진학프로석·박사 채용 접수 플랫폼

Missions

Background:

There are few techniques for extracting PFAS (per- and polyfluoroalkylated substances) from soils. Among them, in situ washing involves injecting a solvent (typically water) into the soil, with or without additives (e.g. surfactants or alcohols), to desorb pollutants from the soil and then extracting the washing solution for treatment.

njecting these liquids into heterogeneous porous media is tricky, as the less permeable zones will be less well cleaned due to hydrodynamic instabilities and preferential pathways. To achieve good injection homogeneity in heterogeneous media, surfactants or alcohols can be injected using non-Newtonian shear-thinning liquids, using approaches similar to those used for enhanced oil recovery. 

The viscosity of such fluids decreases with increasing shear rates. Injected liquids will be more viscous in permeable layers and less viscous in less permeable layers. This means they can theoretically sweep the entire porous medium more evenly. Aqueous foam can behave as a shear-thinning fluid and have the advantage of generating fewer fluids effluent than, e.g., polymers.

The postdoctoral research will focus on the development of non-Newtonian liquids, and in particular aqueous foams, to desorb PFAS from soils while generating as little effluent as possible.

Activities

The aim of the postdoctoral research is to develop a method for extracting PFAS from porous media using non-Newtonian liquids, mainly foams. The PFAS studied will be long-chain (more than 6 carbon atoms), short-chain (between 3 and 6 carbon atoms) and ultra short-chain (less than 3 carbon atoms). The postdoctoral research will focus mainly on laboratory experiments. Batch studies will focus on the adsorption and desorption of different PFAS with different soil matrices and water compositions. Different non-Newtonian liquid formulations will be characterized (interfacial tension, viscosity, foamability, etc.). 1D column tests with different porous media will be used to validate the formulations developed (extraction yields, flow/pressure ratio, type of injection). These tests will be validated in 2D tanks. Monitoring will be carried out using TDR probes and image interpretation techniques.