Nuclear magnetic resonance studies of multiphase systems : application to remediation processes

• Main Author: Baldwin, C. A.
• Published: University of Cambridge 1996
• Subjects: 577.27
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596301

Nuclear Magnetic Resonance (NMR) imaging has been applied to multiphase systems in order to gain insight into both the usefulness of NMR as a quantitative tool and the mass-transfer processes which govern the rate of removal of nonaqueous phase liquid (NAPL) contaminants from groundwater. A new approach to chemically resolved imaging is proposed. It is shown that by acquiring an image of a system with two different gradients, a system composed of two overlapping peaks can be resolved by employing a deconvolution algorithm based upon CLEAN. This method provides better chemical resolution for systems of overlapping peaks than standard chemical select methods, without the need of resorting to chemical shift imaging. Further extension of NMR imaging has been made through the introduction of a segmentation algorithm for the analysis of three-dimensional images. This method provides an unambiguous partitioning of the void space and may be used to obtain information about the geometry and topology of the system. The application of NMR to specific questions in the field of NAPL research has provided new and useful findings. One-dimensional NMR has been used to obtain saturation profiles during the course of dissolution of NAPL. The results were compared to six different models appearing in the literature. It was found that a conceptual model, the pore diffusion model, provided the best agreement with experimental data. However, none of the models were accurate enough to be predictive. The size and shape of NAPL ganglia are studied during the course of dissolution for the first time via three-dimensional imaging of a model NAPL system.