Cactus mucilage and ferric ions for the removal of arsenate (As(V)) from water

Patent metadata

Field	Value
Publication number	US-9776895-B2
Application number	US-201414206404-A
Country	US
Kind code	B2
Filing date	Mar 12, 2014
Priority date	Sep 14, 2011
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

Potable drinking water is plagued with widespread arsenic contamination, particularly in developing communities. Ferric ions were introduced to interact with arsenate based on the strong affinity of arsenate for ferric hydroxides, followed by mucilage addition. The mucilage coagulated and flocculated the ferric-arsenate complex and formed visible flocs that settled at the bottom of the tubes. The system showed 75-96% arsenate removal in 1 hour, while longer retention times showed 100% removal. The role of the mucilage was demonstrated by untreated solutions showing no concentration difference and remaining stable for more than 15 days. This mucilage-based technology has the potential to be a relatively inexpensive, environmentally sustainable alternative to synthetic polymer flocculants for removing arsenic from drinking water.

First claim

What is claimed is:

1. A method of removing arsenic contamination from a sample of water, comprising:
obtaining a sample of water, wherein the sample of water is contaminated with arsenic;
dosing the sample of water with a ferric salt prior to addition of a gelling extract from a cactus;
allowing the ferric salt to interact with the arsenic;
adding the gelling extract obtained from the cactus to the sample of water after dosing the sample of water with the ferric salt and allowing the ferric salt to interact with the arsenic, where the gelling extract is obtained by the steps further comprising:
obtaining cactus pads;
dicing and boiling the cactus pads;
liquidizing the cactus pads and adding a base to neutralize the liquidized cactus pads;
centrifuging the liquidized cactus pads into a liquid fraction and a solid precipitate;
collecting the solid precipitate;
adding sodium hexametaphosphate to the solid precipitate and mixing;
filtering the solid precipitate;
resuspending the solid precipitate in water to form a suspension;
lowering the pH of the suspension;
precipitating a mucilage precipitate from the suspension;
resuspending the mucilage precipitate with deionized water and adjusting the pH until the mucilage precipitate dissolves;
filtering the dissolved mucilage precipitate to form the gelling extract;

mixing the sample of water and gelling extract; and
allowing the sample of water to cure, wherein during the curing step arsenic precipitates out of the sample of water.

2. The method of claim 1 , wherein the gelling extract is added at a final concentration of between about 50 and about 500 mg/L.

3. The method of claim 2 , wherein the gelling extract is at a final concentration of between about 100 mg/L and about 200 mg/L.

4. The method of claim 2 , wherein the gelling extract is at a final concentration of 100 mg/L.

5. The method of claim 1 , wherein the ferric salt is ferric nitrate, ferric chloride, ferric sulfate, ferric carbonate, ferric gluconate, ferric oxalate, or saccharated ferric oxide.

6. The method of claim 5 , wherein the ferric salt is dosed at a final concentration of between about 6 mg/L and about 50 mg/L.

7. The method of claim 6 , wherein the ferric salt is at a final concentration of between about 26 mg/L and about 50 mg/L.

8. The method of claim 7 , wherein the ferric salt at a final concentration of between about 40 mg/L and about 50 mg/L.

9. The method of claim 1 , further comprising allowing the sample of water and added ferric salt and added gelling extract to stand for at least 10 min.

10. The method of claim 9 , wherein the water and added ferric salt and added gelling extract stands for about 1 hour.

11. The method of claim 9 , wherein the water and added ferric salt and added gelling extract stands for about 24 h.

12. The method of claim 1 , further comprising filtering residual iron and mucilage from the sample of water further comprising:
collecting the sample of water after precipitation of arsenic; and
running the sample of water through filter cloth, filter paper, Buchner funnel, rotary vacuum-drum filter, screen filter, sand filter, fine mesh sieve, coffee filter, ceramic membrane size-exclusion filter, cellulose acetate membrane size-exclusion filter, polyvinylidene fluoride membrane size-exclusion filter, polyacrylonitrile membrane size-exclusion filter, polypropylene membrane size-exclusion filter, polysulfone membrane size-exclusion filter, polyethersulfone membrane size-exclusion filter, polyamide membrane size-exclusion filter, hollow fiber filter, or a combination thereof in sequence.

13. The method of claim 1 , further comprising hydrolyzing the ferric salt prior to addition to the sample of water.

14. The method of claim 13 , wherein the ferric salt is aged in water for at least 48 hours to hydrolyze the ferric salt.

15. A method of removing arsenic contamination from a sample of water, comprising:
obtaining a sample of water, wherein the sample of water is co, urinated with arsenic;
dosing the sample of water with a hydrolyzed ferric salt, wherein the hydrolyzed ferric salt is obtained by aging ferric salt in water for at least 48 hours prior to addition to the sample of water;
allowing the hydrolyzed ferric salt to interact with the arsenic;
adding a gelling extract obtained from cactus to the sample of water after dosing the sample of water with the hydrolyzed ferric salt, where the gelling extract is obtained by the steps further comprising:
obtaining cactus pads;
dicing and boiling the cactus pads;
liquidizing the cactus pads and adding a base to neutralize the liquidized cactus pad;
centrifuging the liquidized cactus pads into a liquid fraction and a solid precipitate;
collecting the solid precipitate;
adding sodium hexametaphosphate to the solid precipitate and mixing;
filtering the solid precipitate;
resuspending the solid precipitate in water to form a suspension;
lowering the pH of the suspension;
precipitating a mucilage precipitate from the suspension;
resuspending the mucilage precipitate with deionized water and adjusting the pH until the mucilage precipitate dissolves;
filtering the dissolved mucilage precipitate to form the gelling extract;
wherein the gelling extract is added at a final concentration of between about 50 and about 500 mg/L;

mixing the sample of water and gelling extract; and
allowing the sample of water to cure, wherein during the curing step arsenic precipitates out of the sample of water.

16. The method of claim 15 , wherein the gelling extract is at a final concentration of 100 mg/L.

17. The method of claim 15 , wherein the ferric salt is ferric nitrate, ferric chloride, ferric sulfate, ferric carbonate, ferric gluconate, ferric oxalate, or saccharated ferric oxide.

18. The method of claim 17 , wherein the ferric salt is at a final concentration of between about 40 mg/L and about 50 mg/L.

19. The method of claim 15 , further comprising allowing the sample of water, added hydrolyzed ferric salt, and added gelling extract to stand for at least 10 min.

20. The method of claim 19 , wherein the water and added hydrolyzed ferric salt and added gelling extract to stand for about 24 h.

21. The method of claim 15 , further comprising filtering residual iron and mucilage from the sample of water further comprising:
collecting the sample of water after precipitation of arsenic; and
running the sample of water through filter cloth, filter cloth, filter paper, Buchner funnel, rotary vacuum-drum filter, screen filter, sand filter, fine mesh sieve, coffee filter, ceramic membrane size-exclusion filter, cellulose acetate membrane size-exclusion filter, polyvinylidene fluoride membrane size-exclusion filter, polyacrylonitrile membrane size-exclusion filter, polypropylene membrane size-exclusion filter, polysulfone membrane size-exclusion filter, polyethersulfone membrane size-exclusion filter, polyamide membrane size-exclusion filter, hollow fiber filter, or a combination thereof in sequence.

Assignees

• Alcantar Norma A
• Fox Dawn I
• Univ South Florida

Inventors

• Alcantar Norma A
• Fox Dawn I

Classifications

• C02F1/62

  Heavy metal compounds · CPC title

• C02F1/5236

  using inorganic agents · CPC title

• B01D21/01

  using flocculating agents (for purifying water C02F1/52; for liquid radioactive waste G21F9/10) · CPC title

• C02F1/56

  Macromolecular compounds · CPC title

• C02F1/286

  using natural organic sorbents or derivatives thereof · CPC title