A method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds.

Abstract

This invention provides a method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds, relating to the field of pharmaceutical process technology. This invention utilizes hydrochloric acid and phosphoric acid produced during the sulfonamide compound production process, as well as sodium carbonate produced by the condensation reaction, for neutralization, reducing the consumption of acid and alkali in the production of sulfonamide compounds and the treatment of phosphorus-containing wastewater. The pH of the condensation aqueous phase is adjusted to 5.5–6.0 to produce sodium dihydrogen phosphate and disodium hydrogen phosphate. Sodium hydroxide is then added to further adjust the pH to 12–13, completely converting sodium dihydrogen phosphate and disodium hydrogen phosphate into trisodium phosphate. Taking advantage of the significant solubility difference between trisodium phosphate and sodium chloride at low temperatures of 0–10°C, trisodium phosphate is separated. Finally, calcium chloride and sodium phosphate form calcium phosphate precipitate, essentially removing phosphate ions from the second mother liquor, thereby achieving full recovery of inorganic salts from the phosphorus-containing wastewater and achieving deep phosphorus removal.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical process technology, specifically to a method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds. Background Technology

[0002] Sulfonamides were the earliest synthetic antibacterial drugs, typically appearing as white or pale yellow crystalline powders. Since their invention and application in the 1930s, sulfonamides have been widely studied and valued as the most promising antibacterial drugs due to their ease of production, storage, efficacy, convenience, and low cost. With over 80 years of history, more than 8,500 sulfonamide drugs have been synthesized, with over 20 commonly used clinically, including sulfadiazine, sulfamethoxypyrimidine, and sulfadiazine. While antibiotics and quinolones have gradually replaced sulfonamides with the discovery and development of various antibiotics, sulfonamides still possess unique advantages such as a broad antibacterial spectrum, stability, ease of use, low cost, and the ability to be mass-produced without consuming grain. Sulfonamides remain an important drug in the treatment of infections in livestock and poultry.

[0003] The production of sulfonamide drugs generates a variety of wastewater, making treatment complex. Phosphorus-containing wastewater is often treated by distillation, but the resulting inorganic salts cannot be recovered, and solid waste treatment is costly. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds. The method provided by this invention obtains trisodium phosphate and calcium phosphate from the phosphorus-containing wastewater generated during the preparation of sulfonamide compounds, resulting in a low phosphorus content in the final mother liquor after treatment.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds, comprising the following steps:

[0007] After removing the solvent from the crude sulfonamide compound solution, water is added, or water is added to the crude sulfonamide compound solution to allow for layering, resulting in a condensed aqueous phase. The pH of the condensed aqueous phase is adjusted to 5.5–6.0, and solid-liquid separation is performed to obtain a first solid component and a first mother liquor. The first solid component is dried to obtain the sulfonamide compound. The crude sulfonamide compound solution is obtained by chlorinating phosphorus oxychloride and a hydroxyl group, acidifying at a pH of 3–3.5, and then condensing with sulfonamide. The acid used to adjust the pH to 5.5–6.0 includes the acid obtained during the acidification process.

[0008] The pH of the first mother liquor was adjusted to 12-13 with sodium hydroxide, and the temperature was lowered to 0-10℃ to induce crystallization. The solid and liquid components were separated to obtain the second solid component and the second mother liquor, respectively. The second solid component was dried to obtain trisodium phosphate.

[0009] The second mother liquor was mixed with calcium chloride to carry out a precipitation reaction, and the solid and liquid were separated to obtain a third solid component and a final mother liquor; the third solid component was dried to obtain calcium phosphate.

[0010] Preferably, before adding water to the crude sulfonamide compound solution, the process further includes: removing the solvent from the crude sulfonamide compound solution;

[0011] The condensed aqueous phase is first decolorized by a first activated carbon, and then the pH value is adjusted to 5.5-6.0;

[0012] The first mother liquor is first decolorized by a second activated carbon and then separated into solid and liquid components. The resulting liquid component is then adjusted to pH 12-13 with sodium hydroxide.

[0013] Preferably, before cooling to 0-10°C, a third activated carbon decolorization process is performed;

[0014] The crystallization time is 1 to 2 hours.

[0015] Preferably, the molar ratio of calcium chloride to trisodium phosphate in the second mother liquor is 1.5 to 1.6:1.

[0016] Preferably, the method for preparing the crude sulfonamide compound liquid includes the following steps:

[0017] Phosphorus oxychloride and hydroxyl compounds are subjected to a chlorination reaction to obtain a chlorinated reaction solution;

[0018] The chlorinated reaction solution obtained from the chlorination reaction is mixed with a water-immiscible solvent and ice water, and the pH value is adjusted to 3-3.5. The mixture is then separated into an organic phase and an acidic aqueous phase. The organic phase is evaporated to dryness to obtain chloride. The acidic aqueous phase is reused in the step of adjusting the pH value to 5.5-6.0.

[0019] The chloride, sulfonamide, organic solvent, and alkaline reagent are mixed and subjected to a condensation reaction to obtain the crude product liquid of the sulfonamide compound.

[0020] Preferably, the hydroxyl group includes maleic hydrazine or 2-hydroxyquinoxaline;

[0021] The molar ratio of the hydroxyl group to phosphorus oxychloride is 1:2 to 2.2;

[0022] The chlorination reaction is carried out at a temperature of 100–105°C for 1.5–2 hours.

[0023] Preferably, the water-immiscible solvent includes one or more of dichloromethane, chloroform, dichloroethane, and toluene;

[0024] The alkali used to adjust the pH value to 3-3.5 includes one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0025] Preferably, the molar ratio of sulfonamide to chloride is 1:0.95 to 1;

[0026] The alkaline reagent includes sodium carbonate and / or sodium bicarbonate; the molar ratio of the sulfonamide to the alkaline reagent is 1:1 to 1.45;

[0027] The organic solvents include o-dichlorobenzene and / or dimethylformamide.

[0028] Preferably, the condensation reaction is carried out at a temperature of 145–170°C for 3.5–4 hours.

[0029] Preferably, the acidic aqueous phase is first decolorized with a fourth activated carbon before use.

[0030] In this invention, phosphorus oxychloride and hydroxyl groups undergo a chlorination reaction, followed by acidification at a pH of 3-3.5 to produce chloride, hydrochloric acid, and phosphoric acid. These then undergo a condensation reaction with sulfonamides to produce sulfonamide compounds and sodium carbonate. This invention utilizes the hydrochloric acid and phosphoric acid (acidic aqueous phase) generated during the sulfonamide compound production process, as well as the sodium carbonate produced during the condensation reaction, for neutralization, thus reducing the production of sulfonamide compounds and the consumption of acid and alkali in the treatment of phosphorus-containing wastewater. The pH of the condensation aqueous phase is adjusted to 5.5-6.0 to produce dihydrogen phosphate. Sodium dihydrogen phosphate and disodium hydrogen phosphate are added, and then sodium hydroxide is added to adjust the pH to 12-13, so that sodium dihydrogen phosphate and disodium hydrogen phosphate are completely converted into trisodium phosphate. Taking advantage of the significant solubility difference between trisodium phosphate and sodium chloride at low temperatures of 0-10℃, trisodium phosphate is separated. Finally, calcium chloride and sodium phosphate form calcium phosphate precipitate, and solid-liquid separation is used to remove most of the phosphate ions from the second mother liquor. Sodium chloride remains in the final mother liquor, thus achieving full recovery of inorganic salts from phosphorus-containing wastewater and achieving deep phosphorus removal. This invention provides a new approach to the treatment of phosphorus-containing wastewater, considering its treatment during the process design stage, and offering a new option for treating phosphorus-containing wastewater from other similar products. It also reduces enterprise production costs, especially waste solids treatment costs.

[0031] Furthermore, this invention uses a water-immiscible solvent and ice water as the hydrolysis system for phosphorus oxychloride, and adjusts the pH to 3-3.5 so that the hydrochloric acid in the phosphorus oxychloride hydrolysate is basically neutralized into sodium chloride, thereby retaining phosphoric acid; at the same time, this pH range also utilizes the water-immiscible solvent to completely extract and separate chloride from water. Detailed Implementation

[0032] This invention provides a method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds, comprising the following steps:

[0033] After removing the solvent from the crude sulfonamide compound solution, water is added, or water is added to the crude sulfonamide compound solution to allow for layering, resulting in a condensed aqueous phase. The pH of the condensed aqueous phase is adjusted to 5.5–6.0, and solid-liquid separation is performed to obtain a first solid component and a first mother liquor. The first solid component is dried to obtain the sulfonamide compound. The crude sulfonamide compound solution is obtained by chlorinating phosphorus oxychloride and a hydroxyl group, acidifying at a pH of 3–3.5, and then condensing with sulfonamide. The acid used to adjust the pH to 5.5–6.0 includes the acid obtained during the acidification process.

[0034] The pH of the first mother liquor was adjusted to 12-13 with sodium hydroxide, and then cooled to 0-10°C to induce crystallization. The solid and liquid components were separated to obtain the second solid component and the second mother liquor, respectively. The second solid component was dried to obtain trisodium phosphate dodecahydrate.

[0035] The second mother liquor was mixed with calcium chloride to carry out a precipitation reaction, and the solid and liquid were separated to obtain a third solid component and a final mother liquor; the third solid component was dried to obtain calcium phosphate.

[0036] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0037] The preparation method of crude sulfonamide compounds will be explained in detail below.

[0038] In this invention, the method for preparing the crude sulfonamide compound liquid preferably includes the following steps:

[0039] Phosphorus oxychloride and hydroxyl compounds are subjected to a chlorination reaction to obtain a chlorinated reaction solution;

[0040] The chlorinated reaction solution obtained from the chlorination reaction is mixed with a water-immiscible solvent and ice water, and the pH value is adjusted to 3-3.5. The mixture is then separated into an organic phase and an acidic aqueous phase. The organic phase is evaporated to dryness to obtain chloride. The acidic aqueous phase is reused in the step of adjusting the pH value to 5.5-6.0.

[0041] The chloride, sulfonamide, organic solvent, and alkaline reagent are mixed and subjected to a condensation reaction to obtain the crude product liquid of the sulfonamide compound.

[0042] This invention involves chlorinating phosphorus oxychloride and a hydroxyl group to obtain a chlorinated reaction solution.

[0043] In this invention, the hydroxyl group preferably includes maleic hydrazine or 2-hydroxyquinoxaline. In this invention, the molar ratio of the hydroxyl group to phosphorus oxychloride is preferably 1:2 to 2.2, and in specific embodiments it can be 1:2, 1:2.05, 1:2.1, 1:2.15, or 1:2.2.

[0044] In this invention, the preferred temperature for the chlorination reaction is 100–105°C, and in specific embodiments, it can be 100°C, 101°C, 102°C, 103°C, 104°C, or 105°C; the preferred reaction time is 1.5–2 hours, and in specific embodiments, it can be 90 minutes, 100 minutes, 110 minutes, or 120 minutes. In this invention, the chlorination reaction solution is not post-treated and is used directly for subsequent reactions.

[0045] After obtaining the chlorination reaction solution, the present invention mixes the chlorination reaction solution obtained by the chlorination reaction with a water-immiscible solvent and ice water, adjusts the pH value to 3-3.5, separates the layers, and obtains an organic phase and an acidic aqueous phase respectively; evaporates the organic phase to dryness to obtain chloride; the acidic aqueous phase is reused in the step of adjusting the pH value to 5.5-6.0.

[0046] In this invention, the water-immiscible solvent preferably includes one or more of dichloromethane, chloroform, dichloroethane, and toluene. In this invention, the mass ratio of the hydroxyl group to the volume of the water-immiscible solvent is preferably 1 g: 4-6 mL, and in specific embodiments, it can be 1 g: 4 mL, 1 g: 4.5 mL, 1 g: 5 mL, 1 g: 5.5 mL, or 1 g: 6 mL. In this invention, the volume ratio of the first organic solvent to ice water is preferably 1: 0.55-0.65, and in specific embodiments, it can be 1: 0.55, 1: 0.6, or 1: 0.65.

[0047] In this invention, the preferred method for mixing the chlorinated reaction solution obtained from the chlorination reaction, the water-immiscible solvent, and ice water is to add the chlorinated reaction solution dropwise into the water-immiscible solvent and ice water. The temperature of the system during the dropwise addition is preferably 15-25°C, and in specific embodiments, it can be 15°C, 20°C, or 25°C.

[0048] In this invention, the alkali used to adjust the pH value to 3-3.5 preferably includes one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate; in specific embodiments, the pH value can be 3, 3.1, 3.2, 3.3, 3.4, or 3.5. In this invention, the alkali is preferably used in the form of an aqueous solution, and the concentration of the aqueous solution is preferably 20-40 wt%, in specific embodiments it can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%. In this invention, the aqueous solution is preferably added dropwise, and the temperature of the system during the dropwise addition is preferably 15-25°C, in specific embodiments it can be 15°C, 20°C, or 25°C.

[0049] This invention uses a water-immiscible solvent and ice water as the hydrolysis system for phosphorus oxychloride, and adjusts the pH to 3-3.5. The byproducts of phosphorus oxychloride produced during the chlorination reaction are hydrolyzed into phosphoric acid. Excess phosphorus oxychloride is hydrolyzed into phosphoric acid and hydrochloric acid. The hydrochloric acid is neutralized into sodium chloride, thereby retaining the phosphoric acid. At the same time, this pH range also allows the water-immiscible solvent to completely extract and separate the chloride from the water.

[0050] In this invention, the chloride includes 3,6-dichloropyridazine or 2-chloroquinoxaline.

[0051] After obtaining the acidic aqueous phase, the present invention preferably further includes: subjecting the acidic aqueous phase to a fourth activated carbon decolorization to obtain decolorized acidic water; and then reusing the decolorized acidic water to adjust the pH value to 5.5-6.0 (i.e., to adjust the pH value of the system after the first activated carbon decolorization). The present invention reuses the acidic aqueous phase in the post-treatment step after the condensation reaction, thus achieving full utilization of the phosphorus-containing waste acid generated during the preparation of sulfonamide compounds.

[0052] In this invention, the decolorization temperature of the fourth activated carbon is preferably 20-30°C, and in specific embodiments, it can be 20°C, 25°C, or 30°C; the decolorization time of the fourth activated carbon is preferably 1-2 hours, and in specific embodiments, it can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, or 120 minutes. In this invention, the preferred mass ratio of the hydroxyl group to the activated carbon is 1:0.02-0.04, and in specific embodiments, it can be 1:0.02, 1:0.03, or 1:0.04.

[0053] After obtaining the chloride, the present invention mixes the chloride, sulfonamide, organic solvent and alkaline reagent, and carries out a condensation reaction to obtain the crude product liquid of the sulfonamide compound.

[0054] In this invention, the molar ratio of sulfonamide to chloride is preferably 1:0.95 to 1, and in specific embodiments it can be 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99 or 1:1.

[0055] In this invention, the alkaline reagent preferably includes sodium carbonate and / or sodium bicarbonate. In this invention, the molar ratio of the sulfonamide to the alkaline reagent is preferably 1:1 to 1.45, and in specific embodiments it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.45.

[0056] In this invention, the organic solvent preferably includes o-dichlorobenzene and / or dimethylformamide (DMF). In this invention, the mass ratio of the chloride to the volume of the organic solvent is preferably 1 g: 4.5–5.5 mL, and in specific embodiments it can be 1 g: 4.5 mL, 1 g: 5 mL, or 1 g: 5.5 mL.

[0057] In this invention, the temperature of the condensation reaction is preferably 145-170°C, and in specific embodiments it can be 145°C, 150°C, 155°C, 160°C, 165°C or 170°C; the time of the condensation reaction is preferably 3.5-4 hours, and in specific embodiments it can be 210 minutes, 220 minutes, 230 minutes or 240 minutes.

[0058] After obtaining the crude sulfonamide compound liquid, the present invention removes the solvent from the crude sulfonamide compound liquid and adds water, or adds water to the crude sulfonamide compound liquid to separate the layers, obtaining a condensed aqueous phase. The pH value of the condensed aqueous phase is adjusted to 5.5-6.0, and solid-liquid separation is performed to obtain a first solid component and a first mother liquor. The first solid component is dried to obtain sulfonamide compounds. The crude sulfonamide compound liquid is obtained by chlorinating phosphorus oxychloride and hydroxyl group, acidifying at pH value of 3-3.5, and then condensing with sulfonamide. The acid used to adjust the pH value to 5.5-6.0 includes the acid obtained by acidification.

[0059] In this invention, the added water is preferably hot water, and the temperature of the hot water is preferably 80-100℃. In specific embodiments, it can be 80℃, 85℃, 90℃, 95℃ or 100℃.

[0060] The present invention does not have any particular limitation on the method for removing the solvent from the crude sulfonamide compound liquid. Any solvent removal method known to those skilled in the art can be used, such as evaporation.

[0061] In this invention, the condensed aqueous phase is preferably decolorized first by activated carbon, and then the pH value is adjusted to 5.5-6.0. In this invention, the decolorization temperature of the first activated carbon is preferably 85-95°C, and in specific embodiments, it can be 85°C, 90°C, or 95°C; the decolorization time of the first activated carbon is preferably 1-2 hours, and in specific embodiments, it can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. In this invention, the preferred mass ratio of chloride to activated carbon is 1:0.02-0.04, and in specific embodiments, it can be 1:0.02, 1:0.03, or 1:0.04.

[0062] In this invention, the pH value is preferably 5.5, 5.6, 5.7, 5.8, 5.9, or 6.0. In this invention, the acid used to adjust the pH value to 5.5–6.0 is preferably the decolorizing acid solution.

[0063] In this invention, the solid-liquid separation is preferably performed while the liquid is hot. This invention does not impose any particular limitation on the solid-liquid separation method; any solid-liquid separation method well-known to those skilled in the art can be used, such as filtration, vacuum filtration, or centrifugation.

[0064] In this invention, the drying temperature is preferably 95-105°C, and in specific embodiments it can be 95°C, 98°C, 100°C, 102°C or 105°C; this invention does not have a special limitation on the drying time, as long as it is dried to constant weight.

[0065] In this invention, phosphorus oxychloride and hydroxyl groups undergo a chlorination reaction, followed by acidification at a pH of 3–3.5 to produce chloride, hydrochloric acid, and phosphoric acid. These then undergo a condensation reaction with sulfonamides to produce sulfonamide compounds and sodium carbonate. This invention utilizes the hydrochloric acid and phosphoric acid (acidic aqueous phase) produced during the production of sulfonamide compounds, as well as the sodium carbonate produced during the condensation reaction, for neutralization, thereby reducing the production of sulfonamide compounds and the consumption of acid and alkali in the treatment of phosphorus-containing wastewater. The pH of the condensation aqueous phase is adjusted to 5.5–6.0 to produce sodium dihydrogen phosphate and disodium hydrogen phosphate.

[0066] After obtaining the first mother liquor, the present invention adjusts the pH value of the first mother liquor to 12-13 with sodium hydroxide, cools it to 0-10°C to crystallize, separates the solid and liquid, and obtains the second solid component and the second mother liquor respectively; the second solid component is dried to obtain trisodium phosphate.

[0067] In this invention, the first mother liquor is first decolorized by a second activated carbon and then subjected to solid-liquid separation. The resulting liquid component is then adjusted to a pH of 12-13 using sodium hydroxide. In this invention, the decolorization temperature of the second activated carbon is 20-30°C, and in specific embodiments, it can be 20°C, 25°C, or 30°C; the decolorization time of the second activated carbon is preferably 1-2 hours, and in specific embodiments, it can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min; the preferred mass ratio of chloride to activated carbon is 1:0.02-0.04, and in specific embodiments, it can be 1:0.02, 1:0.03, or 1:0.04.

[0068] The present invention does not have any particular limitation on the solid-liquid separation, and any solid-liquid separation method known to those skilled in the art can be used, such as filtration, vacuum filtration or centrifugation.

[0069] In this invention, the pH value is preferably 12, 12.2, 12.4, 12.5, 12.6, 12.8, or 13. This invention utilizes sodium hydroxide to adjust the pH value to 12-13, causing sodium dihydrogen phosphate and disodium hydrogen phosphate to be completely converted into trisodium phosphate. The converted trisodium phosphate exists in the form of trisodium phosphate dodecahydrate. The trisodium phosphate dodecahydrate, after drying, yields trisodium phosphate hexahydrate and / or anhydrous trisodium phosphate.

[0070] In this invention, the step of cooling to 0-10°C preferably further includes: subjecting the system after adjusting the pH value to 12-13 to third activated carbon decolorization. In this invention, the temperature for third activated carbon decolorization is 85-95°C, and in specific embodiments, it can be 85°C, 90°C, or 95°C; the decolorization time is preferably 1-2 hours, and in specific embodiments, it can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, or 120 minutes; the preferred mass ratio of chloride to activated carbon is 1:0.02-0.04, and in specific embodiments, it can be 1:0.02, 1:0.03, or 1:0.04.

[0071] In this invention, the temperature after cooling is preferably 0℃, 2℃, 4℃, 5℃, 6℃, 8℃, or 10℃; the crystallization time is preferably 1-2 hours, and in specific embodiments, it can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. This invention utilizes the significant solubility difference between trisodium phosphate and sodium chloride at low temperatures of 0-10℃ to separate trisodium phosphate.

[0072] In this invention, the drying process is preferably carried out by air drying at room temperature.

[0073] After obtaining the second mother liquor, the present invention mixes the second mother liquor with calcium chloride to carry out a precipitation reaction, and separates the solid and liquid components to obtain the third solid component and the final mother liquor; the third solid component is dried to obtain calcium phosphate.

[0074] In this invention, the molar ratio of calcium chloride to trisodium phosphate in the second mother liquor is preferably 1.5–1.6:1, and in specific embodiments it can be 1.51:1, 1.52:1, 1.53:1, 1.54:1, 1.55:1, 1.56:1, 1.57:1, 1.58:1, 1.59:1, or 1.6; the calcium chloride preferably includes calcium chloride dihydrate. By controlling the ratio of trisodium phosphate and calcium chloride in the second mother liquor, this invention enables the trisodium phosphate in the second mother liquor to be converted into calcium phosphate, which can then be removed via solid-liquid separation, thus achieving the purpose of phosphorus removal from wastewater.

[0075] In this invention, the precipitation reaction temperature is preferably room temperature, and the precipitation reaction time is preferably 1 to 1.5 hours, which can be 60 minutes, 70 minutes, 80 minutes or 900 minutes in specific embodiments; the precipitation reaction is preferably carried out under stirring conditions.

[0076] The present invention does not have any particular limitation on the solid-liquid separation, and any solid-liquid separation method known to those skilled in the art can be used, such as filtration, vacuum filtration or centrifugation.

[0077] This invention utilizes calcium chloride and sodium phosphate to form a precipitate of calcium phosphate, and then removes phosphate ions from the second mother liquor through solid-liquid separation. Sodium chloride remains in the final mother liquor, thereby achieving full recovery of inorganic salts in phosphorus-containing wastewater and achieving the goal of deep phosphorus removal from phosphorus-containing wastewater.

[0078] In this invention, the drying temperature is preferably 95-105°C, and in specific embodiments it can be 95°C, 98°C, 100°C, 102°C or 105°C; this invention does not have a special limitation on the drying time, as long as it is dried to constant weight.

[0079] After obtaining the final mother liquor, the present invention preferably further includes concentrating and drying the final mother liquor to obtain sodium chloride. The present invention does not have specific limitations on the concentration and drying processes, as long as the solvent in the final mother liquor can be removed.

[0080] This invention provides a new approach to the treatment of phosphorus-containing wastewater, considering its treatment during the process design stage, and offering a new option for treating phosphorus-containing wastewater from other similar products. It also reduces enterprise production costs, particularly solid waste treatment expenses.

[0081] To further illustrate the present invention, the following detailed description of the treatment method for phosphorus-containing wastewater generated during the preparation of sulfonamide compounds provided by the present invention is provided in conjunction with the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0082] Example 1

[0083] S1 Chlorination reaction: Add 475g of phosphorus oxychloride and 170g of maleic hydrazine to the reaction flask, connect the hydrogen chloride absorption device, turn on the stirrer, heat to 100℃ and keep the temperature for 2 hours, then cool to 20℃ to obtain the chlorination reaction solution.

[0084] S2 hydrolysis reaction: 850 mL of dichloromethane and 510 mL of ice water were added to the reaction flask. Chlorination reaction solution was added dropwise at 15 °C, followed by the addition of 30 wt% sodium hydroxide aqueous solution to adjust the pH to 3. The mixture was allowed to separate into two phases: an organic phase and an acidic aqueous phase. The organic phase was evaporated to dryness to obtain 220 g of 3,6-dichloropyridazine. 5.1 g of activated carbon was added to the acidic aqueous phase, and the mixture was decolorized at 30 °C for 1 h to obtain decolorized acidic water.

[0085] S3 condensation reaction: 1100 mL of o-dichlorobenzene, 220 g of 3,6-dichloropyridazine, 268 g of sulfonamide, and 224 g of sodium carbonate were added to a reaction flask. Stirring was started, and the temperature was raised to 165 °C and kept at that temperature for 3.5 h. 1100 mL of hot water at 80 °C was added, and the mixture was allowed to separate into layers. 6.6 g of activated carbon was added to the resulting aqueous phase, and the mixture was decolorized at 95 °C for 1 h. The solution was then neutralized at 95 °C with the decolorizing acid obtained in S2 to pH 5.5. The solution was filtered while hot to obtain the first solid component and the first mother liquor. The first solid component was dried to obtain sulfachlorpyridazine.

[0086] Add 6.6g of activated carbon to the first mother liquor, decolorize at 20℃ for 2h, filter to remove activated carbon and water-insoluble matter, add sodium hydroxide to adjust pH to 13, add another 6.6g of activated carbon, decolorize at 80℃ for 1h, cool to 0℃ and keep warm for 1h, filter, and obtain the second solid component and the second mother liquor respectively; dry the second solid component at room temperature to obtain 1116g of trisodium dodecahydrate with a purity of 98.8%, which is equivalent to 1103g of trisodium dodecahydrate (theoretical 1178g). It is estimated that the second mother liquor contains about 75g of trisodium dodecahydrate.

[0087] Add 45g of calcium chloride dihydrate to the second mother liquor, stir for 1 hour, filter, and obtain the third solid component and the final mother liquor respectively. Dry the third solid component to obtain calcium phosphate; the phosphorus content of the final mother liquor is <10mg / L.

[0088] Example 2

[0089] S1 Chlorination reaction: Add 420g of phosphorus oxychloride and 200g of 2-hydroxyquinoxaline to the reaction flask, connect the hydrogen chloride absorption device, turn on the stirrer, heat to 105℃ and keep the temperature for 1.5h, recover phosphorus oxychloride under reduced pressure, cool to 30℃, and obtain the chlorination reaction solution.

[0090] S2 hydrolysis reaction: 1000 mL of dichloromethane and 600 mL of ice water were added to the reaction flask. Chlorination reaction solution was added dropwise at 25 °C, followed by the addition of 30 wt% sodium hydroxide aqueous solution to adjust the pH to 3.5. The mixture was allowed to separate into two phases: an organic phase and an acidic aqueous phase. The organic phase was evaporated to dryness to obtain 220 g of 2-chloroquinoxaline. 6 g of activated carbon was added to the acidic aqueous phase, and the mixture was decolorized at 20 °C for 2 h to obtain decolorized acidic water.

[0091] S3 condensation reaction: Add 1100mL of anhydrous DMF, 220g of 2-chloroquinoxaline, 230g of sulfonamide, and 146g of sodium carbonate to a reaction flask, start stirring, heat to 145-150℃ and distill off the aqueous DMF at normal pressure, and keep warm for 4h; add 600mL of hot water at 100℃, separate the layers, add 6.6g of activated carbon to the obtained aqueous phase, decolorize at 85℃ for 2h, neutralize to pH=6.0 with the decolorizing acid water obtained in S2 at 85℃, filter while hot, and obtain the first solid component and the first mother liquor respectively; dry the first solid component to obtain sulfaquinoxaline.

[0092] Add 6.6g of activated carbon to the first mother liquor, decolorize at 30℃ for 1h, filter to remove activated carbon and water-insoluble matter, add sodium hydroxide to adjust pH to 12, add another 6.6g of activated carbon, decolorize at 70℃ for 2h, cool to 10℃ and keep warm for 1h, filter, and obtain the second solid component and the second mother liquor respectively; dry the second solid component at room temperature to obtain 489g of trisodium phosphate dodecahydrate with a purity of 98.2%, which is equivalent to 489g of trisodium phosphate dodecahydrate (theoretical 521g). It is estimated that the second mother liquor contains about 32g of trisodium phosphate dodecahydrate.

[0093] Add 19.5g of calcium chloride dihydrate to the second mother liquor, stir for 1 hour, filter, and obtain the third solid component and the final mother liquor. Dry the third solid component to obtain calcium phosphate; the phosphorus content in the final mother liquor is <10mg / L.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating phosphorus-containing wastewater generated during the preparation of sulfonamide compounds, comprising the following steps: After removing the solvent from the crude sulfonamide compound solution, water is added, or water is added to the crude sulfonamide compound solution to separate the layers, resulting in a condensed aqueous phase. The pH of the condensed aqueous phase is adjusted to 5.5-6.0, and solid-liquid separation is performed to obtain the first solid component and the first mother liquor, respectively. The first solid component is dried to obtain sulfonamide compounds. The preparation method of the crude sulfonamide compound liquid includes the following steps: chlorinating phosphorus oxychloride and a hydroxyl group to obtain a chlorinated reaction solution; mixing the chlorinated reaction solution obtained from the chlorination reaction with a water-immiscible solvent and ice water, adjusting the pH value to 3-3.5, separating the layers to obtain an organic phase and an acidic aqueous phase respectively; evaporating the organic phase to dryness to obtain a chloride; reusing the acidic aqueous phase in the step of adjusting the pH value to 5.5-6.0; mixing the chloride, sulfonamide, organic solvent, and alkaline reagent to carry out a condensation reaction to obtain the crude sulfonamide compound liquid. The pH of the first mother liquor was adjusted to 12-13 with sodium hydroxide, and the temperature was lowered to 0-10℃ to induce crystallization. The solid and liquid components were separated to obtain the second solid component and the second mother liquor, respectively. The second solid component was dried to obtain trisodium phosphate. The second mother liquor was mixed with calcium chloride to carry out a precipitation reaction, and the solid and liquid were separated to obtain a third solid component and a final mother liquor; the third solid component was dried to obtain calcium phosphate.

2. The processing method according to claim 1, characterized in that, The condensed aqueous phase is first decolorized by a first activated carbon, and then the pH value is adjusted to 5.5-6.0; The first mother liquor is first decolorized by a second activated carbon and then separated into solid and liquid components. The resulting liquid component is then adjusted to pH 12-13 with sodium hydroxide.

3. The processing method according to claim 1, characterized in that, Before cooling to 0-10°C, a third activated carbon decolorization process is also performed. The crystallization time is 1 to 2 hours.

4. The processing method according to claim 1, characterized in that, The molar ratio of calcium chloride to trisodium phosphate in the second mother liquor is 1.5 to 1.6:

1.

5. The processing method according to claim 1, characterized in that, The hydroxyl group includes maleic hydrazide or 2-hydroxyquinoxaline; The molar ratio of the hydroxyl group to phosphorus oxychloride is 1:2 to 2.2; The chlorination reaction is carried out at a temperature of 100–105°C for 1.5–2 hours.

6. The processing method according to claim 1, characterized in that, The water-immiscible solvents include one or more of dichloromethane, chloroform, dichloroethane, and toluene; The alkali used to adjust the pH value to 3-3.5 includes one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

7. The processing method according to claim 1, characterized in that, The molar ratio of sulfonamide to chloride is 1:0.95-1; The alkaline reagent includes sodium carbonate and / or sodium bicarbonate; the molar ratio of the sulfonamide to the alkaline reagent is 1:1 to 1.45; The organic solvents include o-dichlorobenzene and / or dimethylformamide.

8. The processing method according to claim 1 or 7, characterized in that, The condensation reaction is carried out at a temperature of 145–170°C for 3.5–4 hours.

9. The processing method according to claim 1, characterized in that, The acidic aqueous phase is first decolorized with a fourth activated carbon before use.