JP2769774B2 - Method and apparatus for regenerating electroless nickel plating wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for regenerating and recycling a waste electroless nickel plating waste solution.

[0002]

BACKGROUND OF THE INVENTION Since electroless nickel plating can form a plating film by utilizing a chemical reaction of a reducing agent,
Plating film can be formed on non-conductive ceramics and plastics. Also, compared with electroplating, the plating film has excellent coverage and a uniform film without pinholes can be obtained. , Automotive fuel supply parts,
Widely used for camera parts, printing roll parts and the like. However, if a reaction inhibitory component by-produced during plating accumulates, the plating reaction is inhibited, and good plating cannot be performed, and the entire waste liquid is now being disposed of by a contractor as industrial waste. About 100,000 tons of these plating waste liquids are generated annually, and 90% of them are currently dumped in the ocean.

[0003]

2. Description of the Related Art The main technologies currently being studied as a method for reusing an electroless plating waste solution include (a) a plating solution using a reverse osmosis membrane or an ion exchange membrane to which hypophosphorous acid is bound. There are a reverse osmosis method and an ion-exchange membrane method for removing phosphorous acid components therein, and (b) an electrolytic method for oxidizing phosphorous acid to phosphoric acid. In addition, although the target is different from electroless nickel plating, as a method for regenerating an electroless tin plating bath, a step of adding an alkaline earth metal salt to a plating bath to precipitate a stannate of an alkaline earth metal. A means for regenerating a tin plating bath including a step of removing the precipitate of the stannate from the plating bath has also been proposed (JP-A-63-192876).

[0004]

However, in the reverse osmosis method and the ion exchange membrane method, the removal rate of phosphorous acid is 30 to 5 (a).
0%, and the (b) electrolysis method has the drawback that the specific gravity and viscosity increase with the increase in the amount of accumulated phosphoric acid, making it difficult to form a plating film. In addition, the cost of regeneration treatment is too high and the treatment efficiency is low, and it is difficult to sufficiently cope with the removal of BOD components in wastewater treatment.

In the method of regenerating a bath for electroless tin, since the technique is a processing technique for tin, which is an amphoteric metal, regeneration can be performed by the above-described means. When trying to apply it to electrolytic nickel plating wastewater,
Due to the effect of the added alkaline earth metal salt, nickel ions in the electroless nickel plating solution form precipitates as poorly soluble nickel hydroxide, and the value as a plating solution lacking nickel ions is lost. However, it cannot be applied to electroless nickel plating as it is.

An object of the present invention is to solve the above-mentioned drawbacks of the conventional electroless plating wastewater treatment technology and to develop an effective electroless plating wastewater recycling technology.

[0007]

An object of the present invention is a plating waste solution containing a salt obtained by oxidizing hypophosphite by forming a nickel film in an electroless nickel plating bath. The liquid is a waste liquid because the metal plating film is formed by utilizing the reduction reaction of the reducing agent, so that the oxidation of the reducing agent itself proceeds by the plating film forming reaction, and the phosphite which has lost the reducing power is reduced. Is accumulated in the plating solution in a large amount, and the oxidized reducing agent inhibits a plating film forming reaction, so that plating cannot be performed with the plating solution having an increased accumulated amount.

[0008] Then, the means for reacting with phosphite to form a precipitate was examined. When calcium hydroxide was added to the electroless nickel plating waste solution as a phosphite treatment agent, phosphite was added. Is generated, and it is confirmed that it can be removed as a precipitate. From the same properties, application to barium or strontium hydroxide is possible.
That is, for example, when hydroxides such as calcium hydroxide, barium hydroxide, and strontium hydroxide are added to the waste liquid,
It has been found that compounds such as calcium phosphite, barium phosphite, and strontium phosphite are produced, and the compounds are solidified, deposited as a precipitate from the solution, and can be removed by separation.

However, in the above method, when a hydroxide is added, the pH of the processing solution becomes alkali of 10 or more, and nickel ions in the electroless nickel plating solution form precipitates as poorly soluble nickel hydroxide. As a result, the solution from which the gelation of the solution has progressed and the nickel ions as the main component have been removed has no value as a plating solution, and the purpose of reuse is impaired.

Therefore, as a result of intensive studies on a means for selectively precipitating only the phosphite compound without precipitating nickel ions, ammonium hydroxide was added in an amount of 0.2 to 4 mol per mol of nickel ions present in the waste liquid. Mole percentage,
More preferably, when added at a ratio of 1.8 to 2.2 mol, a bonding relationship is formed between the ammonium ion and the nickel ion, and the compound can be dissolved in the plating waste solution as a soluble complex ion which is extremely stable even under alkaline conditions. It has been found that it does not hinder the promotion of the precipitation of the phosphite compound. That is, when ammonium hydroxide is added at a ratio of 0.2 to 4 moles relative to 1 mole of nickel ions present in the waste liquid, between the ammonium ions and nickel ions,
A complex ion is formed, and its form is (NH ₄ ) ₂ Ni (SO
₄₎ it is estimated to ₂ · 6H ₂ O, which is to exist stably as soluble material in solution, there is no fear that the nickel ions will be precipitated as the hydroxide. At this time, if the amount of ammonium hydroxide is 0.2 mol or less, nickel ions precipitate, and if the amount is 4.0 mol or more, the regenerated plating solution is decomposed and a plating film cannot be formed. on the other hand,
With 0.2 to 0.8 mol, a plating film can be formed but still has little luster. With 2.2 to 4.0 mol, a plating film is still formed but with a lot of roughness.
A good glossy film was formed in the range of 1.8 to 2.2 mol, and it was confirmed that the film was in an optimum range.

Further, a phosphorous acid compound is selected for the same purpose.
After studying the method of selective precipitation, the electroless nickel
The salt of hypophosphite oxidized by plating film formation
Containing phosphorus electrolyte in wastewater
Calcium, barium, or strontium equimolar to the acid concentration
Containing at least one of the group consisting of
Add a phosphite treatment agent, stir for a certain period of time,
As much as possible, then adjust the pH to 4-6,
Phosphorous compounds without precipitation of nickel ions
Have been found to selectively remove only That is,
As described in Example 3, the concentration of phosphorous acid in the waste liquid is equimolar.
Add calcium hydroxide and stir the solution for a certain period of time
While promoting the reaction between phosphite and calcium hydroxide,
For a certain period of time, the sub-
The acid component is precipitated as much as possible. Furthermore, in the solution
In order to remove phosphite , first, the relationship between the amount of calcium phosphite dissolved and the pH was examined. As shown in FIG.
It was found that the dissolution amount of calcium phosphite was remarkably reduced from about pH 3. On the other hand, when the relationship between the reaction of nickel ions with hydroxide and pH was tested, as shown in Table 1, no precipitation occurred at pH 6 or lower, and about 6% precipitation was generated at pH 7 to 8. And at pH 9 2
It was found that a precipitate of 99% was formed at a pH of 8% and a pH of 10 or more. From these results, the pH of the treatment solution was adjusted to
At pH 4 or higher where the amount of dissolved
It is possible to maximize the precipitation of the phosphite compound without precipitating nickel by adjusting it to 6 or less at which no phosphite compound is generated, that is, it is possible to selectively precipitate only the phosphite compound and remove it. became.

[0012]

[Table 1] Conditions) NiCl ₂ is dissolved in 0.1N HCl, and Ni ²⁺
Was prepared, and a pH adjusting reagent was administered thereto, and the residual concentration of Ni in the solution after the formation of the precipitate was measured.

The precipitated phosphite compound is separated by separation means including a centrifugal separator and the like described below. At this time, when calcium is used as the phosphite treatment agent, excessive calcium ions remain, and if this is used as it is as a regenerating plating solution, the gloss of the film tends to be lost. Therefore, it is preferable to add a fluorine compound, for example, ammonium fluoride (NH ₄ F), react with residual calcium to form a precipitate as calcium fluoride, and separate and remove the precipitate after removing the precipitate of the phosphite compound. . At this time, the fluorine compound not only promotes precipitation, but also
It is suitable because it increases the gloss of the plating film.

[0014] The filtrate after the precipitation and separation can be used as it is as an electroless nickel plating solution again.
More desirably, the components of the processing solution are analyzed, and when nickel sulfate, hypophosphorous acid, organic acid, and the like are insufficient, it is desirable to make up for this and to regenerate as a complete plating solution.

When electroless nickel plating was performed using the thus obtained regenerating solution, the deposition rate of the film, uniform deposition of the film, hardness of the film, corrosion resistance of the film, adhesion of the film, etc. The characteristic values were comparable to those of a new plating bath, and were confirmed to be excellent in physical properties.

Next, an apparatus for regenerating an electroless nickel plating waste solution for realizing the above method comprises a storage tank for storing the electroless nickel plating waste solution, and a reaction between the waste solution, ammonium hydroxide and a phosphite treatment agent. When a reaction tank for selectively generating a phosphite compound, a separation tank for removing a precipitate generated by the reaction, and a temperature of a separated solution from the separation tank, and the phosphite treatment agent is calcium. And a heating tank for promoting further precipitation of calcium hydroxide. Desirably, an adjusting tank is provided after the heating tank for charging the insufficient chemical into the processing liquid.

The operation of the reproducing apparatus will be described first.
The solution sent from the storage tank that stores the plating waste solution is mixed with the phosphating agent and ammonium hydroxide charged from the chemical tank in the reaction tank, or the pH is adjusted to avoid precipitation of nickel ions. While promoting the reaction of forming a phosphorous acid compound. When the reaction is completed, the treatment solution is sent to a separation tank, and a sediment having a large specific gravity is separated and removed by a centrifugal separator in a centrifuge in the separation tank to remove a phosphite compound as a plating inhibiting component. Can be. The treatment liquid is put into a heating bath, the temperature of the liquid is raised, the solubility of calcium is lowered by the temperature raising effect, and the calcium hydroxide which is still dissolved in the liquid is precipitated, thereby completely removing the calcium hydroxide. be able to. For further perfection, put into the adjustment tank and replenish the plating bath with insufficient components such as nickel sulfate, hypophosphorous acid, organic acid, etc. from the chemical tank, and return such processing solution to the plating tank for reuse. can do.

[0018]

According to the present invention, based on the above constitution and operation, it is possible to greatly reduce phosphorous acid as a plating inhibiting component while keeping the rate of reduction of nickel concentration as a plating main component to a minimum. Selective removal is possible, and an epoch-making effect is achieved in that components necessary for plating film formation are secured and reuse becomes possible. The apparatus of the present invention equipped with a centrifugal separator, a heating tank, and the like is capable of sufficiently removing a phosphorous acid component, which is a plating-inhibiting component, and is optimal as a reprocessing apparatus, and is a complicated and expensive apparatus. This is an extremely useful invention that does not require a device and provides a simple and efficient mechanism.

[0019]

【Example】

(Example 1) Ammonium hydroxide was added to a waste solution of electroless nickel plating containing 100 g / L of phosphorous acid as a plating inhibiting component at various concentrations with respect to 1 mol of nickel ions in the waste solution. 60 g of calcium hydroxide adjusted to the same concentration as the phosphorous acid concentration in the waste liquid was added,
After stirring for 30 minutes, the mixture was allowed to stand for 3 hours and then separated into solid and liquid by centrifugation. Next, the separated solution was subjected to microfiltration, sulfuric acid was added to the filtrate to adjust the pH to 4.5, the temperature of the solution was raised to 70 ° C., and after heating for 30 minutes, microfiltration was immediately performed. Using the filtrate as a regenerating solution for electroless plating, a plating film was formed. The results are shown in Table 2. As shown in Table 2, it is possible to form a plating film when the concentration of ammonium hydroxide is in the range of 0.2 to 4.0 mol with respect to 1 mol of nickel ions in the waste liquid. The best film was formed in the range of 1.8 to 2.2 mol, and it was found that this range was the optimum range.

[0020]

[Table 2]

(Example 2) Phosphorous acid 1 as a plating inhibiting component
2.0 mol of ammonium hydroxide was added to the electroless nickel plating waste solution containing 00 g / L, and after stirring, calcium hydroxide adjusted to a slurry state was added with 60 g of an equimolar concentration of the phosphorous acid concentration in the waste solution to obtain 30 g After stirring for 3 minutes, the mixture was allowed to stand for 3 hours, and then separated into solid and liquid by centrifugation. Next, the separated solution was subjected to microfiltration, sulfuric acid was added to the filtrate to adjust the pH to 4.5, the temperature of the solution was raised to 70 ° C., and after heating for 30 minutes, microfiltration was immediately performed. For comparison, the components of a plating bath newly prepared for performing electroless nickel plating (hereinafter referred to as a new bath) and the components of the filtrate obtained when the treatment was performed without adding ammonium hydroxide were analyzed. The results are as shown in Table 3. In the sample in which ammonium hydroxide was added to the plating waste liquid, the removal rate of the phosphorous acid component that inhibits plating reached 92%, while 94% of nickel ions were retained. It was found to be excellent and selectively removed. In contrast,
In the plating waste solution containing no ammonium hydroxide, 96% of the nickel ions were removed, and it was found that almost no plating solution was suitable for reuse.

[0022]

[Table 3]

Example 3 Nickel sulfate 25 g / L, hypophosphorous acid 28 g / L, complexing agent 55 g / L, phosphorous acid 120 g / L
A sulfuric acid was added to the solution to adjust the pH to 4.6. Then, 71 g of calcium hydroxide having an equimolar concentration to the phosphorous acid concentration in the waste solution was added, and the mixture was stirred for 30 minutes. Sulfuric acid was added to adjust the pH of the treatment solution to 6.0,
After leaving for 3 hours, the same processing as in Example 1 was performed. The results are as shown in Table 4, and the removal rate of the phosphorous acid component was 99%.
, While 88% of the nickel ions were retained, again showing excellent and selective removal. On the other hand, when calcium hydroxide was directly added to the waste liquid for comparison, the pH of the treatment liquid became 10.5. In this state, the gelation of the liquid proceeded and nickel ions were converted into nickel hydroxide in the waste liquid. It gradually settled out and could not be reused.

[0024]

[Table 4]

(Example 4) A nickel plating film was formed using the regenerating solutions of Examples 1 and 2, and a difference in characteristics from a nickel plating film produced using a new bath was examined. The results are shown in Table 5. As shown in Table 5, various characteristic values of the nickel plating film prepared using the regenerating solution show excellent values not inferior to the film formed by the new bath. It was clarified that it can be used for plating in steel.

[0026]

[Table 5]

(Embodiment of Reproducing Apparatus) Next, an embodiment of an apparatus for realizing the above-mentioned reproducing method will be described. Reference numeral 1 denotes a storage tank for storing a waste liquid of electroless nickel plating, in which a pH meter for pH control is provided. 2 is a reaction tank for promoting the reaction between the phosphite in the waste liquid and the ammonium hydroxide or the phosphite treatment agent in the pH-adjusted liquid. With the mouth 3a facing the reaction tank 2,
In the lower part of the reaction tank 2, a stirring blade 2a for making the reaction uniform is arranged.

Next to the reaction tank 2, a separation tank 4 for removing the precipitate generated in the reaction tank 2 is arranged.
Inside, a centrifugal separator 4a of about 1 mφ is disposed, and a sediment having a large specific gravity is separated by a centrifugal action. The separation tank 4 may be provided with filter paper or the like. However, the precipitation of the phosphite compound tends to be clogged because the particles are small, and the centrifugal separator 4a is suitable for continuous processing.

Reference numeral 5 denotes a storage tank for temporarily storing the processing liquid from which the precipitate has been removed, and the liquid in the storage tank 5 is filtered by a filter 6.
To the heating tank 7, and the filter 6 filters fine precipitated particles that are not separated in the separation tank 5.

7 is a heating tank for heating the processing solution,
Since calcium hydroxide has the property that its solubility decreases with increasing temperature, when calcium is used as the phosphite treatment agent, this property is used to raise the liquid temperature to 80 to 90 ° C. by steam heating or the like. The temperature is raised to promote the precipitation effect associated with the decrease in solubility to promote the deposition of calcium hydroxide.

Reference numeral 8 denotes a filter for filtering the sediment.
The adjustment tank 9 is used to reuse the treatment solution after the removal of the phosphite compound as a plating inhibitor as an electroless nickel plating solution. It communicates with a chemical tank 10 equipped with phosphoric acid, ammonium hydroxide, an organic acid, etc., and replenishes and adjusts the processing solution with a deficient chemical to obtain a regenerating solution in a more desirable form. The adjusting tank 9 is communicated with the plating tank so that the regenerating process can be performed cyclically.

(Operation of Embodiment of Recycling Apparatus) The operation of this embodiment will be described. The processing liquid pumped from the storage tank 1 storing the plating waste liquid is supplied from the chemical tank 3 to the reaction tank 2 first. The added phosphite treatment agent, for example, calcium hydroxide, is mixed in aqueous ammonia or in a pH-adjusting solution, and promotes a phosphite compound formation reaction while avoiding precipitation of nickel ions therein.

The reaction time is about 30 minutes to 1 hour. When the reaction is completed, the treatment liquid mixed with the precipitate is sent to the separation tank 4, and the sediment having a large specific gravity is centrifuged by the centrifuge 4a in the separation tank 4. Is separated by centrifugation. At this time, the centrifugal separator 4a can perform continuous processing without causing clogging or the like even if the precipitate of the phosphite compound is fine.

Next, the processing solution from which the phosphite compound has been removed enters the temporary storage tank 5, and after filtering the remaining fine particles with the filter 6, enters the heating tank 7. In the heating tank 7, the liquid temperature is maintained at 80 to 90 ° C. by steam heating, the solubility of calcium hydroxide is reduced by the temperature increasing effect, and calcium hydroxide still dissolved in the liquid is precipitated. In the filter 8, the removal action is completely completed.

The treatment solution thus obtained removes the phosphite compound as a plating-inhibiting component and sufficiently retains the nickel ion component, so that it can be reused as it is for electroless nipmel plating. However, in order to further improve the completeness, the components are charged into the adjusting tank 9 and replenished from the chemical tank 10 with insufficient components as a plating bath such as nickel sulfate, sulfuric acid, hypophosphorous acid, ammonium hydroxide, and organic acids. If such a treatment solution is returned to the plating tank and reused, the plating waste solution can be recycled.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a device of the present invention.

FIG. 2 is a graph showing the amount of calcium phosphite dissolved.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Storage tank 2 Reaction tank 3 Chemical tank 4 Separation tank 4a Centrifugal separator 5 Storage tank 6 Filtration machine 7 Heating tank 8 Filtration machine 9 Adjustment tank 10 Chemical tank

Claims (6)

(57) [Claims] 1. An electroless nickel plating waste solution containing a salt in which hypophosphite has been oxidized by forming an electroless nickel plating film, ammonium hydroxide is added in an amount of 0.2 mol per mol of nickel ions present in the waste solution. ４4 mol, more preferably 1.8１2.2 mol, and then a phosphite treatment agent containing at least one of the group consisting of calcium, barium or strontium hydroxide is added. And selectively removing a phosphite compound without causing precipitation of nickel ions. 2. The concentration of phosphorous acid in wastewater of electroless nickel plating wastewater containing a salt obtained by oxidizing hypophosphite by forming an electroless nickel plating film and an organic acid as a complexing agent. And a phosphite treating agent containing at least one of the group consisting of hydroxides of calcium, barium or strontium in equimolar amounts, and stirred for a certain period of time to precipitate the phosphite component as much as possible, Then adjust the pH to 4-6,
A method for regenerating an electroless nickel plating waste liquid, comprising selectively removing only a phosphite compound without precipitating nickel ions. 3. The method according to claim 2, wherein an organic acid is added to the electroless nickel plating waste liquid. 4. When calcium is used as the phosphite-treating agent, a fluorine compound is added to remove a precipitate of the phosphite compound to form a precipitate of calcium fluoride, which is separated and removed. The method for regenerating an electroless nickel plating waste liquid according to any one of the above items. 5. A storage tank for storing an electroless nickel plating waste liquid, a reaction tank for promoting a reaction between the waste liquid and ammonia and a phosphite treatment agent to selectively generate a phosphite compound, and a precipitate formed by the reaction. An apparatus for regenerating an electroless nickel plating waste liquid, comprising: a separation tank for removing substances; and a heating tank for raising the temperature of the separated liquid from the separation tank to promote further precipitation of calcium hydroxide. 6. The apparatus according to claim 5, further comprising an adjusting tank for introducing a chemical insufficient in the processing liquid after the heating tank.