Location: Water Management and Conservation Research
Project Number: 2020-13000-005-021-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2024
End Date: Jan 31, 2026
Objective:
The chief objective is to utilize mechanochemical technique to investigate the destruction of per- and polyfluoroalkyl substances in contaminated soil. We will use brushite/monetite precursor as a milling medium to facilitate mechanochemistry and encapsulate formed fluoride. In our recent work (RSC Mechanochem., 2024, 1, 263-278) we already demonstrated the mechanochemical conversion of monetite/brushite to hydroxyapatite. Hydroxyapatite is a major mineral prevalent in natural environment. Importantly, OH- ions in hydroxyapatite can be substituted with other anions, such as F-, to form stable and environmentally benign mineral, fluoroapatite. Hence the objective is to perform tandem mechanochemical conversion of PFAS while encapsulating the resulting F- moiety in a thermodynamically stable form that can be stored as a mineral.
Approach:
Initially, we will utilize a standard PFAS substance, such as Tridol S3, a commercial C6 AFFF concentrate manufactured by Angus Fire (UK). We will also synthesize monetite/brushite solid precursors using sol/gel methods described in our work (RSC Mechanochem., 2024, 1, 263-278). Mechanochemical experiments will be performed in a dedicated Retsch PM 300 ball mill and two stainless steel jars. PFAS will be pipetted directly onto 25 mg of brushite/monetite precursor and milled for various amounts of time. Each data point will be generated from a discrete trial run. All experimental runs will be conducted under ambient temperature, pressure, and humidity. Analysis of the resulting products will be performed at USDA ARS in Arizona using LC-MS/MS. If mechanochemical reaction will need to be accelerated, we will utilize Liquid Assisted Grinding (LAG) using a strong Lewis base, such as KOH, as a co-milling agent. Once we establish performance metrics and kinetics of PFAS mechanochemical reaction, we will seek from USDA ARS to provide us with contaminated soils for experiments. Ultimately, we will be using a scalable technique routinely used in large scale mineral and fertilizer industry, mechanochemistry, to destruct PFAS while immediately encapsulating it in a solid low solubility mineral form. The results of this research will provide for the large-scale approach to remediation of the PFAS contaminated soils.
