Method for purifying sulfonated aromatic monomer

A method for purifying a sulfonated aromatic monomer represented by formula 1 as shown in the following reaction scheme 2, the method comprising the steps of:

• allowing an aromatic monomer 3 to react with fuming sulfuric acid 4 to prepare a sulfonated aromatic compound 2;
• adding a salt to the compound 2 to precipitate a crude compound 1-1;
• dissolving the crude compound 1-1 in water, wherein the step of dissolving the crude compound is carried out after washing the crude compound with alcohol selected from among methanol, ethanol or a mixture thereof to remove sulfuric acid remaining in the crude compound 1-1;
• neutralizing the aqueous solution containing the crude compound, wherein the step of neutralizing the aqueous solution containing the crude compound is carried out using any one weak base selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, ammonium hydroxide, ammonia, sodium phosphate and sodium sulfate;
• and
• concentrating the neutralized aqueous solution and recrystallizing the concentrate from water, wherein alcohol is not added during the steps of neutralizing and recrystallizing:
• wherein X is a halogen group element, and Y is any one selected from the group consisting of —S—, —C═O—, —P(O)(C6H5)— and —SO2—.