A device for treating fluorine-containing organic wastewater

Abstract

The utility model discloses a kind of fluorine-containing organic wastewater treatment devices, belong to wastewater treatment technical field, the device includes including homogeneous adjustment jar, ozone oxidation tower, chemical sedimentation tank, electro-catalytic reactor, ion exchange column, clean water pool and sequentially pipeline connection;The lower part of the ozone oxidation tower is equipped with gas distribution plate connection ozone generator;Upper portion is equipped with tail gas treatment mouth;The top of the chemical sedimentation tank is provided with calcium salt dosing device, and sludge outlet is connected to sludge collection tank at bottom portion.This utility model realizes the integrated processing of "PFAS breakage-fluorine ion precipitation-depth oxidation-resin defluorination" by multiple units cooperation, realizes PFAS high degradation rate, fluorine ion high removal rate, COD high removal rate.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment technology, specifically relating to a fluoride-containing organic wastewater treatment device, which is particularly suitable for the treatment of PFAS etching waste liquid (containing high concentrations of PFAS, fluoride ions and COD) in the semiconductor industry, and can make the treated effluent meet the requirements of the "Electronic Industry Water Pollutant Discharge Standard" (GB39731-2020). Background Technology

[0002] In semiconductor manufacturing, wet etching processes require the use of PFAS etching solutions (the core components of which are long-chain PFAS such as PFOA and PFOS, supplemented by hydrofluoric acid, isopropanol, etc.). The resulting fluoride-containing organic wastewater has the following significant characteristics: 1. PFAS is difficult to degrade: The carbon-fluorine bond energy in PFAS molecules is as high as 485kJ / mol. Conventional biological treatment methods and ordinary oxidation methods cannot effectively break this chemical bond, which leads to the easy accumulation of PFAS in the environment. Moreover, existing treatment technologies, such as the "ozone oxidation + biological treatment" process disclosed in CN117819696A, are insufficient for the degradation of PFAS and are difficult to meet emission requirements.

[0003] Fluoride ions are highly corrosive: The concentration of fluoride ions in wastewater is usually 500-2000 mg / L, which is extremely corrosive to traditional electrocatalytic electrodes (such as titanium-based DSA electrodes), resulting in a shortened electrode life of only 100-200 hours. Frequent replacement is required, which not only increases maintenance costs but also easily causes wastewater leakage during replacement, leading to secondary pollution. For example, CN211847486U uses a titanium-based electrode, which does not solve the problem of fluoride corrosion.

[0004] Poor device decentralization: Existing treatment processes mostly adopt separate devices for "pretreatment tank + oxidation tower + sedimentation tank + defluorination column", such as the magnetic coagulation-ion exchange process in CN120553906A. A single set of devices requires 50-80m² of space and has more than 20 pipeline connection nodes, which are prone to problems such as pipeline blockage and uneven mixing of reagents. Moreover, this process is only suitable for wastewater with fluoride ion concentration ≤300mg / L and cannot treat high-concentration fluoride-containing organic wastewater.

[0005] Simultaneous compliance is difficult: The "Emission Standard of Water Pollutants for Electronic Industry" (GB39731-2020) requires that fluoride-containing organic wastewater must simultaneously meet the requirements of "PFAS≤5μg / L, fluoride ions≤1mg / L, and COD≤50mg / L". Existing equipment has difficulty achieving simultaneous compliance of the three indicators due to problems such as electrode corrosion and poor unit synergy.

[0006] In summary, existing technologies for treating fluoride-containing organic wastewater cannot solve the complex problem of "fluoride corrosion and recalcitrant degradation," and there is an urgent need to develop an integrated treatment device that is resistant to fluoride corrosion and highly efficient in degradation. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide an integrated, efficient, and corrosion-resistant PFAS fluoride-containing organic wastewater treatment device.

[0008] The specific technical solution is as follows: A device for treating fluoride-containing organic wastewater includes a homogenization tank, an ozone oxidation tower, a chemical precipitation tank, an electrocatalytic reactor, an ion exchange column, and a clear water tank, which are connected in sequence by pipelines. The homogenizing tank is equipped with a wastewater inlet and an acid / alkali dosing port at the top, and has an internal stirrer and pH meter; it is made of fiberglass, which is resistant to acid corrosion and has no metal ion leaching within the pH range of 1-14; The ozone oxidation tower is equipped with a gas distribution plate at the bottom connected to an ozone generator; an activated carbon adsorption column is installed at the upper tail gas treatment port; and a wastewater distributor is connected at the water inlet. The top of the chemical precipitation tank is equipped with a calcium salt dosing device, which can add CaCl2 and Ca(OH)2 in stages, and the bottom is opened to connect to the sludge collection tank.

[0009] A No. 2 booster pump and a filter are installed between the chemical precipitation tank and the electrocatalytic reactor, and are connected by pipelines; the electrocatalytic reactor adopts a BDD anode and a carbon felt cathode.

[0010] This invention achieves integrated treatment of "PFAS bond breaking - fluoride ion precipitation - deep oxidation - resin defluorination" through multi-unit collaboration, resulting in high PFAS degradation rate, high fluoride ion removal rate, and high COD removal rate. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the fluoride-containing organic wastewater treatment device of this utility model. Detailed Implementation

[0012] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto.

[0013] like Figure 1 As shown, a fluoride-containing organic wastewater treatment device includes a homogenization tank 1, an ozone oxidation tower 6, a chemical precipitation tank 12, an electrocatalytic reactor 19, an ion exchange column 20, and a clear water tank 21, which are connected in sequence by pipelines. The homogenizing tank 1 is equipped with a wastewater inlet 2 and an acid / alkali dosing port at the top, and has a stirrer 3 and a pH meter 4 inside; it is made of fiberglass, which is resistant to acid corrosion and has no metal ion leaching in the pH range of 1-14; The ozone oxidation tower 6 is equipped with a gas distribution plate 7 at the bottom, which is connected to the ozone generator 10; the upper tail gas treatment port 9 is equipped with an activated carbon adsorption column; and a wastewater distributor 8 is connected to the water inlet. The top of the chemical precipitation tank 12 is equipped with a calcium salt dosing device 11, which can add CaCl2 and Ca(OH)2 in stages, and the bottom is opened to connect to the sludge collection tank 13.

[0014] A No. 2 lift pump 14 and a filter 15 are provided between the chemical precipitation tank 12 and the electrocatalytic reactor 19, and are connected by pipelines; the electrocatalytic reactor 19 adopts a BDD anode and a carbon felt cathode.

[0015] The working process of this utility model's fluoride-containing organic wastewater treatment device is as follows: 1. Homogenization and Conditioning: Fluorine-containing organic wastewater enters homogenization and conditioning tank 1 through wastewater inlet 2. pH value is monitored by pH meter 4. 10% sulfuric acid or sodium hydroxide solution is added through acid / alkali addition port 17 to adjust the pH to 3.0-4.0. Stirring is performed by agitator 3 for 30 minutes to homogenize the water quality. Then, the wastewater is pumped into ozone oxidation tower 6 through lift pump 5 and evenly distributed into ozone oxidation tower 6 by wastewater distributor 8. 2. Ozone oxidation pretreatment: Ozone generator 10 produces high-concentration ozone of 50-100 mg / L, which is dispersed into the wastewater through a PTFE gas distribution plate 7 with a pore size of 0.5-1 mm. After reacting for 60 minutes, the long-chain carbon-fluorine bonds of PFAS can be initially broken, such as decomposing PFOA into C4-C6 short-chain fluorocarboxylic acids. At the same time, some small-molecule organic matter such as COD, such as isopropanol, is oxidized, which reduces the burden on subsequent electrocatalytic oxidation. After the tail gas is treated by the activated carbon adsorption column at the tail gas treatment port 9, the residual ozone is ≤0.1 mg / m3, which meets the requirements of "Occupational Exposure Limits for Hazardous Factors in the Workplace" (GBZ 2.1-2019) before being discharged. The wastewater flows into the chemical precipitation tank 12 by gravity. 3. Chemical precipitation and solid-liquid separation: Calcium salt dosing device 11 first adds 1.0-2.0 g / L CaCl2, Ca²⁺ reacts with fluoride ions for 20 min to generate CaF₂ precipitate (Ksp=3.4×10⁻¹¹); then 0.5-1.0 g / L Ca(OH)₂ is added to adjust the pH to 8.0-8.5 to promote the stabilization of CaF₂ precipitate. After standing for 30 min, solid-liquid separation is achieved. The separated sludge enters the sludge collection tank 13 through the bottom sludge discharge port. The fluoride ion concentration of the clear liquid can be reduced to below 50 mg / L. After being filtered by filter 15 by No. 2 lift pump 14, it is pumped into the electrocatalytic reactor 19. 4. Electrocatalytic oxidation deep treatment: The current density of the electrocatalytic reactor 19 is set at 30-50 mA / cm², and the electrode spacing is 5 cm. The BDD anode generates a large amount of •OH, which can efficiently degrade residual short-chain PFAS (mineralized into CO2, H2O and F⁻) and COD; the carbon felt cathode can adsorb and degrade intermediate products, avoiding secondary dissolution; the electrocatalytic oxidation reaction for 90 min can achieve a PFAS degradation rate of ≥95% and a COD removal rate of ≥90%; the BDD anode is resistant to fluorine corrosion and shows no significant corrosion after continuous operation for 500 h in a 1000 mg / L fluoride ion solution; the treated wastewater flows by gravity into the ion exchange column 20; 5. Deep defluorination: Wastewater passes through ion exchange column 20, which is filled with aminophosphonic acid-type fluoride-specific chelating resin with an adsorption capacity ≥1.2mmol / g, which can adsorb residual fluoride ions and reduce them from 50mg / L to ≤1mg / L; the treated wastewater enters clear water tank 21. 6. Standardized discharge / reuse: The water quality indicators in the clear water tank 21 are detected by a water quality monitoring instrument. Water that meets the standards is reused or discharged, while wastewater that does not meet the standards is returned for reprocessing.

[0016] Example 1: Treatment of high-concentration PFAS etching waste liquid 1. Wastewater quality: PFAS concentration 150 mg / L (as PFOA), fluoride ion 1200 mg / L, COD 3500 mg / L, pH 2.8; treatment capacity 10 m³ / h; 2. Equipment operating parameters: Homogenization tank 1: Add 10% sulfuric acid to adjust the pH to 3.5, stirrer 3 speed 150 r / min, hydraulic retention time 30 min; Ozone oxidation tower 6: ozone production 80mg / L, gas distribution plate 7 orifice diameter 0.8mm, reaction time 60min, residual ozone in tail gas 0.08mg / m³; Chemical precipitation tank 12: CaCl2 dosage 1.5g / L (stir for 20min), Ca(OH)2 dosage 0.8g / L (adjust pH to 8.2), let stand for 30min; Electrocatalytic reactor 19: current density 40mA / cm², electrode spacing 5cm, reaction time 90min, temperature control 35℃; Ion exchange column 20: resin packing height 1.2m; 3. Treatment effect: The effluent fluoride ion concentration was 0.8 mg / L (removal rate 99.9%) and COD was 42 mg / L (removal rate 98.8%), both meeting the GB 39731-2020 standard; after 500 hours of continuous operation of the BDD anode, the catalyst film thickness remained at 10.5 μm with no corrosion marks.

[0017] Example 2: Treatment of medium-concentration PFAS etching waste liquid 1. Wastewater quality: PFAS concentration 80 mg / L (as PFOS), fluoride ion 800 mg / L, COD 2200 mg / L, pH 3.1; treatment capacity 8 m³ / h; 2. Operating parameters of the apparatus: ozone production 60 mg / L, CaCl2 dosage 1.2 g / L, Ca(OH)2 dosage 0.6 g / L, electrocatalytic current density 35 mA / cm², reaction time 75 min; other parameters are the same as in Example 1; 3. Treatment effect: effluent fluoride ion 0.6mg / L (removal rate 99.9%), COD 35mg / L (removal rate 98.4%); BDD anode continuous operation for 600h without corrosion.

[0018] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the protection scope of this utility model.

Claims

1. A device for treating fluoride-containing organic wastewater, characterized in that: It includes a homogenization tank (1), an ozone oxidation tower (6), a chemical precipitation tank (12), an electrocatalytic reactor (19), an ion exchange column (20), and a clear water tank (21), which are connected in sequence by pipelines; The ozone oxidation tower (6) is equipped with a gas distribution plate at the bottom connected to the ozone generator (10); and an exhaust gas treatment port (9) at the top. The chemical precipitation tank (12) is equipped with a calcium salt dosing device (11) at the top and a sludge discharge port at the bottom connected to the sludge collection tank (13).

2. The fluoride-containing organic wastewater treatment device according to claim 1, characterized in that, The homogenizing tank (1) has a wastewater inlet (2) and an acid / alkali dosing port (17) at the top, and is equipped with a stirrer (3) and a pH meter (4) inside.

3. The fluoride-containing organic wastewater treatment device according to claim 1, characterized in that, The ozone oxidation tower (6) is connected to a wastewater distributor (8) at its inlet; and an activated carbon adsorption column is installed at the tail gas treatment port (9).

4. The fluoride-containing organic wastewater treatment device according to claim 1, characterized in that, A No. 2 booster pump (14) and a filter (15) are provided between the chemical precipitation tank (12) and the electrocatalytic reactor (19), and are connected by pipelines.

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