Decommissioning particle sizing after a freeze-thaw laboratory based simulation of a permeable reactive barrier

Brief description

The impact of freeze-thaw cycling on a ZVI and inert medium was assessed using duplicated Darcy boxes subjected to 42 freeze-thaw cycles. This dataset consists of particle sizing during the decommissioning process of the experiment. Two custom built Perspex Darcy boxes of bed dimensions: length 362 mm, width 60 mm and height 194 mm were filled with a mixture of 5 wt% Peerless iron (Peerless Metal Powders and Abrasive, cast iron aggregate 8-50 US sieve) and 95 wt% glass ballotini ground glass (Potters Industries Inc. 25-40 US sieve). This ratio of media was selected to ensure that most aqueous contaminant measurements were above the analytical limit of quantification (LOQ) for feed solutions at a realistic maximum Antarctic metal contaminant concentration at a realistic field water flow rate. All solutions were pumped into and out of the Darcy boxes using peristaltic pumps and acid washed Masterflex FDA vitron tubing. Dry media was weighed in 1 kg batches and homogenised by shaking and turning end over end in a ziplock bag for 1 minute. To ensure that the media was always saturated, known amounts of Milli-Q water followed by the homogenised media were added to each box in approximately 1 cm layers. 20 mm of space was left at the top of the boxes to allow for frost heave and other particle rearrangement processes. On completion of freeze-thaw cycling and solution flow (refer to Statham 2014), an additional series of assessments was conducted. The media from between the entry weir and the first sample port was removed in five approximately 400 g samples of increasing depth. This procedure was repeated between the last sample port and the exit weir. These samples were left to dry in a fume cabinet before duplicated particle sizing using a Endcotts minor sieve shaker.