JPS5823154B2 - Metsuki Haisu Inoshiyorihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating plating wastewater and recovering heavy metals.

Generally, wastewater from the plating process contains heavy metal ions such as copper, nickel, chromium, zinc, lead, and cadmium, as well as precious metal ions such as gold and silver. Alternatively, the current situation is to perform neutralization, coagulation and sedimentation treatment, and then discharge the water to a water quality that is below a certain discharge standard.

Also, in the plating process, a large amount of washing water is used in the washing process, but in order to make effective use of water, a closed system has been put into practical use that treats the washing wastewater of each plating process with ion exchange resin. After filling the column and adsorbing heavy metal ions, the heavy metal ions are eluted with an eluent to regenerate the ion exchange resin, and the eluent is neutralized and coagulated and precipitated to convert the heavy metal ions into hydroxides. A method of processing sludge is generally widely used.

However, in the method using ion exchange resin, the diameter is about 30 mm.
Because of the spherical particles of 0 to 1200μ, there is generally a difference in the ion diffusion mechanism between the surface and the inside, and there is a distribution in the rate of adsorption and elution of heavy metal ions.In adsorption, as the liquid passing rate increases, the through-current capacity increases. On the other hand, elution has the disadvantage that the amount of eluent is large, the elution time is long, and regeneration requires a long time.

Furthermore, in the ion exchange resin method, the eluent is often neutralized, and the neutralized coagulation and sedimentation requires a large amount of alkali and coagulant, as well as acid for pH adjustment. There are many problems in terms of pollution and resource conservation associated with treatment.

In order to solve these problems with the ion exchange resin method, the present inventors conducted research on plating wastewater treatment using fibrous ion exchangers and chelate formers, and arrived at the present invention.

That is, the present invention provides a process for treating plating wastewater with a fibrous material having a single fiber diameter of 5 to 150 μm having ion-exchange ability or chelate-forming ability to adsorb heavy metal ions in the plating wastewater to the fibrous material, The present invention provides a method for treating plating wastewater, which comprises a step of eluting the fibrous material that has adsorbed ions, or a step of electrolytically recovering heavy metal ions in the eluent using an insoluble anode and a cathode.

According to the present invention, electrolytic recovery of heavy metals is easier than with the ion exchange resin method, and unlike the conventional neutralization coagulation precipitation method, heavy metal sludge is not generated, making it an extremely effective method.

Further, according to the present invention, it is not necessarily necessary to perform electrolytic recovery of heavy metals, and it is of course possible to convert heavy metals into sludge by neutralizing and coagulating and precipitating the eluent as in the conventional method.

Furthermore, the effluent obtained by treating washing wastewater according to the present invention can be reused as washing water, making it possible to recycle washing water and save water.

The single fiber diameter of the fibrous material having ion exchange ability or chelate forming ability used in the present invention is 5 to 150μ, preferably 1
0 to 100μ, single fibers less than 5μ are unsuitable if fiber strength is required, and fibers exceeding 150μ cause ion adsorption and ion diffusion on the surface and inside in the case of elution, similar to ion exchange resins. This is not preferable because it tends to cause a speed difference.

The fibrous material having ion exchange ability or chelate forming ability used in the present invention is generally preferably made of synthetic fiber from the viewpoint of chemical resistance, such as polyvinyl alcohol fiber, acrylic fiber, polyvinyl chloride fiber, Polyvinylidene chloride fibers, phenol fibers, polystyrene fibers, etc. can be widely used.

Carboxyl groups (-COOH), sulfone groups (-3O3H), secondary amine groups, tertiary amine groups, quaternary ammonium groups, polyethylene polyamino groups (
-NH(CH2CH2NH)nH) ion exchange group or chelate forming functional group is introduced.

The fibrous material can be in various shapes such as short fibers, cloth, felt, tow, etc., and has a much greater degree of freedom in handling than particulate ion exchange resins or chelate resins. It's advantageous.

In the present invention, the above-mentioned fibrous material having ion exchange ability or chelate forming ability is immersed in plating wastewater in an appropriate form and brought into contact with the material for a sufficient time to adsorb heavy metal ions for treatment.

As a treatment method, any method can be used, such as making it into a cotton-like material and throwing it into wastewater, packing it into a column or passing it through a filter, or making it into a fabric and immersing it in wastewater.

Further, the treatment format can be changed as appropriate depending on the type of ion exchange group and chelate-forming functional group.

It is of course possible to discharge the treated effluent or to reuse it as washing water.

The fibrous material on which heavy metal ions have been adsorbed by such treatment can be treated with an eluent such as hydrochloric acid, sulfuric acid, caustic soda, and sodium hydroxide to elute the heavy metal ions from the fibrous material.

According to the method of the present invention, heavy metal ions can be efficiently eluted from fibrous materials, can be eluted with a smaller amount of eluent than in the ion exchange resin method, and can be electrolytically recovered at the same time as the elution.

Next, it is preferable to recover the heavy metal ions in the eluent by an electrolytic method, since this eliminates the need for sludge treatment.

The ion exchange resin method requires a large amount of eluent in the elution process, the elution time is long, and the concentration of heavy metal ions in the eluent tends to be low.Even in electrolytic recovery, electrolysis requires a long time. do.

However, the present invention is characterized in that elution can be performed with a small amount of eluent, the elution time is short, and electrolytic recovery can be performed at the same time as elution, so that the electrolytic reaction can be carried out efficiently.

As the insoluble anode used for electrolytic recovery, platinum, titanium, lead peroxide, etc. are used, and as the insoluble negative ffl plate, platinum, aluminum, stainless steel plate, etc. are used.

The present invention will be explained below with reference to Examples.

Example 1 A single acrylic fiber with a diameter of 40μ made of a copolymer of 48% by weight of acrylonitrile and 52% by weight of vinyl chloride was heated and hydrolyzed in a caustic soda aqueous solution, and the amount of cation exchanged was 7.2 meq/y (dry f 1ber)
A-type weakly acidic cation exchange fiber (WK) was obtained.

This cation exchange fiber was cut into a length of 2 mm using a cutter to obtain chopped fiber.

On the other hand, 23.5775 g of copper sulfate was dissolved in distilled water and
An aqueous solution (pH 4, 6) was prepared.

The copper ion (Cu2+) concentration in this aqueous solution is 300
ppm, and corresponds to the washing wastewater from the first washing tank taken out from the plating bath.

This copper sulfate solution was mixed with 53 g of Na-form WK (dry f
SV (space velocity) from the top of an acrylic resin column (inner diameter 20 mm, length 900 m/m) packed with 1 ber equivalent) at an exchange density of 0.2 jq/rrtl.
No copper ions were detected in the effluent.

Next, 5% sulfuric acid aqueous solution 1
00771/ was passed through SV6, the effluent was placed in a 300 m/beaker (electrolytic cell), and a column was placed using platinum plates (30 mm x 30 m, 71 V x 0.3 platinum plates) for both negative and positive poles.
Electrolytic tank direct connection method, current density 2A/dm2, liquid temperature 25℃
While recovering the copper ions in the electrolytic cell, the liquid was passed through the column using a pump and circulated, and the copper was electrolytically recovered at the same time as the elution. The final copper recovery rate was 99.99.

Comparative Example 1 In Example 1, Amberlite I manufactured by Organo ■ was used as a weakly acidic cation exchange resin instead of the weakly acidic cation exchange fiber.
RC-84 (Na type) (exchange capacity 9.2meq/&)
42 g (dry resin equivalent) with a packing density of 0
-4! /rnl into an acrylic resin column, and
A sulfuric acid steel solution 207 containing 00 ppm copper ions was passed through at 5V20 to adsorb copper ions, and then a 5% sulfuric acid aqueous solution (1140 m/ml) was passed through at SV6, and elution and electrolytic recovery were carried out in the same manner as in Example 1. At the same time, the steel recovery rate was 80%.
Up to this point, the current efficiency was 96%, and the final copper recovery rate was 99.9%.

Example 2 A single acrylic fiber with a diameter of 75 μm made of a copolymer containing 90% by weight of acrylonitrile and 10% by weight of vinyl bromide was treated with triethylenetetramine.

Anion exchange capacity 6.9 meq 7g (dry f
iber) weakly basic anion exchange fiber (WA) was obtained.

This WA was washed with water, cut into 1 mm pieces with a cutter, and then
．． Conditioning was performed in OH form with a 5N-NaOH aqueous solution.

This WA has an anion exchange ability as well as a chelate forming ability with heavy metal ions.

On the other hand, 7.05 g of cuprous cyanide, 11.57 g of sodium chloride
251 was prepared by dissolving y in distilled water.

This solution contains 200 ppm of copper ions.

OHH type K was conditioned into H type with a 5% hydrochloric acid aqueous solution, and this H type WK 55g (dryfiber conversion)
with a packing density of 0.2 g/ml, an inner diameter of 20 yn, and a length of 1
It was packed into a 100 mm acrylic resin column to serve as a first column.

Separately OHH type A 23 j! (dry f 1ber
(converted) was packed into an acrylic resin column with an inner diameter of 20mm and a length of 500mm to form a second column.

The lower end of the first column and the upper end of the second column were connected with a vinyl chloride resin tube, and a copper sodium cyanide aqueous solution 257 with a copper ion concentration of 200 ppm was passed through the top of the first column at 5V21. The copper cyanide ions were completely adsorbed on the WA, and then the copper cyanide ions were completely eluted with 5 ml of NaCN aqueous solution until the copper ion concentration was 2.
0 g# of eluent was obtained.

Put 250 rnl of this eluent into a beaker of 5007717, use a lead peroxide plate as the anode and a stainless steel plate as the cathode, and put it on the cathode plate while stirring with a magnetic stirrer at a current density of 2A/dm2 and a liquid temperature of 25°C. 99 copper
．． 99% recovery was achieved.

The current efficiency was 97% at a silver recovery rate of 80.

Comparative Example 2 In Example 2, instead of the cation exchange fiber (WK), Amberlite J RC-84 (conditioned into H type) of Comparative Example 1 (52 idryre sin equivalent) was used at a packing density of 0.4jj/ml. This was then packed with an acrylic resin column T to form a first column.

Separately, instead of the anion exchange fiber (WA) of Example 2, a weakly basic anion exchange resin Diaion W manufactured by Mitsubishi Chemical Corporation was used.
A-21 (OH type, anion exchange capacity 5.98 meq/
g) 27 g (dry resin equivalent) was packed into an acrylic resin column at a packing density of 0.38 g/ml,
This was the second column.

The lower end of the first column and the upper end of the second column are connected with a vinyl chloride resin tube, and copper sodium cyanide 251 with a copper ion concentration of 200 ppm is poured from the top of the first column.
was passed through the solution at 5V20 to completely adsorb the copper cyanide ions to the diamond ion WA-21, and then the 5V NaCN
The aqueous solution was passed through the top of the column at SV2 to completely elute the copper cyanide ions, thereby obtaining an eluent with a copper ion concentration of 14 g/l.

360rnl of this eluent was placed in a 500m beaker and electrolyzed using a lead peroxide plate as the anode and a stainless steel plate as the cathode at a current density of 2 A/dm and a liquid temperature of 250C while stirring with a magnetic stirrer. , 99.9% of the copper was recovered in the cathode plate.

The current efficiency was 80% until the shell recovery rate was 70%.

Example 3 The weakly acidic cation exchange fiber used in Example 1 was conditioned into an H shape (WK) to treat the washing water after copper birophosphate plating.

The plating washing water contained 20 ppm of copper ions and had a pH of 89.

Next, the H type WK65g (dry fiber conversion) is 0
．． A column was packed with a packing density of 297 ml, and plating washing water 5001 was passed through the top of the column at 5V21 to completely adsorb copper ions, and then a 5th column sulfuric acid aqueous solution was passed through SV.
At step 2, the solution was passed from the top of the column to completely elute the copper ions, and an eluent with a copper ion concentration of 20 g/l was obtained.

Pour 500 m of the eluent of the above into a beaker No. 11, electrolyze it using a platinum plate (50 mm x 50 mwt x 0.3 mm) as a cathode and anode plate at a current density of 2 A/dm2 and a liquid temperature of 25°C while stirring with a magnetic cooler. Copper 99.9% for the cathode plate.
99% recovery was achieved.

The current efficiency was 96 degrees up to a silver recovery rate of 80.

Comparative Example 3 In Example 3, Diaion WK 10 manufactured by Mitsubishi Chemical Industries, Ltd. (Hu, cation exchange capacity 8.9 meq/, F (dry resin)) was used as the weakly acidic cation exchange resin.
71 g (dry resin equivalent) with a packing density of 0.3
When the column was filled with 9 g/ml and the washing water 5007 of the birophosphate copper plating of Example 3 was passed from the top of the column at 5V20, copper ions were detected in the effluent from around 1501, Since leakage of copper ions started, the flow of liquid was stopped.

From the above Examples and Comparative Examples, the fibrous material of the present invention adsorbs and elutes heavy metal ions more easily than ion exchange resins or chelate resins, and electrolytically recovers heavy metals from the eluent. This can be done with a small amount of eluent, and it is a new treatment method in terms of pollution control and resource conservation, and the equipment can be made lighter and smaller, which has great industrial significance.

Claims (1)

[Claims] 1. A step of treating plating wastewater with a fibrous material having a single fiber diameter of 5 to 150 μm having ion exchange ability or chelate forming ability to adsorb and remove heavy metal ions in the plating wastewater, and removing the fibrous material that has adsorbed heavy metal ions. A method for treating plating wastewater that consists of a process of treating it with an eluent to elute heavy metal ions.