title: Detergency and Its Implications for Oil Emulsion Sieving and Separation.
abstract: Separating petroleum hydrocarbons from water is an important problem to address in order to mitigate the disastrous effects of hydrocarbons on aquatic ecosystems. A rational approach to address the problem of marine oil-water separation is to disperse the oil with the aid of surfactants in order to minimize the formation of large slicks at the water surface and to maximize the oil-water interfacial area. Here we investigate the fundamental wetting and transport behavior of such surfactant-stabilized droplets and the flow conditions necessary to perform sieving and separation of these stabilized emulsions. We show that, for water-soluble surfactants, such droplets are completely repelled by a range of materials (intrinsically underwater superoleophobic) due to the detergency effect; therefore, there is no need for surface micro-/nanotexturing or chemical treatment to repel the oil and prevent fouling of the filter. We then simulate and experimentally investigate the effect of emulsion flow rate on the transport and impact behavior of such droplets on rigid meshes to identify the minimum pore opening (w) necessary to filter a droplet with a given diameter (d) in order to minimize the pressure drop across the mesh-and therefore maximize the filtering efficiency, which is strongly dependent on w. We define a range of flow conditions and droplet sizes where minimum droplet deformation is to be expected and therefore find that the condition of w ≈ d is sufficient for efficient separation. With this new understanding, we demonstrate the use of a commercially available filter-without any additional surface engineering or functionalization-to separate oil droplets (d < 100 μm) from a surfactant-stabilized emulsion with a flux of ∼11,000 L m-2h-1bar-1. We believe these findings can inform the design of future oil separation materials.
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Thomas M
authors.identifier: 0000-0003-3309-3568
authors.initials: TM
authors.lastname: Schutzius
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Christopher
authors.initials: C
authors.lastname: Walker
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Tanmoy
authors.initials: T
authors.lastname: Maitra
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Romy
authors.initials: R
authors.lastname: Schönherr
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Christos
authors.identifier: 0000-0002-8482-1150
authors.initials: C
authors.lastname: Stamatopoulos
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Jung
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Carlo
authors.initials: C
authors.lastname: Antonini
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Hadi
authors.initials: H
authors.lastname: Eghlidi
authors.affiliation: Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland.
authors.forename: Julie L
authors.initials: JL
authors.lastname: Fife
authors.affiliation: Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Patera
authors.affiliation: Laboratory for Multiscale Studies in Building Physics, Swiss Federal Laboratories for Materials Science and Technology-Empa , Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
authors.forename: Dominique
authors.initials: D
authors.lastname: Derome
authors.affiliation: Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich , Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
authors.forename: Dimos
authors.identifier: 0000-0001-5733-6478
authors.initials: D
authors.lastname: Poulikakos