Effect of freeze-thaw process on partitioning of contaminants in ferric precipitate.
The primary interest of this work was to determine the processing conditions which will provide the most water removal from the precipitate after freezing and thawing. The work examined the effect of variables such as freezing time, freezing temperature, and pre-treatment steps, e.g. agitation or concentration, on the freeze thaw process of ferric precipitates. The extent of dewatering of freeze thawed samples was not significantly affected by freezing rate or curing time, provided the floc was completely frozen. However, a pre-concentration step was found to produce a more concentrated residual. The relatively low degree of structure within the ferric flocs makes them particularly suitable for freeze-thaw conditioning. Only a slight increase in leach out of contaminant from the floc was observed. Thus, the experiments indicate that this is a very simple and effective method of dewatering precipitates, which does not require the use of additional additives.
McMinn
Wendy A M
WA
School of Chemical Engineering, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, UK. w.mcminn@qub.ac.uk
Keown
James
J
Allen
Stephen J
SJ
Burnett
Michael G
MG
D011232:Chemical Precipitation; D005427:Flocculation; D005615:Freezing; D007501:Iron / Q000737:chemistry*; D013696:Temperature; D014865:Waste Disposal, Fluid; D014867:Water / Q000737:chemistry
D014867:Water; D007501:Iron