On the purification of β-naphthalenesulfonic acid from dilute aqueous solutions containing sulfuric acid

In the development of a biological process for the production of beta-naphthol starting from beta-naphthalenesulfonic acid, the purification of the acid from dilute aqueous solutions containing sulfuric acid is of relevant importance. We investigate the feasibility of carrying out such a purification using the secondary amine Amberlite LA-2 dissolved in toluene. Experimental measurements were performed with aqueous solutions of beta-naphthalenesulfonic acid (NSA) in the concentration range 0.01-0.5 m. The organic phase comprised 0.5 m of Amberlite in the diluent toluene. Experimental results were modeled to determine the Nernst distribution coefficients of NSA and sulfuric acid and the infinite dilution selectivity. The obtained value of this last parameter shows that separation is thermodynamically favored.