Method of removing particulate silicon from an effluent water

Patent metadata

Field	Value
Publication number	US-9828263-B2
Application number	US-201414470998-A
Country	US
Kind code	B2
Filing date	Aug 28, 2014
Priority date	Aug 28, 2014
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A method of removing particulate silicon from an effluent water in accordance with various embodiments may include: adding a base to the effluent water, an amount of the added base being sub-stoichiometric with regard to a basic oxidation reaction of an entire amount of silicon contained in the effluent water to ortho-silicic acid or ortho-silicate ions; maintaining a resulting mixture of the effluent water and the base in a predetermined temperature range for a period of time, so that a sediment including silicon is formed; and separating the sediment and the effluent water from each other.

First claim

What is claimed is:

1. A method of removing elementary solid particulate silicon from an effluent water containing elementary solid particulate silicon, the method comprising:
adding a base to the effluent water, an amount of the added base being sub-stoichiometric with regard to a basic oxidation reaction of an entire amount of silicon contained in the effluent water to ortho-silicic acid;
forming a sediment including silicon, wherein forming the sediment comprises:
maintaining a resulting mixture of the effluent water and the base in a predetermined temperature range for a period of time, wherein the formed sediment comprises an agglomeration of at least a portion of the solid particulate silicon that has reacted with the base; and
separating the sediment and the effluent water from each other,

wherein the particulate silicon is removed from the effluent water without adding a metallic salt to the effluent water in addition to the base, and
wherein the sediment is formed in the absence of a precipitation reaction.

2. The method of claim 1 , wherein the base comprises one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide and ammonia.

3. The method of claim 1 , wherein the base is added in the form of an alkaline solution.

4. The method of claim 3 , wherein the alkaline solution is selected from the group consisting of a sodium hydroxide solution, a potassium hydroxide solution, a calcium hydroxide solution, a barium hydroxide solution, an ammonia solution and combinations thereof.

5. The method of claim 1 , wherein the base is added to the effluent water in such an amount that a molar ratio of aqueous hydroxide ions provided by the base in the effluent water to silicon contained in the effluent water is equal to or less than 1:1.

6. The method of claim 1 , wherein the base is added to the effluent water in such an amount that a molar ratio of aqueous hydroxide ions provided by the base in the effluent to silicon contained in the effluent water is greater than or equal to 0.01:1.

7. The method of claim 1 , wherein the predetermined temperature range is equal to or higher than 40° C.

8. The method of claim 1 , wherein the predetermined temperature range is smaller than the boiling temperature of the base.

9. The method of claim 1 , wherein the predetermined temperature range is equal to or smaller than 90° C.

10. The method of claim 1 , wherein the period of time is greater than or equal to 2 minutes.

11. The method of claim 1 , wherein the period of time is less than or equal to 14 minutes.

12. The method of claim 1 , the method further comprising:
adding to the effluent water a component selected from the group consisting of diammonium phosphate, mono-ammonium phosphate, ammonium sulfate, ammonium hydrogen sulfate and combinations thereof.

13. The method of claim 12 , wherein the component is added in an amount of equal to or less than 20 mol %.

14. The method of claim 12 , wherein the component is added in an amount of equal to or more than 5 mol %.

15. The method of claim 1 , wherein the effluent water originates from a production of one or more chips and/or from a processing of one or more wafers.

16. The method of claim 1 , wherein the effluent water contains silicon particles in a mass concentration of equal to or less than 250 mg per liter, or wherein a size of silicon particles contained in the effluent water is in a sub micrometer range.

17. The method of claim 1 , wherein the sediment is formed in the absence of a co-precipitation reaction.

18. The method of claim 1 , wherein the effluent water contains a dopant, and wherein the dopant is at least partially removed from the effluent water together with silicon via the sediment.

19. The method of claim 1 , wherein the at least a portion of the solid particulate silicon that has reacted with the base comprises partially oxidized silicon particles.

20. A method of removing elementary solid particulate silicon from an effluent water containing elementary solid particulate silicon, the method comprising:
adding a base to the effluent water in such an amount that a molar ratio of aqueous hydroxide ions provided by the base in the effluent water to silicon contained in the effluent water is less than or equal to 2:1;
forming a sediment including silicon, wherein forming the sediment comprises:
maintaining a resulting mixture of the base and the effluent water in a predetermined temperature range for a period of time, wherein the sediment comprises an agglomeration of at least a portion of the solid particulate silicon that has reacted with the base; and

separating the sediment and the effluent water from each other,
wherein the particulate silicon is removed from the effluent water without adding a metallic salt to the effluent water in addition to the base, and
wherein the sediment is formed in the absence of a precipitation reaction.

21. A method of removing elementary solid particulate silicon from an effluent water containing elementary solid particulate silicon, the method comprising:
providing 0.02 to 0.1 mol of dissolved sodium hydroxide in the effluent water per gram silicon contained in the effluent water or
providing 0.02 to 0.1 mol of dissolved potassium hydroxide in the effluent water per gram silicon contained in the effluent water or
providing 0.01 to 0.05 mol of dissolved calcium hydroxide in the effluent water per gram silicon contained in the effluent water or
providing 0.02 to 0.1 mol of dissolved barium hydroxide in the effluent water per gram silicon contained in the effluent water or
providing 0.02 to 0.1 mol of ammonium in the effluent water per gram silicon contained in the effluent water or
providing 0.02 to 0.1 mol of dissolved sodium hydroxide in the effluent water per gram silicon contained in the effluent water, wherein the dissolved sodium hydroxide is partially or entirely substituted with one or more of the following: dissolved potassium hydroxide in a molar substitution ratio of 1:1, dissolved calcium hydroxide in a molar substitution ratio of 1:2, dissolved barium hydroxide in a molar substitution ratio of 1:2 and ammonium in a molar substitution ratio of 1:1;
forming a sediment including silicon, wherein forming the sediment comprises:
maintaining a resulting mixture of the effluent water and one or more of the dissolved sodium hydroxide, the dissolved potassium hydroxide, the dissolved calcium hydroxide, the dissolved barium hydroxide and the ammonium in a predetermined temperature range for a period of time, wherein the sediment comprises an agglomeration of at least a portion of the solid particulate silicon that has reacted with the base; and

separating the sediment and the effluent water from each other,
wherein the particulate silicon is removed from the effluent water without adding a metallic salt to the effluent water in addition to the base, and
wherein the sediment is formed in the absence of a precipitation reaction.

Assignees

• Infineon Technologies Ag

Inventors

• Kroener Friedrich
• Kroener Zeljka

Classifications

• C02F2305/02

  Specific form of oxidant · CPC title

• C02F2101/10

  Inorganic compounds · CPC title

• C02F1/72

  by oxidation {(C02F1/4672 takes precedence)} · CPC title

• C02F2101/103

  Arsenic compounds · CPC title

• C02F1/5236 Primary

  using inorganic agents · CPC title