Complete Reductive Defluorination of Per- and Polyfluoroalkyl Substances (PFASs) by Hydrated Electrons Generated from 3-Indole-acetic-acid in Chitosan-Modified Montmorillonite

Hailiang Dong | Miami University

ER18-1526

Objective

This project will develop a low cost, environmentally friendly "green chemistry" approach, e.g., using chitosan-montmorillonite nano-composite, for effectively degrading poly- and perfluoroalkyl substances (PFASs) in investigation-derived waste (IDW). Specifically, the research team will determine:

  1. The maximum sorption capacity of 3-indole-acetic-acid (IAA), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) to chitosan-modified montmorillonite.
  2. The rates and pathways of PFOA and PFOS degradation by hydrated electrons generated from IAA that is intercalated in the chitosan-montmorillonite structure.
  3. The impacts of potential of hydrogen (pH), dissolved oxygen (DO), and water chemistry (nitrate, sulfate, bicarbonate; benzene, toluene, ethylbenzene, and xylene [BTEX]; and natural organic matter) on PFOA/PFOS degradation.
  4. The degradation of perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs) in the presence of a broad range of PFASs in IDW.

By the end of this project, the research team aims to develop a novel capability where it can be easily deployed to dispose of, discharge, or reuse IDW.

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Technical Approach

This research will test the hypothesis that a chitosan-modified montmorillonite nano-composite is an effective material for sorbing high concentrations of IAA and PFASs. Upon ultraviolet irradiation, hydrated electrons generated from IAA will not recombine with indole radical cations, which, along with the spatial proximity with sorbed PFASs, will completely defluorinate PFASs. The research team further hypothesize that this treatment technology is expected to operate over a large range of pH and DO condition and in the presence of natural organic matter (NOM), co-contaminants, and competing anions, due to spatial configuration of hydrated electrons, PFASs, co-contaminants, and competing anions within the structure of the chitosan-modified montmorillonite nano-composite. These hypotheses will be tested by performing three tasks: 1) synthesis of a chitosan-modified montmorillonite nano-composite and sorption experiments of IAA, PFOA and PFOS to the nano-composite; 2) experiments of PFOA and PFOS degradation by hydrated electrons generated from IAA that is intercalated into the structure of the nano-composite to determine the rate and pathway; the impacts of water chemistry (NOM, BTEX, nitrate, sulfate, and bicarbonate) on PFAS degradation; (3) degradation experiments of PFCAs and PFSAs in the presence of a wide range of PFASs under realistic environmental conditions to assess the feasibility of this novel approach for treating concentrated IDW.

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Benefits

This novel technology is expected to provide the DoD with a proven technical basis for developing a cost-effective, mobile or temporary treatment system for treating concentrated PFASs in IDW. Because chitosan-montmorillonite nano-composite is environmentally friendly, ease-to-deploy, and effective in completely defluorinating PFASs, this treatment approach may be far more attractive than current treatment methods and allows DoD to directly dispose of, discharge, or reuse IDW. (Anticipated Completion - February 2019)

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Points of Contact

Principal Investigator

Hailiang Dong

Miami University

Phone: 513-529-2517

Program Manager

Environmental Restoration

SERDP and ESTCP

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