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      Permanent link:
      https://www.ias.ac.in/article/fulltext/jcsc/120/06/0637-0643

    • Keywords

       

      Wetting control; porous substrate wetting; porous silica film; surfactant mediated wetting; oil-water contact angle.

    • Abstract

       

      Selective permeation of oil and water across a porous medium, as in oil recovery operations, depends on the preferential wetting properties of the porous medium. We show a profound influence of surfactants in wetting of porous media and thus demonstrate a new route for the control of water-in-oil wetting of porous substrates by changing the concentration of surfactants in an aqueous sub-phase below the substrate. This strategy is employed to engineer partial reversible wetting transitions on a porous silica film. The film itself is grown and stabilized on a flat, macroscopic interface between an oil phase and an aqueous sub-phase. On increasing the surfactant (CTAB) concentration in the sub-phase, contact angle of a water drop (placed on the oil side of the film) changes from 140° to 16° in 25 min by diffusion of the surfactant across the porous film. On further replacement of the sub-phase with pure water, diffusion of the surfactant from the water drop back to the sub-phase was slower, increasing the contact angle in the process from 16° to 90° in 2 h. Wettability control by a cationic surfactant (CTAB) was found to be much faster (6 deg/min) than that offered by an anionic surfactant, SDS (0.05 deg/min). Switching of the surface wettability due to the surfactant diffusion may have implications in oil-water separation, chemical bed reactors and microfluidic devices.

    • Author Affiliations

       

      Manish M Kulkarni1 Rajdip Bandyopadhyaya2 Ashutosh Sharma1

      1. Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016
      2. Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076
    • Dates

       
  • Journal of Chemical Sciences | News

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