JP3181824B2 - Treatment method for electroless nickel plating aging solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of industrially efficiently separating and removing nickel ions, hypophosphorous acid, phosphorous acid and organic acids remaining in an aging solution for electroless nickel plating and disposing them. The present invention relates to a method for treating an electroless nickel plating aging solution that renders a non-polluting state up to a stable state.

[0002]

2. Description of the Related Art At present, electroless plating technology is utilized in various fields from decorative plating articles to production of functional electronic components such as magnetic disks and magnetic tapes. Nickel-cobalt alloys are partially applied in addition to nickel, which has been widely used in the past.

[0003] The electroless plating method is generally carried out by immersing a substrate to be plated in a plating solution prepared in advance and reacting it for an empirically determined time. Even with proper management, an increase in oxidation products during the reaction is inevitable, and the processing liquid used to some extent can no longer be reused.

For this reason, a bath solution that has undergone a certain plating reaction is
Despite large amounts of plating metal ions such as Ni ²⁺ and reducing components such as sodium hypophosphite remaining in the solution, they are often discarded as plating aging solutions by means of ocean dumping. Was.

[0005] However, marine dumping has been banned from the demands of pollution prevention and environmental purification, and on the other hand, from the viewpoint of active collection and reuse of valuable metal components contained, techniques for treating plating aging solutions have been actively developed. Some of them have been put to practical use.

[0006] As a method of treating the nickel plating aging solution,
The main method is to separate and recover nickel ions, for example, a method of extracting and recovering nickel by an electrolytic method, a method of injecting a large amount of iron powder or vanadium salt into a plating aging solution, inducing self-decomposition, and separating and collecting, A method of adsorbing on an ion-exchange resin, a method of putting an aluminum plate or aluminum foil into an alkaline plating aging solution to precipitate nickel, recovering it with nitric acid, and adsorbing nickel remaining in the mother liquor with a chelating resin ( JP-A-51-6136), a method of applying a plating aging solution to a raw material in a method of producing a powdered electroless plating powder by an addition method, and the like have been proposed. Also, a method of separating and recovering dissolved phosphorous acid from the standpoint of environmental pollution has been proposed. For example, titanium oxide carrying a noble metal such as Pt in a state where a plating aging solution is kept in an acidic state is used as a photocatalyst. A method of oxidizing hypophosphite ions to phosphate ions or converting the same to calcium phosphate (JP-A-6-136549). On the other hand, nickel is separated and recovered from the plating aging solution,
Furthermore, a batch processing method of recovering phosphorous acid has been proposed. For example, the plating aging solution is subjected to electroless plating on mica powder to recover nickel, and the mother liquor is oxidized with hydrogen peroxide or the like to be converted into orthophosphate ions, which are then converted into calcium ions (Ca ²⁺ ). Method of reacting to precipitate and separate as calcium phosphite or calcium phosphate ｛“Study on treatment technology for phosphorus-based difficult-to-treat plating effluent” Research Report of Product Chemistry No. 121｝, treating used electroless nickel plating solution with oxalic acid By removing minerals and then adding a mineral acid and a calcium compound, followed by calcination in the air to enable separation and recovery of valuable resources without discharging pollution (Japanese Patent Application Laid-Open No. Hei 7-206444). Is mentioned.

However, all of the above methods have operational or economic disadvantages and are difficult to implement industrially.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the present inventors have conducted intensive studies on a rational treatment method for an electroless nickel plating aging solution. And then subjecting it to an electroless plating reaction, nickel ions can be substantially completely and easily separated and recovered as nickel metal, and the phosphorous acid remaining in the separated mother liquor can be separated from gypsum or mineral acid and slaked lime. The present inventors have found that the plating aging solution can be made non-polluting to a state where it can be discarded by separating and recovering calcium phosphite or calcium phosphate by an oxidation reaction under the action of the above, thereby completing the present invention.

That is, the present invention relates to an electroless nickel plating capable of industrially inexpensively and effectively separating and recovering Ni ²⁺ and phosphorous acid from an aging solution for electroless nickel plating to make it non-polluting until it can be disposed of. An object of the present invention is to provide a method for treating an aging solution.

[0010]

SUMMARY OF THE INVENTION The present invention provides a method for treating an electroless nickel plating aging solution .
contacting the aging solution with nickel powder at pH
Ri and to perform the electroless plating reaction, the first separation step of separating and recovering nickel ions in the aging solution as nickel metal,
A gypsum or mineral acid and slaked lime are allowed to act on the separated mother liquor to sequentially perform a second separation step of separating and recovering dissolved phosphorous acid as calcium phosphite.

Hereinafter, the present invention will be described in detail. The electroless nickel plating aging solution to be treated in the present invention is a nickel plating waste solution mainly using sodium hypophosphite as a reducing agent, but is applicable to a plating waste solution using a nickel-cobalt alloy as a plating metal source. You can also. The term "plating aging solution" as used here means that when electroless nickel plating is performed with a plating solution in a bath, sodium hypophosphite used as a reducing agent is oxidized, and the plating function gradually decreases with the generation of sodium phosphite. It refers to a bath solution to be discarded that does not exhibit a replating function in a built bath even though a plating solution is newly replenished and contains a considerable amount of Ni ²⁺ .

Although the composition of the electroless nickel plating aging solution varies depending on the composition of the bath, the plating conditions, and the like, one example of the composition of the nickel plating aging solution is that Ni ²⁺
There _{4~7g / L, H 2 PO 2} 2- is 25~55g / L, H
PO ₃ ^2-is 80~100g / L, SO ₄ ^2- is 30 to 75
g / L, chelating agent is 30 to 55 g / L, Na ⁺ 46 to
The hydrogen ion concentration of the aging solution is generally about pH 4.5 to 5.5. However, the electroless nickel plating aging solution to be treated in the present invention is not limited to those having the above composition.

The first separation step according to the present invention is a step of selectively separating and recovering nickel ions as nickel metal from the aging solution for electroless nickel plating as described above. In other words, this step is to complete the nickel plating reaction so as to substantially remove the remaining Ni ²⁺ .

As described above, the electroless nickel plating aging solution is usually an acidic solution having a pH of about 4.5. In the first step, the pH of the solution is adjusted to a range around neutrality, usually pH 6 in the treatment. To 9, preferably in the range of pH 7 to 8. For adjusting the pH, a commonly used alkaline agent such as sodium hydroxide or potassium hydroxide is used.

The feature of the first step in the present invention resides in that the electroless nickel plating aging solution adjusted to about neutrality is brought into contact with nickel powder while stirring under heating to carry out an electroless plating reaction. The heating of the electroless nickel plating solution is performed under the necessary operating conditions for efficiently recovering the dissolved Ni ²⁺ , and the temperature is generally maintained at 50 to 90 ° C., preferably 60 to 80 ° C. Nickel powder is a component that functions as a recovery agent for Ni ²⁺ , and any nickel metal powder that can be dispersed in water can be used without any particular limitation. The most preferable mode of operation is to repeatedly use the nickel powder used for the electroless reaction as it is. The reason for this is that the nickel powder used for the first electroless plating reaction can be used repeatedly, which is economically advantageous. If the nickel powder grows in the course of the electroless plating reaction, it may be used after pulverization.

The operation of bringing the nickel powder into contact with the above electroless nickel plating aging solution to cause an electroless plating reaction is as follows: (1) After introducing the nickel powder into the plating aging solution adjusted to pH 6 to 9 at room temperature, A method of performing an electroless plating reaction while stirring at a temperature of 90 ° C., (2) an aqueous slurry of nickel powder previously adjusted to a temperature of 50 to 90 ° C. and a pH of 6 to 9 (a diluted aging solution may be used as a dispersion medium) )), A method of simultaneously or continuously adding an electroless nickel plating and an alkali agent to carry out an electroless plating reaction under stirring while heating and maintaining a pH state, or (3) these methods. It can be performed by any of the methods of performing an electroless plating reaction in combination. Among them, the method (1) is industrially most advantageous because the operation is simple and the nickel recovery rate is high. When the method (1) is used, the operation is not limited to one-stage operation, and can be performed continuously by performing multi-stage operation.

In the course of the electroless plating reaction, hydrogen gas is generated, and this gas firing phenomenon is a measure of the start and end of the reaction. That is, the reaction end point is the point at which the gas firing phenomenon stops. After the completion of the electroless plating reaction, the treatment is completed by aging usually for 0.5 hour or more, preferably for 1 to 2 hours, and the mixture is filtered and separated by a conventional method. Therefore, by the first separation step, the amount of dissolved Ni ²⁺ is 1
Nickel can be recovered at a surprisingly high removal rate of 0 ppm or less, and the recovered nickel component is used as a valuable metal. On the other hand, hypophosphorous acid is oxidized to phosphorous acid, so that the treated mother liquor contains substantially no metal component and has a composition mainly composed of sodium phosphite and sodium sulfate. Very reasonable.

That is, the second separation step is a step of separating and recovering phosphorous acid from the mother liquor as calcium phosphite. As a specific operation, gypsum or mineral acid and slaked lime are added to the mother liquor after the first separation step, and the mixture is reacted under heating to precipitate and remove dissolved phosphorous acid by calcium phosphite.

In this step, the concentration of the applicable phosphorous acid component is not particularly limited, but is usually 30% by weight or less, preferably 20% by weight or less.

The gypsum and slaked lime used are not particularly limited, but are preferably finer particles from the viewpoint of reactivity. Specifically, the average particle diameter is usually 1 to 50 μm, preferably 10 to 50 μm, and particularly preferably about 10 to 50 μm. It is about 20 μm. This is because if the particle size exceeds 50 μm, the reactivity becomes poor, and if the particle size is less than 1 μm, it is difficult to obtain industrially.

The amounts of gypsum and slaked lime added are slightly smaller than the exact stoichiometry relative to the amount of phosphorous acid contained in the mother liquor, and are usually 1.1 to 1.8 relative to phosphorous acid. The molar amount is twice as much, preferably 1.2 to 1.6 times.

The pH at the time of the reaction varies slightly depending on the type of calcium salt used. When gypsum is used, the pH of the reaction system is usually about 7 to 9, preferably about 8 at neutrality. On the other hand, when slaked lime is used, the pH during the reaction
Is a weakly alkaline region of usually 7 to 12, preferably 8 to 10. The reaction system becomes strongly alkaline with the addition of the above amount of slaked lime in the reaction system. Therefore, the reaction proceeds by adding a mineral acid such as sulfuric acid or hydrochloric acid. In this case, the amount of the mineral acid to be added is at least equimolar to the amount of phosphorous acid contained in the mother liquor, preferably 1.0 to 1.1 times. The order of addition of the mineral acid and slaked lime does not have any particular problem, and they may be added at the same time or first.

The above reaction with gypsum or slaked lime usually has a temperature of 40 to 60 ° C, preferably 45 to 50 ° C.
The reaction time is not particularly limited as long as it is 0.5 hours or longer, but is usually 0.5 to 10 hours, preferably 1 to 3 hours. After completion of the reaction, the reaction mixture is separated by filtration in a conventional manner.

As can be seen from the above, the reaction between gypsum and the mother liquor is a typical metathesis reaction, and the reaction between slaked lime and the mother liquor is a metathesis reaction accompanied by neutralization. Depends on circumstances and economic reasons. The former reaction is greatly affected by the physical properties of the gypsum, and the reaction rate may be 90% or less. Therefore, when it is necessary to more completely remove phosphite ions, the latter reaction is advantageous.

In the mother liquor treated in the second separation step, substantially no Ni ²⁺ is present, and the phosphorous acid content is usually 8,000.
ppm or less, preferably 5000 ppm or less.

Therefore, the mother liquor after the second separation step can be sufficiently discarded, but if stricter discharge regulations are required, the following third and fourth separation steps can be sequentially performed as desired. Further, the phosphorous acid component and the organic acid are further removed from the mother liquor.

The third separation step is a step of oxidatively decomposing a phosphorous acid component into a phosphoric acid component and separating and recovering it as calcium phosphate. Specifically, an oxidizing agent is added to the mother liquor after the second separation step to oxidize and decompose phosphorous acid, and then a calcium compound is added to separate and recover the phosphoric acid as calcium phosphate.

The type of the oxidizing agent is not particularly limited, and a common oxidizing agent such as chlorine, sodium hypochlorite, hydrogen peroxide and ozone can be used. The addition amount of the oxidizing agent is usually 0.8 to 1.2 times mol, preferably 0.9 times mol, relative to the BOD amount. The reaction temperature is not particularly limited, and may be usually about 20 ° C. The pH of the reaction system is usually 1 to 5, preferably 2 to 3. The reaction time is not particularly limited as long as it is 1 hour or longer, and is usually 1 to 4, preferably 2 to 3 hours. Thus, the phosphorous acid component is oxidized to the orthophosphoric acid component.

Then, the residual dissolved phosphoric acid component and a calcium salt are allowed to act to separate and recover calcium phosphate from the mother liquor, whereby oxyacid ions of phosphorus can be completely removed from the mother liquor. The type of calcium salt used is, for example, slaked lime, calcium chloride,
Gypsum etc., but calcium salt and pH of reaction system
Slaked lime, which also acts as a conditioning agent, is most advantageous.

The amount of the calcium salt to be added is at least stoichiometric, preferably about 1.5 to 2.0 moles, relative to phosphoric acid. The reaction temperature is not limited, but is not lower than room temperature, preferably about 50 ° C. The pH of the reaction system is usually 7 to 10, preferably 8 to 9. The reaction time is not particularly limited because it is an instantaneous precipitation reaction, but it is usually 1 to 3 hours, preferably about 2 hours, in view of the aging operation in consideration of separability and the like. After the completion of the reaction, calcium phosphate is separated and recovered from the mother liquor by filtration in a conventional manner.

The fourth separation step is a step of biologically removing organic acids remaining in the mother liquor after the third separation step by an activated sludge method. The total amount of activated sludge (MLSS concentration) in the aeration tank is usually 2000 to 3000 mg / L, preferably 2500
mg / L, and the residence time of the treated water is not particularly limited as long as it is 40 hours or longer, and is usually 40 to 60 hours, preferably 50 hours.

By sequentially performing the third separation step and the fourth separation step after the first separation step and the second separation step, the nickel ion concentration in the electroless nickel plating aging solution is usually 1 ppm or less, preferably 0 ppm or less. .5 ppm or less, BOD
The concentration is usually 30 ppm or less, preferably 15 ppm or less, and the P concentration is usually 10 ppm or less, preferably 4 pp.
m or less, the plating waste liquid can be rationally treated by the method according to the present invention.

[0033]

The present invention provides a method for treating an electroless nickel plating aging solution, wherein the plating aging solution is brought into contact with Ni powder,
A first separation step of separating and recovering dissolved Ni ²⁺ as nickel metal, a second separation step of separating and recovering the separated mother liquor by treating gypsum or mineral acid and slaked lime to separate and recover phosphorous acid as calcium phosphite It is characterized by applying.

In the first separation step, pH is adjusted around neutral,
Using a heated electroless nickel aging solution as a plating bath,
It is recovered and separated as metal. By this first separation step, hypophosphorous acid is oxidized to phosphorous acid, and Ni ²⁺ in the aging solution is substantially absent, and at most 10 pp
At m, the recovery of Ni ²⁺ is remarkably high, and the effect facilitates the transfer to the next second step. Thus, in the first separation step, N
It is completely unexpected that the i ²⁺ can be recovered purposefully, and the detailed mechanism is unknown. However, it is because the plating reaction is performed near neutrality and the plating substrate is selected from nickel powder. it is conceivable that.

The second separation step is a step in which gypsum or slaked lime acts as a calcium salt to separate and recover phosphorous acid as calcium phosphite. For example, when gypsum is used, the reaction formula is as shown below.

[0035]

[Reaction formula 1] Na ₂ HPO ₃ + CaSO ₄ → CaHPO ₃ ↓ + Na ₂ SO ₄ (1)

In the above reaction formula, the dissolution of gypsum is rate-limiting and reacts with phosphite ions to cause precipitation of calcium phosphite, and the liquid phase is a metathesis reaction producing sodium sulfate, which is also unexpected. The reaction proceeds, which is an economical method.

On the other hand, the mechanism of calcium phosphite formation by slaked lime when sulfuric acid is used as the mineral acid is as follows:

[0038]

[Reaction formula 2] Na ₂ HPO ₃ + H ₂ SO ₄ + Ca (OH) ₂ → CaHPO ₃ ↓ + Na ₂ SO ₄ + 2H ₂ O (2)

In the above reaction formula, slaked lime sequentially dissolves and reacts with phosphite ions to cause precipitation of calcium phosphite, and the liquid phase forms sodium sulfate, which is substantially different from formula (1). Absent.

The separated mother liquor treated in the second separation step is substantially free of Ni ²⁺ , and the phosphorous content is usually 8000 ppm or less, preferably 5000 ppm or less, corresponding to the solubility of the reaction system. I do. In the present invention, the treatment of the plating waste liquid is substantially finished in the above two steps, but further, if the treatment of the waste liquid is considered, the plating residual liquid remains after the first separation step and the second separation step as necessary. A third separation step in which phosphorous acid is oxidized to phosphoric acid, and the phosphoric acid is reacted with a calcium salt to completely separate and recover phosphorus oxyacid ions as calcium phosphate; and the remaining organic acid is activated sludge. Thus, the treatment is completed by sequentially performing the fourth separation step of biologically removing the fourth separation step.

Thus, the electroless nickel plating aging solution can be made pollution-free up to treated water substantially free of nickel ions, phosphorous acid and organic acids. The recovered nickel metal can be circulated during the process and then easily and effectively used as valuables.
Calcium phosphite can be used for rust preventive pigments, fillers or calcined calcined calcium phosphate ceramics and fertilizers.

[0042]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A used electroless nickel plating aging solution having the composition shown in Table 1 was used.

[0044]

[Table 1]

First separation step: 1 t of electroless nickel plating waste liquid having the above composition (specific gravity: 1.
2, pH 4.5), add 10kg of Ni powder and add 50wt
The pH was maintained at 8 by dropwise addition of% NaOH, and the temperature was raised until the reaction started. Hydrogen gas was generated at a temperature of about 65 ° C., and while maintaining the pH at 8 by dropwise addition of 50% wt NaOH, the temperature was further raised to 80 ° C. and aged for 1 hour. After the completion of the electroless plating reaction, the mixture was separated by filtration by a conventional method, and 14.5.
Kg of nickel metal was separated and recovered (removal rate 99.9).
%). The mother liquor after filtration and separation ^contained 5 mg / Ni ^2+.
L and 148 g / L of phosphorous acid remained.

Second separation step 50 wt% sulfuric acid 366 was added to 1.2 t of the mother liquor after the first separation step.
Kg and 180 kg of slaked lime powder were added (pH 9). 5
The temperature was raised to 0 ° C. and aged for 2 hours while stirring. Next, the reaction solution was separated by filtration in a usual manner, and 355 kg
Of calcium phosphite was separated and recovered (removal rate 95
%). The mother liquor after filtration and separation contained phosphorous acid in an amount of 6.
6 g / L remained.

By the above two steps, it was found that each of them can be recovered from the plating aging solution as a valuable resource, and as a result, the plating aging solution can be rationally treated.

Third separation step 1.35 t of mother liquor after the second separation step (BOD: 3500 m
g / L), 16 kg of chlorine gas was blown therein, and the phosphorous acid component was oxidized and decomposed at 20 ° C. for 30 minutes. Then, slaked lime powder 1
2.5 kg was added, and the mixture was aged at 50 ° C. for 2 hours with stirring. After completion of the reaction, the reaction mixture was separated by filtration in a conventional manner to recover 24 kg of calcium phosphate (removal rate: 99%). Incidentally, the mother liquor after the filtration separation is only phosphoric acid content as PO ₄ ^3- 20 m
It was only as low as g / L.

Fourth step: 1.345 t of the mother liquor after the third separation step was subjected to activated sludge treatment in a 2 m ³ aeration tank (MLSS amount: 2500 mg / L) for 50 hours to remove organic acids, and 19 kg Sludge cake was removed (BOD removal rate 99%). As a result,
As shown in Table 2, the main liquid composition of the final treated water was completely harmless and could be discharged as it was.

[0050]

[Table 2] * P removal rate was calculated based on the hypophosphorous acid content before treatment and the P content in the phosphorous acid content.

[0051]

As described above, according to the method for treating an electroless nickel plating aging solution of the present invention, Ni ²⁺ , phosphorous acid and an organic acid can be industrially produced from the plating aging solution by a simple operation. It can be efficiently separated and removed, and it can be made pollution-free until it can be discarded, and its industrial utility value is extremely large.

Claims (3)

(57) [Claims] An electroless nickel plating aging solution and a nickel powder are brought into contact with each other at a pH near neutrality to cause an electroless plating reaction to separate and recover nickel ions in the aging solution as nickel metal. An electroless nickel plating aging process, in which a gypsum or mineral acid and slaked lime are allowed to act on the separated mother liquor to separate and recover dissolved phosphorous acid as calcium phosphite. Liquid treatment method. 2. A further, the mother liquor of the second separation step, by adding an oxidizing agent, after oxidative decomposition of phosphorous acid content remaining,
A method for treating an electroless nickel plating aging solution, which is subjected to a third separation step of causing slaked lime to act to separate and collect calcium phosphate. 3. A method for treating an electroless nickel plating aging solution, further comprising a fourth separation step of removing an organic acid in the mother liquor after the third separation step by an activated sludge method.