Method of extracting metal ions from an aqueous solution utilizing an antimony silicate sorbent
The invention provides a use of a material comprising antimony silicate as a sorbent in the removal of metal ions, e.g. radioactive metal ions, from an acidic liquid medium. The metal ions may be selectively removed from amongst other ions such as Na, K, Mg, and Ca ions. Strontium is particularly effectively removable in this way. There is also provided a method of preparing an antimony silicate material for use in removing metal ions. The invention further provides a material comprising antimony silicate doped with one or more elements selected from the group consisting of tungsten, niobium and tantalum. The doped material has been found to be particularly effective as a sorbent in the removal of metal ions from a liquid medium.
1. A method of extracting metal ions from an aqueous solution comprising contacting the aqueous solution with a material consisting essentially of antimony silicate doped with one or more elements selected from the group consisting of tungsten, niobium and tantalum which material has been obtained by reacting together in a liquid medium a silicon-containing compound, an antimony containing compound and a compound containing one or more of the elements in the presence of an acid.
2. A method according to claim 1 wherein the material has a Si:Sb ratio of less than 5.
3. A method according to claim 1 wherein the one or more elements is present in the material at a concentration in the range from about 0.5 to about 30.0 weight %.
4. A method according to claim 2 wherein the one or more elements is present in the material at a concentration in the range from about 0.5 to about 30.0 weight %.
5. A method according to claim 1 in which the aqueous solution has a pH <7.
6. A method according to claim 1 in which the metal ions are radioactive metal ions.
7. A method according to claim 6 in which the radioactive metal ions comprise Sr, Cs, Co, Pu or Am ions.
8. The process of claim 1 wherein the acid is a polymerization catalyst.
9. The method of claim 1 wherein the material is a crystalline antimony silicate material.
10. The method of claim 6 in which the aqueous solution is acidic and contains at least one background ions Na, K, Mg or Ca ions at a higher concentration than the concentration of the radioactive metal ions.
11. The method of claim 6 in which the aqueous solution is acidic and contains at least one background ion Na, K, Mg, or Ca ions, and in which the radioactive metal ions are selectively removed from the aqueous solution, the background ions being left behind in the aqueous solution.
12. A method of extracting metal ions from an aqueous solution comprising contacting the aqueous solution with a material consisting essentially of antimony silicate doped with one or more elements selected from the group consisting of tungsten, niobium and tantalum.