Surfactant controlled switching of water-in-oil wetting behaviour of porous silica films grown at oil-water interfaces

Journal of Chemical Sciences

Manish M Kulkarni²  Rajdip Bandyopadhyaya2¹  Ashutosh Sharma1² 

[1] Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076$$;Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016$$

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

DOI  :  

来源: Indian Academy of Sciences

【 摘 要 】

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.

【 授权许可】

Unknown