PROCESS FOR PRODUCING HIGH-PURITY TEREPHTHALIC ACID

A process for producing high-purity terephthalic acid in which the p-toluic acid contained in wastewater which has conventionally been discarded is recovered selectively and utilized as a material for terephthalic acid. The process for high-purity terephthalic acid production includes a p-toluic acid recovery step in which p-toluic acid is recovered from a primary mother liquor and supplied to an oxidation reaction step, and is characterized in that the recovery step comprises the following steps: (I) an adsorption step in which the primary mother liquor or a secondary mother liquor obtained by cooling the primary mother liquor and subjecting it to solid-liquid separation is supplied, as a raw liquid to be treated, to an adsorption column packed with an adsorbent in which the breakthrough time for toluic acid is longer than that for benzoic acid to thereby adsorb the p-toluic acid and benzoic acid contained in the raw liquid onto the adsorbent; (II) a supply stopping step in which the supply of the raw liquid to the adsorption column is stopped anytime after the breakthrough time for benzoic acid has passed; (III) a desorption step in which a desorbing agent is supplied to the adsorption column to desorb the p-toluic acid adsorbed; and (IV) a circulation step in which the p-toluic acid contained in the desorbing agent discharged from the adsorption column is supplied to the oxidation reaction step.