In order to test the effectiveness of complexing agents for in-depth cross-linking and mobility control in polymer and waterfloods, we investigated the transport of aluminum citrate solutions in sandstone and limestone cores. The study was prompted by experimental observations indicating that crosslinking attempts cause plugging of the inlet end of core sections unless special precautions were observed. The plugging was caused by poor transport of the aluminum citrate solutions, which, in turn, was caused by precipitation of aluminum hydroxide in limestone cores, and of both aluminum and ferric hydroxide in sandstone cores. The formation of these precipitates, and the poor transport of the aluminum citrate solution was confirmed experimentally and modeled quantitatively by a geochemical flow simulator. We then used the flow simulator to design injected solutions that would avoid precipitation, generally by raising the injected pH and by using a larger citrate to aluminum ratio. By using these solutions the precipitation could be avoided, and the aluminum citrate could be transported in an unretarded fashion. Polymer cross-linking treatments using solutions designed to eliminate precipitation generally showed more uniform mobility reduction, and an absence of the plugging observed in the first set of flow experiments.

Due to its properties such as biocompatibility, water solubility and stability, polyvinylpyrrolidone (PVP) becomes more and more attractive for biomedical applications. This polymeric material is used in various applications such as pharmaceutical aid, complexing agent or solubilizer. PVP nanofibers are often produced using PVP solutions in solvents with high toxicity such as dimethylformamide (DMF). The aim of this study is to investigate the effect of process parameters on the electrospinning behavior of polyvinylpyrrolidone in solvents with lower toxicity such as dimethylsulfoxide (DMSO) or ethanol. Therefore, solutions of PVP in ethanol, PVP in DMSO or PVP in binary solvent systems such as DMSO/ethanol or DMSO/acetone were prepared and electrospun. The effect of process parameters such as voltage, flow rate, tip-to-collector distance were examined. A solution parameter, the polymer concentration was also considered. The morphology and diameter of the electrospun nanofibers were characterized by scanning electron microscopy (SEM). The effect of the solution viscosity was also questioned. Nanofibers with a homogeneous cylindrical morphology were obtained in the case of PVP in ethanol solutions for a polymer concentration of 7 wt.%. The process parameters were: a voltage of 15kV, tip-tocollector distance of 15 cm and a flow rate of 1.25 mL/h. PVP in DMSO solutions didn't allow the obtention of solid nanofibers on the collector where a wetness zone appears. This shows that the solvent could not evaporate quickly. A wetness was also observed with PVP solutions prepared using binary solvent systems where a more volatile solvent such as ethanol or acetone was used.