KR101312086B1 - Method for collecting alloy-metal from MEA - Google Patents

Abstract

The present invention relates to a method for recovering platinum (Pt), cobalt (Co) and palladium (Pd), in particular an electrode containing a platinum / cobalt alloy and a platinum / palladium alloy from waste MEA (Membrane Electrode Assembly) of a fuel cell. After separating through a solvent and an ultrasonic wave, and selectively separating platinum, cobalt and palladium using an acid treatment and a reducing agent in the electrode containing platinum, thereby providing a method for recovering the entire valuable metal used in the fuel cell.

Description

Method for collecting alloy-metal from MEA

The present invention relates to a method for recovering platinum (Pt), cobalt (Co) and palladium (Pd), in particular an electrode containing a platinum / cobalt alloy and a platinum / palladium alloy from waste MEA (Membrane Electrode Assembly) of a fuel cell. After separating through a solvent and ultrasonic waves, and selectively separating platinum, cobalt and palladium using an acid treatment and a reducing agent in the electrode containing platinum, to recover the entire valuable metals used in the fuel cell.

As a technique used in the conventional MEA, a method using a single catalyst of platinum or alloying cobalt, palladium, ruthenium, iridium and the like for reducing the high cost of platinum has been developed and used.

However, since the platinum and other metals used in the technique also have limited use in limited resources, there is a continuing need for a recovery method for these metals.

However, the recovery and separation techniques used in the past are limited to the separation and recovery of platinum, and the following techniques are disclosed, for example.

[Patent Document 1: Publication No. 1997-0074955 (Published Dec. 10, 1997)]

According to the technique of this document, first, waste scrap is used as a starting material in order to recover platinum, and this is dissolved in aqua regia to prepare a chloroplatinic acid solution containing impurities, followed by addition of a neutralizing agent of NaOH or KOH to the pH of the solution. A secondary neutralization step of adjusting the pH value of the solution to 9.5-10.5 by filtering a primary neutralization step of adjusting the value to 5.5-7.0, insoluble impurities precipitated in the primary neutralization step, and adding a neutralizing agent to the primary filtrate of chloroplatinic acid. And, filtering the insoluble impurities precipitated in the secondary neutralization step, adding hydrochloric acid to the secondary filtrate from which the insoluble impurities are removed, and adding ammonium chloride to the solution thus treated to convert platinum to ammonium chloroplatinum chloride. And a step of vigorously heating ammonium platinum chloride to obtain sponge platinum.

However, when the MEA scrap for fuel cell is reduced through the process described in the above document, it is easy to separate the platinum and trace impurities (less than 0.5%) of the MEA, for example, an alloy containing 0.5% or more impurities. There is a problem in that the purity of the platinum and the valuable metals is impaired or the number of processes is increased, and the recovery rate is low.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and comprehensively controls acid treatment, especially pH control after separation of a catalyst using a solvent, separation of Nafion, pretreatment time, substitution with water, and ultrasonication. By doing so, it is possible to selectively recover platinum, cobalt and palladium, and to increase separation efficiency and recovery rate.

In addition, in order to increase the separation efficiency and recovery rate of the alloy in the MEA, there is a need for a method of removing Nafion and catalyst through pretreatment of the existing aqua regia process and a more convenient and faster manufacturing method to increase the separation efficiency of valuable metals of the catalyst thus obtained. According to the present invention, the Nafion of MEA and the catalyst are separated through an organic solvent before the conventional aqua resolution process, and then the organic solvent is removed through a washing process with pure water, and the catalyst is dispersed by ultrasonic waves, After cobalt (Co) was removed through the widened alloy catalyst and the acid treatment reaction, all of the platinum and palladium remaining in the MEA were recovered through the reaction of aqua regia.

Therefore, the method for recovering alloy in MEA according to the present invention is to separate valuable metals with high recovery rate in a short reaction period by separating Nafion and alloy catalyst in MEA using organic solvent and improving dispersibility using ultrasonic waves. And recoverable.

In the method of recovering the alloy of MEA according to the present invention, adding an organic solvent to the MEA, adding pure water to the MEA to which the organic solvent is added, separating the alloy catalyst and the nifion, and dispersing the separated alloy catalyst using ultrasonic waves. Dispersing cobalt by adding a dispersed alloy catalyst to an acid, filtering a solution in which cobalt is dissolved, and then preparing and recovering cobalt hydroxide by adding caustic soda. Preparing a chloroplatinic acid solution by dissolving the solution, adding hydrochloric acid to the chloroplatinic acid solution, concentrating to remove nitric acid, and adding a saturated ammonium chloride solution to the nitric acid-free solution to form ammonium chlorochloride. Filtering and separating the solution containing ammonium platinum salt, and recovering platinum by calcining the separated ammonium chloroplatinate salt, chloride Precipitating impurities using ammonia salt solution separated by ammonium salt, removing the precipitated impurities and preparing the ammonium palladium chloride salt using hydrochloric acid and then filtering the filtered solution, and filtered palladium chloride A method for recovering an alloy of MEA is provided that consists of calcining an ammonium salt to recover palladium.

According to the method of the present invention, it is possible to separate and recover an alloy having high alloy recovery and excellent purity.

1 is a flow chart showing the flow of the valuable metal recovery in the MEA according to the acid treatment and pH according to the present invention.

Hereinafter, the content of the present invention will be described in detail.

In order to achieve the above technical problem, the present invention, first, waste MEA in an organic solvent, for example, methanol (methanol), ethanol (ethanol), propanol (iso-propanol), butanol ( Soak in butanol, pentanol, hexanol, heptanol, heptanol, acetone, and tetrahydrofuran for 0.1 to 10 minutes. (If less than 0.1 minutes, Nafion and the alloy catalyst is not completely separated, and if more than 10 minutes, the alloy catalyst is dispersed in the organic solvent, the filter is not filtered, causing loss.)

The MEA soaked in the organic solvent is immersed in pure water to facilitate separation of the alloy catalyst and Nafion.

After removing the separated separator and filtering the paper filter paper, using the ultrasonic wave to increase the dispersibility of the filtered alloy catalyst in pure water, the frequency is preferably maintained at 50 ~ 100MHz. (50MHz or less has no effect on dispersibility, and above 100MHz, high temperature occurs and aggregation occurs.)

The dispersed alloy catalyst is then dissolved in acid (hydrochloric acid, nitric acid, or sulfuric acid). At this time, the dissolution temperature is 80 ℃ or more, the solution in which the cobalt dissolved is filtered and separated from the alloy catalyst. (Cobalt is not completely dissolved below 80 ° C.)

And 10-90 degreeC caustic soda is added to the filtered solution, and cobalt hydroxide is formed. (Solution below 10 ° C is slow in reactivity to increase the content of impurities, and the yield is also low. If it is above 90 ° C, the solution precipitates and the reactivity with cobalt becomes low, resulting in high impurity content.)

The separated alloy catalyst is dissolved in aqua regia (nitric acid: hydrochloric acid ratio 1: 3). At this time, the dissolution temperature is 80 ℃ or more (platinum is not completely dissolved at 80 ℃ or less). Heat it until NOx gas is generated while adding hydrochloric acid to remove nitric acid. (If the nitrate group is not removed, the yield will be lower when forming salt, which is a post process.)

The carbon catalyst is removed by filtering the solution from which the nitrate groups have been removed. A saturated ammonium chloride solution was added to the filtrate to form a ammonium chloroplatinate salt. (Saturated solutions below 10 ° C have a low reactivity, resulting in high impurity content, and low yields. Above 90 ° C, saturated solutions precipitate with ammonium chloride, resulting in low reactivity with platinum, resulting in high impurity content.)

After filtering the separated ammonium chloroplatinum salt, the residue is calcined at 700 ~ 1000 ℃ to reduce to platinum (reduction occurs only when the baking temperature is below 700 ℃, platinum is volatilized above 1000 ℃). The remaining filtrate is recovered from palladium after measuring ICP to determine whether platinum is present. (When platinum remains, the solution is dried, calcined, and repeated after aqua regia treatment.)

In the process of recovering palladium, a precipitate is first formed by adjusting pH using ammonia water. (At this time, the pH is maintained at 8. The purity is lowered because the formation of impurities is less than pH 8, and the loss of recovery occurs because the amount of liquid is increased when the pH is above 8).

The precipitated impurities are removed by filtration, and pH is adjusted using hydrochloric acid in the cleared supernatant to form ammonium palladium chloride salt. (pH is preferably adjusted to 1 or less. At pH 1 or higher, salt formation is low and recovery is low.)

The precipitated palladium salt is filtered and calcined in an inert gas atmosphere (hydrogen, argon, nitrogen) to recover palladium. (At this time, the temperature conditions are 300 ° C. or lower. Oxidation proceeds at 300 ° C. or higher.)

Hereinafter, the present invention will be described in more detail.

In the manufacturing method of increasing the recovery rate of high purity platinum, cobalt, and palladium according to the present invention, in order to maximize the separation of Nafion and the alloy catalyst to increase the recovery rate, the organic solvent is removed under pure water treatment after the organic solvent is carried out according to the above conditions. And maximize separation efficiency.

This uses the property of Nafion having hydrophobicity, and it reduces the bonding of the Nafion and the alloy catalyst through the organic solvent, and can be efficiently minimized using pure water to minimize the loss and at the same time shorten the process.

The separated alloy catalyst is dissolved and separated from the cobalt through a reaction with an acid, and the remaining platinum / palladium catalyst is reacted with aqua regia to dissolve.

At this time, the reaction between the solid phase and the liquid phase can increase the reactivity by widening the surface area of the solid phase using ultrasonic waves.

In addition, after removing the nitrate after filtration of the solution, it is reacted with a saturated ammonium chloride saturated aqueous solution, which removes the nitrate to increase the reactivity of ammonium chloride and chloroplatinic acid, the ammonium chloride in the hot state through the difference in reactivity Platinum of high purity can be obtained, and palladium is recovered from the separated filtrate through pH adjustment to separate three substances (platinum, cobalt, palladium), and the yield is also characterized by having an effect of increasing.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

However, the embodiments described below are for illustrating the present invention, and the content of the present invention is not limited to the following examples.

Figure 1 shows a manufacturing method according to the invention as a process example, showing a flow chart of the alloy recovery process of the MEA according to the method.

First, the fuel cell MEA scrap is placed in a 10 Lt beaker, ethanol is placed in the beaker filled with scrap, and soaked for 5 minutes so that the MEA does not come into contact with air (step S1). When ethanol and MEA meet, the electrode and Nafion are separated due to swelling of Nafion (step S2). Pour ethane and pour distilled water. Distilled water is used to remove all ethanol remaining in the MEA. Finally, after filling with distilled water, the ultrasonic device disperses the alloy remaining in the electrode at 80 MHz (step S3). The dispersed alloy catalyst was dissolved in cobalt at 80 ° C using hydrochloric acid (step S4). Caustic soda is added to the separated cobalt chloride solution to prepare and recover cobalt hydroxide (step S5). The alloy catalyst from which cobalt was removed is dissolved in aqua regia (step S6). The dissolved solution is filtered and concentrated to remove all nitric acid. The solution under hydrochloric acid was added to a saturated solution of ammonium chloride at 85 ° C. to prepare ammonium chloroplatinate salt, followed by filtration (step S7). The filtered platinum salt is calcined at 800 ° C. to recover platinum (steps S8 and S9). The filtered filtrate is adjusted to pH 8 using ammonia to precipitate impurities (step S10). The impurities are removed by refiltration and the remaining filtrate is adjusted to pH 1 with hydrochloric acid, and then ammonium palladium chloride salt is prepared and filtered (step S11). The filtered palladium salt is calcined in a 290 ° C hydrogen gas atmosphere to recover palladium (steps S12 and S13).

Comparative Example 1

First, put the MEA scrap for fuel cell into a 10Lt beaker. Place ethanol in a scrap filled beaker and let the MEA stay in contact with air for 5 minutes. When ethanol meets MEA, the electrode and Nafion are separated by the swelling of Nafion. Pour off ethanol and pour distilled water. Distilled water is used to remove all ethanol remaining in the MEA. Finally, after distilled water is filled, the ultrasonic device disperses the remaining alloy in the electrode at 80 MHz. The dispersed alloy catalyst was dissolved in cobalt at 60 ° C using hydrochloric acid. Caustic soda is added to the separated cobalt chloride solution to prepare and recover cobalt hydroxide. Cobalt-free alloy catalyst is dissolved in aqua regia. The dissolved solution is filtered and concentrated to remove all nitric acid. The solution under hydrochloric acid was added to a saturated solution of ammonium chloride at 85 ° C. to prepare ammonium chloroplatinate salt, and then filtered. The filtered platinum salt is calcined at 800 ° C. to recover platinum. The filtered filtrate is adjusted to pH 8 with ammonia to precipitate impurities. The impurities are removed by refiltration and the remaining filtrate is adjusted to pH 1 using hydrochloric acid, and then ammonium palladium chloride salt is prepared and filtered. The filtered palladium salt is calcined in a 290 ° C. hydrogen gas atmosphere to recover palladium.

Comparative Example 2

First, put the MEA scrap for fuel cell into a 10Lt beaker. Place ethanol in a scrap filled beaker and let the MEA stay in contact with air for 5 minutes. When ethanol meets MEA, the electrode and Nafion are separated by the swelling of Nafion. Pour off ethanol and pour distilled water. Distilled water is used to remove all ethanol remaining in the MEA. Finally, after distilled water is filled, the ultrasonic device disperses the remaining alloy in the electrode at 80 MHz. The dispersed alloy catalyst is dissolved in cobalt at 80 ° C. using hydrochloric acid. Caustic soda is added to the separated cobalt chloride solution to prepare and recover cobalt hydroxide. Cobalt-free alloy catalyst is dissolved in aqua regia. The dissolved solution is filtered and concentrated to remove all nitric acid. The solution under hydrochloric acid was added to a saturated ammonium chloride solution at 85 ° C. to prepare ammonium chloroplatinate salt, followed by filtration. The filtered platinum salt is calcined at 800 ° C. to recover platinum. The filtered filtrate is adjusted to pH 6 with ammonia to precipitate impurities. The impurities are removed by refiltration and the remaining filtrate is adjusted to pH 1 using hydrochloric acid, and then ammonium palladium chloride salt is prepared and filtered. The filtered palladium salt is calcined in a 290 ° C. hydrogen gas atmosphere to recover palladium.

[Comparative Example 3]

First, put the MEA scrap for fuel cell into a 10Lt beaker. Place ethanol in a scrap filled beaker and let the MEA stay in contact with air for 5 minutes. When ethanol meets MEA, the electrode and Nafion are separated by the swelling of Nafion. Pour off ethanol and pour distilled water. Distilled water is used to remove all ethanol remaining in the MEA. Finally, after distilled water is filled, the ultrasonic device disperses the remaining alloy in the electrode at 80 MHz. The dispersed alloy catalyst is dissolved in cobalt at 80 ° C. using hydrochloric acid. Caustic soda is added to the separated cobalt chloride solution to prepare and recover cobalt hydroxide. Cobalt-free alloy catalyst is dissolved in aqua regia. The dissolved solution is filtered and concentrated to remove all nitric acid. The solution under hydrochloric acid was added to a saturated ammonium chloride solution at 85 ° C. to prepare ammonium chloroplatinate salt, followed by filtration. The filtered platinum salt is calcined at 800 ° C. to recover platinum. The filtered filtrate is adjusted to pH 8 with ammonia to precipitate impurities. The impurities are removed by refiltration and the remaining filtrate is adjusted to pH 3 with hydrochloric acid, and then ammonium palladium chloride salt is prepared and filtered. The filtered palladium salt is calcined in a 290 ° C. hydrogen gas atmosphere to recover palladium.

[Comparative Example 4]

First, put the MEA scrap for fuel cell into a 10Lt beaker. Place ethanol in a scrap filled beaker and let the MEA stay in contact with air for 5 minutes. When ethanol meets MEA, the electrode and Nafion are separated by the swelling of Nafion. Pour off ethanol and pour distilled water. Distilled water is used to remove all ethanol remaining in the MEA. Finally, after distilled water is filled, the ultrasonic device disperses the remaining alloy in the electrode at 80 MHz. The dispersed alloy catalyst is dissolved in cobalt at 80 ° C. using hydrochloric acid. Caustic soda is added to the separated cobalt chloride solution to prepare and recover cobalt hydroxide. Cobalt-free alloy catalyst is dissolved in aqua regia. The dissolved solution is filtered and concentrated to remove all nitric acid. The solution under hydrochloric acid was added with a saturated solution of ammonium chloride at 10 ° C. to prepare ammonium chloroplatinate salt, followed by filtration. The filtered platinum salt is calcined at 800 ° C. to recover platinum. The filtered filtrate is adjusted to pH 8 with ammonia to precipitate impurities. The impurities are removed by refiltration and the remaining filtrate is adjusted to pH 1 using hydrochloric acid, and then ammonium palladium chloride salt is prepared and filtered. The filtered palladium salt is calcined in a 290 ° C. hydrogen gas atmosphere to recover palladium.

The summary results according to the above examples and comparative examples are summarized in the following table.

cobalt
Melting temperature cobalt
yield Ammonium chloride
Temperature Plasticity
Temperature platinum
yield Plasticity
Temperature ammonia
pH Hydrochloric acid
pH yield water
Example 1
80 ℃
99%
85 ℃
800 ℃
99%
800 ℃
8
One
99%
99.99%
Comparative Example 1
60 ° C
76%
85 ℃
800 ℃
99%
800 ℃
8
One
98%
99%
Comparative Example 2
80 ℃
99%
85 ℃
800 ℃
99%
800 ℃
6
One
85%
98%
Comparative Example 3
80 ℃
99%
85 ℃
800 ℃
95%
800 ℃
8
3
88%
99.99%
Comparative Example 4
80 ℃
99%
10 ℃
800 ℃
96%
1000 ℃
8
One
99%
99.99%

Or more, with reference to the accompanying drawings and the table for the preferred embodiment of the present invention was described in detail.

However, the above-described embodiment is only an example for explaining the present invention, and is not used to limit the scope or limit of the meaning of the present invention, and in the technical field to which the present invention belongs within the scope of the claims. Of course, any person having ordinary skill in the art can make various modifications.

Claims (11)

The alloy recovery method of the MEA (Membrane Electrode Assembly) for fuel cells,
Adding an organic solvent to the MEA;
Separating pure water from the alloy catalyst and the nifion by adding pure water to the MEA to which the organic solvent is added;
Dispersing the separated alloy catalyst using ultrasonic waves;
Dissolving cobalt by adding the dispersed alloy catalyst to an acid;
Filtering the solution in which the cobalt is dissolved, and then preparing and recovering cobalt hydroxide by adding caustic soda;
Preparing a chloroplatinic acid solution by dissolving the cobalt-free alloy catalyst in aqua regia;
Adding hydrochloric acid to the chloroplatinic acid solution and concentrating to remove nitric acid;
Adding a saturated ammonium chloride solution to the nitric acid-free solution to form ammonium chloroplatinate salt;
Filtering and separating the solution containing the ammonium platinum chloride salt and calcining the separated ammonium platinum chloride salt to recover platinum;
Precipitating impurities using ammonia in the solution from which the ammonium platinum chloride salt is separated;
Removing the precipitated impurities and preparing the ammonium palladium chloride salt using hydrochloric acid and then filtering the remaining solution; And
The filtered ammonium palladium chloride salt using an inert gas of hydrogen, argon, nitrogen, any one of the steps of firing at less than 300 ℃ recovering the alloy of the MEA, characterized in that consisting of. The method of claim 1,
The organic solvent is methanol, ethanol, propanol, iso-propanol, butanol, butanol, pentanol, hexanol, heptanol (heptanol), acetone (acetone), tetrahydrofuran (tetrahydrofurane) any one selected from the alloy recovery method of MEA. The method of claim 1,
Dispersing the ultrasonic alloy in the separated alloy catalyst using an ultrasonic wave of the frequency of 50 ~ 100MHz, MEA alloy recovery method. The method of claim 1,
Dissolving cobalt by dispersing the dispersed alloy catalyst in an acid selects any one of hydrochloric acid, nitric acid, or sulfuric acid, and the dissolution temperature is 80 ° C or more. The method of claim 1,
Filtering the solution in which the cobalt is dissolved, and then recovering the cobalt hydroxide by adding caustic soda, adding caustic soda at 10 to 90 ° C. The method of claim 1,
Dissolving the solution into the aqua regia to prepare a chloroplatinic acid solution is an alloy recovery method of MEA, characterized in that the aqua regia (nitric acid, hydrochloric acid ratio 1: 3) or more. The method of claim 1,
The method for recovering the alloy of MEA, characterized in that the ammonium chloroplatinate salt is added by adding a saturated ammonium chloride solution to the nitric acid removed solution using a saturated ammonium chloride solution of 10 ~ 90 ℃. The method of claim 1,
The firing temperature of the step of recovering the platinum by calcining the separated ammonium chloroplatinate salt is an alloy recovery method of MEA, characterized in that 700 ~ 1000 ℃. The method of claim 1,
Precipitating impurities using the ammonia solution of the ammonium platinum chloride salt by using ammonia, the method for recovering the alloy of MEA, characterized in that the ammonia is adjusted to pH 8. The method of claim 1,
Removing the precipitated impurities and preparing the ammonium palladium chloride salt using hydrochloric acid, followed by filtering, adjusting the hydrochloric acid to pH 1, wherein the alloy is recovered. delete

Images