Selenium removal process
View Patent ↗A process for removing selenium from an aqueous stream using a supported sulfur material, to convert selenocyanate to selenite, followed by removal of the selenite from the aqueous stream.
1. A process comprising:
a) contacting a feed stream comprising water and selenocyanate with a composition consisting essentially of sulfur and a porous support, wherein said porous support is selected from the group consisting of alumina, carbon and combinations thereof, in the presence of at least about 6 ppm oxygen, for conversion of at least a portion of said selenocyanate to selenite, thereby forming an intermediate stream; and
b) contacting said intermediate stream with a selenite removal system, thereby forming a treated stream comprising less selenium than said feed stream.
2. The process of claim 1 wherein said feed stream comprises at least about 8.5 ppm oxygen when contacted with said composition.
3. The process of claim 1 wherein said porous support is carbon.
4. The process of claim 1 wherein said selenite removal system is selected from the group consisting of copper coprecipitation of said selenite, iron coprecipitation of said selenite, and combinations thereof.
5. The process of claim 1 wherein said selenite removal system comprises iron coprecipitation of said selenite.
6. The process of claim 1 wherein said feed stream is contacted with a sufficient quantity of said composition such that at least about 70 wt. % of said selenocyanate is converted to selenite.
7. The process of claim 1 wherein said feed stream is contacted with a sufficient quantity of said composition such that at least about 80 wt. % of said selenocyanate is converted to selenite.
8. The process of claim 1 wherein said intermediate stream is contacted with a sufficient quantity of said selenite removal system such that said treated stream contains less than or equal to about 30 wt. % of the selenium contained in the feed stream, on an elemental selenium basis.
9. The process of claim 1 wherein said intermediate stream is contacted with a sufficient quantity of said selenite removal system such that said treated stream contains less than or equal to about 5 wt. % of the selenium contained in the feed stream, on an elemental selenium basis.
10. The process of claim 1 wherein the concentration of sulfur of said composition is in the range of from about 10 to about 60 wt. % sulfur.
11. The process of claim 1 wherein the concentration of sulfur of said composition is in the range of from about 10 to about 30 wt. % sulfur.
12. The process of claim 1 wherein said contacting in steps a) and b) is at a temperature in the range of from about 20° C. to about 100° C.
13. The process of claim 1 wherein said contacting in steps a) and b) is at a temperature in the range of from about 30° C. to about 80° C.