Grantee Research Project Results
2020 Progress Report: The BOHP/UV Process for Destruction of PFAS in Leachate and Groundwater: Tandem mechanistic advancement and pilot demonstration
EPA Grant Number: R839630Title: The BOHP/UV Process for Destruction of PFAS in Leachate and Groundwater: Tandem mechanistic advancement and pilot demonstration
Investigators: Cates, Ezra L
Institution: Clemson University
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2019 through July 31, 2022 (Extended to July 31, 2023)
Project Period Covered by this Report: August 1, 2019 through July 31,2020
Project Amount: $458,469
RFA: Practical Methods to Analyze and Treat Emerging Contaminants (PFAS) in Solid Waste, Landfills, Wastewater/Leachates, Soils, and Groundwater to Protect Human Health and the Environment (2018) RFA Text | Recipients Lists
Research Category: Human Health , Water Quality , Drinking Water , Water , PFAS Treatment
Objective:
to the destruction of poly-/perfluoroalkyl substances (PFAS) present in landfill leachate. The original objectives of the 3-year project are to (1) assess degradation kinetics of leachate-relevant poly/perfluorocarboxylic acids (PFCAs) by Bi3O(OH)(PO4)2/ultraviolet process (BOHP/UV) using catalyst particles prepared in the PI’s lab; (2) test hypothesized process modification for photocatalytic mineralization of perfluorosulfonates; and (3) conduct trials of leachate treatment in an integrated BOHP/UV reactor with ceramic ultrafiltration pretreatment (Purifics Photo-cat). The schedule of tasks as originally proposed for the first year of work is shown below for reference.
Progress Summary:
Catalyst synthesis using our establish methods has been achieved without complication. Additional hydrothermal reaction vessels were procured and gram-quantity synthesis of BOHP powder is achievable as needed. Quality of batches has been confirmed via PFOA degradation tests for reference. Analysis of long and short-chain PFCA degradation by the BOHP/UV process indicated that degradation was chain-length dependent, and activity of BOHP toward C5-C7 compounds was poor compared to long-chain PFCAs. This finding was attributed to poor adsorption and interaction between the photoexcited BOHP particles and the target PFAS contaminants.
An original task was aimed at assessing degradation kinetics of PFOA by BOHP/UV within a commercial Purifics Photo-cat system and using waters containing 100 mg-DOC/L of volatile fatty acids (VFAs). The task has been excluded from our revised plan (outlined below) following results of Photo-cat experiments which determined that PFAS degradation in the Photo-cat system is attributed primarily to vacuum-UV (VUV) induced photolysis, and not BOHP photocatalysis. Through additional experimentation, it was determined that the commercial system is unable to adequately take advantage of efficient BOHP photocatalysis due to its excessive UV intensity and narrow lamp-to-wall distance of the annular reactors. Our revised plan thus includes development of a new stirred-tank reactor design and utilizing the newly optimized novel pilot reactor for leachate treatment studies.
In pursuant of methods for degradation of highly recalcitrant perfluorosulfonic acids present in certain groundwaters and landfill leachate, a novel photocatalytic reduction method was evaluated for PFOS destruction. Ultraviolet irradiation of BiPO4 particles in an oxygen-free solution of PFOS in methanol resulted in PFOS disappearance (methanol served as the electron donor). Liberation of F– and SO42– was also observed, and generation of PFCA intermediates, confirming degradation of the PFOS target. The stability of the BiPO4 catalyst proved to be short-lived due to electron injection into surface oxygen vacancies which affected the semiconductor electronic properties photocatalytic degradation of PFOS is notable as it has not been previously achieved, and this system will be studied further herein.
Future Activities:
Based on results from year 1, the projective objectives have been revised to include the following:
1. Assessment of impacts of leachate matrix co-constituents on BOHP/UV degradation of PFOA.
2. Comparison of DOC reduction rates by BOHP/UV and TiO2/UV.
3. Leachate Treatment Pilot Testing in Optimized Stirred-Tank Photocatalytic Reactors.
4. Advancement of BiPO4/UV reductive photocatalysis for PFOS degradation.
Journal Articles:
No journal articles submitted with this report: View all 9 publications for this projectSupplemental Keywords:
hazardous waste remediation; water purification technologies; photocatalytic reduction, groundwater remediation; photocatalyst water disinfectionRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.