Grantee Research Project Results
2020 Progress Report: Synthesis and Characterization of Fluorinated Hydrocarbon Anion Exchange Resins for the Extraction of Perfluorinated Chemicals
EPA Grant Number: SU839454Title: Synthesis and Characterization of Fluorinated Hydrocarbon Anion Exchange Resins for the Extraction of Perfluorinated Chemicals
Investigators: Danielson, Neil , Berberich, Jason , Almquist, Catherine B , Smith, Abby , Wourms, Hannah , Beckman, Matthew , Kuehl, Emily , Spilker, Robert
Institution:
Current Institution: Miami University - Oxford
EPA Project Officer: Page, Angela
Phase: I
Project Period: December 1, 2018 through November 30, 2019 (Extended to November 30, 2021)
Project Period Covered by this Report: December 1, 2019 through November 30,2020
Project Amount: $14,999
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2018) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
To the best of our knowledge, the application of any completely polymeric mixed mode fluorocarbon substituent/anion exchange material for the adsorption of perfluoroalkyl chemicals (PFCs) has never been reported. We proposed an approach to prepare a pH and pressure stable mixed mode fluorocarbon substituent/anion exchange material for the adsorption of PFCs such as perfluorooctanoic acid (PFOA). Toward this goal, the broad tasks of this research are to: 1) Synthesize and characterize a Kel-F 800/weak anion exchange resin, 2) Compare the adsorption capacity and thermodynamic parameters of the adsorbents for PFOA in the batch mode and the adsorption kinetics of the adsorbents for PFOA in the column breakthrough mode, 3) Investigate how representative co-contaminants and minerals in the water impact adsorption capacity and adsorption kinetics of the PFCs, and 4) Demonstrate that the adsorbents can be regenerated and reused.
Progress Summary:
We have pioneered the use of mixed mode fluorocarbon polymer/aminopropyl silica as column packings for high performance liquid chromatography (HPLC) based on polychlorotrifluoroethylene-vinylidene fluoride co-polymer (Kel-F 800) modified aminopropyl silica. In this work, we have used a controlled particle and pore size polystyrene-divinylbenzene weak anion exchange (PSDVB-WAX) polymer as the basis for a completely new class of fluorocarbon polymer/anion exchange polymer hybrid materials for the adsorption of PFCs such as PFOA. This fluorous affinity between adsorbent and PFCs should provide enhanced selectivity as well as good adsorption capacity. We have shown that the PSDVB-WAX-Kel-F particles can be packed into stainless steel liquid chromatography (LC) columns of 0.4 cm ID and 2 cm in length using simple glass wool plugs as frits. The adsorption performance of these columns has been investigated using standard LC instrument hardware composed of a high pressure pump and a UV-VIS detector with on-line data acquisition software. A solution of PFOA was pumped through the polymer packed column in order to generate a breakthrough curve. Both ion exchange and hydrophobic retention profiles for PFOA are evident on PSDVB-WAX-Kel-F columns based on acetonitrile and perchlorate mobile phases. However, breakthrough of PFOA is shorter on the for the PSDVB-WAX-Kel-F column than the starting PSDVB-WAX polymer due to possible coverage of pores and less accessible anion exchange amines. This set-back was overcome by a second reaction involving polyethyleneimine (PEI) and PSDVB-WAX-Kel-F.
This dual grafted fluorinated hydrocarbon amine weak anion exchange resin polymer (PSDVB-WAX-Kel-F-PEI) synthesized by a two-step amine grafting reaction was optimized with
respect to stoichiometry of PEI to PSDVB-WAX-Kel-F. The success of the syntheses was verified by scanning electron microscopy and the adsorption performance evaluation was conducted by constant flow rate high-performance liquid chromatography (HPLC) fixed-bed column analyses. The results show the breakthrough of the PSDVB-WAX-Kel-F-PEI synthesized by the optimum stoichiometry was two times better than the starting anion exchange polymer PSDB-WAX, and six times better than the powdered activated carbon. The adsorption kinetic parameters of the optimum synthesized sorbent were determined using the Thomas model and the Yoon-Nelson model.The adsorption mechanisms of this novel adsorbent including hydrophobic interaction and electrostatic interaction were also further clarified in this study. Regeneration of the PSDVB-WAX-Kel-F-PEI packed column after PFOA adsorption was possible using a mixture of 10% 0.05 M methanesulfonic acid and 90% acetonitrile solution as the desorption solution to remove the retained PFOA through both ion exchange and hydrophobic forces without damaging the polymer. Based on almost the same time of saturation midpoint, it can be highlighted that the PFOA adsorption efficiency can be maintained for at least five cycles without any reduction. This work has been completed and a manuscript has been written for submission to the Journal of Hazardous Materials.
Our present work is summarized as follows. Poly(ethylene-chlorotrifluoroethylene), also known as Halar, is a fluoropolymer containing chlorine groups with excellent stability. We have shown a feasible reaction approach that can graft polyamines into the chlorotrifluoroethylene part of the co-polymer under moderate reaction conditions. Polyethyleneimine (PEI) was selected as the derivatization amine to synthesize this Halar-PEI product. Column breakthrough studies are being used to evaluate the adsorption performance of this novel Halar-PEI adsorbent.
Future Activities:
We have shown definitely that this dual grafted fluorinated hydrocarbon amine weak anion exchange resin polymer (PSDVB-WAX-Kel-F-PEI) is effective for the adsorption of PFOA from water and has excellent potential for solid phase extraction analytical applications. The Halar-PEI polymer having larger particles should be applicable for larger columns and more preparative water purification applications.
Journal Articles:
No journal articles submitted with this report: View all 5 publications for this projectSupplemental Keywords:
Perfluoroalkyl chemicals (PFCs), perfluorooctanoic acid (PFOA), water treatment, polystyrene-divinylbenzene (PSDVB), weak anion exchange (WAX), Kel-F 800, polyethyleneimine (PEI), Halar, graft polymer, Thomas model.
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.