JP2975577B2 - Electrolytic treatment of 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 for electrolytically treating an electroless nickel plating waste liquid, an electrode for a cathode of an electrolytic treatment apparatus for the waste liquid, and an electrolytic treatment apparatus for the waste liquid.

[0002]

2. Description of the Related Art Generally, in an electroless plating method in which a metal is chemically precipitated by a metal ion and a reducing agent, the life of a plating solution used is short, and a large amount of a concentrated waste solution (same as an aging solution) is generated. Occur. In particular, the electroless nickel plating waste liquid contains sodium hypophosphite (H ₂ P) as a reducing agent.
Since O ₂ ⁻ ) is used, the plating waste liquid contains a large amount of phosphorus compounds such as sodium phosphite (H ₂ PO ₃ ⁻ ) generated by oxidation.

[0003] Plating waste liquid containing a phosphorus compound has a great effect on marine organisms such as plankton when dumped into the ocean as it is, and also has a biological oxygen demand (BOD value) and a chemical level which are indicative of the pollution level of the water environment. Oxygen demand (COD
Value), it is necessary to remove the phosphorus compound from the plating waste liquid so that the concentration becomes as low as possible from the viewpoint of environmental hygiene.

Among the phosphorus compounds, those present as phosphite ions in the waste liquid can be coagulated and precipitated by adding a calcium salt at a pH of 5 or more, and can be removed from the waste liquid. Since phosphorus compounds dissolved as hypophosphite ions do not aggregate and precipitate, they need to be phosphite ionized by oxidation treatment.

[0005] Conventional electroless nickel plating wastewater treatment methods for removing phosphorus compounds and organic acids from the wastewater include the following.
There is known a treatment method (called a self-decomposition method) in which a waste liquid is heated to 90 ° C. or more, iron powder, nickel powder, and the like are added, nickel ions are reduced, and hypophosphite ions are oxidized to phosphite ions. Have been. In addition, on the surface of the titanium dioxide photocatalyst utilizing light energy, the active oxygen generated by the reaction with water and dissolved oxygen is used as an oxidizing agent to oxidize hypophosphite ions in the plating waste liquid to phosphate ions,
At the same time, a method of decomposing organic substances such as organic acids into carbon dioxide and water is also known.

Further, as a processing method for the same purpose, there is an electrolytic processing method using an insoluble electrode as an anode. When the electroless nickel plating waste liquid is treated by the electrolytic treatment method, hypophosphite ions are oxidized to phosphate ions at the anode, and organic acids are also oxidatively decomposed.
As the D value decreases, nickel precipitates at the cathode and heavy metal components are removed from the waste liquid.

[0007]

However, in the conventional electrolytic treatment method for the electroless nickel plating waste solution, the efficiency of the oxidative decomposition of organic acids by anodic oxidation is low, and the concentration is sufficiently low (for example, a COD concentration of 500 mg / l or less). ) Has a problem that it is difficult to perform decomposition treatment quickly.

In the conventional electrolytic treatment method, the coagulated sediment is removed after the electrolytic treatment, and a complexing agent (chelate resin) is added to a liquid filtered from the coagulated sediment to filter the organic acid. It is necessary to separate the filtrate, add a photocatalyst to the filtrate, and treat it with ultraviolet light to decompose the organic acid.In such a complicated treatment process, a highly efficient and low-cost electroless nickel plating wastewater treatment should be performed. Could not.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to oxidize hypophosphorous acid to phosphorous acid and reduce and remove heavy metal components (nickel) in the waste liquid. The present invention provides an electroless nickel plating waste liquid treatment method in which the decomposition action of the organic acid in the solution by the Kolbe reaction is efficiently performed, or provides an electrode and an apparatus used in such a treatment method. Is to simplify the process, and enable high-efficiency and low-cost processing.

[0010]

In order to solve the above-mentioned problems, the present invention provides a method of electrolytically treating an electroless nickel plating wastewater by applying a direct current to an anode and a cathode disposed in the wastewater. In the above method, an electroless nickel plating waste solution is subjected to electrolytic treatment by attaching copper powder to the surface of the cathode.

In the invention of the above-mentioned treatment method, it is preferable to employ copper powder having a particle size of 0.02 to 0.5 μm, and the copper powder is formed on the metal surface by electrolytic reduction of an electrolytic solution containing copper ions. Precipitated particle size 0.02-0.5μ
m copper powder can be adopted.

In order to solve the above-mentioned problem, in another invention of the present application, a particle size of 0.0
This was used as a cathode electrode of an electrolytic treatment apparatus for an electroless nickel plating waste liquid, which was formed by depositing copper powder of 2 to 0.5 μm by electrolytic reduction.

In order to solve the same problem as described above, in another invention of the present application, an electrolytic cell containing an electroless nickel plating waste solution is provided, and an anode formed of an insoluble material is provided in the electrolytic cell. , With a particle size of 0.02-
A cathode to which copper powder of 0.5 μm was adhered was provided, and an electroless nickel plating waste effluent electrolyzing apparatus was provided by distributing power from a DC power source to the positive and negative electrodes.

According to the invention relating to the electrolytic treatment method for the electroless nickel plating waste solution, it is considered that the electrolytic oxidation reaction occurs at the cathode due to the catalytic action of the copper powder adhering to the surface of the cathode. The organic acid is decomposed and carbon dioxide is generated by the Kolbe reaction shown by. _{^{R · CO 2 -. → R}} · CO 2 → R + CO 2 ( Kolbe reaction) (wherein, R · CO ₂ ^- represents a material obtained by ionization of fatty acids such as hydroxy carboxylic acid).

As described above, in the electrolytic treatment method of the electroless nickel plating waste solution of the present invention, the copper powder coated on the surface of the cathode has an oxidizing effect at the cathode due to the catalytic action, and oxidizable substances in water such as fatty acids are used. That is, it is considered that the organic acid which can be a polluting source is oxidized and the COD value and the BOD value of the waste liquid are efficiently reduced. Therefore, in the above treatment method, there is no need to add a complexing agent (chelate resin) or to decompose the complexing agent after the treatment as in the conventional treatment method.

Further, the invention relating to the cathode electrode of the electrolysis apparatus for electroless nickel plating waste liquid according to the present invention is characterized in that copper powder having a predetermined particle size is deposited on the electrode surface, so that the electroless nickel plating waste liquid is subjected to electrolytic treatment. As the cathode used in the method,
It becomes an electrode that performs an extremely efficient oxidation reaction with a copper catalyst together with the reduction reaction.

Further, the invention relating to the apparatus for electrolyzing an electroless nickel plating waste liquid according to the present invention provides a method for producing an electroless nickel plating waste solution having a particle size of 0.0
By adopting the cathode to which the copper powder of 2 to 0.5 μm adheres, similarly to the above, there is an oxidizing action at the cathode due to the catalytic action of the copper powder, and an oxidizable substance in water such as fatty acid, that is, an organic acid which can be a pollution source. Can be oxidized, and the COD value and BOD value of the waste liquid can be efficiently reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The types of plating baths used for electroless nickel plating include hypophosphorous acid baths, hydrazine baths, borohydride compound baths, and the like. The nickel plating waste liquid does not need to be a waste liquid in which the types of the reducing agent and the complexing agent are particularly limited.
However, as is clear from the results of Examples described later, good results were obtained by treating a waste solution of a hypophosphite bath (acid bath or alkaline bath) using hypophosphite as a reducing agent. It has gained. Incidentally, typical hypophosphite bath components are shown in Table 1 below.

[0019]

[Table 1]

The electroless nickel plating waste solution to be subjected to the electrolytic treatment of the present invention is, for example, an aged electroless nickel plating solution used in the plating treatment (hereinafter referred to as an aging solution).
It is preferable to use those which have been previously treated by a self-decomposition method or the like. In the self-decomposition method, the liquid temperature of the aging solution is 90 ° C.
Heat above, add iron and nickel powder to this,
Nickel ions contained in the aging solution are reduced and precipitated to oxidize hypophosphorous acid to phosphorous acid. Usually, a phosphite ion is generated in a reaction time of about 60 minutes. To this, a calcium salt is added at a pH of 5 or more, and the phosphite is removed by coagulation precipitation as calcium phosphite or magnesium phosphite.

The anode disposed in the electroless nickel plating waste liquid may be an insoluble electrode, and its material is not particularly limited. For example, lead dioxide or an alloy of lead peroxide and titanium is used. can do.

The cathode disposed in the electroless nickel plating waste liquid is composed of a metal electrode substrate made of iron, steel (including stainless steel), etc., to which copper powder has adhered. The particle size of such copper powder is preferably 0.02 to 0.5 μm, and the specific surface area of the electrode surface to which such copper powder adhered is preferably increased as the electrolytic efficiency becomes better. .

Further, the particle size of the copper powder is set to a value between 0.02 and 0.1.
The reason why the particle size is limited to 5 μm is that, when the particle diameter is smaller than the predetermined range, the specific surface area is large but the adhesive strength is too low. It is.

In order for copper powder having a predetermined particle size to adhere to the surface of the electrode substrate as described above, for example, the electrode (cathode) substrate is immersed in an electrolytic solution containing copper ions, and this is used as a cathode. For example, a method can be adopted in which a direct current is passed between both electrodes using lead dioxide or the like as an anode, and copper powder is deposited on the surface of the cathode substrate by electrolytic reduction.

Examples of the electrolytic solution containing copper ions are shown in Table 1 above.
Can be used in addition to the copper salt to the chemical nickel plating hypophosphite bath shown in (1).

An embodiment of an apparatus for electrolyzing an electroless nickel plating waste liquid and a cathode will be described below with reference to FIGS.
It will be described based on.

As shown in FIGS. 1 and 2, the apparatus according to the first embodiment immerses an anode 2 formed of lead dioxide in an electrolytic tank 1 containing an electroless nickel plating waste solution A, Particle size of 0.02
An electrolytic treatment apparatus for electroless nickel plating waste liquid, in which a cathode 5 coated with copper powder 4 having a thickness of about 0.5 μm is immersed, and a current is supplied to the pair of electrodes from a DC power supply 6.

The electrolyzing apparatus for electroless nickel plating waste liquid of the second embodiment shown in FIG. 3 is an apparatus particularly suitable for treating a large amount of waste liquid, and accommodates electroless nickel plating waste liquid A. A reticulated anode (las anode) 8 made of lead dioxide is arranged in each of three cells in the electrolytic cell 7 and a copper powder having a particle size of 0.02 to 0.5 μm is formed on the surface of a stainless steel electrode substrate. This is an electrolytic treatment apparatus for electroless nickel plating waste liquid, in which cathodes 5 coated with, respectively, are disposed, and a current is supplied to the three pairs of electrodes from a DC power supply (not shown).

In this apparatus, an outlet hole 10 connected to an air supply pipe 9 for sending compressed air is provided on the bottom surface of the electrolytic cell 7, and a liquid flow rising by air bubbles blown out from the outlet hole 10 is formed. The waste liquid treated in each tank is sequentially sent to each of the formed electrolytic cells adjacent to each other with the partition wall 11 interposed therebetween, and the lower the concentration of the electrolytic solution, the lower the electrolytic cell on the downstream side. An exhaust duct 12 is disposed above the liquid level of the electrolytic cell, and the pressure inside the duct 12 is reduced by a pump 13 to forcibly exhaust gas such as carbon dioxide generated at the cathode of the electrolytic cell.

The treated waste liquid is returned from the storage tank at the rightmost position in FIG. 3 to the electrolytic cell at the leftmost position in the figure as necessary, and is circulated until the wastewater has a required low concentration. It is also possible.

[0031]

【Example】

[Example 1: Production Example of Cathode] 100 mg / liter of copper ion (Cu ⁺ ) was added to a hypophosphite bath for chemical nickel plating, a cathode made of stainless steel was used as a cathode, and a cathode polarization of 0 was used. When ^{2 A} / dm ² was given, glossy copper was deposited in the initial stage of energization. In this case, since the copper concentration is very small, the precipitate rapidly changes to a powdery precipitate,
The particle size of the copper powder adhering in that state has a submicron diameter of 0.1 μm.
It was about 02 to 0.5 μm.

Example 2 Electrolytic Treatment by Apparatus of First Embodiment An electroless nickel plating waste solution was treated using the electrolytic treatment apparatus of the first embodiment shown in FIGS. That is, the electroless nickel plating solution (N in Table 1
o. 6) is treated by an autolysis method to oxidize hypophosphite ions to phosphite ions to cause agglomeration and precipitation, and nickel ions to reduce and precipitate. A waste liquid (containing 20 g / liter of citric acid) from which phosphorous acid was removed was treated.

A rectangular plate-shaped (100 cm ² area) anode 2 made of lead dioxide is provided in the electrolytic cell containing the waste liquid.
A cathode 5 having copper powder having a particle size of 0.02 to 0.5 μm densely attached is provided so as to cover the entire surface of a stainless steel plate (area 100 cm ² ), and a direct current is supplied without stirring the waste liquid in the electrolytic cell. A DC current having a current density of 0.2 A / dm ² was applied between the cathode and the anode from the power supply for 25 minutes. During the energization, the liquid to be treated changed color to yellow, brown, and black sequentially, and smelled like burning coffee beans.

When the concentration of citric acid in the waste liquid after the treatment was measured by liquid chromatography, it was 10 g / liter, which was half the initial concentration.

Example 3 Electrolytic treatment by the apparatus of the first embodiment In the electrolytic treatment method of Example 2, except that the waste liquid was stirred by a stirrer,
The electrolysis was performed for minutes.

When the concentration of citric acid in the waste liquid after the treatment was measured in the same manner as in Example 2, it was 10 g / L.
It was half of the initial concentration.

[0037]

As described above, the invention of the present invention relating to the electrolytic treatment method of the electroless nickel plating waste liquid employs a cathode having a copper powder adhered to a metal surface, so that the oxidative decomposition of an organic acid can be efficiently performed. This is a commonly used wastewater treatment method for electroless nickel plating.Since there is no need to filter the complexing agent or decompose the complexing agent as the wastewater treatment process, the treatment process can be simplified, and high efficiency is achieved. There is an advantage that low-cost electrolysis can be performed.

In the invention relating to the cathode electrode of the electrolytic treatment apparatus for electroless nickel plating waste liquid according to the present invention, copper powder having a predetermined particle size is deposited on the electrode surface. There is an advantage that the cathode electrode can perform an extremely efficient oxidation reaction.

Further, in the invention relating to the electrolysis apparatus for electroless nickel plating waste liquid of the present application, a cathode to which copper powder having a predetermined particle diameter is adhered is adopted, so that, similarly to the invention relating to the waste liquid treatment method described above, There is an advantage that the oxidation action of the cathode oxidizes an organic acid that can be a polluting source in water, thereby providing an electrolytic treatment apparatus that efficiently reduces the COD value and the BOD value of the waste liquid.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an electrolytic processing apparatus according to a first embodiment.

FIG. 2 is an enlarged sectional view of a cathode of the electrolytic processing apparatus according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating an electrolytic processing apparatus according to a second embodiment.

[Description of Signs] A Waste liquid 1, 7 Electrolyte tank 2, 8 Anode 3 Electrode substrate 4 Copper powder 5 Cathode 6 DC power supply 9 Air supply pipe 10 Blow-out hole 11 Partition wall 12 Exhaust duct 13 Pump

Claims (5)

(57) [Claims] 1. A method of electrolytically treating a waste solution by applying a DC current to an anode and a cathode disposed in an electroless nickel plating waste solution, wherein the electrolytic treatment is performed by attaching copper powder to the surface of the cathode. A method for electrolytically treating an electroless nickel plating waste solution. 2. The method according to claim 1, wherein the copper powder has a particle size of 0.02 to 0.5 μm.
The method for electrolytically treating an electroless nickel plating waste solution according to claim 1, which is a copper powder. 3. The method according to claim 1, wherein the copper powder is copper powder precipitated by electrolytic reduction of a copper ion-containing electrolytic solution. 4. The method according to claim 1, wherein a particle size of 0.02 to
An electrode for a cathode of an electrolytic treatment apparatus for electroless nickel plating waste liquid, which is obtained by depositing 0.5 μm copper powder by electrolytic reduction. 5. An electrolytic cell containing an electroless nickel plating waste solution is provided, an anode formed of an insoluble material is provided in the electrolytic cell, and copper powder having a particle size of 0.02 to 0.5 μm is adhered to the surface. Electrolytic treatment equipment for electroless nickel plating wastewater, which is provided with a negative electrode and distributes power from the DC power source to the positive and negative electrodes.