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1. WO2009003709 - PREPARATION OF NEW HYDROTALCITE-LIKE ADSORBENTS USEFUL FOR THE ADSORPTION OF ANIONIC MATERIALS

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[ EN ]

C LA I M S

1. Method for the synthesis of an adsorbent suitable for the adsorption of anions, comprising at least the following steps :

a) extracting a clay with mineral acid and separating the liguid extract phase thereby providing an acid extract containing at least 6,5 g/1 aluminium ions and at least 4,5 g/1 iron ions;

b) adjusting the magnesium concentration of the acid
extract by adding a magnesium source to the acid
extract until a magnesium concentration of at least
6.8 g/1 is obtained;

c) adjusting the pH of the acid extract to at least pH = 7 by adding an aqueous alkaline solution thereby obtaining a neutralized extract;

d) after adjustment of the pH to at least pH = 7, adding a carbonate source to the neutralized extract
thereby obtaining a carbonated extract;

e) separating a precipitate from the carbonated extract formed during addition of the aqueous alkaline solution and the carbonate source to the acid extract;

f) drying and optionally milling the precipitate;

wherein no calcination is performed on the precipitate.

2. Method according to claim 1, wherein the aqueous alkaline solution is added under high shear.

3. Method according to one of the preceding claims, wherein the carbonate source is added as an aqueous solution.

4. Method according to claim 3, wherein the concentration of the aqueous carbonate source solution is selected within a range of 10 to 25 wt.-%.

5. Method according to any of the preceding claims, wherein the liquid extract phase provided as the aluminium source is adjusted to a temperature in a range of 50 to 90 0C.

6. Method according to any of the preceding claims, wherein during addition of the aqueous alkaline solution and/or the carbonate source, the extract is kept at a temperature within a range of 50 to 90 0C.

7. Method according to one of the preceding claims, wherein the acid extract obtained by extracting a clay has a solid content of less than 20 wt.-%.

8. Method according to any one of the preceding claims, wherein the acid extract obtained by extracting a clay has an acid content of less than 20 wt.-%.

9. Method according to any one of the preceding claims, wherein after adjusting the magnesium concentration in the acid extract the mixture is agitated at least 5 minutes before adding the aqueous alkaline solution.

10. Method according to any one of the preceding claims, wherein after addition of the carbonate source the mixture is reacted for at least 1 hour.

11. Method according to any one of the preceding claims, wherein after separation of the precipitate, the precipitate is washed with water.

12. Method according to one of the preceding claims, wherein the magnesium source comprises Mg(OH)2.

13. Method according to one of the preceding claims, wherein the carbonate source is selected from the group consisting of Na2CO3, NaHCO3, K2CO3, KHCO3, CaCO3, Ca(HCO3J2, MgCO3,

Mg (HCO3) 2.

14. Method according to one of the preceding claims, wherein the aqueous alkaline solution comprises at least one compound selected from the group consisting of NaOH, KOH, Ca(OH)2, Mg(OH)2.

15. Method according to one of the preceding claims, wherein the high shear condition is achieved by stirring the magnesium/aluminium mixture at a rotation speed within a range of 100 - 5000 rpm, preferably in a range of 1000 - 3000 rpm.

16. Method according to one of the preceding claims, wherein the high shear agitation is continued until separation of the precipitate.

17. Method according to one of the preceding claims wherein the adsorbent after drying is not subjected to a calcination procedure.

18. Method according to one of the preceding claims, wherein the clay is selected from the group of smectic clays, preferably from the group consisting of montmorillonite, ben- tonite, hectorite, nontronite, vermiculite, illite, sapo- nite, preferably bentonite.

19. Method according to any one of the preceding claims, wherein the mineral acid used for extracting the clay is selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and mixtures thereof.

20. Method for purification of water, wherein an adsorbent is prepared with a method according to one of claims 1 to 19 and the water to be purified is contacted with the adsorbent.

21. Method according to claim 20, wherein the water to be purified contains sulfur-containing anions.