A resource treatment process for phosphorus-containing and aluminum-containing sodium chloride waste salt generated in a process for preparing diethyl methyl phosphite

Abstract

The present technology is based on a waste salt of diethyl methyl phosphite, and fine separation and resource utilization of the waste salt with high salt, rich aluminum, phosphorus and organic matter are carried out to prepare a large amount of water treatment agent and new coating material. The waste salt is subjected to steps of dissolution-oxidation-blown off-filtration-odor removal, organic phosphorus is oxidized and converted into phosphite, and deep dephosphorization and accumulation of phosphite are carried out by adsorption. Calcium and zinc oxides are added to prepare phosphite corrosion-resistant coating. The precipitated aluminum hydroxide is cleaned, dissolved, adsorbed, dephosphorized and oxidized to prepare low-sodium dephosphorized polyaluminum ferric chloride. The collected solution is a low-phosphorus and aluminum-free near-saturated salt solution, which is electrolyzed to prepare water treatment agents such as liquid caustic soda and sodium hypochlorite.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization technology, and relates to a resource utilization process for sodium chloride waste salt containing phosphorus and aluminum generated during the preparation of diethyl methylphosphonate. Background Technology

[0002] Diethyl methylphosphonite is an important chemical intermediate used in the synthesis of the novel, highly effective herbicide glufosinate. Currently, the main methods for preparing diethyl methylphosphonite include the ethanol method, the triethyl phosphite method, and the methyl dichloride method. The latter uses phosphorus trichloride, aluminum trichloride, and chloromethane as raw materials to prepare a ternary complex, which is then directly used to prepare diethyl methylphosphonite. Particularly concerning is the generation of sodium chloride solid slag containing phosphorus and aluminum during the production process using aluminum as a reducing agent, including sodium tetrachloroaluminate. According to relevant regulations, sodium tetrachloroaluminate, as an organic chemical catalyst or a byproduct of the pharmaceutical industry, is classified as hazardous solid waste due to its strong corrosiveness and is classified as Class C solid waste, becoming a major concern in the industry. Therefore, numerous publications have reported on its treatment and resource utilization.

[0003] The patent "A Process for Recovering Sodium Tetrachloroaluminate in the Production of Glufosinate (CN201510697507.1)" describes the preparation of aluminum tripolyphosphate from the waste residue of methyl dichloride production. It utilizes phosphorus and aluminum elements in the waste generated during the methyl dichloride ternary complex method to produce aluminum tripolyphosphate as a byproduct. Using chloromethane, aluminum trichloride, and phosphorus trichloride as raw materials, the resulting complex is reduced under the catalysis of aluminum powder. Phosphoric acid or phosphate is added to the waste after distilling off the methyl dichloride product, and a condensation reaction occurs at a high temperature of 250–450°C. After the reaction, the product is washed, dried, and micronized to obtain aluminum tripolyphosphate. The yield of the byproduct aluminum tripolyphosphate can reach 90%, and the purity can reach 98%.

[0004] Some literature reports the preparation of aluminum hypophosphite from waste residue. Aluminum hypophosphite is a novel flame retardant. Using chloromethane, aluminum trichloride, and phosphorus trichloride as raw materials, the resulting complex is reduced under the catalysis of aluminum powder. The waste after distilling off the product, methyl dichloride, is dissolved in ethanol, filtered, and the filtrate is added to a sodium hypophosphite solution. The mixture is refluxed for 3 hours, cooled, filtered, and the filter cake is dried to obtain the finished aluminum hypophosphite product. The yield of the byproduct aluminum hypophosphite can reach over 80%, and the product purity is over 98%. The process steps are as follows: 1) decomposition and precipitation; 2) solid filtration; 3) cooling and precipitation; 4) reuse; 5) recycling; 6) preparation of polyaluminum chloride. This invention transforms sodium tetrachloroaluminate solid waste into a valuable resource, recycling the aluminum trichloride obtained after its decomposition.

[0005] Li Weiwei et al. proposed a method for the harmless treatment of sodium tetrachloroaluminate. The sodium tetrachloroaluminate crystalline solids are broken down to increase the specific surface area, thereby accelerating the harmless treatment process. Water is added sequentially, controlling the water-to-sodium tetrachloroaluminate ratio to be 1–10:1 by weight, at a temperature of 50–100°C for the reaction: 2NaAlCl4 + H2O → Cl2Al-O-AlCl2 + 2HCl + 2NaCl. The resulting substances are polyaluminum chloride, hydrogen chloride, and sodium chloride. Adding hot water accelerates the reaction, thus speeding up HCl formation and preventing the direct release of HCl into the environment due to bubbling during cold water reactions. Alkali metal hydroxides or sodium bicarbonate are then added to neutralize the HCl, adjusting the pH to 5–10, yielding MXCly (where M represents an alkali metal). The treated harmless substances, such as polyaluminum chloride and MXCly, are transferred to a wastewater sedimentation tank. Utilizing the flocculation properties of polyaluminum chloride, other substances are adsorbed and aggregated through van der Waals forces and electrostatic attraction, forming larger particles and accelerating the sedimentation of other substances in the tank. However, the above treatment did not take into account the fine separation of aluminum, phosphorus and sodium chloride, resulting in a high number of impurities and low quality in the recovered products. It also did not take into account the treatment of products containing organic matter and other odors, and thus could not achieve high-quality reuse and harmless treatment. Summary of the Invention

[0006] This invention addresses the aforementioned problems by providing a resource-based treatment process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate. Based on a type of waste salt produced during the preparation of diethyl methylphosphonate, this invention performs fine separation on the high-salt, aluminum-rich, phosphorus-containing, and organic-laden waste salt, recovering low-sodium, phosphorus-free polyaluminum ferric chloride and near-saturated brine with aluminum content less than 100 ppb. These are then electrolyzed to produce disinfectants and sodium hydroxide. Liquid sodium hydroxide with an effective sodium hypochlorite content greater than 12% and 20%, as well as new materials such as calcium phosphite and zinc phosphite suitable for use as anti-corrosion coatings, can be recycled and utilized resource-based.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A resource recovery process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate includes the following steps:

[0009] Step 1: Dissolve, oxidize, strip, and filter the waste salt with water to remove insoluble matter, odors, and gases for purification; the oxidant oxidizes the entrained organic matter and converts organic phosphorus to phosphorous acid; the solution is neutralized with alkali and then filtered to recover aluminum hydroxide precipitate.

[0010] Step 2: The precipitated aluminum hydroxide is cleaned, dissolved, adsorbed, dephosphorized, and oxidized to prepare low-sodium dephosphorized polyaluminum ferric chloride; calcium oxide and / or zinc oxide are added to the dealuminized salt solution to prepare calcium phosphite or calcium zinc phosphite anti-corrosion coating material; if calcium oxide and zinc oxide are added, their molar ratio is 1:1.

[0011] Step 3: Precipitate the near-saturated salt solution to remove aluminum and phosphite, and then purify it to prepare alkaline solution and sodium hypochlorite water treatment agent.

[0012] Furthermore, the oxidant in step 1 is one or two of ozone, hydrogen peroxide, or sodium hypochlorite.

[0013] Furthermore, when ozone is used as the oxidant in step 1, the outgoing gas undergoes multi-stage purification through adsorption using an activated carbon filter bed. The first stage of the activated carbon bed uses a ternary catalyst supported on vanadium, and is simultaneously rinsed with water. The second stage uses porous carbon to adsorb small organic molecules. Heating can be used to increase the dissolution rate, but the temperature should be controlled below 50°C to reduce water evaporation. The amount of water added is mainly controlled to ensure complete dissolution, but it should be controlled to be above 200 g / L based on the sodium chloride content.

[0014] Furthermore, the insoluble matter obtained after oxidation and dissolution in step 1 is mainly impurities such as silicon doped in the raw materials; the solution is neutralized with alkali to a pH of 6-8, and then filtered to recover the aluminum hydroxide precipitate; the final filtrate mainly contains sodium phosphite and a small amount of aluminum, in addition to sodium chloride.

[0015] Further, the aluminum hydroxide precipitated in step 2 contains sodium chloride and aluminum phosphite. Sodium chloride is washed away with deionized water, and the wash water is recycled for dissolution until the conductivity of the aluminum hydroxide wash water is below 30 μS / cm. Solid aluminum hydroxide is dissolved in hydrochloric acid to control the pH to 3-4. Phosphorus removal is performed by adsorption using aluminum hydroxide prepared from recycled aluminum chloride solution as the adsorbent, and the phosphorus is reduced to below 10 ppm. Ferrous chloride and hydrogen peroxide are added for heating and oxidation to further remove organic matter and phosphite. The total organic matter (TOC) is controlled at 10 ppm. Aluminum or iron is added as needed to polymerize and prepare polyaluminum ferric chloride.

[0016] Furthermore, the dissolution and adsorption dephosphorization requires the backwash solution of the adsorption and dephosphorization column to be returned to the precipitation tank for the preparation of calcium phosphite or calcium zinc phosphite. The backwash solution is a saturated sodium chloride solution. The precipitate is washed with deionized water until the water conductivity is lower than 30 μs / cm and then dried at low temperature to obtain phosphite.

[0017] Furthermore, the filtrate from the recovery of phosphite is required to be close to saturated sodium chloride. Aluminum-based adsorbents are used for phosphorus removal, and the adsorption-elution process is the same as above. Sodium hypochlorite is used for oxidation to remove organic matter, and the TOC is reduced to below 5 ppm. Residual chlorine is removed by stripping, and ion-activated carbon filtration and cation exchange are performed to remove calcium, magnesium and other hardness and aluminum, so as to meet the standards for entering the tank.

[0018] Furthermore, the sodium chloride concentration is above 220 g / L, the brine concentration entering the diaphragm outlet is controlled below 80 g / L, the current is constant at 3-3.7 A, the voltage is between 5.0-10 V, the electrolysis time is 1-5 hours (can be continuous), and the electrode plate is 8.5 cm long, 5.5 cm wide, and has an area of ​​46.75 cm². 2 Electrolysis produces 20% and 12% sodium hypochlorite of liquid sodium hydroxide, and the demineralized water is recycled.

[0019] Furthermore, the aluminum-based adsorbent mainly utilizes aluminum hydroxychloride. During the synthesis process, aluminum chloride purified by this process and sodium carbonate are adjusted to pH 2, and organic acids such as citric acid are added to prepare an adsorbent with a crystalline structure and micron-scale under hydrothermal conditions.

[0020] Furthermore, the electrolytic cell uses a symmetrical ion exchange membrane, which has the characteristics of being homogeneous on both sides and resistant to acids and alkalis.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0022] This process achieves the precise separation and recovery of aluminum and phosphorus from waste residue and sodium chloride from the final filtrate. The resulting products from the treated waste residue are diverse, including polyaluminum chloride, calcium phosphite, zinc phosphite, sodium hypochlorite, and sodium hydroxide. Furthermore, the process includes specific treatment procedures for both gaseous and liquid components, preventing direct discharge and resource waste. The entire process achieves high-quality reuse and harmless treatment. Attached Figure Description

[0023] Figure 1 Process flow diagram of this invention.

[0024] Figure 2 Infrared spectrum of calcium phosphite prepared in Example 1.

[0025] Figure 3 XRD pattern of aluminum-based adsorbent in Example 1.

[0026] Figure 4 SEM image of aluminum-based adsorbent in Example 1.

[0027] Figure 5 Example 1: A diagram showing the homogeneous features of a symmetrical ion exchange membrane on both sides.

[0028] Figure 6 XPS plot of vanadium catalyst in Example 2.

[0029] Figure 7 SEM image of activated carbon in Example 2.

[0030] Figure 8 Infrared spectrum of calcium zinc phosphite prepared in Example 2. Detailed Implementation

[0031] The following discloses some embodiments of the present invention. Those skilled in the art can appropriately modify the process parameters to achieve the desired results based on the content of this document. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of the present invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0032] A resource recovery process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate includes the following steps:

[0033] Step 1: Dissolve, oxidize, strip, and filter the waste salt with water to remove insoluble matter, odors, and gases for purification; the oxidant oxidizes the entrained organic matter and converts organic phosphorus to phosphorous acid; the solution is neutralized with alkali and then filtered to recover aluminum hydroxide precipitate.

[0034] Step 2: The precipitated aluminum hydroxide is cleaned, dissolved, adsorbed, dephosphorized, and oxidized to prepare low-sodium dephosphorized polyaluminum ferric chloride; calcium oxide and / or zinc oxide are added to the dealuminized salt solution to prepare calcium phosphite or calcium zinc phosphite anti-corrosion coating material; if calcium oxide and zinc oxide are added, their molar ratio is 1:1.

[0035] Step 3: Precipitate the near-saturated salt solution to remove aluminum and phosphite, and then purify it to prepare alkaline solution and sodium hypochlorite water treatment agent.

[0036] Furthermore, the oxidant in step 1 is one or two of ozone, hydrogen peroxide, or sodium hypochlorite.

[0037] Furthermore, when ozone is used as the oxidant in step 1, the outgoing gas undergoes multi-stage purification through adsorption using an activated carbon filter bed. The first stage of the activated carbon bed uses a ternary catalyst supported on vanadium, and is simultaneously rinsed with water. The second stage uses porous carbon to adsorb small organic molecules. Heating can be used to increase the dissolution rate, but the temperature should be controlled below 50°C to reduce water evaporation. The amount of water added is mainly controlled to ensure complete dissolution, but it should be controlled to be above 200 g / L based on the sodium chloride content.

[0038] Furthermore, the insoluble matter obtained after oxidation and dissolution in step 1 is mainly impurities such as silicon doped in the raw materials; the solution is neutralized with alkali to a pH of 6-8, and then filtered to recover the aluminum hydroxide precipitate; the final filtrate mainly contains sodium phosphite and a small amount of aluminum, in addition to sodium chloride.

[0039] Further, the aluminum hydroxide precipitated in step 2 contains sodium chloride and aluminum phosphite. Sodium chloride is washed away with deionized water, and the wash water is recycled for dissolution until the conductivity of the aluminum hydroxide wash water is below 30 μS / cm. Solid aluminum hydroxide is dissolved in hydrochloric acid to control the pH to 3-4. Phosphorus removal is performed by adsorption using aluminum hydroxide prepared from recycled aluminum chloride solution as the adsorbent, and the phosphorus is reduced to below 10 ppm. Ferrous chloride and hydrogen peroxide are added for heating and oxidation to further remove organic matter and phosphite. The total organic matter (TOC) is controlled at 10 ppm. Aluminum or iron is added as needed to polymerize and prepare polyaluminum ferric chloride.

[0040] Furthermore, the dissolution and adsorption dephosphorization requires the backwash solution of the adsorption and dephosphorization column to be returned to the precipitation tank for the preparation of calcium phosphite or calcium zinc phosphite. The backwash solution is a saturated sodium chloride solution. The precipitate is washed with deionized water until the water conductivity is lower than 30 μs / cm and then dried at low temperature to obtain phosphite.

[0041] Furthermore, the filtrate from the recovery of phosphite is required to be close to saturated sodium chloride. Aluminum-based adsorbents are used for adsorption and phosphorus removal, with the adsorption-elution process being the same as above. Sodium hypochlorite is used for oxidation to remove organic matter, bringing the TOC to below 5 ppm. Residual chlorine is removed by stripping, and ion-activated carbon filtration and cation exchange are performed to remove calcium, magnesium, and other hardness substances, as well as aluminum, to meet the standards for entering the tank.

[0042] Furthermore, the sodium chloride concentration is above 220 g / L, the brine concentration entering the diaphragm outlet is controlled below 80 g / L, the current is constant at 3-3.7 A, the voltage is between 5.0-10 V, the electrolysis time is 1-5 hours (can be continuous), and the electrode plate is 8.5 cm long, 5.5 cm wide, and has an area of ​​46.75 cm². 2 Electrolysis produces 20% and 12% sodium hypochlorite of liquid sodium hydroxide, and the demineralized water is recycled.

[0043] Furthermore, the aluminum-based adsorbent mainly utilizes aluminum hydroxychloride. During the synthesis process, aluminum chloride purified by this process and sodium carbonate are adjusted to pH 2, and organic acids such as citric acid are added to prepare an adsorbent with a crystalline structure and micron-scale under hydrothermal conditions.

[0044] Furthermore, the electrolytic cell uses a symmetrical ion exchange membrane, which has the characteristics of being homogeneous on both sides and resistant to acids and alkalis.

[0045] Example 1.

[0046] Weigh 20g of waste residue (Al content 10%, P content 7.2%, NaCl content 66.54%), add 25ml of aqueous solution, place in a three-necked flask, add 5ml of hydrogen peroxide as an oxidant, and then introduce 10 mg / L of ozone. The gas is collected by passing through the first-stage activated carbon bed containing vanadium-loaded catalyst, while simultaneously being rinsed with water. The second stage utilizes porous carbon to adsorb small organic molecules. Both stages of adsorption work together to purify the gas. After heating at 40℃ for 1 hour, no odorous gas was released from the three-necked flask.

[0047] The solution was filtered to remove insoluble matter, yielding a supernatant (Al content 12%, P content 6.65%, NaCl content 210 g / L). The pH of the solution was adjusted to 6.6 with 0.1 mol / L sodium hydroxide to completely precipitate aluminum ions. Filtration yielded a phosphorus-containing supernatant (P content 9.1%, NaCl content 218 g / L) and aluminum hydroxide precipitate (Al content 90.4%).

[0048] Adding calcium oxide to the filtrate yields calcium phosphite precipitate, which is then vacuum dried to obtain the final product. Calcium phosphite is identified by infrared spectroscopy. Figure 2 As shown.

[0049] The obtained aluminum hydroxide precipitate was first washed with water, then dissolved in 0.5 mol / L hydrochloric acid at pH=3.8. Iron salt and hydrogen peroxide were added for secondary oxidation to convert phosphorus into phosphate. At the same time, the organic matter content was further controlled at 5 ppm. The solution was filtered (P content 28 mg / L). The small amount of phosphorus in the solution was removed with an adsorbent, and finally polyaluminum ferric chloride (P content 3 mg / L) was obtained.

[0050] The adsorbent packed into the adsorption column is an aluminum-based adsorbent, the basic component of which is aluminum hydroxide (synthesized hydrothermally at 180 degrees Celsius using potassium aluminum sulfate dodecahydrate and urea as raw materials), characterized as follows: Figure 3 and Figure 4 As shown, the backwash solution is a saturated sodium chloride solution.

[0051] The NaCl filtrate was collected, and organic matter was removed by sodium hypochlorite oxidation. The TOC level was 3 ppm. Adsorption dephosphorization was performed using the same method as above, followed by deep dechlorination and removal of other calcium and magnesium cations via ion exchange. After purification, a sodium chloride solution with a concentration of 230 g / L was introduced into a symmetrical membrane for electrolysis. The electrolysis time was 180 min, with a constant current of 3.0 A and a voltage between 5.2 V. The electrode plates were 8.5 cm long, 5.5 cm wide, and had an area of ​​46.75 cm². 2 The brine concentration at the outlet of the tank is 79 g / L, and the demineralized water is recycled. Electrolysis prepares a 20% sodium hydroxide solution; chlorine gas is passed through the sodium hydroxide to obtain a 12% sodium hypochlorite solution.

[0052] Example 2.

[0053] Weigh 20g of waste residue (Al content 13%, P content 8.9%, NaCl content 56.65%), add 25ml of aqueous solution, and place in a three-necked flask. Add 5ml of hydrogen peroxide as an oxidant, then introduce 10 mg / L of ozone. The gas is collected by passing through the first-stage activated carbon bed containing vanadium-loaded catalyst, while simultaneously being rinsed with water. The second stage utilizes porous carbon to adsorb small organic molecules. Both stages of adsorption work together to purify the gas. After heating at 30℃ for 1.5 hours, no odorous gas is released from the three-necked flask.

[0054] The solution was filtered to remove insoluble matter, yielding a supernatant (Al content 14.2%, P content 7.93%, NaCl content 221 g / L). The pH of the solution was adjusted to 6.8 with 0.1 mol / L sodium hydroxide to completely precipitate aluminum ions. Filtration yielded a phosphorus-containing supernatant (P content 9.1%, NaCl content 230 g / L) and aluminum hydroxide precipitate (Al content 96.9%).

[0055] Adding zinc oxide and calcium oxide (molar ratio 1:1) to the filtrate yields a calcium zinc phosphite precipitate. Vacuum drying yields the final product, which is then analyzed by infrared spectroscopy to confirm the calcium zinc phosphite precipitate. Figure 8 As shown.

[0056] The obtained aluminum hydroxide precipitate was first washed with sodium chloride filtrate, then dissolved in 0.5 mol / L hydrochloric acid at pH=3.8. Iron salt and hydrogen peroxide were added for secondary oxidation to convert phosphorus into phosphate. At the same time, the organic matter content was further controlled at 5 ppm. The solution was filtered (P content 28 mg / L). The trace amount of phosphorus in the solution was removed with an adsorbent, and finally polyaluminum ferric chloride (P content 3 mg / L) was obtained.

[0057] The adsorbent packed into the adsorption column is an aluminum-based adsorbent, the basic component of which is aluminum hydroxide (synthesized hydrothermally at 180 degrees Celsius using potassium aluminum sulfate dodecahydrate and urea as raw materials), and the backwash solution is a saturated sodium chloride solution.

[0058] The NaCl filtrate was collected, and organic matter was removed by sodium hypochlorite oxidation. The TOC concentration was 3.1 ppm. The adsorption dephosphorization method was the same as above, followed by deep dechlorination and removal of other calcium and magnesium cations via ion exchange. After purification, a sodium chloride solution with a concentration of 230 g / L was introduced into a symmetrical membrane for electrolysis. The electrolysis time was 130 min, the current was constant at 3.5 A, and the voltage was between 7.0 and 7.2 V. The electrode plates were 8.5 cm long, 5.5 cm wide, and had an area of ​​46.75 cm². 2The concentration of the brine exiting the tank is 76.8 g / L. The concentration of the brine exiting the tank is 67 g / L; the demineralized water is recycled. Electrolysis prepares a 20% sodium hydroxide solution; chlorine gas is passed into the sodium hydroxide solution to obtain a 12% sodium hypochlorite solution.

[0059] Example 3.

[0060] Weigh 20g of waste residue (Al content 11.3%, P content 9.2%, NaCl content 72.54%), add 25ml of aqueous solution, and place in a three-necked flask. Add 5ml of hydrogen peroxide as an oxidant. The gas is collected by passing through the first-stage activated carbon bed containing vanadium-loaded catalyst, while simultaneously being rinsed with water. The second stage utilizes porous carbon to adsorb small organic molecules. Both stages of adsorption work together to purify the gas. After heating at 40℃ for 1 hour, no odorous gas is released from the outlet of the three-necked flask.

[0061] The solution was filtered to remove insoluble matter, yielding a supernatant (Al content 14%, P content 10.65%, NaCl content 210 g / L). The pH of the solution was adjusted to 6.3 with 0.1 mol / L sodium hydroxide to completely precipitate aluminum ions. Filtration yielded a phosphorus-containing supernatant (P content 7.3%, NaCl content 226 g / L) and aluminum hydroxide precipitate (Al content 86.2%).

[0062] Calcium oxide is added to the filtrate to obtain calcium phosphite precipitate, which is then dried under vacuum to obtain the final product. Calcium phosphite is then identified by infrared spectroscopy comparison.

[0063] The obtained aluminum hydroxide precipitate was first washed with sodium chloride filtrate, then dissolved in 0.5 mol / L hydrochloric acid at pH=3.1. Iron salt and hydrogen peroxide were added for secondary oxidation, so that phosphorus was converted into phosphate and the organic matter content was 5 ppm. The solution was filtered (P content 32 mg / L), and the small amount of phosphorus (P content 1 mg / L) in the solution was removed with an adsorbent, finally yielding polyaluminum ferric chloride.

[0064] The adsorbent packed into the adsorption column is an aluminum-based adsorbent, the basic component of which is aluminum hydroxide (synthesized hydrothermally at 180 degrees Celsius using potassium aluminum sulfate dodecahydrate and urea as raw materials), and the backwash solution is a saturated sodium chloride solution.

[0065] The NaCl filtrate was collected, and organic matter was removed by sodium hypochlorite oxidation. The TOC level was 3 ppm. The adsorption dephosphorization method was the same as above, followed by deep dechlorination and removal of other calcium and magnesium cations through ion exchange.

[0066] After purification, a sodium chloride solution with a concentration of 247 g / L was introduced into a symmetrical diaphragm for electrolysis. The electrolysis time was 100 min, the current was constant at 3.7 A, the voltage was between 7.8 and 8.4 V, and the electrode plates were 8.5 cm long, 5.5 cm wide, and had an area of ​​46.75 cm².2 The concentration of the brine discharged from the tank is 79.8 g / L. The demineralized water is recycled. Electrolysis is used to prepare a 20% sodium hydroxide solution; chlorine gas is passed into the sodium hydroxide to obtain a 12% sodium hypochlorite solution.

[0067] Example 4.

[0068] Weigh 20g of waste residue (Al content 12.3%, P content 9.5%, NaCl content 58.63%), add 25ml of aqueous solution, and place in a three-necked flask. Add 5ml of hydrogen peroxide as an oxidant and 8 mg / L ozone. The gas is collected by passing it through the first-stage activated carbon bed containing vanadium-loaded catalyst, while simultaneously being rinsed with water. The second stage utilizes porous carbon to adsorb small organic molecules. Both stages of adsorption work together to purify the gas. After heating at 40℃ for 1 hour, no odorous gas is released from the outlet of the three-necked flask.

[0069] The solution was filtered to remove insoluble matter, yielding a supernatant (Al content 13.4%, P content 11.05%, NaCl content 190 g / L). The pH of the solution was adjusted to 6.4 with 0.1 mol / L sodium hydroxide to completely precipitate aluminum ions. Filtration yielded a phosphorus-containing supernatant (P content 8.6%, NaCl content 212 g / L) and aluminum hydroxide precipitate (Al content 85.4%).

[0070] Calcium oxide is added to the filtrate to obtain calcium phosphite precipitate, which is then dried under vacuum to obtain the final product. Calcium phosphite is then identified by infrared spectroscopy comparison.

[0071] The obtained aluminum hydroxide precipitate was first washed with sodium chloride filtrate, then dissolved in 0.5 mol / L hydrochloric acid at pH=3.1. Iron salt and hydrogen peroxide were added for secondary oxidation, so that phosphorus was converted into phosphate and the organic matter content was 5 ppm. The solution was filtered to obtain a solution (P content 28 mg / L). The small amount of phosphorus (P content 1 mg / L) in the solution was removed with an adsorbent, and finally polyaluminum ferric chloride was obtained.

[0072] The adsorbent packed into the adsorption column is an aluminum-based adsorbent, the basic component of which is aluminum hydroxide (synthesized hydrothermally at 180 degrees Celsius using potassium aluminum sulfate dodecahydrate and urea as raw materials), and the backwash solution is a saturated sodium chloride solution.

[0073] The NaCl filtrate was collected, and organic matter was removed by sodium hypochlorite oxidation. The TOC was measured to be 2.6 ppm. The adsorption dephosphorization method was the same as above, followed by deep dechlorination and removal of other calcium and magnesium cations through ion exchange.

[0074] The NaCl filtrate from the entire process was collected (TOC measured at 2 ppm, NaCl content at 239.2 g / L). The electrolysis time was 90 min, the current was constant at 3.7 A, the voltage was between 8.2 and 8.8 V, and the electrode plates were 8.5 cm long, 5.5 cm wide, and had an area of ​​46.75 cm². 2 The concentration of the brine discharged from the tank was 76.8 g / L. The demineralized water was recycled. Electrolysis was used to prepare a 20% sodium hydroxide solution; chlorine gas was passed into the sodium hydroxide to obtain a 12% sodium hypochlorite solution.

Claims

1. A resource-based treatment process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate, characterized in that, Includes the following steps: Step 1: Dissolve, oxidize, strip, and filter the waste salt with water to remove insoluble matter, odors, and gases for purification; the oxidant oxidizes the entrained organic matter and converts organic phosphorus to phosphorous acid; the solution is neutralized with alkali and then filtered to recover aluminum hydroxide precipitate. Step 2: The precipitated aluminum hydroxide is washed, dissolved, adsorbed, dephosphorized, and oxidized to prepare low-sodium dephosphorized polyaluminum ferric chloride; calcium oxide and / or zinc oxide are added to the dealuminized salt solution to prepare zinc phosphite, calcium phosphite, or calcium zinc phosphite; if calcium oxide and zinc oxide are added, their molar ratio is 1:

1. Step 3: Precipitate the saturated salt solution to remove aluminum and phosphite, and then purify it to prepare alkaline solution and sodium hypochlorite water treatment agent; In step 2, the dissolution and adsorption dephosphorization requires the backwash liquid of the adsorption and dephosphorization column to be returned to the precipitation tank for the preparation of calcium phosphite or calcium zinc phosphite. The backwash liquid is a saturated sodium chloride solution. The precipitate is washed with deionized water until the water conductivity is lower than 30 μs / cm and then dried at low temperature to obtain phosphite. The filtrate for recovering phosphite is required to be saturated sodium chloride. Aluminum-based adsorbents are used for adsorption and phosphorus removal. The adsorption-elution process is the same as above. Sodium hypochlorite is used for oxidation to remove organic matter, and the TOC is reduced to below 5 ppm. Residual chlorine is removed by stripping. Ion activated carbon filtration and cation exchange are used to remove calcium, magnesium and aluminum to meet the standards for entering the tank. The aluminum-based adsorbent is synthesized using aluminum hydroxychloride. During the synthesis process, aluminum chloride and sodium carbonate purified by this process are used to adjust the pH of the system to 2. Citric acid is added and hydrothermal conditions are used to prepare an adsorbent with a crystalline structure and micron-scale.

2. The resource utilization process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate as described in claim 1, characterized in that, In step 1, the oxidant is one or two of ozone, hydrogen peroxide, or sodium hypochlorite.

3. The resource utilization process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate as described in claim 2, characterized in that, When the oxidant is ozone, the outgoing gas undergoes multi-stage purification through adsorption using an activated carbon filter bed. The first stage of the activated carbon bed uses a ternary catalyst supported on vanadium, and is simultaneously rinsed with water. The second stage uses porous carbon to adsorb small organic molecules. Heating increases the dissolution rate but must be controlled below 50°C to reduce water evaporation. The amount of water added is controlled to ensure complete dissolution, but must be controlled to be above 200 g / L based on the sodium chloride content.

4. The resource utilization process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate as described in claim 1, characterized in that, The insoluble matter obtained after oxidation and dissolution in step 1 is mainly impurities such as silicon doped into the raw materials; the solution is neutralized with alkali to a pH of 6-8, and then filtered to recover the aluminum hydroxide precipitate; the final filtrate mainly contains sodium phosphite and a small amount of aluminum, in addition to sodium chloride.

5. The resource utilization process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate as described in claim 1, characterized in that, The aluminum hydroxide precipitated in step 2 contains sodium chloride and aluminum phosphite. Sodium chloride is washed away with deionized water, and the wash water is recycled for dissolution until the conductivity of the aluminum hydroxide wash water is below 30 μS / cm. Solid aluminum hydroxide is dissolved in hydrochloric acid to control the pH to 3-4. Phosphorus removal is then performed using aluminum hydroxide prepared from recycled aluminum chloride solution as the adsorbent, and the phosphorus is reduced to below 10 ppm. Ferrous chloride and hydrogen peroxide are added for heating and oxidation to further remove organic matter and phosphite. The total organic matter (TOC) is controlled at 10 ppm. Aluminum or iron is added as needed to polymerize and prepare polyaluminum ferric chloride.

6. The resource utilization process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate as described in claim 1, characterized in that, The sodium chloride concentration is above 220 g / L, the brine concentration entering the diaphragm outlet is controlled below 80 g / L, the current is constant at 3-3.7 A, the voltage is between 5.0-10 V, the electrolysis time is 1-5 hours, and the electrode plate is 8.5 cm long, 5.5 cm wide, and has an area of ​​46.75 cm². 2 Electrolysis produces a 20% sodium hydroxide solution. Chlorine gas is passed through the sodium hydroxide to produce a 12% sodium hypochlorite solution. The demineralized water is recycled. The sodium chloride concentration of 220 g / L or higher refers to the sodium chloride solution purified from the saturated salt solution used in step 3 to remove aluminum and phosphite, which has a concentration of 220 g / L or higher.

7. The resource utilization process for phosphorus- and aluminum-containing sodium chloride waste salt generated during the preparation of diethyl methylphosphonate as described in claim 6, characterized in that, The electrolytic cell uses a symmetrical ion exchange membrane, which is homogeneous with no front or back sides and is resistant to acids and alkalis.

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