Colloids and Surfaces A: Physicochem. Eng. Aspects 522 (2017) 105–112 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journa l h om epage: www.elsevier.com/locate/colsurfa Mixed micelle formation of cationic gemini surfactant with anionic bile salt: a PAH solubilization study Sanjay Kumar Yadav a , Kushan Parikh a , Sanjeev Kumar b,∗ a Department of Chemistry, Faculty of Science, Soft Material Research Laboratory, The Maharaja Sayajirao University of Baroda, 390002, Vadodara, India b Department of Applied Chemistry, Faculty of Technology & Engineering, The Maharaja Sayajirao University of Baroda, 390002, Vadodara, India h i g h l i g h t s • CG and bile salt interact synergisti- cally. • Solubility of PAH increases in CG-bile salt mixed solution. • Solubilization capacity is found lower than CG-anionic surfactant. • The study may find applications in biomedical field. • The findings can be used in aquatic recharging of water bodies. g r a p h i c a l a b s t r a c t PAH solubilization in aqueous and mixed CG-bile salt micellar solution. a r t i c l e i n f o Article history: Received 5 January 2017 Received in revised form 18 February 2017 Accepted 20 February 2017 Available online 22 February 2017 Keywords: Bile salt Cationic gemini surfactant Critical micelle concentration Polycyclic aromatic hydrocarbon Molar solubilization ratio a b s t r a c t Aqueous mixed micelle formation between cationic gemini surfactant (butanediyl-1,4-bis (N,N-alkyl ammonium) dibromide, m-4-m; or ethane-1,2-diyl (N,N-dimethyl-N-dodecyl-alkyl ammoniumace- toamide) dichloride, m-Eda-m, where m = 12,14 and 16) and bile salt (sodium cholate, SC or sodium deoxycholate, SDC) has been investigated by conductivity measurements and the critical micelle concen- tration values are compared with individual gemini surfactant or bile salt. Surfactant–bile salt interactions (interaction parameter, ˇ m ) have been compared using theoretical models of Clint, Rubingh and Moto- mura. cmc values, with varying mole fractions of CG or bile salt, were used to obtain composition of binary mixture for PAH solubilization. Solubilization studies of polycyclic aromatic hydrocarbons PAHs, fluorene, anthracene and pyrene, have also been performed spectrophotometrically in aqueous cationic gemini (CG) with or without bile salt (SC or SDC). Individual bile salt nearly failed to solubilize any amount of PAHs. The solubilization potential has been discussed in the light of molar solubilization ratio (MSR) and compared with other similar CG-anionic surfactant systems. This is the first study in which oppo- sitely charged CG-bile salt binary mixtures are used to enhance aqueous solubility of PAHs. The study may find potential use in biomedical applications. © 2017 Elsevier B.V. All rights reserved. ∗ Corresponding author at: Department of Applied Chemistry, Faculty of Technol- ogy & Engineering, The Maharaja Sayajirao University of Baroda, Vadodara 390002, Gujarat, India. E-mail address: drksanjeev@gmail.com (S. Kumar). 1. Introduction Anionic biosurfactants, bile salts, are synthesized from choles- terol in the liver. They work as solubilizers and emulsifiers for various biomolecules (cholesterol, bilirubin, lecithin and hydrophobic vitamins) in gastrointestinal tract [1]. Due to typical chemical structure [2] of bile salts, their solution properties are different from conventional anionic surfactant. The solution prop- http://dx.doi.org/10.1016/j.colsurfa.2017.02.048 0927-7757/© 2017 Elsevier B.V. All rights reserved.