Microplastics are an emerging chemical of concern due to their widespread occurrence in the environment, recalcitrant properties, and potential adverse effects. To add to their complexity, co-occurring chemicals such as per and poly-fluoroalkyl substances (PFAS) may interact with microplastics, altering their transport and distribution in the environment. The objective of this proof-of-concept project is to determine if a novel process utilizing colloidal gas aphrons (also known as "aphrons") can effectively and efficiently remove microplastics and PFAS from water. Aphrons represent a unique foam-like microstructure, where each individual entity consists of a core of gas encapsulated within a water layer and further surrounded by three concentric layers of surfactants. Aphrons have three key underlying advantages that make them a compelling research target to address treatment: (1) several publications show promising results for the removal of microplastics from water using aphrons; (2) ESTCP is currently funding an aphron technology demonstration for PFAS removal (ER23-7892), and (3) potential for rapid commercialization due to existing large-scale water treatment units designed for suspended solids removal from source waters.

This project will perform a combination of laboratory experiments to: 1) understand the mechanisms of microplastics and PFAS removal by gas aphrons and 2) use this knowledge to optimize the design of the gas aphron technology to remove both microplastics and PFAS from water. The experiments are designed to address key questions including:

• Which surfactants produce the best aphrons for removing microplastics and PFAS?
• Do aphrons remove microplastics by an electrostatic attraction mechanism?
• Can aphrons effectively remove both microplastics and PFAS from water?
• Will the addition of metal- or polymer-based coagulants improve the microplastic removal efficiency aphrons?

The experimental research conducted in the project will support the advancement of a novel gas aphron technology that has the potential to remove both microplastics and PFAS from impacted waters. If successful, the aphron system will provide a cost-effective alternative to rapidly treat surface water and groundwater, as well as other aqueous waste streams. (Anticipated Project Completion - 2027)