Sunil S. Bhagwat

Equilibrium and Dynamic Surface Tension Behavior of Triblock Copolymer PEO-PPO-PEO in Aqueous Medium

Equilibrium surface tension of water-soluble triblock copolymer PEO-PPO-PEO (Pluronics) has been measured to determine critical micelle concentration (CMC). The equilibrium surface tension data have been fitted with Langmuir adsorption isotherm. Dynamic surface tension (DST) of the polymer solutions has been measured at below and above the CMC. Results have been compared with the data of a typical nonionic surfactant C12E9. Significant difference in behavior of DST has been observed, with the P123 showing very slow relaxation below the CMC. Above CMC, DST data of P123 show a long induction period. However, relaxation time has been found to be comparable to C12E9. Ward and Tordai model with Langmuir adsorption isotherm has been used to fit the DST data of P123. Similarly C12E9 data from the literature have been fitted with Ward and Tordai model. A reasonably good fit has been obtained for C12E9, although the long-time data deviate from the model. The model has been found to be inadequate for the triblock copolymer that has been attributed to the change in configuration of the polymer at the surface after adsorption. GRAPHICAL ABSTRACT

Effect of polar head surfactants on the demulsification of crude oil

ABSTRACT Surfactants can act as demulsifiers to neutralize the stabilizing effect of natural emulsifiers in crude oil. Here, the effect of polar head group of surfactants with identical hydrophobic chain C12 (SLES, SLS, C12E23, BKC, C12E7) on the demulsification of crude oil emulsion and its effect on water separation rate were studied at different temperature. The activation energy for destabilization was calculated. The results indicate that the rate of water separation increases with temperature and surfactant concentration. The emulsion destabilising activation energy decreases as the concentration of the surfactant increases. The Interfacial Tension (IFT) study showed that when the reduction in IFT was the highest, the water separation rate and efficiency achieved was the highest.

Effect of salinity on the IFT between aqueous surfactant solution and crude oil

ABSTRACT The effect of salts and different surfactants on the equilibrium as well as dynamic interfacial tension (DIFT) between crude oil and water was investigated. Three different types of surfactants with identical hydrophobic chain length C12: Sodium Lauryl Ether Sulphate (SLES), Dodecyl Trimethyl Ammonium Bromide (DTAB), Polyoxyethylene (23) lauryl ether (C12E23) were used in this study. SLES shows better synergism of salt and surfactant mixture amongst the surfactants studied. The order of synergism of salts with the surfactant observed was MgCl2>CaCl2> NaCl. The results obtained from partition coefficient study show that the addition of salts favours the partition of surfactants into the oil phase hence reduce IFT more effectively. DIFT results reveal that, salt accelerates the surfactant migration towards the interface, hence, reducing the t* value.