TWI328566B - Electro-coagulation water treatment reactor and process for treating waste water - Google Patents

Description

1328566 IX. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to an electrocoagulation reactor, and more particularly to a sensing electrode of the electrocoagulation reactor. [Prior Art] - The semiconductor industry generates a large amount of wastewater, especially chemical mechanical polishing (CMP). The CMP produces wastewater containing a large amount of nano-sized particles and auxiliaries, even including organic components containing carbon. In order to avoid environmental pollution and reuse of recycled wastewater, the current wastewater treatment process mainly includes chemical coagulation, membrane filtration, and electrocoagulation, and is combined with ion exchange resin or photocatalytic oxidation treatment to increase the effect. Chemical coagulation has been around for a long time and is the most common wastewater treatment method. The principle of chemical coagulation is to use a chemical reagent to change the surface potential of the suspended particles and to destroy the stability thereof, and then to form a flocculent agglomeration of particles in the water by coagulation, and then remove it by precipitation. However, the dosing amount of this method is not easy to control, the volume of the coagulation tank is large, and the water quality after treatment is poor, and has been gradually replaced by other wastewater treatment processes. Membrane filtration is carried out using a microfiltration membrane, an ultrafiltration membrane, or a ceramic filtration membrane. However, the problem of membrane filtration is that membrane fouling is likely to occur, the amount of waste water per unit time is too small (about 99 liters/hour* film area m2), and the dissolved organic oxide (TOC) and total organic carbon (TOC) cannot be removed. And the price is very expensive (NT$1-4 million per square meter film). The principle of electrocoagulation is to use the metal ions released from the electrodes to form the rubber plume of the hydrogen oxidized metal, and the rubber feathers will collect the particles in the wastewater. However, the current known electrocoagulation technology has a processing time of several hours, and the nanoparticle removal effect is 0956-A21950TWF (N2): P55950095TW: hsuhuche 5 1328566 total = film is poor, and it is impossible to simultaneously remove dissolved oxides and '^^1 organic carbon (TOC). In U.S. Patent No. 3,969,245, it is disclosed that after the electric coagulation and charging of the waste line rod electrode, bubbles are formed on the electrode and the floc is added to add a coagulant to produce a larger floc. (10) Kidney bean liquid. In U.S. Patent No. 5, No. 14, using film and electrocoagulation to remove contaminants in liquids, the electrodes of the long length are placed in an insulated electric coagulation tank, and the temperature, pressure and flow rate are 5 weeks. Coagulation. In U.S. Patent No. 5,587, G57, a conductive rod electrode is placed in a conductive tank and a direct current is passed to perform electric coagulation treatment. In U.S. Patent No. 6,139,710, a plate electrode is placed vertically in an electrocoagulation reaction tank. The pump is used for pressure control, and the electric current is controlled by a voltage and current to release the gas generated in the reaction. mud. In U.S. Patent No. 6,582,592, a dissolved metal for treating industrial waste water is disclosed. The waste water flows between parallel electrode plates, and the electrode is ionized. The filter is used to separate the sludge and clarified water, and the temperature and force are monitored. And acid test value. In U.S. Patent No. 6,613,217, the reactor is composed of longitudinally elongated electrodes and electrocoagulated to remove foam and gas from the product, and a small spacing between the electrodes can be adjusted under the reactor. In U.S. Patent No. 67,1989,4, the organic and metal contaminated liquid is treated by electrocoagulation technology, and the waste liquid is removed by coagulation after coagulation, minus 956-A21950TWF (N2); P55950095TW: hsuhuche 6 1328566 produces a clear liquid after pressing . In U.S. Patent No. 6,797,179, the industrial wastewater containing f is treated by electrocoagulation technology, and the electrode plate is passed through a direct current power source to make it electrically charged, and the waste water flows through the electrode plate for electrocoagulation reaction. At the same time control the temperature and acid test conditions. The above-mentioned electrocoagulation treatment device still cannot effectively solve the wastewater generated by the semiconductor process, especially the chemical mechanical polishing wastewater. Therefore, there is a need for new electric mixing/rotating devices and corresponding wastewater treatment methods. • The present invention provides an electro-coagulation reactor comprising an anode and a cathode; a plurality of conducting electrodes respectively connected to the anode and the cathode; a plurality of aluminum sensing electrodes located between the conducting electrodes; and a plurality of irons A sensing electrode is located between the conductive electrodes. The invention also provides a method for treating wastewater, comprising introducing waste water into the above-mentioned electric/rotation reaction state, introducing a direct current power source, and generating an induced current between the sensing electrode and the iron sensing electrode between the conducting electrodes to generate iron ions and |g. After the ions form a rubber feather, the suspended particles of the rubber feather and the wastewater are aggregated; and the suspended particles of the rubber feather and the waste water are removed. [Embodiment] In Fig. 1, a schematic view of an electrocoagulation reactor 1 of a preferred embodiment of the present invention is shown. The power supply 10 is divided into an anode 1 ο A and a cathode i 0B. The anode 10A is connected to the lead electrode 11A, and the cathode is connected to the lead electrode iiB. The material of the lead electrodes 11A and 11B may be made of aluminum, iron, steel, or stainless steel. Between the lead electrodes 11A and 11B, a plurality of surface sensing electrodes 13a and iron 0956-A21950TWF(N2) are interposed; P55950〇95TW: hsuhuche 7 1328566

The sensing electrode 13B preferably has a distance between the two sensing electrodes and the conductive electrode of 0.1 cm to 1 cm. The material of the iron sensing electrode 13B includes iron, steel, or stainless steel. In Fig. 1, the electrocoagulation reactor divides the tank into 5 blocks with 6 conductive electrodes, and the block with 16 sensing electrodes in each block is all the sensing electrodes 13A' and the other The block is the iron sensing electrode 13B. However, it is understood that the number of blocks, the number of the aluminum sensing electrodes 13A and the iron sensing electrodes 13B, and the manner in which the sensing electrodes are disposed may be adjusted as appropriate. For example, more than one block may be the aluminum sensing electrode 13A. In other embodiments, the aluminum sensing electrodes and the iron sensing electrodes may be staggered (as in Figure 2), rather than the same sensing electrodes as shown in Figure 1 being disposed in the same block. In other embodiments, the shapes of the conductive electrodes 11A, 11B, the sensing electrodes 13A, and the iron sensing electrodes 13B may be other shapes such as a columnar shape or a tubular shape in addition to a plate shape. After the wastewater is introduced into the electrocoagulation reactor 1, the power supply supplies direct current to the lead electrodes 11A and 11B. Inductively, an electric field is generated between the aluminum sensing electrode 13A and the iron sensing electrode 13B between the conductive electrodes 11A and 11B, and the electrode is oxidized to form iron ions and aluminum ions, thereby generating a rubber plume of aluminum hydroxide and aluminum hydroxide with water. The rubber feathers will be aggregated with the suspended particles in the wastewater into larger size particles, which are easier to remove by sedimentation or filtration. In an electric coagulator, the reaction of the anode is as follows:

Fe(s)Fe2+(aq) + 2e' (Formula 1)

Fe2+(aci) FeJ+(aq) + e·(Formula 2) 4Fe2+(aq) + 10H2O(1) + 02(g)— 4Fe(OH)3 (s) + 8H+ (Formula 3) A1(S) A1J (aq) + 3e (Formula 4) 0956-A21950TWF(N2): P55950095TW: hsuhuche 8 1328566

Al3+(aq) + 3H20(1)-A1(0H)3 (4) +3H+(Formula 5) The reaction formula of the cathode is as follows: 2H (aq) + 2e -» H2(g) (Formula 6) In addition to directly introducing wastewater into the present invention In addition to the electric coagulation reactor treatment, 'the oxidant can also be added to oxidize the organic matter in the wastewater before starting the electrocoagulation. The oxidizing agent may be oxygen, ozone, hydrogen peroxide, fluorine gas, chlorine or a combination thereof, and hydrogen peroxide is preferred in the preferred embodiment. The addition of an oxidant can effectively solve the problem of TOC and increase the oxidation efficiency of Fe2+. The reaction of the entire oxygenation reaction is as follows:

Fe2+(aq) + H202-Fe3+(aq) + 0H_ + ·0Η (Formula 7) •0Η+organic carbon—·product after degradation+C〇2+H2〇(i) (Equation 8)

Since the conductive electrode ΠΑ, 11B, the sensing electrode 3A, and the iron sensing electrode 13B are slowly passivated and consumed with the electrochemical reaction, it is necessary to carry out regeneration treatment even after a certain period of time, or even directly replace the electrode. In order to average the electrode loss, the DC power supply of the power supply of the present invention reverses the polarity after the interval, so that the electrical properties of the cathode and the anode are reversed. The preferred interval is between about 1-5 minutes and the direct current is between about 10-25 amps. The treated wastewater may first adjust the pH value, preferably the pH value is between 5 and 7, and then the precipitation, filtration, floatation, overflow or the combination of the above steps is used to remove the aggregation of the rubber feathers and suspended particles of the wastewater. For example, after the sedimentation tank is introduced to carry out the sedimentation of the rubber feather, the settled wastewater is then introduced into the overflow tank, and the upper water sample is taken for detection. The results show that the electro-coagulation reactor of the invention can greatly reduce the turbidity, the solubility enthalpy concentration, the TOC, and simultaneously change the nano-scale suspension into 0956-A21950TWF (N2); P55950095TW; hsuhuche 9 1328566 to 2300 nm or more. Shen Temple. Most importantly, in the preferred embodiment, the electrocoagulation reactor of the present invention can be continuously treated for 5 hours without regeneration treatment.

In other comparative embodiments of the invention, all of the sensing electrodes are in the sense electrodes. The disadvantage of this method is that the cost of the car is expensive and the regeneration loss is fast, which will greatly increase the material cost of wastewater treatment. In another comparative embodiment of the invention, all of the sensing electrodes are iron sensing electrodes. Although this method can reduce the material cost, the iron electrode needs to be disassembled and regenerated frequently, which will greatly increase the operation and time cost. The invention can prolong the regeneration time of the iron sensing electrode and reduce the loss rate of the aluminum sensing electrode. To make the skilled person more aware of the features of the present invention, the preferred embodiments are exemplified below. Example 1 After the grinding waste liquid was uniformly mixed in the ratio of oxide/metal ion (3/1), hydrogen peroxide (0.04%) was added to the tank and stirred uniformly. After the pump is introduced into the electric coagulation tank, direct current (7〇V / 25A) is applied, and the direct current is exchanged polarity every minute, and the flow rate of the waste water is 12 L/min. Then, the wastewater is introduced into the post-treatment tank to adjust the pH value, and then introduced into the sedimentation tank for sedimentation, and finally introduced into the overflow tank, and the upper water sample is taken for detection. As shown in Fig. 1, the electric kneading tank uses five iron electrodes as the guide electrodes, and divides the tank into four regions. One of the areas contained 16 aluminum electrode plates as the sensing electrodes, and the other three areas contained 16 iron electrode plates as the sensing electrodes. The plate spacing was 0.3 cm. The water quality analysis before and after the wastewater treatment of this example is shown in Table 1. 0956-A21950TWF(N2):P55950095TW:hsuhuche 1328566 Table 1 time water quality project stock solution 100 minutes 180 minutes 240 minutes 300 minutes acid value 8.9 5.78 5.52 5.50 5.64 turbidity (ntu) 236 3.58 2.65 3.01 2.89 conductivity ( Ms/cm) 333 562 436 440 415 Solubility 矽; il degree (nig/L) 151.2 22.3 45.4 35.7 48.9 Average particle size (nm) 159 6650 2360 7210 3120 Bound potential (mV) -42.7 -3.96 -6.4 -1.72 -20.3 Total Organic Carbon (ppb) 2781 425 431 747 687 Example 2

In the second embodiment, as shown in Fig. 2, the electric kneading tank has five ferroelectric electrodes as the conducting electrodes, and the tank body is divided into four regions. Two of the areas contain 8 I-electrode plates and 8 pieces of iron electrode plates as sensing electrodes. The other two areas contain 16 {iron electrode plates as sensing electrodes. The four regions are staggered and the plates are spaced 0.3 cm apart. The water quality analysis before and after wastewater treatment is shown in Table 2. Table 2 Time Water Quality Project Stock Solution 100 minutes 180 minutes 240 minutes 300 minutes Acid value 8.9 6.47 6.54 6.62 6.58 Turbidity (NTU) 236 11.5 21.8 32.2 33.5 Conductivity (ps/cm) 333 882 765 704 780 Solubility 矽Concentration (111§/1-) 151.2 28.8 24.7 20.1 25.1 Average particle size (nm) 159 8310 2300 1710 1540 0956-A21950TWF(N2); P55950095TV\/:hsuhuche 1328566 Jieda potential (mV) -42.7 -16.5 -34.7 - 36.6 -32.5 Total Organic Carbon (ppb) 2781 419 527 549 806 Comparative Example In this example, the 'electrical coagulation tank uses five iron electrodes as the conducting electrode, and the chamber is divided into four regions. 64 iron electrode plates were used as the sensing electrodes' Each of the regions had 16 iron electrode plates with a plate spacing of 0.3 cm. The water quality analysis before and after wastewater treatment is shown in Table 3. • Table three time water quality project stock solution 100 minutes 180 minutes 240 minutes 300 minutes acid test value 8.9 6.74 6.35 6.34 electrode passivation can not work turbidity (NTU) 236 11.1 32.9 33.2 conductivity (ps / cm) 333 842 788 783 solubility 矽Concentration (mg/L) 151.2 32.5 52.4 51 Average particle size (nm) 159 3300 1100 715 Bound potential (mV) -42.7 -30.5 -30.5 -34.3 Total organic carbon (ppb) 2781 738 945 1100

From the comparison of Table 1, Table 2 and Table 3, it is clear that the all-iron induction electrode plate of the comparative example cannot be subjected to wastewater treatment for more than 5 hours due to electrode passivation. Compared with the comparative examples, the electrodes of Examples 1 and 2 of the present invention were still functioning normally after 5 hours. The segmented sensing electrodes (Example 1) are compared with the staggered sensing electrodes (Case 2). The segment setting performance is 0956-A21950TWF (N2); P55950095TW: hsuhuche 12 1328566 is better than the staggered setting. In summary, the design of the iron sensing electrode of the present invention in combination with the aluminum sensing electrode is better than when all the sensing electrodes are of a single material. In the preferred embodiment, the experimental results of the arrangement of the 'iron-sensing electrode and the sensing electrode are best. While the invention has been described above in terms of several preferred embodiments, the present invention is not intended to be limited to the scope of the invention. The scope of protection of the present invention is subject to the scope of the patent application.

0956-A21950TWF(N2):P55950095TW:hsuhuche 13 1328566 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an electrocoagulation reactor of a preferred embodiment of the present invention, wherein a portion of the sensing electrode and the iron sensing electrode are disposed, 2 is a schematic view of an electrocoagulation reactor of Embodiment 2 of the present invention, wherein the sensing electrode and the iron sensing electrode are disposed in a wrong manner, and FIG. 3 is a schematic view of the electrocoagulation reactor of the comparative example of the present invention, wherein only iron Induction electrode. [Main component symbol description] 1 ~ electrocoagulation reactor; 10 ~ power supply; 10 A ~ anode; 10B ~ cathode; 11A, 11B ~ conductive electrode, 13 A ~ Ming induction electrode; 13B ~ iron induction electrode.

0956-A21950TWF(N2): P55950095TW: hsuhuche 14

Claims (1)

1328566 X. Patent Application Range: 1. An electrocoagulation reactor comprising: an anode and a cathode; a plurality of conducting electrodes respectively connected to the anode and the cathode; a plurality of aluminum sensing electrodes located at the conducting electrodes And a plurality of iron sensing electrodes 'between the guiding electrodes. 2. The electrocoagulation reactor of claim 1, wherein the conductive electrodes comprise an iron electrode or an aluminum electrode. 3. The electrocoagulation reactor of claim 1, wherein the aluminum sensing electrodes are interleaved with the iron sensing electrodes. 4. The electrocoagulation reactor of claim 1, wherein the inductive electrode plates are disposed with the iron sensing electrode segments. 5. The electrocoagulation reactor of claim 1, wherein the number of the conductive electrodes is between 2 and 6. 6. The electrocoagulation reactor of claim 1, wherein the number of the sensing electrodes and/or the number of the ferroelectric sensing electrodes between the conducting electrodes is between 1 and 16. 7. The electrocoagulation reactor of claim 1, wherein the conductive electrodes, the aluminum sensing electrodes, and the iron sensing electrodes are in the form of a plate, a column, or a tube. 8. The electrocoagulation reactor of claim 1, wherein the iron sensing electrodes comprise iron, steel, or stainless steel. 9. A method for treating wastewater, comprising: introducing a wastewater into an electrocoagulation reaction as described in claim 1 of the patent scope 0956-A21950TWF (N2); P55950095TW: hsuhuche 1328566 gs. · σσ, introducing a DC current to make the wastewater The aluminum sensing electrodes between the guiding electrodes and the iron sensing electrodes generate an induced current, which generates iron ions and aluminum ions to form a rubber feather, and the rubber feathers and the suspended particles of the wastewater gather; removing the rubber feathers and the wastewater The suspended particles are aggregated. 10. The method of treating wastewater according to claim 9, further comprising adjusting the pH of the wastewater to between pH 5 and pH 7 before removing the colloid and the suspended particulates of the wastewater. 11. The wastewater treatment method of claim 9, wherein the source of the wastewater comprises a chemical mechanical polishing process. 12. The wastewater treatment method of claim 9, wherein the method further comprises adding an oxidant prior to introducing the wastewater into the electro-coagulation reactor. 13. The wastewater treatment method of claim 12, wherein the oxidant comprises oxygen, ozone, hydrogen peroxide, fluorine gas, chlorine gas, or a combination thereof. 14. The wastewater treatment method of claim 9, wherein the direct current is between 10 and 25 amps. 15. The method for treating wastewater according to claim 9, wherein the polarity of the direct current is reversed after an interval, and the electrical properties of the cathode and the anode are reversed, wherein the interval is between about 1-5 Between minutes. 16. The wastewater treatment method of claim 9, wherein the aluminum sensing electrodes of the electrocoagulation reactor are interdigitated with the iron sensing electrodes. 17. The wastewater treatment method according to claim 9, wherein 0956~A21950TWF(N2); P55950095TW:hsuhuche]6 1328566 the electro-coagulation reactor of the sensing electrode plate and the iron sensing electrode system Section settings. 18. The wastewater treatment method according to claim 9, wherein the step of removing the agglomeration of the rubber feathers and the suspended particles of the wastewater comprises precipitation, filtration, flotation, overflow or a combination thereof. 0956-A21950TWF(N2); P55950095TW; hsuhuche