JPH08260161A - Method for recovering ni or zn salt from waste liquid containing ni or zn and ni - Google Patents

Abstract

PURPOSE: To obtain a recovered Ni soln. having g high content of Ni and extremely low in impurities by dissolving a sludge obtained by flocculating and separating an Ni-contg. waste liq. with a mineral acid, regulating the pH to separate SS, dehydrating and purifying the obtained liq. CONSTITUTION: A waste liq. 1 contg. Ni or Zn and Ni is added with Ca(OH)2 in an air oxidation tank 4, further admixed with a high molecular flocculant 3 in a flocculation tank 6, sent to a settling tank 7, flocculated and separated. The treated water 35 is neutralized and then discharged 10. Meanwhile, the flocculated and separated sludge 11 is dissolved with H2 SO4 9, then regulated to pH3 to 5 with NaOH 14 and introduced into a separation tank 15. The separated sludge 17 is dehydrated and reutilized as the raw material for Ni and Zn. Besides, the supernatant liq. 16 is added with NaOH 14 and an inorg. dehydration assistant 23 respectively in a reaction tank 11 and in a mixing tank 22 and dehydrated. The dehydrated cake 19b is dissolved with H2 SO4 9, regulated to pH3 to 4 with NaOH 14, passed successively through a separation tank 26, a UF membrane module 30 and active-carbon adsorption tank 32 and recovered as a recovered Ni soln. 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering Ni or Zn and a Ni salt, and in particular, it can be reused in a plating bath from a waste liquid containing Ni or Zn and Ni discharged from a Ni-based plating plant. The present invention relates to a method for recovering Ni salt or Zn and Ni salt.

[0002]

2. Description of the Related Art In recent years, a large amount of Ni-plated steel sheets or Zn-Ni alloy-plated steel sheets have been produced in steel mills as the value added of products has increased. In the production of such plated steel sheet, a large amount of waste liquid containing Ni or Zn and Ni is discharged from the production line by rinsing the plating liquid adhering to the product after plating with water and dumping out by updating the concentrated plating bath. It Ni of these waste liquids containing Ni
The concentration or Zn and Ni concentration is about 0.01 to 0.1%. In particular, Ni is widely used in various fields as a plating raw material, a raw material for stainless steel, etc., and its price is higher than that of Fe or Zn.

Under such circumstances, Ni recovery is very important from the viewpoint of resource saving. Further, in treating the waste liquid, Ni, which is a heavy metal, is treated from the viewpoint of water quality conservation in public water areas.
Must be removed. Conventionally, coagulation-sedimentation has been performed for the treatment of such heavy metal-containing waste liquids discharged in such a large amount, and the treated water is discharged to public water bodies. The coagulated sedimented sludge generated is dehydrated and then discarded as industrial waste, or is sold to electric furnace manufacturers as a substitute for Ni ore as so-called Yamamoto reduction. However, even when the coagulated sedimented sludge containing Ni is dehydrated as described above, the dehydrated cake contains a large amount of heavy metals other than Zn and Ni such as Fe, Cr, Cu, Pb, and Cd and impurities that are organic substances. Therefore, its utility value is extremely low, and even if it is sold directly as it is, it is not much different from industrial waste.

The present inventors have previously found a method of recovering Ni or Zn and a Ni salt or a Zn and Ni salt that can be used as a Ni plating solution from a coagulation sedimentation sludge of Ni or Zn and a waste liquid containing Ni. (Japanese Patent Application No. 6-148532, hereinafter referred to as the prior application) FIG. 2 shows a process diagram of the recovery method of the prior application. However, according to the technique of this prior application, although it is effective in the method of recovering the Ni salt or Zn and the Ni salt from the organic-free Ni or Zn and the Ni-containing waste liquid, a large amount of the Ni or Zn and the Ni-containing waste liquid is produced. When it is contaminated with organic matter, the technique of the prior application cannot sufficiently separate the organic matter and the Ni salt or the Zn and Ni salt, and the organic matter remains in the Ni salt or the Zn and Ni salt recovered for this reason. However, there was a problem that it could not be reused as a plating solution.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and in the coagulation-sedimentation treatment of waste liquid containing Ni or Zn and Ni, Ni or Zn and Ni-containing sludge, which are generated in a large amount, are mixed with Ni, Impurities such as heavy metals and organic substances other than Zn are extremely small, and high concentration Ni or Zn and N
Ni or Zn capable of obtaining a recovery liquid containing i and reusing the obtained Ni or Zn and the Ni recovery liquid in a plating bath can reduce production cost and save energy and resources. And Ni from waste liquid containing Ni
An object of the present invention is to provide a method for recovering salt or Zn and Ni salt.

[0006]

In order to solve the above problems, the present invention provides a method for recovering Ni or Zn and a Ni-containing waste solution containing purified Ni, Zn and Ni-containing waste solution. The following steps (a) to (f) are sequentially performed, and a method for recovering a Ni salt or Zn and a Ni salt is provided. (A) First step of coagulating and separating Ni or Zn and a waste liquid containing Ni, (b) Second step of dissolving coagulating and separating sludge generated in the first step with mineral acid, (c) Acid dissolution of the second step Third step of adjusting the liquid to pH 3 to 5 with an alkaline agent, (d) third
Fourth step of solid-liquid separation of SS produced in the step, (e) fifth step of adding alkaline agent and inorganic dehydration auxiliary agent to the separated solution of the fourth step, and (f) fifth step of dehydration A sixth step in which the cake is dissolved with a mineral acid, the pH is adjusted with an alkaline agent, and then the produced SS and the inorganic dehydration aid are separated by a membrane. Further, in the present invention, after the step (f), a seventh step of subjecting the membrane-separated water of the sixth step to adsorption of activated carbon may be included.

Next, the present invention will be described in detail. In the first step, Ni or Zn and the Ni-containing waste liquid are coagulated and separated. Specifically, an alkaline agent is added to the waste liquid,
After air oxidation treatment, a polymer coagulant, preferably an anionic polymer coagulant, is added to aggregate and separate heavy metals in the waste liquid as hydroxides. As described above, in the first step, it is desirable to use the alkali agent and the polymer coagulant, especially the anionic polymer coagulant in combination, but the coagulation and precipitation treatment may be performed with the alkali agent alone. The alkaline agent may be slaked lime generally used for waste liquid treatment, slaked lime for tap water, or caustic soda (NaOH). Also, any known polymer flocculant can be used, but both are used. Slaked lime that can be used is preferable. In the first step for coagulating and precipitating the waste liquid, Fe ²⁺ in the waste liquid is converted into Fe by the air oxidation treatment.
³⁺ , and by adding an alkaline agent to the waste liquid, the heavy metals in the waste liquid are converted into hydroxides to cause aggregation and precipitation.

In the second step, a mineral acid is added to the coagulated sedimentation sludge of the first step or the concentrated sludge obtained by concentrating the coagulated sedimentation sludge,
Dissolves heavy metal hydroxides at pH 0.5-2. HCl, HNO ₃ , H ₂ SO ₄ etc. can be used as mineral acid, but CaS
The removal of Ca as O ₄ can be expected, and it is preferable to use H ₂ SO _{4 in} order to obtain the form of NiSO ₄ or ZnSO ₄ often used in plating baths. In the third step, the second
An alkaline agent, especially NaOH, is added to the acid solution of the process to adjust the pH to ³ to 5 to remove Fe ³⁺ as an impurity from Fe.
Change to insoluble in (OH) ₃ .

In the solid-liquid separation in the fourth step, the sludge produced in the third step may be concentrated to a volume of 1 to several% by gravity concentration, centrifugal concentration, membrane separation concentration, etc., and then supplied to the dehydrator. However, if the sludge concentration from the third step is 1% or more, the concentration operation can be omitted and direct dehydration treatment may be performed. As the dehydrator, any of a filter press, a vacuum dehydrator, a centrifugal dehydrator, a belt press and the like can be used. In order to increase the recovery rate of Ni, it is desirable to use a filter press that can reduce the water content of the dehydrated cake as much as possible. Since the dehydrated filtrate at the time of dehydration contains Ni or Zn and Ni, it is returned to the second step. Since the generated dehydrated cake also contains Ni or Zn and Ni, it is reused as a raw material of Ni ore in order to effectively utilize resources.

In the fifth step, the separated liquid from the fourth step, that is,
An alkaline agent, especially NaOH, is added to the concentrated supernatant liquid, the membrane separation liquid or the like to adjust the pH to 10 to 12, and Ni or Zn and Ni in the separation liquid are mixed with insoluble Ni (OH) ₂ or Zn (O
H) Change to ₂ . Next, after adding an inorganic dehydrating auxiliary, the whole amount is dehydrated by a filter press, and Ni (OH) ₂ or Zn (OH) ₂ , Ni (OH) ₂ and the inorganic dehydrating auxiliary are recovered as a dehydrated cake. Inorganic dehydration aids include powdered activated carbon, perlite, diatomaceous earth, activated clay, kaolin, etc.
It is a material that is not dissolved in mineral acid and can be used in the present invention as long as it is in powder form, and its addition amount is 0.1 to 10% relative to the weight of sludge caused by Ni (OH) ₂ and Zn (OH) _2. Is preferred. Further, a dehydration cake washing step can be added to the fifth step.

In the washing step, industrial water, tap water, preferably pure water (demineralized water) is added to the unwashed dewatered cake in the fifth step to remove impurities such as NaC which are easily dissolved in water in the dewatered cake.
It is carried out in order to increase the purity of the recovered Ni or the recovered Zn and Ni by removing 1 and NaSO ₄ . After extracting the impurities from the dehydrated cake to the water side, the impurities may be removed from the system together with the dehydrated filtrate by a dehydration operation, if necessary. The washing of the dehydrated cake or the washing and dehydrating operations can be repeated once to several times. The dehydrated filtrate and the dehydrated filtrate after the washing operation are returned to the first step.

In the sixth step, Ni (OH) ₂ or Zn is used.
After dissolving the dehydrated cake of the fifth step containing (OH) ₂ , Ni (OH) ₂ and an inorganic dehydration aid with mineral acid, the pH was adjusted with an alkaline agent.
Adjusted to 8-12, Ni (OH) ₂ and Zn (OH) ₂
Dissolve. The undissolved inorganic dehydration aid is removed by membrane separation to obtain membrane separated water. This membrane-separated water becomes a recovery liquid containing Ni salt or Ni and Zn salt. When the SS concentration of the undissolved inorganic dehydration aid or the like is 1% or more, it is necessary to remove the SS in advance before the membrane separation.
The SS removing means may be carried out by a method such as dehydration, filtration or sedimentation separation, but it is preferable to use sedimentation separation because the operation is simple and the equipment cost is low. TOC of 10 mg / liter or more in the membrane separation water of the sixth step
When the water remains, the membrane-separated water is subjected to activated carbon adsorption treatment to remove organic substances. The activated carbon is preferably fibrous activated carbon.

Next, an example of a method for recovering Zn and Ni from a waste liquid containing Zn and Ni according to the present invention will be described with reference to FIG. First step: Zn, Ni-containing waste liquid (1) is introduced into an air oxidation tank (4) having an air diffuser, Ca (OH) ₂ (2) is added, and air oxidation is performed to thereby Fe ^{2 in the} waste liquid. ⁺ Is oxidized to Fe ³⁺ , and all become Fe (OH) ₃ .
On the other hand, Ni and Zn become Ni (OH) ₂ and Zn (OH) ₂ and are all insolubilized. These three types of hydroxide and N
SS originally present in waste liquid containing i or Ni and Zn
In the coagulation tank (6), the polymer coagulant (3) is added for coagulation treatment. The SS produced here is a settling tank (7)
The solid-liquid separation is carried out into coagulation-sedimentation treated water (35) and coagulation-sedimentation sludge (11). The coagulation sedimentation treated water is discharged after being neutralized with H ₂ SO ₄ (9) in the neutralization tank (8).

Second step: The heavy metal hydroxide in the coagulation sedimentation sludge (11) is No. H ₂ in one dissolution tank (12)
SO ₄ was added and dissolved in PH0.5～2. N
o. In addition to the coagulating sedimentation sludge (11), No.
No. 1 dehydrated filtrate (20a) and No. 1 2 The dehydrated cake slurry (28) is introduced, and Ni and Zn remaining in the liquid are recovered in this step and the following third and fourth steps. Third step: No. 1 was added to the acid solution of the second step. NaOH (14) is added in a pH adjusting tank (13) to adjust the pH to 3-5. Here, the impurities Fe ³⁺ are replaced with Fe (O
H) Change to insoluble in ₃ . Fourth step: CaSO ₄ produced in the second step and SS produced in the third step are No. Solid-liquid separation is performed in the 1SS separation tank (15). The supernatant liquid (16) is sent to the next step. The solid-liquid separated No. 1 dehydrated cake slurry (17) is N
o. It is dehydrated with 1 filter press (18a). The No. No. 1 dehydrated cake (19a) was reused as an ore of Ni and Zn. The 1-dehydrated filtrate (20a) is returned to the second step as described above.

Fifth step: p of the supernatant (16) of the fourth step
NaOH in the reaction tank (21) so that H becomes 10-12.
Is added. Next, powdered activated carbon (100 to 200 mesh) (23), which is an inorganic dehydration aid, is added to the mixing tank (22). The amount of powdered activated carbon added is 1 to 50% per SS in the reaction tank (21). After that, the total amount is N
o. No. 2 filter press (18b) was used for dehydration. Two
The dehydrated filtrate (20b) is returned to the first step. The main purpose of adding activated carbon in this step is as a dehydration aid, but it is also the purpose of removing organic substances contained in the process water.

No. No. 2 dehydrated cake (19b) is No. Two
The total of Ni concentration and Zn concentration in the melting tank (24) is 100 m.
Diluting water (36) was injected so as to be less than or equal to g / liter, and H ₂ SO ₄ was added to add N in the dehydrated cake.
i (OH) ₂ and Zn (OH) ₂ are dissolved while maintaining pH 0.5-2. Demineralized water or tap water can be used as the diluting water, and the amount of the water is Ni or Zn or Ni + Z in the recovered liquid.
It is added so that the n concentration becomes about 100 g / liter.
Next, No. 2 pH adjusting tank (25) with NaOH (14)
Is added to adjust the pH to 3-5, which is suitable for recovery and reuse. No. In the 2SS separation tank (26), the powdered activated carbon (23) added in the fifth step is separated. The powdered activated carbon is No. It is returned to the second step as the 2-dehydrated cake slurry (28), dehydrated in the fourth step, and removed outside the recovery system of the present invention.

Sixth step: No. The supernatant of the 2SS separation tank (26) is guided to the UF raw water tank (27) and supplied to the UF membrane module (30) having a molecular weight cutoff of 20,000 to 100,000, and fine SS in the supernatant is obtained. To be removed. UF concentrate (2
9) are UF raw water tank (27) and No. 9 respectively. It is returned to the 2 pH adjusting tank (25). In order to maintain the SS concentration in the UF raw water tank at 2% or less, the SS in the UF concentrate (29) was changed to No.
Remove in 2SS separation tank. 7th step: The UF membrane permeate (31) is passed through an activated carbon adsorption tower (3
Water is passed to 2) at an SV of 3 liter / h or less. As a result, the organic substances remaining in the UF membrane permeation liquid (31) and adversely affecting the plating property are adsorbed and removed. The activated carbon adsorption tower outlet water from which the organic substances have been removed is used as Ni or Zn and Ni recovery liquid (3
3) It is reused in the plating bath.

[0018]

Most of the organic substances in the waste liquid containing Ni and Zn are Ni (OH) ₂ and Zn (OH) ₂ produced in the waste liquid treatment process.
Is adsorbed on and is transferred to the coagulating sedimentation sludge and the concentration of the organic matter is concentrated. According to the prior application, the coagulated sedimented sludge is dissolved with a mineral acid to form Ni and Zn salts, and then F which is an impurity.
Only solid-liquid separation of e (OH) ₃ and CaSO ₄
The organic substances transferred from the Ni, Zn waste liquid are directly Ni, Zn
High concentration remains in the recovered liquid. Even if it is attempted to remove all such high-concentration organic substances by activated carbon adsorption, it is extremely difficult to completely remove them.

On the other hand, according to the present invention, Fe that easily dissolves coagulated sedimented sludge containing an organic matter with mineral acid and neutralizes it to form Fe
First, (OH) ₃ and CaSO ₄ are removed, and then the target components Zn and Ni are separated into solid and liquid as hydroxides. From a liquid containing such a large amount of organic matter, Zn (O
It can be separated into H) ₂ and Ni (OH) ₂ and dissolved again with mineral acid to obtain a Zn / Ni recovery liquid containing very few impurities, and trace amounts of organic substances remain in the Zn / Ni recovery liquid. In some cases, it is possible to remove by adsorption with activated carbon.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 According to the process chart shown in FIG. 1, Zn, Ni salt was recovered as follows from the Zn, Ni-containing waste liquid having the following properties. pH: 5.8 Ni: 500 mg / liter Zn: 243 mg / liter SS: 3 mg / liter T-Fe: 10 mg / liter TOC: 880 mg / liter TOC is an index representing organic matter concentration in organic carbon. is there.

In the air oxidation tank (4), the Zn, N
To the i-containing waste solution, Ca (OH) ₂ (Wako Pure Chemical Industries, Ltd. reagent, for chemistry) 1300 mg / liter was added to adjust the pH.
Was adjusted to 7 and air was blown into the waste liquid from the air diffuser pipe (5) in the air oxidation tank (4) to perform air oxidation treatment for 30 minutes. Next, Ca (O
H) ₂ was added to adjust the pH of the solution to 10 by adding 1700 mg / liter in total, and then the solution was added to the precipitation tank (7).
Coagulation and precipitation treatment was carried out. The water quality of the coagulation sedimentation treated water (35) is as follows. pH: 10 Ni: 1 mg / liter Zn: 1 mg / liter SS: 1 mg / liter T-Fe: 0.1 mg / liter TOC: 65 mg / liter

When the generated coagulated sedimented sludge is left to stand in the sedimentation tank (7) for about 18 hours, the concentration of the concentrated sludge becomes 10 kg /
It became m ³ . No. 1 dissolution tank (12)
When H ₂ SO ₄ was added therein, CaSO ₄ was produced. At that time the pH was 1. Next, No. 1 pH adjustment tank (1
In step 3), NaOH was added to adjust the pH to 4 so that Fe ³⁺ as an impurity becomes insoluble in Fe (OH) _3.
aSO ₄ together with No. In the 1SS separation tank (15),
The supernatant (16) and No. 1 dehydrated cake slurry (17)
Solid-liquid separation is carried out. No. 1 dehydrated cake slurry is N
o. The dehydrated cake having a water content of 70%, which was dehydrated by a filter press (18a), is reused as a substitute for ore of Ni.

The composition of the dehydrated cake per dry weight is as follows. _{Ni (OH) 2: 16%} Zn (OH) 2: 10% Fe (OH) 3: 8% CaSO 4: 89% recovered dewatering filtrate containing Ni and Zn in the target No. 1 Returned to the dissolution tank (12). Supernatant containing Ni and Zn (16)
Was adjusted to pH 11 by adding NaOH in the reaction tank (21), Ni to Ni (OH) ₂ and Zn to Zn (OH) 2.
Set to ₂ and insolubilize. Next, in the mixing tank (22), powdered activated carbon (EVA DIA, manufactured by EBARA CORPORATION) is SS
10% was added and the mixture was stirred for about 15 minutes.

No. 1 in the state of containing powdered activated carbon. No. 2 with a water content of 70% was dehydrated with a filter press (18b).
2 Dehydrated cake (19b) was obtained. The composition per dry weight of this dehydrated cake is as follows. Ni (OH) ₂ : 61% Zn (OH) ₂ : 29% Others (activated carbon): 10% Since the dehydrated filtrate (20b) contains several 10 mg / liter of SS containing activated carbon as a main component, an air oxidation tank. Return to (4). On the other hand, No. No. 2 dehydrated cake (19b) is No. Two
The total of Ni concentration and Zn concentration in the melting tank (24) is 100 g.
Demineralized water was injected as dilution water (36) so as to be not more than 1 / liter, H ₂ SO ₄ was added, and the mixture was stirred for 30 minutes while maintaining pH 2 to dissolve it.

After that, by adding NaOH to adjust the pH to 4, a water area load of 5 mm / min and a residence time of 6 hours were used.
o. In the 2SS separation tank (26), precipitable SS was removed in advance. The solid-liquid separated No. 2 S in the dehydrated slurry (28)
S is No. Returning to No. 1 dissolution tank (12), No. 1 1SS separation tank or No. It is discharged to the outside of the recovery system of the present invention by 1 filter press (18a). No. The SS concentration of the supernatant from the 2SS separation tank (26) is 300 mg / liter,
This supernatant is used as a polysulfone-based UF having a molecular weight cut off of 20,000.
A tubular module (30) incorporating a membrane (membrane area: 0.
034m ² ), membrane surface velocity: 2 m / sec, operating pressure: 2 k
Water was continuously supplied under the conditions of gf / cm ² and the amount of the supplied liquid: 2 liters / hour. The permeated liquid volume at this time is about 1 liter /
It was time.

The properties of the Zn and Ni recovery solution obtained in the present invention are as follows, and the quality was sufficiently reusable as a plating bath. pH: 4.0 SS: 1 mg / liter or less Ni: 66 g / liter Zn: 32 g / liter T-Fe: 0.1 mg / liter or less Pb: 0.1 mg / liter Cu: 0.1 mg / liter Liters Cd: 0.1 mg / liter or less Cr: 0.1 mg / liter or less TOC: 3 mg / liter or less

Example 2 A Zn, Ni salt recovery experiment was carried out in the same manner as in Example 1 using the waste liquid containing Zn and Ni having the same TOC content of 1360 mg / liter and other liquid compositions as in Example 1. The composition of the obtained UF membrane permeate was as follows. pH: 4.0 SS: 1 mg / liter or less Ni: 66 g / liter Zn: 32 g / liter T-Fe: 0.1 mg / liter or less Pb: 0.1 mg / liter Cu: 0.1 mg / liter Liters Cd: 0.1 mg / liter or less Cr: 0.1 mg / liter or less TOC: 13 mg / liter The activated carbon adsorption tower (32) filled with the UF membrane permeated liquid (31) is a SV: 1. Water is passed at liter / h,
When the organic matter was removed, the TOC of the Zn and Ni recovery liquid was 4 mg / liter, and the obtained Zn and Ni recovery liquid had a quality that was sufficiently reusable as a plating bath.

Comparative Example 1 A Zn, Ni salt recovery experiment was carried out according to the process shown in FIG. Using the same Zn, Ni-containing waste liquid as that used in Example 1, the same conditions as in Example 1 were used in the air oxidation tank (4), the flocculation tank (6) and the precipitation tank (7) shown in FIG. Coagulation-precipitation treatment was performed. The coagulated sedimented sludge (11), which was allowed to stand for about 18 hours in the sedimentation tank (7), was filtered (1
As a result of dehydration under the conditions of 1) in which the pressing pressure was 15 kg / cm and the pressing time was 15 minutes, the water content of the dehydrated cake (19) was 75%.
Became.

The composition of the obtained dehydrated cake (19) per dry weight was as follows. _{Ni (OH) 2: 51%} Zn (OH) 2: 24% Fe (OH) 3: 1% CaSO 4: 14% Feed the dehydrated cake 14kg to dissolving tank (12), H ₂ SO ₄ in the dissolution vessel ( 9) was added and the dehydrated cake was dissolved while maintaining the pH at 1. Undissolved residue is N
o. It separated in the 1SS separation tank (15). This supernatant liquid is sent to the pH adjusting tank (13), and NaOH is added in the pH adjusting tank.
(14) was added and the mixture was stirred for 30 minutes while maintaining the pH at 4. The resulting SS such as Fe (OH) ₃ was added to No. 5 having a water area load of 5 mm / min or less. 2SS separation tank (26)
Then, SS which is apt to settle was removed in advance.

No. The SS concentration of the supernatant from the 2SS separation tank was 1%, and this supernatant was incorporated into a tubular module (3 with a polysulfone UF membrane having a molecular weight cut off of 20,000).
0) (membrane area: 0.034 m ² ), membrane surface velocity: 2 m /
Water was continuously supplied under the conditions of seconds, operating pressure: 2 kgf / cm ² , and supply amount of liquid: 2 liters / hour. The amount of permeated liquid at this time was about 0.8 liter / hour. Then this UF
The membrane permeated liquid (31) was sent to an activated carbon adsorption tower (32) using activated carbon fibers, and organic matter in the liquid was removed in the activated carbon adsorption tower. TOC of the obtained Zn, Ni recovery liquid (33)
Since the concentration is as high as 160 mg / liter, it is difficult to reuse it as a plating bath.

[0031]

INDUSTRIAL APPLICABILITY According to the present invention, in the coagulation / precipitation treatment of the Ni recovery liquid, it was possible to obtain a Ni recovery liquid containing a high concentration of Ni and containing very few impurities from a large amount of high Ni-containing sludge. . By reusing the obtained Ni recovery liquid in the plating bath, it greatly contributes to reduction of production cost, energy saving and resource saving.

[Brief description of drawings]

FIG. 1 is a process diagram showing an example of an apparatus used in a recovery method of the present invention.

FIG. 2 is a process drawing of an apparatus used in a comparative example.

[Explanation of symbols]

1: Waste liquid containing Zn and Ni, 2: Ca (OH) ₂ , 3: Polymer coagulant, 4: Air oxidation tank, 5: Air diffuser, 6: Coagulation tank, 7: Settling tank, 8: Neutralization tank , 9: H ₂ SO ₄ , 1
0: discharged water, 11: coagulated sedimentation sludge, 12: No. 1 melting tank, 13: No. 1 pH adjusting tank, 14: NaOH, 1
5: No. 1SS separation tank, 16: supernatant, 17: No.
1 dehydrated cake slurry, 18a: No. 1 filter press, 18b: No. 2 filter press, 19a: N
o. 1 dehydrated cake, 19b: No. 2 dehydrated cakes, 20
a: No. 1 dehydrated filtrate, 20b: No. 2 dehydrated filtrate, 2
1: reaction tank, 22: mixing tank, 23: inorganic dehydration aid, 2
4: No. 2 dissolution tank, 25: No. 2 pH adjusting tank, 2
6: No. 2SS separation tank, 27: UF raw water tank, 28: N
o. 2 dehydrated cake slurry, 29: UF concentrated liquid, 30:
UF membrane module, 31: UF membrane permeate, 32: activated carbon adsorption tower, 33: Zn, Ni recovery liquid, 34: stirrer, 3
5: coagulation sedimentation treated water, 36: dilution water

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Katsuji Kitajima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor, Keiichi Shoda 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd.

Claims (2)

[Claims] 1. A method for recovering a solution containing Ni or Zn and a salt thereof purified from a waste solution containing Ni, characterized in that the following steps (a) to (f) are sequentially performed.
Method for recovering salt or Zn and Ni salt. (A) First step of coagulating and separating Ni or Zn and a waste liquid containing Ni, (b) Second step of dissolving coagulating and separating sludge generated in the first step with mineral acid, (c) Acid dissolution of the second step Third step of adjusting the liquid to pH 3 to 5 with an alkaline agent, (d) third
Fourth step of solid-liquid separation of SS produced in the step, (e) fifth step of adding alkaline agent and inorganic dehydration auxiliary agent to the separated solution of the fourth step, and (f) fifth step of dehydration A sixth step in which the cake is dissolved with a mineral acid, the pH is adjusted with an alkaline agent, and then the produced SS and the inorganic dehydration aid are separated by a membrane. 2. The method for recovering Ni salt or Zn and Ni salt according to claim 1, further comprising a seventh step after the step (f) in which the membrane-separated water in the sixth step is subjected to activated carbon adsorption treatment. .