JPH042792A - Method for recycling fecl3 solution - Google Patents

Abstract

PURPOSE:To effectively recycle FeCl3 from an FeCl3 soln. as a used etching soln. by absorbing HCl in the FeCl3 soln., heating and concentrating the resulting hydrochloric acid soln., stripping off HCl and sending the remaining soln. to a crystallizer. CONSTITUTION:A used etching soln. 3 is sent to an NiCl2 crystallizer 5 and brought into contact with HCl sent from a pipe 6. A formed slurry contg. NiCl2 and FeCl2 is sent to an NiCl2 filter 7 and subjected to solid-liq. separation. The separated mother liquor is fed into a concentrator 10 and most of HCl is removed by evaporation. The resulting concd. FeCl3 soln. is mixed with circulating mother liquor contg. FeCl3 and the mixture is sent to an FeCl3 crystallizer 12, where a slurry contg. crystals of FeCl3.2.5H2O is formed. This slurry is fed into an FeCl3 separator 17 and subjected to solid liq. separation. The separated crystals are washed to remove free HCl and the separated mother liquor is returned to the concentrator 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to nickel or an iron alloy containing nickel,
For example, the present invention relates to a method for regenerating waste liquid generated when etching unchanged steel (Invar) with an aqueous solution containing FeCl.

[Conventional technology]

In recent years, with the development of televisions, office automation equipment, and computers, CRTs have come into widespread use, and demands for high precision and high quality have also increased. Along with this, high nickel alloys such as invar have also been used for shadow masks.

For etching such alloy films or pure nickel films, a highly concentrated aqueous solution of FeCl5 is used as an etching agent because it has a mild and reliable effect and does not generate gas. When raw metals such as nickel and iron are partially dissolved during etching, FeCl5 is reduced and becomes FeC.
It becomes l□. On the other hand, iron and nickel are each FeCl*
and NiC1□ and dissolves.

The generated FeClt is treated with H in the presence of chlorine gas or hydrochloric acid.
20, etc., it is easily oxidized to the original FeCl5, but only by such a method, N is added to the system.
iCl2 accumulates and eventually becomes unusable in terms of reaction rate and equilibrium. Therefore, in order to recycle the etching solution, it is necessary to extract at least a portion of it as etching waste solution, remove the nickel component, and then return it to the system. Various methods have been proposed for removing nickel from such etching waste liquid. That is, (a) a method of electrolyzing waste liquid and depositing metallic nickel by cathodic reduction (Japanese Patent Laid-Open No. 59-31868).

(b) A method of precipitating and separating nickel as a complex using a selective complexing agent for nickel such as glyoxime (Japanese Unexamined Patent Publication No. 59-1
90367), (c) a method in which nickel is precipitated by displacement using metallic iron, and then Fe"+ is oxidized to Fe3+ using chlorine (Japanese Patent Publication No. 61-44814), (d) after heating and concentrating the etching waste liquid. After cooling, first FeClx・4
After removing H20 crystals, HCl gas is introduced while cooling the mother liquor to 5 to -10°C to precipitate and recover only nickel as NiCl2 crystals, while stripping HCl from the liquid to be treated. is recovered as a concentrated liquid of FeClg, and the stripped and recovered HC
(Japanese Patent Publication No. 63-10097), (e) absorbing HCl gas into the etching waste liquid to crystallize FeClz crystals at the same time as NiCl2, and heating the solid-liquid separated liquid. After distilling and removing some of the HCl gas and water, water and iron pieces are added to the residual liquid to neutralize it.
1 (Japanese Patent Laid-Open No. 62-222088) has been proposed.

[Problem to be solved by the invention]

In conventional method (a), Fe t + and Ni2+ have similar standard electrode potentials at which they become metals, and nickel tends to generate overvoltage, making it difficult to selectively reduce and precipitate only nickel. '' is also reduced, so it is not economical. (b) can achieve a high nickel removal rate, but the complexing agent is expensive, and it is generally not necessary to completely remove nickel, so it is not economical. (c) has few advantages. After all 3''' is reduced to Fe''+, nickel precipitates and a large amount of FeCl□ is generated, so this is not necessarily a good method for recovering FeCl3. (d) is one of the most desirable methods. However, it requires cooling to a low temperature of 5 to -10°C, which increases electricity costs, and because FeCl5 is recovered as an aqueous solution, hydrogen chloride in the recirculated etching solution cannot be sufficiently removed. If the etching solution contains free hydrogen chloride above a certain limit, there is a great possibility that hydrogen will be generated during etching, which will hinder precise and stable operation, and there will also be safety problems.

Therefore, when highly accurate etching is required, such as for CRT shadow masks, a large amount of metallic iron or iron oxide is added to the recovered iron chloride solution to neutralize the free hydrochloric acid, as shown in example (e). create a need. However, the added iron increases a large amount of Fe2, and in order to recover it as Fe''+ for etching, the consumption of oxidizing agent increases.

Also, in some cases, it is necessary to extract excess iron for balance purposes, which is wasteful consumption and cannot be said to be a rational method.

[Means to solve the problem]

The present invention is an attempt to solve the above-mentioned problems, and the method uses N discharged from the etching process of nickel or nickel alloy using an aqueous solution of FeCl5.
HCl gas is absorbed into waste liquid containing iCl2, FeCl3 or even FeClz, and due to the difference in solubility Ni
In a method for regenerating an etching Iil liquid, which includes crystallizing Cl2 and recovering and reusing FeCl and HCl, (a) the etching waste liquid is brought into contact with an HCl-containing gas, either as is or after being concentrated; HCl is absorbed and most of NiClt and FeClz and/or Fe
A step of simultaneously crystallizing and separating a part of FeCl3 at 15 to 35°C and recovering most of FeCl3 as a hydrochloric acid solution, and (b) recycling the FeCl3 hydrochloric acid solution in a concentrator.
Concentrate by heating or heating under reduced pressure while mixing with Cl5 solution, distill off at least a part of HCl and water, and extract a part of the concentrated liquid.
Crystals mainly composed of 5.2.5H-0 and FeCl5 solution are precipitated and separated, and the mother liquor is collected from the circulating FeC
The FeClz crystals are circulated to the concentrator as a solution, and the FeClz crystals are washed as necessary with water or a solution containing almost no free HCl in the system, and then returned to the etching step, and (C) the FeClz crystals distilled off in the previous step It consists of a combination of at least three steps: separating water from a mixture of HCl and water, concentrating HCl, and returning it to step (a).

The present invention will be explained below based on the illustrated flowchart.

When a nickel alloy plate such as Invar is etched with an aqueous FeCl1 solution, NiCl and FeClt are generated and dissolved in the etching solution. Usually the etching solution is FeCl
In order to keep the concentration constant, C1,
FeClx is oxidized to FeCl5 and the concentration is recovered, and the mixture is used by mixing it with FeCl3 for makeup, which is sent separately, as necessary. NiC1* concentration to a certain extent,
For example, if it exceeds 5%, it will be unsuitable for etching.
A portion of the etching solution is extracted from the pipe 2 or 1 and subjected to regeneration treatment as etching waste solution. This waste liquid usually contains about 40-50 wt% FeCl5, FeClz
It contains approximately 0-10 wt% of NiCl2 and 2-5 wt% of NiCl2. If the oxidized liquid is extracted from the oxidation tank O through the pipe 2, it will contain almost no FeClz, so it will be removed in a later operation.
NIC12 containing almost no . l'1 when processing the liquid extracted through pipe 1 before being oxidized
Since FeCl2 also tends to crystallize at the same time as ic1z, Ni
The purity of C1□ decreases. However, the load for oxidation is reduced accordingly.

Next, the waste liquid extracted from the etching tank E or the oxidation tank O is sent to the NiCl2 crystallizer 5 via the pipe 3.
In some cases, Fe may be added in a pre-concentrator (not shown) before
Cl may be concentrated to about 60 to 100% by weight.

Concentration saves the amount of HCl that has to be absorbed.

This is particularly preferred in the case of waste liquid containing a small amount of Fecl.

MCI is sent to the crystallizer 5 through a pipe 6 and comes into contact with the waste liquid that is the liquid to be treated.

The liquid to be treated is cooled and circulated by the pump p-1 and the cooler 4, and is brought into contact with HCl by suitable means such as a wetted wall, so that the average temperature is maintained at about room temperature of 15 to 35°C. HCl may be absorbed under pressure. If it is less than 15°C, the power cost for cooling increases, and if it exceeds 35°C, it is not preferable due to the solubility of HCl and NiCl2. Here Ni
The solubility of C1t becomes extremely low due to an increase in the common ion CF, and C1t crystallizes.

FeClx also has a similar tendency.

On the other hand, FeCl s becomes a chloroferric acid complex HFeCl, and its solubility increases, making it difficult to precipitate. FeCl1 is H
Depending on the absorption method of Cl, it may be possible to precipitate it before making it into a chloroferric acid complex due to solubility, but in this case, N
Since iC1* is probably involved as a eutectic, the NiC1* concentration in the remaining mother liquor can also be significantly lowered.

In the case of a nickel alloy, the amount of iron to be precipitated is equal if the Ni/Fe ratio in the precipitated crystals is equal to or slightly larger than the Ni/Fe in the alloy, eliminating the need to replenish FeCl5 into the system. When, the total intra-system balance is established.

A crystal slurry containing NiCl, FeCl, and possibly FeCl1 produced in the crystallizer 5 is sent by a pump p-2 to the NtC1z filter 7, where solid-liquid separation is performed. Filtration can be carried out using any device, but the temperature is preferably around the crystallization temperature. As the device, a centrifugal separator, a pressure filter, etc. are suitably used. H that may occur at this time
The Cl gas is optionally processed through a hydrochloric acid vapor line 8.

The mother liquor separated by filtration@&7 is a solution mainly consisting of concentrated FeCl (and/or HFeCl) and HCl. This is supplied to a de-HCl/FeCl/concentrator 1510 by a pump p-3, and heated by steam 11 to evaporate most of the MCI and water. At this time, reduced pressure evaporation may be used.

This mixture of HCl and water may be used in the HCl concentrator 9 by increasing the concentration to around 90 to 100% using appropriate means such as extractive distillation using CaC1z, pressurized distillation, cooling decomposition, etc., as necessary. This increases the absorption efficiency in the crystallizer 5. Meanwhile, in the concentrator 10, FeClz is mixed with circulating FeCl5 mother liquor, which will be described later, and concentrated to a concentration of about 75%. The concentration temperature used is about 180°C under normal pressure, and about 60-120°C under reduced pressure. The concentrated liquid is sent to the FeCl5 crystallizer 12 through the pipe 15, but in the figure, it is circulated by the pump p-4, and FeCl,
The FeClx slurry is supplied and mixed into a pipe 14 through which the FeClx slurry is cooled by a crystallization cooler 13. The temperature of the crystallizer 12 is maintained at about 30-35°C, and mainly FeCl5.2.
Crystals of 5H,0 crystallize and become slurry, which is pumped p-
It is supplied to the FeCl3 separator 17 through s and subjected to solid-liquid separation at a temperature of 30° C. or higher. The crystal part is washed with a small amount of water sent from the pipe 16 or a liquid containing almost no free HCl generated in the system, for example, a small amount of the waste liquid before absorbing MCI, and free HCl is removed from the crystal. . At this time, in the latter method, the FeCl5 crystal is contaminated to some extent with 1 g of Ni'C, but since the quantity is small, no particular problem occurs.

The mother liquor from which the crystals mainly composed of FeCl1.2.5H10 have been separated is returned to the concentrator 10 via pump p-6 as the FeCl5 concentrator circulating fluid.

The crystals of FeCl obtained in the present invention have low stickiness,
Since the separation of the mother liquor is good, free HCl can be separated very well, almost no chemical removal operation is required, and even if necessary, the amount of iron or iron oxide required for this purpose is extremely small.

The crystals mainly composed of FeCl, .2.5H and O thus obtained are sent to the dissolution tank S and supplied as a FeCl solution to the etching tank for reuse.

〔Example〕

The results of the operation according to the flow chart shown in the figure are shown in Table 1 below. The etching waste liquid used here was concentrated to a concentration of about 606/' FeCl+ using a concentrator (not shown). Position numbers in the table correspond to those in the figure.

(The following is a blank space) [Effects of the invention] The present invention is particularly useful for high-precision C
It is effective for recycling and recovering nickel alloy etching waste liquid for RT shadow masks, and since the crystallization temperature of various crystals is high, it is advantageous in terms of energy, and recovered FeCl s
This is an extremely excellent method industrially because it is easy to remove free HCl therein.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one embodiment of the present invention. 1.2.3...Piping 4...Cooler 5
...NiC11 crystallizer 6...Piping 7.
...NiCl2 filtration 58 ... Hydrochloric acid vapor line 9 ... HCl concentrator 10 ... HCl removal
Also FeCl5 concentrator 11...Steam 12
...FeCl, crystallizer 13 ...FeCl5
Crystallization cooler 14, 15.16...Piping 17
...FeCl, separator p-1, 2, 3, 4, 5,
6... Pump E... Etching tank O...
...Oxidation tank S...Dissolution tank

Claims (1)

[Claims] (1) NiCl_ discharged from the etching process of nickel or nickel alloy using an aqueous solution of FeCl_3,
2. HCl gas is absorbed into the waste liquid containing FeCl_3 or even FeCl_2, and NiC
In a method for recycling an etching waste liquid, which includes crystallizing and separating FeCl_2 and recovering and reusing FeCl_3 and HCl, (a) the etching waste liquid is used as it is or is concentrated;
Contact with HCl-containing gas to absorb HCl, NiC
l_2 and FeCl_2 and/or FeCl_
A part of 3 was simultaneously crystallized and separated at 15 to 35°C, and F
Most of the eCl_3 is recovered as a hydrochloric acid solution, and (b) the FeCl_3 hydrochloric acid solution is recycled in a concentrator.
Concentrate by heating or heating under reduced pressure while mixing with Cl_3 solution, distill off at least part of HCl and water, extract a part of the concentrated liquid, and convert it into FeCl in a crystallizer.
Crystals mainly composed of _3・2.5H_2O and FeCl_3
The mother liquor is circulated as the circulating FeCl_3 solution to the concentrator, and the FeCl_3
The crystals are washed with water or a solution containing almost no free HCl in the system as necessary, and then returned to the etching process; and (c) water is separated from the mixture of HCl and water distilled off in the previous process. A method for regenerating FeCl_3 liquid, comprising at least three steps of concentrating HCl and returning it to step (a).