LOW-TEMPERATURE EXPERIMENTAL INVESTIGATION OF THE EFFECT OF HIGH PH NAOH SOLUTIONS ON THE OPALINUS SHALE, SWITZERLAND

Batch reactor experiments were performed at 150-degrees-C, 175-degrees-C, and 200-degrees-C to determine the effect of high pH NaOH solutions on the mineralogy of the Opalinus shale. In these experiments, the change in solution quench pH at 25-degrees-C, solution composition, and mineralogy were monitored as a function of time for up to almost-equal-to 40 days. Runs were performed in 50 ml titanium hydrothermal reactor vessels. Each reactor was charged with 0.5-5.0 g of the 80-200 mesh size fraction of Opalinus shale, and 25 ml of solution (0.1 and 0.01 M NaOH). The general sequence of reaction products observed under these high pH conditions include first the formation of analcime, followed by vermiculite, and finally Na-rectorite formation.