Soil decontamination by mechanically activated oxidation

• US 7,722,292 B2
• Filed: 03/08/2007
• Issued: 05/25/2010
• Est. Priority Date: 03/08/2007
• Status: Expired due to Fees

• Current Assignee: Golder Associates Limited (WSP Global, Inc.)
• Original Assignee: Golder Associates Limited (WSP Global, Inc.)
• Inventors: Bergeron, Eric, Barbeau, Mathieu
• Primary Examiner(s): KRECK, JANINE MUIR
• Application Number:
  US11/715,383
• Publication Number:
  US 20080221380A1
• Time in Patent Office: 1,174 Days
• Field of Search: 405/128.75, 588/320
• US Class Current: 405/128.75
• CPC Class Codes: B09C 1/08 chemically

Abstract

A method of performing soil decontamination including mechanically mixing the soil with solid oxidant prior to any addition of water and until an exothermic reaction between the oxidant and contaminants within the soil occur, adding only necessary water to obtain an homogeneous mix between the soil and the oxidant, and mechanically mixing the soil with the oxidant and the water for a predetermined period of time to allow the oxidant to at least partially oxidize the contaminants.

Claims

1. A method for decontaminating soil comprising:

(a) adding solid oxidant to the soil;

(b) mechanically mixing the oxidant with the soil until an exothermic reaction occurs between the oxidant and contaminants within the soil;

(c) adding water to obtain a homogeneous mix between the soil and the oxidant while keeping a temperature of the soil above a minimum temperature threshold;

(d) mechanically mixing the soil with the oxidant and the water until the reaction between the oxidant and the contaminants is determined to have slowed down below a given threshold; and

(e) ensuring that a pH of the soil is substantially neutral after step (d) by adding acid to the soil at any time after step (a).

2. The method according to claim 1, wherein steps (a) and (b) are repeated until a temperature of the soil exceeds the minimum temperature threshold.

3. The method according to claim 1, wherein the minimum temperature threshold is about 60°

C.

4. The method according to claim 1, wherein steps (a) through (d) are repeated until a desired contaminant concentration is reached.

5. The method according to claim 4, wherein before step (a) a required oxidant quantity is determined based on the desired contaminant concentration, and step (a) includes adding the oxidant in an amount corresponding to a fraction of the required oxidant quantity.

6. The method according to claim 1, further comprising after step (e) a step of letting the substantially neutral soil rest for further reaction between the oxidant and the contaminants to occur.

7. The method according to claim 6, further including adding additional oxidant to the substantially neutral soil before letting the substantially neutral soil rest.

8. The method according to claim 1, wherein step (c) includes adding water to obtain a soil water content of between approximately 5% W/W and approximately 8% W/W.

9. The method according to claim 1, wherein step (b) includes mechanically mixing the oxidant with the soil in a continuous manner for a period lasting between 5 minutes and 20 minutes.

10. The method according to claim 1, wherein step (d) includes mechanically mixing the soil with the oxidant and the water in a continuous manner.

11. The method according to claim 1, wherein step (d) includes mechanically mixing the soil with the oxidant and the water for a period lasting between 4 hours and 20 hours.

12. The method according to claim 1, wherein step (a) includes adding between 5 and 20 g of the oxidant per g of the contaminants.

13. The method according to claim 1, wherein before step (a) the soil is excavated and put in an ex-situ mixer, and steps (a) through (e) are performed in the ex-situ mixer.

14. The method according to claim 1, wherein step (c) is only performed after step (b).

15. The method according to claim 1, wherein in step (d) the reaction between the oxidant and contaminants is determined to have slowed down below the given threshold based on at least one of a temperature variation of the soil and a color variation of the soil during step (d).

16. The method according to claim 1, wherein the oxidant is permanganate.

17. A method of performing soil decontamination comprising mechanically mixing the soil with solid oxidant prior to any addition of water and until an exothermic reaction between the oxidant and contaminants within the soil occur, adding only necessary water during decontamination to obtain an homogeneous mix between the soil and the oxidant, and mechanically mixing the soil with the oxidant and the water for a predetermined period of time to allow the oxidant to at least partially oxidize the contaminants.

19. The method according to claim 17, wherein the water is added such as to obtain a soil water content of between approximately 5% W/W and approximately 8% W/W.

20. The method according to claim 17, wherein the predetermined period of time is between 4 hours and 20 hours.

21. The method according to claim 17, wherein mixing of the soil with the oxidant prior to any addition of water is performed in a continuous manner for a period lasting between 5 minutes and 20 minutes.

22. The method according to claim 17, wherein mixing of the soil with the oxidant prior to any addition of water is performed until a soil temperature reaches a temperature threshold of between about 40°

C. and about 80°

C., a quantity of the oxidant being selected to reach the temperature threshold.

23. The method according to claim 17, wherein the oxidant is permanganate.

18. A method of performing decontamination comprising mechanically mixing the soil with solid oxidant prior to any addition at water and until an exothermic reaction between the oxidant and contaminants within the soil occur, adding only necessary water to obtain an homogeneous mix between the soil and the oxidant, mechanically mixing the soil with the oxidant and the water for a predetermined period of time to allow the oxidant to at least partially oxidize the contaminants, and adding acid to the soil to ensure that a pH of the soil is substantially neutral after the predetermined period of time.