PURPOSE: To recover the titled acid from the waste liquor of fiber processing of reduction in weight, by neutralizing previously an alkali metal hydroxide existing in excess in a solution of an alkali metal terephthalate by a desulfurizing device for exhaust gas, precipitating it with an acid, utilizing the excess alkali effectively.
CONSTITUTION: In recovering terephthalic acid from a solution of an alkali metal terephthalate, an alkali metal hydroxide existing in excess in the solution of the alkali metal terephthalate is previously neutralized with a sulfur oxide in a desulfurizing device for exhaust gas, precipitated with an acid, so that terephthalic acid is recovered. In the titration curve of the solution of sodium terephthalate, the white precipitate of terephthalic acid is formed from a pH of 5.8, and the precipitation is finished at a pH of 4.0. A solution of hydrolyzate of polyester fiber can be used as the solution of the alkali metal terephthalate.
YOSHIDA TATSUYA
MATSUMOTO MUNEO
