A system and process for deep treatment and reuse of fluorine-containing wastewater in the electronics industry

Abstract

The present invention is a system and process for deep treatment and reuse of fluorine-containing wastewater in the electronics industry. The system includes a regulating tank, a first multi-media filter, an activated carbon filter, a softening device, a filtered water tank, a security filter, an RO system, a temporary storage tank for fluorine-containing wastewater, a primary chemical mixing system for high-concentration fluorine-containing wastewater, a secondary deep defluorination system for high-concentration fluorine-containing wastewater, a second multi-media filter, a defluorination resin tower and a discharge tank, which are sequentially connected through pipelines. The regulating tank is connected to the fluorine-containing wastewater inlet pipe, and the discharge tank is connected to the standard discharge pipe. The process includes: the first step: a fluorine-containing wastewater regulating system; the second step: a reverse osmosis filtration system; the third step: a primary chemical mixing system for high-concentration fluorine-containing wastewater; the fourth step: a secondary deep defluorination system for high-concentration fluorine-containing wastewater; the fifth step: a defluorination resin system. The advantages of the present invention: the purpose of deep treatment and recycling of fluorine-containing wastewater in the electronics industry is achieved by using a process of RO concentration, two-stage chemical mixing, and the addition of a defluorination agent and a defluorination resin.

Description

Technical Field

[0001] The present invention relates to a technology for deep treatment of fluorine-containing wastewater in the electronics industry, and specifically to a system and process for deep treatment and reuse of fluorine-containing wastewater in the electronics industry, belonging to the technical field of water treatment. Background Art

[0002] The production process of electronic products (such as semiconductors, panels, photovoltaics, etc.) uses hydrofluoric acid, ammonium fluoride and other materials in pickling and wet etching processes, which will produce wastewater containing fluoride ions. This type of fluoride-containing wastewater is usually the second and third cleaning water of the process, with large water volume, less impurities, and acidic influent (pH is about 1 to 3).

[0003] Existing technologies often use methods such as calcium mixing and precipitation, and adding defluoridation agents to remove fluoride ions from water. Among them, the calcium mixing process can only remove F in water to about 10-20 mg / L, which cannot meet the existing emission standards, and there are problems such as large dosage, high sludge output, and residual calcium ion scaling in the water causing damage to subsequent processes; the defluoridation agent addition process refers to adding defluoridation agents to the first-level calcium mixing water. The effective ingredients such as aluminum and iron in the defluoridation agent form sludge precipitation together with fluoride ions, which can reduce F in the water to below 3 or 1 mg / L, meeting the existing emission requirements. However, due to the high cost and large dosage of defluoridation agents, they are generally used in projects with small water volumes.

[0004] Chinese patent CN201010525143.6 "Photovoltaic wastewater defluorination method" first adds calcium hydroxide to adjust the wastewater pH to 8.5-9.5 for chemical mixing and precipitation, and the mixed water is further removed by flotation process to remove colloids and suspended matter in the water. The treated wastewater passes through a modified double resin ion exchange column containing a gel strong acid Al-type ion exchange resin and a macroporous weak acid Al-type ion exchange resin. This method combines the calcium addition and mixing process with the defluorination resin process, which can stabilize the fluorine content of the effluent to less than 3ppm, but uses a two-stage resin tower for adsorption, resulting in a large resin consumption, high initial cost and subsequent resin regeneration costs, and does not achieve the recycling of fluorine-containing wastewater.

[0005] Chinese patent CN201811613176.9 "A method for treating fluorine-containing wastewater" has a specific process flow: first, add lime water solution to adjust the pH value of the fluorine-containing wastewater to 8-9, then add 0.3-0.4% alum, and control the pH value to 10-11, and add polyacrylamide solution for chemical mixing and precipitation. This method can only treat the fluorine in the wastewater to below 5ppm by adding lime and alum, which is far from meeting the emission standards for some areas with strict fluorine emission requirements.

[0006] Chinese patent CN201910319768.8 "A high-efficiency defluoridation agent and its application in industrial wastewater" uses a defluoridation agent to treat fluoride-containing wastewater. The defluoridation agent is a composite agent of organic high molecular cationic polymer and nano-ferric silicate polymer. The content of nano-ferric silicate polymer in the composite coagulant is 5% to 10%, and the content of organic high molecular cationic polymer is 3% to 10%. By adding the defluoridation agent in the two-stage mixing section, the fluoride ions in various fluoride-containing industrial wastewaters can be reduced to less than 1 mg / L. However, the preparation process of the defluoridation agent in this method is complicated and the preparation cost is high. At the same time, the addition of the defluoridation agent in the two-stage mixing section results in a large amount of defluoridation agent (5000 to 6000 mg / L), a sharp increase in sludge production, and high operating costs. It is not suitable for the treatment of fluoride-containing wastewater with large water volume such as the electronics industry.

[0007] From the above content, it can be seen that the existing process has the following problems: conventional calcium addition and mixed sedimentation are difficult to remove fluoride in wastewater to below 1 mg / L, and there are problems such as high sludge production due to large dosage, and scaling of residual calcium ions in the water causing damage to subsequent processes; although the addition of defluorination agents to treat fluoride-containing wastewater can treat the fluoride in the wastewater to a lower level, there are generally problems such as large dosage and high operating costs; the use of special defluorination resin technology to treat fluoride-containing wastewater has problems such as high initial investment, large resin consumption, and high calcium and magnesium content in the resin influent, which easily leads to scaling; in view of the large amount of fluoride-containing wastewater in the electronics industry, it is difficult to take into account both treatment effect and economy by using only the addition of drugs or resins, and it is impossible to achieve the recycling and reuse of fluoride-containing wastewater. Summary of the invention

[0008] The present invention proposes a system and process for deep treatment and reuse of fluorine-containing wastewater in the electronics industry. The purpose is to address the problems that the existing process for fluorine-containing wastewater in the electronics industry is difficult to treat it to below 1 mg / L, the method of adding drugs or resins alone is difficult to take into account both treatment effect and economy, and the recycling and reuse of fluorine-containing wastewater cannot be achieved. A deep treatment process for fluorine-containing wastewater is provided, which can effectively reduce the cost of adding drugs, reduce the consumption of resins, save energy and reduce consumption, and ultimately achieve wastewater reuse.

[0009] The technical solution of the present invention is a process for deep treatment and reuse of fluorine-containing wastewater in the electronics industry, comprising the following process steps:

[0010] Step 1: Fluoride-containing wastewater regulation system: Fluoride-containing wastewater is pumped to the fluoride-containing wastewater regulation tank to even out the water quality and quantity, and adjust the pH to 7-8;

[0011] Step 2: Reverse osmosis filtration system: The effluent from the fluorine-containing wastewater regulating tank passes through a multi-media filter, an activated carbon filter and a softening device in turn to remove suspended matter, some organic matter and calcium and magnesium hardness in the water. After being treated by the softening device, the fluorine-containing wastewater with a hardness of less than 1 mg / L enters the RO system after pH adjustment. The recovery rate of the RO system is >70%. The effluent from the RO system is returned to the front-end pure water system for reuse, and the reverse osmosis concentrated water enters the primary mixing system for high-concentration fluorine-containing wastewater.

[0012] Step 3: Primary chemical mixing system for high-concentration fluorine-containing wastewater: The reverse osmosis concentrated water is the concentrated high-concentration fluorine-containing wastewater. After adjusting the pH to 7-9, a single type of defluoridation agent is added to fully react for 20-30 minutes to form calcium fluoride precipitation with the fluoride ions in the wastewater. Polyacrylamide is added to react for 0.25 hours. After flocculation and precipitation for 2-3 hours, the water is discharged. The fluorine concentration in the water is 15-20 mg / L and enters the secondary deep defluoridation system for high-concentration fluorine-containing wastewater;

[0013] Step 4: Secondary deep defluorination system for high-concentration fluoride-containing wastewater: Add composite deep defluorination agent, reaction time 0.5h, adjust the effluent pH to 6-7, add polyacrylamide to react for 0.25h, flocculation and precipitation for 2-3h, and the effluent enters the defluorination resin system. At this time, the fluoride concentration in the wastewater is 3-6mg / L;

[0014] Step 5: Fluorine removal resin system: The effluent from the secondary deep defluorination system for high-concentration fluorine-containing wastewater enters a multi-media filter to remove colloids and suspended matter in the water. The filtered effluent enters a fluorine removal resin tower for deep treatment. The aluminum-containing groups of the resin are used to adsorb fluoride ions in the water. The effluent from the resin is stabilized and treated to below 1 mg / L. The resin concentrate is returned to the primary mixing system for high-concentration fluorine-containing wastewater for further treatment.

[0015] Preferably, in the reverse osmosis filtration system of the second step, a pH adjustment unit, a bactericide dosing unit and a coagulant dosing unit are provided in front of the multi-media filter. Before the fluorine-containing wastewater flows into the multi-media filter, the pH is adjusted to neutral, and after the coagulant is added, the fluorine-containing wastewater flows into the multi-media filter. Subsequently, the fluorine-containing wastewater filtered through the multi-media filter flows into the activated carbon filter.

[0016] Preferably, in the primary chemical mixing system for high-concentration fluorine-containing wastewater in the third step, the single type of defluorinating agent is a calcium chloride solution with a mass concentration of 30% or a calcium hydroxide solution with a mass concentration of 10%.

[0017] Preferably, the calcium chloride is added in an amount of a molar ratio of Ca / F=0.6 to 0.65, and the polyacrylamide concentration is 3 mg / L.

[0018] Preferably, in the fourth step high-concentration fluorine-containing wastewater secondary deep defluorination system, the concentration of the composite deep defluorination agent is 200-500 mg / L, and the concentration of the polyacrylamide is 3 mg / L.

[0019] Preferably, the composite deep defluorination agent is prepared from polyaluminium chloride, activated alumina, calcium fluoride, polyferric chloride and modified molecular sieve, and has a pH of 1 to 3.

[0020] Preferably, the mass ratio of the polyaluminium chloride, activated alumina, calcium fluoride, polyferric chloride and modified molecular sieve is 50:20:5:20:5.

[0021] Preferably, the purity of the polyaluminium chloride is defined as Al2O3 content ≥ 28%.

[0022] Preferably, in the fifth step fluorine removal resin system, the effluent from the fluorine removal resin tower is provided with a pH adjustment unit and a fluoride ion online monitor, and the effluent after treatment by the fluorine removal resin tower is adjusted to a pH of 6.5-8.5, and the effluent that meets the standards then flows into the discharge pool; if the effluent water quality is unqualified, the unqualified water is returned to the high-concentration fluorine-containing wastewater primary mixing system for treatment through the switching of valves and pipelines.

[0023] Preferably, the method further comprises sludge treatment: the precipitates produced by the primary chemical mixing system for high-concentration fluorine-containing wastewater and the secondary deep defluorination system for high-concentration fluorine-containing wastewater are introduced into a filter press for dehydration treatment, the pressed water is returned to the primary chemical mixing system for high-concentration fluorine-containing wastewater treatment, and the produced mud cake is outsourced for treatment.

[0024] A system for deep treatment and reuse of fluorine-containing wastewater in the electronics industry comprises a regulating tank, a first multi-media filter, an activated carbon filter, a softening device, a filtered water tank, a security filter, an RO system, a fluorine-containing wastewater temporary storage tank, a high-concentration fluorine-containing wastewater primary mixing system, a high-concentration fluorine-containing wastewater secondary deep defluorination system, a second multi-media filter, a defluorination resin tower and a discharge tank, which are sequentially connected through pipelines. The regulating tank is connected to a fluorine-containing wastewater inlet pipe, and the discharge tank is connected to a standard discharge pipe.

[0025] Preferably, the primary chemical mixing system for high-concentration fluorine-containing wastewater comprises a reaction tank A, a coagulation tank A, a flocculation tank A, a sedimentation tank A and an intermediate water tank A connected in sequence, and the secondary deep defluorination system for high-concentration fluorine-containing wastewater comprises a reaction tank B, a pH adjustment tank, a flocculation tank B, a sedimentation tank B and an intermediate water tank B connected in sequence; the sedimentation tank A and the sedimentation tank B are respectively connected to the sludge storage tank through pipelines, and the sludge storage tank is sequentially connected to the plate and frame filter press, the filtrate tank and the fluorine-containing wastewater temporary storage tank through pipelines; a pH adjustment unit is provided in the adjustment tank, and a bactericide dosing unit and a coagulant dosing unit are connected on the pipeline between the adjustment tank and the multi-media filter; the discharge tank is connected to the fluorine-containing wastewater temporary storage tank through a pipeline, the water outlet of the fluorine removal resin tower is connected to the discharge tank through a pipeline, a pH adjustment unit and a fluoride ion online monitor are provided on the pipeline between the fluorine removal resin tower and the discharge tank, and the concentrated water outlet of the fluorine removal resin tower is connected to the pipeline between the discharge tank and the fluorine wastewater temporary storage tank through a pipeline.

[0026] The advantages of the present invention are: the process of RO concentration, two-stage mixing, adding defluorination agent and defluorination resin is used to achieve the purpose of deep treatment and recycling of fluorine-containing wastewater in the electronics industry. Specifically:

[0027] 1. Based on the characteristics of less impurities and larger water volume in the electronics industry, the fluorine-containing wastewater is concentrated by RO process. The RO effluent is reused in the front-end pure water system, and the RO concentrated water enters the high-concentration fluorine-containing wastewater treatment system, thus realizing the recycling of fluorine-containing wastewater. At the same time, the scale of fluorine-containing wastewater treatment is reduced, and the water volume and treatment load of the mixing system are reduced.

[0028] Second, a two-stage chemical mixing process of adding defluoridation agent and defluoridation resin is used to treat high-concentration fluoride-containing wastewater. The fluoride in the effluent can be stably less than 1 mg / L, meeting the owner's deep defluoridation requirements. At the same time, by adding defluoridation agent, the fluoride in the resin inlet water can be reduced to 5-10 mg / L, which can greatly reduce the amount of defluoridation resin used, reduce regeneration costs, and reduce initial installation costs and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of the deep treatment and reuse process of fluorine-containing wastewater in the electronics industry.

[0030] Figure 2 It is a structural block diagram of the system for deep treatment and reuse of fluorine-containing wastewater in the electronics industry of the present invention.

[0031] In the figure, 1 is a regulating tank, 2 is the first multi-media filter, 3 is an activated carbon filter, 4 is a softening device, 5 is a filtered water tank, 6 is a security filter, 7 is a RO system (reverse osmosis system), 8 is a temporary storage tank for fluorine-containing wastewater, 9 is a reaction tank A, 10 is a coagulation tank A, 11 is a flocculation tank A, 12 is a sedimentation tank A, 13 is an intermediate water tank A, 14 is a reaction tank B, 15 is a pH regulating tank, 16 is a flocculation tank B, 17 is a sedimentation tank B, 18 is an intermediate water tank B, 19 is a second multi-media filter, 20 is a fluorine removal resin tower, 21 is a discharge tank, 22 is a sludge storage tank, 23 is a plate and frame filter press, and 24 is a filtrate tank. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to examples and specific implementation modes.

[0033] like Figure 2 As shown, a system for deep treatment and reuse of fluorine-containing wastewater in the electronics industry comprises a regulating tank 1, a first multi-media filter 2, an activated carbon filter 3, a softening device 4, a filtered water tank 5, a security filter 6, an RO system 7, a fluorine-containing wastewater temporary storage tank 8, a high-concentration fluorine-containing wastewater primary mixing system, a high-concentration fluorine-containing wastewater secondary deep defluorination system, a second multi-media filter 19, a defluorination resin tower 20 and a discharge tank 21, which are sequentially connected by pipelines. The regulating tank 1 is connected to the fluorine-containing wastewater inlet pipe, and the discharge tank 21 is connected to the standard discharge pipe.

[0034] The primary chemical mixing system for high-concentration fluorine-containing wastewater includes an A reaction tank 9, an A coagulation tank 10, an A flocculation tank 11, an A sedimentation tank 12 and an A intermediate water tank 13 connected in sequence, and the secondary deep defluorination system for high-concentration fluorine-containing wastewater includes a B reaction tank 14, a pH adjustment tank 15, a B flocculation tank 16, a B sedimentation tank 17 and a B intermediate water tank 18 connected in sequence.

[0035] The A sedimentation tank 12 and the B sedimentation tank 17 are connected to the sludge storage tank 22 through pipelines respectively, and the sludge storage tank 22 is connected to the plate and frame filter press 23, the filtrate tank 24 and the fluorine-containing wastewater temporary storage tank 8 in sequence through pipelines.

[0036] The regulating tank 1 is provided with a pH regulating unit, and a bactericide dosing unit and a coagulant dosing unit are connected to the pipeline between the regulating tank 1 and the multi-media filter 2 .

[0037] The discharge pool 21 is connected to the fluorine-containing wastewater temporary storage pool 8 through a pipeline, the water outlet of the fluorine removal resin tower 20 is connected to the discharge pool 21 through a pipeline, a pH adjustment unit and a fluorine ion online monitor are arranged on the pipeline between the fluorine removal resin tower 20 and the discharge pool 21, and the concentrated water outlet of the fluorine removal resin tower 20 is connected to the pipeline between the discharge pool 21 and the fluorine wastewater temporary storage pool 8 through a pipeline.

[0038] Water pumps are provided on the regulating tank 1 and the first multi-media filter 2, the filtered water tank 5 and the security filter 6, the security filter 6 and the RO system 7, the fluorine-containing wastewater temporary storage tank 8 and the A reaction tank 9, the A intermediate water tank 13 and the B reaction tank 14, the B intermediate water tank 18 and the second multi-media filter 19, the discharge tank 21 and the fluorine-containing wastewater temporary storage tank 8, the pipelines between the fluorine removal resin tower 20 and the discharge tank 21 and the fluorine-containing wastewater temporary storage tank 8, the pipelines between the A sedimentation tank 12 and the sludge storage tank 22, the B sedimentation tank 17 and the sludge storage tank 22, the sludge storage tank 22 and the plate and frame filter press 23, and the filtrate tank 24 and the fluorine-containing wastewater temporary storage tank 8.

[0039] like Figure 1 As shown in the figure, a deep treatment and reuse process of fluorine-containing wastewater in the electronics industry has the following process flow: after the pH of the fluorine-containing wastewater is adjusted in the pH adjustment tank, it is treated by a multi-media filter and an activated carbon filter and then enters a softening resin tower for softening treatment. The treated effluent enters a reverse osmosis system, and the osmotic effluent returns to the pure water system for reuse, and the concentrated water enters a high-concentration fluorine-containing wastewater treatment system. After the pH of the high-concentration fluorine-containing wastewater is adjusted, it enters a primary calcium addition and mixing system, and the mixed effluent enters a secondary deep defluorination treatment system, where the fluorine in the wastewater is treated to 3-5 mg / L, further reducing the influent load of the defluorination resin. After the treated water is filtered through a multi-media filter and adsorbed by a defluorination resin tower, the fluorine in the effluent is stabilized to less than 1 mg / L, achieving the standard discharge and recycling of fluorine-containing wastewater.

[0040] The specific steps are as follows:

[0041] Step 1: Fluoride-containing wastewater regulation system: The fluoride-containing wastewater is pumped to the fluoride-containing wastewater regulation tank to even out the water quality and quantity, and adjust the pH to 7-8.

[0042] Step 2: Reverse osmosis filtration system: The effluent from the fluorine-containing wastewater regulating tank passes through a multi-media filter, an activated carbon filter and a softening device in order to remove suspended matter, some organic matter and hardness such as calcium and magnesium in the water. Then the fluorine-containing wastewater (hardness less than 1 mg / L) treated by the softening device enters the RO system (recovery rate> 70%) after pH adjustment. The RO system permeate returns to the front-end pure water system for reuse, and the reverse osmosis concentrated water enters the high-concentration fluorine-containing wastewater primary mixing system.

[0043] The multi-media filter is provided with a pH adjustment unit, a bactericide dosing unit and a coagulant dosing unit in front of the multi-media filter. Before the fluorine-containing wastewater flows into the multi-media filter, the pH is adjusted to neutral, and after the coagulant is added, the fluorine-containing wastewater flows into the multi-media filter, and then the fluorine-containing wastewater filtered by the multi-media filter flows into the activated carbon filter.

[0044] Step 3: Primary chemical mixing system for high-concentration fluoride-containing wastewater: The reverse osmosis concentrate is the concentrated high-concentration fluoride-containing wastewater. After adjusting the pH to 7-9, a single type of defluoridation agent is added and fully reacted for 20-30 minutes. At this time, calcium chloride and fluoride ions in the wastewater form calcium fluoride precipitation. Polyacrylamide is added to react for 0.25 hours. After flocculation and precipitation for 2-3 hours, the effluent (fluoride concentration in the water is 15-20 mg / L) enters the secondary deep defluoridation system for high-concentration fluoride-containing wastewater.

[0045] The single type of defluoridating agent is a simple inorganic substance, and is preferably a calcium chloride solution with a mass concentration of 30% or a calcium hydroxide solution with a mass concentration of 10%.

[0046] The calcium chloride addition amount is a molar ratio of Ca / F=0.6-0.65, and the polyacrylamide concentration is 3 mg / L.

[0047] Step 4: Secondary deep defluorination system for high-concentration fluoride-containing wastewater: Add composite deep defluorination agent (200-500 mg / L), reaction time 0.5h, adjust the effluent pH to 6-7, add polyacrylamide to react for 0.25h, and after flocculation and sedimentation for 2-3h, the effluent enters the defluorination resin system. At this time, the fluoride concentration in the wastewater is 3-6 mg / L. Compared with the conventional calcium defluorination process (which can only remove fluoride in the wastewater to 10-20 mg / L), the amount of defluorination resin used can be greatly reduced.

[0048] The composite deep defluoridation agent is prepared from polyaluminium chloride (50%) (purity is defined as Al2O3 content ≥ 28%), activated alumina (20%), calcium fluoride (5%), polyferric chloride (20%), modified molecular sieve (5%), etc. The agent itself is acidic, with a pH of about 1 to 3. Fluoride in water is removed through the high affinity and adsorption of aluminium to fluoride ions.

[0049] The polyacrylamide concentration is 3 mg / L.

[0050] Step 5: Fluorine removal resin system: The effluent from the secondary deep defluorination system for high-concentration fluorine-containing wastewater enters the multi-media filter to remove colloids and suspended matter in the water. The filtered effluent enters the defluorination resin tower for deep treatment, and the aluminum-containing groups of the resin are used to adsorb fluoride ions in the water. The resin effluent can be stably treated to less than 1 mg / L, and the resin concentrated water returns to the primary mixing system for high-concentration fluorine-containing wastewater for further treatment.

[0051] The effluent from the fluorine removal resin tower is provided with a pH adjustment unit and an online fluoride ion monitor. The effluent treated by the fluorine removal resin adsorption tower is adjusted to a pH value of 6.5 to 8.5, and the qualified drainage then flows into the discharge pool (final drainage monitoring tank); if the drainage water quality is unqualified, the unqualified water is returned to the front end (fluorine-containing wastewater temporary storage pool) by switching valves and pipelines.

[0052] Step 6: Sludge treatment: The sediment from the previous step (in the sedimentation tank) is introduced into the filter press for dehydration treatment, and the pressed water is returned to the high-concentration fluorine-containing wastewater primary mixing system for treatment, and the resulting mud cake is outsourced for treatment.

[0053] Example 1

[0054] The water quality of fluoride-containing wastewater from a semiconductor factory is as follows: pH 1.5-3, F 300-400 mg / L, TDS 250-300 mg / L, and wastewater flow rate 3000 m 3 / d. The implementation of this case includes the following steps:

[0055] Step 1: Adjust the pH to 7 and enter the multi-media filter and activated carbon filter. The pH adjustment, bactericide dosing unit and coagulant dosing unit are set before the multi-layer filter. The fluorine-containing wastewater filtered by the activated carbon filter then flows into the softening resin tower. At this time, the hardness of the fluorine-containing wastewater is less than 1mg / L.

[0056] Step 2: The filtered water enters the RO system, and the final water production rate is 77-78%. The concentrated water produced by RO enters the high-concentration fluorine-containing wastewater treatment system, and the RO effluent is reused to the front-end pure water system.

[0057] Step 3: After the reverse osmosis concentrate is adjusted to pH 8, it enters the primary calcium addition and mixing system, where calcium chloride (Ca / F=0.6, molar ratio) and polyacrylamide (3 mg / L) are added in sequence, reacting for 0.5 h and 0.25 h respectively. After settling for 2 h, the mixed water enters the secondary deep defluorination system. The fluoride content of the primary mixed water is 18-20 mg / L.

[0058] Step 4: Add composite deep defluoridation agent (300 mg / L) directly to the first-stage calcified mixed water, adjust the pH to 7 after 0.5h of reaction, add polyacrylamide (3 mg / L, 0.25h), and after 2h of precipitation, the mixed water enters the defluoridation resin system. The fluoride content of the secondary mixed water is 5-6 mg / L.

[0059] Step 5: The effluent treated by the fluorine removal resin adsorption tower is mixed in a pipeline mixer and the pH value is adjusted to 7. The qualified effluent then flows into the final drainage monitoring tank. At this time, the fluorine content of the effluent is 0.2 mg / L.

[0060] Example 2

[0061] The water quality of fluoride-containing wastewater from a panel factory is as follows: pH is 2-3, F is 200-300 mg / L, TDS is 500-600 mg / L, and the wastewater flow rate is 2000 m 3 / d. The implementation of this case includes the following steps:

[0062] Step 1: Adjust the pH to 7 and enter the multi-media filter and activated carbon filter. The pH adjustment, bactericide dosing unit and coagulant dosing unit are installed in front of the multi-layer filter. The fluorine-containing wastewater filtered by the activated carbon filter then flows into the softening resin tower. At this time, the hardness of the fluorine-containing wastewater is less than 1 mg / L.

[0063] Step 2: The filtered water enters the RO system, and the final water production rate is 75%. The concentrated water produced by RO enters the high-concentration fluorine-containing wastewater treatment system, and the RO effluent is reused in the front-end pure water system.

[0064] Step 3: After the reverse osmosis concentrate is adjusted to pH 7, it enters the primary calcium addition and mixing system, and calcium chloride (Ca / F=0.65, molar ratio) and polyacrylamide (3 mg / L) are added in sequence, reacting for 0.5 h and 0.25 h respectively. After settling for 2 h, the mixed water enters the secondary deep defluorination system. The fluoride content of the primary mixed water is about 15 mg / L.

[0065] Step 4: Add composite deep defluoridation agent (200 mg / L) directly to the first-stage calcified mixed water, adjust the pH to 6.5 after 0.5h of reaction, add polyacrylamide (3 mg / L, 0.25h), and after 2h of precipitation, the mixed water enters the defluoridation resin system. The fluoride content of the secondary mixed water is about 5 mg / L.

[0066] Step 5: The effluent treated by the fluorine removal resin adsorption tower is mixed in a pipeline mixer and the pH value is adjusted to 7. The qualified effluent then flows into the final drainage monitoring tank. At this time, the fluorine content of the effluent is about 0.15 mg / L.

[0067] Comparative Example

[0068] The water quality of fluoride wastewater from a semiconductor factory is as follows: pH is 2-3, F is 300-400 mg / L, TDS is about 300 mg / L, and the wastewater flow rate is 1000 m 3 / d. The implementation of this case includes the following steps:

[0069] Step 1: After the fluoride-containing wastewater is adjusted to pH 8, it enters the primary calcium addition and mixing system, and calcium chloride (Ca / F=0.65, molar ratio) and polyacrylamide (3 mg / L) are added in sequence, reacting for 0.5 h and 0.25 h respectively. After settling for 2 h, the mixed water enters the secondary deep defluorination system. The fluoride content of the primary mixed water is 15-20 mg / L.

[0070] Step 2: Add composite deep defluorination agent (2000 mg / L) directly to the first-stage calcified mixed water, adjust the pH to 7 after 0.5h of reaction, add polyacrylamide (3 mg / L, 0.25h), and adjust the pH of the mixed water to 7 after 2h of precipitation before meeting the discharge standards. At this time, the fluoride content of the effluent is 0.58 mg / L.

[0071] Step 3: The sediment in the primary and secondary sedimentation tanks is introduced into the filter press for dehydration treatment, the squeezed water is returned to the primary mixing system for treatment, and the resulting mud cake is outsourced for treatment.

[0072] The process of "primary calcium addition + secondary defluorination agent addition" is adopted, and the dosage of defluorination agent is 2.0kg / d, and the operating cost is about 11.77 yuan / ton of water. Compared with this process, the dosage of the patented agent is 0.4kg / d, which is 80% lower than the same period last year; the operating cost is about 4.07 yuan / ton of water, which is 65.4% lower than the same period last year; at the same time, the average water production rate of recycled water is 72-74%, which can greatly reduce the amount of fresh water.

[0073] For those skilled in the art, under the inspiration of the concept and specific embodiments of this patent, some variations can be directly derived or associated from the disclosure of this patent and common sense. Ordinary technicians in this field will realize that other methods can also be used, or commonly known technologies in the prior art can be used instead, as well as changes in parameters such as dosage, reaction time, or slightly beyond this range, etc. Non-substantial changes can also be applied, and can achieve the functions and effects described in this patent. No more examples will be given in detail, and they all fall within the scope of protection of this patent.

Claims

1. A process for deep treatment and reuse of fluorine-containing wastewater in the electronics industry, characterized in that: The process steps include: Step 1: Fluoride-containing wastewater regulation system: Fluoride-containing wastewater is pumped to the fluoride-containing wastewater regulation tank to even out the water quality and quantity, and adjust the pH to 7-8; Step 2: Reverse osmosis filtration system: The effluent from the fluorine-containing wastewater regulating tank passes through a multi-media filter, an activated carbon filter and a softening device in turn to remove suspended matter, some organic matter and calcium and magnesium hardness in the water. After being treated by the softening device, the fluorine-containing wastewater with a hardness of less than 1 mg / L enters the RO system after pH adjustment. The recovery rate of the RO system is >70%. The effluent from the RO system is returned to the front-end pure water system for reuse, and the reverse osmosis concentrated water enters the primary mixing system for high-concentration fluorine-containing wastewater. Step 3: Primary chemical mixing system for high-concentration fluorine-containing wastewater: The reverse osmosis concentrated water is the concentrated high-concentration fluorine-containing wastewater. After adjusting the pH to 7-9, a single type of defluoridation agent is added to fully react for 20-30 minutes to form calcium fluoride precipitation with the fluoride ions in the wastewater. Polyacrylamide is added to react for 0.25 hours. After flocculation and precipitation for 2-3 hours, the water is discharged. The fluorine concentration in the water is 15-20 mg / L and enters the secondary deep defluoridation system for high-concentration fluorine-containing wastewater. Step 4: Secondary deep defluorination system for high-concentration fluoride-containing wastewater: Add composite deep defluorination agent, reaction time 0.5 h, adjust the effluent pH to 6-7, add polyacrylamide to react for 0.25 h, and after flocculation and sedimentation for 2-3 h, the effluent enters the defluorination resin system. At this time, the fluoride concentration in the wastewater is 3-6 mg / L; Step 5: Fluorine removal resin system: The effluent from the secondary deep defluorination system for high-concentration fluorine-containing wastewater enters a multi-media filter to remove colloids and suspended matter in the water. The filtered effluent enters a defluorination resin tower for deep treatment. The aluminum-containing groups of the resin are used to adsorb fluoride ions in the water. The fluorine content in the resin effluent is stabilized to less than 1 mg / L. The resin concentrated water is returned to the primary chemical mixing system for high-concentration fluorine-containing wastewater for further treatment. In the primary chemical mixing system of high-concentration fluorine-containing wastewater in the third step, the single type of defluoridating agent is a calcium chloride solution with a mass concentration of 30% or a calcium hydroxide solution with a mass concentration of 10%; In the third step, the amount of calcium chloride added is a molar ratio of Ca / F=0.6-0.65, and the concentration of polyacrylamide is 3 mg / L; In the fourth step of the high-concentration fluorine-containing wastewater secondary deep defluorination system, the concentration of the composite deep defluorination agent is 200-500 mg / L, and the concentration of the polyacrylamide is 3 mg / L; The composite deep defluorination agent is prepared from polyaluminium chloride, activated alumina, calcium fluoride, polyferric chloride and modified molecular sieve, and has a pH of 1-3; The mass ratio of the polyaluminium chloride, activated alumina, calcium fluoride, polyferric chloride and modified molecular sieve is 50:20:5:20:5; The purity of the polyaluminium chloride is defined as Al2O3 content ≥ 28%; In the fifth step of the fluorine removal resin system, the effluent from the fluorine removal resin tower is provided with a pH adjustment unit and a fluoride ion online monitor. The effluent treated by the fluorine removal resin tower is adjusted to a pH of 6.5-8.5, and the qualified drainage then flows into the drainage pool; if the drainage water quality is unqualified, the unqualified water is returned to the high-concentration fluorine-containing wastewater primary mixing system for treatment through the switching of valves and pipelines; It also includes sludge treatment: the sediment produced by the primary chemical mixing system of high-concentration fluorine-containing wastewater and the secondary deep defluorination system of high-concentration fluorine-containing wastewater is introduced into the filter press for dehydration treatment, the pressed water is returned to the primary chemical mixing system of high-concentration fluorine-containing wastewater for treatment, and the produced mud cake is outsourced for treatment.

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