Microstructural changes in bentonite caused by selected organic solvents

Previous research has shown that clays permeated with concentrated organic liquids undergo increases in conductivity up to several orders of magnitude compared to that of water. The objective of this study was to explain such increases in conductivity in terms of mineralogical and microstructural changes of bulk clay.; Bentonite was exposed to aniline and xylene through batch experiments for varying time periods. Compacted sand-bentonite samples were exposed to these solvents either through laboratory conductivity testing or by immersing in the liquid. Mineralogy and microstructure of the samples before and after such treatments were studied using x-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy, and/or mercury intrusion porosimetry.; Analyses performed on aniline-(batch)treated-bentonite suggest that there is no change in crystal structure of bentonite as evidenced by infrared analysis. However immediate exposure of bentonite to aniline results in the adsorption of aniline; with time aniline desorbs and the bentonite returns to its original state. It can be concluded that instantaneous adsorption of aniline results in flocculation of bentonite and eventual desorption of aniline reduces the degree of flocculation.; Tests performed on compacted sand-bentonite samples permeated with aniline indicate that the clay mineral itself is not affected by the exposure to aniline except for adsorption. The amount of bentonite in the composite specimen controls the pore size distribution of the sample. A higher fraction of clay in a soil mass results in a greater proportion of fine pores ({dollar}<{dollar}50 {dollar}mu{dollar}m), which in turn results in an increased resistance to flow thus reducing the conductivity of the soil to aniline. Therefore the controlling factor for the conductivity of a clay-sand mixture to aniline appears to be the pore structure of the soil.; Results with xylene need to be interpreted with caution because of the difficulties with this chemical due to its high volatility and low dielectric constant. Tests indicate that the mineralogy of bentonite is not altered by xylene exposure, other than an increase in adsorption with time; this may result in an increase in flocculation with time leading to an increase in conductivity.