Combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater

Abstract

The present invention relates to a combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater, which comprises the following steps: performing coagulation-flocculation treatment on the perchlorate wastewater, and then standing and separating solid pollutants to obtain pretreated wastewater; performing reverse osmosis membrane treatment on the pretreated wastewater, with a plurality of reverse osmosis membrane devices connected in series in sequence, so that the wastewater undergoes multi-stage reverse osmosis treatment, and the fresh water discharged from the last-stage reverse osmosis membrane device is the produced water; the concentrated water of the next-stage reverse osmosis membrane device is returned to the water inlet end of the previous-stage reverse osmosis membrane device; the concentrated water produced by the first-stage reverse osmosis membrane device is subjected to three-dimensional electrocatalysis treatment to degrade perchlorate in the concentrated water; an anode plate and a cathode plate connected to a power supply are arranged in an electrolytic cell, and a plurality of conductive particles and insulating particles are filled between the anode plate and the cathode plate; the water obtained after three-dimensional electrocatalysis treatment is mixed with the raw wastewater, and then coagulation-flocculation treatment is performed again.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly 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 characteristics such as high stability, high migration and diffusion ability, high water solubility, low adsorption property, and universality of pollution. If perchlorate enters the human body through drinking water or the food chain, due to its very close charge and ionic radius to iodide ions, it can competitively inhibit the absorption of iodine by the human thyroid gland and interfere with the normal function of the thyroid gland.

[0003] At present, the treatment technologies for perchlorate wastewater mainly include adsorption method, ion exchange method, chemical reduction method, biological method, electrochemistry 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, difficult regeneration of the adsorbent, and easy generation of secondary pollution. The removal efficiency of the ion exchange method is affected by the stability, exchange capacity, regeneration ability, and selectivity of specific resins, and high-concentration perchlorate wastewater will be generated during resin regeneration, without fundamentally removing perchlorate. The chemical reduction method is mainly based on the electrons provided by zero-valent metals or variable-valent metal ion systems or substances such as H2 to reduce and degrade ClO4 - to Cl - , but it requires a relatively high 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 electrochemistry method mainly reduces perchlorate in wastewater to chloride ions by applying an external electric field. The membrane separation method mainly uses the external pressure and the selective permeability of the membrane to achieve the membrane separation and removal of perchlorate, but it will generate a large amount of highly concentrated perchlorate wastewater, concentrating the pollutants and not fundamentally solving 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, including the following steps:

[0005] S1: After adjusting the pH of the perchlorate wastewater, perform coagulation-flocculation treatment, and then stand and separate solid pollutants to obtain pretreated wastewater;

[0006] S2: Perform reverse osmosis membrane treatment on the pretreated wastewater. Several reverse osmosis membrane devices are connected in series in turn, so that the wastewater undergoes multi-stage reverse osmosis treatment, and the fresh water discharged from the last-stage reverse osmosis membrane device is the produced water;

[0007] 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;

[0008] 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;

[0009] An anode plate and a cathode plate connected to a power source are provided in the electrolytic cell, and a number of conductive particles and insulating particles are filled between the anode plate and the cathode plate;

[0010] S4: After the water obtained from the three-dimensional electrocatalytic treatment in step S3 is mixed with the raw wastewater, coagulation-flocculation treatment is carried out.

[0011] Optionally, in step S1, first add alkali to the raw perchlorate wastewater to adjust the pH value to 8-9; then add a coagulant PAC and a flocculant PAM, mix them evenly with the wastewater and react; after the coagulation and flocculation reactions, let the wastewater stand for separation, the solid contaminants settle to the bottom, and the relatively clear water body at the top overflows to the filtration device, which can further remove solid contaminants. After the treatment in step S1, impurities such as suspended solids, bacteria, and colloids in the wastewater that are likely to cause reverse osmosis membrane fouling are removed. The filtration device can use a filtration membrane (pore size 1-5μm) to improve the filtration effect.

[0012] Optionally, in step S2, generally 1-3 series-connected reverse osmosis membrane devices are set, the fresh water outlet of the upstream reverse osmosis membrane device is connected to the water inlet of the downstream reverse osmosis membrane device, and the fresh water outlet of the last reverse osmosis membrane device is connected to the product water tank;

[0013] The operating pressure of each reverse osmosis membrane device is 1.5-2.5 Mpa, 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.

[0014] 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, 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, and the concentrated water discharged from the first-stage reverse osmosis membrane device is subjected to three-dimensional electrocatalytic treatment.

[0015] Optionally, the anode plate is a lead dioxide electrode plate, and the cathode plate is a stainless steel plate; the conductive particles play the role of a catalyst, and the insulating particles are plastic particles or glass particles.

[0016] Further optionally, both the conductive particles and the insulating particles are solid cylinders with a diameter of 2-5 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 (1-3):1.

[0017] Further 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 0.5-2.5 h, 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.

[0018] In step S3, under the action of the electric field, one end of the conductive particle is induced to be the anode and the other end is induced to be the cathode through electrostatic induction, and the whole 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 and is reduced and degraded on the surface of the cathode plate and the induced cathode of the particle electrode, or the highly efficient degradation of perchlorate is achieved through the extremely strong reducing active substances (such as active hydrogen [H]) generated during the electrolysis process.

[0019] Preferably, several conductive particles and several insulating particles are arranged horizontally and vertically and uniformly between the anode plate and the cathode plate. In a horizontal row, the conductive particles and the insulating particles are arranged at intervals; in a vertical row, the conductive particles and the insulating particles are also arranged at intervals.

[0020] Further optionally, in any horizontal row or vertical row, the central axes of any two adjacent particles are perpendicular to each other, that is, one of any two adjacent particles is vertical and the other is horizontal.

[0021] Further optionally, the particles in a horizontal row or vertical row are penetrated by a non-metallic wire rope to connect the particles into a string; above the liquid level at the top of the electrolytic cell, there is a horizontal bracket. The top end of the non-metallic wire rope of the vertical row is connected to the horizontal bracket, and the bottom end is connected to the bottom of the electrolytic cell;

[0022] On the side of the anode plate facing the cathode plate, there is a non-metallic vertical bracket 1 that does not contact the anode plate. On the side of the cathode plate facing the anode plate, there is a non-metallic vertical bracket 2 that does not contact the cathode plate; the two ends of the non-metallic wire rope of the horizontal row are respectively connected to the vertical bracket 1 and the vertical bracket 2.

[0023] The present invention optimizes the particle electrodes in the traditional electrolytic cell. Both the conductive particles and the insulating particles are designed as cylindrical shapes, which are simple to manufacture and have a low cost. Moreover, the volume ratio of the two types of particles is optimized, making the spatial distribution of the two types of particles more reasonable, enabling the conductive particles to be isolated from each other, effectively reducing the short-circuit current, achieving the effective repolarization of each particle electrode, increasing the current efficiency, and greatly improving the degradation efficiency of perchlorate.

[0024] The above-mentioned criss-cross particle arrangement form of the present invention can further locate the positions of the two types of particles. In both the horizontal and vertical directions, the conductive particles are separated from each other to avoid the generation of short-circuit current due to the contact of conductive particles. Moreover, the conductive particles and the insulating particles are arranged horizontally and vertically at uniform intervals, greatly improving the uniformity of the particle electrodes in the space between the anode and cathode plates, enabling the microelectrodes to be evenly distributed and not drift excessively with the water flow, avoiding the formation of accumulation or rarefaction of conductive particles, and improving the catalytic oxidation efficiency.

[0025] Compared with the traditional dispersed particle electrodes, the present invention also provides another particle distribution form, that is, several spherical particle parts are added into the electrolytic cell. The spherical particle part includes an outer hollow shell and several conductive particles and several insulating particles inside. The whole shell is spherical, including at least two mutually perpendicular solid spherical surfaces. The spherical surface between two adjacent solid spherical surfaces is vacant, allowing the wastewater to enter the inside of the shell;

[0026] Each solid spherical surface is circular ring-shaped. The inner side surface of the solid spherical surface is provided with several support rods evenly distributed in a radial manner. Each support rod passes through the center of the sphere of the shell. Several conductive particles and insulating particles are arranged on the support rod, stringing the conductive particles and the insulating particles into a string.

[0027] Optionally, both ends of the support rod are respectively connected to the inner side surface of the corresponding solid spherical surface. The materials 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.

[0028] Optionally, on the same support rod, the conductive particles and the insulating particles are arranged at intervals, that is, there is an insulating particle between two closest conductive particles, for example, arranged in the order of conductive particle, insulating particle, conductive particle, insulating particle...

[0029] On two adjacent solid spherical surfaces, and on the corresponding two support rods at the same height, different particles are arranged at the same height position to avoid the combination of conductive particles close to each other at the same height on two adjacent support rods into one microelectrode. That is, on two adjacent support rods at the same height, on one support rod, conductive particles, insulating particles, conductive particles, insulating particles,..., conductive particles, insulating particles are arranged in sequence, and on the other support rod, insulating particles, conductive particles, insulating particles, conductive particles,..., insulating particles, conductive particles are arranged in sequence.

[0030] Further optionally, the conductive particles include two spindle-shaped segments of the same size, with one end of the two segments facing each other connected to form a connection point. The support rod passes through the connection point, and the central axes of the two segments are on the same straight line, and the support rod is perpendicular to this straight line;

[0031] Each segment is a variable-diameter structure, and the diameter gradually decreases from the center to both ends. The segment is spindle-shaped, with the largest diameter at the center, and both ends are symmetrically arranged left and right. The two segments of the conductive particles are integrally formed.

[0032] Further optionally, a number of grooves are uniformly arranged on the outer surface of the conductive particles, and the grooves protrude into the conductive particles to increase the specific surface area of the conductive particles and improve the electrolysis effect.

[0033] Preferably, the grooves are circular and parallel to the cross-section of the conductive particles. A number of turns of grooves are uniformly arranged along the central axis of the conductive particles and are equally spaced.

[0034] Preferably, the grooves conform to the central axis of the conductive particles. One end of the groove is at one end of the conductive particle, the groove crosses the diameter maximum of the segment where it is located, and the other end of the groove is at the connection point of the conductive particle.

[0035] 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.

[0036] The conductive particles of the present invention are double-spindle-shaped, minimizing the volume at both ends of the conductive particles. When two spherical particles approach or collide, the probability of the conductive particles on them coming into contact with each other is minimized. The grooves on the surface of the conductive particles can increase the specific surface area, that is, increase the electrolysis treatment area, which is beneficial to the efficient degradation of perchlorate.

[0037] Further optionally, the housing includes more than two solid spherical surfaces, and a number of solid spherical surfaces are uniformly distributed along the circumference of the housing, which can increase the number of conductive particles and insulating particles.

[0038] Further optionally, the ratio of the diameter of the spherical particle part to the distance between the anode and the cathode is (0.4 - 0.6):1, and 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 the cathode is 1:(1 - 1.5).

[0039] Traditional conductive particles and insulating particles are dispersed in the electrolytic cell and move with the wastewater flow. Various situations may occur with the water flow, and various situations may also occur with each particle, such as sedimentation, accumulation, uneven distribution, etc. In addition, the particles will also collide with each other, causing particle wear. In view of this situation, the present invention proposes the above-mentioned spherical shell and double-spindle conductive particle solutions.

[0040] The non-metallic shell (such as plastic) has good flexibility and can avoid collision damage when contacting or colliding with the outer shells of other spherical particle parts or when contacting or colliding with other particles. At the same time, it protects the particles inside the shell. As long as the number of solid spherical surfaces of each shell and the spacing between the 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 the other shell, avoiding the impact of the solid spherical surface on the particles and the insertion of the two shells together. In addition, as long as the number of solid spherical surfaces of each shell and the spacing between the solid spherical surfaces are reasonably set, when a free particle approaches the shell, the free particle cannot enter between two adjacent solid spherical surfaces of the shell and will not impact the particles inside the shell. The particles inside the spherical particle part and the free particles outside the shell cooperate with each other to form a multi-dimensional and complex microelectrode environment. Compared with the traditional all-free particle environment, the water treatment effect in the electrolytic cell of the present invention is better. The inventor guesses that it may be related to the above-mentioned multi-dimensional and complex microelectrode environment, and it remains to be further explored and studied by those skilled in the art. Description of the Drawings

[0041] Figure 1 It is a schematic flow chart of the combined treatment method described in Example 1;

[0042] Figure 2 It is a schematic diagram of the arrangement of conductive particles and insulating particles in the electrolytic cell of Example 6;

[0043] Figure 3 It is a schematic structural diagram of the spherical particle part of Example 7 (the conductive particles and insulating particles are omitted);

[0044] Figure 4 It is a schematic diagram of conductive particles and insulating particles on the support rod.

[0045] In the drawings, 1 - conductive particle, 2 - insulating particle, 3 - anode plate, 4 - cathode plate, 5 - electrolytic cell, 6 - spherical particle part, 7 - solid spherical surface, 8 - support rod, 9 - groove. Detailed Embodiments

[0046] The water quality of the 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.

[0047] Example 1

[0048] The combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided in this example is as Figure 1 shown, and includes the following steps:

[0049] S1: After adjusting the pH of the perchlorate wastewater, carry out coagulation-flocculation treatment, and then stand still to separate solid pollutants, and the pretreated wastewater is obtained;

[0050] S2: Carry out reverse osmosis membrane treatment on the pretreated wastewater. Several reverse osmosis membrane devices are connected in series in turn, so that the wastewater undergoes multi-stage reverse osmosis treatment, and the fresh water discharged from the last-stage reverse osmosis membrane device is the product water;

[0051] 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;

[0052] S3: Carry out three-dimensional electrocatalysis treatment on the concentrated water of the first-stage reverse osmosis membrane device in step S2 to degrade perchlorate in the concentrated water;

[0053] An anode plate and a cathode plate connected to a power supply are arranged in the electrolytic cell, and a number of conductive particles and insulating particles are filled between the anode plate and the cathode plate;

[0054] S4: After the water obtained from the three-dimensional electrocatalysis treatment in step S3 is mixed with the raw wastewater, carry out coagulation-flocculation treatment again.

[0055] In step S1, first add alkali to 8L of raw perchlorate wastewater to adjust the pH value to 8.5; then add 8mL of 5wt% PAC solution and stir evenly, and then add 4mL of 1wt‰ PAM and stir evenly; after coagulation and flocculation reactions, let the wastewater stand still and separate for 1h, the solid dirt settles to the bottom, and the relatively clear water body at the top overflows to the filtering device, which can further remove solid dirt. Vacuum filtration is used for solid-liquid separation, the pore size of the filter membrane of the filtering device is 1μm, and the generated solid residue is sent out for disposal.

[0056] In step S2, set 2 series-connected reverse osmosis membrane devices to treat the 8L of pretreated wastewater in step S1. 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, and the fresh water outlet of the second-stage reverse osmosis membrane device is connected to the product water tank;

[0057] 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 Company.

[0058] The first - stage reverse osmosis membrane device produces 6 L of first - stage fresh water and 2 L of first - stage concentrated water. The 6 L of first - stage fresh water is input into the second - stage reverse osmosis membrane device, which produces 4.5 L of second - stage fresh water and 1.5 L of second - stage concentrated water. The second - stage fresh water, as the produced water, can meet the discharge standards or be reused, while the second - stage concentrated water is recycled to the inlet end of the first - stage reverse osmosis membrane device; the first - stage concentrated water enters the electrolytic cell for further treatment. The perchlorate concentration of the second - stage fresh water in step S2 is 0.078 mg / L, and the perchlorate removal rate is 99.98%.

[0059] The anode plate is a lead dioxide electrode plate, and the anode plate uses the doped and 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.

[0060] Both the conductive particles and the insulating particles are solid cylinders, with a diameter of 2 mm for both types of particles. The total volume ratio of the conductive particles to the total volume of the insulating particles in the electrolytic cell is 1:1. The conductive particles and the insulating particles are both scattered between the anode and cathode plates and move naturally with the water flow. A magnetic stirrer is added to the electrolytic cell, and a magnetic stirrer is set below the electrolytic cell to provide stirring in the electrolytic cell.

[0061] The following pretreatment is carried out on the conductive particles before use: The conductive particles are washed with deionized water, then soaked in the concentrated water produced by the first reverse osmosis membrane device until adsorption saturation, and then the conductive particles are drained and reserved to eliminate the influence of the adsorption of perchlorate by the conductive particles during the electrolysis process.

[0062] In step S3, the 2 L of first - stage concentrated water is processed in 4 batches, with 500 mL in each batch. The size of the electrolytic cell is 12 cm×6.8 cm×11 cm, the sizes of the anode and cathode plates are both 6.7 cm×8.3 cm, the distance between the anode plate and the cathode plate is 7 cm, the current density is 3.5 mA / cm 2 , the electrolysis time is 2 h, 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 1:1. The perchlorate concentration of the electrolytic cell effluent is 290.5 mg / L.

[0063] In step S4, the 4 batches of a total of 2 L of electrolytic effluent are all mixed with the raw wastewater and then subjected to coagulation - flocculation treatment.

[0064] Since 1.5 L of secondary concentrated water is returned to the water inlet end of the reverse osmosis membrane device and 2 L of electrolyzed effluent is returned to the front end of the coagulation - flocculation - filtration process, in subsequent cyclic treatment, the addition amount of the perchlorate wastewater, which is the raw material in step S1, is 4.5 L each time. In this way, the raw material is 4.5 L and the secondary fresh water is also 4.5 L, achieving an output balance. When the conductivity of the water inlet of the first - stage reverse osmosis membrane device reaches 9100 us / cm, to ensure the effluent quality of the secondary fresh water and the service life of the reverse osmosis membrane, 2 L of electrolyzed effluent is heated to dryness, and the obtained solid residue is sent out for disposal.

[0065] Comparative Example 1

[0066] 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 electrocatalysis treatment in step S3 is not carried out, and the concentrated water that should be input into the electrolytic cell is directly returned to the coagulation - flocculation process in step S1, which will increase the load of step S2.

[0067] Because the primary concentrated water is not treated by three - dimensional electrolysis and is directly returned to step S1, the perchlorate content in the subsequent primary concentrated water will increase. After several runs of treatment, it will accumulate and increase, increasing the load of the S2 reverse osmosis system. After 12 runs of treatment, the secondary fresh water exceeds 0.7 mg / L.

[0068] Comparative Example 2

[0069] 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 conductive particles and insulating particles are not set in the electrolytic cell, and the perchlorate concentration of the electrolytic cell effluent is 1098 mg / L, and the treatment effect is worse than that in Example 1.

[0070] Example 2

[0071] The combined treatment method of reverse osmosis and three - dimensional electrocatalysis for perchlorate wastewater provided in this example 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.

[0072] Example 3

[0073] The combined treatment method of reverse osmosis and three - dimensional electrocatalysis for perchlorate wastewater provided in this example 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 0.9:1.

[0074] Example 4

[0075] 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 wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is 3:1.

[0076] Embodiment 5

[0077] 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 wastewater in the electrolytic cell to the sum of the volumes of the conductive particles and the insulating particles is 3.1:1.

[0078] Embodiment 6

[0079] 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, as Figure 2 shown, in the electrolytic cell 5, a plurality of conductive particles 1 and a plurality of insulating particles 2 are arranged horizontally and vertically in a criss-cross and uniform manner between the anode plate 3 and the cathode plate 4. In a horizontal row, the conductive particles and the insulating particles are arranged at intervals; in a vertical column, the conductive particles and the insulating particles are also arranged at intervals.

[0080] In any horizontal row or vertical column, the central axes of any two adjacent particles are perpendicular to each other, that is, one of any two adjacent particles is vertical and the other is horizontal.

[0081] The particles in a horizontal row or vertical column are penetrated by a non-metallic wire rope through each particle, so as to connect each particle into a string; a horizontal bracket is provided above the liquid level at the top of the electrolytic cell, and the top end of the non-metallic wire rope of the vertical column is connected to the horizontal bracket, and the bottom end is connected to the bottom of the electrolytic cell;

[0082] On the side of the anode plate facing the cathode plate, there is a non-metallic vertical bracket 1 that does not contact the anode plate. On the side of the cathode plate facing the anode plate, there is a non-metallic vertical bracket 2 that does not contact the cathode plate; the two ends of the non-metallic wire rope of the horizontal row are respectively connected to the vertical bracket 1 and the vertical bracket 2.

[0083] Embodiment 7

[0084] 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 number of spherical particle parts 6 are added to the electrolytic cell, as Figures 3 - 4 shown, the spherical particle part 6 includes an outer hollow shell and a number of conductive particles 1 and a number of insulating particles 2 inside. The whole shell is spherical, including two mutually perpendicular solid spherical surfaces 7. The spherical surface between adjacent two solid spherical surfaces 7 is vacant, allowing wastewater to enter the inside of the shell;

[0085] Each solid spherical surface 7 is annular. A number of support rods 8 evenly distributed in a radial pattern are provided on the inner side surface of the solid spherical surface 7. Each support rod 8 passes through the center of the spherical shell. A number of conductive particles 1 and insulating particles 2 are provided on the support rod 8, and the conductive particles and insulating particles are strung together in a series.

[0086] Both ends of the support rod 8 are respectively connected to the inner side surface of the corresponding solid spherical surface 7. The materials of the solid spherical surface and the support rod are both non-metallic, such as plastic, which is not easy to adsorb pollutants in the wastewater.

[0087] On the same support rod 8, the conductive particles and the insulating particles are arranged at intervals, that is, one insulating particle is provided between two closest conductive particles;

[0088] On two adjacent solid spherical surfaces 7, on the corresponding two support rods at the same height, different particles are arranged at the same height position to prevent the conductive particles close to each other at the same height on two adjacent support rods from merging into one microelectrode. That is, on two adjacent support rods at the same height, on one support rod, conductive particles, insulating particles, conductive particles, insulating particles,..., conductive particles, insulating particles are arranged in sequence, and on the other support rod, insulating particles, conductive particles, insulating particles, conductive particles,..., insulating particles, conductive particles are arranged in sequence.

[0089] The conductive particle includes two spindle-shaped parts of the same size. One end of the two parts facing each other is connected to form a connection part. The support rod penetrates through this connection part. The central axes of the two parts are on the same straight line, and the support rod is perpendicular to this straight line;

[0090] Each part is a variable-diameter structure. From the center to both ends, the diameter gradually decreases. The part is spindle-shaped, with the largest diameter at the center, symmetrically arranged at both ends left and right, and the two parts of the conductive particle are integrally formed.

[0091] A number of grooves 9 are evenly provided on the outer surface of the conductive particle. The grooves 9 protrude into the conductive particle to increase the specific surface area of the conductive particle and improve the electrolysis effect.

[0092] The groove is circular and parallel to the cross-section of the conductive particle. A number of circles of grooves are evenly provided along the central axis of the conductive particle and are equally spaced.

[0093] The ratio of the diameter of the spherical particle part to the distance between the anode and the cathode is 0.4:1. The total volume of the conductive particles in all spherical particle parts and the total volume of all free conductive particles between the anode and the cathode have a ratio of 1:1.

[0094] Example 8

[0095] 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 the ratio of the diameter of the spherical particle part to the distance between the anode and cathode is 0.6:1.

[0096] Embodiment 9

[0097] 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 the ratio of the diameter of the spherical particle part to the distance between the anode and cathode is 0.61:1.

[0098] Embodiment 10

[0099] 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 the ratio of the total volume of the conductive particles in all the spherical particle parts to the total volume of all the conductive particles free between the anode and cathode is 1:1.5.

[0100] Embodiment 11

[0101] 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 the ratio of the total volume of the conductive particles in all the spherical particle parts to the total volume of all the conductive particles free between the anode and cathode is 1:1.6.

[0102] Embodiment 12

[0103] 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 surface of the conductive particles.

[0104] Table 1 Comparison of perchlorate concentrations in the effluent of the electrolytic cell in the above embodiments

[0105] 。

[0106] As can be seen from the above table, for the combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater provided by the present invention, the electrolytic cell equipped with three-dimensional microelectrodes can better treat perchlorate pollutants. By setting the parameters of the conductive particles and insulating particles in the electrolytic cell, the treatment effect can be further improved. In particular, the two particle setting forms provided in Embodiment 6 and Embodiment 7 optimize the structure of the microelectrodes in the electrolytic cell, improve the contact between the microelectrodes and the wastewater, enrich the number of microelectrodes, and are conducive to improving the removal rate of perchlorate.

Claims

1. A combined treatment method of reverse osmosis and three-dimensional electrocatalysis for perchlorate wastewater, characterized in that, Including: S1: Coagulate - flocculate the perchlorate wastewater, then let it stand to separate solid pollutants, and obtain the pretreated wastewater; S2: Treat the pretreated wastewater by reverse osmosis membrane. Several reverse osmosis membrane devices are connected in series in turn, so that the wastewater undergoes multi - stage reverse osmosis treatment. The fresh water discharged from the last - stage reverse osmosis membrane device is the product water; The concentrated water of the next - stage reverse osmosis membrane device returns to the 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 treated by three - dimensional electrocatalysis to degrade perchlorate in the concentrated water; An anode plate and a cathode plate connected to a power supply are arranged in the electrolytic cell. Several conductive particles and insulating particles are filled between the anode plate and the cathode plate; After the water obtained from the three - dimensional electrocatalysis treatment in step S3 is mixed with the raw wastewater, coagulation - flocculation treatment is carried out again; Several spherical particle parts are added into the electrolytic cell. The spherical particle part includes a hollow shell on the outside and several conductive particles and several insulating particles inside. The whole shell is spherical, including at least two mutually perpendicular solid spherical surfaces. The spherical surface between two adjacent solid spherical surfaces is vacant, allowing wastewater to enter the inside of the shell; Each solid spherical surface is circular - ring - shaped. Several support rods evenly distributed in a radial pattern are arranged on the inner side surface of the solid spherical surface. Each support rod passes through the center of the sphere of the shell. Several conductive particles and insulating particles are arranged on the support rod, stringing the conductive particles and insulating particles into a string; On the same support rod, the conductive particles and insulating particles are arranged at intervals; on two adjacent solid spherical surfaces, and on the corresponding two support rods at the same height, different particles are arranged at the same - height position.

2. The combined treatment method according to claim 1, wherein In step S1, first add alkali to the raw perchlorate wastewater to adjust the pH value to 8 - 9; then add a coagulant PAC and a flocculant PAM, mix them evenly with the wastewater and react; after the coagulation and flocculation reactions, let the wastewater stand and separate. The solid pollutants settle to the bottom, and the relatively clear water body at the top overflows to the filtering device, which can further remove solid pollutants.

3. The combined treatment method according to claim 1, characterized in that, In step S2, set 2 - 3 reverse osmosis membrane devices connected in series. The fresh - water outlet of the upstream - side reverse osmosis membrane device is connected to the inlet of the downstream - side reverse osmosis membrane device, and the fresh - water outlet of the last reverse osmosis membrane device is connected to the product water tank; The operating pressure of each reverse osmosis membrane device is 1.5 - 2.5 Mpa, 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 treatment 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 the role of a catalyst, and the insulating particles are plastic particles or glass particles.

5. The combined treatment method according to claim 4, characterized in that, Both the conductive particles and the insulating particles are solid cylindrical. 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 treatment method according to claim 5, wherein, The current density in the electrolytic cell is 3 - 9 mA / cm 2 , the electrolysis time is 0.5 - 2.5 h, 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 treatment method according to claim 1, characterized in that The conductive particle includes two spindle - shaped parts of the same size. One end of the two parts facing each other is connected to form a connection part. The support rod passes through the connection part, and the central axes of the two parts are on the same straight line. The support rod is perpendicular to this straight line; Each part is a variable - diameter structure, and the diameter gradually decreases from the center to both ends.

Images