TWI637915B - Fluorinated wastewater treatment system - Google Patents

Abstract

The invention is a fluorine-containing wastewater treatment system, which comprises a direct current power supply unit, a water introduction unit to be treated, a reaction unit, an anode unit, a cathode unit, and a pH control unit. The anode unit and the cathode unit are both located in the reaction unit. When the DC power supply unit supplies power, the anode unit is placed in a porous metal container for waste aluminum chips. The fluoride ions in the water react to produce cryolite crystals and precipitate on the bottom of the reaction unit. Therefore, in this case, the scrap aluminum scrap is achieved. When the anode unit can be used as a waste, the porous metal container can effectively fix the scrap aluminum scrap, and the Al / F mole ratio, pH value and Na / F mole ratio can be controlled to a specific range to achieve good results. Its defluorination effect and other advantages.

Description

Fluorinated wastewater treatment system

The invention is a fluorine-containing wastewater treatment system, in particular a system for treating fluorine-containing wastewater to generate cryolite crystals. Among them, the present invention achieves a waste aluminum scrap when the anode unit can be used for waste, and the porous metal container can effectively fix the waste aluminum scrap, and can control the Al / F mole ratio, pH and Na / F mole ratio to a specific range. Good defluorination effect.

In the semiconductor industry, panel industry, and solar industry, hydrofluoric acid (HF) with a concentration of more than 49% is usually used for etching or cleaning. Depending on the needs of different processes, hydrofluoric acid is often mixed with other acids, such as phosphoric acid, nitric acid and sulfuric acid. In Taiwan, high-concentration fluorine-containing wastewater is mainly recovered through the synthesis of synthetic fluorite or sodium fluorosilicate.

For low-concentration fluorine-containing wastewater, the fluorine-containing concentration is at least 0.5%, and the removal of fluoride ions is mainly a chemical precipitation method by adding different calcium salts through calcium fluoride (fluorite, CaF ₂ ). To produce extremely fine particles (0.1 micron), coagulants or flocculants are used to achieve this. As a result, a large amount of sludge is produced, but the fluorine content is extremely low, which makes the reuse or treatment of this sludge more difficult. In addition, because fluorine is corrosive to the kiln, the ratio of sludge that can be added is controlled to less than 3%.

In 2014 and 2015, the amount of calcium fluoride sludge used in Taiwan in the cement industry was 27,802 tons and 27,991 tons. However, for increasingly stringent environmental regulations and the decline in Taiwan's cement output, it is necessary to develop new technologies to address low-concentration fluorine-containing wastewater and treatment of fluorine-containing wastewater.

Regarding the "fluorine-containing wastewater treatment method" of the Republic of China Invention Publication No. TW-201619063 (the Republic of China Invention Patent No. TW-I588097), a fluorine-containing wastewater treatment method has been disclosed. This method includes the following steps: First, perform the water inlet step to Mix well. Then, the fluoride ion detection unit is used to control the fluoride ion concentration of the water to be treated in the mixing tank. Then, the water to be treated and the aluminum salt solution are introduced into a fluidized bed crystallization tank and mixed to obtain a cryolite (Cryolite, Na ₃ AlF ₆ ) crystal. Among them, due to the need to introduce an aluminum salt solution, higher costs are required, and scrap aluminum scraps are not used.

In view of this, it is necessary to develop technologies that can solve the above-mentioned conventional disadvantages.

The invention is a fluorine-containing waste water treatment system, which can achieve the following effects: waste aluminum scraps can be used as anode units for waste, porous metal containers can effectively fix waste aluminum scraps, and can control Al / F molar ratio and pH value Compared with Na / F Molar to a specific range to achieve a good defluoridation effect. In order to solve the problem that the conventional need to introduce an aluminum salt solution requires a higher cost.

Therefore, the present invention is to provide a fluorine-containing wastewater treatment system, which includes: a direct current power supply unit having a positive power supply unit and a negative power supply unit for supplying a direct current of a predetermined voltage; and introduction of water to be treated A unit for supplying a water to be treated; the water to be treated is a fluorine-containing wastewater; a reaction unit having a containing space for containing the water to be treated; an anode unit being provided in the containing space The anode unit is provided with a porous metal container and a waste aluminum chip, the porous metal container has a plurality of through-holes, and the waste aluminum chip can be accommodated therein; the anode unit is connected to the through a first wire A positive power supply unit; a cathode unit disposed in the accommodating space and spaced from the anode unit; the cathode unit includes at least one cathode metal plate connected to the negative power supply unit through a second wire; and A pH control unit is used to adjust and prepare the pH value of the water to be treated in the reaction unit; thereby, the waste aluminum scraps are placed in the porous metal container to form an anode, and the The treated water provides aluminum ions, and reacts with fluoride ions in the water to be treated to generate cryolite crystals, which are precipitated on the bottom of the reaction unit.

The above-mentioned objects and advantages of the present invention can be easily understood from the detailed description and accompanying drawings of selected embodiments below.

The following examples and drawings are used to explain the present invention in detail:

10‧‧‧DC Power Supply Unit

11‧‧‧Positive electricity supply department

12‧‧‧Negative power supply department

13‧‧‧Multimeter

20‧‧‧Untreated water introduction unit

21‧‧‧Control slot

22‧‧‧ inlet tube

23‧‧‧Export tube

24‧‧‧Pressurized pump

25‧‧‧ return tube

30‧‧‧ reaction unit

31‧‧‧accommodation space

40‧‧‧Anode unit

41‧‧‧ porous metal container

42‧‧‧Scrap aluminum scraps

43‧‧‧first lead

50‧‧‧ cathode unit

51‧‧‧ cathode metal plate

52‧‧‧Second Lead

60‧‧‧pH control unit

70‧‧‧Fluoride detection unit

80‧‧‧Disturbance generating unit

Figure 1 is a perspective view of the fluorine-containing wastewater treatment system of the present invention

Figure 2 is a schematic diagram of the system architecture of the fluorine-containing wastewater treatment system of the present invention

Figure 3 is a schematic diagram of the correspondence between the Al / F mole ratio and the removal efficiency of fluorine at different pH values of the present invention

Figure 4 is a schematic diagram of the experimental results of the present invention at a pH value of 5.0

Figure 5 is a schematic diagram of the experimental results of the present invention at a pH of 5.5

Figure 6 is a schematic diagram of the experimental results of the present invention at a pH value of 6.0

Figure 7 is a schematic diagram of the experimental results of the present invention at a pH of 6.5

FIG. 8 is a schematic diagram of actual photography of the main structure of the present invention

FIG. 9 is a schematic diagram of actual photography of waste aluminum scraps of the present invention.

Please refer to FIGS. 1, 2 and 8. The present invention is a fluorine-containing wastewater treatment system, which mainly includes: a DC power supply unit 10, a water introduction unit 20 to be treated, a reaction unit 30, and an anode unit 40. A cathode unit 50 and a pH control unit 60.

Regarding the DC power supply unit 10, it has a positive power supply unit 11 and a negative power supply unit 12 for supplying a DC voltage of a predetermined voltage; of course, a multimeter 13 (Multimeter) can also be included to measure the State of current and voltage.

The water to be treated introduction unit 20 is used to supply a water to be treated; the water to be treated is fluorine-containing wastewater.

Of course, the water to be treated can also refer to the method in the "fluorine-containing wastewater treatment method" of the Republic of China Invention Patent Publication No. TW-201619063 (the Republic of China Invention Patent No. TW-I588097), and introduce high-concentration fluorine-containing wastewater and low-concentration in advance The fluorine-containing wastewater is then controlled and adjusted to a predetermined fluoride ion concentration. This mixing technology is a published technology and will not be described in detail here.

The reaction unit 30 has a receiving space 31 for receiving the water to be treated.

Regarding the anode unit 40, it is provided in the accommodating space 31. The anode unit 40 has a porous metal container 41 (for example, a grid-shaped cylinder or a porous hole basket of other shapes) and a waste. Aluminum shavings 42 (see FIG. 9, for example, scrap aluminum shavings after cutting); the porous metal container 41 has a plurality of through-holes (for liquid circulation), and is used to accommodate the cutting-shaped waste aluminum shavings 42; The anode unit 40 is connected to the positive power supply unit 11 through a first wire 43.

In particular, the waste aluminum scraps 42 in the first figure are in a state before being put in for easy understanding. In actual use, they are placed in the porous metal container 419 and completely immersed in the water to be treated. .

The cathode unit 50 is disposed in the accommodation space 31 and is spaced from the anode unit 40. The cathode unit 50 includes at least one cathode metal plate 51 (for example, two or more stainless steel plates, and The anode units 40 are separated by 1 cm or other distances), and are connected to the negative power supply unit 12 through a second wire 52.

The pH control unit 60 is used to adjust and control the pH value of the water to be treated in the reaction unit 30. For example, a product of model PC3200 manufactured by Suntex Instruments Co., Ltd. made in Taiwan is used.

Accordingly, the scrap aluminum scrap 42 is placed in the porous metal container 41 to constitute an anode, and aluminum ions are provided to the water to be treated, which reacts with fluorine ions in the water to be treated to generate cryolite crystals (not shown in the figure) (Shown in conjunction with Chen Ming) and precipitated at the bottom of the reaction unit 30.

Therefore, the present invention achieves the purpose of removing the fluoride ions in the water to be treated by using the unique manner in which the aluminum scrap 42 is placed in the porous metal container 41.

Of course, the present invention can further add a fluoride ion detection unit 70, which is disposed in the reaction unit 30, and is used to detect the fluorine ion concentration of the water to be treated in the reaction unit 30.

In practice, the to-be-treated water introduction unit 20 may be a return pipe, which has a control tank 21, an introduction pipe 22, an outlet pipe 23, a pressurized pump 24, and a return pipe 25. The introduction pipe 22 is connected to the control tank 21 and the reaction unit 30 to introduce the water to be treated into the reaction unit 30, and the outlet pipe 23 is connected to the reaction unit 30 and the control tank 21 to use the The treated water is led out of the reaction unit 30. The pressurized pump 24 is connected between the lead-out pipe 23 and the control tank 21 to pressurize the treated water. The return pipe 25 is provided in the pressurized pump. Between 24 and the control tank 21, the water to be treated is introduced into the control tank 21 to form a reflux cycle.

The pH control unit 60 is disposed in the control tank 21, and can further control the pH value of the water to be treated introduced from the control tank 21.

In addition, a disturbance generating unit 80 may be further added, such as Stirring Hot Plates manufactured by Massachusetts, USA (Cemarec ^TM ), which is placed under the reaction unit 30, so that the reaction unit 30 The to-be-treated water generates a disturbance, which makes the reaction better.

Nano-ions are also added to the water to be treated, and they are controlled under the following conditions:

[a] The pH value of the water to be treated is controlled at 5.0-6.5, and the Al / F mole ratio is 0.8 / 6 ~ 1.2 / 6.

[b] The pH value of the water to be treated is controlled at 6.0 ~ 6.5 and the Al / F mole ratio is 1/6 ~ 3/6, while the Na / F mole ratio is 4/6 ~ 12/6.

For the experimental data of the present invention, please refer to FIG. 3, which is the removal efficiency of this fluorine when the pH value is fixed at 5, 5.5 and 6.0. Among them, the horizontal axis of Figure 3 is the Al / F mole ratio, the unit is X / 6; where Al is calculated according to Faraday's law. The vertical axis is Fluoride Removal Efficiency (unit:%).

When the Al / F molar ratio is 1/6, the removal rate of this fluorine reaches the maximum value regardless of the pH value.

When the Al / F molar ratio is greater than 1/6, and the pH value is controlled at 6, the removal rate of fluorine remains stable, as high as 90 to 100%, which is an ideal result.

When the Al / F molar ratio is greater than 1/6 and the pH is controlled at 5.5, the removal rate of fluorine remains stable after a slight decrease, and both are above 90%, which is also good.

When the Al / F molar ratio is greater than 1/6 and the pH is controlled at 5.0, the removal rate of fluorine gradually decreases.

Therefore, regardless of the pH value, if the Al / F molar ratio is between 0.8 / 6 and 1.2 / 6, there should be a good fluorine removal rate.

Refer to Figures 4, 5, 6, and 7 for the fixed conditions of F- = 0.15 mol, but when the pH is controlled at 5.0, 5.5, 6.0, and 6.5, the Na / F molar ratio is And the relationship between Al / F mole ratio and cryolite production rate.

It can be seen from Figure 4 that when the pH value is controlled at 5.0, mainly when the Al / F molar ratio is about 1/6, the cryolite generation rate can reach more than 90%.

It can be seen from Fig. 5 that when the pH value is controlled at 5.5, mainly when the Al / F molar ratio is about 1/6, the cryolite production rate can reach more than 90%. In addition, when the Al / F molar ratio is greater than 1/6, if the Na / F molar ratio is close to 11/6 ~ 12/6, the cryolite generation rate may be about 70%.

It can be seen from Fig. 6 that when the pH value is controlled at 6.0, mainly when the Al / F molar ratio is about 1/6, the cryolite generation rate can reach more than 90%. In addition, when the Al / F molar ratio is greater than 1/6, if the Na / F molar ratio is 4/6 ~ 12/6, the cryolite production rate can be maintained above 70%.

As can be seen from Fig. 7, when the pH value is controlled at 6.5, mainly when the Al / F molar ratio is around 1/6, the cryolite production rate can reach more than 90%. In addition, when the Al / F molar ratio is greater than 1/6, if the Na / F molar ratio is 4/6 ~ 12/6, the cryolite production rate can be maintained above 70%.

That is, it can be concluded that:

[a] When the Al / F molar ratio is around 1/6, when the pH value is controlled at 5.0-6.5, the cryolite production rate can reach more than 90%. The Al / F mole ratio can be defined as a range of 0.8 / 6 to 1.2 / 6 around 1/6.

[b] When the pH is controlled at 6.0 ~ 6.5 and the Al / F molar ratio is greater than 1/6, if the Na / F molar ratio is 4/6 ~ 12/6, the cryolite production rate can be maintained at 70% The above can also reach a practical level.

The advantages and effects of this case can be summarized as:

[1] Waste aluminum scrap can be used as anode unit. The traditional method of aluminum ion source is aluminum salt solution, and this case cleverly uses waste aluminum chips (connected to the positive electrode of the power supply) as the aluminum ion source, which not only saves the cost of aluminum salt solution, but also achieves the purpose of waste utilization, which is quite environmentally friendly. Therefore, the waste aluminum scrap can be used as the anode unit.

[2] Porous metal container can effectively fix waste aluminum scraps. The porous metal container in this case is like a container, which limits the movement range of these scrap aluminum scraps. It is very convenient to operate when the scrap aluminum scraps are to be taken out for observation or to be replenished. Therefore, the porous metal container can effectively fix aluminum scrap.

[3] Al / F molar ratio, pH value and Na / F molar ratio can be controlled to a specific range to achieve a good defluoridation effect. The present invention has two methods. The second method is to control the Al / F mole ratio at about 1/6, and when the pH value is controlled at 5.0-6.5, the cryolite generation rate can reach more than 90%. The second method is: when the pH value is controlled at 6.0 ~ 6.5 and the Al / F mole ratio is greater than 1/6, if the Na / F mole ratio is 4/6 ~ 12/6, the cryolite production rate can be maintained Above 70%, it can reach a practical level, which can be used for defluorination in related industries. Therefore, the Al / F mole ratio, pH value and Na / F mole ratio can be controlled to a specific range to achieve a good defluorination effect.

The above is only a detailed description of the present invention through a preferred embodiment, and any simple modifications and changes made to the embodiment will not depart from the spirit and scope of the present invention.

Claims (6)

A fluorine-containing wastewater treatment system includes: a direct current power supply unit having a positive power supply unit and a negative power supply unit for supplying a direct current of a predetermined voltage; and a to-be-treated water introduction unit for supplying power A water to be treated; the water to be treated is fluorine-containing wastewater; a reaction unit having a receiving space for containing the water to be treated; an anode unit provided in the receiving space; the anode unit having A porous metal container and a waste aluminum chip, the porous metal container having a plurality of through-holes, and the waste aluminum chip can be accommodated therein; the anode unit is connected to the positive power supply part through a first wire; a cathode A unit provided in the accommodation space and spaced from the anode unit; the cathode unit includes at least one cathode metal plate connected to the negative power supply unit through a second wire; and a pH control unit used for To adjust and supply the pH value of the water to be treated in the reaction unit; thereby, the waste aluminum scraps are placed in the porous metal container to form an anode, and aluminum ions are provided to the water to be treated, and The fluoride ions in the water to be treated react to produce cryolite crystals, which are precipitated on the bottom of the reaction unit. The fluorine-containing wastewater treatment system according to item 1 of the scope of the patent application, wherein nano-ions are added to the water to be treated and controlled under the following conditions: the pH of the water to be treated is controlled at 5.0-6.5, and Al / F The mole ratio is between 0.8 / 6 and 1.2 / 6. The fluorine-containing wastewater treatment system according to item 1 of the scope of the patent application, wherein nano-ions are added to the water to be treated and controlled under the following conditions: the pH value of the water to be treated is controlled between 6.0 and 6.5 and Al / F friction The ear ratio is between 1/6 ~ 3/6, and the Na / F molar ratio is between 4/6 ~ 12/6. The fluorine-containing wastewater treatment system according to item 1 of the scope of the patent application, further comprising: a fluorine ion detection unit, which is set in the reaction unit to detect fluorine in the water to be treated in the reaction unit Ion concentration. The fluorine-containing wastewater treatment system according to item 1 of the scope of the patent application, wherein the water introduction unit to be treated is a return line, which has a control tank, an introduction pipe, an outlet pipe, a pressurized pump and A return pipe; the introduction pipe system is connected to the control tank and the reaction unit to introduce the water to be treated into the reaction unit, and the outlet pipe system is connected to the reaction unit and the control tank to discharge the to-be-treated water In the reaction unit, the pressurizing pump is connected between the outlet pipe and the control tank to pressurize the water to be treated, and the return pipe is provided between the pressurizing pump and the control tank. In order to introduce the water to be treated into the control tank, a reflux cycle is formed. According to the fluorine-containing wastewater treatment system described in item 1 of the scope of the patent application, it further comprises: a disturbance generating unit, which is placed under the reaction unit to cause disturbance of the water to be treated in the reaction unit.