JPS6144814B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention removes unnecessary heavy metals from a concentrated strongly acidic ferric chloride waste solution that contains a large amount of two or more types of heavy metals other than iron, and in particular contains the largest amount of nickel among these metals. The present invention relates to a method for regenerating a ferric chloride liquid with ability or flocculating action. Ferric chloride liquid is commonly used as an etching liquid (corrosive liquid) for precision processing of metal plates made of materials such as steel, copper, stainless steel, and nickel alloys, and is also used as an inexpensive inorganic flocculant in sewage treatment plants. It is used as. However, as the etching solution is used for corrosion, heavy metal ions accumulate in the solution, trivalent iron ions are reduced to divalent ones, the corrosive power decreases, and the solution is finally discarded. Currently, most of this waste liquid is subjected to alkali neutralization treatment, and the resulting precipitate is called sludge, which poses many pollution problems and is difficult to dispose of. For this reason,
It is desired to regenerate ferric chloride waste liquid and recycle it multiple times or more. Examples of conventional methods for regenerating ferric chloride waste liquid include (1) blowing chlorine gas into ferric chloride waste liquid containing large amounts of two or more types of heavy metals;
There is a method of regenerating it by oxidizing Fe ²⁺ → Fe ³⁺ . However, with this method, the regenerated solution has a weak recovery of etching ability and cannot be used in the same way as the new solution. (2) There are examples of recycling ferric chloride waste liquid that etches only copper, using electrolytic methods and chemical replacement methods. However, this method is not suitable for recycling when a large amount of various heavy metals other than copper are contained. (3) In addition, heavy metals as impurities are ignored, and instead only iron ions are adsorbed with a chelate resin, and after the iron is recovered, chlorine gas is injected to create a ferric chloride solution. be. However, this method requires a complex process and high equipment costs, making it difficult to put it into practical use from a profitability standpoint. Furthermore, according to Japanese Patent Publication No. 52-45665, the pH value of acidic waste liquid containing about 50 to 300 PPM of heavy metals is 5 to 5.
6, and then adding iron powder to the waste liquid to bring the heavy metals in the waste liquid below the permissible wastewater standard. However, this method is not suitable for treating the strongly acidic waste liquid which contains heavy metals at a high concentration of several 1000 PPM or more and contains the largest amount of nickel among the heavy metals, which is the object of the present invention. First, adjusting the waste liquid to a neutral range is a big hassle;
Furthermore, if iron powder is used, there is a risk that a reaction may occur rapidly at once, which is not desirable in terms of equipment maintenance. Of course, the method described above does not provide the benefit of restoring the etching ability of the ferric chloride solution and reusing it. Furthermore, when nickel metal is present in the largest amount in the waste liquid, nickel has a strong affinity with metal iron, so the precipitated nickel adheres to the surface of metal iron in a film form and becomes passivated. This prevents the subsequent precipitation reaction of heavy metals from proceeding, and therefore heavy metals other than iron cannot be removed by precipitation using normal means. As mentioned above, in the conventional method for regenerating ferric chloride liquid, there was no practical and efficient way to regenerate waste liquid that contains a large amount of two or more types of heavy metals, and in particular contains the metal nickel in the largest amount. good. The present invention is a method for regenerating ferric chloride waste liquid, which is different from the conventional techniques as described above.
This is a method for efficiently regenerating concentrated waste liquid that contains two or more types of nickel, chromium, and other heavy metals in large amounts. Specifically, the present invention mixes a lump of metallic iron into the waste liquid as described above, keeps the waste liquid in a heated state and stirs it to remove precipitated heavy metals, and then mixes it into the waste liquid. This is a regeneration method characterized by blowing in chlorine gas. The ferric chloride waste solution used for etching copper, stainless steel, nickel alloys, and other metal irons contains mostly Fe ³⁺ and Fe ²⁺ , but Ni ²⁺ and Cr ³⁺ eluted from the metal plates mentioned above also contain Fe 3+ and Fe 2+ . , Zn ²⁺ , Mn ³⁺ , Co ²⁺ ,
Contains large amounts of Cu ²⁺ and other heavy metal ions. Therefore, even if chlorine gas is blown into the material in this state to oxidize Fe ²⁺ →Fe ³⁺ , the recovery of the corrosion ability is weak. Apparently, the above-mentioned dissolved metal ions are interfering, and unless they are removed, reuse is impossible. Therefore, in the present invention, the following steps are used as a pre-process to remove heavy metals. A considerable amount of lumpy metallic iron is mixed into the ferric chloride waste liquid, and the waste liquid is heated to 40 to 90°C using reaction heat, a steam heater, or external heating. In this state, the waste liquid is reduced to ferrous chloride liquid while containing heavy metals. Furthermore, an excess amount of lump metal iron is mixed in, and the waste liquid is allowed to stand still in a heated state, or is stirred by vibration, rotation, etc., and the heated state is continued. In this way, unnecessary heavy metal ions are replaced with added metallic iron,
Precipitation occurs through various reactions such as reduction, adsorption, and co-precipitation. The waste liquid is filtered and solid-liquid separated by means such as a filter press method, and precipitated heavy metals are removed from the liquid. In this way, a ferrous chloride solution filtrate containing few impurities is obtained. Chlorine gas is blown into the waste liquid that has gone through the previous step as described above to oxidize Fe ⁺² →Fe ⁺³ , thereby completing all steps of the present invention. However, if the obtained regenerating solution contains excessive trivalent iron ions, the concentration should be adjusted to a predetermined Baume concentration by diluting it with water. EXAMPLES The present invention will be explained in further detail with reference to Examples below. [Example 1] 350 ml of ferric chloride waste solution (contains Fe, Ni, Cr, Cu and other heavy metals) from etching a metal plate
Mix 320g of metal iron 5cm round nails into the mixture,
After heating to a temperature of 50 to 80°C, a shaking machine with a shaking rate of 200 times/minute and a shaking width of 40 mm was used. Table 1 shows the heavy metal concentration of the stock solution and the concentration of the filtrate after a certain treatment time. Note that Fe (iron) is expressed in weight%, and other metals are expressed in weight%.
The unit is PPM.

[Example 2]

Add 400 g of lump metal iron, approximately 2 cm square, which has many protrusions with a large surface area, to 500 ml of ferric chloride waste liquid.
The experiment was carried out using the same shaker as in Example 1 under the same heating conditions. Table 2 shows the results of sampling and extraction performed at each reaction treatment time and measuring the concentration of heavy metals in the filtrate.

[Table] Among the heavy metals shown in Table 2, the main metals Fe,
The removal process for Ni, Cr, and Cu is shown in Figure 1 of the drawings. As can be seen from Table 2 and Figure 1, there are metals that can be removed and metals that cannot be removed or that increase. This is due to the characteristics of the metal, and moreover, this level of residue does not have any adverse effect on the etching ability of the regenerating solution. The method of the present invention is characterized in that lumpy metallic iron is added to a strongly acidic and highly corrosive ferric chloride waste solution, although the waste solution has a reduced etching ability. In other words, lumpy metallic iron is dissolved and the iron (Fe) content tends to increase, but this is a problem because it becomes a target when it is oxidized to ferric chloride by chlorine gas injection in the later process. There isn't. On the other hand, the reaction mechanism for removing heavy metals other than iron, which are unnecessary substances, is not clear, but by adding excess metal iron, chemical substitution occurs due to differences in ionization tendency, and rotation and shaking occur. Due to physical agitation, the metal iron collides with each other, the surface is abraded, and the metal nickel that adheres to the surface of the metal iron is peeled off, and the metal iron becomes finer due to the melting of the metal iron. It is thought that new surfaces are exposed and adsorption reactions and coprecipitation reactions continue to occur. Warming conditions accelerate these reactions. Therefore, the removal of these heavy metals is not 100% complete, nor is it necessary. If it is below a certain level, it can be used as a fully regenerated etching solution. FIG. 2 shows the flow when carrying out the regeneration method of the present invention on a large scale. According to the figure, 1 batch is 1~ ^10m3
First, the waste liquid is stored in the waste liquid storage tank 1, and a certain amount of the accumulated waste liquid is sent to the reaction tank 3 using the pump 2. Add, heat and stir. The waste liquid after the reaction treatment passes through a strainer 4 and is stored in a reaction treatment liquid storage tank 5, and then is forcibly filtered in a filter press machine 6 to remove heavy metals. Thereafter, it is stored again in the second ferrous chloride storage tank 7, oxidized with chlorine gas in the chlorine reaction tank 8, and the regenerated ferric chloride liquid is stored in the storage tank 9 for further use. It is something to be prepared for. The present invention is as described above, and according to the present invention, even if the PH value is strong acidity of 1 or less, and the content of heavy metals other than iron is at a high concentration of several 1000 to 2000 = 0 = PPM. This method has the advantage that various heavy metals can be removed at once, and the etching ability of the regenerated ferric chloride solution does not deteriorate at all. Furthermore, in the present invention, since lumpy metallic iron is added to the waste liquid, which is strongly acidic and has sufficient corrosive power, there is a risk that the reaction will rapidly proceed at once due to the addition of iron powder. It is also preferable in terms of equipment maintenance. In addition, during the reaction treatment with metallic iron, it may be allowed to stand still, but if agitation such as vibration or rotation is performed, the iron ingots will collide with each other, and the metallic nickel that has adhered to the surface in a film form due to crushing, abrasion, etc. will be exfoliated. Furthermore, since a new highly reactive surface is exposed, it has the effect of appropriately accelerating the reaction. 40 again this time
It can be said that it is efficient to heat the liquid to about 90°C to cause the reaction. The present invention makes it possible to regenerate ferric chloride waste liquid at low cost, eliminating the need to purchase new liquid, and the amount of heavy metals discharged by the method of the present invention is lower than that of conventional neutralization. Since the amount is much smaller than the sludge produced by the treatment, the benefits of subsequent treatment are also great. As described above, the present invention is extremely superior in practical terms.

[Brief explanation of the drawing]

Fig. 1 is a graph plotting the concentration changes of the main heavy metals in the waste liquid against reaction time in Example 2 of the present invention, and Fig. 2 shows the flow when carrying out the regeneration method of the present invention. FIG. 2 is a schematic diagram of the device. 1... Waste liquid storage tank, 2... Pump, 3... Reaction tank, 4...
Strainer, 5... Reaction treatment liquid storage tank, 6... Filter press machine, 7... Ferrous chloride storage tank, 8... Chlorine reaction tank, 9... Storage tank.

Claims (1)

[Scope of Claims] 1. A concentrated strongly acidic ferric chloride waste solution that contains two or more types of heavy metals other than iron, has a concentration of several thousand ppm or more, and contains the largest amount of nickel among the heavy metals. A method for regenerating a ferric chloride liquid, which comprises mixing lumpy metal iron, keeping the waste liquid in a heated state and stirring to remove precipitated heavy metals, and then blowing chlorine gas into the waste liquid. 2. The method for regenerating ferric chloride liquid according to claim 1, wherein the heating temperature of the waste liquid is 40 to 90°C.