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 nearly equal 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.