Adsorption thermodynamics and kinetic investigation of aromatic amphoteric compounds onto different polymeric adsorbents

The adsorption behavior of p-aminobenzoic acid and o-aminobenzoic acid onto the different polymeric adsorbents was systematically investigated as a function of the solution concentration and temperature. Experimental results indicated that the equilibrium adsorption data of the four polymeric adsorbents fitted well in the Freundlich isotherm. The adsorption capacity of multi-functional polymeric adsorbent NJ-99 was the highest, which might be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of aminobenzoic acid. The adsorption capacity of o-aminobenzoic acid onto any adsorbent was higher than p-aminobenzoic acid. Thermodynamic studies suggested the exothermic, spontaneous physical adsorption process. Adsorption kinetics results showed that the adsorption followed the pseudo-second-order kinetics model and the intraparticle mass transfer process was the rate-controlling step.