In a process for producing aromatic dicarboxylic acids which incorporates the disproportionation of a salt of an aromatic mono- or dicarboxylic acid to produce the unreacted salt of an aromatic mono- or dicarboxylic acid and the salt of the desired aromatic dicarboxylic acid, a method is disclosed for separating the salt of the desired product from the unreacted salt which comprises passing both said unreacted salt and said salt of the desired product in an aqueous solution over an adsorbent comprising an activated carbon. The process is particularly suitable for separating potassium naphthoate from 2,6-K2NDA after potassium naphthoate is disproportionated to produce 2,6-K2NDA and 1- or 2- potassium naphthoate. The adsorbent can be regenerated by the use of a displacing agent and reused without off site regeneration.