A method for resource recovery of potassium perchlorate from industrial wastewater

Abstract

The present invention discloses a method for resource recovery of potassium perchlorate from industrial wastewater, which includes: deeply removing perchlorate in the wastewater by using macroporous strongly basic anion exchange resin, enriching the perchlorate into the ion exchange resin, concentrating the perchlorate anion into the resin desorption solution by a resin regenerant, and precipitating potassium perchlorate to obtain crude potassium perchlorate crystals. The present invention obtains a large amount of crude potassium perchlorate crystals, and then purifies the crude potassium perchlorate crystals through an anti-solvent recrystallization process to obtain fine potassium perchlorate crystals with smaller particle size and higher purity. The particle size of the crude potassium perchlorate crystals of the present invention is greater than 100 microns, and the purity of potassium perchlorate reaches more than 90%; the particle size of the potassium perchlorate crystals after anti-solvent recrystallization is 8 - 45 microns, and the purity can reach more than 99.5%. In addition, the removal rate of perchlorate anion in the fireworks wastewater can reach more than 95%, the removal rate of sulfate radical reaches more than 99%, and the removal rate of COD reaches more than 60%.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a method for resource recovery of potassium perchlorate in industrial wastewater. Background Art

[0002] Perchlorate (ClO4 - ) is one of the main persistent pollutants in the environment and widely exists in surface water, groundwater and soil. Perchlorate is mainly used as a solid oxidant in fireworks, firecrackers, fuses, etc., resulting in high concentrations of perchlorate in the wastewater from fireworks and firecrackers. As an endocrine disruptor, when perchlorate enters the human body, it will interfere with the utilization of iodine by the thyroid gland, thereby reducing the synthesis of thyroid hormones t3 and t4, seriously threatening human health.

[0003] Perchlorate in the wastewater from fireworks and firecrackers has characteristics such as non-volatility, high solubility and kinetic stability, and the concentration is extremely high. Since conventional water treatment processes such as coagulation, sedimentation and filtration are difficult to remove perchlorate ions in the wastewater, the concentration of perchlorate in the wastewater gradually increases during the recycling process, even reaching hundreds of milligrams per liter, posing a great ecological risk. The ion exchange method for removing perchlorate does not require the addition of other substances, and high flow rates can be used during operation. The equipment is miniaturized, with the advantages of simple operation, large adsorption capacity, short contact time and small floor area, and has good removal effects on perchlorates with different concentrations. However, the ion exchange method can transfer perchlorate in the wastewater from fireworks and firecrackers to the resin, but does not achieve the degradation of perchlorate ions. After the saturated ion exchange resin is desorbed and regenerated by the desorbent, the desorption liquid is highly concentrated with perchlorate, objectively creating conditions for the resource recovery of potassium perchlorate in the desorption liquid.

[0004] So far, there has been little research on the advanced treatment of high-concentration perchlorate in the wastewater from fireworks and firecrackers. The treatment of the concentrated perchlorate in the desorption liquid has limitations, and the recovery method of potassium perchlorate therein has not been reported. Summary of the Invention

[0005] Object of the Invention: Aiming at the problems existing in the prior art, the present invention provides a method for resource recovery of potassium perchlorate in industrial wastewater. This method realizes the recovery and even resource utilization of potassium perchlorate while purifying industrial wastewater, especially the wastewater from fireworks and firecrackers, can fundamentally solve the pollution problem caused by potassium perchlorate, achieve double benefits of environment and economy, and effectively solve the problem that potassium perchlorate in wastewater cannot be resourcefully recovered. In particular, the problems related to the purification and directional regulation of potassium perchlorate are solved.

[0006] Technical solution: To achieve the above object, a method for the resource recovery of potassium perchlorate from industrial wastewater according to the present invention includes the following steps: deeply removing potassium perchlorate in the fireworks wastewater by using macroporous strongly basic anion exchange resin, enriching potassium perchlorate into the ion exchange resin, further concentrating perchlorate ions into the resin desorption liquid by using a resin regenerant, and precipitating potassium perchlorate to obtain crude potassium perchlorate crystals due to supersaturation.

[0007] Among them, the macroporous strongly basic ion exchange resin skeleton can be styrene-based or acrylic-based.

[0008] Among them, the macroporous strongly basic ion exchange resin skeleton is an acrylic-based skeleton, the resin crosslinking degree is less than 10%, and the resin water content is greater than 40%.

[0009] Among them, the resin regenerant is a KCl solution, the solution concentration is 10-20 wt%, the desorption temperature is 60-95 °C, the dosage of the resin regenerant is 2-10 times the volume of the resin. After the regenerant regenerates the resin to form a desorption liquid (i.e., the KCl solution after desorption is completed) and the temperature is cooled to room temperature, potassium perchlorate precipitates due to supersaturation to obtain crude potassium perchlorate crystals.

[0010] Among them, the desorption liquid in which potassium perchlorate precipitates due to supersaturation is reheated to 60-95 °C, and can be used as a regenerant to repeat the thermal desorption of the perchlorate ion-enriched ion exchange resin and cooled to room temperature. In this process, crude potassium perchlorate crystals can be continuously precipitated.

[0011] Among them, after the macroporous strongly basic anion exchange resin undergoes multiple thermal desorptions, if there is no obvious crystallization after the desorption liquid is cooled, it can be considered that the resin desorption is complete, and the resin can be reused to deeply remove potassium perchlorate in the wastewater.

[0012] Among them, the precipitated crude potassium perchlorate crystals are dissolved in water at 45-55 °C to form a saturated potassium perchlorate solution, a poor solvent for potassium perchlorate is added and slowly stirred to make potassium perchlorate precipitate due to supersaturation to obtain fine crystals. The volume ratio of water, poor solvent and the system is 1:0.05-2, and the poor solution includes one or more of methanol, ethanol, and acetone.

[0013] The method for the resource recovery of potassium perchlorate in the fireworks wastewater according to the present invention specifically includes the following steps:

[0014] (1) After the fireworks wastewater is clarified by sand filtration to remove particulate matter in the wastewater, it is adsorbed by macroporous strongly basic anion exchange resin;

[0015] (2) The macroporous strongly basic anion exchange resin adsorbed to saturation is thermally desorbed and regenerated by using a regenerant, and crude potassium perchlorate crystals precipitate after the desorption liquid is cooled to room temperature;

[0016] (3)The resin desorption liquid for precipitating crude potassium perchlorate crystals can be reused multiple times. After reheating, thermal desorption regeneration can be carried out on the macroporous strongly basic anion exchange resin, and step (2) is repeated;

[0017] (4)During the process of repeating step (3), after the macroporous strongly basic anion exchange resin has been thermally desorbed multiple times, if there is no obvious crystallization after the desorption liquid cools down, it can be considered that the resin desorption is complete and can be reused in step (1);

[0018] (5)The crude potassium perchlorate crystals are poured into water and reheated to dissolve, making it reach a saturated solution state. A poor solvent for potassium perchlorate is added and slowly stirred, and fine potassium perchlorate crystals are gradually precipitated.

[0019] The application of the method for resource recovery of potassium perchlorate in industrial wastewater described in the present invention in the resource recovery of potassium perchlorate in potassium perchlorate wastewater from different sources, especially in firework wastewater containing high concentrations of potassium perchlorate.

[0020] Among them, in the resource recovery of potassium perchlorate in the firework wastewater, the purity of the crude potassium perchlorate crystals directly obtained is over 90%. After anti-solvent recrystallization, the purity of the fine potassium perchlorate crystals can reach over 99.5%. The particle size of the directly crystallized crude potassium perchlorate crystals is greater than 100 microns, and the particle size of the potassium perchlorate crystals after anti-solvent recrystallization is 8 - 45 microns. The removal rate of potassium perchlorate can reach over 95%, the removal rate of sulfate radicals reaches 99% or more, and the COD removal rate reaches 60% or more.

[0021] The present invention realizes for the first time the resource recovery of potassium perchlorate in firework wastewater. The present invention recovers high-value potassium perchlorate from the wastewater and further purifies it. Based on some characteristics of potassium perchlorate, that is, its solubility varies greatly at different temperatures, the high-concentration potassium perchlorate solution in the desorption liquid can naturally precipitate after cooling, and further purified by the method described in the present invention, high-value potassium perchlorate crystals can be recovered. At the same time, only high-purity potassium perchlorate can be obtained by recrystallization.

[0022] At present, in addition to containing a relatively high concentration of potassium perchlorate, the wastewater from fireworks also contains high concentrations of impurities such as nitrates, phthalates, and sulfates, resulting in a low efficiency of direct resource recovery of potassium perchlorate in the wastewater. Anion exchange resins exhibit advantages that are difficult to match by other methods in the enrichment and concentration of potassium perchlorate. The solubility of potassium perchlorate varies greatly at different temperatures. By thermal desorption of potassium chloride solution, the perchlorate ions enriched by the anion exchange resin are concentrated into the resin desorption solution. After cooling to room temperature, a large amount of fine potassium perchlorate crystals can precipitate, and the crude potassium perchlorate crystals can be recovered through centrifugation. The desorption solution after crystallizing potassium perchlorate can be reused as a resin regenerant multiple times, greatly reducing the ecological risk of generating high-concentration desorption solution. The crystal size and morphology of potassium perchlorate have important effects on the combustion performance and rheological properties of fireworks propellants. The smaller the particle size, the larger its specific surface area, the faster the thermal decomposition, the closer the diffusion flame is to the combustion surface, and the more conducive it is to heat transfer, thereby increasing the burning rate of solid propellants. According to the difference in the solubility of potassium perchlorate in different solvents, the crude potassium perchlorate crystals are dissolved and then re-precipitated by the anti-solvent recrystallization method, that is, potassium perchlorate reaches supersaturation and precipitates through a non-solvent for potassium perchlorate. Since the anti-solvent recrystallization method has a simple and safe process, does not involve high temperature and high pressure, and has outstanding advantages such as small product particle size, good uniformity, easy scale production, and easy control of particle size and morphology, it creates conditions for recovering ultra-fine potassium perchlorate crystals with controllable particle size and morphology from the resin desorption solution. The present invention simultaneously removes the nitrate and sulfate pollution loads in the fireworks wastewater, and the treated effluent can be reused as workshop cleaning water, realizing the deep removal of potassium perchlorate in the wastewater of the fireworks industry, especially for industrial wastewater containing a high concentration of potassium perchlorate.

[0023] Mechanism: In addition to containing a high concentration of potassium perchlorate, the fireworks wastewater also contains relatively high concentrations of impurities such as nitrates, phthalates, and sulfates. The efficiency of directly recycling potassium perchlorate in the wastewater is relatively low. Ion exchange resins have a high affinity for perchlorate ions, so potassium perchlorate in the fireworks wastewater can be enriched through ion exchange resins, and then the perchlorate ions can be concentrated in the resin desorption solution. The solubility of potassium perchlorate in aqueous solutions at different temperatures varies greatly. By thermally desorbing the ion exchange resin enriched with perchlorate ions using highly concentrated brine, a large amount of crude potassium perchlorate crystals can precipitate out after the desorption solution is cooled. In addition, the present invention purifies potassium perchlorate through an anti-solvent recrystallization process, while improving the crystal particle size and morphology of potassium perchlorate. The smaller the particle size, the larger the specific surface area, which is more conducive to heat transfer, thus increasing the burning rate of solid propellants. During the recrystallization process, the nucleation and growth of potassium perchlorate crystals are highly related to the properties of the anti-solvent. The particle size and morphology of potassium perchlorate crystals can be regulated by optimizing the water / anti-solvent ratio. With the addition of the anti-solvent, potassium perchlorate becomes supersaturated and nucleates and crystallizes. The formation and growth of crystal nuclei lead to a continuous decrease in the concentration of potassium perchlorate in the solution. When the concentration of potassium perchlorate in the solution is lower than the critical nucleation concentration, the crystal growth process is completed. This process can not only improve the purity of potassium perchlorate crystals but also reduce the crystal particle size and increase the crystal specific surface area, thereby optimizing the crystal properties.

[0024] The present invention utilizes the characteristic that the solubility of potassium perchlorate varies greatly at different temperatures. By thermally desorbing with a potassium chloride solution, the perchlorate ions enriched by the anion exchange resin are concentrated in the resin desorption solution. After cooling to room temperature, a large amount of crude potassium perchlorate crystals can precipitate out. Then, the crude potassium perchlorate crystals are purified through an anti-solvent recrystallization process to obtain fine potassium perchlorate crystals with a smaller particle size and higher purity. The potassium chloride desorption solution after crystallizing potassium perchlorate can be reused as a resin regenerant multiple times, greatly reducing the ecological risk of generating highly concentrated desorption solutions. The particle size of the crude potassium perchlorate crystals described in the present invention is greater than 100 microns, and the purity of potassium perchlorate reaches over 90%. The particle size of the potassium perchlorate crystals after anti-solvent recrystallization is 8 - 45 microns, and the purity can reach over 99.5%. In addition, the removal rate of potassium perchlorate in the fireworks wastewater can reach over 95%, the removal rate of sulfate ions can reach over 99%, and the COD removal rate can reach over 60%.

[0025] The present invention has realized the recycling, purification and directional crystallization of potassium perchlorate in wastewater for the first time through a specific method. In addition to containing a high concentration of potassium perchlorate, the fireworks wastewater also contains relatively high concentrations of impurities such as nitrates, phthalates, and sulfates. The efficiency of directly recycling potassium perchlorate in the wastewater is relatively low. The solubility of potassium perchlorate in aqueous solutions at different temperatures varies greatly. In the present invention, a concentrated brine (KCl) with a specific concentration is used for thermal desorption of the ion exchange resin enriched with perchlorate ions. A large amount of crude potassium perchlorate crystals can be precipitated after the desorption solution is cooled. Furthermore, by controlling the recrystallization process, potassium perchlorate with high recovery rate, high purity and high added value can be obtained. The KCl solution with a specific concentration can not only be used as a regenerant for thermal desorption multiple times, but also the specific concentration and thermal desorption temperature are very important, effectively ensuring the recovery purity of potassium perchlorate. The method of the present invention has high desorption performance and is conducive to the resource recycling of potassium perchlorate.

[0026] The higher the purity of potassium perchlorate recovered by the method of the present invention, the wider the range of its utilization. The present invention recovers potassium perchlorate from wastewater for the first time, realizing the resource utilization of pollutants while purifying sewage; the present invention effectively improves the purity of potassium perchlorate by using anti-solvent recrystallization; the present invention improves the desorption efficiency of the resin by using a heating method, and at the same time increases the solubility of potassium perchlorate by utilizing the solubility difference of potassium perchlorate, so that it precipitates supersaturated at room temperature.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention provides a method for resource recycling of potassium perchlorate in industrial wastewater. The operation of the present invention is simple and environmentally friendly. The purity of the recovered potassium perchlorate reaches more than 99.5%. In addition, the removal rate of potassium perchlorate in the wastewater can reach more than 95%, the removal rate of sulfate radicals can reach more than 99%, and the COD removal rate can reach more than 60%. The treated effluent can be reused as workshop cleaning water.

[0029] 2. The prior art mainly focuses on the deep removal of potassium perchlorate in wastewater and rarely considers the recycling of potassium perchlorate in wastewater. The present invention realizes the recovery and even resource utilization of potassium perchlorate while purifying wastewater, which can fundamentally solve the pollution problem caused by potassium perchlorate and achieve double benefits of environment and economy.

[0030] 3. The method for resource recycling of potassium perchlorate in industrial wastewater of the present invention is applicable to various wastewater systems containing potassium perchlorate, especially fireworks wastewater. The resin desorption solution for precipitating crude potassium perchlorate crystals can be used multiple times, and the anion exchange resin can be recycled for thermal desorption regeneration. This process does not increase the amount of resin desorption solution, greatly reducing the ecological risk of the resin desorption solution. Specific embodiments

[0031] The present invention can be better understood according to the following embodiments. Those skilled in the art can easily understand that the content described in the embodiments is only used to illustrate the present invention and should not and will not limit the present invention described in detail in the claims. The materials, reagents, etc. used in the following embodiments can be obtained from commercial sources without special instructions. The experimental methods without specific conditions noted in the embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0032] In the examples, the macroporous strongly basic ion exchange resin is D213 anion exchange resin produced by Jiangsu Jinkai Resin Factory, or IRA958 anion exchange resin of Purolite Company, or D730 anion exchange resin of Zhejiang Zhengguang Resin Industry Co., Ltd., all of which are acrylic-based skeletons, the resin cross-linking degree is less than 10%, and the resin water content is greater than 50%.

[0033] Example 1

[0034] A method for resource recovery of potassium perchlorate from fireworks wastewater, and the raw water used is the wastewater in the sedimentation tank of a certain fireworks enterprise. The concentration of perchlorate ion in the wastewater is 120 mg / L, the concentration of sulfate ion is 15 mg / L, and the COD concentration is 55 mg / L.

[0035] The specific treatment steps are as follows:

[0036] (1) After the fireworks wastewater is clarified by sand filtration to remove the particulate matter in the wastewater, it is adsorbed by D213 anion exchange resin produced by Jiangsu Jinkai Resin Factory;

[0037] (2) The anion exchange resin adsorbed to saturation is thermally desorbed and regenerated with KCl solution. The KCl concentration is 10 wt%, the desorption temperature is 80 °C, the volume of the KCl solution is 5 times the volume of the resin. After the thermally desorbed and regenerated desorption liquid is cooled to room temperature, crude potassium perchlorate crystals are precipitated;

[0038] (3) The resin desorption liquid with precipitated crude potassium perchlorate crystals can be used multiple times. Heating it to 80 °C again can thermally desorb and regenerate the anion exchange resin, and repeat step (2);

[0039] (4) Repeating the process of step (3), after the ion exchange resin is thermally desorbed 4 times, there is no obvious crystallization after the desorption liquid is cooled, and it can be considered that the resin desorption is complete and can be reused in process (1);

[0040] (5) The crude potassium perchlorate crystals are poured into water and reheated to 55 °C to dissolve until it reaches a saturated solution state. A poor solvent for potassium perchlorate is added and slowly stirred, and fine potassium perchlorate crystals are gradually precipitated. The poor solvent used is methanol, and the volume ratio of water / methanol in the system after adding is 1:0.5.

[0041] The crude potassium perchlorate directly obtained in this example has a purity of 95.4%. After anti-solvent recrystallization, the fine crystals of potassium perchlorate can reach a purity of 99.6%. The particle size of the directly crystallized crude crystals is greater than 100 microns, and the average particle size of the potassium perchlorate crystals after anti-solvent recrystallization is 34 microns. In addition, the removal rate of perchlorate in the fireworks wastewater can reach more than 95%, the removal rate of sulfate can reach more than 99%, and the removal rate of COD can reach more than 60%.

[0042] Example 2

[0043] A method for resource recovery of potassium perchlorate from fireworks wastewater, where the raw water used is the wastewater in the sedimentation tank of a certain fireworks enterprise. The concentration of perchlorate in the wastewater is 120 mg / L, the concentration of sulfate is 15 mg / L, and the concentration of COD is 55 mg / L.

[0044] The specific treatment steps are as follows:

[0045] (1) After the fireworks wastewater is clarified by sand filtration to remove the particulate matter in the wastewater, it is subjected to adsorption treatment with the IRA958 anion exchange resin of Purolite Company;

[0046] (2) The anion exchange resin adsorbed to saturation is regenerated by thermal desorption using a KCl solution. The KCl concentration is 20 wt%, the desorption temperature is 60 °C, the volume of the KCl solution is 2 times the volume of the resin. After the thermal desorption regeneration forms the desorbed solution and cools to room temperature, crude potassium perchlorate crystals precipitate;

[0047] (3) The resin desorbed solution containing the precipitated crude potassium perchlorate crystals can be used multiple times. Heating it to 60 °C again can perform thermal desorption regeneration on the anion exchange resin. Repeat step (2);

[0048] (4) Repeating the process of step (3), after the ion exchange resin is thermally desorbed 4 times, and there is no obvious crystallization after the desorbed solution cools, it can be considered that the resin desorption is complete and can be reused in process (1);

[0049] (5) Pour the crude potassium perchlorate crystals into water, reheat to 45 °C and dissolve them to make a saturated solution state. Add a poor solvent for potassium perchlorate and stir slowly. Fine potassium perchlorate crystals gradually precipitate. The poor solvent used is ethanol, and the volume ratio of water / ethanol in the system after adding is 1:0.05.

[0050] The crude potassium perchlorate directly obtained in this example has a purity of 93.5%. After anti-solvent recrystallization, the fine crystals of potassium perchlorate can reach a purity of 99.5%. The particle size of the directly crystallized crude crystals is greater than 100 microns, and the average particle size of the potassium perchlorate crystals after anti-solvent recrystallization is 30 microns. In addition, the removal rate of perchlorate in the fireworks wastewater can reach more than 95%, the removal rate of sulfate can reach more than 99%, and the removal rate of COD can reach more than 60%.

[0051] Example 3

[0052] The method for resource recovery of potassium perchlorate from fireworks wastewater uses the raw water as the wastewater in the sedimentation tank of a certain fireworks enterprise. The concentration of perchlorate ion in the wastewater is 120 mg / L, the concentration of sulfate ion is 15 mg / L, and the COD concentration is 55 mg / L.

[0053] The specific treatment steps are as follows:

[0054] (1) After the fireworks wastewater is clarified by sand filtration to remove the particulate matter in the wastewater, it is adsorbed by the D730 anion exchange resin of Zhejiang Zhengguang Resin Industry Co., Ltd.

[0055] (2) The anion exchange resin adsorbed to saturation is regenerated by thermal desorption using a KCl solution. The KCl concentration is 15 wt%, the desorption temperature is 95 °C, the volume of the KCl solution is 10 times the volume of the resin. After the hot desorption regeneration forms the desorption liquid and cools to room temperature, crude potassium perchlorate crystals precipitate.

[0056] (3) The resin desorption liquid from which the crude potassium perchlorate crystals precipitate can be used multiple times. By heating it to 95 °C again, the anion exchange resin can be regenerated by thermal desorption, and step (2) is repeated.

[0057] (4) During the process of repeating step (3), after the ion exchange resin is thermally desorbed 4 times, when there is no obvious crystallization after the desorption liquid cools, it can be considered that the resin desorption is complete and can be reused in process (1).

[0058] (5) The crude potassium perchlorate crystals are poured into water and reheated to 55 °C to dissolve until it reaches a saturated solution state. An antisolvent of potassium perchlorate is added and slowly stirred, and fine potassium perchlorate crystals gradually precipitate. The antisolvent used is acetone, and the volume ratio of water / antisolvent in the system after addition is 1:2.

[0059] The purity of the crude potassium perchlorate directly obtained in this example reaches 94.8%. The fine potassium perchlorate crystals after antisolvent recrystallization can reach a purity of 99.5%. The particle size of the directly crystallized crude crystals is greater than 100 microns, and the average particle size of the potassium perchlorate crystals after antisolvent recrystallization is 32 microns. In addition, the removal rate of perchlorate ion in the fireworks wastewater can reach more than 95%, the removal rate of sulfate ion reaches more than 99%, and the COD removal rate reaches more than 60%.

[0060] Comparative Example 1

[0061] In Comparative Example 1, the method in Example 1 is adopted, and the KCl solution is replaced with a potassium sulfate or potassium nitrate solution of the same concentration, and the recovery of potassium perchlorate cannot be achieved.

[0062] Comparative Example 2

[0063] In Comparative Example 2, the method in Example 1 was adopted, and the KCl solution was replaced with a KCl solution with a concentration of 25 wt%. The purity of the crude potassium perchlorate directly obtained was 85.4%. After anti-solvent recrystallization, the purity of the fine potassium perchlorate crystals could reach 90.7%. In addition, the removal rate of perchlorate in the fireworks wastewater could reach over 95%, the removal rate of sulfate could reach over 99%, and the COD removal rate could reach over 60%.

[0064] In this example, it was found that during the recovery process, when the concentration of the KCl solution was too high, although the removal rates of perchlorate and others were still very high, it would significantly affect the purity of the recovered potassium perchlorate.

[0065] Comparative Example 3

[0066] In Comparative Example 3, the method in Example 1 was adopted, and the KCl solution was replaced with a KCl solution with a concentration of 5 wt%. The purity of the crude potassium perchlorate directly obtained in this example was 80.6%. After anti-solvent recrystallization, the purity of the fine potassium perchlorate crystals could reach 85.3%. In addition, the removal rate of perchlorate in the fireworks wastewater could reach over 90%, the removal rate of sulfate could reach over 95%, and the COD removal rate could reach over 60%. In this example, it was found that during the recovery process, when the concentration of the KCl solution was low, the removal rates of perchlorate and others decreased slightly, and it would also significantly affect the purity of the recovered potassium perchlorate.

[0067] It can be seen from Comparative Examples 2 and 3 that too high or too low concentration of the KCl solution will significantly affect the purity of the recovered potassium perchlorate, and its concentration is very important during the recovery process. The low-concentration KCl solution not only reduces the desorption efficiency of perchlorate, but also significantly reduces the recovery purity of potassium perchlorate; although the removal rates of perchlorate and others are still very high for too high concentration of KCl, it will also significantly affect the purity of the recovered potassium perchlorate.

[0068] Comparative Example 4

[0069] In Comparative Example 4, the method in Example 1 was adopted, and the desorption temperature was room temperature. The purity of the crude potassium perchlorate directly obtained was 78.2%. After anti-solvent recrystallization, the purity of the fine potassium perchlorate crystals could reach 84.6%. In addition, the removal rate of perchlorate in the fireworks wastewater could reach over 80%, the removal rate of sulfate could reach over 80%, and the COD removal rate could reach over 50%.

[0070] In this comparative example, it was found that during the recovery process, when the desorption temperature was low, not only the removal rates of perchlorate and others would decrease significantly, but also it would significantly affect the purity of the recovered potassium perchlorate. At the same time, if the desorption temperature is too high, exceeding 100 °C, it will cause certain damage to the resin structure and performance, and the resin functional groups are prone to oxidation. In addition, under high-temperature conditions, the perchlorate structure is unstable and may react with the container to cause corrosion.

Claims

1. A method for resource recovery of potassium perchlorate from industrial wastewater, characterized in that, It includes the following steps: deeply removing potassium perchlorate in wastewater by using macroporous strongly basic anion exchange resin, enriching potassium perchlorate in the ion exchange resin, further concentrating perchlorate ions into the resin desorption solution by a resin regenerant, and precipitating potassium perchlorate to obtain crude potassium perchlorate crystals due to supersaturation; The resin regenerant is a KCl solution with a solution concentration of 10-20 wt%, a desorption temperature of 60-95 °C, and the dosage of the resin regenerant is 2-10 times the volume of the resin. After the regenerant regenerates the resin and the temperature of the formed desorption solution is cooled to room temperature, crude potassium perchlorate crystals precipitate due to supersaturation of potassium perchlorate; The method specifically includes the following steps: (1) After the industrial wastewater is clarified by sand filtration to remove particulate matters in the wastewater, it is subjected to adsorption treatment by macroporous strongly basic anion exchange resin; (2) The macroporous strongly basic anion exchange resin adsorbed to saturation is thermally desorbed and regenerated by a regenerant, and crude potassium perchlorate crystals precipitate after the formed desorption solution is cooled to room temperature; (3) The resin desorption solution from which crude potassium perchlorate crystals precipitate can be used multiple times. After being reheated, it can be used as a regenerant to thermally desorb the macroporous strongly basic anion exchange resin, and step (2) is repeated; (4) In the process of repeating step (3), after the macroporous strongly basic anion exchange resin is thermally desorbed multiple times, if there is no obvious crystallization after the desorption solution is cooled, it can be considered that the resin desorption is complete, and it can be reused for step (1); (5) The crude potassium perchlorate crystals are poured into water, reheated and dissolved to make it reach a saturated solution state, a poor solvent for potassium perchlorate is added and slowly stirred, and fine potassium perchlorate crystals gradually precipitate.

2. The method for resource recovery of potassium perchlorate from industrial wastewater according to claim 1, wherein The macroporous strongly basic ion exchange resin skeleton is styrene-based or acrylic-based.

3. The method for resource recovery of potassium perchlorate from industrial wastewater according to claim 1, wherein The macroporous strongly basic ion exchange resin skeleton is an acrylic-based skeleton, the resin crosslinking degree is less than 10%, and the resin water content is greater than 50%.

4. The method for resource recovery of potassium perchlorate from industrial wastewater according to claim 1, characterized in that, The desorption solution from which potassium perchlorate precipitates due to supersaturation is reheated to 60-95 °C, and can be used as a resin regenerant to repeatedly perform thermal desorption of the perchlorate ion-enriched ion exchange resin and cooled to room temperature, and crude potassium perchlorate crystals can continuously precipitate during this process.

5. The method for resource recovery of potassium perchlorate in industrial wastewater according to claim 1, wherein, After the macroporous strongly basic anion exchange resin is thermally desorbed multiple times, if there is no obvious crystallization after the desorption solution is cooled, it can be considered that the resin desorption is complete, and the resin can be reused to deeply remove perchlorates in wastewater.

6. The method for resource recovery of potassium perchlorate from industrial wastewater according to claim 1, characterized in that, The precipitated crude perchlorate crystals are dissolved in water at 45-55 °C to form a saturated potassium perchlorate solution, a poor solvent for potassium perchlorate is added and slowly stirred to make potassium perchlorate supersaturated and precipitate fine crystals. The volume ratio of water to the poor solvent in the system is 1:0.05-2, and the poor solvent includes one or more of methanol, ethanol, and acetone.

7. Application of the method for resource recovery of potassium perchlorate in industrial wastewater according to claim 1 in the resource recovery of potassium perchlorate in fireworks wastewater.

8. The application according to claim 7, characterized in that, The purity of the crude potassium perchlorate directly obtained in the resource recovery of potassium perchlorate from fireworks wastewater is over 90%. After anti-solvent recrystallization, the fine crystals of potassium perchlorate can reach a purity of over 99.5%. The particle size of the directly crystallized crude potassium perchlorate crystals is greater than 100 microns, while the particle size of the potassium perchlorate crystals after anti-solvent recrystallization is 8 - 45 microns. The removal rate of perchlorate can reach over 95%, the removal rate of sulfate can reach 99% or more, and the removal rate of COD can reach 60% or more.