JPS6366908B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in a method for removing heavy metals from a ferric chloride etching waste solution containing heavy metals and regenerating it into a ferric chloride solution with restored etching ability. [Prior Art] Ferric chloride solution is frequently used as an etching solution for etching metal plates made of steel, copper, stainless steel, nickel alloy, etc. When this etching solution is used repeatedly, dissolved heavy metals accumulate in the solution, and trivalent iron ions are reduced to divalent ones and become ferrous chloride, resulting in a decrease in etching ability. Therefore, it had to be disposed of as waste liquid, which caused a pollution problem. Therefore, it has been desired to regenerate and reuse such etching waste liquid. Conventionally, as a method for regenerating ferric chloride etching waste liquid, a method described in Japanese Patent Application Laid-open No. 121123/1983 has been known. This method involves adding lumps of metallic iron to the ferric chloride etching waste liquid, then heating it to remove the precipitated heavy metals, and then blowing chlorine gas to convert the divalent iron ions in the waste liquid to trivalent. Become. However, in this method, when heating the waste liquid after adding metallic iron, if local overheating or overheating occurs over an hour, an explosive reaction will occur and the pressure inside the reactor will rise rapidly. There are drawbacks in terms of equipment maintenance, such as liquid leaks and gas leaks, and problems with the material of the reactor due to the high temperature of the waste liquid, and improvements have been desired. [Problems to be Solved by the Invention] The present invention has been made under the above circumstances, and is capable of safely handling ferric chloride etching waste liquid containing a large amount of heavy metals without causing any damage to the equipment. The purpose is to provide a method for reproducing information quickly and efficiently. [Means for Solving the Problems] The present invention involves heating a ferric chloride etching waste solution containing heavy metals in advance, adding metallic iron to the heated waste solution to cause a reaction, removing precipitated heavy metal components, and then discharging the waste solution. The present invention provides a method for regenerating a ferric chloride etching waste solution, which comprises blowing chlorine gas into the waste solution to oxidize divalent iron ions in the waste solution into trivalent iron ions. In the method of the present invention described above, the heating temperature of the etching waste liquid before adding metal iron is preferably 60 to 120°C, more preferably 90 to 100°C. Below 60°C, the reaction is too slow, and above 120°C, it is difficult to control the reaction. Further, it is preferable that the metal iron added to the heated etching waste liquid be in the form of lumps. Powdered metallic iron is not preferred because the reaction proceeds rapidly and causes the same problems as in the prior art. Note that it is preferable to add not only metal iron but also Fe(OH) ₂ -containing sludge as a catalyst to the heated etching waste liquid. This Fe(OH) _2- containing sludge is
The heavy metal components removed from the etching waste liquid are recovered and separated and recovered from this. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. The drawing is a flow sheet showing the etching solution regeneration process used in the examples. First, the ferric chloride etching waste liquid stored in the waste liquid tank 1 is heated to 100° C. through the heater 2. The heat source of the heater 2 is steam from a steam source 3. Next, the etching waste liquid heated to 100℃ was poured into the reactor 4.
to be introduced. Reactor 4 is a cylindrical vessel rotatable around a horizontal axis 5. A lump of metallic iron 6 is added to the etching waste liquid introduced into the reactor 4. As a result, ferric chloride is reduced to ferrous chloride, and heavy metal components in the waste liquid react with iron and precipitate. Such a reaction is uniformly carried out by rotating the reactor 4. In addition, reactor 4
In addition to metallic iron, separately recovered Fe(OH) ₂ -containing sludge, which will be described later, is added to the waste liquid as a catalyst, thereby making it possible to carry out the reaction more efficiently. FIG. 2 shows the amounts of Ni and Cr dissolved in the etching waste liquid during heating in the heater 2 and during the reaction in the reactor 4, and changes over time in the pH of the waste liquid. From the second graph, it can be seen that both Ni and Cr rapidly precipitate due to the reaction in the reactor 4, and the concentration in the waste liquid decreases. For example, Ni becomes 400~2.5~3 hours from the start of the reaction.
Although the Ni concentration decreases to 500 ppm, it can be used as a regenerated etching solution. The etching waste liquid containing the precipitated heavy metal components is then introduced into the stirring tank 7, where it is uniformly stirred. Water 8 is added to this stirring tank 7, and the waste liquid is diluted to a predetermined concentration. Thereafter, the waste liquid is sent to a filter press 9 together with water 8 as washing water, where it is filtered and separated into liquid and solids. Of the solid content, the light sludge deposited on the left side in front of the filter press is Fe(OH) ₂ -containing sludge 10 with a low content of heavy metals such as Ni, and the heavy sludge deposited on the right side in front of the filter press is sludge containing heavy metals such as Ni. High Ni-containing sludge 1
It is 1. Fe(OH) ₂ -containing sludge 10 is introduced into reactor 4 together with metal iron 6 as a catalyst. Ni-containing sludge 11 is collected separately,
It is sold as recovered Ni raw material. The composition (wt%) of the Ni-containing sludge obtained in this example is shown in Table 1 below.

[Table] As is clear from Table 1, Ni-containing sludge is
It has an extremely high Ni content and can be usefully used as a Ni resource. On the other hand, the liquid is sent to a chlorine reaction tank 12, and chlorine gas 13 is blown into it. As a result, ferrous ions (F ²⁺ ) in the liquid are oxidized to ferric ions (F ³⁺ ). That is, ferrous chloride is treated as ferric chloride. The regenerated etching solution thus obtained is sent to storage tank 14 and stored there. The composition of the etching solution regenerated by the above process is shown in Table 2 below, along with the compositions of the new solution and waste solution.

〔Effect of the invention〕

By the method of the present invention, various excellent effects shown below can be obtained. (1) Unlike conventional methods, in the method of the present invention, metal iron is added after heating the etching waste solution, so the reaction occurs gradually and uniformly, which is completely conducive to operational safety and equipment maintenance. Does not cause any problems. (2) Etching costs are significantly reduced because there is no need to purchase new etching liquid or to dispose of etching waste liquid. For example about 50
~60% decrease. In particular, the direct connection to the etching process eliminates the cost of transporting etching waste liquid and regenerating liquid. (3) All by-products other than the regenerated liquid can be reused, so there is no waste liquid and no pollution problem occurs. Contains particularly high concentrations of Ni, Cr, Cu, etc.
All Ni-containing sludge can be recycled. (4) Since the quality of the etching solution is always maintained constant, etching can be performed with constant accuracy.
Useful for quality control. In particular, in recent years, it has been planned that the material of shadow masks will shift from iron to amber (nickel alloy), but when such shadow masks are manufactured by etching, a large amount of nickel dissolves into the etching solution, which causes the etching process. However, according to the method of the present invention, the nickel component is effectively removed from the etching waste solution, so that the accuracy of the shadow mask is not impaired. (5) By adding Fe(OH) ₂ sludge to the waste liquid, the generation of hydrogen gas (OH ^- +H ⁺ →H ₂ O) is fundamentally suppressed, so there is almost no risk of explosion.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of the etching waste liquid regeneration process according to an embodiment of the present invention, and FIG. 2 shows the etching waste liquid regeneration process during heating and reaction.
3 is a graph showing changes over time in the amount of Ni and Cr and the pH of waste liquid. 2... Heater, 4... Reactor, 9... Filter press, 12... Chlorine reaction tank.

Claims (1)

[Claims] 1 Preheat ferric chloride etching waste liquid containing heavy metals to 60 to 120°C, add metallic iron to this heated waste liquid and react, remove precipitated heavy metal components, and remove Fe(OH) ₂ from the heavy metal components. Separate and recover the sludge and Ni-containing sludge, add the Fe(OH) _2- containing sludge to the heated waste liquid as a catalyst for the reaction with the metal iron, and then blow chlorine gas into the waste liquid from which heavy metal components have been removed. A method for regenerating a ferric chloride etching waste solution, which comprises oxidizing divalent iron ions in the waste solution to trivalent iron ions.