| Previous investigators have demonstrated in a number of laboratory studies that clays and shales exhibit membrane properties. One membrane process thought to occur in the subsurface is hyperfiltration. Hyperfiltration, also called reverse osmosis, occurs when hydraulic head acts against the osmotic gradient reversing the direction of water flux. However, prediction of hyperfiltration in subsurface materials and relations to clay-rich engineered barriers has been problematic. Therefore, the goal of this research was to develop a transient model capable of describing hyperfiltration effects in natural, membrane-functioning materials. To that end, a set of analytical equations describing transient hyperfiltration was developed and a computer program was written in VISUAL BASIC to implement the transient hyperfiltration model. This model was tested against previously published experimental data and found to satisfactorily reproduce the experimental results. In order to apply the model to natural situations, it is necessary to know what reasonable values of the membrane coefficients are for natural materials. Numerous experiments have determined these coefficients for compacted clays, but very little information exists on the value of these coefficients for shales. To determine reasonable values of these coefficients for use in subsurface modeling, a number of lithosmometer experiments were conducted using thin disks of shales from Chupadero mines in New Mexico and Mancos Shale from Moab, Utah. Several additional experiments were also conducted to test transport of large ionic azo dye molecules through compacted Na-montmorillonite. The lithosmometer experiment yielded shale membrane efficiencies between 41% and 88%. These coefficients appear to be more related to pore size than to mineralogy. The two ionic azo dyes used showed significant variability in their mass transfer coefficients, intrinsic retentions and amount rejected by compacted Na-montmorillonite. X-ray diffractograms of Na-montmorillonite indicated that adsorption of the dyes on the clay surface was more prominent than absorption.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office. |
