Solubilization potentials of single and mixed oppositely charged gemini surfactants: A case of polycyclic aromatic hydrocarbons

Abstract

Solubilization studies of polycyclic aromatic hydrocarbons (PAHs), fluorene, anthracene and pyrene, have been performed spectrophotometrically in aqueous cationic surfactant (conventional and gemini) with or without an anionic gemini surfactant, AG (phosphoric acid, P,P′-1,4-butanediyl P,P′-didodecyl ester, disodium salt). Cationic surfactants (both conventional and gemini) used in the study are: alkyltrimethylammonium bromide (CnTAB, n=12,14 and 16), butanediyl-1,4-bis (N,N-alkyl ammonium) dibromide (m-4-m, m=12,14 and 16) and ethane-1,2-diyl (N,N-dimethyl-N-dodecyl-alkyl ammoniumacetoamide) dichloride (m-Eda-m, m=12,14 and 16). Conductometric measurements have also been performed to determine critical micelle concentration (cmc) values of various conventional and oppositely charged gemini combinations. Surfactant–surfactant interactions (interaction parameter, βm) have been compared using theoretical models of Clint, Rubingh and Motomura. cmc values with varying mole fraction were used to determine composition of binary mixture, corresponding to minimum cmc (cmcm), for PAH solubilization. The solubilization potential has been discussed in the light of molar solubilization ratio (MSR) and various ordering are suggested for conventional, gemini and binary mixture. AG and 16-4-16/16-Eda-16 show minimum and maximum MSR when present individually in the solution. However, AG+16-4-16/16-Eda-1616-4-16/16-Eda-16 combinations shown best solubilization potential among all the binary mixture studied. It has been shown that above combinations, in general, are better performing for all the PAHs solubilization (this is not true for other binary mixtures reported till date). Probably, this is the first report in which oppositely charged gemini surfactants are used in binary mixtures to exploit their solubilization potential.