Enhancement of Solubilization (PAHs/Water) & Rheological Behavior at the Interfaces (Air, Oil/Water) in Presence of Surfactants & Additives

Abstract

Solubilization of two immiscible phases can be achieved with the help of additives such as surfactants as it has wide range of applications in many industries. In order to have better solubilization the rheological behaviour of additive added interface plays a critical role. In this thesis solubilization of naphthalene, a double ringed PAH and anthracene, a triple ringed PAH, in the micellar solution of cationic surfactant CTAB has been studied in order to remove PAHs from contaminated soil and ground water. Effect of three electrolytes NaCl, Na2So4 and CaCl2 on the solubilization of naphthalene and anthracene as additives in the presence of cationic surfactant CTAB is also examined. Different physicochemical properties such as critical micelle concentration (CMC), molar solubilization ratio (MSR) and partition coefficient (Km) have been estimated for the cationic surfactant and cationic surfactant with different electrolyte solutions. The cationic surfactant system showed a synergetic behaviour and a maximum synergism was observed for the cationic surfactant in the presence of higher valence counter ion electrolyte. The synergism of CTAB with electrolyte is also confirmed by 1D 1H NMR study. The rheology at air/water and oil/water interface has been presented using cationic single chain surfactant CTAB, double chain cationic surfactant DDAB, non-ionic surfactant IGEPAL CO-630, anionic surfactant SDBS and TiO2 nanoparticle of size 21 nm. In addition to these rheology studies for surfactant mixture of DDAB & IGEPAL CO 630, CTAB in presence of NaCl and mixture of SDBS with TiO2 has been studied extensively at air/water and oil/water interfaces. Additives like electrolyte and nanoparticle are used in order to reduce the consumption of costly surfactant as well as to reduce their environmental impact. Synergism was observed for all the mixed system but SDBS with TiO2 nanoparticle showed more stable oil/water interface by reducing the viscosity and linear viscoelastic parameters at the interface.