TWI438154B - Method for treating hydrofluoric acid wastewater - Google Patents

Description

Hydrofluoric acid drainage treatment method Field of invention

The present invention relates to a method for treating hydrofluoric acid drainage containing hydrazine and fluorine.

Background of the invention

The treatment method for recycling hydrofluoric acid produced in the manufacturing steps of electronic components such as semiconductors or liquid crystals has been reviewed since the beginning. For example, Patent Document 1 discloses a method in which the pH is adjusted to 6 or more by adding a base to the drainage of fluorine and antimony to precipitate a niobate, and then the niobate is solidified by a filter press or the like. The liquid is separated, and water-soluble calcium is added to the separation liquid, whereby the method of recovering fluorine by the form of calcium fluoride is obtained.

In the wastewater treatment method disclosed in Patent Document 1, since the alkali is added to remove the citric acid contained in the wastewater and the solid-liquid separation is performed, the fluorine contained in the separation liquid is NaF, NH ₄ F, KF. An alkali metal salt is present. In this way, the separation liquid cannot be directly reused as hydrofluoric acid for etching or washing, and therefore it is necessary to recover fluorine after recovering fluorine by calcium fluoride by the addition of water-soluble calcium. The raw materials are used to form hydrofluoric acid, and the steps for recycling are not only cumbersome but also consume a lot of energy.

Further, Patent Document 2 discloses a method for recovering hydrofluoric acid by heating a waste liquid of hydrofluoric acid containing cerium oxide and a metal component in an evaporation pot to form a crude hydrofluoric acid vapor, and in the crude hydrofluoric acid evaporation step. A method of suppressing precipitation of a metal component by adding sulfuric acid to a hydrofluoric acid waste liquid to dissolve a metal component to prevent fouling in the evaporation pot.

The problem of the hydrofluoric acid recovery method disclosed in the above Patent Document 2 is that a large amount of crude hydrofluoric acid vapor is likely to be mixed in the hydrofluoric acid waste liquid, and thus the condensed water is still difficult to reuse as hydrofluoric acid.

Advanced technical literature [Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-207797

Patent Document 2: Japanese Patent No. 4635527

Summary of invention

Accordingly, an object of the present invention is to provide a method for treating hydrofluoric acid drainage which is capable of efficiently removing hydrazine contained in a hydrofluoric acid drainage and easily recovering hydrofluoric acid which can be reused.

The foregoing object of the present invention can be attained by a method for treating hydrofluoric acid drainage, which is for treating a hydrofluoric acid drainer containing bismuth and fluorine, which comprises a membrane separation step for the hydrofluoric acid The drainage is passed through a membrane separation device at a pH of less than 6, and separated into a hydrofluoric acid aqueous solution penetrating water and a non-penetrating water concentrated by the hydrazine industry.

In the method for treating hydrofluoric acid drainage, the membrane separation step is preferably carried out by passing the membrane separation device without adding an alkali component (particularly a calcium component) to the hydrofluoric acid. The membrane separation apparatus preferably performs membrane separation using an NF membrane or membrane separation using an RO membrane.

Further, it is further provided with an evaporation step in addition to the above membrane separation step. Preferably, the evaporation step heats the aforementioned penetrating water to form a hydrofluoric acid-containing vapor.

According to the present invention, a method for treating hydrofluoric acid drainage can be provided, which can efficiently remove hydrazine contained in hydrofluoric acid drainage, and can easily recover hydrofluoric acid which can be reused.

Simple illustration

Fig. 1 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage according to an embodiment of the present invention.

Fig. 2 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage in another embodiment of the present invention.

Fig. 3 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage in still another embodiment of the present invention.

Form for implementing the invention

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage according to an embodiment of the present invention. The hydrofluoric acid drainage treatment apparatus shown in Fig. 1 is configured such that the raw liquid tank 10 and the membrane separation device 20 are connected by a pipe 11, and the hydrofluoric acid drainage stored in the raw liquid tank 10 is supplied to the membrane separation device. 20 was subjected to membrane separation. The membrane separation device 20 is formed with a primary chamber 23 and a secondary chamber 24 separated by a separation membrane 22 inside the casing 21. The hydrofluoric acid drainage supplied from the raw liquid tank 10 to the primary chamber 23 of the membrane separation device 20 by the operation of a pump (not shown) is separated into two through the separation membrane 22 The water passing through the chamber 24 and the non-penetrating water that cannot pass through the separation membrane 22 are discharged through the pipes 25 and 26, respectively. In the separation membrane 22, it is preferable to effectively remove the ruthenium contained in the hydrofluoric acid drainage in a dissolved state, and specifically, an RO membrane (Reverse Osmosis Membrane) or an NF membrane (Nanofiltration Membrane) can be used. A part of the non-penetrating water discharged from the primary chamber 23 can be passed through the reflux pipe 27 to merge with the hydrofluoric acid drainage flowing through the pipe 11.

In the method for treating hydrofluoric acid drainage according to the embodiment of the present invention, the hydrofluoric acid-containing hydrofluoric acid-containing wastewater generated in the manufacturing step of an electronic component such as a semiconductor or a liquid crystal is pressurized and supplied from the raw solution tank 10 to the film. The separation device 20 is performed. The hydrofluoric acid drainage of the separation membrane 22 is maintained at a pH lower than 6 without adding an alkali component, and the ruthenium component contained therein is mostly dissolved and exists in an ionic state, and does not pass through the membrane due to the large molecular weight of the ion. . Therefore, in the primary chamber 23 of the membrane separation device 20, most of the crucible does not pass through the separation membrane 22 but is concentrated and discharged without passing through the water. On the other hand, the fluorine contained in the hydrofluoric acid drainage is in the form of an aqueous solution of hydrofluoric acid and the Teflon passes through the separation membrane 22, so that the reduced hydrofluoric acid is discharged from the secondary chamber 24 of the membrane separation device 20. . In order to increase the concentration ratio of the ruthenium and to reduce the amount of non-penetrating water, it is preferable to reflux a part of the non-penetrating water by the reflux pipe 27, and by adjusting the opening degree of the valve 28, the recovery rate of the penetrating water can be controlled. .

As described above, in the method for treating hydrofluoric acid drainage according to the present embodiment, the hydrazine can be removed without adding an alkali component such as calcium to the hydrofluoric acid drainage, so that the permeated water can be directly reused as a high-purity hydrofluoric acid aqueous solution. Therefore, it is not necessary to carry out the step of producing fluorine from the obtained calcium fluoride as in the conventional technique of adding calcium component to hydrofluoric acid drainage to recover calcium fluoride, and the recovery efficiency can be improved. Again, this In the invention, the alkali component such as calcium is not added as described above, in order to maintain the pH value of the hydrofluoric acid drainage below 6, so that the hydrofluoric acid which has passed through the separation membrane 22 can be directly reused, even if hydrofluoric acid is drained. It is also possible to have a trace amount of alkali component which can achieve the purpose.

When the pH of the hydrofluoric acid drainage water passing through the separation membrane 22 is increased to 6 or more, for example, when an alkali component is present, fluorine is reduced to a fluoride salt (for example, NaF or the like), and the fluorine ion which passes therethrough is lowered. The pass rate of hydrofluoric acid in 22 will decrease. Therefore, the hydrofluoric acid drainage must pass through the separation membrane 22 in a state where the pH is lower than 6. Since the pH value is more than 5.5, the fluoride ion passage rate can be further improved, and it is more preferably 5 or less. The lower limit of the pH of the hydrofluoric acid drainage is not particularly limited, and is, for example, 2 or more.

The separation membrane 22 may be either an RO membrane or an NF membrane. From the viewpoint of further increasing the passage rate of the hydrofluoric acid aqueous solution, it is preferable to suitably use the NF membrane, and on the other hand, from the viewpoint of further increasing the ruthenium removal rate. It is better to use RO membrane properly.

The method for treating hydrofluoric acid drainage of the present invention can also be carried out by using the apparatus shown in Fig. 2. The hydrofluoric acid drainage treatment apparatus shown in Fig. 2 is further provided with an evaporation device 30 and a condenser 40 in addition to the raw liquid tank 10 and the membrane separation device 20 shown in Fig. 1, and the evaporation device 30 is used. The hydrofluoric acid-containing vapor is generated by heating and evaporating the hydrofluoric acid aqueous solution that has passed through the membrane separation device 20, and the condenser 40 cools the generated hydrofluoric acid-containing vapor to be condensed. The configuration of the evaporation device 30 is not particularly limited. For example, a known instantaneous evaporation concentration device can be used, that is, a hydrofluoric acid aqueous solution is heated by a heater to be supersaturated, and then dispersed and evaporated in an evaporation can under reduced pressure. By. The hydrofluoric acid-containing vapor generated in the evaporation device 30 is introduced into the condenser 40 through the pipe 31 to be condensed water, and is recovered from the pipe 32. On the other hand, the concentrated water concentrated by the evaporation device 30 is discharged from the pipe 33.

With the hydrofluoric acid drainage treatment device shown in FIG. 2, the hydrofluoric acid drainage containing ruthenium and fluorine is separated by the membrane separation device 20 into a penetrating water and a non-penetrating water, and the permeated water is evaporated. Device 30 produces a hydrofluoric acid containing vapor that is recovered. On the other hand, most of the ruthenium contained in the hydrofluoric acid drainage is removed by the membrane separation device 20, and the evaporation device 30 can be further reduced together with other impurities to obtain a hydrofluoric acid aqueous solution of higher purity.

An example of the mass balance of the treatment apparatus for hydrofluoric acid drainage shown in Fig. 2 is as follows. A hydrofluoric acid-containing wastewater containing 47 mg/kg and about 1% of hydrofluoric acid (HF) is 15092 kg/day, and is supplied from the raw liquid tank 10 to the membrane separation device 20 to obtain cerium (Si). And hydrofluoric acid (HF) is 10 mg/kg each, and about 1% of penetrating water is 12,074 kg/day. That is, about 80% of the hydrofluoric acid drainage can be recovered by the hydrofluoric acid aqueous solution, and the hydrofluoric acid concentration of the hydrofluoric acid aqueous solution is about 1 wt% of the hydrofluoric acid concentration of the hydrofluoric acid drainage, and the relative Here, by reducing the hydrazine concentration from 47 mg/kg to 10 mg/kg, the enthalpy of mixing with the hydrofluoric acid aqueous solution can be sufficiently reduced.

Further, the penetrating water contains cerium (Si) and hydrofluoric acid (HF) of 121 g/day and 120 kg/day, respectively, and is supplied to the evaporation device 30 and the condenser 40 to obtain cerium (Si) and The hydrofluoric acid (HF) was 57 g/day and the condensed water of 108 kg/day was 11,940 kg/day. That is, it is possible to recover a certain amount of condensed water with the penetrating water, and about 90% of the hydrofluoric acid (HF) can be recovered. Although the concentration of hydrofluoric acid in the recovered condensed water is 0.91% by weight, it can reduce other impurities while making the concentration of cesium. It was further reduced from 10 mg/kg to 5 mg/kg, and a high-purity hydrofluoric acid aqueous solution was recovered.

The hydrofluoric acid drainage treatment apparatus shown in FIG. 2 is configured to introduce hydrofluoric acid drainage into the evaporation apparatus 30 after the membrane separation apparatus 20 performs membrane separation, thereby recovering a high-purity hydrofluoric acid aqueous solution. After the hydrofluoric acid drainage is first introduced into the evaporation device 30 to generate hydrofluoric acid-containing vapor, the condensed water is subjected to membrane separation by the membrane separation device 20.

The method for treating hydrofluoric acid drainage of the present invention can also be carried out by using the apparatus shown in Fig. 3. The hydrofluoric acid drainage treatment apparatus shown in Fig. 3 is further provided with an additional tank 50 and additional evaporation in addition to the raw liquid tank 10, the membrane separation device 20, the evaporation device 30, and the condenser 40 shown in Fig. 2 . In the device 60, the additional tank 50 is for storing the primary concentrated water discharged from the evaporation device 30 via the pipe 33 and the non-penetrating water discharged from the membrane separation device 20 via the pipe 26, and the additional evaporation device 60 The mixed water supplied from the additional tank 50 by the piping 51 is heated and evaporated. In the third embodiment, the same components as those in the second embodiment are denoted by the same reference numerals.

The vapor generated in the additional evaporation device 60 contains a small amount of hydrofluoric acid that has not passed through the membrane separation device 20 and a small amount of hydrofluoric acid that has not been evaporated by the evaporation device 30, so that the vapor can be returned to the raw liquid tank 10 through the pipe 61. Increase the recovery rate of hydrofluoric acid. On the other hand, the secondary concentrated water which has been concentrated by the additional evaporation device 60 is discharged from the pipe 62.

10‧‧‧ raw liquid tank

11‧‧‧Pipe

20‧‧‧ membrane separation device

21‧‧‧ housing

22‧‧‧Separation membrane

23‧‧‧First room

24‧‧‧Second room

25,26‧‧‧Pipe

27‧‧‧Reflow piping

28‧‧‧Valves

30‧‧‧Evaporation unit

31,32,33‧‧‧Pipe

40‧‧‧Condenser

50‧‧‧Additional slot

51‧‧‧Pipe

60‧‧‧Additional evaporation unit

61,62‧‧‧Pipe

Fig. 1 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage according to an embodiment of the present invention.

Fig. 2 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage in another embodiment of the present invention.

Fig. 3 is a schematic configuration diagram of an apparatus for treating a hydrofluoric acid drainage in still another embodiment of the present invention.

10‧‧‧ raw liquid tank

11‧‧‧Pipe

20‧‧‧ membrane separation device

21‧‧‧ housing

22‧‧‧Separation membrane

23‧‧‧First room

24‧‧‧Second room

25,26‧‧‧Pipe

27‧‧‧Reflow piping

28‧‧‧Valves

Claims (5)

A method for treating hydrofluoric acid drainage, which is used for treating a hydrofluoric acid drainer containing bismuth and fluorine, comprising: a membrane separation step of passing the hydrofluoric acid drainage through a membrane separation device at a pH of less than 6 And separated into a hydrofluoric acid aqueous solution penetrating water and condensed non-penetrating water. The method for treating hydrofluoric acid drainage according to claim 1, wherein the membrane separation step passes through the membrane separation device without adding an alkali component to the hydrofluoric acid drainage. The method for treating hydrofluoric acid drainage according to the first aspect of the patent application further comprises an evaporation step of heating and evaporating the permeated water to form a hydrofluoric acid-containing vapor. The method for treating hydrofluoric acid drainage according to claim 1, wherein the membrane separation device uses an NF membrane for membrane separation. The method for treating hydrofluoric acid drainage according to claim 1, wherein the membrane separation device uses an RO membrane for membrane separation.