Solubilization capabilities of mixtures of cationic Gemini surfactant with conventional cationic, nonionic and anionic surfactants towards polycyclic aromatic hydrocarbons

Solubilization capabilities of equimolar mixed micellar solutions of Gemini surfactant, C 16H 33N +(CH 3) 2 (CH 2) 5 N +(CH 3) 2 C 16H 33 2Br − (G) with cetylpyridinium chloride (CPC), sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and Brij56 towards polycyclic aromatic hydrocarbons (PAHs), viz pyrene and anthracene are studied spectophotometerically at 25 °C and then compared. The results showed that irrespective of the surfactant type, the solubility of PAHs increases linearly with increasing surfactant concentration, as a consequence of association between the PAH and micelles. Solubilization capacity has been quantified in terms of molar solubilization ratio (MSR), micelle-water partition coefficient ( K m), ratio of binding constant ( K 1) between the micelle and PAH to the aggregation number ( N) of surfactant solution and free energy of solubilization ( Δ G s 0 ) of PAHs. Equimolar binary surfactant mixtures showed higher solubilization capacity than their respective individual surfactants except G-CPC wherein the values were intermediate between the two. The mixed micellization parameters viz interaction parameter, β, micellar mole fraction within the mixed micelle, X i , and activity coefficients, f i, were evaluated using Rubingh approach. The values of X i were then employed to evaluate solubilization efficiency of mixed micelles using Regular solution approach (RSA). In addition experimental micelle-water partition coefficients of hydrocarbons have been compared with those predicted theoretically by geometric mean equation for mixed Gemini-conventional surfactant systems. Such mixed systems promise to improve the performance of surfactant enhanced remediation of soils and sediments by decreasing the applied surfactant level and thus remediation cost.