KR100758461B1 - Method for reuse of wastewater in continuous electroplating lines - Google Patents

Abstract

The present invention relates to an electroplating wastewater recycling method generated in a continuous electroplating process having a soluble anode,

Concentrate the secondary wastewater generated during the continuous electroplating process with a reverse osmosis filter, recycle the filtered water to industrial water, transfer the concentrate with the plating wastewater to the reaction tank, neutralize with alkali salts, and filter the metal hydroxide. An electroplating wastewater recycling method is provided in which a slurry is removed and transferred to a plating solution circulation tank to recycle conductive additives and additives of oil value present in the plating wastewater to a plating process.

According to the present invention, the electroplating wastewater generated in the continuous electroplating process having a soluble anode is passed through the reverse osmosis filter, the filtered water is used as recycled water, and the concentrate is continuously contained in the plating wastewater by neutralization treatment and removing the slurry. Conductive aids and additives can be recovered and recycled into the plating process.

Plating wastewater, recycling, continuous electroplating, fusible anode, reverse osmosis filter

Description

Recycling method for electroplating wastewater generated in continuous electroplating process with soluble anodes {METHOD FOR REUSE OF WASTEWATER IN CONTINUOUS ELECTROPLATING LINES}

1 is a flowchart showing a plating wastewater recycling process of the present invention.

The present invention relates to an electroplating wastewater recycling method, and more particularly, the filtered water obtained by passing the electroplating wastewater generated in a continuous electroplating process having a soluble anode through a reverse osmosis filter is used as recycled water, and the concentrate is neutralized. And it relates to a method for recycling the conductive auxiliary and additive components contained in the plating waste water by removing the slurry.

Continuous electroplating processes having a soluble anode include zinc-based alloy plating processes such as zinc plating, zinc-iron, zinc-nickel and zinc-cobalt, and tin plating processes. The plating wastewater of the continuous electroplating process is contaminated by the plating liquid disposed in the plating process or the plating liquid deposited on the strip during the washing of the strip. Therefore, these plating waste liquors contain metal ions, conductive aids and plating additives. In particular, since these plating solutions are acidic plating baths, the amount of metal ions dissolved in the positive electrode is greater than that of metal ions reduced in the negative electrode during plating. The reason is that the metal is dissolved by the electrical reaction at the anode, but the gas is generated as the metal is dissolved by the substitution reaction with hydrogen ions, and the reduction of the hydrogen ions is performed in addition to the reduction of the metal ions at the cathode. This is because there is a difference between the amount of reduction and the amount of oxidation at the anode and the difference is more than the amount of metal that is buried out of the strip. Therefore, in order to perform the normal plating operation, it is necessary to continuously discard a part of the plating liquid. When the plating liquid is discarded, the salts or additives of the conductive auxiliary material present therein are also discarded. Potassium chloride is used in the chloride-based acidic plating solution and sodium sulfate is used in the sulfuric acid-based plating solution as a conductive auxiliary material. As the additive, PEG (polyethylene glycol) in the case of zinc and zinc-based alloys, PSA (phenol sulfonic acid) or MSA (methanesulfonic acid) in the case of tin plating solution are used. In particular, in the continuous electroplating process, the plating liquid is buried in the strip and flows out of the plating cell. The washing process mainly consists of the first washing with acidic solution of pH 0.5-1.5 and the second washing with deionized water. The wastewater from the first wash usually contains 3,000 ~ 10,000ppm, and the wastewater from the second wash contains about 100 ~ 500ppm metal ions for plating.

In general, the plating wastewater treatment of the continuous electroplating process removes metal ions into a slurry of metal aquatic products by neutralization and separates them with a filter, and the additives are removed by adsorption by activated carbon or by decomposing organic matter by adding an oxidizing agent. In addition, the ions of the conductive auxiliary salt are discharged out of the state contained in the discharge. In this case, the conductive additives and additives are not recycled and disposed of.                         

Meanwhile, Korean Patent Application No. 99-32745 discloses a method of separating plating wastewater into treated water and concentrate using an electrodialysis apparatus and an evaporative concentrator, converting the concentrate into a plating solution, and recycling the treated water into industrial water. have. However, this method is applicable to plating processes with insoluble anodes, but is not suitable for application to plating processes with soluble anodes. The reason for this is that in the plating process having a soluble anode, the concentration of metal ions for plating is increased, and therefore, a larger amount of plating liquid must be discarded, and conductive auxiliary salts or additives must be disposed of in this process.

Accordingly, an object of the present invention is to provide a method for recycling electroplating wastewater generated in a continuous electroplating process having a soluble anode.

According to one aspect of the invention,

Separating the secondary waste washing liquid generated during the continuous electroplating process having a soluble anode and undergoing primary and secondary washing with a reverse osmosis filter to be separated into filtrate and concentrate;

Recycling the filtered water into industrial water; And

The concentrate is transferred to a reaction tank together with a waste washing solution containing a primary waste washing solution generated during the continuous electroplating process, neutralized with alkali salts and filtered to remove slurry of the metal hydroxide, and the filtered water is transferred to a plating solution circulation tank. Recycling the conductive additives and additives of oil value present in the plating wastewater to the plating process;

Provided is an electroplating wastewater recycling method comprising a.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention concentrates the secondary wastewater in the wastewater generated in the continuous electroplating process having a soluble anode with a reverse osmosis filter to use the filtered water as recycled water, and the concentrated solution into the reaction tank together with the plating wastewater containing the primary wastewater. Neutralization treatment is carried out by adding alkali salts to neutralization, and the slurry of metal hydroxide is removed by a filter, and the filtered water is transferred to a plating solution circulating tank to reuse conductive additives and additives present in the plating wastewater.

The electroplating wastewater recycling process of this invention is shown in FIG.

According to the electroplating wastewater recycling process of the present invention, first, the secondary wastewater washing liquid generated in the continuous electroplating process having a soluble anode is concentrated with a reverse osmosis filter and separated into filtered water and a concentrate.

In general, a continuous electroplating process having a soluble anode undergoes a first washing and a second washing, among which 100 to 500 ppm of metal ions are present in the second washing liquid. If the secondary waste water is concentrated through a reverse osmosis filter 10 times, the concentrated water becomes 1/10 of the initial capacity and the concentration of metal ions present in the water increases by 10 times. And, the amount of permeate filtered water is reduced to 9/10 of the initial capacity, and the concentration of metal ions is reduced to 10 ppm or less. Therefore, the filtered water of the secondary wastewater passed through the reverse osmosis filter may be used again as the first wash, or may be used as a roll washing solution during the plating process. Preferably the permeate filtered water has a metal ion concentration of 100 ppm or less. In this case, the reason why the reverse osmosis filter is used at the time of concentration is that the metal ions and the organic additives can easily be concentrated when passing through the ion membrane and are economically inexpensive. The concentration of the secondary waste washings is preferably concentrated 8-12 times, more preferably 9-11 times and most preferably 10 times. If the concentration is excessively excessive, the metal salt is concentrated in the ion membrane of the reverse osmosis filter, thereby decreasing the permeation efficiency and increasing the concentration of metal ions in the permeated water, thereby improperly reducing the water quality of the filtered filtrate. Too little concentration is economically inefficient.

As described above, the filtered water passed through the reverse osmosis filter may be used as the first washing liquid or may be recycled as industrial water of the process used for the roll washing liquid of the plating process.

On the other hand, the concentrated liquid obtained by concentrating the secondary waste washings with a reverse osmosis filter, as shown in Figure 1, is joined to the other waste plating liquid containing the primary waste washings are transferred to the reaction tank. Thereafter, an alkali salt is added to the reaction tank to neutralize the solution, followed by filtration to remove the slurry of the metal hydroxide. At this time, the neutralization treatment is in the range of pH 6-8, preferably 6.5-6.5. Then, the filtered water is transferred directly to the plating solution circulation tank or concentrated by transfer to a vacuum evaporator and then to the plating solution circulation tank. The filtrate thus obtained is in a neutral state in which the slurry of the metal hydroxide is removed and contains valuable conductive additives and other additives and can be recycled in the plating process. The filtered water may be repeatedly circulated throughout the plating process as shown in FIG.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

Example

As shown in Table 1, the secondary waste washing liquid generated in the continuous electroplating process having the soluble anode using the plating solution of the following three plating systems was treated according to the process of the present invention and the concentration of each component was measured.

The concentration of the plating liquid component of each plating system was measured, and the second waste water discharged from each process was self-manufactured using a reverse osmosis filter (BW30-8040 membrane manufactured by Dow Chemical Co.) at a feed rate of 10 m 3 / hour. Permeate through the reverse osmosis filter), and concentrated 10 times, and compared the concentration of each component in the filtered filtrate.

The concentrated solution of 10-fold water obtained by treatment with the reverse osmosis filter was neutralized by adding an alkali salt in a reaction tank. At this time, the alkali salt was used potassium hydroxide in the case of zinc and zinc-iron plating system, sodium hydroxide in the case of tin plating system, and the pH was adjusted to 6.5-7.5 range. The neutralized reactant was then filtered through a pressurized filter (a pressurized filter self-made with a filter cloth of phenol resin capable of filtering 1 micron or more) to remove slurry of metal hydroxide.

The concentration of each component of the resultant was measured and compared with before treatment. Each measurement result is shown in Table 1 below. The filtrate was evaporated and concentrated 5 times, 10 times, and 10 times with respect to the wastewater of the zinc, zinc-iron, and tin plating solutions, respectively, to be used as the plating solution.

  Plating system   Plating solution concentration (ppm) The concentration of filtrate (ppm) before and after the reverse osmosis filter treatment of the secondary wastewater Concentration before and after neutralization and slurry removal treatment of the concentrate obtained by the reverse osmosis filter treatment of the secondary wastewater (ppm) Before treatment After treatment Before treatment After treatment zinc ZnCl ₂ 15,000 200 5 6,000 20 KCl 30,000 350 3 7,500 7,400 PEG 100 12 One 45 42 Zinc-iron ZnCl ₂ 15,000 180 16 1,400 12 FeCl ₂ 2,000 80 8 600 7 KCl 30,000 330 32 3,000 2,800 PEG 300 43 4 180 175 Remark SnCl ₂ 40,000 260 30 2,500 8 Na ₂ SO ₄ 50,000 330 32 3,100 3,050 PSA 200 41 3 34 31

As shown in Table 1, when the secondary wastewater generated in the continuous electroplating process according to the present invention, the filtered water filtered by the reverse osmosis filter is reduced to less than 100ppm metal ion industrial water of the plating process In addition, the neutralization and slurry removal treatment of the concentrate obtained by reverse osmosis filter treatment was carried out, and most of the conduction aids (KCl and Na ₂ SO ₄ ) and additives (PEG and PSA) were recovered and recycled. .

In the method of the present invention, the electroplating wastewater is passed through a reverse osmosis filter, and the filtered water is used as recycled water. Can be recycled.

Claims (3)

Separating the secondary waste washing liquid generated during the continuous electroplating process having a soluble anode and undergoing primary and secondary washing with a reverse osmosis filter to be separated into filtrate and concentrate; Recycling the filtered water into industrial water; And The concentrate is transferred to a reaction vessel together with the plating wastewater containing the primary wastewater generated during the continuous electroplating process, neutralized with alkali salts and filtered to remove slurry of the metal hydroxide, and the filtered water is transferred to a plating solution circulation tank. Recycling the conductive additives and additives of oil value present in the plating waste water in the plating process; Electroplating wastewater recycling method comprising a. The method of claim 1, wherein the filtered water in the first step is characterized in that the metal ion concentration of 100ppm or less. The method of claim 1, wherein in the third step, the filtrate is concentrated by using a vacuum evaporator and then transferred to the plating solution circulation tank.

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