JPS59185770A - Method for recovering nickel from waste chemical nickel plating bath - Google Patents

Abstract

PURPOSE:To reutilize nickel in a waste chemical nickel plating soln. by adjusting the soln. to a prescribed pH with oxalic acid to precipitate complexed nickel ions as nickel oxalate which is simply reduced to nickel. CONSTITUTION:When a chemical nickel plating soln. contg. a hypophosphite as a reducing agent and an org. acid as a complexing agent is aged, the waste soln. is adjusted to 1-3pH with oxalic acid to precipitate complexed nickel ions in the waste soln. as insoluble nickel oxalate. Nickel oxalate contg. little phosphoric acid is recovered by filtration, and it is reduced to metallic nickel by heating in a reducing atmosphere. Thus, nickel is reutilized and an economical effect is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering nickel from aged waste liquid of a chemical nickel plating bath, and relates to a method for recovering nickel from aged waste liquid of a chemical nickel plating bath, which uses hypophosphite as a reducing agent and an organic acid as a complexing agent. This method is characterized by adding oxalic acid to the aged waste liquid, precipitating nickel ions complexed with an organic acid as insoluble nickel oxalate, and recovering the waste.

Conventionally, chemical nickel plating can be used to plate nonconductors such as plastics and ceramics, and it is also used for electronic parts, precision equipment, etc. because it can provide a uniform plating layer with high added value such as corrosion resistance and wear resistance. widely used in The chemical nickel plating bath contains nickel ions, reducing agents, complexing agents, etc. In particular, the reducing agent is said to be essential for reducing nickel ions to nickel, but as nickel precipitates, it oxidizes and its concentration increases. decreases. If the reducing agent is hypophosphite, it will be oxidized to phosphite, so controlling the concentration of hypophosphite ions and nickel ions is essential for effective retention in a chemical nickel plating bath. These are replenished in a timely manner to regenerate the plating solution. However, there is a limit to this replenishment, and as the amount of phosphite ions accumulated in the solution increases, the deposition rate and condition may deteriorate, or the plating solution may age and become unusable after 5 to 6 cycles. In order to reduce the concentration of nickel, phosphorus, COD, etc. to within the discharge standards, the aged waste liquid is treated with various types of waste liquid before being discharged. However, there is still no effective treatment technology for the aged waste liquid from chemical nickel plating baths, and since nickel is a rare metal, it is necessary to recycle it in order to conserve resources, but nickel cannot be recovered from aged waste liquid.
The phosphorus content of recovered nickel is high, making it difficult to recycle it effectively.

For example, methods for recovering nickel from the aged waste liquid of a chemical nickel plating bath consisting of nickel chloride, sodium hypophosphite, and a complexing agent during bath preparation include cathodic electrolysis or an alkaline agent such as sodium hydroxide or sodium carbonate. There is a method in which nickel is added and precipitated as nickel hydroxide, but in the former cathodic electrolysis method, the electrodeposit contains 5 to 15% phosphorus, which has the disadvantage that it cannot be effectively reused as metallic nickel. In the latter method, in which nickel ions are precipitated as nickel hydroxide, nickel ions easily precipitate as hydroxide at pH 8 to 9 when no complexing agent is contained, but in the case of chemical nickel waste liquid containing a complexing agent, nickel ions are precipitated at pH 8 to 9. At pH 9 to 9, almost no hydroxide is produced, and only at high pH values of 10 to 13, hydroxide is produced, and since the hydroxide is in the form of a loose colloid, it is difficult to pass through the mouth. The drawback is that nickel cannot be easily recovered.

Therefore, in order to recover nickel powder with low phosphorus content, calcium chloride and calcium hydroxide are added to the aged waste liquid to form a precipitate of calcium phosphite which is insoluble at around pH 9. One possibility is to lower the pH of the solution to around 4 and recover it as an electrodeposit using cathode electrolysis, but in this method, a large amount of calcium phosphite precipitate contains nickel and a complexing agent, so the discarded arsenic acid A water rinse is required to separate them from the lucium precipitates. Since the cathodic electrolysis method is carried out by adding the oral fluid containing nickel ions to the initial oral fluid, it has the drawbacks of a low nickel ion concentration and difficulty in obtaining a satisfactory electrodeposit. Furthermore, since a large amount of calcium phosphite precipitate to be discarded is washed and passed through the mouth, it is time consuming and uneconomical.

In short, in the method of recovering nickel from nickel plating aging waste liquid, it is important to make the precipitate easier to pass through and to minimize the amount of phosphorus contained in the recovered nickel.

However, in the present invention, in the aged waste liquid of a chemical nickel plating bath that uses hypophosphite as a reducing agent and an organic acid as a complexing agent, an oxalic acid component is added to the waste liquid to adjust the pH to 1 to 3.
When the nickel ions complexed with organic acids in the aged waste liquid are made acidic and precipitated as insoluble nickel oxalate, the nickel oxalate has a low water content and good sedimentation properties, and the amount of contamination with 9 components is small. By passing the waste liquid through the mouth, nickel ions can be easily and quickly recovered as nickel oxalate. In addition, as is well known, nickel oxalate can be used in an atmosphere such as city gas, methane gas, nitrogen gas, or hydrogen gas, or in a vacuum (10 torr or less).
By heating at about 300 to 400°C for 1 hour or more, 90% or more of the nickel is easily reduced as metallic nickel.

The phosphorus content in the metal nickel is 0.1% or less, which is extremely small compared to conventional methods, and can be added to steel materials to improve their quality. In addition, by heating nickel oxalate to 400°C or higher in the atmosphere, it can be made into nickel oxide with a phosphorus content of 0.06% or less, which is widely used by adding it to ceramic materials to improve their quality. It can also be used effectively as a rare metal. Furthermore, recovering nickel as nickel oxalate from the aged waste liquid of chemical nickel plating baths and reusing it as metallic nickel and nickel oxide8 has a very large economic effect on the industry.

Examples of the present invention will be described in detail below.Example 1 Composition of aging solution q = Kke/l/10 f/(J (Ni"
240Off'M'A') Sodium citrate 20
y/1 (10100001 as COD value)p Sodium sulfite 40g/l (5700ppm as P)a
Processing conditions for nickel recovery Addition amount of oxalic acid 6. Tf/l (1.8 of N12+
pH value after addition of (2 times mole) pH2.0 Treatment temperature 50℃, treatment time 24 hoursNickel ion concentration in the sip-filtered solution and phosphorus concentration in the sip-filter (nickel oxalate) in the sip-filtered solution The nickel ion concentration in 43T/β phosphorus concentration in nickel oxalate (CP/N:% of L) is 08% in the state of nickel oxalate/L/1 f.
"U') Approximately 0 when washed with 100rnl of water
．． 1%, approximately 0.05% for 200ml Treatment conditions for Q phosphorus and COD value Calcium chloride dihydrate is added to the above mouth surface (the amount added is C
a/! 'J citric acid (mole ratio) 1.2 times mole, Ca / citric acid (mole ratio) 1.8 times mole total 51 fl/l)
The pH is adjusted to 8, and calcium phosphite, calcium citrate, and calcium oxalate (excess oxalate) are added to settle as a precipitate.

Treatment temperature: 50°C, treatment time: 24 hours α Phosphorus in supernatant, COD value y aooppm, COD value 700 I) 1
)m wastewater standard is COD value 100 ppm,
It is necessary to treat wastewater by diluting it with about 7 to 10 times as much water, adding an oxidizing agent to oxidize the organic matter, or oxidizing the organic matter by anodizing electrolysis.

However, even if these treatments are applied, most of the nickel ions are removed as nickel oxalate by using oxalic acid in baths using citric acid as a complexing agent. For this reason, most of the citric acid does not exist as a complex with nickel ions, so it is easily oxidized.
Non-K property by reacting with a2+ ions +7) It can be removed as calcium citrate, and nickel can be recovered in the aged wastewater of chemical nickel plating baths that use hypophosphite as a reducing agent and citric acid as a complexing agent. was carried out in the manner described above, and slaked lime and calcium salts such as calcium chloride were further added to the mouth surface through which nickel oxalate had been passed.11) H7-1
The solution is made alkaline to 0, and the calcium ions, phosphorous acid, citric acid, and excess oxalic acid are precipitated as insoluble calcium phosphite, calcium citrate, and calcium oxalate, and these are passed through the mouth. Since the concentration of citric acid is greatly reduced on this surface, the COD value can be easily and economically reduced by oxidizing the organic acid using an oxidizing agent or anodizing electrolytic method. be.

Example 2 Composition of aging liquid Nickel chloride 10 f/l (N:L”2400 W
#) Sodium phosphite 4of/l Malic acid 18y/l Succinic acid 16F//l/a Nickel recovery conditions Amount of sulfuric acid added 6.1f//11 (Ni'1/1
, 3 times mo/L/) pH value after addition: pH 2.0 Treatment temperature: 50°C, treatment time: 24 hours Nickel ion concentration in the surface: 59flf//1 P washed with 100rrLl of water per 1g of nickel oxalate /
Ni, value 0.1% Example 3 Composition of aging liquid Nickel chloride 1og/(1(Ni” 2400■/
β) Sodium phosphite 40g/β Sodium acetate 20g/β a Nickel recovery conditions Amount of oxalic acid added 6. tf/l(N:l'1/1.
pH value after addition of 3 times mole) pH 2,.

Treatment temperature 50°C1 Treatment time 24 hours Nickel ion concentration in the mouth surface 7 814/1 Washed with plQQJ of water per 1g of nickel oxalate P/Nl value 0.1
%

Claims (1)

[Claims] Oxalic acid was added to the chemical nickel plating aging waste solution using hypophosphite as a reducing agent and an organic acid as a complexing agent to adjust the pH to 1.
Chemical nickel plating characterized by acidicity of ~3 to precipitate nickel ions complexed with organic acids in aged wastewater as insoluble nickel oxalate, and at the same time recover the waste as nickel oxalate with low phosphorus content. A method for recovering nickel from bath waste.