Method for treating metal-contaminated water and soil

• US 7,029,202 B2
• Filed: 07/22/2002
• Issued: 04/18/2006
• Est. Priority Date: 07/22/2002
• Status: Expired due to Fees

• Current Assignee: NORAM Engineering and Constructors Ltd.
• Original Assignee: NORAM Engineering and Constructors Ltd.
• Inventors: Zhuang, J. Ming
• Primary Examiner(s): Hruskoci, Peter A.
• Application Number:
  US10/199,119
• Publication Number:
  US 20040010955A1
• Time in Patent Office: 1,366 Days
• Field of Search: 210/710, 210/724, 210/725, 210/727, 210912-914, 405/128.5, 405/128.75, 588/256
• US Class Current: 405/128.5
• CPC Class Codes: B09C 1/08 chemically
• CPC Class Codes: C02F 1/5245 using basic salts, e.g. of aluminium and iron
• CPC Class Codes: C02F 1/5263 using natural chemical compounds
• CPC Class Codes: C02F 1/54 using organic material
• CPC Class Codes: C02F 1/56 Macromolecular compounds
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2101/20 Heavy metals or heavy metal compounds
• CPC Class Codes: C02F 2101/22 Chromium or chromium compounds, e.g. chromates
• CPC Class Codes: C02F 2103/06 Contaminated groundwater or leachate
• CPC Class Codes: C02F 2103/10 from quarries or from mining activities
• CPC Class Codes: Y10S 210/912 Heavy metal
• CPC Class Codes: Y10S 210/913 Chromium
• CPC Class Codes: Y10S 210/914 Mercury

Abstract

A method for removing metal contaminants from water uses lignin derivatives, such as lignosulfonates and kraft lignin, a coagulant, such as a metal salt, and a pH-increasing composition. The lignin derivative is dispersed in the contaminated water, the coagulant is added and the pH is adjusted as required to cause flocculation. A sludge is formed that contains the metals and that is separated from the treated water by filtration. Related methods are used to reduce the leachable metal content of contaminated soils. The invention also provides a composition for stabilizing the metal contaminants in soil, comprising lignin derivatives, a coagulant and a composition for increasing the pH. The mixture is blended with the contaminated soil, reducing its leachable metal content.

Claims

1. A method of reducing the leachability of metals of metal-contaminated soil, comprising the steps of:

(a) preparing a mixture comprising;

(i) lignin derivatives;

(ii) an aluminum or iron salt coagulant; and

(iii) a composition selected from the group consisting of hydrated lime, calcium oxide, magnesium hydroxide, soda ash and sodium hydroxide for increasing the pH of said soil, wherein said coagulant forms a complex with said lignin derivatives for scavenging said metals; and

(b) blending said mixture with said soil, to reduce the leachability of said metals in said soil.

2. A method according to claim 1 wherein the metal contaminants comprise one or more of mercury, chromium, copper, lead, nickel and aluminum.

3. A method according to claim 1 wherein said lignin derivatives comprise lignosulfonates.

4. A method according to claim 3 wherein said lignosulfonates comprise one or more of:

(i) ammonium lignosulfonates;

(ii) calcium lignosulfonates;

(iii) sodium lignosulfonates; and

(iv) potassium lignosulfonates.

5. A method according to claim 1 wherein said lignin derivatives comprise kraft lignin.

6. A method according to claim 1 wherein said lignin derivatives comprise sulfonated kraft lignin salts.

7. A method according to claim 6 wherein said sulfonated kraft lignin salts comprise sulfonated kraft lignin salts of ammonium, calcium, sodium or potassium.

8. A method according to claim 1 wherein said iron salt is ferric chloride.

9. A method according to claim 1 wherein said iron salt is ferric sulfate.

11. A method according to claim 1 wherein the mass ratio of said lignin derivatives to said coagulant is at least 1:

0.5.

12. A method according to claim 1 wherein the mass ratio of said lignin derivatives to said coagulant is at least 1:

1.

13. A method according to claim 1 wherein the mass ratio of said lignin derivatives to said coagulant is at least 1:

2.

14. A method according to claim 1 wherein the mass ratio of said lignin derivatives to said composition for increasing the pH is in the range of 1:

1 to 1;

4.

15. A method according to claim 1 wherein the mass ratio of said lignin derivatives to said composition for increasing the pH is in the range of 1:

1 to 1;

8.

16. A method according to claim 1 wherein the mass ratio of said mixture to said soil is in the range of 1:

5 to 1;

100.

10. A method according to claim 10 wherein said aluminum salt is aluminum chloride or aluminum sulfate.

17. A method of reducing the leachability of mercury from a mercury-contaminated soil, comprising the steps of:

(a) preparing a mixture comprising;

(i) a lignin derivative comprising one or more of lignosulfonates and kraft lignin;

(ii) an aqueous ferric chloride solution; and

(iii) hydrated lime, wherein said ferric chloride forms a complex with said lignin derivatives for scavenging said mercury; and

(b) blending said mixture with said contaminated soil, to reduce the leachability of mercury from said soil.

18. A method of reducing the leachability of metals of metal-contaminated soil, comprising the steps of:

(a) preparing a sludge prepared by the process of;

(i) providing water containing humic or fulvic acid and a metal;

(ii) dispersing a metal salt coagulant in said water;

(iii) causing the formation of a floc including said humic or fulvic acid in the mixture of step (a)(ii);

(iv) allowing said floc to coagulate and form said sludge; and

(v) separating said sludge from said treated water; and

(b) blending said sludge with said metal-contaminated soil, to reduce the leachability of said metals in said soil.

19. A method according to claim 18 wherein said step of causing the formation of a floc comprises adjusting the pH of said water so as to cause flocculation.

20. A method according to claim 19 wherein said pH is adjusted by the addition of one or more of hydrated lime, calcium oxide, magnesium hydroxide, soda ash and calcium hydroxide.

21. A method according to claim 19 wherein said pH is adjusted to a pH in the range of 4–

10.

22. A method according to claim 19 wherein said pH is adjusted to a pH in the range of 5–

6.

23. A method according to claim 18 wherein the metal contaminants comprise one or more of mercury, chromium, copper, lead, nickel, zinc and aluminum.

24. A method according to claim 18 wherein said metal salt coagulant is an iron salt.

25. A method according to claim 24 wherein said iron salt is ferric chloride.

26. A method according to claim 24 wherein said iron salt is ferric sulphate.

27. A method according to claim 18 wherein said coagulant is an aluminum salt.

28. A method according to claim 18 wherein said aluminum salt is aluminum chloride or aluminum sulfate.

29. A method according to claim 18 wherein step (d) comprises allowing said floc to settle in a clarifier.

30. A method according to claim 18 step (e) comprises removing said sludge by filtration.

31. A method of reducing the leachability of metals of metal-contaminated soil, comprising the steps of:

(a) preparing a sludge prepared by the process of;

(i) providing water containing humic or fulvic acid and a metal;

(ii) dispersing a metal salt coagulant in said water;

(iii) causing the formation of a floc including said humic or fulvic acid in the mixture of step (a)(ii); and

(iv) separating said floc from an aqueous filtrate; and

(b) blending said separated floc with said metal-contaminated soil, to reduce the leachability of said metals in said soil.

32. A method of reducing the leachability of mercury from a mercury-contaminated soil, comprising the steps of:

(a) providing a sludge prepared by the process of;

(i) providing groundwater containing humic and fulvic acids and mercury;

(ii) dispersing ferric chloride in said water;

(iii) adjusting the pH of said water so as to cause the formation of a floc, including said humic or fulvic acids;

(iv) allowing said floc to coagulate and form said sludge; and

(v) separating said sludge from said treated water; and

(b) blending said sludge with said mercury-contaminated soil, to reduce the leachability of said mercury in said soil.