Grantee Research Project Results
Final Report: Novel Remediation Technique for PFAS contaminated Soil and Sediment
EPA Contract Number: 68HE0D18C0027Title: Novel Remediation Technique for PFAS contaminated Soil and Sediment
Investigators: Nayak, Subhadarshi
Small Business: QMetry Corporation
EPA Contact: Richards, April
Phase: I
Project Period: October 1, 2018 through March 31, 2019
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2018) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Land Revitalization
Description:
PFAS or poly- and per-fluoroalkyl substances are man-made chemicals that have been used in industry and consumer products worldwide since the 1950s. PFASs, such as perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), are mobile, persistent, and bio-accumulative, and are toxic emerging contaminants. Besides direct handling of these materials, exposure may also occur by using products or materials that contain PFAS. Studies led by Center for Disease Control and Prevention (CDC) revealed that some PFAS may affect growth and development, reproduction, thyroid function, the immune system, and injure the liver in animals. These chemicals do not degrade in the environment, and people and wildlife are likely exposed by consuming PFAS-contaminated water or food for years to come. Soil and sediment contaminated with these persistent organic pollutants (POPs) are likely to find their ways to ground water via leaching or storm water run-off. These POPs can also enter the food chain by uptake by crops grown in these lands or by livestock foraging.
Most of the current approaches to remediate PFAS contaminated soil and sediment are based on separation of PFAS-contaminated media from the environment. Specialized materials such as activated carbon, clay and other materials with favorable surface related properties are used to adsorb PFASs from soil, sediment and water and then treated or stored separately. Few methods that rely on transformation of PFAS, in which these pollutants are transformed to simple harmless molecules such as H2O, CO2 and HF, includes incineration and sono-chemical treatment. These methods are expensive, limited in efficacy and scalability, and energy- or labor-intensive. Hence, there is a strong need for an affordable, practical, and scalable remediation method.
QMetry Corporation was awarded a Phase I EPA SBIR project to study the feasibility of a novel remediation method for PFAS-contaminated soil and sediment. QMetry has demonstrated the feasibility of a novel cement-carbon composite electrodes for electrochemically oxidize and destroy per- and polyfluoroalkyl substances (PFAS) present in the soil and sediment, thus, amend the polluted soil and sediment. Functionalized graphite, activated carbon, modified clay, cement, and electro-oxidation catalysts are used to make a composite carbon-cement electrode. The innovative electrode was designed and built for actualizing a three-prong approach for PFAS transformation and mineralization. The proprietary electrode design aimed to achieve these three goals.
1.Mechanical mixing of an contaminated environmental medium (soil, slurry, sediment, water, effluent, or wastewater) improve diffusion or transport of PFAS molecules.
2.The ultra-high surface area associated with a hierarchical network of micro-, meso- and macro-pores improves adsorption of organic compounds. The composite with hydrophilic phases enhanced electrochemical contact with the media, whereas the hydrophobic sites provided sites for adsorbing the CF2tails of PFAS. Additionally, proprietary constituents preferentially adsored the PFAS molecules either by interacting with the headgroups or the CF2 tails.
3.Electro catalysts incorporated in the composite electrode A pulse electrical current is applied through the medium using the carbon-cement-composite electrode as cathode and a graphite electrodes as anode. Electrical energy pulses trigger electrochemical oxidation of the PFAS selectively adsorbed on the composite electrode. The pulsed energization and abrasion due to the mixing action renewed the electrode surface, thus, inhibited anode passivation and cathodic scaling.
Summary/Accomplishments (Outputs/Outcomes):
In the Phase I feasibility study, the team used a bench-top set-up of electrode and carried our experiments using PFOS and PFOA-spiked soil and established the following findings:
1. The modified carbon, cement, and other minor constituents could be cast into a concrete electrode with adequate strength that can be used to mix soil and sediment.
2. The concrete composite was of high porosity (41%�53%) with micro-, meso- and macro-pores.
3. Modified carbon phases with minor addition of metal oxides improved conductance of the composite for adequate electrical performance (~ 1000 S/m).
4. The composite exhibited both hydrophilic and hydrophobic sites.
5. The time to equilibrate, as the metric for quantifying diffusion-based transport of PFAS, indicates that moderate mixing improved diffusion substantially (at least 2 order of magnitude in environmentally relevant concentration of PFOS and PFOA.
6. The electrode material exhibited high selective adsorption of PFOS and PFOA as seen in experiment with soil samples high (6.1%) as well as low (<1.0%) total organic carbon (TOC).
7. Electrochemical reaction transformed PFOS and PFOA into simple, smaller molecules in about 53 hours to threshold of detection. The initial concentration from nearly100 ng/kg to end of treatment concentration of about 5ng/kg.
8. Incorporation of electro-catalyst enhanced the reaction rate substantially (18-23 hours).
Conclusions:
The highly porous electrode selectively adsorbs and destroys the PFAS by an electrochemical advanced oxidation process (EAOP). The large surface area of the porous electrodes accelerates the adsorption and oxidation reaction rate as it reduces the distance for the rate limiting mass transfer. Functionalized phases in the composite selectively (or preferentially) adsorb PFAS molecule. This selectivity can be further enhanced by addition of functionalized carbon customized to interact with the headgroups or the CF2 tails of PFAS. Additionally, the pulsed energization will inhibit anode passivation and cathodic scaling. The electrode can be implemented in common farm or construction machines by casting the concrete mixture onto the tines of a tiller/cultivator or cutterhead teeth of a dredger. The concrete casted tines or cutterhead energized by pulse electrical current act as electrodes with alternate polarity for electrochemical reaction while simultaneously mixing the soil, slurry, or sediment. The innovative composite surface is continually renewed via abrasion, thus, prevent passivation and fouling a common issue in EAOP. The composite electrode is environmentally benign and disposable. The remediation method can be carried out in situ without extensive material, energy input, or capital investment.
Commercialization:
We will design and build a functional prototype for remediation of an contaminated site using a farm equipment. The prototype demonstration will establish economic feasibility of the innovation. Based on market research and input provided by Foresight, QMetry will partner with an industry leader in environmental remediation. Additionally, we also have developed a marketing plan for Department of Defense (DoD) contracts for remediation of aqueous film forming foam (AFFF)-affected sites following Foresight's recommendation. The negotiation is underway for formally initiating partnership. The partnership will include the development phase, demonstration of the prototype, and data collection to meet regulatory specification. QMetry will then license the technology to the marketing partner for commercial applications. The team may supply the functionalized ingredients for carbon-cement composite electrodes. We will supply these products through contract manufacturing (ball milling). Some of the steps can be carried out according to our proprietary recipes in-house. The team will also contract manufacture the tine/cutter-head electrodes for the pilot projects or for long-term sale to marketing partner. QMetry will hire a well-known commercialization specialist with successful career in DoD contracting and 35+ years of experience as C-level executive in technology firms. The hiring will be funded by third-party investment currently under negotiation and expected to materialize in August 2019. Additionally, the investment will also help fund legal fees for executing partnership agreement, intellectual property protection, technology development for market readiness including pre-production and production prototype development, test and demonstration.
The 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.