WO2022186452A1

WO2022186452A1 - Apparatus and method for recovery of ammonia in wastewater

Info

Publication number: WO2022186452A1
Application number: PCT/KR2021/017541
Authority: WO
Inventors: 한종인; 이광택
Original assignee: 한국과학기술원
Priority date: 2021-03-03
Filing date: 2021-11-25
Publication date: 2022-09-09
Also published as: KR20220124512A

Abstract

An apparatus for recovery of ammonia comprises: a reaction tank containing ammonia or ammonium ion-containing wastewater; an oxidation electrode connected to the reaction tank, where an oxidation reaction takes place; a reduction electrode facing the oxidation electrode, where a reduction reaction occurs; a cation exchange membrane located between the oxidation electrode and the reduction electrode and allowing ammonium ions to pass therethrough; and a power supply device connected to the oxidation electrode and the reduction electrode to supply electrical energy.

Description

Apparatus and method for recovering ammonia present in wastewater

An apparatus and method for recovering ammonia in wastewater are provided.

The high concentration of ammonia that may exist in the wastewater causes defects in the operation of the bioreactor and causes environmental problems such as eutrophication when discharged to water.

Ammonia may be treated by 1) ammonia stripping, 2) struvite mineral precipitation method, 3) ion exchange method, and the like.

In the case of the ammonia stripping method, high-efficiency removal and recovery of ammonia is possible, but the energy consumption is large.

In the case of struvite mineral precipitation, ammonia is recoverable in the form of solid salt, but since Mg ²⁺ , NH ⁴⁺ , and PO ₄ ^3- react in a 1:1:1 ratio, it is not necessary to inject additional pollutants have.

In the case of the ion exchange method, ammonia can be selectively removed and recovered, but a large amount of salt such as NaCl is required for regeneration of the ion exchange resin.

Accordingly, various studies and developments have been made on low-energy and high-efficiency operation for the recovery of ammonia.

One embodiment of the present invention is to purely recover only ammonia in wastewater.

One embodiment of the present invention is to recover ammonia present in wastewater in a pure gaseous state.

One embodiment of the present invention is to purely recover ammonia in a gaseous state using an electrochemical system.

One embodiment of the present invention is to increase the economic efficiency and productivity of the ammonia removal and recovery process.

In addition to the above problems, the embodiment according to the present invention may be used to achieve other problems not specifically mentioned.

Ammonia recovery apparatus according to an embodiment of the present invention is connected to a reaction tank containing wastewater containing ammonia or ammonium ions, the reaction tank, the oxidation reaction takes place, the anode opposite to the oxidation electrode and the reduction reaction occurs, the oxidation electrode It is located between the and the cathode, and includes a cation exchange membrane through which ammonium ions pass, and a power supply device connected to the anode and the cathode to supply electrical energy.

Ammonium ions are converted to ammonia, and gaseous ammonia can be recovered.

Ammonium ions can be concentrated into liquid ammonia by reacting with hydroxide ions generated between the cathode and the cation exchange membrane.

The concentrated liquid ammonia may be recovered as gaseous ammonia by air or oxygen supplied to the cathode.

Hydroxide ions may be generated by a reduction reaction of oxygen or a reduction reaction of water at the reduction electrode.

The wastewater may contain organic matter, and the organic matter may be decomposed by an oxidation reaction at the anode.

The ammonia recovery device may further include a catalyst located on the cathode.

The movement speed of ammonium ions can be controlled by adjusting the voltage applied to the power supply.

The concentration of recovered ammonia can be controlled by adjusting the flow rate of air or oxygen supplied to the cathode.

Ammonia recovery method according to an embodiment includes the steps of putting wastewater containing ammonia or ammonium ions in a reaction tank, an oxidation reaction taking place in an anode connected to the reaction tank, a reduction reaction occurring in a cathode facing the anode electrode , a step of passing ammonium ions in a cation exchange membrane positioned between the anode and the cathode, and a power supply connected to the anode and the cathode for supplying electrical energy.

The electrochemical device for an ammonia recovery device according to an embodiment is a reaction tank containing ammonia or ammonium ion-containing wastewater, connected to the reaction tank, an oxidation electrode where an oxidation reaction occurs, a reduction electrode facing the oxidation electrode and a reduction reaction occurs, oxidation It is located between the electrode and the cathode, and includes a cation exchange membrane through which ammonium ions pass, and a power supply device connected to the anode and the cathode to supply electrical energy.

The electrochemical device for the ammonia recovery device may further include a catalyst positioned on the reduction electrode.

According to one embodiment of the present invention, it is possible to recover only the gaseous pure ammonia gas from the wastewater by using the electrochemical device, and it is possible to increase the economic efficiency and productivity of the ammonia removal and recovery process.

1 is a view showing an apparatus for removing ammonia in wastewater and recovering gaseous pure ammonia according to an embodiment.

2 is a result of absorbing ammonia separated purely from an electrochemical device in a sulfuric acid solution according to the supplied air flow rate and measuring the result over time.

3 is a result showing the recovery efficiency of ammonia separated from the anode reaction tank.

With reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of a well-known known technology, a detailed description thereof will be omitted.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Then, the ammonia recovery apparatus according to an embodiment will be described in detail.

1 is a schematic configuration diagram of an ammonia recovery apparatus according to an embodiment.

The ammonia recovery device according to an embodiment may include an electrochemical device 100 for recovering ammonia.

The electrochemical device 100 for recovering ammonia may include an electrochemical cell capable of recovering pure ammonia by an electrochemical method. For example, the electrochemical apparatus 100 for recovering ammonia includes an electrochemical cell capable of separating ammonia or ammonium ions contained in the wastewater and converting the ammonia or ammonium ions into ammonia to degas and recover in gaseous form.

The electrochemical device 100 is a pair of electrodes including a reaction tank 140 containing high concentration ammonia, ammonium ions, etc., an oxidation electrode 110 inducing an oxidation reaction, and a reduction electrode 120 inducing a reduction reaction, And it includes a cation exchange membrane (CEM, Cation exchange membrane) 150 for separating the pair of electrodes.

A solution containing a high concentration of ammonia, ammonium ions, etc. may contain wastewater that must be purified through a treatment facility such as livestock wastewater.

The cation exchange membrane 150 is positioned between the anode 110 and the cathode 120 for separation of ammonium ions inside the electrochemical device 100 . Ions passing through the cation exchange membrane 150 may include ammonium ions (NH ₄ ⁺ ).

The cathode 120 may include a gas diffusion electrode (GDE, gas diffusion membrane) through which the gas may pass.

The ammonia recovery device may further include a gas supply device 160 for supplying a gas to induce a reduction reaction of the electrochemical device 100 and degassing ammonia converted between the cation exchange membrane 150 and the reduction electrode 120 . can For example, the gas supplied from the gas supply device 160 may be air or oxygen. The operating energy of the ammonia recovery device may be reduced by the oxygen gas present in the air among the supplied gas. In addition, by adjusting the flow rate of air or oxygen supplied from the gas supply device 160, the concentration of the recovered ammonia may be adjusted. Ammonia concentrated to a high concentration may be degassed by the air supplied from the gas supply device 160 . The separated ammonia can be recovered purely in gaseous form without an additional stripping process.

For example, the ammonia recovery device may further include an air blower for supplying air to the gas diffusion electrode. At the gas diffusion electrode, gaseous ammonia may be separated and recovered.

Ammonium ions may be separated through the cation exchange membrane 150 in the reaction tank 140 . The moved ammonium ions may react with the hydroxide ions generated between the reduction electrode 120 and the cation exchange membrane 150 to be directly concentrated in the form of ammonia. Here, hydroxide ions may be generated by a reduction reaction of oxygen or a reduction reaction of water under a platinum-based catalyst. In addition, ammonia generated between the cathode 120 and the cation exchange membrane 150 may be directly concentrated to a high concentration.

For example, ammonium ions that have passed through the cation exchange membrane 150 from the reaction tank 140 are converted to the form of hydroxide ions (OH ^- ) and ammonia (NH ₃ ) generated on the surface of the reduction electrode 120 through Reaction Equation 1 (NH 3 ). can

[Scheme 1]

NH ₄ ⁺ + OH ^- → NH ₃ (aq) + H ₂ O

Ammonia produced and dissolved by Reaction Equation 1 may be degassed in a gaseous state through Reaction Equation 2 by the supplied air.

[Scheme 2]

NH ₃ (aq) → NH ₃ (g)

Ammonia generated in the electrochemical device 100 may be recovered in the form of a pure gas having a specific concentration without including other interfering substances.

The oxidation electrode 110 is located inside the electrochemical device 100 and is an electrode where an oxidation reaction occurs when an electrochemical reaction occurs as an anode. In this case, the anode 110 may be included in the reaction tank 140 . Sewage water containing ammonia may be circulated and introduced into the reaction tank 140 .

The reduction electrode 120 is located inside the electrochemical device 100 and is an electrode where the reduction reaction occurs when the electrochemical reaction occurs as a cathode of the electrochemical device 100 . The surface of the cathode 120 may include a catalyst 130 capable of increasing the surface reaction of the cathode 120 .

The power supply unit 170 supplies electrical energy for separation of ammonium ions inside the electrochemical device 100 . When a voltage is applied by connecting the anode 110 and the cathode 120 using the power supply 170, water is decomposed in the anode 110 to generate oxygen and hydrogen ions, and oxidized Electrons may be provided at the same time as the reaction, and accordingly, carbon-based organic materials present in the wastewater may be oxidized and decomposed. By adjusting the voltage applied to the power supply unit 170, the movement speed of ammonium ions may be controlled.

When a voltage is applied, the oxidation reaction of water occurring on the surface of the anode 110 may be expressed by the following Reaction Equation 1.

[Scheme 1]

2H ₂ O → O ₂ + 4H ⁺ + 4e ^-

When a voltage is applied, the oxidation reaction of the organic material in the typical urban wastewater that occurs on the surface of the anode 110 may be expressed by the following Reaction Equation 2.

[Scheme 2]

1/50C ₁₀ H ₁₉ O ₃ N + 9/25H ₂ O → 9/50CO ₂ + 1/50 NH ₄ ⁺ + 1/50HCO ₃ ^- + H ⁺ + e ^-

When a voltage is applied, the oxidation reaction of a typical protein that occurs on the surface of the anode 110 can be expressed by the following Reaction Equation 3.

[Scheme 3]

1/66C ₁₆ H ₂₄ O ₅ N ₄ + 27/66H ₂ O → 8/33CO ₂ + 2/33 NH ₄ ⁺ + 13/33H ⁺ + e ^-

When a voltage is applied, the oxidation reaction of formic acid occurring on the surface of the anode 110 may be expressed by the following Reaction Equation 4.

[Scheme 4]

1/2HCOO ^- + 1/2H ₂ O → 1/2HCO ₃ ^- + H ⁺ + e ^-

When a voltage is applied, the oxidation reaction of glucose occurring on the surface of the anode 110 may be expressed by the following Reaction Equation 5.

[Scheme 5]

1/24C ₆ H ₁₂ O ₆ + 1/4H ₂ O → 1/4CO ₂ + H ⁺ + e ^-

When a voltage is applied, the oxidation reaction of carbohydrates occurring on the surface of the anode 110 may be expressed by the following Reaction Equation 6.

[Scheme 6]

1/4CH ₂ O + 1/4H ₂ O → 1/4CO ₂ + H ⁺ + e ^-

When a voltage is applied, the oxidation reaction of pyruvic acid, which is a representative material among volatile organic acids, occurring on the surface of the anode 110 can be expressed by the following Reaction Equation 7.

[Scheme 7]

1/10CH ₃ COCOO ^- + 2/5H ₂ O → 1/5CO ₂ + 1/10HCO ₃ ^- + H ^_ + e ^-

When a voltage is applied, the oxidation reaction of propionic acid, which is a representative material among volatile organic acids, occurring on the surface of the anode 110 may be expressed by the following Reaction Equation 8.

[Scheme 8]

1/14CH ₃ CH ₂ COO ^- + 5/14H ₂ O → 1/7CO ₂ + 1/14HCO ₃ ^- + H ^_ + e ^-

When a voltage is applied, the oxidation reaction of acetic acid occurring on the surface of the anode 110 may be expressed by the following Reaction Equation 9.

[Scheme 9]

1/8CH ₃ COO ^- + 3/8H ₂ O → 1/8CO ₂ + 1/8HCO ₃ ^- + H ^_ + e ^-

The supplied electrons may be supplied to the cathode 120 via a wire connected to the power supply 170 . The cathode 120 may be an electrode made of carbon having micropores, for example, several tens of micrometers, and gas may pass therethrough.

The catalyst 130 may be applied to the reduction electrode 120 . For example, the catalyst 130 may be a platinum-based catalyst. The total energy requirement of the electrochemical device 100 for recovering ammonia may be reduced by the applied catalyst 130 . The catalyst may induce a reduction reaction of oxygen or water.

Air containing oxygen may be supplied in the direction of the cathode 120 having micropores by using the gas supply device 160 . The flow rate of air can be flexibly adjusted according to the applied voltage or current. Oxygen containing about 21% concentration in the supplied air may be reduced in the reduction electrode 120 coated with the catalyst 130 , and may also be reduced in water that may exist between the catalyst 130 and the cation exchange membrane 150 . may cause a reaction.

When a voltage is applied, the reduction reaction of oxygen occurring on the surface of the reduction electrode 120 may be expressed by the following Reaction Equation 10.

[Scheme 10]

O ₂ + 2H ₂ O + 4e ^- → 4OH ^-

When a voltage is applied, the reduction reaction of water occurring on the surface of the cathode 120 may be expressed by the following Reaction Equation 11.

[Scheme 11]

H ₂ O + e ^- → 1/2H ₂ + OH ^-

A voltage is applied by the power supply unit 170, and when electrons move from the anode 110 to the cathode 120, ammonium ions are generated between the anode 110 and the cathode 120 to match electrical neutrality. It can move through the cation exchange membrane 150 installed in the The speed of moving ammonium ions may be adjusted by adjusting the applied voltage of the power supply unit 170 . In addition to ammonium ions, various cations such as hydrogen ions, sodium ions, potassium ions, and calcium ions can also move, but only in wastewater containing a high concentration of ammonium ions, ammonium ions can serve as the first charge carrier. For example, the high concentration of ammonium ions may be at a concentration of 3,000 mg/L or more per 1 L of wastewater.

Ammonium ions flowing in the direction of the cathode 120 may be converted to liquid ammonia by combining with hydroxide ions generated by Reaction Scheme 10 or Reaction Scheme 11, and the reaction to be converted into liquid ammonia may be expressed by Scheme 12 below.

[Scheme 12]

NH ₄ ⁺ + OH ^- → NH ₃ (l) + H ₂ O

Since the liquid ammonia produced has a very high solubility of about 520 g/L at about 20 ^o C, it may be difficult to convert to gaseous phase and degas. However, since the space between the cation exchange membrane 150 and the cathode 120 is very narrow compared to the volume of the reaction tank 140, the liquid ammonia flowing over can be concentrated to a very high concentration. Therefore, the ammonia stripping reaction can occur directly in the electrochemical device 100 for recovering ammonia by the gas supplied by the gas supply device 160 without additional energy supply. As a result, gaseous ammonia may be produced.

Since the gases that are degassed, generated, or supplied from the electrochemical device 100 for recovering ammonia are ammonia, nitrogen, hydrogen, and oxygen, gaseous ammonia can be directly recovered.

2 is a result showing the ammonia recovery amount according to the air flow rate per unit electrode area supplied by the gas supply device (160). For ease of measurement, the ammonia concentration is measured using the Nessler method after absorbing ammonia discharged in the gas phase into the sulfuric acid tank.

While the flow rate supplied to the cathode 120 is increased from about 5 mL/min/cm ² to about 20 mL/min/cm ² It is confirmed that the amount of ammonia recovery is increased by about 2 times. Since desorption of ammonia occurs by effective contact of gas and liquid, it is confirmed that excess ammonia is degassed at a high flow rate. At this time, the supplied air flow rate may be adjusted to adjust the concentration of gaseous ammonia.

3 is a result showing the ratio of ammonia ions present in the reaction tank 140 are transferred through the cation exchange membrane 150 in the form of ions, and the converted ammonia is desorbed by the gas supply unit 160 .

When the flow rate supplied to the cathode 120 by the gas supply device 160 is increased from about 5 mL/min/cm ² to about 20 mL/min/cm ² , the ammonia recovery rate is from about 55% to about 98% It can be seen that increases up to

Then, a method for recovering ammonia according to an embodiment will be described in detail. A description overlapping with the description of the above-described ammonia recovery device will be omitted.

Ammonia recovery method includes a step of putting wastewater containing ammonia or ammonium ions in a reaction tank, an oxidation reaction taking place in an anode connected to the reaction tank, a step in which a reduction reaction occurs in a cathode facing the anode electrode, and an anode and A step of passing ammonium ions in the cation exchange membrane positioned between the cathodes, and a power supply connected to the anode and the cathode for supplying electrical energy.

Ammonium ions are converted to ammonia, and gaseous ammonia can be recovered.

The concentrated liquid ammonia may be recovered as gaseous ammonia by oxygen supplied to the cathode.

A reduction reaction can be induced in the catalyst located on the reduction electrode.

The concentration of recovered ammonia can be controlled by adjusting the flow rate of oxygen supplied to the cathode.

Then, an electrochemical device for an ammonia recovery device according to an embodiment will be described in detail. A description overlapping with the description of the above-described ammonia recovery device will be omitted.

The electrochemical device for the ammonia recovery device is connected to a reaction tank containing ammonia or ammonium ion-containing wastewater, the reaction tank, an anode where an oxidation reaction occurs, a cathode opposite to the anode and where a reduction reaction occurs, and between the anode and the cathode. Located in the cation exchange membrane through which ammonium ions pass, and a power supply device connected to the anode and cathode to supply electrical energy.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

Claims

a reactor containing wastewater containing ammonia or ammonium ions;

an anode connected to the reaction tank, where an oxidation reaction occurs,

a reduction electrode facing the anode and a reduction reaction occurs;

A cation exchange membrane positioned between the anode and the cathode and allowing the ammonium ions to pass therethrough, and

A power supply device connected to the anode and the cathode to supply electrical energy

Ammonia recovery device comprising a.
In claim 1,

The ammonium ions are converted to ammonia, and ammonia recovery apparatus in which gaseous ammonia is recovered.
In claim 2,

The ammonium ions react with the hydroxide ions generated between the cathode and the cation exchange membrane to be concentrated into liquid ammonia.
In claim 3,

The concentrated liquid ammonia is recovered as gaseous ammonia by air or oxygen supplied to the cathode.
In claim 4,

The hydroxide ion is an ammonia recovery device that is generated by the reduction reaction of oxygen or the reduction reaction of water in the reduction electrode.
In claim 4,

The wastewater includes an organic material, and the organic material is decomposed by an oxidation reaction at the anode.
In claim 1,

Ammonia recovery device further comprising a catalyst located on the cathode.
In claim 1,

Ammonia recovery device for controlling the movement speed of ammonium ions by adjusting the voltage applied to the power supply.
In claim 1,

Ammonia recovery device for controlling the concentration of the recovered ammonia by adjusting the flow rate of air or oxygen supplied to the cathode.
Putting wastewater containing ammonia or ammonium ions in a reactor;

Oxidation reaction occurs in the oxidation electrode connected to the reaction tank;

a step in which a reduction reaction occurs in the anode opposite to the anode;

The step of passing the ammonium ion in the cation exchange membrane located between the anode and the cathode, and

The step of supplying electrical energy by a power supply connected to the anode and the cathode

Ammonia recovery method comprising a.
In claim 10,

The ammonium ion is converted to ammonia, and ammonia in a gaseous state is recovered.
In claim 11,

The ammonium ion reacts with hydroxide ions generated between the cathode and the cation exchange membrane and is concentrated to liquid ammonia.
In claim 12,

The concentrated liquid ammonia is recovered as gaseous ammonia by oxygen supplied to the cathode.
In claim 13,

The method for recovering ammonia is that the hydroxide ions are generated by a reduction reaction of oxygen or a reduction reaction of water in the reduction electrode.
In claim 13,

The wastewater includes an organic material, and the organic material is decomposed by an oxidation reaction at the anode.
In claim 10,

Ammonia recovery method for inducing the reduction reaction in the catalyst located on the reduction electrode.
In claim 10,

Ammonia recovery method for controlling the movement speed of ammonium ions by adjusting the voltage applied to the power supply.
In claim 10,

Ammonia recovery method for controlling the concentration of the recovered ammonia by adjusting the flow rate of oxygen supplied to the cathode.
a reactor containing wastewater containing ammonia or ammonium ions;

an anode connected to the reaction tank, where an oxidation reaction occurs,

a reduction electrode facing the anode and a reduction reaction occurs;

A cation exchange membrane positioned between the anode and the cathode and allowing the ammonium ions to pass therethrough, and

A power supply device connected to the anode and the cathode to supply electrical energy

An electrochemical device for an ammonia recovery device comprising a.
In paragraph 19,

An electrochemical device for an ammonia recovery device further comprising a catalyst positioned on the cathode.