JPH0221995A - Treatment of waste solution - Google Patents

Abstract

PURPOSE:To inexpensively treat a waste soln. contg. a metallic complex without contaminating the work environment by regulating a waste copper plating soln. to >=11.0pH, then adding a hydrosulfite to obtain the precipitates of copper and copper sulfide, adding the precipitates to the waste soln. to cause a reaction, and separating the formed precipitates. CONSTITUTION:The waste copper plating soln. is regulated to >=11pH with a caustic alkali, and then a hydrosulfite is added to obtain the precipitates of copper and copper sulfide. The waste soln. generated from a plating works and contg. the complex of the copper, nickel, cobalt, silver, gold, etc., with a chelating agent is regulated to >=11.0pH, then 0.1-1 pts.vol. of the precipitates is added to 1000 pts.vol. of the waste soln. to decompose the complex contained in the waste soln. into elementary metals or metallic salts which are precipitated. The precipitate is separated by filtration, and the heavy metal concn. is reduced to the effluent standard value of the works.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for treating wastewater, more specifically:
The present invention relates to a simple and economical method for treating plating waste liquid containing copper, nickel, or metal complexes such as cobalt, silver, and gold.

Prior Art and Problems Generally, plating solutions contain various chelating agents that create metal and lead bodies to stabilize them.

Therefore, the Metsuki factory generates wastewater containing complexes of metals such as copper and nickel with ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA), tartaric acid, and citric acid.

In recent years, printed wiring boards have been developed to make electronic devices smaller and lighter, and electroless plating (also known as chemical plating) technology has been applied to add conductivity to the through holes of plastic boards. There is.

This technology is also used for plating the surfaces of plastics, which are often used in automobile parts, home appliances, decorative items, etc.

Because glass is non-conductive, it was impossible to plate it with metal using the electrolytic plating method, but with the development of electroless plating, it became possible to treat the surface of decorative items and plastic products as a substitute for metals, and this technology became widely used. It's coming.

In electroless plating, aminocarboxylic acids such as EDTA; oxycarboxylic acids such as tartaric acid, citric acid, gluconic acid, and malic acid; malonic acid, Chelating agents such as carboxylic acids such as succinic acid and acetic acid are used. Among these, aminocarboxylic acids and oxycarboxylic acids form stable complexes with metal ions in the liquid, so it is difficult to separate and remove dissolved metals by coagulation-sedimentation treatment, which is commonly used in wastewater treatment. For this reason, river and soil contamination due to wastewater is often a problem.

Conventionally, methods for treating plating waste liquid include chemical treatment using hydrogen peroxide or the like, electrolytic oxidation treatment, and the like. In addition, as a method for treating wastewater containing heavy metal complexes, soluble iron salts or calcium salts are added to the wastewater to convert the heavy metal complexes into iron or calcium complexes, and the liberated heavy metals are precipitated and separated as hydroxides. Has there been any proposal for a replacement treatment method or a method for directly adsorbing heavy metal complexes onto activated carbon?These methods involve complicated treatment steps, and in addition, treatment of the iron or calcium complexes produced as by-products is time-consuming and expensive. It was not always satisfactory due to some shortcomings.

For example, JP-A No. 50-10780 discloses that by adding an excessive amount of calcium compound to a chemical cleaning waste liquid containing a complex of iron and citric acid, the metal content and citric acid content in the waste liquid are reduced to a poorly soluble form. A method is disclosed in which COD components are decomposed by simultaneously precipitating and separating the calcium salt, and further oxidizing the supernatant with hydrogen peroxide, perchloride, or the like.

However, this method requires considerable processing costs for dehydration, incineration, landfilling, etc. of the precipitate, and is problematic in terms of cost for industrial implementation.

In addition, JP-A-60-118 discloses that a waste liquid containing ethylenediaminetetraacetic acid, copper and formalin is heated,
The first step is to perform reduction using formalin contained in the waste liquid, add mineral acid to adjust the pH value of the liquid to 2.5 or less,
A second step in which ethylenediaminetetraacetic acid is precipitated and recovered, and a trivalent iron compound is added to the waste liquid from the first and second steps and then adsorbed with a chelate resin, or the first and second A method is disclosed in which the waste liquid that has passed through the process is adsorbed with a chelate resin that has adsorbed trivalent iron in advance, and the copper remaining in the waste liquid is removed in a third step. Since the process involves multiple steps: eluting the adsorbed copper with mineral acid and then treating the eluted copper with the usual coagulation-precipitation method, it requires complicated equipment and time, and has the disadvantages of high processing costs. be.

Furthermore, JP-A No. 60-118290 discloses that when treating wastewater containing complexes consisting of metals such as nickel, zinc, copper, and cobalt and various cleaning agents, 100 to 200 mg of nickel/ A method is disclosed in which metals are precipitated as oxides by adding a chlorinating agent at pH 7 to I2 in the presence of j2. However, with this method, if nickel is not present in the wastewater, it is necessary to add nickel salt, and the metal is likely to corrode.
In addition, since a chlorine compound that generates chlorine gas that is harmful to the human body is used as an oxide, there are problems such as deterioration of the durability of the device and the working environment.

Purpose As a result of studies to solve the problems of the conventional waste liquid treatment technology as described above, the inventor first discovered that copper, nickel,
After adjusting the pH of the waste liquid containing metal complexes such as cobalt, silver, and gold to 11 or higher with caustic alkali, at least 1 part by weight of sodium dithionite is added to 1 part by weight of the dissolved metal,
A method for treating waste liquid consisting of separating the produced precipitate was proposed (Japanese Unexamined Patent Publication No. 7894/1983). As a result of intensive research into simpler and more economical methods, we have discovered a method for treating plating waste liquid that is inexpensive and has no problems in terms of workability and work environment, and has completed the present invention.

Thus, according to the present invention, a waste liquid containing a copper complex is adjusted to pH 11 or higher with caustic alkali, and then treated with at least 1 part by weight of sodium dithionite per 1 part by weight of dissolved copper. 0.1 to 1 volume part of the precipitate obtained was adjusted to pH 11 or higher with a caustic alkali containing metal complexes such as copper, nickel, cobalt, silver, and gold.
Provided is a method for treating waste liquid, which comprises adding a volumetric portion of the liquid to react, and separating the resulting precipitate.

The feature of the present invention is that, first of all, after adjusting the waste liquid containing the copper complex to pH 1.1 or higher with caustic alkali, the dissolved metal
The point is to utilize the precipitate formed by adding at least 1 part by weight of sodium dithionite. The separated precipitate may be stored either wet or dry.

Next, after adjusting the pH of the waste liquid containing complexes of copper, nickel, cobalt, silver, gold, etc. to 11 or higher, the copper and copper sulfide etc. precipitated and separated as described above are added to 1,000 parts by volume of the waste liquid. 0.1-1 part by volume of a mixture of , alone or in combination with sodium dithionite, is stirred and reacted, and the precipitate formed is separated.

The waste liquid to be treated by the method of the present invention is a waste liquid containing complexes of metals such as copper, nickel, cobalt, silver, and gold, and is mainly a plating waste liquid from the electroless plating or electrolytic plating process of these metals. , or cleaning waste liquid discharged from the cleaning process of plating products taken out from the plating bath or the filtration and cleaning process during the cycle life of the plating bath. More specifically, for example: (a) copper, silver or gold;
Copper, silver or gold electroless plating waste containing EDTA, formalin and caustic soda: (b) Nickel, EDT
A, nickel plating waste liquid containing sodium citrate, ammonia and amine boron compound or hypophosphite;
(C) Cobalt plating waste liquid containing cobalt, sodium citrate, sodium hypophosphite, ammonium sulfate, etc. can be considered.

When these waste liquids are treated according to the method of the present invention, first, the copper plating waste liquid is adjusted to pH 11 or higher with caustic alkali.
Preferably, it is adjusted within the range of 11 to 13. The caustic alkali used for this pH adjustment may be added as is in the form of a solid powder, but it is convenient to add it in the form of an aqueous solution with a concentration of 5 to 50%, which is easier to work with.

Add sodium dithionite to the pH-adjusted waste solution and stir. The amount of sodium dithionite added is at least 1 part by weight per 1 part by weight of dissolved copper in the waste liquid,
This sodium dithionite can be used in the form of anhydrous salt or hydrosulfide.

By adding sodium dithionite, dissolved copper reacts with the sodium dithionite, and the dissolved copper precipitates as simple copper or sulfide.

The precipitate generated here is filtered using a filter press or the like, taken out as a cake, and stored in a wet state or in a dry powder state.

Next, the pH of the plating waste liquid discharged from the plating process is adjusted to 11 or more, preferably in the range of 11 to 13, using caustic alkali, and the above-mentioned stored wet or dry copper precipitate is added and stirred. do. The amount of the copper precipitate used here is at least 0.1 part by volume, and usually in the range of 0.1 to 1 part by volume, per 000 parts by volume of the waste liquid. Depending on the type of dissolved metal, if the addition of the copper precipitate alone does not sufficiently precipitate the dissolved metal, it is preferable to use sodium dithionite in combination.

The amount of sodium dithionite used here is generally in the range of 0.05 to 1 part by weight per 1 part by weight of the dissolved metal.

The single copper, gold or nickel salts, cobalt salts, silver salts, etc. that are produced form precipitates that are easy to separate, so they can be easily taken out as a case using a filter press or the like.

Although the above reaction can be carried out at room temperature, it is usually carried out at 20°C.
The reaction can be completed in a short time by heating to the above temperature, preferably within the range of 30° to 50°C.

The filter cake obtained by the method of the present invention as described above generally has a high metal content of about 40 to 80% and can be reused as a raw material for metal scouring. On the other hand, the filtrate after filtering out the precipitate has a metal ion concentration of 5 mg/β or less, and the COD value can be easily lowered by activated sludge treatment.

Next, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 Copper 1,300mg/j! , 30 mg/l of formalin and 6,400 mg/β of Rothsell salt, and adjusted to pH 12.5 with 48% caustic soda, was heated at 35°C while stirring twice the amount of hydrosulfide as the copper concentration.
When added, a copper-colored precipitate of metallic copper was produced.

After standing still for 2 hours, it was filtered to obtain a cake (hereinafter, the cake obtained here will be referred to as Keta A).

On the other hand, nickel 2,800mg/j2. Sodium borohydride 140mg/II! and EDTA2.200m
The plating waste liquid with a pH of 8-5 containing g/j2 was adjusted to pH 12.0 using 48% caustic soda.

Next, 1.5 parts of cake A obtained above was added to 81.000 parts of this nickel waste liquid at 30°C without stirring,
After standing for 2 hours, it was filtered to obtain a green cake.

The nickel concentration of the filtrate was determined by colorimetry and was found to be 3 "IIg/β
Therefore, it was confirmed that the present invention is extremely effective as a method for treating wastewater containing metal complexes.

On the other hand, the nickel content in the filtered cake was analyzed as 43
%Met.

Example 2 A nickel plating waste solution having the same composition as in Example 1 was maintained at 20°C and adjusted to pH 12°0 with 48% caustic soda. Next, to 1.000 parts by volume of this waste liquid, 1 part by volume of the cake AO obtained in Example 1 and 1 part by weight of dissolved nickel were added.
To this, 0.5 parts by weight of hydrosulfide was added and reacted with stirring at the same temperature. After standing still for 10 hours, it was filtered to obtain green particles. The nickel concentration in the filtration was colorimetrically determined to be 2 mg/β, indicating that this treatment method is excellent in treating waste liquid containing nickel complexes.

Example 3 Copper 1.800mg/j2. Formalin 3.5mg/j2
A plating waste solution containing 6.50 On+g/A of Rothsell's salt was adjusted to pH 12.0 with 48% caustic soda and maintained at 35°C.

To 1,000 parts by volume of this plating waste liquid, 0.05 parts by volume of the dry powder of Cake A obtained in Example 1 was added and reacted with stirring. After standing for 2 hours, it was filtered to obtain a dark red cake.

As a result of colorimetric determination of the copper concentration of the filtrate, it was 1 mg//2,
It was confirmed that this treatment method is excellent in treating waste liquid containing copper complexes. On the other hand, the copper content of the filtered cake was analyzed as 4
It was 7%.

Example 4 Silver nitrate 1,400 mg/β, 38% formalin 1 mj2
/11 alcohol 50 +nll/j2 and ammonia-containing plating waste liquid with a pH of 8.7 was adjusted to pH 11.5 using 48% caustic soda. Next, 0.6 parts by volume of the cake A obtained in Example I was added to 1000 parts by volume of the plating waste liquid kept at 28°C with stirring, and the mixture was allowed to stand for 2 hours to obtain a gray precipitate.

After that, it was filtered and the silver concentration of the filtrate was colorimetrically determined.
ng/l or less, confirming that this method is suitable for treating silver plating waste liquid.

Example 5 Cobalt2, 000 mg/1. , Dia 1,1
7 acid 5.000mg/l, sodium citrate 4,500m
g/β and ammonium sulfate 10.000 mg/l, and the pH was adjusted to 12.2 with 48% caustic soda.
To 0 part by volume, part by volume of the cake Al obtained in Example 1 was added without stirring to cause a reaction.

After standing for 2 hours, it was filtered to obtain a reddish-brown cake.

The cobalt concentration of the filtrate was measured colorimetrically and was found to be 2 mg/!
It was confirmed that this method is suitable for treating cobalt plating waste liquid.

Example 6 Gold chloride 2,500mg/β, tartaric acid 6,800mg/l
The plating waste liquid with a pH of 8.6 and containing 28 tng/1 of caustic soda was adjusted to pH 11.5 with 48% caustic soda.

Next, 95 parts by volume of the cake AO obtained in Example 1 was added to 1,000 parts by volume of plating waste liquid kept at 25 DEG C. with stirring to precipitate all the elements.

After standing for 8 hours, it was filtered to obtain a gold cake. As a result of colorimetric determination of the total concentration during filtration, it was less than 1 mg//2, confirming that this method is extremely effective as a treatment method.

Comparative Example 1 Nickel 2,800mg/β, sodium borohydride 140mg//! and EDTA 2,200 mg/β and pH 8.5 was adjusted to pH 12.0 using 48% caustic ivy.

Next, hydrosulfide in an amount 5 times the nickel concentration was added and reacted at 35°C. After standing for 2 hours, it was filtered to obtain a black cake (the cake obtained here is referred to as cake B). Next, copper 1.300mg/J, formalin 3
0 IIg/It and 6,400 mg/l of Lotusel salt, and adjusted to pH 12,0 with a 48% caustic sorter.
To 1,000 parts by volume of the plating waste liquid maintained at .degree. C., 4 parts by volume of the cake B obtained earlier was added with stirring.

Even after standing still for 20 hours, no copper precipitate was obtained, confirming that the product was unsuitable.

Comparative Example 2 Nickel 2.800+og/R1 sodium borohydride 1401og/l and EDTA 2.200mg/l
A plating waste solution containing β with a pH of 8.5 was adjusted to pH 12.0 using 48% caustic ivy. While maintaining this liquid at 40°C, the cake B obtained in Comparative Example 1 was mixed with 1.000% of the waste liquid.
1 volume part per volume part and 0.5 parts by weight of hydrosulfide per 1 part by weight of dissolved nickel were added with stirring.

After being allowed to stand still for 20 hours, the nickel concentration of the supernatant liquid, which produced a small amount of precipitate, was colorimetrically determined and found to be 2,500 mg/l, which confirmed that it was not suitable for waste liquid treatment.

As detailed above, in the present invention, copper plating waste liquid is adjusted to pH 11.0 or higher with caustic alkali, then hydrosulfide is added to obtain a precipitate of copper and copper sulfide, and this precipitate is A caustic alkali is applied to the metallurgical waste liquid containing a complex of copper, nickel, cobalt, silver, gold, etc. and a chelating agent generated from the metallurgical factory to a pH of 11.0 or higher, preferably P.
After adjusting to H11.0 to 13.0, the waste liquid was 1.000
Adding sodium dithionite alone or in combination at a ratio of 0.1 to 1 part by volume to part by volume, thereby decomposing the complex and precipitating it as an elemental metal or a metal salt, and then filtering it out. This method reduces the heavy metal concentration of the filtrate to below the factory discharge standard value, and is a method for treating plating wastewater with low treatment costs and good workability.

Claims (3)

[Claims] (1) After adjusting the waste liquid containing the copper complex to pH 11 or higher with caustic alkali, at least 1 part by weight of dissolved copper is added.
0.1 to 1 part by volume of the precipitate obtained by treatment with part by weight of sodium dithionite is heated to pH 1 with a caustic alkali containing a metal complex such as copper, nickel, cobalt, silver, or gold.
1. A method for treating a waste liquid, which comprises adding the waste liquid to 1,000 parts by weight of the waste liquid adjusted to a concentration of 1 or more, causing a reaction, and separating the resulting precipitate. (2) 0.1 to 1 part by weight of a precipitate obtained by adding sodium dithionite to a waste solution containing a copper complex and 0.05 to 1 part by weight of sodium dithionite per 1 part by weight of dissolved metal. The method according to claim 1, which is used in combination with. (3) The method according to claim 1, wherein the reaction is carried out at a temperature of at least 20°C.