Diatomaceous earth products containing reduced soluble metal levels, processes for reducing soluble metal levels in diatomaceous earth products, and methods of using the same
Disclosed herein are diatomaceous earth products containing reduced soluble metal levels, processes for reducing soluble metal levels in diatomaceous earth products, and methods of using the same. In particular, diatomaceous earth products are disclosed that have been treated with at least one surface metal blocking agent, and then subjected to at least one thermal treatment process to reduce the level of soluble metals associated therewith. Such diatomaceous earth products containing reduced soluble metal levels may be useful for various applications including, but not limited to, as filter aid materials.
1. A process for making a low soluble metal content diatomaceous earth product, comprising:
treating at least one dry natural diatomaceous earth with at least one dry phosphorus-containing compound; and
subjecting the phosphorus-treated diatomaceous earth material to at least one thermal treatment;
wherein the at least one phosphorus-containing compound is present in an amount ranging from about 0.2% to about 2%, relative to the weight of the at least one natural diatomaceous earth, and
wherein the thermally-treated diatomaceous earth material possesses a soluble metal content less than about 40 ppm, as measured by EBC.
2. The process of claim 1 , wherein the low soluble metal content diatomaceous earth product is a particulate.
3. The process of claim 1 , wherein the at least one phosphorus-containing compound comprises at least one phosphate.
4. The process of claim 3 , wherein the at least one phosphate is chosen from the group consisting of sodium triphosphate, sodium phosphate, sodium pyrophosphate, sodium hexametaphosphate, monobasic potassium phosphate, potassium phosphate, and aluminum phosphate.
5. The process of claim 3 , wherein the at least one phosphate is dibasic sodium phosphate.
6. The process of claim 1 , wherein the thermally-treated diatomaceous earth material possesses a soluble metal content less than about 20 ppm, as measured by EBC.
7. The process of claim 6 , wherein the thermally-treated diatomaceous earth material possesses a soluble metal content less than about 10 ppm, as measured by EBC.
8. The process of claim 1 , wherein the soluble metal content of the thermally-treated diatomaceous earth material is about 50% less than the soluble metal content of the at least one natural diatomaceous earth, as measured by EBC.
9. The process of claim 8 , wherein the soluble metal content of the thermally-treated diatomaceous earth material is about 70% less than the soluble metal content of the at least one natural diatomaceous earth, as measured by EBC.
10. The process of claim 9 , wherein the soluble metal content of the thermally-treated diatomaceous earth material is about 90% less than the soluble metal content of the at least one natural diatomaceous earth, as measured by EBC.
11. The process of claim 1 , wherein the at least one thermal treatment is chosen from the group consisting of calcination, flux calcination, roasting, and microwave plasma heating.
12. The process of claim 1 , wherein the at least one natural diatomaceous earth is treated with the at least one phosphorus-containing compound in an amount ranging from about 0.5% to about 1%, relative to the weight of the at least one natural diatomaceous earth.
13. The process of claim 1 , wherein the process does not include an acid washing step.
14. A thermally-treated diatomaceous earth material comprising at least one phosphorus-containing compound, wherein the material has a soluble metal content less than about 40 ppm, as measured by EBC.
15. A particulate filter aid composition comprising the thermally-treated diatomaceous earth material of claim 14 .
16. A method of filtering a liquid, comprising passing the liquid through at least one filter membrane comprising a thermally-treated diatomaceous earth material comprising at least one phosphorus-containing compound, wherein the material has a soluble metal content less than about 40 ppm, as measured by EBC.
17. The method of claim 16 , wherein the at least one phosphorus-containing compound is present in an amount ranging from about 0.2% to about 2%, relative to the weight of the at least one diatomaceous earth feed material.
18. The method of claim 16 , wherein the liquid is chosen from a beverage, an edible oil, and a fuel oil.
19. The method of claim 18 , wherein the beverage is a beer.
20. The method of claim 18 , wherein the beverage is a wine.