Preparation, Characterization and Rheological Behavior of Glutathione-Chitosan Conjugates in Aqueous Media

Glutathione-chitosan conjugates are adequate carriers for anticancer treatment due to their ability for inhibition of efflux pumps, improved mucoadhesivity and in-situ gelling. These conjugates were obtained via carbodiimide at different reaction times in order to get different thiolation degrees (i.e., 4.4!, 5.1! and 7.0!) and their behavior in aqueous media at a pH of 4, 5 and 6 was assessed by measurements of hydrodynamic diameter, zeta potential and rheological analyses at a pH ranging from 4 to 6. Data examination was conducted by principal component analysis (PCA) which in turn explained 73.1! of data variability. All samples showed a Newtonian flow and thiolation rendered materials with a highly pronounced temperature-dependent behavior and a gel-like structure. In turn, the phase shift angle was the most prominent rheological change especially at a pH of 5.0 and 6.0 due to the formation of disulfide bonds. The thiolation degree was the most influential factor and it was inversely related to particle charge and consistency index.

Experimental study on friction loss of W/O emulsion in pipelines and its reduction methods.

In the turbulence of ocean wave, spilled oil takes sea water as small droplets dispersed in it, which is referred to as W/O emulsion. The resultant W/O emulsion has very high viscosity and changes its rheological behavior to cause various difficulties encountered in oil spill response fields such as clogging of pipe line due to too much friction. We conducted experimental researches focusing on friction loss of high viscosity W/O emulsion in pipe line flow. Our research covers the following topics:(1)The rheological change of W/O emulsion and its effect on friction loss of the pipe line flow.(2)Friction loss reduction methods. (1)As for the rheological change, we tried to propose a formulation which gives the friction loss of the W/O emulsion in the pipe line flow. Assumption of the W/O emulsion as pseudo-plastic fluid lead us to a new friction loss prediction formulation which well agrees to the experimental data. (2)As for the friction loss reduction methods, two methods, which are water injection and surfactant injection, were experimentally tested and evaluated. In the water injection study, transport experiments using high viscosity emulsion of real C-heavy oil were carried out in three types of pipe at various flow rates. Pressure drop was measured and correlated with the water injection ratio. A new formulation providing the pressure drop was proposed based on an assumption that the oil and water system forms CAF (Core Annular Flow). The formulation, which is not qualitative but quantitative expression, has shown good agreement with the experimental measurements and also indicates that the best water injection ratio exists for the pressure loss reduction. In the surfactant injection study, we measured friction loss reduction effect in various cases of chemical agents and pipe diameters. The chemical agents, diethylhexyl sodium sulfosuccinate, sorbian laurate were tested as well as some dispersant products. We found that very small amount of surfactant injection can promotes the emulsion breaking inside the pipe and provides drastic reduction of the friction between the emulsion and the pipe wall. The water injection method and the surfactant injection method were applied to the practical use in oil recovery vessels in Japan.