JPH083160B2 - Apparatus and method for removing ferric ion and iron hydroxide sludge in iron-based electroplating solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a ferric ion and iron hydroxide sludge which are present in an iron-based electroplating solution and produce a ferric compound that affects plating. The present invention relates to a technique for simply and industrially removing.

[Prior Art] In recent years, iron-based electroplating has been actively performed on an industrial scale particularly for plating on steel sheets in order to secure 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 uppermost layer of multi-layer plating.
The iron component of these plating layers is obtained by electrolytic deposition of ferrous ions in the plating solution. However, the ferrous ion in the plating solution is extremely unstable and is easily oxidized by dissolved oxygen in the solution or oxygen generated in the anode to generate ferric ion. In particular, in recent years, an insoluble anode is often used from the viewpoint of productivity, and it is operated in an extremely oxidizable state. The ferric hydroxide sludge produced by the ferric ion is disliked as a harmful substance because when the amount of ferric hydroxide increases in the plating solution, it deteriorates the properties of the plating film and reduces the current efficiency. .

For this reason, various countermeasures against ferric ions have been conventionally taken. Among these measures, there are ones that prevent the oxidation of ferrous ions, ones that reduce ferric ions, and ones that remove ferric ions. As a method of preventing the oxidation of ferrous iron, there is a method of operating by lowering the pH of the plating bath below 1.5, but it is difficult to sufficiently prevent the oxidation. There is also a method of preventing the oxidation of ferrous ions by bringing the plating solution into contact with metallic iron, but this involves the dissolution of iron. As a method of reducing ferric ion, there is a method of dissolving ferric iron in a plating solution to reduce ferric ion. However, this is similar to the oxidation prevention method by contact with metallic iron, because it is intended to dissolve iron for the purpose of keeping the ferrous ion concentration in the plating bath constant for another purpose. It has the drawback that it is easy to lose balance and the plating conditions become unstable.

On the other hand, as a method of reducing ferric iron without dissolving iron, there is a method of electrolytic reduction. For example, JP-A-58
In 199888, the electrolytic cell was divided by an anion-exchange membrane diaphragm to divide it into an anode chamber and a cathode chamber, another conductive liquid was placed in the anode chamber, and the plating solution was sent to the cathode chamber for cathodic reduction. Is proposed. However, there is a problem that the operating cost increases significantly because an electrolytic bath is required in addition to the plating bath, and not only the cathode chamber but also the anode chamber needs to be strictly controlled to maintain the reducing conditions. is there. As a method of removing ferric ion, there are a method of adsorbing it on a chelate resin and a method of raising the pH of the plating solution to more than 3.5 to precipitate it as ferric hydroxide and filtering it. Since the maintenance cost is high in the chelate method, precipitation filtration is common.

[Problems to be Solved by the Invention] However, in the conventional precipitation method, since the precipitate is fine and the removal effect is small, the size of the device becomes large, and since the precipitation is accelerated, the pH is greatly increased. There were problems such as complicated pH adjustment of the bath.

The present invention has been made to solve such a problem, and an object thereof is to industrially and easily remove ferric ions and iron hydroxide sludge.

[Means for Solving the Problem] A means for achieving this object is a ferric ion and water in an iron-based electroplating solution consisting of one or more stationary tanks and a storage tank connected to the stationary tanks. A device for removing iron oxide sludge, in which the stationary tank is equipped with a mechanism for measuring the concentration of ferric ion by depth and a suction port, and this suction port is movable up and down to control its position. The mechanism is also equipped with a device for removing ferric iron ions in the iron-based electroplating solution and iron hydroxide sludge, but one in which a filter is connected to the bottom of the stationary tank is one of the forms. And
Using the above equipment, the iron-based electroplating solution is allowed to stand in a stationary tank to adjust the pH of this plating solution to 2 or more and less than 3.5, and the ferric ion concentration in the upper layer of this standing solution is adjusted. It is a method of removing ferric iron ions and iron hydroxide sludge in the iron-based electroplating solution by sucking the upper layer based on the measured value and transferring it to the storage tank, and at the same time, the lower layer of the plating solution left standing in the stationary tank. This is a method for removing ferric iron ions and iron hydroxide sludge in an iron-based electroplating solution, which is also used by filtering the part and transferring the filtrate to a storage tank.

[Function] Iron hydroxide sludge is harmful as described above, but for example, in iron-zinc alloy plating, iron hydroxide sludge is mostly ferric hydroxide, and its amount increases to 10 g / near plating. Since the effect will appear, it is desirable to control the amount to 1 g / or less. When the iron-based electroplating solution whose ferric ion concentration has increased is transferred to a stationary tank and the pH of this plating solution is increased to 2 or more, ferric ion is precipitated as ferric hydroxide. Come on. Then, when left to stand as it is, the deposited precipitate is gradually settled, and ferric iron ions decrease from the upper layer and increase in the lower layer. The ferric ion concentration in the depth direction of the stationary plating solution can be measured by a mechanism that measures the ferric ion concentration for each depth. By the control mechanism, the vertically movable suction port can be lowered to a position where the concentration is lower than the specified concentration, and the plating solution is sucked at that position and transferred to the storage tank connected to the stationary tank for storage. Only the plating solution from which ferric ions have been removed will be stored in the tank. The pH of the plating solution when left to stand
Is less than 3.5, for example, in the iron-nickel alloy electroplating, the pH of the solution is operated at 1.0 to 2.0, but the pH of the solution excluding ferric ion is largely separated from the operating plating solution. This is to avoid that. It may be possible to connect one stationary tank to one storage tank and perform the removal while the operation is stopped, but since it takes a considerable time to stand, it is necessary to continue the removal during the plating operation. It may be convenient to have more than one static tank.

When ferric ion is removed as described above, the ferric hydroxide concentration in the lower layer of the plating solution in the stationary tank gradually increases. This high-concentration part may be taken out and treated 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, so most of the plating solution is Can be used for recovery.

[Example] (Example 1) FIG. 1 shows an outline of the produced removing device. In the figure, 1 is a stationary tank, 2 is a storage tank, 3 is a sampling port, 4
Is a turbidimeter, 5 is a central processing unit, 6 is a suction controller, 7 is a suction port, 8 is a suction pump, and 9 is a filter. The stationary tank 1 is provided with sampling ports 3 at regular intervals in the depth direction and is connected to a turbidimeter 4 so that samples taken at each position can be sent to the turbidimeter 4. The turbidimeter 4 is connected to send the respective measured values to the central processing unit 5. The central processing unit 5 is connected to the suction controller 6 and the filter 9, grasps the sedimentation state of the iron hydroxide sludge based on the sent information, judges the suctionable depth, and determines the suction controller 6. Send instructions. The suction controller 6 to which the instruction is given positions the suction port 7 at an appropriate depth and operates the suction pump 8, whereby the upper tank plating solution in the stationary tank is transferred to the storage tank 2. When the amount of the plating solution in the stationary tank 1 decreases and the ferric hydroxide sludge concentration in the lower layer increases, the central processing unit 5 issues an instruction to the filter 9 to activate the filter 9 and filter the solution. The ferric hydroxide sludge is separated and the filtrate is sent to the storage tank 2.

In this example, a plurality of sample ports are provided, but one sample port may be used and the sample ports may be moved up and down. Also, as a measuring instrument for ferric ions, the turbidity that measures the amount of ferric hydroxide by turbidity Although a densitometer is arranged, a flow injection type colorimeter or the like for measuring ferric ion may be arranged.

(Example 2) An iron-zinc alloy electroplating bath containing ferrous sulfate and zinc sulfate as main components and containing sodium sulfate and sodium acetate, treatment for removing ferric ion and iron hydroxide sludge in used ones. And examined the effect.

The plating solution was stored in a stationary tank, sodium hydroxide was added with stirring to adjust the pH, and then the plating solution was allowed to stand. The supernatant was sucked from the upper layer while measuring the turbidity, and most of the plating solution was transferred to the storage tank. Test Nos. 1 to 3 measure ferric ion and iron hydroxide sludge contained in the plating solution in the storage tank in this state, and Test Nos. 4 to 6 show the last remaining lower layer portion. It was separated by filtration with a filter and added to the supernatant. For comparison, the pH of the static solution is
The test was conducted in the same manner as a comparative example for those having a value of less than 2 (Test No. 7) and those for which all liquids were filtered without transferring the supernatant after standing (Test No. 8). Further, as an example of the conventional method, the same method was also applied to a method in which the pH was raised and the whole amount was filtered. The stationary period was 7 days in all, 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 of Test Nos. 1 to 6, the ferric ion was 2.2 g / and ferric hydroxide was 1 g / by the removal treatment.
Reduced to However, in the comparative example, the ferric ion concentration did not decrease in Test No. 7 having a low pH of 1.5, the filtration effect was low in Test No. 8, and under the same filtration conditions as the Examples, the iron hydroxide sludge was completely separated. There wasn't. In the conventional example, since the pH was raised, the ferric ion moved to ferric hydroxide and the concentration decreased, but as in Test No. 7, the filtration load was large and the sludge concentration did not decrease. That is, if the whole amount of the plating solution is filtered without collecting the supernatant to obtain the same effect as that of the example, it is easily found that the filtration capacity is several times or more than that.

[Effects of the Invention] According to the present invention, a static tank is provided to allow ferric iron ions in the iron-based electroplating solution to be changed to ferric hydroxide in a low pH range to precipitate, and the supernatant is stored. Transfer to tank. For this reason, in addition to the small fluctuation in pH of the operating plating solution, the effect of removing fine precipitates exceeds that of the filter, and the filter may or may not be used. As described above, the effect of the present invention is great because the device and operation are simple and the removal ability is excellent.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an apparatus which 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 port, 8 ... Suction pump , 9 ... Filter.

Claims (4)

[Claims] 1. One or more stationary tanks provided with a vertically movable suction port, a control mechanism for controlling the position of the suction port, and a depth-specific measurement mechanism of ferric ion concentration, and this static tank is connected. A storage tank for removing ferric ion and iron hydroxide sludge in an iron-based electroplating solution. 2. The apparatus for removing ferric iron ions and iron hydroxide sludge in an iron-based electroplating solution according to claim 1, wherein the stationary tank is connected to the filter at the bottom. 3. An iron-based electroplating solution is allowed to stand in a stationary tank, the pH of the plating solution is adjusted to 2 or more and less than 3.5, and the concentration of ferric ion contained in the upper layer of the standing solution is measured. A method for removing ferric ions and iron hydroxide sludge in an iron-based electroplating solution, which comprises sucking the upper layer based on the above and transferring it to a storage tank. 4. The ferric ion and hydroxide in the iron-based electroplating solution according to claim 3, wherein the lower layer portion of the plating solution left standing in the stationary tank is filtered and the filtrate is transferred to the storage tank. How to remove iron sludge.