lower electrical energy per\u003Cbr\u003Eorder (EEO). The higher efficiency of UV222\/sulfite can be attributed to stronger light\u003Cbr\u003Eabsorption of sulfite and higher photon energy at 222 nm. Under optimized stepwise\u003Cbr\u003Esulfite dosing conditions, the UV222\/sulfite ARP achieved high perfluorooctyl\u003Cbr\u003Esulfonic acid (PFOS) removal efficiency, nearly 85% reduction in parent compound\u003Cbr\u003Eand 66% defluorination within a six-hour period, while the degradation of shorterchain\u003Cbr\u003EPFHxS and PFBS was slower. Real water matrix components can influence\u003Cbr\u003Etreatment efficiency. The impacts of nitrate\/nitrite were transient that diminished\u003Cbr\u003Eafter rapid photolysis at 222 nm, while dissolved organic matter (DOM) and\u003Cbr\u003Ecarbonates exerted strong reactive species scavenging effects. These findings\u003Cbr\u003Eestablish UV222\/sulfite ARP as a promising strategy to enhance PFAS degradation.\u003Cbr\u003ECareful optimization of system parameters and water matrices will increase the\u003Cbr\u003Eadaptability for PFAS environmental remediation.\u003Cbr\u003EThird, a pilot-scale investigation was conducted to assess the influence of ozonation\u003Cbr\u003E(O3) and ozone\/hydrogen peroxide (O3\/H2O2) advanced oxidation process (AOP),\u003Cbr\u003Erespectively, on the fate of PFAS in a wastewater effluent subjected to reuse. The\u003Cbr\u003Eobjective was to assess the potential of PFAS transformation by AOP under real\u003Cbr\u003Ewater treatment conditions. The study evaluated 40 target PFAS and associated\u003Cbr\u003Eprecursors (based on the total oxidizable precursor (TOP) assay) under various\u003Cbr\u003Etreatment conditions, including different ozone doses (1.0-4.0 mg\u00b7L-1), H2O2 doses\u003Cbr\u003E(0-0.20 mg\u00b7L-1), and contact time (0\u201320 min). Results indicated that short-chain (C3-\u003Cbr\u003EC7) PFAAs dominated in concentrations, while overall PFAA concentrations were\u003Cbr\u003Eelevated by both oxidative treatment processes, particularly after high-dose\u003Cbr\u003Eozonation treatment. TOP assays revealed that there were considerable amounts of\u003Cbr\u003EPFAA precursors in the reuse wastewater and their concentrations were decreased\u003Cbr\u003Eafter the oxidative treatment with increase of some of the PFAAs. This pilot study\u003Cbr\u003Edemonstrated that ozone and ozone-based AOP treatments can have a moderate\u003Cbr\u003Einfluence on the transformation of PFAS and increase of PFAA levels under practical\u003Cbr\u003Econditions.\u003Cbr\u003ELast, based on previous study suggesting the potential of ozone and AOP in the\u003Cbr\u003Etransformation of PFAS precursors into terminal PFAAs, and growing research\u003Cbr\u003E\u003Cbr\u003EA Unit of the University System of Georgia \u2022 An Equal Education and Employment Opportunity Institution\u003Cbr\u003Eevidence supporting the potential of oxidizing PFAA precursors into terminal PFAAs\u003Cbr\u003Ethrough UV\/AOPs, mainly through the facilitation of generation of reactive radical\u003Cbr\u003Especies, PFAS degradation by integrating far-UVC irradiation at 222 nm with\u003Cbr\u003Eperoxydisulfate (PDS)-based AOPs was thus explored. Comparative analysis of\u003Cbr\u003EUV222\/PDS and conventional UV254\/PDS systems revealed that 222-nm irradiation\u003Cbr\u003Esignificantly enhanced the generation of reactive radical species, including hydroxyl\u003Cbr\u003Eand sulfate radicals, thereby accelerating degradation kinetics of PFAS precursors.\u003Cbr\u003ERadical generation was highly influenced by reaction conditions, such as solution\u003Cbr\u003EpH, initial PDS dose, and UV fluence. PFAS precursors including 6:2 FTSA, 6:2 FTCA,\u003Cbr\u003Eand FHxSA showed rapid and complete decay within a short irradiation time. A\u003Cbr\u003Eunique advantage of UV222\/PDS treatment was the capacity for continuous\u003Cbr\u003Edegradation, as PFAS precursors transformed into terminal PFCAs, subsequently\u003Cbr\u003Eundergoing direct photolysis, resulting in chain-shortening and moderate overall\u003Cbr\u003Edefluorination. However, terminal PFAS such as PFOA demonstrated limited\u003Cbr\u003Eenhancement under UV222\/PDS conditions. GenX exhibited moderate\u003Cbr\u003Eimprovement, whereas Perfluoro(2-ethoxyethane)sulfonic acid (PFEESA) remained\u003Cbr\u003Eresistant to degradation by UV222\/PDS. Real water matrices notably reduced\u003Cbr\u003EUV222\/PDS efficiency, slowing PFAS precursor degradation and increasing\u003Cbr\u003Eintermediate byproduct formation. UV222\/PDS systems present significant\u003Cbr\u003Epromises for enhancing remediation of PFAS precursors, although addressing\u003Cbr\u003Elimitations associated with terminal PFAS and complex water matrices remains\u003Cbr\u003Eessential for broad environmental applicability.\u003Cbr\u003EOverall, this study demonstrates the exceptional potential and significant\u003Cbr\u003Eadvantages of far-UVC irradiation at 222 nm for PFAS remediation, presenting\u003Cbr\u003Edetailed mechanistic insights and identifying both strengths and ongoing\u003Cbr\u003Echallenges. The thorough exploration of water matrix effects enhances the practical\u003Cbr\u003Erelevance of these findings, offering valuable guidance for optimizing treatment\u003Cbr\u003Estrategies in real-world applications. This research substantially advances scientific\u003Cbr\u003Eunderstanding and informs the future development of innovative, scalable, and\u003Cbr\u003Esustainable solutions to address global PFAS contamination challenges.\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cstrong\u003EAdvanced Treatment Processes for Destruction of Per- and Polyfluoroalkyl Substances (PFAS) in Water Treatment\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Advanced Treatment Processes for Destruction of Per- and Polyfluoroalkyl Substances (PFAS) in Water Treatment"}],"uid":"27707","created_gmt":"2025-07-07 18:24:36","changed_gmt":"2025-07-07 18:25:13","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2025-07-18T09:00:00-04:00","event_time_end":"2025-07-18T11:00:00-04:00","event_time_end_last":"2025-07-18T11:00:00-04:00","gmt_time_start":"2025-07-18 13:00:00","gmt_time_end":"2025-07-18 15:00:00","gmt_time_end_last":"2025-07-18 15:00:00","rrule":null,"timezone":"America\/New_York"},"location":"Ford ES\u0026T 3229","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}