Process using rare earths to remove oxyanions from aqueous streams
Oxyanions of various contaminant elements, such as chromium, antimony, molybdenum, tungsten, vanadium and uranium, are removed from water and other aqueous feeds by treating the feed with (1) a sorbent comprising one or more rare earth compounds, usually mixed or supported on particulate solids having a cation exchange capacity less than 20 milliequivalents per 100 grams or (2) an aqueous solution of one or more soluble rare earth compounds.
1. A process for removing oxyanions of an element having an atomic number selected from the group consisting of 5, 13, 14, 22 to 25, 31, 32, 40 to 42, 44, 45, 49 to 52, 72 to 75, 77, 78, 82, 83 and 92 from an aqueous feed containing one or more of said oxyanions, which process comprises contacting said aqueous feed with a sorbent comprising one or more rare earth compounds to remove one or more of said oxyanions from said feed and thereby produce an aqueous fluid having a reduced concentration of said oxyanions as compared to said feed, wherein said rare earth compound or compounds are not supported on particulate solids having a cation exchange capacity for said rare earth compound or compounds greater than 20 milliequivalents per 100 grams.
2. The process defined by claim 1 wherein said sorbent comprises a lanthanum compound.
3. The process defined by claim 1 wherein said sorbent comprises a cerium compound.
4. The process defined by claim 1 wherein said sorbent comprises a mixture of rare earth compounds.
5. The process defined by claim 4 wherein said mixture of rare earth compounds comprises a lanthanum compound and a cerium compound.
6. The process defined by claim 4 wherein said mixture of rare earth compounds comprises a praseodymium compound and a cerium compound.
7. The process defined by claim 1 wherein said feed contains one or more oxyanions of elements selected from the group consisting of bismuth, vanadium, chromium, manganese, molybdenum, antimony, tungsten, lead, hafnium and uranium.
8. The process defined by claim 7 wherein said feed contains one or more oxyanions selected from the group consisting of CrO 4 −2 , Cr 2 O 7 −2 , WO 4 −2 , MO 4 −2 , SbO 3 −1 , MnO 4 −2 UO 4 −2 , and VO 4 −3 .
9. The process defined by claim 3 wherein said cerium compound comprises cerium dioxide.
10. The process defined by claim 1 wherein said sorbent consist essentially of a rare earth compound or a mixture of rare earth compounds.
11. The process defined by claim 7 wherein said sorbent comprises one or more rare earth compounds supported on particulate solids having a cation exchange capacity less than 20 milliequivalents per 100 grams.
12. The process defined by claim 7 wherein said sorbent comprises one or more rare earth compound mixed with particulate solids having a cation exchange capacity less than 20 milliequivalents per 100 grams.
13. The process defined by claim 11 wherein said particulate solids having a cation exchange capacity less than 20 milliequivalents per 100 grams are selected from the group consisting of alumina, diatomaceous earth, porous polymeric materials, refractory oxides and non-oxide refractories.
14. The process defined by claim 12 wherein said particulate solids having a cation exchange capacity less than 20 milliequivalents per 100 grams are selected from the group consisting of alumina, diatomaceous earth, porous polymeric materials, refractory oxides and non-oxide refractories.
15. The process defined by claim 11 wherein said particulate solids have essentially no cation exchange capacity.
16. The process defined by claim 12 wherein said particulate solids have essentially no cation exchange capacity.
17. The process defined by claim 7 wherein said sorbent comprises cerium dioxide mixed or supported on alumina or diatomaceous earth.
18. The process defined by claim 7 wherein said sorbent comprises lanthanum oxide mixed or supported on alumina or diatomaceous earth.
19. The process defined by claim 7 wherein said aqueous feed is selected from the group consisting of groundwater, surface water, drinking water, industrial wastewater, agricultural water, lake water, river water, wetlands water and geothermal water.
20. The process defined by claim 2 wherein said feed contains one or more oxyanions of elements selected from the group consisting of chromium, molybdenum, vanadium, uranium, tungsten and antimony.
21. The process defined by claim 3 wherein said feed contains one or more oxyanions of elements selected from the group consisting of chromium, molybdenum, vanadium, uranium, tungsten and antimony.
22. The process defined by claim 7 wherein said feed contains one or more oxyanions of elements selected from the group consisting of bismuth, vanadium, chromium, manganese, molybdenum, tungsten, lead, hafnium and uranium.
23. A process for removing oxyanions of an element selected from the group consisting of bismuth, manganese, molybdenum, antimony, lead, uranium, and hafnium from an aqueous feed containing one or more of said oxyanions, which process comprises contacting said aqueous feed with a sorbent comprising one or more rare earth compounds to remove one or more of said oxyanions from said feed and thereby produce an aqueous fluid having a reduced concentration of said oxyanions as compared to said feed.
24. The process defined by claim 23 wherein said aqueous feed contains one or more oxyanions of elements selected from the group consisting of molybdenum, uranium and antimony and said sorbent comprises cerium dioxide.
25. The process defined by claim 23 wherein said aqueous feed contains one or more oxyanions of elements selected from the group consisting of molybdenum, uranium and antimony and said sorbent comprises lanthanum oxide.
26. The process defined by claim 23 wherein said aqueous feed contains one or more oxyanions of elements selected from the group consisting of bismuth, manganese, molybdenum, antimony, uranium, and hafnium.
27. The process defined by claim 26 wherein said aqueous feed contains one or more oxyanions of elements selected from the group consisting of manganese, molybdenum, uranium and hafnium.
28. A process for removing oxyanions of an element having an atomic number selected from the group consisting of 5, 13, 14, 22 to 25, 31, 32, 40 to 42, 44, 45, 49 to 52, 72 to 75, 77, 78, 82, 83 and 92 from an aqueous feed containing one or more of said oxyanions, which process comprises contacting said aqueous feed with an aqueous solution of one or more soluble rare earth compounds to precipitate one or more of said oxyanions from said feed and thereby produce an aqueous fluid having a reduced concentration of said oxyanions as compared to said feed.
29. The process defined by claim 28 wherein said aqueous solution contains one or more rare earth compounds selected from the group consisting of rare earth chlorides, rare earth nitrates, rare earth ammonium nitrates and rare earth sulfates.
30. The process defined by claim 29 wherein said rare earth compounds or compounds are selected from the group consisting of cerium compounds and lanthanum compounds.
31. The process defined by claim 28 wherein said feed contains one or more oxyanions of elements selected from the group consisting bismuth, vanadium, chromium, manganese, molybdenum, antimony, tungsten, lead, hafnium and uranium.
32. A process for removing oxyanions of an element having an atomic number selected from the group consisting of 5, 13, 14, 22 to 25, 31, 32, 40 to 42, 44, 45, 49 to 52, 72 to 75, 77, 78, 82, 83 and 92 from an aqueous feed containing one or more of said oxyanions, which process comprises contacting said aqueous feed with a sorbent comprising one or more rare earth compounds to remove one or more of said oxyanions from said feed and thereby produce an aqueous fluid having a reduced concentration of said oxyanions as compared to said feed.
33. A device for removing oxyanions from drinking water comprising:
(a) an inlet communicating with a source of said drinking water;
(b) a vessel containing a sorbent comprising one or more rare earth compounds supported on or mixed with particulate solids having a cation exchange capacity less than 20 milliequivalents per 100 grams, wherein said vessel has an entry portion and an exit portion and said entry portion communicates with said inlet; and
(c) an outlet communicating with said exit portion of said vessel.