Method for resource utilization treatment of acidic wastewater produced in production of viscose fibers

Abstract

The application relates to a resource utilization treatment method for acidic wastewater produced in viscose fiber production, which comprises the following steps: S1: performing ultrafiltration treatment on the wastewater to obtain ultrafiltration produced water; S2: performing primary reverse osmosis treatment on the ultrafiltration produced water to obtain primary reverse osmosis produced water and primary reverse osmosis concentrated water; S3: performing secondary reverse osmosis treatment on the primary reverse osmosis produced water to obtain secondary reverse osmosis produced water and secondary reverse osmosis concentrated water, wherein the secondary reverse osmosis produced water is used as recycled water, and the secondary reverse osmosis concentrated water is subjected to primary reverse osmosis treatment again; S4: performing high-level oxidation treatment on the primary reverse osmosis concentrated water to obtain oxidation produced water, which is input into an ion exchange device to obtain ion exchange produced water; S5: inputting the ion exchange produced water into an alloy membrane electrodialysis device to perform electrodialysis treatment, so as to obtain electrodialysis produced water and electrodialysis fresh water, wherein the electrodialysis fresh water is subjected to primary reverse osmosis treatment again; and S6: performing secondary electrodialysis treatment on the electrodialysis produced water to obtain sulfuric acid and sodium hydroxide.

Description

Technical Field

[0001] This invention belongs to the field of acidic wastewater treatment technology, specifically relating to a method for the resource utilization and treatment of acidic wastewater generated during the production of viscose fibers. Background Technology

[0002] Viscose fiber is a cellulose fiber made from cotton pulp and / or wood pulp, and is currently one of the main types of man-made fibers in my country. Due to its good hygroscopicity, ease of dyeing, static-free properties, comfort, and spinnability, it is often blended or interwoven with cotton, wool, or various synthetic fibers for use in various clothing and decorative textiles. High-strength viscose fiber can also be used in industrial products such as tire cord and conveyor belts. In the production process of viscose fiber, wet spinning and post-treatment are typically carried out using a coagulation bath. Multiple washing processes generate acidic wastewater mainly composed of sulfuric acid and sodium sulfate, with an H2SO4 content of 5000-6000 mg / L. This acidic wastewater poses a serious corrosion problem to wastewater treatment equipment; the wastewater also exhibits some hardness and high SO4 content. 2- The content is very high, and the membrane system is at risk of scaling.

[0003] Currently, the treatment process for this acidic wastewater is as follows: first, flocculation and sedimentation, then filtration using a multi-media filter and a self-cleaning filter, followed by ultrafiltration and multi-stage reverse osmosis treatment to obtain permeate, and the concentrate produced by the membrane treatment is returned to the membrane treatment. This method has the following shortcomings: (1) Acidic wastewater has a certain corrosive effect on equipment and pipelines such as multi-media filters and self-cleaning filters; (2) The effect of adding chemicals to precipitate acidic wastewater is not obvious; (3) Acid-resistant ultrafiltration membranes are expensive, and their service life is short and the replacement cost is high when operating under acidic conditions for a long time; (4) Filtration, ultrafiltration and reverse osmosis equipment are prone to scaling and clogging, requiring frequent cleaning; (5) The volume of the concentrate produced by reverse osmosis is equivalent to 30% of the influent, and this concentrate is currently discharged to the sewage treatment plant, which is still difficult to treat. Summary of the Invention

[0004] To address the above problems, this invention provides a method for the resource utilization and treatment of acidic wastewater generated during the production of viscose fibers, comprising the following steps:

[0005] S1: Acidic wastewater is fed into a ceramic membrane ultrafiltration device for ultrafiltration treatment to obtain ultrafiltration permeate;

[0006] S2: The ultrafiltration permeate undergoes primary reverse osmosis treatment to obtain primary reverse osmosis permeate and primary reverse osmosis concentrate;

[0007] S3: The primary reverse osmosis permeate is treated by secondary reverse osmosis to obtain secondary reverse osmosis permeate and secondary reverse osmosis concentrate. The secondary reverse osmosis permeate can be used as recycled water. The secondary reverse osmosis concentrate is mixed with the ultrafiltration permeate and then treated by primary reverse osmosis.

[0008] S4: The concentrated water from the first-stage reverse osmosis undergoes advanced oxidation treatment. The resulting oxidation permeate is then fed into an ion exchange unit to remove divalent or higher cations from the wastewater, yielding ion exchange permeate.

[0009] S5: Ion exchange permeate is fed into the alloy membrane electrodialysis unit for electrodialysis treatment to obtain electrodialysis permeate and electrodialysis desalinated water. The electrodialysis desalinated water is returned to the first-stage reverse osmosis unit for further first-stage reverse osmosis treatment.

[0010] S6: Electrodialysis permeate is fed into a bipolar membrane electrodialysis unit for secondary electrodialysis treatment to obtain sulfuric acid and sodium hydroxide.

[0011] Optionally, in step S1, the acidic wastewater is first fed into the raw water tank for homogenization and adjustment, and then fed into the ceramic membrane ultrafiltration device for ultrafiltration treatment to remove suspended solids in the wastewater and reduce the turbidity of the water.

[0012] The ultrafiltration permeate is fed into the ultrafiltration permeate tank, which is connected to the first-stage reverse osmosis unit to feed the ultrafiltration permeate into the first-stage reverse osmosis unit.

[0013] The cleaning wastewater from the ceramic membrane ultrafiltration unit is returned to the raw water tank and mixed with the raw water to reduce the amount of wastewater discharged.

[0014] This invention uses a ceramic membrane ultrafiltration device to replace the sedimentation tank and multi-stage filtration in the traditional process, which can greatly shorten the process flow. The ceramic ultrafiltration membrane has strong acid and alkali resistance, high strength, and long service life, making it suitable for treating acidic wastewater and greatly reducing the frequency of cleaning and downtime.

[0015] Optionally, in step S2, the first-stage reverse osmosis unit is connected to the first-stage concentrate tank and the first-stage product water tank, which are used to temporarily store the first-stage reverse osmosis concentrate and the first-stage reverse osmosis product water, respectively; the first-stage product water tank is connected to the inlet of the second-stage reverse osmosis unit, and the first-stage concentrate tank is connected to the inlet of the advanced oxidation unit.

[0016] After adjusting the pH of the primary reverse osmosis permeate to neutral by adding alkali, it is fed into the primary permeate tank.

[0017] Optionally, in step S3, the secondary reverse osmosis concentrate is input into the ultrafiltration permeate tank, mixed with the ultrafiltration permeate, and then input into the primary reverse osmosis unit, which can improve the permeate production rate and reduce the amount of concentrate discharged.

[0018] Optionally, in step S4, the advanced oxidation treatment is used to remove organic pollutants from the wastewater. The outlet of the advanced oxidation device is connected to a first intermediate water tank, which is connected to an ion exchange device. Alkali is added to the first intermediate water tank to adjust the pH of the oxidation product water to neutral.

[0019] Optionally, in step S4, the ion exchange device is filled with chelating resin to adsorb divalent or higher cations in the wastewater, thereby preventing scaling of subsequent equipment. The waste liquid generated from the washing and regeneration of the chelating resin has relatively few pollutants and is discharged to the sewage treatment plant.

[0020] Optionally, in step S5, in the alloy membrane electrodialysis device, the salt in the wastewater is transferred to the concentrate side under the action of the electric field to obtain electrodialysis permeate (i.e., concentrated brine) and electrodialysis desalinated water. The electrodialysis desalinated water is returned to the first-stage reverse osmosis device, which can improve the water production rate of the entire system. The electrodialysis permeate is temporarily stored in the second intermediate water tank, which is connected to the bipolar membrane electrodialysis device.

[0021] Optionally, in step S6, the electrodialysis permeate concentrated by the alloy membrane electrodialysis device enters the bipolar membrane electrodialysis device, and at the same time, pure water is input into the bipolar membrane electrodialysis device for secondary electrodialysis treatment to obtain recovered sulfuric acid and sodium hydroxide, thereby achieving resource recovery; the residual liquid of the bipolar membrane electrodialysis device has a low salt content and is returned to the alloy membrane electrodialysis device to continue to participate in electrodialysis treatment.

[0022] This invention effectively treats the concentrate from two-stage reverse osmosis. The concentrate from the first-stage reverse osmosis undergoes advanced oxidation treatment, followed by hardening removal, and then recovers sulfuric acid and sodium hydroxide via electrodialysis, achieving resource recovery. The concentrate from the second-stage reverse osmosis is returned to the ultrafiltration permeate tank, i.e., returned to the first-stage reverse osmosis. The residual liquid from the bipolar membrane electrodialysis unit is returned to the alloy membrane electrodialysis unit. These measures significantly reduce the amount of wastewater discharged.

[0023] The acidic wastewater generated during the production of viscose fiber contains a large amount of recalcitrant pollutants. Advanced oxidation treatment methods mainly include Fenton oxidation and ozone oxidation. However, ozone oxidation has limited oxidation capacity and is selective, only oxidizing a portion of pollutants; direct Fenton oxidation requires large dosages, resulting in high sludge production and operating costs. This invention provides an oxidation reactor that couples Fenton oxidation with electro-oxidation to improve the oxidation treatment effect.

[0024] Optionally, the oxidation reactor coupled with Fenton reaction includes, from the outside to the inside, a first electrode plate, a second electrode plate, and an enhanced reaction cylinder. The first electrode plate and the second electrode plate are electrically connected to the positive and negative terminals of an external power source, respectively, for electro-oxidation treatment. The enhanced reaction cylinder is equipped with a stirring device, and an oxidant dosing pipe is provided at the bottom of the oxidation reactor and at the position corresponding to the enhanced reaction cylinder, for introducing oxidant into the enhanced reaction cylinder to carry out the Fenton reaction.

[0025] The oxidation reactor controls the flow of wastewater through a first electrode plate, a second electrode plate, and a reinforced reaction cylinder arranged sequentially from the outside in, thereby achieving three-stage oxidation decomposition of pollutants in the wastewater through electro-oxidation, Fenton oxidation, and hydrogen peroxide oxidation.

[0026] Optionally, the oxidation reactor is cylindrical, and the first electrode plate, the second electrode plate, the enhanced reaction cylinder, and the outer shell of the oxidation reactor are all concentrically arranged; the space between the outer shell and the first electrode plate is the first cavity, the space between the first electrode plate and the second electrode plate is the second cavity, and the space between the second electrode plate and the enhanced reaction cylinder is the third cavity.

[0027] The top of the outer shell is equipped with a water inlet pipe for inputting wastewater into the first chamber. The wastewater then flows through the second and third chambers in sequence for electro-oxidation treatment. Then the wastewater flows through the interior of the enhanced reaction cylinder for Fenton oxidation treatment.

[0028] Further optionally, the top of the first electrode plate is higher than the liquid level of the first and second chambers, and the bottom is suspended, so that the wastewater in the first chamber flows from top to bottom and then enters the second chamber from the bottom of the first electrode plate.

[0029] The top of the second electrode plate is lower than the top of the first electrode plate, and the bottom is connected to the bottom surface of the oxidation reactor, so that the wastewater in the second chamber flows from bottom to top and then overflows from the top of the second electrode plate to the third chamber.

[0030] The top of the enhanced reaction tube is higher than the liquid level in the third chamber, and the bottom is suspended, so that the wastewater in the third chamber flows from top to bottom and then enters the enhanced reaction tube from the bottom.

[0031] Further optionally, the diameter of the bottom of the enhanced reaction cylinder is larger than the diameter of its other parts, that is, the bottom is open, so that the wastewater input from the third chamber and the oxidant from the oxidant dosing pipe can enter the enhanced reaction cylinder.

[0032] The upper part of the enhanced reaction cylinder is equipped with a water outlet pipe, which is connected to the first intermediate water tank.

[0033] The top of the first electrode plate and the top of the enhanced reaction cylinder are connected to the top surface of the oxidation reactor via a connecting component.

[0034] Optionally, a first aeration pipe is provided on the bottom surface of the oxidation reactor at a position corresponding to the first and second chambers, for pneumatically agitating the water in the first and second chambers.

[0035] Because Fenton oxidation produces a lot of sludge, some small sludge particles enter the coagulation zone with the permeate, while some large sludge particles settle to the bottom of the oxidation reactor. Meanwhile, oxidant and water from the third chamber need to enter the enhanced reaction tank below, causing the bottom feed water to disturb the sludge, which causes the sludge to return to the enhanced reaction tank. At the same time, the sludge also occupies space in the enhanced reaction tank and the oxidation reactor, reducing the amount of wastewater treated.

[0036] Optionally, the oxidant dosing pipe is annular, and the diameter of the oxidant dosing pipe is slightly smaller than the diameter of the bottom of the enhanced reaction cylinder, so that the hydrogen peroxide input through the oxidant dosing pipe preferentially enters the edge of the enhanced reaction cylinder.

[0037] The nozzle of the oxidant dosing pipe is set downwards to prevent sludge falling from the enhanced reaction cylinder from clogging the nozzle and affecting the dosing; the oxidant is hydrogen peroxide.

[0038] Optionally, a guide plate is provided at the bottom of the second electrode plate. The guide plate is located below the oxidant dosing pipe. The guide plate is a downwardly concave arc-shaped plate with the same height on both sides. The outer side is fixed on the side of the second electrode facing the enhanced reaction cylinder, and the inner side is suspended.

[0039] The circumference of the guide plate is not less than the circumference of the oxidant dosing pipe, so that the water flow guided by the guide plate into the bottom of the enhanced reaction cylinder can cover the dosing area of ​​the oxidant dosing pipe and carry hydrogen peroxide into the edge of the enhanced reaction cylinder.

[0040] Optionally, the edge of the enhanced reaction cylinder is provided with several stirring devices, which are evenly arranged along the circumference of the enhanced reaction cylinder to stir the sewage and hydrogen peroxide rising from the edge of the enhanced reaction cylinder.

[0041] The motor of the stirring device is located above the outside of the oxidation reactor, and the stirring shaft extends into the enhanced reaction cylinder to stir the wastewater inside the enhanced reaction cylinder and promote the reaction between the wastewater and the oxidant.

[0042] Further optionally, the center of the enhanced reaction cylinder is provided with a separation stirrer, the rotating shaft of the separation stirrer passes through the top plate of the oxidation reactor and is connected to the corresponding drive motor, and a number of stirring parts are evenly arranged from top to bottom on the rotating shaft; the stirring part includes a number of inclined stirring plates, and the number of stirring plates are evenly arranged along the circumference of the rotating shaft, the inner side of the stirring plate is connected to the outer side of the rotating shaft, and the outer side points to the outside of the enhanced reaction cylinder, and each stirring plate has an angle of -° with the vertical direction.

[0043] The speed of the separator agitator is less than that of the agitator. The separator agitator is used to agitate and enhance the water in the middle of the reaction tank to promote the contact and reaction between wastewater and oxidant. At the same time, the inclined agitator plate can promote the separation of mud and water, so that the sludge slides down the inclined surface of the agitator plate.

[0044] This invention, through the arrangement of the oxidant dosing pipe and the guide plate, allows the wastewater in the third chamber to be redirected by the arc-shaped guide plate, passing under the oxidant dosing pipe and carrying hydrogen peroxide upwards into the enhanced reaction cylinder. It first enters the edge of the enhanced reaction cylinder, where it is stirred by several agitators, pushing the new water from the edge towards the center. During the oxidation reaction, the water flows upwards, and the sludge produced by the reaction mainly falls downwards from the middle of the enhanced reaction cylinder (corresponding to the hollow center of the annular oxidant dosing pipe), achieving sludge-water separation. Because there is no direct upward water flow at this point, but rather water mixing caused by the horizontal or oblique stirring of the agitators, the resistance to sludge descent is small, facilitating sludge-water separation. The falling sludge does not affect the inlet water or the dosing of the dosing pipe. The sludge finally falls to the bottom of the combined oxidizer and is discharged through the sludge discharge port. Attached Figure Description

[0045] Figure 1 This is a process flow diagram of the resource utilization and processing method described in Example 1;

[0046] Figure 2 This is a schematic diagram of the Fenton-electro-oxidation coupled oxidation reactor described in Example 2;

[0047] Figure 3 This is a schematic diagram showing the combination of the flow guide plate, the second electrode, and the enhanced reaction cylinder;

[0048] Figure 4 This is a schematic diagram of a separator / stirrer.

[0049] In the attached diagram, 1-stirring plate, 2-separation stirrer, 3-guide plate, 4-first electrode plate, 5-second electrode plate, 6-enhanced reaction cylinder, 7-oxidant dosing pipe, 8-inlet pipe, 9-outlet pipe, 10-aeration pipe, 11-stirring device. Detailed Implementation

[0050] The wastewater treated in the following examples and comparative cases was acidic wastewater from the production of viscose fiber at a factory in Henan Province. The wastewater quality was: SO42- 2- ≥5000mg / L; COD: ≥500mg / L; pH: 1.61; Evaporation residue: ≥3450mg / L; SS: ≥100mg / L.

[0051] Example 1

[0052] This embodiment provides a method for the resource utilization and treatment of acidic wastewater generated during the production of viscose fibers, such as... Figure 1 As shown, it includes the following steps:

[0053] S1: Acidic wastewater is fed into a ceramic membrane ultrafiltration device for ultrafiltration treatment to obtain ultrafiltration permeate;

[0054] S2: The ultrafiltration permeate undergoes primary reverse osmosis treatment to obtain primary reverse osmosis permeate and primary reverse osmosis concentrate;

[0055] S3: The primary reverse osmosis permeate is treated by secondary reverse osmosis to obtain secondary reverse osmosis permeate and secondary reverse osmosis concentrate. The secondary reverse osmosis permeate can be used as recycled water. The secondary reverse osmosis concentrate is mixed with the ultrafiltration permeate and then treated by primary reverse osmosis.

[0056] S4: The concentrated water from the first-stage reverse osmosis undergoes advanced oxidation treatment. The resulting oxidation permeate is then fed into an ion exchange unit to remove divalent or higher cations from the wastewater, yielding ion exchange permeate.

[0057] S5: Ion exchange permeate is fed into the alloy membrane electrodialysis unit for electrodialysis treatment to obtain electrodialysis permeate and electrodialysis desalinated water. The electrodialysis desalinated water is returned to the first-stage reverse osmosis unit for further first-stage reverse osmosis treatment.

[0058] S6: Electrodialysis permeate is fed into a bipolar membrane electrodialysis unit for secondary electrodialysis treatment to obtain sulfuric acid and sodium hydroxide.

[0059] In step S1, the acidic wastewater is first fed into the raw water tank for homogenization and adjustment, and then fed into the ceramic membrane ultrafiltration device for ultrafiltration treatment. The Nanostone CM-151TM ceramic ultrafiltration membrane is used, with a pore size of 0.03 microns, a membrane material of α-type alumina, and a flux of 180 LMH.

[0060] The ultrafiltration permeate is fed into the ultrafiltration permeate tank, which is connected to the first-stage reverse osmosis unit to feed the ultrafiltration permeate into the first-stage reverse osmosis unit.

[0061] The cleaning wastewater from the ceramic membrane ultrafiltration unit is returned to the raw water tank and mixed with the raw water.

[0062] In step S2, the desalination rate of the first-stage reverse osmosis is ≥98%, and the water recovery rate of the first-stage reverse osmosis system is ≥75%.

[0063] The first-stage reverse osmosis unit is connected to the first-stage concentrate tank and the first-stage product water tank, which are used to temporarily store the first-stage reverse osmosis concentrate and the first-stage reverse osmosis product water, respectively. The first-stage product water tank is connected to the inlet of the second-stage reverse osmosis unit, and the first-stage concentrate tank is connected to the inlet of the advanced oxidation unit. After the pH of the first-stage reverse osmosis product water is adjusted to neutral by adding alkali, it is fed into the first-stage product water tank.

[0064] In step S3, the desalination rate of the secondary reverse osmosis system is ≥97%; the water recovery rate of the primary RO system is ≥85%.

[0065] The secondary reverse osmosis concentrate is fed into the ultrafiltration permeate tank, mixed with the ultrafiltration permeate, and then fed into the primary reverse osmosis unit.

[0066] In step S4, ozone is introduced into the advanced oxidation device for oxidation treatment, and the ratio of ozone dosage to COD is 2.5:1.

[0067] The outlet of the advanced oxidation unit is connected to the first intermediate water tank, which is connected to the ion exchange unit; alkali is added to the first intermediate water tank to adjust the pH of the oxidation product water to neutral.

[0068] The ion exchange device is filled with methacrylic acid chelating resin, which reduces the content of divalent cations such as calcium and magnesium to 0.005 mg / L through adsorption, fully meeting the feed water requirements of the bipolar membrane. The chelating resin is regenerated with hydrochloric acid solution, and the waste liquid generated by elution and regeneration is discharged to the sewage treatment plant.

[0069] In step S5, in the alloy membrane electrodialysis device, the water flow velocity is controlled at 5-10 cm / s and the current efficiency is 92%. The salt in the wastewater is transferred to the concentrate side under the action of the electric field to obtain electrodialysis permeate (i.e., concentrated brine) and electrodialysis desalinate water. The electrodialysis desalinate water is returned to the first-stage reverse osmosis device. The electrodialysis permeate is temporarily stored in the second intermediate water tank, which is connected to the bipolar membrane electrodialysis device.

[0070] In step S6, the electrodialysis permeate concentrated by the alloy membrane electrodialysis unit enters the bipolar membrane electrodialysis unit, while pure water is simultaneously input into the bipolar membrane electrodialysis unit for secondary electrodialysis treatment. The bipolar membrane consists of an anion exchange resin layer (AL), a cation exchange resin layer (CL), and an intermediate catalyst layer. The desalination energy consumption is 46.9 kWh / ton of water, and recovered sulfuric acid and sodium hydroxide are obtained respectively. The residual liquid of the bipolar membrane electrodialysis unit has a low salt content and is returned to the alloy membrane electrodialysis unit to continue participating in electrodialysis treatment.

[0071] The water quality after treatment in this embodiment is as follows: conductivity ≤ 5 μs / cm; COD ≤ 5 mg / L; pH: 6-9; SiO2 ≤ 100 μg / L.

[0072] Example 2

[0073] The resource utilization and treatment method for acidic wastewater generated during viscose fiber production provided in this embodiment is the same as that in Embodiment 1, except that the advanced oxidation device uses a Fenton-coupled electro-oxidation oxidation reactor, such as... Figures 2-4 As shown, from the outside in, it includes a first electrode plate 4, a second electrode plate 5, and an enhanced reaction cylinder 6. The first electrode plate 4 and the second electrode plate 5 are electrically connected to the positive and negative terminals of an external power source, respectively, for electro-oxidation treatment. The enhanced reaction cylinder 6 is equipped with a stirring device 11. An oxidant dosing pipe 7 is provided at the bottom of the oxidation reactor and at the position corresponding to the enhanced reaction cylinder 6, for introducing oxidant into the enhanced reaction cylinder 6 to carry out the Fenton reaction.

[0074] The oxidation reactor is cylindrical, and the first electrode plate 4, the second electrode plate 5, the enhanced reaction cylinder 6, and the outer shell of the oxidation reactor are all concentrically arranged; the space between the outer shell and the first electrode plate 4 is the first cavity, the space between the first electrode plate 4 and the second electrode plate 5 is the second cavity, and the space between the second electrode plate 5 and the enhanced reaction cylinder 6 is the third cavity.

[0075] The top of the outer shell is equipped with a water inlet pipe 8, which is used to input wastewater into the first chamber. The wastewater then flows through the second and third chambers in sequence for electro-oxidation treatment. Then the wastewater flows through the inside of the enhanced reaction cylinder 6 for Fenton oxidation treatment.

[0076] The top of the first electrode plate 4 is higher than the liquid level of the first and second cavities, and the bottom is suspended, so that the wastewater in the first cavity flows from top to bottom and then enters the second cavity from the bottom of the first electrode plate 4.

[0077] The top of the second electrode plate 5 is lower than the top of the first electrode plate 4, and the bottom is connected to the bottom surface of the oxidation reactor, so that the wastewater in the second chamber flows from bottom to top and then overflows from the top of the second electrode plate 5 to the third chamber.

[0078] The top of the enhanced reaction cylinder 6 is higher than the liquid level in the third chamber, and the bottom is suspended, so that the wastewater in the third chamber flows from top to bottom and then enters the interior of the enhanced reaction cylinder 6 from the bottom.

[0079] The bottom diameter of the enhanced reaction cylinder 6 is larger than the diameter of its other parts, that is, the bottom is open, which facilitates the entry of wastewater from the third chamber and oxidant from the oxidant dosing pipe 7 into the enhanced reaction cylinder 6.

[0080] The upper part of the enhanced reaction cylinder 6 is provided with a water outlet pipe 9, which is connected to the first intermediate water tank.

[0081] The top of the first electrode plate 4 and the top of the enhanced reaction cylinder 6 are connected to the top surface of the oxidation reactor via a connecting component.

[0082] The bottom surface of the oxidation reactor is provided with an aeration pipe 10 corresponding to the positions of the first and second chambers, which is used to pneumatically agitate the water in the first and second chambers.

[0083] The oxidant dosing pipe 7 is annular, and the diameter of the oxidant dosing pipe 7 is slightly smaller than the diameter of the bottom of the enhanced reaction cylinder 6, so that the hydrogen peroxide input through the oxidant dosing pipe 7 preferentially enters the edge of the enhanced reaction cylinder 6.

[0084] The nozzle of the oxidant dosing pipe 7 is set downward to prevent sludge falling from the enhanced reaction cylinder 6 from clogging the nozzle and affecting the dosing; the oxidant is hydrogen peroxide.

[0085] The bottom of the second electrode plate 5 is provided with a guide plate 3. The guide plate 3 is located below the oxidant dosing pipe 7. The guide plate 3 is a downwardly concave arc plate with the same height on both sides. The outer side is fixed on the side of the second electrode facing the enhanced reaction cylinder 6, and the inner side is suspended.

[0086] The circumference of the guide plate 3 is not less than the circumference of the oxidant dosing pipe 7, so that the water flow guided by the guide plate 3 into the bottom of the enhanced reaction cylinder 6 can cover the dosing area of ​​the oxidant dosing pipe 7 and carry hydrogen peroxide into the edge of the enhanced reaction cylinder 6.

[0087] The edge of the enhanced reaction cylinder 6 is provided with a plurality of stirring devices 11, which are evenly arranged along the circumference of the enhanced reaction cylinder 6 to stir the sewage and hydrogen peroxide rising from the edge of the enhanced reaction cylinder 6.

[0088] The motor of the stirring device 11 is located above the outside of the oxidation reactor, and the stirring shaft extends into the enhanced reaction cylinder 6 to stir the wastewater in the enhanced reaction cylinder 6 and promote the reaction between the wastewater and the oxidant.

[0089] The center of the enhanced reaction cylinder 6 is provided with a separation stirrer 2. The rotating shaft of the separation stirrer 2 passes through the top plate of the oxidation reactor and is connected to the corresponding drive motor. Several stirring parts are evenly arranged on the rotating shaft from top to bottom. The stirring part includes several inclined stirring plates 1. The stirring plates 1 are evenly arranged along the circumference of the rotating shaft. The inner side of the stirring plate 1 is connected to the outer side of the rotating shaft, and the outer side points to the outside of the enhanced reaction cylinder 6. Each stirring plate 1 has an angle of 10-40° with the vertical direction.

[0090] The COD of the water in the first intermediate water tank of Example 1 was 180 mg / L, and the COD of the water in the first intermediate water tank of Example 2 was 50 mg / L. Therefore, the oxidation reactor in this example has a better oxidation effect and can better treat the concentrate produced by the first-stage reverse osmosis.

Claims

1. A method for the resource utilization and treatment of acidic wastewater generated during the production of viscose fiber, characterized in that, Includes the following steps: S1: Acidic wastewater is fed into a ceramic membrane ultrafiltration device for ultrafiltration treatment to obtain ultrafiltration permeate; S2: The ultrafiltration permeate undergoes primary reverse osmosis treatment to obtain primary reverse osmosis permeate and primary reverse osmosis concentrate; S3: The primary reverse osmosis permeate is treated by secondary reverse osmosis to obtain secondary reverse osmosis permeate and secondary reverse osmosis concentrate. The secondary reverse osmosis permeate can be used as recycled water. The secondary reverse osmosis concentrate is mixed with the ultrafiltration permeate and then treated by primary reverse osmosis. S4: The concentrated water from the first-stage reverse osmosis undergoes advanced oxidation treatment. The resulting oxidation permeate is then fed into an ion exchange unit to remove divalent or higher cations from the wastewater, yielding ion exchange permeate. S5: Ion exchange permeate is fed into the alloy membrane electrodialysis unit for electrodialysis treatment to obtain electrodialysis permeate and electrodialysis desalinated water. The electrodialysis desalinated water is returned to the first-stage reverse osmosis unit for further first-stage reverse osmosis treatment. S6: Electrodialysis permeate is fed into a bipolar membrane electrodialysis unit for secondary electrodialysis treatment to obtain sulfuric acid and sodium hydroxide; The advanced oxidation treatment in step S4 is carried out using a Fenton-electro-oxidation coupled oxidation reactor. The Fenton-electro-oxidation coupled oxidation reactor includes, from the outside to the inside, a first electrode plate, a second electrode plate, and an enhanced reaction chamber. The first electrode plate and the second electrode plate are electrically connected to the positive and negative terminals of an external power supply, respectively, to perform electro-oxidation treatment. The enhanced reaction chamber is equipped with a stirring device, and an oxidant dosing pipe is located at the bottom of the oxidation reactor and at the position corresponding to the enhanced reaction chamber, for introducing oxidant into the enhanced reaction chamber to carry out the Fenton reaction. The oxidation reactor is cylindrical, and the first electrode plate, the second electrode plate, the enhanced reaction cylinder, and the outer shell of the oxidation reactor are all concentrically arranged; the space between the outer shell and the first electrode plate is the first cavity, the space between the first electrode plate and the second electrode plate is the second cavity, and the space between the second electrode plate and the enhanced reaction cylinder is the third cavity; The bottom diameter of the enhanced reaction cylinder is larger than the diameter of its other parts. The bottom of the enhanced reaction cylinder is open, which facilitates the entry of wastewater from the third chamber and oxidant from the oxidant dosing pipe into the enhanced reaction cylinder. The oxidant dosing pipe is annular, and its diameter is slightly smaller than the diameter of the bottom of the enhanced reaction cylinder, so that the hydrogen peroxide input through the oxidant dosing pipe preferentially enters the edge of the enhanced reaction cylinder; the nozzle of the oxidant dosing pipe is set downward to avoid sludge falling from the enhanced reaction cylinder from clogging the nozzle and affecting the dosing. The bottom of the second electrode plate is provided with a guide plate. The guide plate is located below the oxidant dosing pipe. The guide plate is a downwardly concave arc plate with the same height on both sides. The outer side is fixed on the side of the second electrode plate facing the enhanced reaction cylinder, and the inner side is suspended. The circumference of the guide plate is not less than the circumference of the oxidant dosing pipe, so that the water flow guided by the guide plate into the bottom of the enhanced reaction cylinder can cover the dosing area of ​​the oxidant dosing pipe and carry hydrogen peroxide into the edge of the enhanced reaction cylinder. The edge of the enhanced reaction cylinder is provided with several stirring devices, which are evenly arranged along the circumference of the enhanced reaction cylinder to stir the sewage and hydrogen peroxide rising from the edge of the enhanced reaction cylinder. The center of the enhanced reaction cylinder is equipped with a separation stirrer. The rotating shaft of the separation stirrer passes through the top plate of the oxidation reactor and is connected to the corresponding drive motor. Several stirring parts are evenly arranged on the rotating shaft from top to bottom. The stirring parts include several inclined stirring plates. The stirring plates are evenly arranged along the circumference of the rotating shaft. The inner side of the stirring plate is connected to the outer side of the rotating shaft, and the outer side points to the outside of the enhanced reaction cylinder.

2. The resource utilization and processing method according to claim 1, characterized in that, In step S1, the acidic wastewater is first fed into the raw water tank for homogenization and adjustment, and then fed into the ceramic membrane ultrafiltration device for ultrafiltration treatment to remove suspended solids and reduce water turbidity. The ultrafiltration permeate is fed into the ultrafiltration permeate tank, which is connected to the first-stage reverse osmosis unit for feeding the ultrafiltration permeate into the first-stage reverse osmosis unit. The cleaning wastewater from the ceramic membrane ultrafiltration unit is returned to the raw water tank and mixed with the raw water to reduce the amount of wastewater discharged.

3. The resource utilization and processing method according to claim 2, characterized in that, In step S2, the first-stage reverse osmosis unit is connected to the first-stage concentrate tank and the first-stage product water tank, which are used to temporarily store the first-stage reverse osmosis concentrate and the first-stage reverse osmosis product water, respectively; the first-stage product water tank is connected to the inlet of the second-stage reverse osmosis unit, and the first-stage concentrate tank is connected to the inlet of the advanced oxidation unit. After adjusting the pH of the primary reverse osmosis permeate to neutral by adding alkali, it is fed into the primary permeate tank.

4. The resource utilization and processing method according to claim 3, characterized in that, In step S3, the secondary reverse osmosis concentrate is input into the ultrafiltration permeate tank, mixed with the ultrafiltration permeate, and then input into the primary reverse osmosis unit, which can improve the permeate production rate and reduce the amount of concentrate discharged.

5. The resource utilization and processing method according to claim 4, characterized in that, In step S4, the outlet of the advanced oxidation unit is connected to the first intermediate water tank, and the first intermediate water tank is connected to the ion exchange unit; alkali is added to the first intermediate water tank to adjust the pH of the oxidation product water to neutral. The ion exchange device is filled with chelating resin to adsorb divalent or higher cations in wastewater, preventing scaling of subsequent equipment. The waste liquid generated from the washing and regeneration of the chelating resin is discharged to the sewage treatment plant.

6. The resource utilization and processing method according to claim 5, characterized in that, In step S5, in the alloy membrane electrodialysis device, the salt in the wastewater is transferred to the concentrate side under the action of the electric field to obtain electrodialysis permeate and electrodialysis desalinated water. The electrodialysis desalinated water is returned to the first-stage reverse osmosis device, and the electrodialysis permeate is temporarily stored in the second intermediate water tank, which is connected to the bipolar membrane electrodialysis device.

7. The resource utilization and processing method according to claim 6, characterized in that, In step S6, the permeate from electrodialysis enters the bipolar membrane electrodialysis unit, and at the same time, pure water is input into the bipolar membrane electrodialysis unit for secondary electrodialysis treatment to obtain recovered sulfuric acid and sodium hydroxide, respectively; the residual liquid of the bipolar membrane electrodialysis unit is returned to the alloy membrane electrodialysis unit.

8. The resource utilization and processing method according to claim 1, characterized in that, The top of the outer shell is provided with a water inlet pipe for inputting wastewater into the first cavity. The wastewater then flows through the second and third cavities in sequence for electro-oxidation treatment. The wastewater then flows through the interior of the enhanced reaction chamber for Fenton oxidation treatment.

9. The resource utilization and processing method according to claim 8, characterized in that, The top of the first electrode plate is higher than the liquid level of the first and second chambers, and the bottom is suspended, so that the wastewater in the first chamber flows from top to bottom and then enters the second chamber from the bottom of the first electrode plate. The top of the second electrode plate is lower than the top of the first electrode plate, and the bottom is connected to the bottom surface of the oxidation reactor, so that the wastewater in the second chamber flows from bottom to top and then overflows from the top of the second electrode plate to the third chamber. The top of the enhanced reaction cylinder is higher than the liquid level in the third chamber, and the bottom is suspended, so that the wastewater in the third chamber flows from top to bottom and then enters the enhanced reaction cylinder from the bottom; the enhanced reaction cylinder is equipped with an outlet pipe at the top.

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