JPS61143527A - Treatment of metal-containing water - Google Patents

Abstract

PURPOSE:To extract and recover efficiently valuable metals by concentrating preliminarily metal-contg. water and using cyclically a back extracting agent in the stage of separating and extracting the valuable metals by extraction and back extraction from the metal-contg. water. CONSTITUTION:Waste plating water contg. Cu ions such as waste Cu plating water is put into a reaction vessel 31 and a flocculating agent such as FeCl2, FeCl3, FeSO4 or iron polysulfate is added thereto concentrate and flocculate the water and thereafter the water is supplied to a settling vessel 32 where a high-molecular flocculating agent such as partial hydrolyzate of polyacrylamide is added to the water to settle the metals such as Cu and Fe contained in the water in the form of hydroxide. The water is then fed to a pH adjusting vessel 33 where an acid or alkali is added thereto to adjust the pH. The water is fed to an extraction device 34. Only the Cu is separated from Fe by an extracting agent via a cylindrical solid membrane in the device 34 and thereafter the Cu is back extracted by a back extraction method and is taken out of an outlet 27 in the form of the crystal of CusO4. The remaining liquid is again circulated to the vessel 31 for flocculation of the waste plating liquid.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for treating metal-containing water, and more particularly, to a method for treating metal-containing water that can recover contained metals with extremely high efficiency. .

[Prior Art] Cleaning wastewater containing metal is discharged from metal plating processes, or pickling and etching processes for metal materials and metal products.

Conventionally, a common method for treating such metal-containing water is to neutralize it, precipitate metal hydroxides, and then perform solid-liquid separation (for example, Japanese Patent Publication No. 59-29675). Other methods include a method of recovering metals by evaporation, a method of recovering metals from metal-containing water by extraction, and a method of extracting metals after concentrating metal-containing wastewater such as gallium wastewater by an ion exchange resin method (Japanese Patent Application Laid-Open No. 118026-1982). , a method has been proposed in which metals are extracted after concentrating metal-containing wastewater by a reverse osmosis membrane (RO) method (Japanese Patent Application Laid-Open No. 131188/1983).

[Problems to be solved by the invention] However, a method of processing only by neutralization (Tokukō Kokō 5)
9-29675), a large amount of neutralizing agent is required for neutralization, and sludge that is difficult to dewater is generated.

The drawback was that sludge treatment was difficult.

The evaporation method is not advantageous in terms of energy costs and also cannot selectively recover metals, and the method of recovering metals by extraction is only effective when the metals contained in wastewater are at low concentrations. The extraction speed is slow and not efficient.

The method of extracting metal-containing wastewater after concentrating it has the following problems. That is, when the ion exchange resin method or other concentration methods are employed, it is very difficult to recover the metals extracted into the back extractant.

In other words, in conventional methods, it is necessary to precipitate and recover metals from the back-extracting agent by electrolysis, etc., but when electrolysis is used, it is not possible to increase the acid concentration in the back-extracting agent, and the back-extraction rate is low. It has the disadvantage that it is slow. Furthermore, this method requires an electrolyzer, which is not advantageous in terms of equipment costs, power costs, maintenance, etc.

[Means for Solving the Problems] The present invention has been made to solve the above conventional problems and provide an economically and industrially advantageous method for treating metal-containing water. is used as an extraction material, the extraction material is brought into contact with an extraction agent, and the extraction agent is then brought into contact with a back-extracting agent to recover metal salts in the back-extracting agent. The contact between the extraction material and the extraction agent and/or the contact between the extraction agent and the back-extracting agent is carried out through a solid membrane, and the back-extracting agent is used repeatedly to crystallize the extracted material from the back-extracting agent. A method for treating metal-containing water, characterized by:

The main points are as follows.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a system diagram showing an example of treating Cu plating wastewater by employing a coagulation-sedimentation treatment method as a concentration method before extraction according to the method for treating metal-containing water of the present invention.

Cu plating wastewater discharged from the washing process in the finishing process of Cu-plated products usually contains several ppm to several hundred ppm of Cu. In the present invention, such Cu plating wastewater is first sent to the reaction tank 31. It is fed and undergoes a flocculation reaction by a flocculant. In this case, the coagulation reaction efficiency can be increased by adjusting the liquid in the reaction tank to an alkaline range of about PHII by adding a pH adjuster such as an alkaline agent. is selected depending on the metal contained in the wastewater, but usually FeCl2.
FeCl3. Fe compounds such as Fe50+ and polyferric sulfate are preferably used.

The flocculation reaction liquid from the reaction tank 31 is then fed to the precipitation tank 32 and subjected to precipitation treatment. In the precipitation tank 32, by adding a polymer flocculant such as a partial hydrolyzate of polyacrylamide, precipitation can be carried out efficiently. The supernatant water obtained from the precipitation treatment is discharged outside the system. The precipitated sludge contains Cu(OH)2, Fe(O
H)2.

It contains Fe(OH)3, but this one has a pH of
After being fed to the adjustment tank 33 and having its concentration adjusted by adding a renewal solution (such as an electrolytic solution for a plating tank containing several thousand to tens of thousands of ppm of Cu) as necessary, further The pH is adjusted with acid or alkali, and the mixture is sent to the extraction device 34. (The renewal solution may be mixed with washing water and injected into the reaction tank 31 for treatment, but since the Cu concentration is high, it is preferable to send it to the pH adjustment tank for extraction.) Extraction device 34
In this process, first, the liquid from the pH adjustment tank 33 is used as an extractant, and this is brought into contact with an extractant, and then the extractant is brought into contact with a back-extracting agent. Then, the back extractant that extracted Cu 11 from the extraction agent is recycled and used to increase the Cu salt concentration, and the
The u-salt is crystallized from the back extractant. C obtained by crystallization
u SO4.5H20 crystals can be reused in plating baths and the like.

In this case, Fe ” along with Cu2+ is present in the drawing material.
, Fe3+ is included, but in the extraction process, by selecting an extractant (for example, using SME-529 (manufactured by Shell Chemical Co., Ltd.) in this example), only Cu 24'' can be extracted. It is possible to selectively extract Fe 2+, Fe'+
Since Fe salt remains in the raffinate, by feeding the raffinate to the reaction tank 31, it becomes possible to reuse the Fe salt as a flocculant. For this reason, the flocculant needs to be added in the reaction tank only at the start of the treatment, and there is almost no need to add the flocculant thereafter, reducing running costs.

In addition, in FIG. 1, the case where concentration of metal-containing water is performed by a coagulation sedimentation treatment method has been explained, but in the present invention, the concentration method is not limited to this, and other methods,
For example, ion exchange treatment method.

It is also possible to employ membrane separation treatment methods, evaporation treatment methods, etc. Further, as explained above, when only a certain specific component is back-extracted, other metal ions such as iron ions are gradually concentrated in the circulating raffinate, so they are appropriately extracted and processed separately.

By concentrating the metal-containing water in advance and then extracting it in this way, the extraction rate can be significantly improved and the loss of the extractant can be reduced. (Generally, if the extract is concentrated by a factor of X, the loss of extractant will be reduced to about 1/x.

) Figure 2 shows an example of a device suitable for use as the extraction device 34 in the method of the present invention, and is a tubular type.
Alternatively, it is a sectional view of an extraction device equipped with a hollow fiber type solid membrane.

(2) is a cylindrical device casing, in the upper part of which a back extraction side introduction chamber 21 and extraction material introduction chamber 22 are defined by partition plates 11 and 12, and in the lower part by a partition plate 13,
A raffinate discharge chamber 23 and a crystallization chamber 5 are defined. Then, so that the extraction chamber 22 and the extraction chamber 23 are communicated with each other,
A large number of pipe-shaped solid membranes 20 are provided.

Between the upper partition plate 12 and the lower partition plate 23,
And pipe-shaped solid I! The outer part 24 of 20 communicates with the back extraction side introduction chamber 21 and the crystallization chamber 5, respectively.
Further, the extraction agent is supplied and discharged through an extraction agent supply port 15 and an extraction agent discharge port 1B provided in the casing l. In addition, the extraction agent outlet 18 and the extraction agent supply port 1
5 through a conduit 25 in which the pump 2 is installed.

Further, the back extraction side introduction chamber 21 and the crystallization chamber 5 are provided with a back extraction agent supply port 16 and a discharge port 19, respectively, and the supply port 16 and the discharge port 19 are connected by a pipe line 26. A pump 3 is installed in the middle of this pipe line 26, and a pipe 4 for replenishing the back extractant is connected.

In the figure, 17 is an outlet for discharging the extract (raffinate liquid) from the extract discharge chamber 23, and 27 is an outlet for taking out the precipitated crystals from the crystallization chamber 5.

In the extractor shown in FIG. 2 configured in this manner, the extract containing metal salts supplied from the supply port 14 flows from the introduction chamber 22 into the pipe-shaped solid membrane 20 and flows downward (as indicated by the arrow in the figure). A), and the extractant introduced from the supply port 15 and rising up the outer part 24 of the solid membrane 1O (in FIG. 2, the shaded area is the rising area of the extractant) and the solid membrane 2
0, and the metal salts in the extract are extracted into the extract.

- side, the back extractant supplied from the supply port 16 is in the introduction chamber 2.
1, it descends in the form of a liquid column or droplet into the extractant in the outer portion 24 (shaded area in FIG. 2) of the solid membrane 20 (arrow B in the figure), and comes into direct contact with the extractant and metal Perform back extraction of salt.

The raffinate is discharged from the I# outlet 17, and as explained in Fig. 1, when concentrating metal-containing water by the coagulation-sedimentation method, the coagulant contained in the raffinate can be effectively recycled. It is fed to the coagulation-sedimentation reaction tank 31 for utilization. The extraction agent is discharged from the discharge port 18 and returned to the supply port 115 by the pump 2 for circulation use.
The water is discharged from the tank, returned to the supply port 16 by the pump 3, and used for circulation. In addition, a back-extractant is replenished from the pipe 4 as necessary.

The strip-extracting agent that descends from the outer portion 24 of the solid membrane 20 and strips the metal salt enters the crystallization chamber 5.
As the back-extraction operation continues, the metal salt concentration in the back-extracting agent gradually increases, and metal salt crystals begin to precipitate in the back-extracting agent. The metal salt crystals thus crystallized in the back-extracting agent become flocs and precipitate in the crystallization chamber 5, and are discharged from the outlet 27.

In the apparatus shown in Figure 2, the extraction material and the extraction agent are brought into contact through a solid membrane, but they may also be brought into direct contact without passing through the solid membrane, or from the reverse extraction side discharge side at the bottom of the apparatus. Crystallization chamber 5
However, the crystallization chamber may be provided separately from the casing 1, and the crystallization may be carried out within it.However, as shown in Fig. 2, the crystallization chamber 5 may be provided at the bottom of the extraction device. This has the effect of making the device more compact.

When metals are extracted using a chelate extractant using the apparatus shown in Figure 2, the ratio of the metal concentration in the extractant to the metal concentration in the back-extractant is expressed by the following equation (1). .

For example, when the metal is Cu2+, if the pH of the extraction material is 4 and the pH of the back-extracting agent is 11 or less, it can be concentrated more than 1 million times and crystallization becomes possible.

According to the method of recycling the back-extracting agent and recovering metal salts from the back-extracting agent by crystallization, it is only necessary to add an acid equivalent to the metal to be back-extracted, and there is no need to add external energy to the system. metals can be recovered at low cost.

However, at this time, H+ in the back-extracting agent is consumed by the reaction shown in equation (2) below, so it is necessary to regularly replenish acid to the back-extracting agent or to sub-control the pH.

(CuR) extractant ÷ (H2SO,) back extractant 2 ・ → (2HR) extractant ◆ (Cu S O4) back extractant - (
2) (HR: Chelate extraction agent) In the present invention, the extraction agent and the extraction agent are brought into contact with each other and/or the extraction agent and the back-extraction agent are brought into contact through a solid membrane.

However, it is generally preferable to contact without intervening a solid membrane because the back extraction rate is faster and there is no possibility of crystals adhering to the solid membrane.

When using an extremely hydrophobic solid membrane such as a Teflon membrane, the surface of the solid membrane is covered with the extraction agent, so there is almost no crystal adhesion.For this reason, the extraction rate is slow, but the crystal purity is improved. Conceivable. Therefore, when high purity is required for the recovered material, it is preferable to carry out both the contact between the extraction material and the extraction agent and the contact between the extraction agent and the back-extraction agent through a solid membrane.

In the present invention, various forms of the solid membrane are used, such as a flat membrane type, a tubular type, and a hollow fiber type.

The solid membrane may be porous as long as it is porous. Examples include semipermeable membranes made of polytetrafluoroethylene (rPTFE), cellulose acetate, polysulfone, polyvinyl chloride, polypropylene, polyamide, etc.
FE is preferred.

Generally, PTFE is commercially available as Teflon (trade name). PTFE has excellent chemical resistance and hydrophobicity, and has an extremely high extraction rate, making it suitable for use as a solid membrane. The film thickness, pore diameter, etc. of porous PTFE III are selected depending on the ll1l agent used.

The reason why the extraction rate of the PTFE solid membrane is so fast is not clear, but due to its network structure and extreme hydrophobicity (lipophilicity), the contact area between the extraction agent or the back-extraction agent and the extraction agent is not limited to only the pores. This is presumed to be because it spreads over the entire membrane surface and the diffusion within the membrane is also fast.

In the present invention, when the extractant and the extractant or the extractant and the back-extractant are brought into contact through a solid membrane, the solid membrane is p T
F E III is used, and the extraction agent (or the extraction agent and the extraction agent and the extraction agent and the extraction agent are brought into contact with each other through a solid membrane). In the case of contact, the pressure on the side (hereinafter sometimes referred to as "water side") of the extraction material and back-extracting agent is higher than the pressure on the extraction agent side. There is no leakage of the back extractant to the extraction agent side, and no leakage of the extraction agent to the water side, making it possible to perform extraction efficiently.

If the pressure on the extraction or back extraction open side (water side) is the same as or lower than the pressure in the extraction example, the extraction agent will leak to the water side, making extraction difficult. If it is set higher, there will be no leakage of extractant to the water side. And, PTFE
Due to its remarkable hydrophobicity, even if the pressure on the water side is increased, water will not leak to the extractant side (unless excessive pressure is applied).

The pressure difference between the water side and the extractant side should be 0.01 Kg/crn" or more, but if it becomes larger than 3 Kg/c tn", water leakage may occur.
This pressure difference, which is preferably on the order of O1-3 K g/c rn', can be easily adjusted by adjusting the outlet pressure regulating valve of the extractor or back-extractor.

The method for treating metal-containing water of the present invention is suitable for treating liquids to be treated containing metal salts, such as plating wastewater. Examples of metal salts include Ag, AJI, and Co.

Examples include salts of Cd, Cu, Nf, Fe, Hg, Zn, and the like.

The extraction agent used in the process of extracting metal salts is appropriately selected depending on the above-mentioned substance to be extracted, but general specific examples include:
Examples include (1).

■Chelate extractants such as the following a-d: a, R-CI-OH in the black formula "-CI2H25 in the formula R;-C, H18 ■Organic phosphoric acids such as the dome a-c: a, G2- Acidic organic phosphate esters such as ethylhexyl phosphate.

b, neutral phosphate esters such as +-butyl phosphate;

C-) Phosphine oxides such as polyoctylphosphine oxide.

■Amines such as the following: Primen JMT (manufactured by Robm & Haas) Am
berlite LA2 (//) Alanin
e 336 (Henkellp) Aliquat
Primary to quaternary amines such as 336 (tr).

■Carboxylic acids such as naphthenic acid and versatic acid (manufactured by Shell).

■Crown ethers.

When extracting metal salts, the extractant is usually dissolved in a diluent. Can be used.

Further, a modifier such as a higher alcohol or a pH adjuster such as an acid or alkali may be added to the extraction system.

Mineral acids such as He, H2SO, etc. are often used as back extractants, but when di-2-ethylhexyl phosphate (D2EHPA) is used as the extractant, alkaline agents such as NaOH can also be used. be. In any case, it is preferable to replenish acid, alkali, etc. as appropriate when recycling the back-extracting agent.

Specific combinations of extractants, extractants, and back-extractants include:
For example, those in Table 1 of F are listed.

Table 1 Wood 1: Tributyl phosphate Wood 2: Di-2-ethylhexyl phosphate [Function] After first concentrating the metal-containing water, the concentrated liquid is sent to the extraction process as extract material to extract metals with high extraction efficiency. Extraction can be carried out very advantageously.

However, in the metal extraction process, when the back-extracting agent is used repeatedly, metal salts accumulate in the back-extracting agent, become supersaturated, and precipitate (crystallize).Since the precipitated metal salts are crystalline, dehydration and recovery are extremely difficult. It is easy and can be effectively reused.

Further, by carrying out one or both of the contact between the extraction material and the extraction agent and the contact between the extraction agent and the back-extracting agent through a solid membrane, the purity of the recovered metal can be increased.

[Examples] The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 Cu70ppm discharged from the copper plated product washing process,
Contains Fe61ppm and organic acids such as tartaric acid, COD,
, 140ppmc7) Fe 5 in Cu plating washing wastewater
04” 7H20 was added at 2600 ppm, and Ca(O
The pH was adjusted to 11 with H)2. Add 1 liter of partial hydrolyzate of polyacrylamide, a polymer flocculant, to this solution.
When precipitated by adding ppm, the Cu ions in the obtained supernatant water were 0.2 ppm or less, and the sludge contained C.
It contained 2630pp of Cu and 22000pp of FFe. This sludge is the Cu13 discharged from the electrolytic tank.
400ppm, FFe12200pp, and mixed with that discharge ratio, Cu3730ppm, FFe2
A solution containing 1000pp (hereinafter referred to as "undiluted solution") was used for extraction.

A porous PTFE membrane with an area of 75 crn' was used as a solid membrane (
The above stock solution (pH = 4.1) was added as extraction material to the extraction device shown in Figure 2, which was equipped with a pore size of 0.2 μm (pore size: 0.2 m).
Circulate the liquid at m1/min and add SME-5 to the other side.
29 to 40voi% and Shell Sea Jl/D-70
500 mJL of extractant consisting of 60 vofL% (both manufactured by Shell Chemical) and ml of back extractant of 100 g/l H2SO4 were each examined at 720 m/min, 24
The liquid was circulated at a rate of 0 ml/min. During this liquid passage, the stock solution was
The stock solution was replaced with fresh stock solution every 8 hours. In addition, the H2SO4 concentration of the back extractant was adjusted to 100 g/fL.
onc-H2SO4 was added to the back extractant.

When such extraction and back-extraction processes were continued, Cu SO4.5H20 crystals began to precipitate in the back-extractant when the Cu concentration of the back-extractant reached 66,000 PPm, and the precipitation continued steadily from then on. continued. Its initial extraction rate was on average 15.6 g-Cu/rn'-hr (14
The precipitated Cu S O 4 .5H20 crystals, which had a weight of ~18 g-Cu/rr+'·hr), could be easily dehydrated and recovered. In addition, the raffinate after 48 hours was p
H1,2-1.3, Cu80-110 ppm, F
e20800~21000 ppm, Fe
was hardly extracted, and only Cu was crystallized and recovered. Since this raffinate solution contained a large amount of FeJIJ, it was possible to reuse it as a flocculant.

[Effects] As detailed above, the method for treating metal-containing water of the present invention includes:
First, the metal-containing water is concentrated and then the metal salts are extracted, and the extraction can be carried out efficiently at a high extraction rate. Furthermore, by recycling the back-extracting agent to precipitate the metal salt, the metal salt can be very easily and efficiently recovered in the form of crystals. Moreover, one recovered crystal can be used as p■ as it is. Therefore, the cost of processing the recovered material is significantly reduced, which is extremely advantageous economically and industrially. Further, by carrying out one or both of the contact between the extraction material and the extraction agent and the contact between the extraction agent and the back-extraction agent through a solid membrane, the purity of the recovered metal can be increased.

Furthermore, the method of the present invention overcomes the difficulty of sludge treatment during metal ion recovery.

[Brief explanation of drawings]

FIG. 1 is a system diagram illustrating an example of the method for treating metal-containing water of the present invention, and FIG. 2 is a diagram showing the configuration of an extraction device suitable for carrying out the present invention. l...Device casing, 5...Crystallization chamber, 20...Solid film. 31...Reaction tank. 32... Sedimentation tank, 33... pH adjustment tank, 34... Extraction device.

Claims (4)

[Claims] (1) A method in which metal-containing water is used as an extraction material, the extraction material is brought into contact with an extraction agent, and the extraction agent is then brought into contact with a back-extracting agent to recover metal salts into the back-extracting agent. In addition to pre-concentration, the contact between the extraction material and the extraction agent and/or the contact between the extraction agent and the back-extracting agent is performed through a solid membrane, and the material to be extracted is back-extracted by circulating the back-extracting agent. A method for treating metal-containing water, characterized by crystallizing it from a metal-containing agent. (2) Metal-containing water is subjected to coagulation sedimentation treatment, ion exchange treatment,
The method for treating metal-containing water according to claim 1, wherein the metal-containing water is concentrated by membrane separation treatment or evaporation treatment. (3) The method for treating metal-containing water according to claim 2, characterized in that the metal-containing water is concentrated by coagulation-sedimentation treatment using an iron compound as a flocculant. (4) The method for treating metal-containing water according to any one of claims 1 to 3, wherein the metal-containing water is plating wastewater.