Rare earth compositions and structures for removing phosphates from water

1 . A rare-earth compound selected from the group consisting of rare earth anhydrous oxycarbonate and rare earth hydrated oxycarbonate, with a surface area of at least 10 m 2 /g, suitable for the removal of phosphate from water.

2 . A rare-earth compound selected from the group consisting of rare earth anhydrous oxycarbonate and rare earth hydrated oxycarbonate, manufactured as agglomerates of 1 to 1000 μm in size, suitable for the removal of phosphate from water.

3 . The compound of claim 1 or 2 , where the rare earth is selected from the group consisting of lanthanum, cerium and yttrium.

4 . The compound of claim 1 or 2 , where the rare earth is lanthanum.

5 . The compound of claim 1 or 2 , where the compound is a particle with a porous structure.

6 . The compound of claim 5 , where the porous structure is made by total evaporation of a rare-earth salt solution, followed by calcination.

7 . The compound of claim 6 , where the total evaporation step is conducted in a spray dryer.

8 . The compound of claim 6 , where the evaporation temperature is between about 120° and 500° C.

9 . The compound of claim 6 , where the calcination temperature is between about 400° and about 1200° C.

10 . The compound of claim 6 , where the porous particles have a size between 1 and 1000 μm.

11 . The compound of claim 10 , where the particles are formed from individual crystals having a size between 20 nm and 10 μm.

12 . The compound of claim 7 , where the product is made of spheres or parts of spheres.

13 . The compound of claim 6 wherein the rare earth salt solution is a rare earth acetate.

14 . The compound of claim 6 wherein the rare earth salt solution is neutralized with sodium carbonate, followed by washing, filtering and drying.

15 . The compound of claim 14 wherein the neutralization process takes place at a temperature between 30° and 90° C.

16 . The compound of claim 15 wherein the drying takes place at a temperature of about 100° to 120° C.

17 . The compound of claim 16 wherein the drying takes place for a period of about 1 to 5 h.

18 . A method of preventing algal growth in swimming pools and other water systems comprising providing an effective amount of the compound of claim 1 or 2 .

19 . The method of claim 17 wherein the compound exhibits a low solubility in water.

20 . The method of claim 17 wherein the compound is added in the filtration system of a swimming pool.