JP3396919B2 - Water recovery method from fluorine-containing water - Google Patents

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 water from fluorine-containing water, and in particular, the water after fluorine is removed from fluorine-containing water discharged from semiconductor factories is used as pure water with high recovery rate. It relates to a method of recovering at low cost.

[0002]

Fluorine-containing water discharged from semiconductor factories is generally added with calcium salts such as calcium chloride (CaCl ₂ ) and calcium hydroxide (Ca (OH) ₂ ) in an amount of 2 to 10 times the fluorine concentration. Then, the generated calcium fluoride (CaF ₂ ) is subjected to solid-liquid separation for detoxification treatment.

[0003]

In the above conventional method for treating fluorine-containing water, the amount of salt in the treated water is extremely large because excessive calcium ions and chlorine ions are dissolved in the water. Therefore, in order to purify this treated water by ion exchange treatment, the frequency of regeneration of the ion exchange resin becomes extremely high, and therefore a large amount of regenerant is required, which is economically disadvantageous.

For this reason, in the conventional treatment of fluorine-containing water, treated water, that is, separated water obtained by adding calcium salt to fluorine-containing water and performing solid-liquid separation of calcium fluoride, is used for purification. It was discarded without recovery and reuse.

Incidentally, among the fluorine-containing water, it has been attempted to purify water containing fluorine as hydrofluoric acid by ion exchange treatment using a weakly basic anion exchange resin. However, in this treatment, a waste liquid containing sodium fluoride at a high concentration is generated as a waste liquid for regeneration of the ion exchange resin. For this reason, there is a drawback that enormous cost is required for removing fluorine and desalting the recycled waste liquid.

The present invention solves the above-mentioned conventional problems, and provides a method for recovering water from fluorine-containing water, which makes it possible to recover water from fluorine-containing water at a high water recovery rate at low cost and reuse it. The purpose is to do.

[0007]

According to a first aspect of the present invention, there is provided a method of recovering water from fluorine-containing water, which comprises charging the fluorine-containing water with calcium carbonate.
It is a method of collecting water from the fluorine-containing water that flows through the packing tower.
Te, fluorine containing water calcium carbonate in the packed column flow
Calcium fluoride is fluorinated by flowing water upward at a circulation speed
In the packed tower by the passage of water after fixing
Decarbonated of the generated carbonate ions, and <br/> be characterized for performing desalting.

The method for recovering water from fluorine-containing water according to claim 2 is a method for passing the fluorine-containing water through a calcium carbonate packed tower.
A water recovery method from Tsu-containing water, the fluorine containing water
Upward at a velocity of calcium carbonate of said packed tower to flow
After flowing water to fix the fluorine as calcium fluoride , the cation-exchange resin packed tower and the water flow to fill the above
Decarbonation tower to remove carbonate ions generated in the Hamato, and characterized in that it passed through in the order of the anion-exchange resin packed column.

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

FIG. 1 is a system diagram showing an embodiment of a method for recovering water from fluorine-containing water according to the present invention.

In FIG. 1, 1 is calcium carbonate (Ca
CO ₃ ) packed column, 2 is an H-type cation exchange resin packed column, 3
Is a decarboxylation (CO ₂ ) tower, 4 is an OH type anion exchange resin packed tower, and 11 to 16 are pipes.

In the method of this embodiment, first, the fluorine-containing water, which is raw water, is passed through the pipe 11 to the CaCO ₃ packed tower 1 to contain the fluorine contained in calcium fluoride (CaF).
₂ ) Fix and remove.

CaC to be packed in this CaCO ₃ packed tower 1
There is no particular limitation on the particle size of O ₃ , and a small particle size is preferable from the viewpoint of reaction rate with fluorine, and a large particle size is preferable from the viewpoint of handleability. From the viewpoint of the above, in the usual case, a particle diameter of about 0.15 to 1.0 mm is preferable.

Further, the treatment with the CaCO ₃ packed tower may be a one-column system or a multi-stage system in which a plurality of packed towers are arranged in series to pass water. A merry-go-round method in which the order of water is sequentially changed may be used.

[0015] The water flow system of the CaCO ₃ packed column, C a
In the process of CO ₃ is CaF ₂ by the reaction, in order to prevent occurring the sticking phenomenon of the particles, the upward flow water and a flow rate of flowing the filter medium (CaCO ₃₎ <br/> you.

[0016] In reactions with CaCO _3, water flowing out of the CaCO ₃ packed column 1 fluorine has been removed, pipe optionally 1
After mixing industrial water and the like from 3, the water is passed through the pipe 12 to the H-shaped cation exchange resin packed tower 2. Then, it is introduced into the decarbonation tower 3 through a pipe 14 for treatment, and further, an OH is fed through a pipe 15.
Water is passed through the shaped anion exchange resin packed tower 4.

By such ion exchange treatment, CaC
Since the salt content in the outflow water of the O ₃ packed tower 1 is efficiently desalted to obtain high-quality pure water, the outflow water of the OH type anion exchange resin packed tower 4 is treated as treated water through the pipe 16. It can be discharged to the outside and reused as pure water or raw water in the ultrapure water manufacturing process.

The cation exchange resin to be filled in H Katachihi ion exchange resin column 2, strongly acidic, weakly acidic, or may be any of these mixed systems, also, OH-type anion exchange resin packed column The anion exchange resin to be filled in No. 4 may be strongly basic, weakly basic, or a mixed system thereof.

The decarbonation tower 3 is provided between the H-type cation exchange resin packed tower 2 and the OH type anion exchange resin packed tower 4 to release the dissolved CO ₂ gas in the low pH water after the cation exchange resin treatment. After the treatment, the anion exchange resin treatment is advantageous because the ion load on the ion exchange resin can be reduced. As the decarbonation tower 3, an air aeration tower, a nitrogen aeration tower, or a vacuum deaeration tower can be used.

As the fluorine-containing water of the raw water, the high-concentration fluorine-containing water and the low-concentration fluorine-containing water may be treated separately, or may be mixed and treated. Also, Ca
As shown in the figure, the effluent of the CO ₃ packed tower can be treated by mixing it with industrial water such as dilute low-concentration waste water or river water. After the treatment or after mixing with industrial water, the flocculation treatment or the filtration treatment may be performed.

The illustrated method is an embodiment of the present invention,
The present invention is not limited to the illustrated embodiments unless it exceeds the gist.

For example, in the method shown in FIG. 1, CaCO ₃
Ion exchange method is used for desalination treatment of the effluent of the packed tower. It is possible to employ a combination of the above, and further evaporation treatment. The evaporation treatment is advantageous when the high-concentration fluorine-containing water is separately treated.

[0023]

The present invention prevents the increase of salt content in treated water, which is a drawback of the conventional method, fixes fluorine as CaF ₂ , and purifies the treated water by desalting treatment such as ion exchange treatment. According to the present invention, fluoride ions in raw water are removed by the following reaction.

[0024]

[Chemical 1]

The reaction between fluorine and CaCO ₃ is carried out in a fixed bed,
Either a fluidized bed may be used, but if CaCO ₃ is added to the reaction tank and a fluidized bed is used in which solid-liquid separation is performed after the reaction with fluorine, the separated solid matter becomes a mixed system of CaF ₂ and CaCO ₃ , and the utilization of CaCO ₃ Low rate, low purity as CaF _{2 and} low value for reuse. In addition, there are drawbacks such as the need for dehydration treatment. Therefore, in the present invention, we adopt a packed tower type filtration type.

The CaCO ₃ fluorine content of the packed column effluent is significantly lower, although the slight increase in the carbonate ion present, the other salinity increases little, and therefore, removal of the effluent
By performing the carbonic acid treatment and the desalting treatment, water can be recovered as pure water at a high recovery rate at a low cost.

Moreover, in the method of the present invention, since the salt content in the CaCO ₃ packed tower effluent does not increase, the amount of ash in the closed treatment can be reduced, and the fluorine-containing sludge is separated and recovered from the CaCO ₃ packed tower to be recovered. It can also be used and is industrially extremely advantageous.

[0028]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 Fluorine-containing water of the water quality shown in Table 1 discharged from a semiconductor factory was treated according to the method shown in FIG. The specifications of each packed column are as follows. An air aeration tower using a diffuser was installed as the decarbonation tower.

CaCO ₃ packed tower CaCO ₃ particle size: diameter 0.32 mm CaCO ₃ packed amount: 200 ml (filling height 280 mm) Water flow rate: 400 ml / hr H type cation exchange resin packed tower cation exchange resin: hydrochloric acid Regenerated and washed H type strong acidic cation exchange resin resin filling amount: 50 ml Water flow rate: 400 ml / hr OH type anion exchange resin packed column Anion exchange resin: OH type strong basic anion regenerated with caustic soda Exchange resin Resin filling amount: 50 ml Water flow rate: 400 ml / hr Table 1 shows the water quality of the outflow water of the CaCO ₃ packed tower after the continuous water treatment for 48 hours.

[0031]

[Table 1]

Table 2 shows the change with time (corresponding to the amount of treated water) in the electrical conductivity of the treated water (the water discharged from the OH type anion exchange resin packed tower).

[0033]Comparative Example 1 The same procedure as in Example 1 was repeated except that no decarbonation tower was provided.
became. Table 2 shows the changes over time in the electrical conductivity of the treated water.

Comparative ExampleTwo CaCO_ThreeOther than not having packed tower and decarbonation tower
Was performed in the same manner as in Example 1. Electric conductivity of treated water
Table 2 shows the changes over time.

Comparative ExampleThree 7600 mg of calcium hydroxide in raw water of the water quality shown in Table 1
/ L, sulfuric acid 5500mg / l was added for coagulation and precipitation treatment.
More clear water was obtained. The filtered water of the supernatant water has a pH of 7.0
Element 9.2 mg / l, electric conductivity 13000 μs / cm
there were. This filtered water was used in the same manner as in Example 1, namely H-type positive
Same conditions for ion exchange resin tower and OH type anion exchange tower
I passed water. Changes in the electrical conductivity of the resulting treated water over time
It shows in Table 2.

[0036]

[Table 2]

From Table 2, it is understood that according to the method of the present invention, highly pure water can be stably recovered from the fluorine-containing water at a high recovery rate for a long period of time.

On the other hand, in Comparative Example 2 in which the fluorine removal treatment with CaCO ₃ is not performed, desalting by ion exchange is almost impossible.

[0039]

As described above in detail, according to the method for recovering water from fluorine-containing water of the present invention, the fluorine-containing water discharged from a semiconductor factory or the like can be manufactured at low cost, easily and with high recovery rate. Water with high purity can be recovered. Therefore, it is possible to effectively collect and reuse the water that has been conventionally discarded as wastewater, and to effectively use the water resource.

[Brief description of drawings]

FIG. 1 is a system diagram showing a method of one embodiment of a method for recovering water from fluorine-containing water according to the present invention.

[Explanation of symbols]

1 CaCO ₃ packed tower 2 H type cation exchange resin packed tower 3 Decarbonation tower 4 OH type anion exchange resin packed tower

Continuation of the front page (56) Reference JP-A-57-15885 (JP, A) JP-A-56-150482 (JP, A) JP-A-50-10798 (JP, A) JP-A-60-206485 (JP , A) JP 60-48191 (JP, A) JP 50-127872 (JP, A) JP 54-7762 (JP, A) JP 1-304096 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C02F 1/58

Claims (3)

(57) [Claims] 1. Fluorine-containing water in a calcium carbonate packed tower
A method for recovering water from flowing fluorine-containing water , wherein the calcium carbonate in the packed tower flows through the fluorine-containing water.
Fluorine is converted to calcium fluoride by flowing water upward at a speed
After fixing , generated in the packed tower due to the water flow
Water recovery method of a fluorine-containing water, characterized in that the decarboxylation process carbonate ions, and a desalting treatment is performed. 2. Fluorine-containing water in a calcium carbonate packed tower
A method for recovering water from flowing fluorine-containing water , wherein the calcium carbonate in the packed tower flows through the fluorine-containing water.
Fluorine is converted to calcium fluoride by flowing water upward at a speed
After fixing , pass through the cation exchange resin packed tower and the water flow.
Water recovery method of a fluorine-containing water, characterized in that the water flow in the order of the <br/> decarbonation tower to remove carbonate ions generated in a packed column, and the anion exchange resin packed column Te. 3. Fluorine-containing water to a calcium carbonate packed tower
By passing water, the calcium in the effluent of the packed tower
The ion concentration does not increase, or
2. A method for recovering water from fluorine-containing water according to 2.