Removal of selenium from water by complexation with polymeric dithiocarbamates
AssigneeNalco Chemical Company
InventorsThomas M. Miller, Walter H. Goodman
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Abstract
Selenium compounds present in aqueous liquids can be removed using a poly dithiocarbamate materials. The selenium compounds are then removed by precipitation or sedimentation. Optionally, an oxidizing agent may be added to the system prior to the addition of the poly dithiocarbamate. Various filtration methods may be employed to remove the selenium-dithiocarbamate materials from aqueous liquids.
Claims25
A method for the removal of soluble selenium compounds from an aqueous liquid containing soluble selenite and selenate compounds which comprises:
- a) adjusting the pH of the aqueous liquid containing the selenium compounds to a value of about 5 or less:
- b) treating the aqueous liquid with a selenate and selenite precipitating amount of a water soluble polydithiocarbamate precipitation aid;
- c) mixing the water soluble polydithiocarbamate precipitation aid with the aqueous liquid to produce a selenium containing precipitate;
- d) removing the selenium precipitate from the aqueous liquid;
- and,
- e) recovering an aqueous liquid having reduced levels of selenium.
A method for the removal of soluble selenium compounds from an aqueous liquid containing soluble selenite and selenate compounds which comprises:
- a) treating the aqueous liquid with an oxidizing agent in an effective amount to oxidize selenium compounds having a -2 valence to +4 or +6;
- b) treating the aqueous liquid, at a pH value of 5.0 or less, with a selenate and selenite precipitating amount of a water soluble polydithiocarbamate precipitation aid;
- c) mixing the water soluble polydithiocarbamate precipitation aid with the aqueous liquid to produce a selenium containing precipitate;
- d) removing the selenium precipitate from the aqueous liquid;
- and,
- e) recovering an aqueous liquid having reduced levels of selenium.
The method of claim 12 wherein the precipitate is removed by filtration.
A method for the removal of soluble selenium compounds from an aqueous liquid containing soluble selenite and selenate compounds which comprises:
- a) adjusting the pH value of the aqueous liquid to be treated to less than about 5.0;
- b) treating the aqueous liquid with a selenate and selenite precipitating amount of a water soluble polydithiocarbamate precipitation aid;
- c) mixing the water soluble polydithiocarbamate precipitation aid with the aqueous liquid to produce a selenium containing precipitate;
- d) filtering the selenium precipitate from the aqueous liquid;
- and,
- e) recovering an aqueous liquid having reduced levels of selenium.
Dependencies are inferred from the claim text.