System and method for removing nitrate from water

1. A system for removal of nitrate from water, said system comprising:

a first reactor comprising a nanostructured oxide-derived silver (OD-Ag) electrode for electrocatalytic reduction of nitrate (NO 3 − ) to nitrite (NO 2 − ), wherein the nanostructured OD-Ag electrode comprises a surface, wherein said surface comprises a wave-like morphology, said wave-like morphology comprising peaks and valleys deviating ±250 nm from flatness and

a second reactor comprising a Pd-based catalyst for catalytic reduction of nitrite (NO 2 − ).

2. The system according to claim 1 , wherein the first reactor comprises an H-type cell reactor structure.

3. The system according to claim 2 , wherein the first reactor comprises a catholyte portion and an anolyte portion, wherein the catholyte portion and the anolyte portion are connected by a membrane.

4. The system according to claim 3 , wherein the pH in the catholyte portion and the anolyte portion is at least 4.

5. The system according to claim 4 , wherein the pH in the catholyte portion and the anolyte portion is between about 4 and 13.

6. The system according to claim 1 , wherein the system further comprises:

a sealed trap acid solution to absorb NH 3 .

7. The system according to claim 1 further comprising:

an online gas chromatography unit.

8. A method of removing nitrate from water, said method comprising:

providing a system comprising:

a first reactor comprising a nanostructured oxide-derived silver (OD-Ag) electrode for electrocatalytic reduction of nitrate (NO 3 − ) to nitrite (NO 2 − ), wherein the nanostructured OD-Ag electrode comprises a surface, wherein said surface comprises a wave-like morphology, said wave-like morphology comprising peaks and valleys deviating ±250 nm from flatness and

a second reactor comprising a Pd-based catalyst for catalytic reduction of nitrite (NO 2 − );

introducing water containing nitrate (NO 3 − ) into the first reactor to cause catalytic reduction of the nitrate into nitrite (NO 2 − ) by the nanostructured OD-Ag electrode; and

introducing water from the first reactor into the second reactor to cause reduction of nitrite (NO 2 − ) by the Pd-based catalyst, thereby removing nitrate from the drinking water.

9. The method according to claim 8 , wherein the first reactor has an H-type cell reactor structure.

10. The method according to claim 9 , wherein the first reactor comprises a catholyte portion and an anolyte portion, wherein the catholyte portion and the anolyte portion are connected by a membrane.

11. The method according to claim 10 , wherein the pH in the catholyte portion and the anolyte portion is at least 4.

12. The method according to claim 11 , wherein the pH in the catholyte portion and the anolyte portion is between about 4 and 13.

13. The method according to claim 8 , wherein the system further comprises:

a sealed trap acid solution to absorb NH 3 .

14. The method according to claim 8 , wherein H 2 generated from a cathode in the first reactor is used to reduce nitrite in the second reactor.

15. The method according to claim 8 , wherein said water is selected from one or more of drinking water, agricultural river water, and downstream from an anion exchange column in a water treatment plant.

16. The method according to claim 8 , wherein said method achieves a nitrate (NO 3 − ) concentration of about 1.6-2.5 ppm (as Nitrogen).

17. The method according to claim 8 , wherein said method achieves an NH 3 concentration of about 1.1-2.5 ppm NH 3 (as Nitrogen).

18. The method according to claim 8 , wherein said method achieves an undetectable nitrite (NO 2 − ) concentration.

19. The method according to claim 8 , wherein molecular nitrogen gas (N 2 ) is a product from nitrite reduction in the second reactor.

20. The method according to claim 19 , wherein the molecular nitrogen gas (N 2 ) is greater than 93% of the product from nitrite reduction in the second reactor.