Test were performed in vertical flow columns to determine the
release of Hg from the monolith samples when in contact with a
leaching agent (Milli-Q water, pH: 5.60, conductivity 0.09 lS/cm)
filtering through the sample (flow rate: 43 ml/h). A monolith of
each of the encapsulated materials was placed in a PVC column
(height 20 cm, width 8 cm) (Fig. 3). Water was made to flow in
an ascending fashion through the column using an EYELA MP-3
peristaltic pump. The leachates were collected as several fractions
and the total Hg content determined. The pH and conductivity of
the leachate at the column outlet were measured using a Crison
PH25 pH meter (accuracy 0.01 units) and a Crison 525 conductance
meter (accuracy 0.1 lS/cm) respectively. Control samples prepared
with 90 wt% sulfur and 10 wt% STX (Fig. 1) were subjected to the
same tests under the same conditions. All tests were performed
in duplicate.