JPS5819498A - Treatment method for Metsuki wastewater - Google Patents

Abstract

PURPOSE:To treat Ni-, Zn-contg. waste liq. of plating economically with one time of treatment by adding Fe<2+>-contg. liq. to said waste liq. to control its pH and separating Zn(OH)2 and Ni(OH)2 together with Fe(OH)3 by condeposition. CONSTITUTION:Ni<2+>-, Zn<2+>-contg. waste liq. A of rinsing and Fe<2+>-contg. waste liq. B of pickling and rinsing are conducted to the 1st aerating and pH controlling tank 1 then to the 2nd aerating and pH controlling tank 2. Here, the pH of the liqs. A, B is controlled to 8.5-9.5 by using Ca(OH)2 or NaOH, and air is blown thereto through a pressurized air conduit 3 to mix and aerate the liq. of the tank 1 or 2. By said treatment, Zn(OH)2 and Ni(OH)2 are codeposited together with Fe(OH)3. After the sediment is separated away from the bottom part by a clarifier 4, the supernatant is passed through a storage tank 5 then through a quick filter 7 with a pump 6. After hydrochloric acid D is added to the liq. to control its pH in a neutralizing tank 8, the liq. is discharged as waste water E to the outside of the system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for removing Ni from wastewater from Ni-Zn alloy plating equipment.
, relates to a method for treating plating wastewater containing Zn.

Methods for treating wastewater containing heavy metals, such as rinsing wastewater from plating equipment, include an alkali neutralization method and an ion exchange method. The former alkali neutralization method is a method performed in combination with PI (adjustment and coagulation sedimentation (incorporating 1 filtration at the end if necessary)) and is often applied when the amount of wastewater is large.The latter ion exchange method is a method that selectively captures and recovers heavy metals using ion exchange resin, which has the advantage of being able to reuse heavy metals, but when the concentration of heavy metals in wastewater is low, it results in extremely inefficient operation. In addition, if the amount of wastewater is large, large-scale treatment equipment is required.From this point of view, when the concentration of heavy metals is low and the amount of wastewater is large, such as in rinsing wastewater from plating equipment, alkali treatment is recommended. The neutralization law is usually applied.

I am a connoisseur.

By the way, when rinsing waste water from Ni-Zn alloy plating equipment is targeted, the heavy metals that must be removed are Ni.
There are two types: Zn. The pH of Zn"+ is determined by the solubility product of the heavy metals contained and the wastewater standards (normally 1.0 PPM or less is the target).
)t, and Ni''+ precipitates as Ni (
Precipitate with OH)x.

Therefore, when treating rinsing wastewater from Ni-Zn alloy plating equipment where the optimum pH range of the basins for precipitating metal hydroxide differs, it is not possible to perform the rinsing process in one cycle; Adjust the pH to 8~9 and add Zn
(OH)2 is precipitated and Zn (OH) is separated by precipitation.
2 was removed, and then the pH was adjusted to 9 to 10 and Ni (O
H) 2 is precipitated and subjected to precipitation separation.Ni(OH)2
After the Ni(DH)z is precipitated, the Ni(DH)z is removed by precipitation separation, followed by rapid filtration, final pH adjustment, and then draining.

However, in this method, the PH adjustment operation and the precipitation separation operation are repeated twice, which is not rational, and when continuous wastewater treatment is performed, two sets of the same treatment equipment must be installed, which is not economical.

The present invention was proposed to solve such problems,
The purpose of the present invention is to provide an economical plating wastewater treatment method that requires only one treatment instead of the conventional two-time treatment.To achieve this purpose, the present invention
A Fe-containing liquid was added to the plating wastewater containing Ni and Zn, and the pH was adjusted to 8.5 to 9.5 to remove Fe.
(OH) s is precipitated, and at that time Zn (OH) 2 and Ni (OH) 2 are eutectoid and separated and removed.

As mentioned above, the precipitation regions of Zn and Ni coincide at pH = 9, so if the pH is adjusted accurately to 9, Zn
(OH) 2 and Ni (OH) 2 can be precipitated simultaneously. However, in actual equipment, even if the pH is adjusted to 9, the pH will fluctuate in the range of 8.5 to 9.5, making it difficult to lower Zn 2'' + Nt ''+ to the emission standard. be. Here, as a result of intensive research in order to eutectoid Zn (OH)2 and Ni (OH)2 and remove them at once, the present inventor found that it is possible to eutectoid by adding and mixing Fe''+ containing liquid. I found out.

That is, plating wastewater containing Ni and Zn is mixed with a Fe2+-containing liquid, preferably pickling rinse wastewater containing Fe2+ discharged from other processes in the factory, and the mixture is heated to pH=8 while being aerated.
．． If adjusted to 5 to 9.5, Fe(OH)s to precipitate
It was discovered that Zn(OH)2 and Ni(OH)2 are forcibly precipitated with Zn(OH)2 acting as a nucleus.

The precipitation region of Fe(OH)s is PH=8.0 or higher, and the precipitation region of Zn(OH)z in the addition state of Fe2+-containing liquid is approximately 8.0 to 9.5, Ni(OH)2. The precipitation range is approximately 8.5-10.0. Therefore, PH=8.5
~9. In the region of s, there is an overlapping region where both Zn(OH)2 and N1(OHh) precipitate.
When adjusted to ~9.5, Zn2+ and Ni2+ co-deposit as 0, so if this is separated and removed, one treatment is sufficient.

For pH adjustment, Ca(OH)2, NaOH, or the like can be used. The Ni, Zn-containing plating wastewater and the Fe2+-containing liquid may be mixed by aeration using compressed air, or by using an appropriate method such as a method of rapidly stirring the surface. Furthermore, various combinations of processing equipment are possible.

If pickling rinse wastewater containing Fe2+ is used as the Fe2+-containing liquid, this wastewater treatment becomes possible and is extremely economical, which is a preferred embodiment. An example of the treatment apparatus according to the present invention will be explained with reference to the drawings. Then, Ni”, Zn
``The 10-containing rinsing wastewater A and the Fe2+-containing wastewater B are
It is led to the aeration PH adjustment tank 1. A compressed air conduit 3 is provided at the bottom of the first aeration PH adjustment tank 1 and the second aeration PH adjustment tank 2, and the air blown out from each outlet of this conduit 3 mixes the liquid in the tank 1 or 2. Alkaline IJC such as Ca(OH)2 or NaOH is added to OPH adjustment tanks 1 and 2 for aeration, and the pH of the liquid is adjusted to 8.5 to 9.5.
is adjusted to The treatment liquid in the first aeration PR adjustment tank 1 is
Sequentially transfer to aeration PH adjustment tank 2. The treated liquid in the second aeration PH adjustment tank 2 is supplied to a sedimentation separation device, for example, a keralifier 4, and the sediment is removed from the bottom. The P solution is guided to a rapid filter 7 and supplied to a post-neutralization tank 8 . In the post-neutralization tank 8, an acid such as hydrochloric acid is added to
．． After being neutralized to 5, it is discharged as wastewater E to the outside of the system.

-When processed with the processing equipment shown in the drawing and the case of the above-mentioned 2
When I compared the processing performance with the method of performing multiple processing,
As shown in the following table, according to the method of the present invention, a marked improvement in processing performance was observed. The treatment conditions are also shown in the same table.

As described above, the present invention applies F to wastewater containing Ni and Zn.
Since the e2+-containing liquid is added to adjust the pH to 8.5 to 9.5, when precipitating Fe(O)fla, Zn(OH
)2 and Ni(OH)2 can be eutectoid.

Therefore, pH adjustment and separation and removal of precipitates can be carried out in one treatment, which has great operational and economical effects.

Furthermore, the treatment efficiency is higher than that of conventional methods, and there are great advantages in terms of pollution prevention.

In addition, if Fe2+-containing pickling rinse wastewater is used as the p62+-containing liquid, it is also possible to treat this rinse wastewater.
It is extremely economical.

[Brief explanation of drawings]

The drawing is a flow sheet showing an example of processing equipment for carrying out the method of the present invention. 1.2...PH adjustment tank 3...Pressed air conduit 4...Clarifier
7... Rapid r-passage device 8... Post-neutralization tank A...
・Ni" * Zn" containing rinsing wastewater B...Fe
2+ containing wastewater patent applicant Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] (1) Adding Fe to plating wastewater containing Ni*Zn
In addition to adding the + containing liquid, the pH was adjusted to 8.5 to 9.5 to precipitate Fe 0)
A method for treating plating wastewater, characterized by eutectoiding and separating and removing (OH)z and Ni (OB)z.