JP3028391B2 - Treatment of plating waste solution - 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 treating a plating waste liquid.

[0002]

2. Description of the Related Art As shown in FIG. 2, a treatment apparatus for carrying out a conventional plating waste liquid treatment method includes a plating step (31).
A washing water storage tank (32) for storing waste water such as cyan washing water, chromic acid washing water, and acid / alkali washing water,
A filtration device (33) for filtering waste liquid sent from the washing water storage tank (32), a cation exchange tower (34) and an anion exchange tower (35) for removing ions in the waste liquid after filtration, Plating process
An alkaline eluent storage tank (36) for storing cyan-alkali waste liquid from (31), an acid eluent storage tank (37) for storing chromic acid-acid waste liquid, and an alkaline eluent storage tank for these. (36) and a reaction tank (38) for mixing and reacting the waste liquid sent from the acid-based eluent storage tank (37), and a reaction tank (38)
A sedimentation tank (39) for sedimenting the precipitate generated in the above, a drying furnace (40) for evaporating and drying the sediment, and a pH adjusting tank (41) for adjusting the pH of the waste liquid passed through the sedimentation tank (39). It is composed of

[0003] In the case of treating a plating waste liquid using the above-described processing apparatus, a waste liquid having a low concentration of contained components such as cyanine washing water, chromic acid washing water, and acid / alkali washing water is recycled to purified water. On the other hand, concentrated waste liquids such as cyan-alkali waste liquid and chromic acid-acid waste liquid are drained without being recycled.

That is, waste liquids such as cyan water, chromic acid water, and acid / alkali water are temporarily stored in a water tank.
After being collected in (32) and reaching an appropriate amount, it is sent to a filtration device (33) to remove solids, and then the cation component is removed in a cation exchange column (34), and then the anion exchange column. In (35), the anion component is removed, and finally purified water is regenerated. Then, the purified water is sent again to the plating step (31) and reused. On the other hand, the washing wastewater in the filtration device (33) is sent to a reaction tank (38), and each eluent exiting from the cation exchange tower (34) and the anion exchange tower (35) is also an acid-based eluent storage tank ( Once stored in the eluent storage tank (36) and the alkaline eluent (36), it is sent to the reaction tank (38).

On the other hand, a cyan-alkali waste liquid and a chromic acid-acid waste liquid, which are not subjected to the regeneration treatment of purified water, are temporarily stored in an alkaline eluent storage tank (36) and an acid eluent storage tank (37). The wastewater is sent to the reaction tank (38), where it is mixed with the waste liquids sent from the regeneration treatment step. Next, the treated waste liquid reacted in the reaction tank (38) is sent to a settling tank (39), and the sediment settled here is sent to a drying furnace (40) to be solidified and disposed of as sludge. The remaining processing waste liquid is sent to a pH adjusting tank (41) to be neutralized, and then discharged.

[0006]

In the case of the above-mentioned conventional treatment method, the recovery of purified water is low because the purified water cannot be recycled with respect to the cyan-alkali waste liquid or the chromic acid-acid waste liquid. There is. Also, in the regeneration treatment of cyanine washing water, chromic acid washing water, etc., the filtration device (33), cation exchange tower (34) and anion exchange tower (35)
, And a certain amount of time was required for processing in each of these devices. In addition, an alkali for storing each processing waste liquid after treatment in the washing water storage tank (32) for storing the above-mentioned cyan washing water and the like, the cation exchange tower (34) and the anion exchange tower (35). Eluent storage tank (36) and acid eluent storage tank (3
7) is also required, so the processing equipment itself becomes large,
There was also a disadvantage that the installation required a large space.

[0007] An object of the present invention is to provide a high recovery rate of purified water,
In addition, it is an object of the present invention to provide a plating waste liquid treatment method which does not require a washing water storage tank such as a cyan washing water or an acid / alkali eluent storage tank in the regeneration treatment of the waste liquid.

[0008]

According to the present invention, there is provided a method for treating a plating effluent, wherein a chromic acid-based effluent of a chromic acid-based, a cyan-based, and an acid / alkali-based effluent from a plating process is converted to hexavalent chromium. Treated with a hexavalent chromium conversion device that converts to trivalent chromium or a hexavalent chromium recovery device that recovers hexavalent chromium, and treats this wastewater that does not contain hexavalent chromium with other cyanogen-based and acid-alkali-based wastewater and After each washing water is mixed in a mixing tank, this mixed waste liquid is separated into distilled water and concentrated water by an evaporator, and the distilled water is purified and then reused in the plating process, while the concentrated water is discharged. is there.

Further, in the above-mentioned treatment method of the present invention, the purification treatment of distilled water discharged from the evaporator is performed by using a reverse osmosis device.

Further, in any of the above-mentioned treatment methods according to the present invention, at least one of the waste liquid at the bottom of the mixing tank, the concentrated water discharged from the evaporator, and the concentrated water discharged from the reverse osmosis device is treated with sludge by an evaporator to dryness. It is discarded after it has been converted.

In the present invention, examples of the evaporator include a vapor compression evaporator and a multiple effect evaporator. Examples of the vapor compression type evaporator include a mechanical vapor compressor using a turbo compressor and a vapor compressor using an ejector.

[0012]

According to the treatment method of the present invention, concentrated waste liquids of chromic acid type, cyanide type and acid / alkali type are also concentrated by the evaporator to regenerate purified water. Recovery rate is greatly improved. In addition, since all waste liquids are mixed in the mixing tank and then continuously concentrated by the evaporator, the washing water storage tank for storing cyanine washing water and the eluate after each ion exchange are collected as in the past. An acid-based and alkaline-based eluent storage tank may be omitted. Further, a filtration device, a cation exchange column, an anion exchange column, and the like, which are conventionally essential, are also omitted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for treating a plating waste liquid according to the present invention will be described below.

FIG. 1 shows a float chart of the treatment method of the present invention, wherein (1) is a plating step in which a waste liquid to be treated is discharged, and (2) is a chromic acid-based and cyan-based acid discharged from the plating step (1). And a hexavalent chromium conversion tank for converting harmful hexavalent chromium components contained in chromic acid-based waste liquids to harmless trivalent chromium components, among waste liquids composed of acid and alkali,
(3) is the treated waste liquid after conversion to the above trivalent chromium component,
Cyan washing water and acid / alkali washing water and cyan-
Mixing tank for mixing alkaline waste liquid and acid waste liquid, (4)
Is a vapor compression evaporator that evaporates and concentrates the mixed effluent sent from the mixing tank (3), (5) is a reverse osmosis device that removes volatile components in distilled water from the vapor compression evaporator (4),
(6) is an evaporating and drying device for evaporating and solidifying the precipitate reacted in the mixing tank (3), the concentrated water discharged from the vapor compression evaporator (4) and the concentrated water discharged from the reverse osmosis device (5).

Next, the method for treating a plating waste liquid according to the present invention will be described in detail. First, of the waste liquid discharged from the plating step (1), the waste liquid containing hexavalent chromium is converted into a hexavalent chromium conversion tank (2). The waste liquid is sent to the mixing tank (3) after the harmful hexavalent chromium component is converted into a harmless trivalent chromium component. In addition, other waste liquids not containing hexavalent chromium discharged from the plating step (1), that is, cyanic washing water and acid / alkali washing water, and cyan-alkali wastewater and acid-based wastewater are also sent to the mixing tank (3). Here, the trivalent chromium is mixed with the waste liquid after conversion. The nature of the waste liquid in the mixing tank (3) is not particularly limited, and it is not necessary to adjust the supply amount of each waste liquid so that it becomes neutral. The waste liquid mixed in the mixing tank (3) is sent to a vapor compression evaporator (4) to be evaporated and concentrated. The distilled water recovered by the vapor compression evaporator (4) is sent to a reverse osmosis device (5) to remove volatile components, and then sent to a plating tank (1) again for reuse. The sediment that has settled by reacting when mixed in the mixing tank (3), concentrated water from the vapor compression evaporator (4), and concentrated water from the reverse osmosis device (5) are each evaporated to dryness ( 6) After being sent to remove water
Discarded as sludge.

In the present invention, a vapor compression type evaporator
In place of (4), a multi-effect concentrator may be used. The operation at this time is the same as that when the vapor compression type evaporator (4) is used.

A hexavalent chromium recovery and concentration device (7) may be used in place of the hexavalent chromium conversion tank (2). In this case, the recovered hexavalent chromium is sent to the plating process again,
The economy is improved. On the other hand, the discharged concentrated water is
Sent to (3).

[0018]

According to the plating waste liquid treatment method of the present invention, it is possible to regenerate purified water even for concentrated waste liquid such as cyan-alkali waste liquid and chromic acid-acid waste liquid. The recovery rate is greatly improved. Also,
All waste liquids are mixed in a mixing tank and then continuously concentrated by an evaporator.Therefore, a washing water storage tank for storing cyanine washing water, etc. and an acid / alkali system for storing treated water after each ion exchange Each eluent storage tank and the like can be omitted. Further, since a filtration device, a cation exchange column, an anion exchange column, and the like, which are conventionally essential, are also omitted, the required space of the entire processing apparatus can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of a plating waste liquid treatment method according to the present invention.

FIG. 2 is a flowchart showing a conventional example of a method for treating a plating waste liquid.

[Explanation of symbols]

 (1) Plating process (2) Hexavalent chromium conversion equipment (3) Mixing tank (4) Evaporation equipment (5) Reverse osmosis equipment (6) Evaporation and drying equipment (7) Hexavalent chromium recovery equipment

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-49-129360 (JP, A) JP-A-51-125954 (JP, A) JP-B-44-11872 (JP, B1) (58) Field (Int.Cl. ⁷ , DB name) C02F 1/58-1/64 C02F 1/02-1/18

Claims (3)

(57) [Claims] 1. A hexavalent chromium conversion device for converting hexavalent chromium into trivalent chromium, or a hexavalent chromium conversion apparatus, among the chromic acid-based, cyanic, and acid / alkali-based waste liquids from the plating step. Treat with a hexavalent chromium recovery unit that recovers chromium, and treat this wastewater that does not contain hexavalent chromium with other cyanogen-based and acid / alkali-based wastewater and each water wash
After mixing the water in a mixing tank, the mixed waste liquid is separated into distilled water and concentrated water by an evaporator, and the distilled water is purified and then reused in the plating process, while discharging the concentrated water. Method of treating plating waste liquid. 2. The method for treating a plating waste liquid according to claim 1, wherein the purification treatment of the distilled water discharged from the evaporator is performed using a reverse osmosis device. 3. The method according to claim 1, wherein at least one of the waste liquid at the bottom of the mixing tank, the concentrated water discharged from the evaporator, and the concentrated water discharged from the reverse osmosis device is sludge-formed by an evaporator and then discarded. 2. The method for treating a plating waste liquid according to 2.