JPH0310100A - Method and device for removing ferric ion and iron hydroxide sludge in iron-based electroplating solution - Google Patents

Abstract

PURPOSE:To conveniently and industrially remove the ferric ion and iron hydroxide sludge in an iron-based electroplating soln. by lowering the pH of the soln. in a settling tank to convert the ferric ion to ferric hydroxide which is settled and transferring the supernatant water to a storage tank. CONSTITUTION:The iron-based electroplating soln. is settled in the settling tank 1, and the pH is adjusted to 2 to <3.5 to convert ferric ion to ferric hydroxide which is settled. Samples are collected from sampling ports 3 arranged in the depth direction, the ferric ion concn. is measured by a turbidimeter 4, the depth at which the plating soln. is sucked is judged by a central processing unit 5, and the instruction is sent to a suction controller 6. A suction port 7 is positioned at an appropriate depth by the controller 6 based on the instruction, and the plating soln. at the upper layer in the settling tank 1 is transferred to the storage tank 2 by a suction pump 8. When the concn. of the ferric hydroxide sludge in the lower layer in the settling tank 1 is increased, an instruction is sent to a filter 9 from the central processing unit 5, the filtrate and the sludge are separated, and the filtrate is sent to the storage tank 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention is directed to the use of ferric ions and iron hydroxide sludge, which are present in iron-based electroplating solutions and produce ferric compounds that affect plating. It relates to a technique for easily and industrially removing it.

[Prior Art] In recent years, iron-based electroplating has become popular on an industrial scale, particularly as a plating on steel plates, in order to ensure weldability and paintability. Among these platings, there are various iron-based platings such as iron-zinc alloy plating, iron-nickel alloy plating, and iron plating on the top layer of multilayer plating, but the iron component of these plating layers is Obtained by electrolytic deposition of ferric ions in a liquid. However, ferric ions in the plating solution are extremely unstable and are easily oxidized by dissolved oxygen in the solution or oxygen generated at the anode to produce ferric ions. In particular, recently, insoluble anodes are often used from the viewpoint of productivity, and they are operated in a state where they are extremely susceptible to oxidation.

When the amount of iron hydroxide sludge produced by these ferric ions increases during plating, it deteriorates the properties of the plating film and reduces current efficiency, so it is disliked as a harmful substance. There is.

For this reason, various countermeasures against ferric ions have been taken in the past. These measures include those that prevent oxidation of ferric ions, those that reduce ferric ions, and those that remove ferric ions. As a method of preventing oxidation of ferric ions, there is a method of operating the plating bath at a pH lower than 1.5, but it is difficult to sufficiently prevent oxidation. There is also a method of preventing oxidation of ferric ions by bringing the plating solution into contact with metallic iron, but a method of reducing ferric ions that involves dissolving iron involves dissolving metallic iron in the plating solution. There is a method that attempts to reduce ferric ions by

However, this method is similar to the method of preventing oxidation by contacting metal iron.
The dissolution of iron, which is normally done to keep the ferric ion concentration in the plating bath constant, is performed for another purpose, so it has the disadvantage that it tends to upset the balance of the plating solution composition, making the plating conditions unstable. .

On the other hand, as a method for reducing ferric ions without dissolving iron, there is a method of electrolytic reduction. For example, JP-A-58
- In No. 199888, the electrolytic cell is divided into an anode chamber and a cathode chamber by partitioning the electrolytic cell with an anion exchange membrane, a separate conductive solution is placed in the anode chamber, and the plating solution is sent to the cathode chamber where cathode reduction is performed. is proposed. However, since an electrolytic bath is required in addition to the plating bath, and it is necessary to strictly control not only the cathode chamber but also the anode chamber to maintain reducing conditions, there is a problem of significantly increasing operating costs. be. Methods for removing ferric ions include a method in which ferric ions are adsorbed onto a chelate resin, and a method in which the pH of the plating solution is raised to higher than 3.5 to precipitate ferric hydroxide and then filtered. Since the chelate method is expensive to maintain, sediment filtration is common.

[Problems to be solved by the invention] However, in the conventional precipitation method, the precipitate is fine and the removal effect is small, so the aeration equipment becomes large, and the pH is significantly raised to speed up the precipitation, making it difficult to operate. There were problems such as complicated p+-1tA adjustment of the plating bath.

This invention was made to solve such problems, and its purpose is to remove ferric ions and iron hydroxide sludge industrially and easily.

[Means for Solving the Problems] Means for achieving this object is to solve the problem of ferric ions and This is an iron hydroxide sludge removal device, and the stationary tank is equipped with an 81 oval for measuring ferric ion concentration at different depths and a suction port, and this suction port is movable up and down to control its position. This is an apparatus for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution, which also includes a control mechanism, and one form thereof is one in which a filter is connected to the bottom of a stationary tank. and,
Using the above device, the iron-based electroplating solution is left standing in a standing tank, the pH of this plating solution is adjusted to 2 or more and less than 3.5, and the ferric ions contained in the upper layer of this standing solution are This is a method for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution by suctioning the upper layer based on the measured concentration value and transferring it to a storage tank. This is a method for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution, which involves filtering the lower layer of the solution and transferring the filtrate to a storage tank.

[Function] As mentioned above, iron hydroxide sludge is harmful.1 For example, in iron-zinc alloy plating, iron hydroxide sludge is mostly ferric hydroxide, and if the amount increases to nearly 10 g/ρ, Since this will affect the plating, it is advisable to control the amount to 1g/ρ or less.The iron-based electroplating solution, which has a high ferric ion concentration, is transferred to a static tank. When the pH is increased to 2 or more, ferric ions become ferric hydroxide and precipitate. Then, if left as is, the deposited precipitate will gradually settle, ferric ions will decrease from the upper layer and the precipitate will increase in the lower layer. Measuring ferric ion concentration at different depths 8! With this structure, it is possible to measure the ferric ion concentration in the depth direction of the stationary plating solution. A control mechanism allows the vertically movable suction port to be lowered to a position where the concentration is lower than a predetermined concentration, and at that position the plating solution is sucked and transferred to a storage tank connected to a static tank, where it is stored. Only the plating solution from which ferric ions have been removed will be stored in the tank. For example, in the case of iron-nickel alloy electroplating, the pH of the plating solution is set to less than 3.5 during standing.
This is to prevent the pH of the solution from which ferric ions have been removed from being significantly different from that of the plating solution being operated. - It is possible to connect one stationary tank to two storage tanks and perform removal during the suspension of operation, but since it takes a considerable amount of time to leave the stationary, it is not recommended to continue removal during plating operations. It may be convenient to have two or more static tanks.

When ferric ions are removed as described above, the ferric hydroxide concentration gradually increases in the lower layer of the plating solution in the stationary tank. This high concentration part can be taken out and processed separately, but if a filter is connected to the bottom of the stationary tank, the filtrate can be separated and sent to the storage tank, allowing most of the plating solution to be recovered. can be used.

[Example] (Example 1) The outline of the produced removal device is shown in Figure 1, where 1 is a stationary tank, 2 is a storage tank, 3 is a sampling port, 4 is a turbidity meter, and 5 is a center The processing device includes a suction controller 6, a suction port 7, a suction pump 8, and a filter 9. static 1 tank 1
Sampling ports 3 are provided at regular intervals in the depth direction and connected to a turbidity meter 4, so that samples taken at each position can be sent to the turbidity meter 4. The turbidity meters 4 are connected to send their respective measured values to the central processing unit 5. The central processing unit 5 is connected to the suction controller 6 and the filter, and based on the sent information, it grasps the settling depth of the iron hydroxide sludge, determines the depth at which suction is possible, and controls the suction controller 6.
send instructions to. The suction controller 6, which has been given the instruction, positions the suction lower at an appropriate depth and operates the suction pump 8, thereby transferring the plating solution in the upper layer of the stationary tank to the storage tank 2. When the amount of plating solution in the stationary tank 1 decreases and the concentration of ferric hydroxide sludge in the lower layer increases, an instruction is issued from the central processing unit 5 to the filter 9, and the filter 9 operates to remove the filtrate water. The ferric oxide sludge is separated and the filtrate is sent to storage tank 2.

In this example, multiple sample ports were provided, but it is also possible to have one sample port and move it up and down. Although a thermometer is provided, a flow injection type colorimeter or the like for measuring ferric ions may also be provided.

(Example 2) Main ingredients are ferric sulfate and zinc sulfate, sodium sulfate,
An iron-zinc alloy electroplating bath containing sodium acetate was used to remove ferric ions and iron hydroxide sludge from used baths, and its effectiveness was investigated.

This plating solution was stored in a stationary tank, the pH was adjusted by adding sodium hydroxide while stirring, and then the solution was left stationary. The supernatant liquid was sucked from the upper layer while measuring the turbidity, and most of the plating solution was transferred to a storage tank. Tests NIL1 to NIL3 measured the ferric ions and iron hydroxide sludge contained in the plating solution in the storage tank in this state, and test magnets 4 to 6 measured the remaining lower layer using a filter. It was filtered, separated and added to the supernatant. For comparison, the pH of the stationary solution was less than 2 (Test 11i17), and
A sample in which all the liquid was filtered without transferring the supernatant liquid after standing still (Test! No. 8) was also tested in the same manner as a comparative example. or,
As an example of the conventional method, a method in which the pH was raised and the entire amount was filtered was similarly investigated. The standing period is 7 days in each case.
The same filter was used for filtration, and the time required was 10 hours. The conditions and results of these tests are shown in Table 1.

In the examples of the present invention in Tests N[Ll to 6, the removal treatment reduced ferric ions to 2.2 g/Jl and ferric hydroxide to less than 1 g 71. However, in the comparative example, the ferric ion concentration did not decrease in Test NIL7, which had a low pH of 1.5, and the filtration effect was low in Test Magnet 8, and the iron hydroxide sludge was not completely separated under the same filtration conditions as in the Example. Ta. In the conventional example, the pH was raised, so ferric ions migrated to ferric hydroxide and the concentration decreased, but in the test NtL? Similarly, the filtration burden was large, and the sludge concentration did not decrease. That is, if the entire amount of the plating solution is filtered without collecting the supernatant liquid and an attempt is made to obtain the same effect as in the example, it can easily be seen that a filtration capacity several times or more is required.

[Effects of the Invention] According to the present invention, a stationary tank is provided, ferric ions in the iron-based electroplating solution are precipitated by converting them into ferric hydroxide in a low pH region, and the supernatant liquid is stored. Transfer to tank. For this reason, in addition to reducing the pH fluctuation of the plating solution during operation,
The effect of removing fine precipitates is superior to that of a filter, and there is no need to use a filter, or even a small one can be used.As such, this device is simple in equipment and operation, and has excellent removal ability. The effects of invention are significant.

Figure 1

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of an apparatus that is an embodiment of the present invention. 1... Stationary tank, 2... Storage tank, 3... Sampling port, 4... Turbidity meter, 5... Central processing unit, 6... Suction controller, 7... Suction Mouth, 8... Suction pump, 9... Filter.

Claims (4)

[Claims] (1) One or more stationary tanks equipped with a vertically movable suction port, a control mechanism for controlling the position of the suction port, and a depth-based measurement mechanism for ferric ion concentration, and storage connected to the stationary tank. 1. A device for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution, comprising a tank. (2) The device for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution according to claim 1, wherein the stationary tank is connected to a filter at the bottom. (3) Place the iron-based electroplating solution in a stationary tank, adjust the pH of this plating solution to 2 or more and less than 3.5, and measure the ferric ion concentration contained in the upper layer of this stationary solution. A method for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution, the method comprising sucking the upper layer based on the above and transferring it to a storage tank. (4) The removal of ferric ions and iron hydroxide sludge in the iron-based electroplating solution according to claim 3, further comprising filtering the lower layer of the plating solution left still in a still tank and transferring the filtrate to a storage tank. Removal method.