Removal of selenium from refinery wastewater
AssigneeNalco Company
InventorsDaniel E. Schwarz, Jitendra T. Shah
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Abstract
The invention provides a method of efficiently removing selenium from water. The method involves: adding an oxidant to the liquid, adjusting the liquid's pH to below 7.5, adding ferric salt in an amount such that less than a quarter of selenium in the liquid precipitates and adding a poly dithiocarbamate material to the liquid in an amount such that the amount of poly dithiocarbamate material (in ppm) is greater than the amount of ferric salt (in ppm). This method removes far more selenium than previous methods, and does it using a smaller amount of expensive chemicals. Moreover this method makes it far more likely to achieve cost effective compliance with the ever-increasing environmental standards for selenium in water.
Claims10
A method of removing selenium from a liquid comprising the steps of:
- adding an oxidant to the liquid,
- adding a sulfur bearing coagulant to the liquid,
- adjusting the liquid's pH to between 5-7,
- adding ferric salt in an amount such that less than a quarter of selenium in the liquid precipitates,
- adding a poly dithiocarbamate material comprising dithiocarbamate functional groups to the liquid in an amount such that the amount of dithiocarbamate functional groups (in ppm) is greater than the amount of ferric salt (in ppm)
- forming a selenium containing floc particle in which the majority of the selenium is in the form of HSeO3−, and
- separating the floc particle from the liquid with a solid-liquid separation method.
A method of removing seliunium from a liquid comprising the steps of:
- adding an oxidant to the liquid,
- adjusting the liquid's pH to below 7.5,
- adding ferric salt in an amount such that less than a quarter of selenium in the liquid precipitates, and
- adding a DTC material to the liquid in an amount such that the amount of DTC material (in ppm) is greater than the amount of ferric salt (in ppm).
Dependencies are inferred from the claim text.