Reverse osmosis and three-dimensional electrocatalysis combined treatment method for perchlorate wastewater

Abstract

The invention relates to a reverse osmosis and three-dimensional electro-catalysis combined treatment method for perchlorate wastewater, which comprises the following steps: carrying out coagulation-flocculation treatment on the perchlorate wastewater, and then standing to separate solid pollutants to obtain pretreated wastewater; the pretreated wastewater is subjected to reverse osmosis membrane treatment, a plurality of reverse osmosis membrane devices are sequentially connected in series, so that the wastewater is subjected to multi-stage reverse osmosis treatment, and fresh water discharged by the last stage of reverse osmosis membrane device is produced water; concentrated water of the next-stage reverse osmosis membrane device returns to the water inlet end of the previous-stage reverse osmosis membrane device; concentrated water produced by the first-stage reverse osmosis membrane device is subjected to three-dimensional electro-catalysis treatment, and perchlorate in the concentrated water is degraded; an anode plate and a cathode plate connected with a power supply are arranged in the electrolytic bath, and a plurality of conductive particles and insulating particles are filled between the anode plate and the cathode plate; water obtained after three-dimensional electro-catalysis treatment is mixed with raw material wastewater, and then coagulation-flocculation treatment is carried out.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater. Background Art

[0002] Perchlorate is a persistent inorganic pollutant with the characteristics of high stability, high migration and diffusion, high water solubility, low adsorption and universal pollution. If perchlorate enters the human body through drinking water or the food chain, it can competitively inhibit the absorption of iodine by the human thyroid gland due to its charge and ion radius being very close to that of iodine ions, thus interfering with the normal function of the thyroid gland.

[0003] At present, the main treatment technologies for perchlorate wastewater include adsorption, ion exchange, chemical reduction, biological method, electrochemical method and membrane separation method. The adsorption method mainly uses adsorption materials such as activated carbon and bentonite to adsorb and remove perchlorate, but there are problems such as limited adsorption capacity, difficulty in adsorbent regeneration and easy secondary pollution. The removal efficiency of the ion exchange method is affected by the stability, exchange capacity, regeneration ability and selectivity of the specific resin, and high-concentration perchlorate waste liquid will be produced during resin regeneration, and perchlorate is not fundamentally removed. The chemical reduction method is mainly based on the electrons provided by zero-valent metal or variable-valent metal ion systems or substances such as H2 to remove ClO4 - Reduction degradation to Cl - , but it requires a higher reaction activation energy, and the precious metal catalysts used are expensive and easily deactivated. The biological method mainly uses microorganisms to reduce and remove perchlorate under anaerobic conditions, but there are problems such as long treatment cycles and harsh operating conditions. The electrochemical method mainly reduces perchlorate in wastewater to chloride ions through an external electric field. The membrane separation method mainly uses external pressure and the selective permeability of the membrane to achieve membrane separation and removal of perchlorate, but it will produce a large amount of highly concentrated perchlorate wastewater, which concentrates the pollutants and does not fundamentally solve the pollution problem. Summary of the invention

[0004] In view of the above problems, the present invention provides a combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater, comprising the following steps: S1: After the pH of the perchlorate wastewater is adjusted, coagulation-flocculation treatment is performed, and then the solid pollutants are separated by standing to obtain pretreated wastewater; S2: The pretreated wastewater is treated with a reverse osmosis membrane. Several reverse osmosis membrane devices are connected in series in sequence, so that the wastewater undergoes multi-stage reverse osmosis treatment, and the fresh water discharged from the last stage of the reverse osmosis membrane device is produced water; The concentrated water from the next-stage reverse osmosis membrane device returns to the water inlet end of the previous-stage reverse osmosis membrane device; S3: The concentrated water of the first-stage reverse osmosis membrane device in step S2 is subjected to three-dimensional electrocatalytic treatment to degrade perchlorate in the concentrated water; The electrolytic cell is provided with an anode plate and a cathode plate connected to a power source, and a plurality of conductive particles and insulating particles are filled between the anode plate and the cathode plate; S4: The water obtained after the three-dimensional electrocatalytic treatment in step S3 is mixed with the raw wastewater and then subjected to coagulation-flocculation treatment.

[0005] Optionally, in step S1, first add alkali to the raw material perchlorate wastewater to adjust the pH value to 8-9; then add coagulant PAC and flocculant PAM, mix them evenly with the wastewater and react; after coagulation and flocculation reaction, let the wastewater stand for separation, solid dirt settles to the bottom, and the clearer water on the top overflows to the filter device, which can further remove solid dirt. After the treatment of step S1, impurities such as suspended solids, bacteria and colloids in the wastewater that are easy to cause reverse osmosis membrane pollution are removed. The filter device can use a filter membrane (pore size 1-5μm) to improve the filtering effect.

[0006] Optionally, in step S2, 1-3 reverse osmosis membrane devices are generally arranged in series, the fresh water outlet of the reverse osmosis membrane device on the upstream side is connected to the water inlet of the reverse osmosis membrane device on the downstream side, and the fresh water outlet of the last reverse osmosis membrane device is connected to the water production pool; The operating pressure of each reverse osmosis membrane device is 1.5-2.5Mpa, and the volume ratio of fresh water to concentrated water in the total effluent of each reverse osmosis membrane device is (2.5-4.5):1.

[0007] Optionally, in step S2, the concentrated water of the next-stage reverse osmosis membrane device returns to the water inlet end of the previous-stage reverse osmosis membrane device. For example, in a three-stage reverse osmosis process, the first, second, and third-stage reverse osmosis membrane devices are connected in sequence, that is, the fresh water outlet of the first-stage reverse osmosis membrane device is connected to the water inlet of the second-stage reverse osmosis membrane device, the fresh water outlet of the second-stage reverse osmosis membrane device is connected to the water inlet of the third-stage reverse osmosis membrane device, the concentrated water outlet of the third-stage reverse osmosis membrane device is connected to the water inlet of the second-stage reverse osmosis membrane device, and the concentrated water outlet of the second-stage reverse osmosis membrane device is connected to the water inlet of the first-stage reverse osmosis membrane device. The concentrated water discharged from the first-stage reverse osmosis membrane device undergoes three-dimensional electrocatalytic treatment.

[0008] Optionally, the anode plate is a lead dioxide electrode plate, and the cathode plate is a stainless steel plate; the conductive particles play a role as a catalyst, and the insulating particles are plastic particles or glass particles.

[0009] Further optionally, the conductive particles and insulating particles are both solid cylindrical, with diameters of 2-5 mm, and the volume ratio of the total volume of the conductive particles to the total volume of the insulating particles in the electrolytic cell is (1-3):1.

[0010] Optionally, in the electrolytic cell, the distance between the anode plate and the cathode plate is 5-10 cm, and the current density is 3-9 mA / cm 2 The electrolysis time is 0.5-2.5h, and the volume ratio of the wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is (1-3):1.

[0011] In step S3, under the action of the electric field, one end of the conductive particle is induced as an anode and the other end is induced as a cathode through electrostatic induction, and the entire conductive particle is induced into an independent microelectrode. A large number of microelectrodes formed in the electrolytic cell are called particle electrodes. Electrochemical reactions can occur on the surface of each particle electrode. Perchlorate directly obtains electrons on the cathode plate and the induced cathode surface of the particle electrode to be reduced and degraded, or highly reducing active substances (active hydrogen [H], etc.) generated during the electrolysis process are used to achieve efficient degradation of perchlorate.

[0012] Preferably, a plurality of conductive particles and a plurality of insulating particles are uniformly arranged horizontally and vertically between the anode plate and the cathode plate. In a horizontal row, the conductive particles and the insulating particles are spaced apart; in a vertical row, the conductive particles and the insulating particles are also spaced apart.

[0013] Further optionally, in any horizontal row or vertical row, the central axes of any two adjacent particles are perpendicular to each other, that is, of any two adjacent particles, one is vertical and the other is horizontal.

[0014] Further optionally, a non-metallic wire is used to penetrate each particle in a horizontal or vertical row of particles, so that each particle is connected into a string; a horizontal support is provided above the liquid level at the top of the electrolytic cell, and the top end of the non-metallic wire is connected to the horizontal support, and the bottom end is connected to the bottom of the electrolytic cell; A non-metallic vertical bracket 1 is provided on the side of the anode plate facing the cathode plate, and the vertical bracket 1 does not contact the anode plate. A non-metallic vertical bracket 2 is provided on the side of the cathode plate facing the anode plate, and the vertical bracket 2 does not contact the cathode plate. The two ends of the horizontal non-metallic wire rope are respectively connected to the vertical bracket 1 and the vertical bracket 2.

[0015] The present invention optimizes the particle electrodes in the traditional electrolytic cell, designs both the conductive particles and the insulating particles into a cylindrical shape, which is simple to manufacture and has a low cost; and optimizes the volume ratio of the two particles, so that the spatial distribution of the two particles is more reasonable, the conductive particles are isolated from each other, the short-circuit current is effectively reduced, the effective repolarization of each particle electrode is achieved, the current efficiency is increased, and the degradation efficiency of perchlorate is greatly improved.

[0016] The above-mentioned staggered particle arrangement of the present invention can further locate the positions of the two particles, and isolate the conductive particles in both the horizontal and vertical directions to avoid the conductive particles from contacting each other and generating short-circuit current. Moreover, the conductive particles and the insulating particles are evenly arranged horizontally and vertically, which greatly improves the uniformity of the particle electrodes in the space between the anode and cathode plates, so that the microelectrodes are evenly distributed and do not drift excessively with the water flow, avoiding the formation of conductive particle accumulation or dilution, and improving the catalytic oxidation efficiency.

[0017] Compared with the traditional dispersed particle electrode, the present invention also provides another particle distribution form, that is, a plurality of spherical particle parts are added into the electrolytic cell, the spherical particle parts include an external hollow shell and a plurality of conductive particles and a plurality of insulating particles inside, the shell is spherical as a whole, including at least two mutually perpendicular solid spherical surfaces, and the spherical surface between two adjacent solid spherical surfaces is vacant, allowing wastewater to enter the shell; Each solid spherical surface is annular, and the inner side of the solid spherical surface is provided with a plurality of support rods evenly distributed in a radial shape, each support rod passes through the center of the shell, and a plurality of conductive particles and insulating particles are arranged on the support rods, stringing the conductive particles and insulating particles into a string.

[0018] Optionally, both ends of the support rod are respectively connected to the inner side surfaces of the corresponding solid spherical surface, and the material of the solid spherical surface and the support rod are both non-metallic, preferably plastic, which is not easy to adsorb pollutants in the wastewater.

[0019] Optionally, on the same support rod, the conductive particles and the insulating particles are arranged at intervals, that is, an insulating particle is arranged between two closest conductive particles, for example, in the order of conductive particles, insulating particles, conductive particles, insulating particles, etc.; Different particles are arranged at the same height on two adjacent solid spherical surfaces and on two corresponding support rods at the same height to prevent conductive particles close to each other at the same height of two adjacent support rods from merging into one microelectrode, that is, at the same height of two adjacent support rods, conductive particles, insulating particles, conductive particles, insulating particles, ..., conductive particles, insulating particles are arranged in sequence on one support rod, and insulating particles, conductive particles, insulating particles, conductive particles, ..., insulating particles, conductive particles are arranged in sequence on the other support rod.

[0020] Further optionally, the conductive particle comprises two shuttle-shaped sections of the same size, the ends of the two sections facing each other are connected to each other to form a connection, the support rod passes through the connection, the central axes of the two sections are on the same straight line, and the support rod is perpendicular to the straight line; Each division is a variable diameter structure, and the diameter gradually decreases from the center to the two ends. The division is shuttle-shaped, with the largest diameter at the center, and the two ends are symmetrically arranged. The two divisions of the conductive particles are integrally formed.

[0021] Further optionally, a plurality of grooves are evenly arranged on the outer surface of the conductive particles, and the grooves protrude into the inside of the conductive particles to increase the specific surface area of ​​the conductive particles and improve the electrolysis effect.

[0022] Preferably, the groove is circular and parallel to the cross section of the conductive particle, and a plurality of circles of grooves are evenly arranged along the central axis of the conductive particle and are equally spaced.

[0023] Preferably, the groove conforms to the central axis of the conductive particle, one end of the groove is located at one end of the conductive particle, the groove spans the maximum diameter of the portion where it is located, and the other end of the groove is located at the connection of the conductive particle.

[0024] The insulating particles are still cylindrical, and the volume ratio of the total volume of the conductive particles to the total volume of the insulating particles in the electrolytic cell is still (1-3):1.

[0025] The conductive particles of the present invention are double shuttle-shaped, and the volume of the two ends of the conductive particles is minimized as much as possible. When two spherical particles approach or collide, the probability of the conductive particles on them contacting each other is minimized. The grooves on the surface of the conductive particles can increase the specific surface area, that is, increase the electrolytic treatment area, which is conducive to the efficient degradation of perchlorate.

[0026] Further optionally, the shell includes more than two solid spherical surfaces, and the plurality of solid spherical surfaces are evenly distributed along the circumference of the shell, which can increase the number of conductive particles and insulating particles.

[0027] Further optionally, the ratio of the diameter of the spherical particle part to the distance between the anode and cathode electrodes is (0.4-0.6):1, and the ratio of the total volume of all conductive particles in the spherical particle part to the total volume of all free conductive particles between the anode and cathode electrodes is 1:(1-1.5).

[0028] Conventional conductive particles and insulating particles are scattered in the electrolytic cell and move with the flow of wastewater. As the flow of water changes, each particle may also experience various conditions, such as sedimentation, accumulation, uneven distribution, etc. In addition, each particle may collide with each other, causing particle wear. In view of this situation, the present invention proposes the above-mentioned spherical shell and double shuttle-shaped conductive particles.

[0029] The non-metallic shell (such as plastic) has good flexibility, and when it contacts or collides with the shell of other spherical particle parts, or when it contacts or collides with other particles, it can avoid collision damage and protect the particles inside the shell. As long as the number of solid spherical surfaces of each shell and the spacing of solid spherical surfaces are reasonably set, when two shells collide with each other, a certain solid spherical surface of one shell cannot enter between two adjacent solid spherical surfaces of another shell, avoiding the solid spherical surface from hitting the particles, and the two shells are plugged together. In addition, as long as the number of solid spherical surfaces of each shell and the spacing of solid spherical surfaces are reasonably set, when free particles approach the shell, the free particles cannot enter between two adjacent solid spherical surfaces of the shell, and will not hit the particles in the shell. The particles in the spherical particle part cooperate with the free particles outside the shell to form a multi-dimensional complex microelectrode environment. Compared with the traditional fully free particle environment, the water treatment effect in the electrolyzer of the present invention is better. The inventor speculates that it may be related to the above-mentioned multi-dimensional complex microelectrode environment, and it is necessary for those skilled in the art to continue to explore and study. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic flow diagram of the combined treatment method described in Example 1; Figure 2 This is a schematic diagram of the arrangement of conductive particles and insulating particles in the electrolytic cell of Example 6; Figure 3 Schematic diagram of the structure of the spherical particle portion of Example 7 (conductive particles and insulating particles are omitted); Figure 4 Schematic diagram of conductive particles and insulating particles on the support rod.

[0031] In the attached drawings, 1-conductive particles, 2-insulating particles, 3-anode plate, 4-cathode plate, 5-electrolytic cell, 6-spherical particle portion, 7-solid spherical surface, 8-support rod, and 9-groove. DETAILED DESCRIPTION

[0032] The water quality of the raw material perchlorate wastewater used in the following examples and comparative examples is as follows: pH value is 8.05, conductivity is 1049 us / cm, and perchlorate concentration is 503 mg / L.

[0033] Example 1 The present embodiment provides a combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater, such as Figure 1 As shown, the following steps are included: S1: After the pH of the perchlorate wastewater is adjusted, coagulation-flocculation treatment is performed, and then the solid pollutants are separated by standing to obtain pretreated wastewater; S2: The pretreated wastewater is treated with a reverse osmosis membrane. Several reverse osmosis membrane devices are connected in series in sequence, so that the wastewater undergoes multi-stage reverse osmosis treatment, and the fresh water discharged from the last stage of the reverse osmosis membrane device is produced water; The concentrated water from the next-stage reverse osmosis membrane device returns to the water inlet end of the previous-stage reverse osmosis membrane device; S3: The concentrated water of the first-stage reverse osmosis membrane device in step S2 is subjected to three-dimensional electrocatalytic treatment to degrade perchlorate in the concentrated water; The electrolytic cell is provided with an anode plate and a cathode plate connected to a power source, and a plurality of conductive particles and insulating particles are filled between the anode plate and the cathode plate; S4: The water obtained after the three-dimensional electrocatalytic treatment in step S3 is mixed with the raw wastewater and then subjected to coagulation-flocculation treatment.

[0034] In step S1, 8L of raw material perchlorate wastewater is firstly added with alkali to adjust the pH value to 8.5; then 8mL of 5wt% PAC solution is added and stirred evenly, and then 4mL of 1wt‰ PAM is added and stirred evenly; after coagulation and flocculation reaction, the wastewater is allowed to stand for separation for 1h, and the solid dirt settles to the bottom, and the relatively clear water on the top overflows to the filter device, which can further remove the solid dirt. Vacuum filtration is used for solid-liquid separation, and the filter membrane pore size of the filter device is 1μm, and the generated solid residue is sent out for disposal.

[0035] In step S2, two reverse osmosis membrane devices are connected in series to process the 8L pretreated wastewater in step S1, the fresh water outlet of the primary reverse osmosis membrane device is connected to the water inlet of the secondary reverse osmosis membrane device, and the fresh water outlet of the secondary reverse osmosis membrane device is connected to the water production pool; The operating pressure of each reverse osmosis membrane device is 2Mpa, and the volume ratio of fresh water to concentrated water in the total effluent of each reverse osmosis membrane device is 3:1. The membrane element of the reverse osmosis membrane device is the AG1812 special anti-pollution composite membrane produced by Suez.

[0036] The primary reverse osmosis membrane device produces 6L of primary fresh water and 2L of primary concentrated water. 6L of primary fresh water is input into the secondary reverse osmosis membrane device, producing 4.5L of secondary fresh water and 1.5L of secondary concentrated water. The secondary fresh water is used as produced water and can be discharged or reused in compliance with standards, and the secondary concentrated water is circulated to the water inlet end of the primary reverse osmosis membrane device; the primary concentrated water enters the electrolytic cell for further treatment. The perchlorate concentration of the secondary fresh water in step S2 is 0.078mg / L, and the perchlorate removal rate is 99.98%.

[0037] The anode plate is a lead dioxide electrode plate, and the anode plate uses the doped modified lead dioxide electrode in patent CN202311587961.2; the cathode plate is a stainless steel plate; the conductive particles play the role of a catalyst, and the conductive particles use the particle electrode in patent CN202310148152.5; the insulating particles are glass particles.

[0038] The conductive particles and insulating particles are both solid cylindrical, and the diameter of both particles is 2 mm. The volume ratio of the total volume of the conductive particles to the total volume of the insulating particles in the electrolytic cell is 1:1. The conductive particles and insulating particles are scattered between the anode and cathode plates and flow and move naturally with the water flow. Magnets are added to the electrolytic cell, and a magnetic stirrer is set under the electrolytic cell to provide stirring for the electrolytic cell.

[0039] The conductive particles are pretreated as follows before use: the conductive particles are washed with deionized water, then soaked with concentrated water produced by the first reverse osmosis membrane device until adsorption saturation, and then the conductive particles are drained for later use to eliminate the influence of the conductive particles on the adsorption of perchlorate during the electrolysis process.

[0040] In step S3, 2L of primary concentrated water is processed in 4 batches, each batch is 500mL. The size of the electrolytic cell is 12cm×6.8cm×11cm, the size of the cathode and anode plates are both 6.7cm×8.3cm, the distance between the anode plate and the cathode plate is 7cm, and the current density is 3.5mA / cm 2 , the electrolysis time is 2h, the volume ratio of the wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is 1:1. The perchlorate concentration of the electrolytic cell effluent is 290.5mg / L.

[0041] In step S4, 2 L of electrolyzed water from 4 batches are mixed with the raw wastewater and then subjected to coagulation-flocculation treatment.

[0042] Since 1.5L of secondary concentrated water is returned to the water inlet of the reverse osmosis membrane device, and 2L of electrolytic effluent is returned to the front end of the coagulation-flocculation-filtration process, the amount of raw material perchlorate wastewater added in step S1 is 4.5L in the subsequent circulation treatment, so the raw material is 4.5L and the secondary fresh water is also 4.5L, achieving output balance. When the conductivity of the inlet water of the first-stage reverse osmosis membrane device reaches 9100us / cm, in order to ensure the effluent water quality of the secondary fresh water and the service life of the reverse osmosis membrane, the 2L electrolytic effluent is heated and evaporated, and the obtained solid residue is sent out for disposal.

[0043] Comparative Example 1 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this comparative example is the same as that in Example 1, except that the three-dimensional electrocatalytic treatment in step S3 is not performed, and the concentrated water that should be input into the electrolytic cell is directly returned to the coagulation-flocculation process in step S1, which increases the load of step S2.

[0044] Because the primary concentrate is not treated by three-dimensional electrolysis and directly returns to step S1, the perchlorate content in the subsequent primary concentrate will increase. After several runs, the perchlorate content will accumulate and increase the load of the S2 reverse osmosis system, so that after 12 runs, the secondary fresh water will exceed 0.7 mg / L.

[0045] Comparative Example 2 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this comparative example is the same as that in Example 1, except that no conductive particles and insulating particles are provided in the electrolytic cell, the perchlorate concentration of the effluent from the electrolytic cell is 1098 mg / L, and the treatment effect is worse than that in Example 1.

[0046] Example 2 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 1, except that the volume ratio of the total volume of conductive particles to the total volume of insulating particles in the electrolytic cell is 3:1.

[0047] Example 3 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Embodiment 1, except that the volume ratio of the total volume of conductive particles to the total volume of insulating particles in the electrolytic cell is 0.9:1.

[0048] Example 4 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 1, except that the volume ratio of the wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is 3:1.

[0049] Example 5 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 1, except that the volume ratio of the wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is 3.1:1.

[0050] Example 6 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 1, except that: Figure 2 As shown, in the electrolytic cell 5, a plurality of conductive particles 1 and a plurality of insulating particles 2 are evenly arranged in a cross-sectional and longitudinal arrangement between the anode plate 3 and the cathode plate 4. In a horizontal row, the conductive particles and the insulating particles are spaced apart; in a vertical row, the conductive particles and the insulating particles are also spaced apart.

[0051] In any horizontal or vertical row, the central axes of any two adjacent particles are perpendicular to each other, that is, any two adjacent particles, one is vertical and the other is horizontal.

[0052] A non-metallic wire is used to penetrate each particle in a horizontal or vertical row, so that each particle is connected into a string; a horizontal support is provided above the liquid level at the top of the electrolytic cell, and the top end of the non-metallic wire is connected to the horizontal support, and the bottom end is connected to the bottom of the electrolytic cell; A non-metallic vertical bracket 1 is provided on the side of the anode plate facing the cathode plate, and the vertical bracket 1 does not contact the anode plate. A non-metallic vertical bracket 2 is provided on the side of the cathode plate facing the anode plate, and the vertical bracket 2 does not contact the cathode plate. The two ends of the horizontal non-metallic wire rope are respectively connected to the vertical bracket 1 and the vertical bracket 2.

[0053] Example 7 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in embodiment 1, except that a plurality of spherical particles 6 are added into the electrolytic cell, such as Figure 3-Figure 4 As shown, the spherical particle part 6 includes an outer hollow shell and a plurality of conductive particles 1 and a plurality of insulating particles 2 inside. The shell is spherical as a whole and includes two mutually perpendicular solid spherical surfaces 7. The spherical surface between the two adjacent solid spherical surfaces 7 is vacant to allow wastewater to enter the shell. Each solid spherical surface 7 is in a circular shape, and a plurality of support rods 8 evenly distributed in a radial pattern are arranged on the inner side of the solid spherical surface 7. Each support rod 8 passes through the center of the shell, and a plurality of conductive particles 1 and insulating particles 2 are arranged on the support rod 8, stringing the conductive particles and insulating particles into a string.

[0054] The two ends of the support rod 8 are respectively connected to the inner side surfaces of the corresponding solid spherical surface 7. The solid spherical surface and the support rod are both made of non-metallic materials, such as plastic, which is not easy to absorb pollutants in the wastewater.

[0055] On the same support rod 8, the conductive particles and the insulating particles are arranged at intervals, that is, an insulating particle is arranged between two closest conductive particles; On two adjacent solid spherical surfaces 7 and on the corresponding two support rods at the same height, different particles are arranged at the same height to prevent the conductive particles close to each other at the same height of the two adjacent support rods from merging into one microelectrode, that is, at the same height of the two adjacent support rods, conductive particles, insulating particles, conductive particles, insulating particles, ..., conductive particles, insulating particles are arranged in sequence on one support rod, and insulating particles, conductive particles, insulating particles, conductive particles, ..., insulating particles, conductive particles are arranged in sequence on the other support rod.

[0056] The conductive particle comprises two shuttle-shaped sections of the same size, the ends of the two sections facing each other are connected to form a connection, a support rod passes through the connection, the central axes of the two sections are on the same straight line, and the support rod is perpendicular to the straight line; Each division is a variable diameter structure, and the diameter gradually decreases from the center to the two ends. The division is shuttle-shaped, with the largest diameter at the center, and the two ends are symmetrically arranged. The two divisions of the conductive particles are integrally formed.

[0057] A plurality of grooves 9 are evenly arranged on the outer surface of the conductive particles, and the grooves 9 protrude into the inside of the conductive particles to increase the specific surface area of ​​the conductive particles and improve the electrolysis effect.

[0058] The groove is circular and parallel to the cross section of the conductive particle. A plurality of circles of grooves are evenly arranged along the central axis of the conductive particle and are equally spaced.

[0059] The ratio of the diameter of the spherical particle part to the distance between the positive and negative electrodes is 0.4:1, and the ratio of the total volume of the conductive particles in all the spherical particle parts to the total volume of all the free conductive particles between the positive and negative electrodes is 1:1.

[0060] Example 8 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 7, except that the ratio of the diameter of the spherical particle portion to the distance between the anode and cathode electrodes is 0.6:1.

[0061] Example 9 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 7, except that the ratio of the diameter of the spherical particle portion to the distance between the anode and cathode electrodes is 0.61:1.

[0062] Example 10 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 7, except that the ratio of the total volume of the conductive particles in all spherical particle portions to the total volume of all free conductive particles between the anode and cathode electrodes is 1:1.5.

[0063] Embodiment 11 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Example 7, except that the ratio of the total volume of the conductive particles in all spherical particle parts to the total volume of all free conductive particles between the anode and cathode electrodes is 1:1.6.

[0064] Example 12 The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this embodiment is the same as that in Embodiment 7, except that no grooves are provided on the outer surfaces of the conductive particles.

[0065] Table 1 Comparison of perchlorate concentrations in the electrolytic cell effluents of the above embodiments .

[0066] As can be seen from the above table, the combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided by the present invention, the electrolytic cell with three-dimensional microelectrodes can better treat perchlorate pollutants, and the treatment effect can be further improved by setting the parameters of the conductive particles and insulating particles in the electrolytic cell. In particular, the setting form of the two particles provided in Examples 6 and 7 optimizes the structure of the microelectrodes in the electrolytic cell, improves the contact between the microelectrodes and the wastewater, enriches the number of microelectrodes, and is conducive to improving the removal rate of perchlorate.

Claims

1. A combined treatment method for perchlorate wastewater using reverse osmosis and three-dimensional electrocatalysis, characterized in that: include: S1: The perchlorate wastewater is subjected to coagulation-flocculation treatment, and then allowed to stand to separate solid pollutants to obtain pretreated wastewater; S2: The pretreated wastewater is treated with a reverse osmosis membrane. Several reverse osmosis membrane devices are connected in series in sequence, so that the wastewater undergoes multi-stage reverse osmosis treatment, and the fresh water discharged from the last stage of the reverse osmosis membrane device is produced water; The concentrated water from the next-stage reverse osmosis membrane device returns to the water inlet end of the previous-stage reverse osmosis membrane device; S3: The concentrated water of the first-stage reverse osmosis membrane device in step S2 is subjected to three-dimensional electrocatalytic treatment to degrade perchlorate in the concentrated water; The electrolytic cell is provided with an anode plate and a cathode plate connected to a power source, and a plurality of conductive particles and insulating particles are filled between the anode plate and the cathode plate; S4: The water obtained after the three-dimensional electrocatalytic treatment in step S3 is mixed with the raw wastewater and then subjected to coagulation-flocculation treatment.

2. The combined processing method according to claim 1, characterized in that: In step S1, alkali is first added to the raw material perchlorate wastewater to adjust the pH value to 8-9; then a coagulant PAC and a flocculant PAM are added, mixed evenly with the wastewater and reacted; after coagulation and flocculation reaction, the wastewater is allowed to stand for separation, solid impurities settle to the bottom, and the clearer water at the top overflows to the filter device, which can further remove the solid impurities.

3. The combined processing method according to claim 1, characterized in that: In step S2, 1 to 3 reverse osmosis membrane devices are arranged in series, the fresh water outlet of the reverse osmosis membrane device on the upstream side is connected to the water inlet of the reverse osmosis membrane device on the downstream side, and the fresh water outlet of the last reverse osmosis membrane device is connected to the water production pool; The operating pressure of each reverse osmosis membrane device is 1.5-2.5Mpa, and the volume ratio of fresh water to concentrated water in the total effluent of each reverse osmosis membrane device is (2.5-4.5):

1.

4. The combined processing method according to claim 1, characterized in that: The anode plate is a lead dioxide electrode plate, and the cathode plate is a stainless steel plate; the conductive particles play a role of catalyst, and the insulating particles are plastic particles or glass particles.

5. The combined processing method according to claim 4, characterized in that: The conductive particles and insulating particles are both solid cylindrical, and the volume ratio of the total volume of the conductive particles to the total volume of the insulating particles in the electrolytic cell is (1-3):

1.

6. The combined processing method according to claim 5, characterized in that: The current density in the electrolytic cell is 3-9 mA / cm 2 The electrolysis time is 0.5-2.5h, and the volume ratio of the wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is (1-3):

1.

7. The combined processing method according to claim 6, characterized in that: A plurality of conductive particles and a plurality of insulating particles are evenly arranged horizontally and vertically between the anode plate and the cathode plate. In a horizontal row, the conductive particles and the insulating particles are arranged alternately; in a vertical row, the conductive particles and the insulating particles are also arranged alternately. In any horizontal or vertical row, the central axes of any two adjacent particles are perpendicular to each other, and any two adjacent particles, one is vertical and the other is horizontal.

8. The combined processing method according to claim 4, characterized in that: A plurality of spherical particle parts are added into the electrolytic cell, the spherical particle parts include an outer hollow shell and a plurality of conductive particles and a plurality of insulating particles inside, the shell is spherical as a whole, including at least two mutually perpendicular solid spherical surfaces, and the spherical surface between two adjacent solid spherical surfaces is vacant, allowing wastewater to enter the shell; Each solid spherical surface is annular, and the inner side of the solid spherical surface is provided with a plurality of support rods evenly distributed in a radial shape, each support rod passes through the center of the shell, and a plurality of conductive particles and insulating particles are arranged on the support rods, stringing the conductive particles and insulating particles into a string.

9. The combined processing method according to claim 8, characterized in that: On the same support rod, conductive particles and insulating particles are arranged at intervals; on two adjacent solid spherical surfaces and on two corresponding support rods at the same height, different particles are arranged at the same height.

10. The combined processing method according to claim 9, characterized in that: The conductive particle comprises two shuttle-shaped sections of the same size, the ends of the two sections facing each other are connected to form a connection, a support rod passes through the connection, the central axes of the two sections are on the same straight line, and the support rod is perpendicular to the straight line; Each section is a variable diameter structure, with the diameter gradually decreasing from the center to the two ends.

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