Semi-synthetic bleaching earth
The invention relates to a process of processing an acid suspension containing at least one solid, wherein (a) the suspension containing at least one solid is mixed with an alkali metal silicate solution, the pH of the mixture being adjusted to a pH of more than 4, and (b) the resulting precipitate which contains the alkali metal silicate and the at least one solid is separated and optionally washed, dried and ground. The mixture according to (a) after aging may be acidified further by the addition of an acid. Furthermore, there are disclosed an adsorbent obtainable according to the preceding process, and the use thereof.
1. Process of preparation and processing an acid suspension containing at least one solid, comprising leaching a raw clay with acid to obtain the acid suspension containing at least one solid, said acid suspension having a solid content of at least 10 wt. %, mixing the suspension containing at least one solid with an alkali metal silicate solution to form a mixture, whereby the pH of the mixture is adjusted to a pH of more than 4 to produce a precipitate, and separating the resulting precipitate, formed from the mixing of the alkali metal silicate solution and the acid suspension containing at least one solid, from the suspension.
2. Process according to claim 1 , characterized in that the pH of the mixture is adjusted to a pH of more than 6.
3. Process according to claim 1 further comprising, after mixing, the mixture is further acidified to a pH of less than 4 by the addition of an acid.
4. Process according to claim 1 , characterized in that the mixture is heated prior, during or after the formation of the precipitate to a temperature of more than 70° C.
5. Process according to claim 1 , characterized in that the acid suspension contains metal ions having a valency of at least 2 in dissolved form.
6. Process according to claim 5 , characterized in that the metal ions having a valency of at least 2 comprise iron or aluminum ions.
7. Process according to claim 1 , characterized in that the acid suspension containing at least one solid has an acid content of at least 2.5 weight %, based on the weight of the suspension.
8. Process according to claim 1 , characterized in that the acid suspension contains hydrochloric acid and/or sulphuric acid.
9. Process according to claim 3 , characterized in that the further acidified mixture is heated for at least one hour.
10. Process according to claim 3 , characterized in that the further acidified mixture is heated to a temperature of more than 70° C.
11. Process according to claim 3 , characterized in that the further acidified mixture is heated to boiling.
12. Process according to claim 1 , characterized in that the raw clay comprises a montmorillonite-containing clay.
13. Process according to claim 1 , characterized in that the alkali metal silicate solution has a solid content of at least 2 weight %.
14. Process according to claim 1 , characterized in that the alkali metal silicate solution comprises a water glass solution with a molar ratio of SiO 2 /M 2 O>2.0, wherein M comprises an alkali metal.
15. Process according to claim 1 , characterized in that the temperature of the mixture is maintained above 70° C. during the mixing of the alkali metal silicate solution and the acid suspension containing at least one solid.
16. Process according to claim 3 , characterized in that the acid is added in an amount of at least 5 weight %.
17. Process according to claim 1 , characterized in that the separated precipitate is dried to a moisture content of less than 15 weight %.
18. Process according to claim 17 , characterized in that the separated and dried precipitate is subjected to acid activation.
19. Process according to claim 18 characterized in that the separated and dried precipitate is mixed with a solid organic acid.
20. Process according to claim 19 characterized in that the solid organic acid comprises citric acid.