# US 2021/0276891 A1 · System and method for removing nitrate from water

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- Number: US 2021/0276891 A1
- Document ID: US20210276891A1
- Status: Published application
- Kind: A1
- Application number: 17/195,321
- Filed: 2021-03-08
- Published: 2021-09-09
- Earliest claimed: 2020-03-06
- Assignees: Iowa State University Research Foundation, Inc.
- Applicants: Iowa State University Research Foundation, Inc.
- Inventors: Wenzhen Li; Hengzhou Liu; Yifu Chen
- Web page: https://patentgrep.com/patent/US20210276891A1

## CPC

- C02F 1/4676: {by electroreduction}
- B01D 53/18: Absorbing units; Liquid distributors therefor (B01D3/16, B01D3/26, B01D3/30 take precedence; packing elements B01J19/30, B01J19/32)
- C02F 1/46109: {Electrodes}
- C02F 1/70: by reduction {(C02F1/4676 takes precedence)}
- G01N 30/8624: {Detection of slopes or peaks; baseline correction}
- C01B 21/50: Nitrous acid; Salts thereof
- C02F 1/42: by ion-exchange (ion-exchange in general B01J)
- C02F 2001/422: {using anionic exchangers}
- C02F 2001/46133: {characterised by the material}
- C02F 2001/46161: {Porous electrodes}
- C02F 2101/163: {Nitrates}
- C02F 2103/007: {Contaminated open waterways, rivers, lakes or ponds}
- C02F 2201/46115: Electrolytic cell with membranes or diaphragms
- C02F 2209/06: pH
- G01N 30/96: using ion-exchange (G01N30/02, G01N30/90 take precedence)
- Y02W 10/37: using solar energy
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

The present application relates to a system for removal of nitrate from water. The system includes a first reactor comprising a porous oxide-derived silver electrode (OD-Ag) for electrocatalytic reduction of nitrate (NO3−) to nitrite (NO2−) and a second reactor comprising a Pd-based catalyst for catalytic reduction of nitrite (NO2−). Also disclosed is a method of removing nitrate from water.

## Claims

### Claim 1

A system for removal of nitrate from water, said system comprising:
a first reactor comprising a porous oxide-derived silver electrode (OD-Ag) for electrocatalytic reduction of nitrate (NO3−) to nitrite (NO2−) and
a second reactor comprising a Pd-based catalyst for catalytic reduction of nitrite (NO2−).

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 2)

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.

### Claim 4 (depends on 1)

The system according to claim 1, wherein the pH in the first reactor is at least 4.

### Claim 5 (depends on 4)

The system according to claim 4, wherein the pH in the first reactor is between about 4 and 13.

### Claim 6 (depends on 1)

The system according to claim 1, wherein the system further comprises:
a sealed trap acid solution to absorb NH3.

### Claim 7 (depends on 1)

The system according to claim 1 further comprising:
an online gas chromatography for H2 quantification.

### Claim 8

A method of removing nitrate from water, said method comprising:
providing a system comprising:
a first reactor comprising a porous oxide-derived silver electrode (OD-Ag) for electrocatalytic reduction of nitrate (NO3−) to nitrite (NO2−) and
a second reactor comprising a Pd-based catalyst for catalytic reduction of nitrite (NO2−);
introducing water containing nitrate (NO3−) into the first reactor to cause catalytic reduction of the nitrate into nitrite (NO2−) by the porous oxide-derived silver electrode (OD-Ag); and
introducing water from the first reactor into the second reactor to cause reduction of nitrite (NO2−) by the Pd-based catalyst, thereby removing nitrate from the drinking water.

### Claim 9 (depends on 8)

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

### Claim 10 (depends on 9)

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.

### Claim 11 (depends on 8)

The method according to claim 8, wherein the pH in the first reactor is at least 4.

### Claim 12 (depends on 11)

The method according to claim 11, wherein the pH in the first reactor is between about 4 and 13.

### Claim 13 (depends on 8)

The method according to claim 8, wherein the system further comprises:
a sealed trap acid solution to absorb NH3.

### Claim 14 (depends on 8)

The method according to claim 8, wherein H2 generated from a cathode in the first reactor is used to reduce nitrite in the second reactor.

### Claim 15 (depends on 8)

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.

### Claim 16 (depends on 8)

The method according to claim 8, wherein said method achieves a nitrate (NO3−) concentration of about 1.6-2.5 ppm (as Nitrogen).

### Claim 17 (depends on 8)

The method according to claim 8, wherein said method achieves an NH3 concentration of about 1.1-2.5 ppm NH3 (as Nitrogen).

### Claim 18 (depends on 8)

The method according to claim 8, wherein said method achieves an undetectable nitrite (NO2−) concentration.

### Claim 19 (depends on 8)

The method according to claim 8, wherein molecular nitrogen gas (N2) is a product from nitrite reduction in the second reactor.

### Claim 20 (depends on 19)

The method according to claim 19, wherein the molecular nitrogen gas (N2) is greater than 93% of the product from nitrite reduction in the second reactor.