Method for Treating Phosphorus-Containing Wastewater Produced During Preparation of Sulfonamide Compound

A method for treating phosphorus-containing wastewater produced during preparation of a sulfonamide compound, comprising:

• removing a solvent in a crude product solution of the sulfonamide compound and then adding water, or adding the water to the crude product solution of the sulfonamide compound and layering, to obtain a condensed aqueous phase, adjusting a pH of the condensed aqueous phase to 5.5 to 6.0 and conducting a first solid-liquid separation to obtain a first solid component and a first mother liquor, respectively;
• and drying the first solid component to obtain the sulfonamide compound;
• wherein the crude product solution of the sulfonamide compound is prepared by a process comprising:
• subjecting phosphorus oxychloride and a hydroxyl compound to a chlorination reaction to obtain a chlorination reaction solution;
• mixing the chlorination reaction solution obtained after the chlorination reaction, a water-immiscible solvent, and ice water, adjusting a pH of a resulting mixture to 3 to 3.5, and layering to obtain an organic phase and an acidic aqueous phase, respectively;
• evaporating the organic phase to dryness to obtain a chloride;
• and recycling the acidic aqueous phase back to a step of adjusting the pH of the condensed aqueous phase to 5.5 to 6.0;
• and
• mixing the chloride, sulfonamide, an organic solvent, and an alkaline reagent, and conducting a condensation reaction to obtain the crude product solution of the sulfonamide compound,
• adjusting a pH of the first mother liquor to 12 to 13 by using sodium hydroxide, cooling a resulting material to 0° C to 10° C, and conducting crystallization and a second solid-liquid separation in sequence to obtain a second solid component and a second mother liquor, respectively;
• and drying the second solid component to obtain trisodium phosphate;
• and
• mixing the second mother liquor and calcium chloride and conducting a precipitation reaction, and subjecting a resulting reaction material to a third solid-liquid separation to obtain a third solid component and a final mother liquor, respectively;
• and drying the third solid component to obtain calcium phosphate.