| In the present study, the plugging effect of a number of biopolymers, namely xanthan, polyhydroxybutyrate (PHB), guar gum, polyglutamic acid (PGA), and chitosan, has been investigated in a laboratory pressurized pumping flow system. The present work is also targeted to study the correlation, if any, between biopolymer structure and plugging effect. The best plugging effect was obtained for PHB, which can reach more than a billion-fold permeability reduction, followed by chitosan and PGA with a million-fold reduction of permeability. Our results show that the plugging effect is influenced by the structure of biopolymers. Lead stabilization in Ottawa sand, glass spheres and firing range soil were also investigated. This was done in order to find the ability of different cross-linked biopolymers to plug different types of porous medium such that to stop leaching of lead and to form impervious barriers and therefore to stop pollution. It was found, in this study, that guar gum solution plus borax as cross-linking agent was the best system to stabilize lead in firing range soil as well as in sand, and it has the earliest time for 0% leaching out.; It was demonstrated that the two main transition temperatures, i.e., the glass-rubber transition temperature (Tg) and the crystalline melting temperature (Tm) of biopolymers can be correlated with their chemical structure by means of the van Krevelen's method based on additive group-contributions. It was shown that PHB had the lowest Tg and Tm and xanthan had the highest Tg and T m.; Another objective of this research is to develop a numerical model of the in situ gelation process based on McCool's filtration hypothesis. The simulated data of this study were also in close agreement with experimental data, obtained in this study, for the case of xanthan/chromium(III) system in sandpack, natural soil, silt and firing range soil. The linear displacement model, i.e. this study, gave similar results as the radial displacement model of Todd et al. The linear displacement model was chosen over the radial model because the linear model is simple, having less equations, and it takes much less computing time. |
