Bicontinuous microemulsions as adsorbents for liquid-phase separation/purification

We present novel concepts of liquid-phase adsorption at the oil/water interface of a bicontinuous microemulsive phase. We assess these ideas using a tetradecane/didodecyldimethylammonium bromide/water bicontinuous microemulsion (BME) to adsorb chromate anions from aqueous solution. The adsorption isotherms are investigated as a function of solution ionic strength. Our results show that the BME is an effective adsorbent for removing CrO42- from solutions with good selectivity over Br- and high enrichment ratio, due to large internal surface area of the oil/water interface. An approximate model adsorption isotherm is derived from basic thermodynamic considerations. The proposed model is validated against our experimental data with satisfactory agreement for low chromium content in the BME. Implications of these concepts and results for adsorptive separation of generic contaminant from a liquid phase are discussed in comparison with conventional adsorption processes employing solid adsorbents and also with micellar enhanced ultrafiltration process.