Universal Janus Filters for the Rapid Separation of Oil from Emulsions Stabilized by Ionic or Nonionic Surfactants

Abstract

Existing Janus filters cannot separate oil from emulsions stabilized by nonionic surfactants. Reported herein are universal Janus filters that separate oil from emulsions stabilized by not only ionic but also nonionic surfactants. To prepare such a filter, poly(dimethyl siloxane) (PDMS) is grafted onto one side of a fabric. The other side is then grafted with a copolymer polysoap bearing pendant oligo(ethylene glycol) monolaurate (EL) chains. Upon contact with an emulsion, the grafted polysoap competes with free surfactants, ionic or nonionic, for adsorption onto the emulsified droplets, drawing them to the surfaces of the fabric fibers, and causes them to coalesce locally. The coalesced oil then migrates to the PDMS‐coated side of the fabric and selectively permeates it. These novel filters possess enhanced versatility and showcase a new application for polysoaps.

On-Demand Oil–Water Separation by Environmentally Responsive Cotton Fabrics

“…The combination of the SEM image and energy-dispersive X-ray spectroscopy (EDS) analysis is a powerful technique for determining the surface composition and composition distribution. 34 Figure 4c,d shows the SEM−EDS images of P3@CF. The yellow dots representing the Si element (Figure 4c), which is belonged to the PDMS block, are uniformly distributed on the surface of the fabric.…”

“…Noting that the mixed polymer brushes with alternative distribution differ from recently reported V-shape structures. 17,34,35,44 In air, the hydrophobic PDMS block is distributed outside the fabric surface, so the surface initially exhibits hydrophobicity and lipophilicity, as shown in Figure 4e. Hexane soaks into functionalized cotton fabrics rapidly, and the water contact angle (CA) is 120°.…”

“…33 They further improved the coating procedure with designed block copolymers and demonstrated the use of these janus membranes for rapid separation of oil from various surfactant-stabilized O/W emulsions. 34,35 Most studies used simple oil−water mixtures to demonstrate the separation efficiency, which is quite different from actual oil spills and industrial wastewater. 8 The challenge of continuously separating heavy oil−water−light oil ternary mixtures still exists, which is common in actual oil spill cases.…”

Recyclable, Fire-Resistant, Superhydrophobic, and Magnetic Paper Based on Ultralong Hydroxyapatite Nanowires for Continuous Oil/Water Separation and Oil Collection

“…10−15 Superhydrophobic/superoleophilic surfaces can be fabricated by the appropriate surface chemistry and multiscale surface roughness. 16 Various methods have been developed for modifying the substrates including cotton fabrics, 17,18 metal meshes, 19,20 sponges and foam, 21,22 filter paper, 23 and nanofibrous membranes. 24,25 By regulating the wettability difference of the surface toward water and oil, high separation efficiencies of superhydrophobic or superoleophilic materials can be prepared.…”

Co-solvent induced self-roughness superhydrophobic coatings with self-healing property for versatile oil-water separation

“…In the past decades, superhydrophobic surface with static contact angle (CA) larger than 150º and the dynamic slide angle (SA) smaller than 10º has drawn enormous attention due to its potential application in multifarious fields such as oil-water separation, [1][2][3][4][5] self-cleaning, [6][7][8][9] liquid drag-reduction, [10][11][12][13] anti-icing, [14][15][16][17] and so on. [18][19][20][21][22][23][24][25] There is an inherent demand for creating surface roughness to achieve the superhydrophobic state, however, the created surface morphology was often easily damaged during use, leading to the loss of the superhydrophobic state and the functionality.…”