JPH01111825A - Method for recovering palladium from palladium-containing liquid - Google Patents

Abstract

PURPOSE:To recover Pd at a high yield by adjusting the pH of a liquid contg. Pd and other heavy metals to a specific value, then passing the liquid through a chelate type ion exchange resin of a pyridine system to selectively adsorb the Pd thereon, then eluting the Pd by an alkaline liquid. CONSTITUTION:Industrial waste water or the like in which the Pd and the heavy metals such as Fe, Ni, Cu, Zn, Sn, and Pb are dissolved and incorporated is adjusted to <=9pH. This liquid is then passed in a column in which the chelate type ion exchange resin of the pyridine system is packed to adsorb the Pd in the liquid selectively on the ion exchange resin. The other heavy metals are passed through the column without being adsorbed on the ion exchange resin. After this ion exchange resin is rinsed, aq. ammonia, ammonium salt such as (NH4)2SO4 or NH4NO3 or aq. soln. of alkali cyanide such as NaCN or KCN. is passed through the resin to elute the Pd adsorbed thereon. The Pd is thus recovered at the high yield.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention efficiently recovers palladium present as ions in a solution by adsorbing it onto an ion exchange resin and eluating the adsorbed palladium with an alkaline solution. Regarding the method for.

(Prior art and its problems) As a method for recovering palladium from a liquid containing palladium, hydrazine, sodium borohydride, oxalic acid, metal powder (/l powder, Zn powder, Mg powder, Cu powder, etc.) are used.
Common methods include a method of recovering by adding a reducing agent such as, an electrodeposition method, and a method of forming an insoluble complex salt. However, with these methods, several ppm of palladium remains in the solution without being recovered, and if the palladium concentration in the palladium-containing liquid is dilute, a large proportion of palladium remains in the solution without being recovered. , there is a problem that the recovery rate decreases.

In addition to palladium, palladium-containing liquids often contain large amounts of heavy metals such as iron, nickel, copper, zinc, lead, and tin, and these heavy metals are removed during palladium recovery. There are problems in that the palladium is mixed with palladium, making it impossible to obtain a high-quality product, and the subsequent purification of palladium is time-consuming.

To solve the former problem, a method is known in which palladium is concentrated and recovered using an ion exchange resin, but when recovering palladium from a resin that has adsorbed palladium, it is not possible to elute palladium from the resin. Palladium must be recovered after first incinerating the expensive resin, or even if palladium can be eluted, the elution rate is low and the recovery rate decreases, or the resin cannot be reused. There is a problem.

Furthermore, when a palladium-containing liquid containing many impurities mentioned above is used, palladium and these heavy metals are adsorbed at the same time, which not only reduces the amount of palladium adsorbed per ion exchange resin and increases recovery costs, but also increases the recovery cost. There are also problems such as heavy metals mixed into palladium, which lowers the quality of the resulting palladium.

(Objective of the Invention) The present invention has been made in view of the above problems, and aims to provide a method for recovering high-quality palladium that has a high recovery rate (i.e., allows reuse of ion exchange resin). It is something to do.

(Means for Solving the Problems) As described above, the method for recovering palladium from a palladium-containing liquid according to the present invention involves adjusting the palladium-containing liquid to a pH of 9 or less and passing it through a pyridine-based chelating ion exchange resin. The method is characterized in that the palladium is adsorbed by the adsorbent, and then the adsorbed palladium is eluted with an alkaline eluent to recover the palladium.

(Function) The function of the present invention will be described below. It is desirable to adjust the pH of the palladium-containing solution to 9 or less. pH
This is because if the value is higher than 9, the amount of palladium adsorbed to the ion exchange resin may decrease or the amount of palladium may not be adsorbed at all.

Palladium-containing liquids include palladium-containing scrap dissolved in acid, palladium-containing waste liquid discharged from processes that use palladium, and trace amounts of palladium discharged from palladium recovery and purification processes. There are many things such as waste liquid.

Although palladium-containing liquids containing large amounts of heavy metals such as iron, nickel, lead, zinc, and tin as impurities are suitable for the present invention, the present invention can also be applied to liquids that do not contain many impurities.

The palladium concentration in the palladium-containing liquid is 50g/
j! Although the following range is preferable, the present invention can be applied even if it is higher than this, and it can be said to be a preferable method especially when the amount of heavy metals is large (it is difficult to apply the conventional wet method).

When a palladium-containing liquid is passed through a pyridine-based chelating ion exchange resin, palladium is selectively adsorbed, and most of the heavy metals mentioned above are not adsorbed and flow out.

This process separates palladium and impurities,
High quality palladium can be obtained through the process described later.

Although there are many pyridine-based chelating ion exchange resins, Sumikire CR-2 (trade name) was used in the examples.

Further, the adsorption operation is preferably performed by a column method, but may also be performed by a batch method.

The palladium adsorbed on the resin is eluted with an alkaline eluent, but a case where the palladium adsorbed on the resin is a chloro complex (chloropalladic acid) will be described below.

When a palladium-containing liquid is passed through a resin, the palladium (chloropalladate) in the liquid binds to and is adsorbed to the sensitive groups of the resin at a certain distribution ratio.

When aqueous ammonia is used as an alkaline eluent, the palladium ligand ((1-)
is substituted with ammonia (NH3) and becomes an ammine complex of palladium.The distribution ratio between the resin and palladium changes, and the properties of the resin itself also change depending on the pH. Therefore, the palladium adsorbed on the resin becomes an ammine complex of palladium. eluted. When an eluent containing alkali cyanide is used, similarly adsorbed palladium is eluted as a palladium cyano complex.

Examples of alkaline eluents include aqueous ammonia, ammonium salts (ammonium sulfate, ammonium nitrate, etc.),
It is sufficient if it contains a compound capable of supplying a ligand such as alkali cyanide (sodium cyanide, potassium cyanide, etc.), and may also include thiocyanate, thiosulfate, etc., and any one of these may be used. If it contains the above, palladium can be eluted.

The eluent was made alkaline because an alkaline eluent can elute palladium from the resin more easily than an acidic eluent. Alkali hydroxide (sodium hydroxide,
Potassium hydroxide, etc.) may be added.

Further, the resin after palladium has been eluted can be used again after undergoing steps such as water washing and regeneration, which is advantageous.

When using resin in a column, adsorption (liquid passage),
In operations such as elution and regeneration, 5V is preferably 0.5 to 10, and in operations such as washing with water, 5V is preferably 5 to 30.

The obtained palladium concentrate contains almost no heavy metals, so when palladium is obtained from it, metallic palladium with few impurities is obtained, and its quality is approximately 80% or more. As a method for obtaining palladium, the above-mentioned method using a reducing agent, electrodeposition method, insoluble complex salt formation method, etc. are commonly used, but there are many other methods. Furthermore, in order to obtain higher quality palladium, the process of the present invention may be repeated multiple times, or palladium may be obtained after further removal of impurities through separation operations such as membrane separation, solvent extraction, RO or UF. .

(Example 1) As shown in the drawing, a palladium-containing liquid obtained by dissolving Pd-containing scrap in aqua regia (Pd: 0.08 g/1
2. Fe: 1.5g/j! , N i :
0.1g/l.

Pb: 0.20g/j! SCu: 1.2 g/
j! , pH=0.9) was passed through 0.5 liter of pyridine-based chelating ion exchange resin (Sumichelate CR-2) packed in a column at 5V=2. 50 liters J, 100 liters J, 1
When the 50th liter and 200th liter of passing liquid were analyzed, palladium was adsorbed as shown in the table, and heavy metals other than palladium passed through without being adsorbed.

Table Analytical results of resin passing liquid: NO = not detectable, resin after palladium adsorption, 5V = 3 liters of pure water
After washing with water at 20°C, elution was carried out at 5V=2 with 2.5 liters of 5% ammonia water, and then eluted with 2.5 liters of washing water at 5V=2.
Washing was carried out at V=5 to obtain 2.5 liters of eluent containing palladium and 2.5 liters of washing water containing palladium. When both liquids containing palladium were mixed to make 5 liters and analyzed, Pd: 3.19 g/f, Fe: 2 m
g/f, Ni: 1 mg/l.

Cu: 2■/l, Pb: 1K/l or less.

After adjusting this solution to pH=8 with dilute sulfuric acid, 20 g of sodium borohydride was added to reduce the palladium, filtered, washed, and dried to obtain a product with a dry weight of 16.07 g and a grade of 99.2%. of metallic palladium was obtained. The yield from charging the palladium-containing liquid to recovering metal palladium was as high as 99.6% based on the pure amount of palladium.

(Conventional Example 1) A palladium-containing liquid obtained by dissolving Pd-containing scrap in aqua regia (pa: 0.08 g/f, Fe: 1.
5g/lSNi: 0.70g/LPb
: 0.20 g/l, Cu: 1.2 g/l, pH=
1.3) Add 10% sodium hydroxide to 1 liter to adjust the pH to 8.0, then add 5g of sodium borohydride to reduce palladium, filter, wash, and dry. Metallic palladium with a weight of 0.75 g and a grade of 10.1% was obtained. The yield from injecting the palladium-containing liquid to recovering metal palladium was 94.7% based on the pure amount of palladium, lower than in Example 1, and the quality was also significantly low at 10.1%. .

(Example 2) As shown in the drawings < P d : 3. OOg/ (1,F
e: 0.82g/l, Cu: 0.95g/
A hydrochloric acid acidic palladium-containing solution (p) (=3) containing 0.30 g/f of Zn was added to 0.5 liter of a pyridine-based chelating ion exchange resin packed in a column at 5V=1.
The liquid was passed through. Palladium was adsorbed, and heavy metals other than palladium passed through without being adsorbed. 9. After passing 1 liter of liquid, the palladium concentration in the liquid passing through was 2■/
2, so I stopped passing the liquid and turned it to 5V with 5 liters of pure water.
= 10 and washed with water. When the amount of palladium adsorbed on the resin was calculated, it was found to be extremely high at 54.6 g per liter of resin.

After washing, the resin was washed with 1.5 liters of 5% NaOH water.
Elute at V=1 and add 1.5 liters of washing water 5V=5
1.5 liters of eluent containing palladium and 1.5 liters of washing water containing palladium were obtained. Both solutions containing palladium were mixed to form a palladium concentrate.

Next, the resin after palladium elution was regenerated by passing 5% H, 3041 liters of 5V-2, and pure water 2.
5 liters was washed with 5V-5, and the above-mentioned solution was passed through the solution until the palladium concentration in the passing solution was in the range of 1 to 10 mg/42.

In the above method, the operation of palladium adsorption - water washing - palladium elution - water washing - resin regeneration - water washing = (palladium adsorption) was repeated nine times. During the process, the amount of palladium adsorbed per liter of resin was determined from the amount of palladium-containing liquid passed through, and it was found to be between 52 and 56 g, which was almost unchanged.

In a total of 10 operations, 89.2 liters of palladium-containing liquid was treated and a palladium concentrate (P d : 8.91 g/
30 liters was obtained.

This concentrated solution was adjusted to pH=10 with dilute sulfuric acid, and then electrolyzed at a current density of 3 A/dm'' using a platinum-plated titanium plate as the anode and a stainless steel plate as the cathode to deposit palladium.

After palladium electrodeposition, 269.9% of palladium with a grade of 99.4% was deposited from the cathode. Og was obtained. The yield from the time when the palladium-containing liquid was introduced until the metal palladium was recovered was as high as 99.92% based on the pure amount of palladium.

(Conventional example 2) p t : 3.00 g/l, Fe : 0.82 g/f
, Cu: 0.95 g/l, Zn: 0.30
g/I! An acidic palladium-containing solution containing hydrochloric acid (pH=
3) packed in a column using a non-pyridine-based weakly basic ion exchange resin (Diaion 5AIO-A (trade name))
The solution was passed through 0.5 liters at 5V=1. Heavy metals other than palladium were also adsorbed along with palladium, and when 4.6 liters of liquid was passed through, the palladium concentration in the passing liquid became 2 / i, so the flow was stopped and 5 liters of pure water was added to 5V = 1.
Washed with water at 0. When the amount of palladium adsorbed on the resin was calculated, it was found to be 27.6 g per liter of resin, which was lower than in Example 2.

The resin after washing was eluted with 1.5 liters of 5% ammonia water at 5V=1, and then eluted with 1.5 liters of washing water at 5V=1.
When the two solutions were mixed, 3.0 liters of a solution in which a portion of palladium and heavy metals other than palladium were eluted was obtained.

The resin after palladium elution was then heated at 5% Hz 3041
It is regenerated by passing the liquid at 5V = 2, and pure water 2
．． 5 liters was washed at 5V=5, and the above-mentioned solution was passed through the solution until the palladium concentration in the passing solution was in the range of 1 to 10 .mu./2.

In the above method, the operation of palladium adsorption -> water washing - palladium elution - water washing - resin regeneration - water washing = (palladium adsorption) was repeated 9 times. During the course of the process, the amount of palladium adsorbed per liter of resin was determined from the amount of palladium-containing liquid passed through, and the amount was initially 27.6 g, but by the 10th time it was 23.2 g, a decrease of about 15%.

In a total of 10 operations, 41.6 liters of palladium-containing liquid was treated and palladium concentrated liquid (P d : 4.03 g
/2, Fe: 0.16g/1-1Cu: L3
g/l, Zn: 0.30 g/j, 30 liters was obtained.

This concentrated solution was adjusted to pH=10 with dilute sulfuric acid, and then electrolyzed at a current density of 3 A/dm'' using a platinum-plated titanium plate as the anode and a stainless steel plate as the cathode to deposit palladium.

After palladium electrodeposition, 120.1 g of pure palladium with a grade of 78.5% was obtained from the cathode, but the grade was low due to the contamination of Cu, Zn, etc. The yield from charging the palladium-containing liquid to recovering metal palladium was 96.2% based on the pure amount of palladium, which was lower than in Example 2.

(Example 3) As shown in the drawings <Pt: 3. OOg/l, F
e: 0.82g/l, Cu: 0.95g/j!
, 0.5 liters of a pyridine-based chelating ion exchange resin packed with a hydrochloric acid acidic palladium-containing solution (p) I = 3) containing 0.30 g/ffi of Zn in a column was charged with 5 V =
The liquid was passed through at step 1. Palladium was adsorbed, and heavy metals other than palladium passed through without being adsorbed. Since the palladium concentration of the passing liquid became 2 / 2, the liquid passage was stopped and 5
It was washed with a little pure water at 5V=10. The resin after washing with water is KCN50g per liter, KOHlog
Elute with 1.5 liters of eluent containing palladium at a rate of 5V=1, further wash with 1.5 liters of washing water at 5V=5, and elute with 1.5 liters of eluent containing palladium and 1.5 liters of washing water containing palladium. I got 5 liters. Both solutions containing palladium were mixed to form a palladium concentrate.

Then, the resin after palladium elution was mixed with 5% 1(,5Oa1
It is regenerated by passing the liquid at 5V = 2, and pure water 2
．． 5 liters was washed with 5V-5, and the palladium concentration in the liquid that passed through the above solution was 1 to 10 mg//! The liquid was passed until it reached the range of .

In the above method, the operation of palladium adsorption - water washing - palladium elution - water washing - resin regeneration - water washing = (palladium adsorption) was repeated nine times.

A palladium concentrate was obtained through a total of 10 operations.

This concentrated solution was adjusted to pH=12 with dilute sulfuric acid, and then electrolyzed at a current density of 3 A/dm'' using a platinum-plated titanium plate as the positive electrode and a stainless steel plate as the cathode to deposit palladium.

High-quality palladium was obtained from the cathode, and the resin could be used many times.

(Effect of the invention) When recovering palladium from a palladium-containing liquid, the present invention selectively adsorbs palladium to a pyridine-based chelating ion exchange resin, elutes palladium with an alkaline eluent, and ion exchanges the palladium. The resin is reused, while high-grade palladium can be recovered.

In the present invention, there are few impurities mixed in the palladium recovered as in the conventional method, high quality is obtained, the resin on which palladium is adsorbed can be easily eluted, and it can be used many times. In addition to this, there are other effects such as significantly improved yields and reduced recovery and purification costs, making it a great contribution to industry in recovering rare metals like palladium.

[Brief explanation of the drawing]

The accompanying drawing is a block flow diagram of palladium recovery illustrating the implementation of the present invention. Applicant Tanaka Kikinzoku Kogyo Co., Ltd.

Claims (2)

[Claims] (1) Prepare a palladium-containing solution to pH 9 or less, pass it through a pyridine-based chelating ion exchange resin to adsorb palladium, and recover palladium by eluting the adsorbed palladium with an alkaline eluent. A method for recovering palladium from a palladium-containing liquid. (2) The method according to claim 1, wherein the alkaline eluent contains at least one of ammonia, an ammonium salt, and an alkali cyanide.